NO812106L - ALCOHOL PREPARATION PROCESS. - Google Patents

Description

The present application is a continuation-in-part of US-PS No. 088,196 filed October 23, 1979.

The present invention relates to the production of alcohol. More particularly, it relates to a process for the continuous production of ethanol.

In view of the ever-increasing demand for liquid fuels and the diminishing sources of petroleum - crude oil, researchers have begun to investigate alternative liquid fuels to determine the feasibility of commercial production of such substitutes to satisfy this growing demand. Current widespread conditions, including shortages of petroleum crude oil, sharp increases in the price of oil and gasoline products, as well as the poor political stability in many oil-producing countries, have demonstrated the vulnerability of the current sources of liquid fuels. Even if one could accept such a supply and economic instability, it is clear that the worldwide production of petroleum products in the planned quantities can neither keep pace with the increasing demand nor continue indefinitely. It has become quite clear that the time will soon come when one will get

a transition to sources that are sufficient and preferably renewable.

One of the most widely recognized substitutes that may be made available in significant quantities in the near future is alcohol, and ethanol in particular. See "The Report of the Alcohol Fuels Policy Review" (Dept. and Energy/PE-0012, June 1979). It is e.g. today many companies in the United States and elsewhere in the world sell a mixture of gasoline and from approx. 10 to 20% ethanol (commonly referred to as "gasohol"), which can be used as a fuel in conventional automobile engines. Furthermore, ethanol can be mixed with additives to form a liquid ethanol-based fuel (ie ethanol is the main component) which is suitable for operation in most engine types. Such an ethanol-based fuel is described in US-PS No. 087,618 filed October 23, 1979. The present invention is directed to the problem of how to produce sufficient amounts of ethanol that are necessary for use in such substitute fuels to satisfy the increased demand for liquid fuel.

It is well known that ethanol can be produced by fermentation. Even today, in the majority of the world, ethanol is produced through the fermentation process. In the United States, however, only approx. 25% of the total ethanol production obtained by fermentation, with the remaining part produced synthetically, usually from ethylene.

In the fermentation process, yeast is added to a solution of simple sugars. Yeast is a small microorganism that utilizes the sugar in the solution as food, and this produces ethanol and carbon dioxide as by-products. The carbon dioxide leaves as a gas, as it bubbles up through the liquid and the ethanol remains in solution. Unfortunately, the yeast stagnates when the concentration of the ethanol in solution approaches approx. 18% by volume, regardless of whether fermentable sugars are still present.

For an almost complete fermentation and to produce large quantities of ethanol, it has consequently been common practice to use a batch process whereby very large fermentation containers are used which can contain up to 1,892,700 litres. With such large containers, it is economically unrealistic to provide a quantity of yeast that is sufficient to rapidly ferment the sugar solution. Thus, conventional fermentation processes have required 72 hours and more because such time periods are necessary for the yeast population to build up to the required concentration. For example, a quantity of yeast is added to the fermentation vessel. Within about 45-60 minutes the yeast population will have doubled; within another 45-60 minutes this new yeast population will have doubled. It takes many hours for such propagation to produce the amount of yeast necessary to ferment such a large amount of sugar solution.

Furthermore, the sugars used in such traditional fermentation processes typically contained from approx. 6 to 20% of the larger, complex sugars (such as dextrins and dextrose) which take much longer to undergo fermentation, if they want to be fermented, than is the case for the simple hexose sugars (such as glucose and fructose). Thus, it is common practice to end the fermentation process after a specified period of time, such as 72 hours, even if not all the sugars have been utilized. If one considers the previously known processes from an economic point of view, it is preferred to sacrifice the remaining unfermented sugars instead of waiting for complete fermentation of all the sugars in the batch.

In addition to this, experience has shown that it is preferred to add malt enzymes which help the hydrolysis of starches and conversion of the higher complex dextrin and dextrose sugars which are present in the sugar solutions in the previously known fermentation processes. While such malt enzymes add a desired aroma to ethanol produced for human consumption, the malt enzymes do nothing to make ethanol a more advantageous liquid fuel substitute and may actually create problems for such an application.

One of the most important issues with conventional fermentation systems is the difficulty in maintaining a sterile condition free of bacteria in the large batches and with the long fermentation period. The optimal atmosphere for fermentation is unfortunately also very favorable for bacterial growth. Should such a batch become contaminated, not only must the yeast and sugar solution be discarded, but the entire fermentation vessel must be emptied, cleaned and sterilized. This is both time-consuming and very expensive.

After fermentation, the ethanol has been removed from the fermentation solution using traditional processes and the ethanol product has been further concentrated by distillation. Distillation towers capable of such separation and concentration are well known.

From the foregoing it is clear that the type of sugars used in the fermentation process is important for efficient production and yield of ethanol. It is highly desirable that the sugar used in the fermentation process is preferably simple hexose sugars, so that the fermentation period is minimized and so that as much as possible of the sugar can be utilized in the fermentation process and thereby result in a higher yield of ethanol.

Previously known ethanol fermentation processes have generally been limited to the use of small grains as a source of fermentable sugars. These grains are particularly advantageous because the starch in them is easily hydrolyzed to the sugar. While the majority of the resulting sugars are fermentable, unfortunately typically 6 - 20% of the sugars are slowly fermentable or non-fermentable complex sugars. Obtaining the fermentable sugars from such grain sources is also very expensive. Thus, if large quantities of ethanol are to be produced for use as a liquid fuel substitute at reasonable cost, other sources must be considered for obtaining the fermentable sugars. Although it has been shown under laboratory conditions that such sugars can be obtained from cellulosic materials, the hydrolysis process to release fermentable sugars is known to be very difficult. Researchers have therefore not found an economically acceptable method for producing ethanol from such cellulosic sources.

The present invention is directed to a continuous process for the production of alcohol, preferably ethanol, which is suitable for use as a liquid fuel, from cellulose-containing materials.

The present method preferably begins

with cellulosic materials, including materials that are typically considered waste. The cellulose-containing materials are prepared by division and/or grinding processes which reduce the cellulose-containing material to a powdery supply.

This feed material undergoes a delignification process that separates the three main components of the cellulosic source materials: Cellulose, hemicellulose and lignin. First, the feed is mixed with a dilute acid solution and heated to an elevated temperature at a low pressure for a short period of time. After the acid is neutralized, readily degradable starches and sugars and the hemicellulose remain in solution, while the lignin and cellulose are filterable solids. The hemicellulose solution is ready for hydrolysis to simple sugars.

According to the invention, there are two alternative methods for separating the lignin and the cellulose solids. Using the first method, the lignin and cellulose solids are mixed with a moderate concentration of cadox (a very basic solvent) and then heated to an elevated temperature and at a low pressure for a relatively short period of time. According to the second method, the lignin and cellulose solids are cooled and reacted with a cooled, highly concentrated acid for a relatively short period of time. With either the cadox or acid process, the resulting solution contains the cellulose, while the lignin remains as filterable solids. When the cadoxen process is used, the cellulose is precipitated as soft flakes on cooling and aqueous dilution; when the acid process is used, the cellulose is precipitated as soft flakes by the addition of methanol. The soft fluffy cellulose and the pre-separated hemicellulose solution are combined before hydrolyzing.

In the third alternative and currently preferred method, the lignin and cellulose solids are heated under high pressure in the presence of steam to a temperature in excess of approx. 248.9°C in a short period of time. The solids are then thrown into a flash chamber which is maintained at around atmospheric pressure. The resulting material is combined with the previously separated hemicellulose solution prior to hydrolysis.

The hydrolysis process is carried out in a relatively dilute acidic solution at an elevated temperature under pressure for a short period of time. The solution then obtained is neutralized to a pH value of from approx. 4.5 to 5.0, and the lignin solids are separated. The resulting slurry or "brew" contains essentially only simple hexose sugars as opposed to the larger complex sugars. As the slurry cools to approx. 31.1 - 32.2°C (the preferred fermentation temperature) yeast - nutrients are added. The slurry is then pumped into a continuous fermentation vessel where it can be almost completely fermented in as little as approx. 3-6 hours, which is considerably shorter than the previously known processes which require 72 hours.

The present invention also includes alternative methods for fermenting the slurry into ethanol and then purifying the ethanol. Using the first method, the liquid at the top of the fermentation vessel, which contains a high concentration of ethanol, is allowed to enter another fermentation tank where fermentation continues for a few more hours to convert substantially all of the sugars into ethanol. The resulting solution, called the "wash", is heated to a high temperature and then distilled under low pressure. This high temperature and low pressure distillation results in a high degree of separation of the ethanol in just a single distillation. The resulting ethanol distillate can then undergo a final treatment where it can be dehydrated, denatured, stored and/or mixed with other components of a motor fuel.

Alternatively, carbon dioxide, which is a significant byproduct of the fermentation process, is injected through the slurry into the fermentation vessel. By creating a vacuum at the top of the fermentation vessel, the carbon dioxide will transport the ethanol from the fermentation solution. The ethanol can be easily obtained by cooling the carbon dioxide-ethanol vapor and collecting the ethanol condensate. The ethanol can then be treated.

A further alternative method uses the technique of spraying or passing carbon dioxide to remove ethanol from the fermentation vessel under reduced pressure and then the evaporated ethanol is passed through a distillation tower under reduced pressure so that a legal anhydrous ethanol product is obtained without the use of complicated distillation techniques.

The invention also includes capturing the carbon dioxide released from the fermentation process and utilizing it for the production of other important chemicals such as acetylene, benzene and methanol. The carbon dioxide can also be synthetically converted to produce additional amounts of ethanol.

It is therefore an object of the present invention to provide a continuous process for the production of ethanol in a minimum of time and in high yields.

Another purpose of the invention is to provide an ethanol production process which can utilize many types of cellulose-containing waste in the fermentation process.

A further purpose of the invention is to utilize the carbon dioxide which is developed in the fermentation process in the manufacture of other chemical products.

A further object of the invention is to provide an ethanol product at a reasonable cost.

These and other objects and features of the present invention will appear more clearly from the following description and accompanying claims taken in connection with the accompanying drawings. Figure 1 is a block diagram representing the ethanol production process according to the invention. Figure 2 is a schematic view of an embodiment of the part of the present continuous manufacturing process in which the cellulose-containing material is converted into simple sugars in the preparation for the fermentation process. Figure 3 is a schematic representation of an embodiment of part of the present continuous manufacturing process in which the simple sugars are fermented to ethanol and carbon dioxide and each of these substances is processed into end products. Figure 4 is a schematic representation of an alternative embodiment of the part of the present continuous manufacturing process shown in Figure 3. Figure 5 is a schematic representation of an alternative embodiment of the part of the present continuous manufacturing process shown in Figure 2 in which the cellulose-containing the materials are converted into simple sugars in preparation for the fermentation process. Figure 6 is a schematic representation of an alternative embodiment of the part of the present continuous manufacturing process shown in Figures 3 and 4.

The present invention relates to a method for producing alcohol in a continuous production process which uses cellulose-containing waste materials as starting materials. It has been found that cellulosic materials which are often considered waste can be utilized in the present ethanol production process for the formation of ethanol in a better yield and at significantly reduced costs, compared to the previously known processes. It will be understood that any starchy material (such as barley, corn, rice, wheat and other small grains) in which the starch can be easily converted into simple sugars, as well as any sugary material (such as sugar beet or sugar cane) can be used according to the described method. Nevertheless, it is neither necessary nor economically desirable to limit the use of the present invention to such expensive starchy or sugary materials.

Most cellulosic materials generally contain three main components: Cellulose, hemicellulose and lignin, in the approximate ratios of 4:3:3, respectively. However, these are only approximations; e.g. contains softwood in a typical ratio of 42:25:28, corncobs have the quantity proportions of approx. 40:36:13 with a further 8% simple sugars, while urban waste, on the other hand, contains approx. 75-90% cellulose.

Cellulose is a homogeneous polymer of anhydroglycose units linked together by 1,4-beta-glucosidic bonds, compared to the 1,4 and 1,6-alpha bonds in starch. Hemicellulose is a mixture of simple or mixed polysaccharides, including polymers of pentoses (such as xylose and arabinose), hexoses (such as mannose, galactose and glucose) and saccharic acid. Lignin is a branched polymer macromolecule with three-dimensional randomly bonded polyphenolic units. The general aromatic character of lignin, as well as the general occurrence of covalent carbon bonds, prevents the return to monomers when processing lignin and cellulose from the "woody" fibrous cell walls in plants and is the cementing material between adjacent cell walls.

Although it is relatively easy to hydrolyze hemicellulose to simple sugars, cellulose is highly resistant to hydrolysis because (1) cellulose has a highly ordered crystalline structure and (2) lignin physically surrounds and seals the cellulose. The difficulty in using cellulose in the production of ethanol is the necessity of freeing the cellulose molecules from the lignin seal and the crystalline structure, but once this is done, it is no more difficult to hydrolyze the 1,4-beta-glucosidic bonds in cellulose than the 1,4-alpha-glucosidic bonds in starch.

In view of the fact that almost any cellulosic material can be a starting material in the present invention, many materials which have hitherto been regarded only as waste can be used. Recent statistics demonstrate the abundant availability of such cellulosic waste sources compared to traditional petroleum and ethanol sources:

By utilizing such previously unused cellulosic waste materials as source material for the present method, the possibility of providing very large amounts of ethanol is created without the necessity of significantly increasing the production of expensive starchy grain. Furthermore, unlike petroleum crude oil, most cellulose-containing waste material is annually renewable.

If urban or industrial waste is used as starting materials, it is first necessary to sort the cellulose-containing materials. This can be achieved in any suitable way. For example, Teledyne National Corporation markets a variety of machines that can perform various sorting, shredding, drying and compacting operations that reduce the cellulosic material from the waste materials to a pelletized form. The pelletized cellulosic material can be easily ground to the required size.

With reference to Figures 1 and 2, the cellulosic starting materials 10 are subjected to cutting and grinding operations to reduce the starting materials to a workable size. These operations are generally referred to as grinding process 12. It has been found preferable to grind the raw cellulosic material into a feed of very small size so that the cellulosic material can be easily delignified. It has been found to be best if the feed material has an average particle size of approx. 3.2 mm. The feed material should preferably be small enough so that when diluted it will pass through an approximate 20 mesh sieve. If readily hydrolyzable starchy or sugary materials, such as corn or sugar beet, are used, the average size of the feed materials need not be so small. From an economic point of view, it has been found that painting devices, such as represented by the painter 14 in Figure 2, are more efficient and use less energy than dry painters. The use of hot water (close to the boiling point) has also been found to aid the grinding process.

The resulting feed material 16 is then subjected to a delignification process 20 in which the three main components of the feed (cellulose, hemicellulose and lignin) are separated. In the initial step of the de-lignification process, the hemicellulose is removed together with the easily degradable starches and sugars. The feed material 16 is diluted with water, combined with diluted acid 22 and heated in the boiling vessel 24 at an elevated temperature under low pressure. Although acid 22, which is preferably sulfuric acid, can be added in concentrations above 20% by volume, concentrations in the range of approx. 0.5-2.0% found to be generally satisfactory. Such lower concentrations are actually preferred so that the influence of the hydrogen ion is limited, i.e. the concentration of the hydrogen ion is not high enough to hydrolyze the hemicellulose. Although this step in the delignification process can be carried out over a wide range of temperatures and pressures, it has been found desirable to heat the feed material at a temperature of approx. 93.3-148.9°C at a pressure of approx. 0.35-3.5 kg/cm in approx. 2-10 minutes while stirring. (Unless otherwise stated, all pressure measurements are given in relation to the atmosphere and not in relation to absolute pressure). The preferred conditions are a temperature of approx. 107.2°C at a pressure of approx. 1.05 kg/cm 2 in approx. 3-6 minutes.

In the continuous production process, it is therefore preferred to mix acid 22 with feed 16 and then continuously pump the resulting acidic feed solution into one end of the cooking vessel 24. Agitation is carried out in the vessel 24 and the feed solution is removed from the other end of the vessel after a suitable residence time. It has also been found preferable in such a continuous manufacturing process to use a boiling container which can instantly heat the supply solution to the boiling temperature. This can be easily achieved by using a radiant heater 26 which sprays steam through the feed solution as it enters the boiling vessel. Other types of heating devices (such as heating devices such as

using steam coils) can of course be used.

At this point, the neutralizing agent 28 can be added at 30 to the acidic feed solution as it is removed from the boiling vessel 24 until a pH value of

about. 4.0-6.0 has been achieved. If the acidic feed is neutralized, the preferred neutralizing agents are sodium carbonate or sodium bicarbonate. The separator 32 filters the resulting solution (containing the easily degradable starches, sugars and hemicellulose 34) from the solids (containing the cellulose and lignin). Hemicellulose 34 is then ready for the acid hydrolysis process in the boiling container 68, as discussed below. Hemicellulose 34 can be combined at 62 with the cellulose (after the cellulose is delignified) before hydrolysis or it can be hydrolyzed and then fermented separately. Since the hemicellulose-containing solution is to be acidified again during the subsequent hydrolysis step and since neutralization is usually not necessary for the hemicellulose to dissolve in solution, it has been found that the neutralization step can usually be omitted.

The solids separated from the hemicellulose solution are then processed to separate the lignin from the cellulose. This can be achieved by alternative methods. According to the first method, which is represented in Figure 2, the solids are diluted with water and mixed at 36 with a cadoxene solvent 38 (ethylenediamine cation in an aqueous concentration of about 25% by volume) to an amount of about 10-20 volume percent water. The resulting solution is pumped into the boiling container 40, which is preferably constructed so that the solution entering the container is instantly heated by the radiant heater 42. The solution in the boiling container 40 is heated to a pre-elevated temperature of approx. 65.6-115.6°C and a pressure from approx. atmospheric pressure to approx. 1.05 kg/cm for approx. 2-10 minutes while stirring. Such conditions have been found to be sufficient to break up the lignin seal surrounding the cellulose and break down the highly ordered cellulose structure so that the cellulose will dissolve into solution. It will be understood that a longer residence time or a higher temperature and pressure may be necessary depending on the particular cellulose starting material used, how easily the cellulose is bound to the lignin, or the size to which the cellulose starting materials were ground. The preferred conditions are at a temperature of approx. 93.3°C at atmospheric pressure for approx. 3-6 minutes.

The undissolved solids substantially containing lignin 44 can be filtered from the cellulose-containing solution at the separator 46. These lignin solids 44 can be dried, e.g. with a vacuum dryer 48, and then used as a fuel for the heating system 50 which supplies heat to the entire manufacturing operation. Recycling of the by-products, such as use of the lignin, can be a significant factor in the economic feasibility of the ethanol production process according to the invention.

It will be understood that the lignin does not need to be separated from the cellulose solution at this point in the process because the lignin is not subjected to degradation in the subsequent hydrolysis process. For example, in a given particular process plant it may be easier to achieve this lignin separation after hydrolyzing the cellulose; such filtration can easily be achieved after the mixture is cooled in the cooler 86. At this point in the process, the mixture would not be strongly acidic or strongly basic. The presence of the strong acids or bases used in the delignification process can cause maintenance problems in the separator 46.

The cellulose-containing cadox solution is then cooled in the cooling vessel 54 and diluted with water. As the solution 52 cools, the cellulose precipitates as soft flakes which can be filtered from the cadoxene solvent with the separator 56. The cadoxene solvent 38 can then be recycled as indicated in Figure 2. This soft fluff-like cellulose 58 must be rapidly subjected to acid hydrolysis, otherwise the soft fluff-like material will harden and become resistant to acid hydrolysis. The fact that it is necessary to quickly hydrolyze the soft fluff-like material immediately after it is formed is a significant reason why the person skilled in the prior art has not been able to use cellulose-containing starting materials in the previously known batch processes .

As an alternative to the cadoxene treatment for delignification of the cellulose, concentrated sulfuric acid can be used. With such a treatment process, sulfuric acid in concentrations of approx. 60-90% by weight and preferably approx. 72-75%, added to the lignin and cellulose solids that are filtered from the hemicellulose solution in the separator 32. Other acids can be used. One has e.g. found that hydrochloric acid in concentrations from approx. 30 to approx. 60%, preferably approx. 40%, is effective in delignifying the cellulosic material.

The solids and the concentrated acid can be boiled at a temperature of approx. 65.6-115.6°C for 2-10 minutes (preferably at a temperature of about 93.3°C for about 3-6 minutes). When the resulting solution is cooled and diluted with methanol, the cellulose will precipitate as a soft fluffy material.

It has unfortunately been found that when the lignin and cellulose solids are heated above room temperature in concentrated sulfuric acid, the resulting material is often a black tar-like substance. The presence of this tar-like substance greatly complicates the re-precipitation of the cellulose fluff material prior to the hydrolysis process. When the lignin and cellulose solids are reacted with the concentrated sulfuric acid at a temperature of approx. 15.6-23.9°C, the result is a gray colloidal solution in which some of the cellulose has been charred and some of the sugars have undergone decomposition. The colloidal material also complicates the reprecipitation of the cellulose fluff material.

It has been discovered that significant charring of the cellulose and breakdown of the sugars can be avoided by cooling the concentrated sulfuric acid and the cellulose and lignin solids to a temperature from approx. -1.1 to 15.6°C (the preferred temperature is about 4.4-10°C) and then allow the reaction to proceed with vigorous stirring for about 1-10 minutes. The high acid concentration at such cool temperatures can still break down lignin and. the cellulose structure and dissolve the cellulose. In addition to this, the cool temperatures will delay the breakdown of the cellulose by minimizing the formation of hydrogen ions that would begin to hydrolyze the cellulose into non-fermentable cellibose. Under these temperature conditions, most of the cellulose will dissolve in the concentrated acid. The resulting acid solution, when diluted with methanol, will give a soft fluff-like precipitate of cellulose 58. Using this delignification method, the boiling vessel 40 (shown in figure 2) would be replaced with a boiling vessel in which the temperature of the reactants could be lowered to the desired temperature. This cellulose precipitate 58 can be separated and hydrolyzed as if the cadoxene treatment was used. The acid and methanol are of course preferably recycled.

In preparation for the acid hydrolysis process, the cellulose 58 (in the form of a soft fluffy material) is diluted with water for easier handling and mixed at 62 with hemicellulose 34. This slurry is then mixed with acid 64, preferably sulfuric acid, to achieve a concentration calculated on water volume, of approx. 0.5-10%. It has been found that this mixing is best achieved in a continuous mixing tank 66 for the slurry, so that a complete mixing of the components is obtained. The slurry is heated in the boiling container 68, preferably instantaneously by means of the radiant heating device 70, to a temperature of approx. 93.3-204 .4°C at a pressure of approx. 1.05-14 kg/cm<2>in approx. 2-10 minutes. It will be understood that the temperature, pressure and residence time are interdependent so that any of them can be modified to adapt the acid hydrolysis process to the continuous manufacturing process. For example, if easily hydrolyzable starches are used, a temperature of approx. 93.3°C at 1.05 kg/cm2 be sufficient.

If more hydrolysis-resistant materials are used,

however, it may be necessary to raise the temperature above 204.4°C or more by increasing the pressure sufficiently to prevent the water from changing to steam. Nevertheless, the preferred hydrolysis conditions which are sufficient for most materials are a temperature of approx. 182.2°C at a pressure of approx. 10.5 kg/cm 2 in a residence time of approx. 3-6 minutes.

The hydrolyzed slurry is neutralized by

74 to a preferred pH value of approx. 4.5-5.0; preferred neutralizing agents 72 are sodium carbonate and sodium bicarbonate. This slightly acidic slurry is termed "wort", represented as 76 in Figure 1, although it is usually termed "porridge". The slurry must be cooled to the fermentation temperature, which is preferably in the range 31.1-32.2°C. According to the present continuous manufacturing process, it is advantageous to cool the slurry in a series of cooling processes 78 in order to thereby minimize the amount of energy required.

By e.g. feeding the slurry into a flash cooler 80, the temperature can be instantly lowered to approx. 126.7-104.4°C. It is then preferred to add yeast nutrients 82 to the slurry because at this temperature they are automatically sterilized and are completely mixed with the slurry. Heating the yeast nutrients and the slurry to a temperature in excess of 93.3°C results in a significant advance compared to the known technique by preventing bacterial contamination in the fermentation containers. The slurry may then be pumped into a vacuum flash cooler 84, preferably a barometric condenser and ejector, where it is further cooled to a temperature of about 71.1-48.9°C. The slurry is then pumped through the cooler 86 where cooling water is added to bring the solution down to the fermentation temperature and the pH value is adjusted to approx. 4.5-5.0. At this point the slurry is ready for the fermentation process 90.

It will be understood that the processes described for delignification and hydrolysis of the cellulosic materials described above are relatively severe because a strong acid or base is required to separate the lignin and cellulose. These delignification processes also require expensive equipment to reduce1 the acid, base and methanol reagents. Such recycling equipment can amount to over 40% of the total equipment costs for the alcohol production process; furthermore, operation of this recycling equipment can utilize up to 60% of the energy requirements for the total manufacturing process.

An alternative to the above-described delignification processes which avoids the use of acids or bases has been discovered. It has been found that when cellulosic materials are heated under pressure in the presence of steam to a temperature of approx. 204.4°C, the cellulose cells begin to soften, and that when such materials are heated to approx. 248.9°C the cellulose becomes practically amorphous. At temperatures of approx. 248.9°C and the correspondingly high pressure, the cellulosic cells will absorb water from the flow into the spaces between the cells and through the cell walls (due to pressure) into the cell. The result is that the cells become hydrated. By suddenly exposing these hydrated cellulosic cells to atmospheric pressure, the water in and between the cells will expand explosively and thereby destroy the cellulosic crystalline structure and break the lignin seal. The effect of the expanding water vapor when exposed to atmospheric pressure, which can be compared to "popcorn popping", is rapid exposure of the cellulose cell structure so that the cellulose can be easily hydrolyzed by acid in the subsequent hydrolysis process.

According to this method, which is illustrated in figure 5, the lignin and cellulose solids (from the separator 32) are pumped into the cellulose digester 240 which is maintained at a steam pressure of between approx. 42 and approx. 105 kg/cm o (which, according to conventional steam tables, gives temperatures from about 248.9 to about 315.6°C) for about 3-30 minutes. The preferred conditions are approx. 49 kg/cm<2> (equivalent to approx. 260°C) for approx. 10-15 minutes. Press approx. 42-49 kg/cm 2 is necessary for the cells to become sufficiently hydrated to undergo the aforementioned "popcorn popping" effect when the hydrated cells are exposed to atmospheric pressure. In addition to this, it is desirable to minimize the temperature to which the cellulose-containing materials are exposed because too high a temperature can char or scorch the cellulose. It will therefore be understood that the effective use of the 'popcorn-smashing' method is limited to relatively narrow pressure and temperature ranges. The time required to hydrate the cellulosic cells will naturally vary depending on the type of feed material used. in addition to this, surfactants, such as "4X fire water", can be used to reduce the surface tension of the water molecule coolers and thereby allow for a more rapid hydration of the cellulose materials and a corresponding reduction of the residence time.

The hydrated materials are then flung into the flash chamber 242 which is maintained at near atmospheric pressure. The sudden transfer of the hydrated cellulosic materials from a pressure of approx. 42-105 kg/cm 2 to atmospheric pressure, results in uprooting of the lignin and exposure of the cellulose-containing cells. Unlike the delignification processes that use strong acid or booths (discussed above) in which the cellulose dissolves, the "popcorn popping" process separates the lignin and cellulose, but only exposes the cellulose so that it can be easily hydrolyzed.

In preparation for hydrolysis, the resulting slurry (as it leaves flash chamber 242) is combined at 244 with hemicellulose 34. This slurry is then mixed with acid 246, preferably sulfuric acid, to a concentration of about 0.5 to approx. 10% in a continuous mixing tank 248y preferably approx. 0.5%. The slurry is hydrolyzed in the boiling vessel 250 under the same conditions as discussed above with respect to the hydrolysis in the boiling vessel 68 in Figure 2. The cellulose is easily hydrolyzed under such conditions while the lignin remains unaffected by the acid at the

specified pressures and temperatures.

The hydrolyzed slurry is cooled by discharge into the flash cooler 252. The slurry is then neutralized at 254 with the neutralizing agent 256. At this point in the process the sugars are in solution while the lignin, any undissolved cellulose and other non-hydrolysable components of the feed material (such as plastic or other complex molecules that may be present in feed materials such as garbage) are solids. These solids can be easily separated at 258, dried, then utilized as previously described. Although any conventional separation technique may be used, a convenient method of separating the solids from the fermentable sugars (or "wort") is the use of a vacuum filter belt which draws the solution from the solids using a vacuum. An early advantage of a vacuum filter belt is that it simultaneously sufficiently cools the solution before fermentation without the use of coolers 84 and 86 (shown in figure 2). After yeast nutrients 260 have been added to the sugary solution (ie "wort") and any minor changes in the temperature or pH of the solution have been made, the solution is ready for fermentation.

It is particularly noteworthy that the slurry ("wort") produced from the cellulosic materials according to the present methods contains a very large proportion of simple sugars which are easily fermentable. Thus, almost all the sugars are converted in the fermentation process. Furthermore, unlike previously known processes, there is no need to add malt enzymes to the slurry to convert the dextrins into fermentable sugars.

The present invention includes three alternative methods whereby the sugars in the slurry are fermented to alcohol and the alcohol is purified. These alternative methods are illustrated in figures 3, 4 and 6 and are discussed separately in the following. According to the first method shown in figure 3, the slurry ("wort") (which has been cooled to about 31.1-32.2°C, which has had its pH adjusted to about 4.5-5, 0

and which has been diluted with water to a concentration of approx. 15-25 weight percent sugar), pumped into the primary fermentation container 92 where it has a residence time of approx. 6-11 hours, but preferably approx. 8 hours. The container 92 is provided with an agitator 94 which is preferably provided with devices which can keep the solution in the slurry in the preferred temperature range for fermentation. Since the fermentation process is exothermic, means must be provided for cooling the solution as needed; if the environment outside the container 92 is cold, means must also be provided for heating the solution to maintain the fermentation temperature.

Periodically (such as at the beginning of each start-up cycle) sufficient yeast (preferably brewer's yeast) is added, usually represented as 88 in Figure

1, to the primary fermentation vessel to bring the yeast cell count up to a concentration of approx. 100 million cells per ml within 4 hours. It has been found that under the conditions of the present invention yeast multiply continuously during fermentation at a rate sufficient to maintain this optimum population.

As the slurry undergoes fermentation, ethanol and carbon dioxide are produced in relative percentages of approx. 51% to 49%, respectively. In contrast to the previously known batch system where the carbon dioxide is allowed to escape into the atmosphere or is only collected for sale as a by-product, it has been found advantageous to utilize this produced carbon dioxide, represented as 96, for conversion into other usable products, as discussed below.

The primary fermentation vessel 92 preferably has a constant level overflow to a secondary fermentation vessel 98 for a further fermentation residence time of approx. 2-5 hours, preferably approx. 3 hours. Although it is covered by the present invention only to have a fermenter

ing container where the residence time is set. Correspondingly,

it has been found advantageous to use such a secondary fermentation vessel because this helps to achieve almost complete fermentation of the sugars in the slurry. Such an arrangement also allows any slower fermenting sugars to remain in the fermenter for a longer period of time to complete the fermentation process. This is achieved because the specific gravity of ethanol (about 1.0) is less than that of the slurry (about 1.16 depending on the sugar content); the ethanol thus tends to rise to the top and move faster to the subsequent process steps. The secondary fermentation vessel 98 is also provided with agitators and devices 99 for maintaining the correct fermentation temperature. Consequently, the total fermentation time is approximately 8-15 hours, preferably approx. 11 hours.

From the secondary fermentation vessel, the ethanol-containing "wash" is pumped to the distillation system, generally represented as 100, where it is heated in the heating device 102 located at the bottom of the distillation tower 104. By using the heated vapors from the distillation tower, the heating device 102 can be economically raise the temperature of the "wash" material to be distilled.

One of the unique features of the present invention is the high-temperature-low-temperature operation of the distillation tower. By placing the vacuum pump 106 at the top of the distillation tower 104, the pressure in the tower is reduced. Although vacuum distillation has been used in the synthetic vitamin industry, such use has taken place at very low temperatures to protect the vitamins from degradation. In the present method, however, it is desirable to heat the ethanol-containing "wash" to as hot as possible, preferably in the range of approx. 32.2-82.2°C, so that it will quickly evaporate in the distillation tower. It will be understood that the temperature of the ethanol-containing "wash" will be above the boiling point of ethanol at the pressures in the distillation tower, which pressures are kept as low as possible, preferably at approx. 0.14-0.7 kg/cm 2. This hybrid system with high temperature and low pressure allows for greater separation of the ethanol than conventional distillation towers or low-temperature vacuum distillation towers.

The efficiency of any distillation tower is determined by its ability to rapidly exchange the components between the liquid and vapor pools, which is a function of the vapor-liquid interface area and the flow characteristics of the vapor. The high-temperature and low-pressure system increases the velocity of the steam moving upwards and thus increases the interfacial transfer between liquid and steam and results in an increased splitting effect in the distillation tower. As part of the vapor condenses and falls down through the tower, the collision force thus becomes much greater than in conventional towers. At the same time, the vacuum changes the total pressure and thereby makes the separation easier because the relative volatility of the components in the solution changes. Naturally, one must ensure that the upward forces of the vacuum are not so great that a lift is created

the liquid droplets which are greater than the gravitational forces of the droplets.

Although it will be understood that a number of different conventional distillation towers will be sufficient according to the present invention, for illustrative purposes, one embodiment shall be mentioned. The ethanol-containing "wash" material is pumped into the bottom of a distillation tower having a diameter of 0.91 m and a height of 14.6 m in which the lower part serves as a splitting section with perforated plates around it and the upper section as a rectification column with approximately 26 bubble plates. Due to the reduced pressure under which the distillation is achieved, it is preferred to have a large cross-sectional area so that the steam's upward movement is not hindered by the steam's expansion which is caused

of the reduced pressure. Otherwise, the capacity of the distillation tower is greatly reduced. Steam is flushed into the incoming "wash" at approx. 0.21 kg/cm 2 and thus heats the solution

to its boiling point. Consequently, the ethanol is immediately vaporized as it enters the distillation tower.

The vacuum pump 106 reduces the pressure at the top of the distillation tower by preferably 1.4-2.1 kg/cm . This results in a vapor rich in ethanol that rapidly rises through the tower. As the vapor is drawn up the tower, it encounters droplets of water and ethanol that have condensed, and this results in a splitting action whereby the water is generally returned to the bottom of the distillation tower and the ethanol is generally drawn to the outlet opening at the top of the tower. When the steam is present at the top of the tower, it can easily condense on cooling at 108.

Part of the distillate 110 is preferably returned to the tower as reflux to increase the splitting effect and to regulate the degree of strength of the distillate. The remainder of the ethanol distillate is sent to final treatment 112. By regulating the amount of distillate returned to the tower, the concentration of the resulting ethanol product can be regulated. For example, by allowing a larger portion of the distillate to return to the tower, the reflux effect is increased so that the distillate achieves a higher ethanol concentration. Concentrations of around 95% (190 strength) ethanol can be achieved. Should there only be a need for concentrations of 140 or 150 strength, such as in a blended ethanol-based fuel, a smaller amount of the distillate is returned to the tower.

The undistilled components or residues in the "wash" material that remain at the bottom of the distillation tower can be continuously removed and dried, such as in the vacuum dryer 114. When the cellulosic starting materials are forest products or other crop materials, the dried residue can be used as a supplement for animal feed or as a fertiliser. When the cellulose-containing starting materials are urban or industrial waste, the dried residue can be used as fuel for heating systems or as fertiliser.

The second method according to the invention, whereby the sugars are fermented to alcohol and the alcohol is purified, eliminates the need for conventional distillation equipment. It will be understood that the elimination of the conventional distillation tower in the ethanol manufacturing process is significant since the tower can represent a significant percentage of the total capital investment required to build such an ethanol manufacturing facility and has one of the highest energy consumption of all components in the manufacturing process . This alternative embodiment of the fermentation process, generally represented as 190 (in Figure 1), is schematically shown in Figure 4. The slurry ("wort") is pumped into the fermentation vessel 192 under the same temperature conditions as discussed above. The main difference is that part of the carbon dioxide that is formed during the fermentation process is recycled to the bottom of the fermentation vessel and passed through the slurry in the fermentation vessel.

(Other gases which do not inhibit the fermentation process can of course be used). This passage under pressure of finely divided carbon dioxide through the jet nozzle 194 into the fermentation container will transport a mixture of ethanol and water from the fermented solution in vapor form. The preferred rate of carbon dioxide flow has been found to be approx. 0.075-3.74 dm 3 per liter of solution in the fermentation vessel. By placing the fermentation vessel under a slightly reduced pressure (lowering the pressure by up to 0.35 kg/cm ), such as with the vacuum pump 196, the carbon dioxide will carry a richer ethanol mixture out of the vessel where it can be condensed and removed from the carbon dioxide in the condenser 198. The ethanol which has a degree of strength of approx. 190 can then be taken to final treatment without the need for any further distillation.

It will be understood that the flushed carbon dioxide will use the collision with the fermentation solution (similar to the plate in the distillation tower) to remove the ethanol for which the carbon dioxide has an affinity. It is preferred that the jet of carbon dioxide is finely divided and sprayed out so that it is brought into contact with almost the entire slurry in the fermentation vessel. This can be achieved by using a suitable spray head, preferably a carbon or aloxite spray head. Although it is preferred to have a temperature control device 200 to maintain the temperature of the fermentation solution, it is not necessary to also have an agitator because the introduced carbon dioxide will ensure sufficient agitation.

The non-ethanol containing portions of the fermented solution including the dead yeast cells are gradually removed from the fermentation vessel through overflow 212 at the top of the fermentation vessel 192, dried (such as in a vacuum dryer 214) and used as a supplement to animal feed, as a fuel or as a fertilizer .

The ethanol, whether condensed as it leaves the distillation tower 104 (Figure 3) or as it leaves the fermenter 192 (Figure 4), is taken to final treatment 112 where it can be dehydrated at 116 by benzene distillation or salt dehydration, where it can be denatured with methanol 120 or other approved means according to the current regulations, and/or where it can be stored. The ethanol can also be mixed at 117 with other components, generally represented as 118, to form an ethanol-based fuel, as described in US-PS No. 087,618 filed October 23, 1979.

The third method according to the invention, whereby the sugars are fermented to alcohol and the alcohol is purified, is aimed at removing the ethanol from the slurry and distilling it to legal anhydrous purity. As shown in Figure 6, the slurry is pumped into the primary fermentation vessel 262 where it has a residence time of between approx.

3 and 6 hours, but preferably approx. 4 hours. Although the residence time is very short compared to previously known methods (and the other methods according to the invention), most of the sugars will be completely fermented during this time period because under the conditions stated below it is possible to maintain a population of up to 500 million yeast cells per ml. The importance of this advance in the technique is clear in light of the fact that previously known processes typically only give access to a population of at most approx. 70-100 million yeast cells per ml.

One of the reasons why such a high population of yeast cells can be maintained is that the ethanol produced by fermentation is continuously removed from the fermentation container 262. There is thus no ethanol inhibition of the fermentation process. The ethanol is removed from the fermentation vessel by continuously providing a vacuum of approx. 50.8-66 cm of mercury, preferably approx. 63.5 cm. Also, carbon dioxide is flushed at 262 through the fermenting slurry to help transport the ethanol away from the fermenting slurry. (Small amounts of oxygen are also flushed through the fermenting slurry to help maintain the yeast population). By minimizing the ethanol concentration in container 262 it has been found

that sugar solutions even as high as 40 and 50% can be used in the fermentation process, compared to previously known processes which are generally limited to sugar solutions of less than 10-20%.

It will be understood that it may be necessary to add heat to the primary fermentation vessel because the constant evaporation of ethanol from the slurry would otherwise quickly cause the temperature to drop below the preferred fermentation temperature. As indicated, most of the sugars are fermented while the slurry is in the primary fermentation vessel 262. Nevertheless, there is a constant overflow into the secondary fermentation vessel 266 where the final amounts of sugar are fermented and the ethanol is removed under vacuum. The secondary fermentation vessel also serves as a recirculation station because the dead yeast cells (floating) tend to migrate to the top of the vessel where they eventually overflow into the sedimentation tank 268. The live yeast cells become dormant with the diminishing nutrient supply and sink to the bottom of the vessel 266 where they are recycled at 270 to the primary fermentation vessel 262. By returning the unused yeast cells to the primary fermentation vessel, the highest yeast cell concentration is maintained therein without the continuous addition of significant amounts of yeast. The solids collected in the sedimentation tank 268 are separated by means of a screw press 272 and dried. These solids make an excellent supplement to animal feed because they consist of proteins, heavy sugars and other organic compounds.

As shown in Figure 6, the ethanol vapor from the fermentation containers 262 and 264 is fed directly into the distillation tower 274 in a vapor state. Experiments have shown that the ethanol (which is still in a vaporized state) is in a minimum concentration of approx. 15-20% when it enters the distillation tower. This is significant compared to typical distillation towers where the ethanol only comprises approx.

4-10% of the liquid solution entering the tower and where the ethanol must be evaporated from a liquid solution once it has entered the distillation tower. Due to the fact that the ethanol concentration is much greater (in the present

invention) as it enters the distillation tower, less separation will be necessary for the tower part.

The vacuum pump 280 provides a vacuum in the distillation tower of approx. 50.8-66 cm of mercury, preferably approx. 63.5 cm mercury. This greatly reduced pressure allows for a much greater separation of the ethanol. The reduced pressure also reduces the ethanol and water azeotrope material so that the resulting product is approx. 99.6% ethanol (compared to being able to obtain 95% ethanol at atmospheric pressure) with only one pass through the distillation tower The resulting ethanol thus satisfies the law's requirement of 99.3% for anhydrous ethanol without the need for expensive benzene distillation methods or the like. It has been found that when the ethanol enters the distillation tower in a vapor state and at a reduced pressure of approx. 6 3.5 cm of mercury, the temperature at the bottom of the tower is approx. 4 3.3°C and the temperature halfway up the distillation tower approx. 32.2°C.

The ethanol exiting the distillation tower 274 is liquefied in the condenser 276. Some of the ethanol is passed through the reflux drum 284 and then recycled back to the distillation tower at 278 to increase the efficiency of the tower. The carbon dioxide that is separated from the ethanol by the reflux drainage contains a small percentage of ethanol. It is therefore preferred to pass this steam through the washer 282 so that this ethanol can finally be collected.

A significant feature of the present invention is that a simple vacuum source 280 is used to remove the ethanol from the slurry in the fermentation tanks 262 and 266 and to distill the ethanol in the tower 274. This design allows maintaining a lower ethanol concentration in the fermentation vessels while the concentration of the evaporated ethanol as enters the distillation tower is kept relatively high, and thus the extent of separation that must be achieved by the distillation tower is minimized.

It will be seen that the condenser 276 is placed in the vacuum line between the distillation tower 274 and the vacuum pump 280. With this location it is much easier to maintain the necessary vacuum because as the ethanol condenses at 276, the vacuum load on the distillation tower increases. If it weren't for the fact that the vacuum was used to remove the ethanol from the fermentation tanks, it would be necessary to introduce a gas into the distillation tower to prevent the tower from collapsing. However, due to the coordinated arrangement of the vacuum system (including the vacuum pump and condenser) with both the distillation tower and the fermentation tanks, power requirements are greatly reduced.

One of the important features of the present invention is its versatility when it comes to using a number of different starting materials. Accordingly, as the available starting materials vary over time or as several different types of starting materials become available, no significant modification of the present method needs to be made. If e.g. a source of cooked cellulose was available at a given time, it could simply be added to the process prior to the cadox or concentrated acid step of the delignification process, such as through valves 140 as shown in Figure 2. If a source of starch materials were available, the materials could be added just before the acid hydrolysis, such as through valve 142. If starting materials containing simple sugars were readily available, they could be added to the continuous process at a point just before the fermentation process, such as through valve 144, which would expose the materials to a temperature which was high enough to sterilize them.

Another feature of the invention is to use all the by-products. Methanol 120 for denaturation and the main components of a blended ethanol-based fuel, benzene 122 and acetylene 124, can therefore be synthetically produced in the carbon dioxide conversion unit 126 from the excess carbon dioxide produced as a by-product in the fermentation process. Further amounts of ethanol can also be synthetically produced from the excess carbon dioxide. The process for producing this synthetic ethanol 130 utilizes the hitherto discarded carbon dioxide by-product from the fermentation process for a dramatic increase in the yield of ethanol. Without increasing the amount of cellulosic starting materials or the size or number of the process vessels or distillation towers, it is actually possible to almost double ethanol production.

The following processes, which are individually previously known, demonstrate the uses to which carbon dioxide can be put. While many processes for converting carbon dioxide into base chemicals are known, the present invention is unique in its use of carbon dioxide as a base feedstock for the manufacture of essential petrochemicals. It will be understood that the resulting products which are mentioned below as well as others which could be produced according to prevailing technology, are main materials and feed materials for the existing petrochemical industry. The present invention utilizes the existing interrelatedness between many of the main raw materials in the petrochemical

industry.

Carbon dioxide from the fermentation tanks can e.g. is reacted with carbon at elevated temperatures (such as approx. 600-1000°C) to produce carbon monoxide:

Such a process is used today in the steel industry.

Carbon monoxide can react with water at temperatures of approx. 200-500°C for the formation of hydrogen and carbon dioxide:

This process is often used in connection with coal and coke gasification. With the components supplied from these two main reactions (carbon dioxide, carbon monoxide and hydrogen), many important petrochemicals can be produced.

Carbon monoxide and hydrogen in the presence of a number of well-known mixed metal oxide catalysts can e.g. combined at temperatures of approx. 300-600°C and press at approx. 100-200 atmospheres for the formation of both methanol and benzene:

Methanol can also be produced using the well-known Fisher-Tropsch process.

Furthermore, carbon monoxide can be combined with methane (which can be produced from carbon monoxide and hydrogen, anaerobic treatment, or natural gas) and water at temperatures of approx. 300-600°C over iron catalysts for the formation of ethanol and iron oxide:

It is through this type of synthetic production of ethanol that gives access to larger production quantities of ethanol without increasing the quantity of cellulosic starting materials. Acetylene can also be produced from methane with a low electrical discharge, and ethylene, which is a key chemical in the petrochemical industry, can be produced.

It will be clear from the foregoing that for full utilization of the carbon dioxide by-product, this will not only provide the chemicals necessary for the production of an ethanol-based fuel, but also other chemicals that can be used directly or as intermediate products in the petrochemical industry .

It will be understood that the described continuous ethanol production process allows for maximizing the efficiency of each step in the overall process. For example, in the previously known batch methods it was necessary to carry out several operations in the same cooking vessel; in the present invention, on the other hand, each process step can be carried out in a container that is specially designed for each operation and at the temperature and pressure conditions that are most suitable for that operation. By performing each operation under optimal conditions, the ethanol yield can. greatly improved.

Furthermore, according to the present invention, it is not necessary to use large cooking containers (approx. 37,854-49,210.2 liters) and fermentation containers (approx. 1,892,700 liters) as in the prior art and which take up considerable floor space. It will be understood that such large containers are not energy efficient in the heating or pressure steps and do not contribute to achieving and maintaining uniform mixing and temperature conditions, such uniform conditions being particularly critical during the fermentation process. Such large containers also result in long time delays with a view to heating and cooling the large amounts of solution.

One of the most important advantages of the present invention is that the fermentation time is dramatically reduced from approx. 72 hours for a total of around 3-6 hours. This reduction is possible due to the high yeast population and the minimization of ethanol inhibition. Because there is not a constant flow of slurry into the fermentation vessel and ethanol out of the vessel, you get a continuous multiplication of yeast during the fermentation process, which maintains an optimal population.

In consideration of the foregoing, it will be understood that the present invention can be carried out in many specific forms and in specific embodiments that are not exemplified above, without leaving the framework or essential characteristics of the invention. The described embodiment shall in all respects only be regarded as illustrative and not restrictive and the framework of the invention is therefore indicated in the accompanying claims rather than in the preceding description. All variations that will be covered by the meaning of and the equivalence area for the claims shall be covered of their frame.

Claims (27)

1. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weak acid solution to thereby form a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; bringing the undissolved cellulosic material into contact with concentrated acid at a temperature in the range from approx. -1.1 to approx. 15.6°C to thereby form another. solution comprising dissolved cellulose and a solid waste; removal of the solid waste from the second solution; precipitation of cellulose from the second solution; and hydrolyzing with a weakly acidic solution the hemicellulose from the first solution and the precipitated cellulose from the second solution to thereby form fermentable sugars. 2. Method according to claim 1, where the cellulosic material is a waste material selected from the group consisting of corn residues, forestry material, "feedlot", crops, municipal or industrial waste. 3. Method according to claim 1, where the concentration of the first weakly acidic solution in which the hemicellulose is dissolved is from approx. 0.5 to approx. 2.0 volume percent. 4. Method according to claim 3, where the acid in the first weakly acidic solution is sulfuric acid. 5. Method according to claim 3, where the cellulose-containing material and the first weakly acidic solution are heated to a temperature in the range from approx. 93.3 to approx.' 148.9°C at a pressure from approx. 0.35 to approx. 3.5 kg/cm <2> in a period from approx. 2 to approx. 10 minutes. 6. Method according to claim 1, where the concentration, calculated by volume, of said concentrated acid solution is from approx. 60 to approx. 90%. 7. Method according to claim 6, where the acid in said concentrated acid solution is sulfuric acid. 8. Method according to claim 1, where the second weakly acidic solution with which the precipitated cellulose and hemicellulose is hydrolysed to fermentable sugars has a concentration from approx. 0.5 to approx. 10 percent by volume. 9. Method according to claim 8, where the acid in said second weakly acidic solution is sulfuric acid. 10. Method according to claim 8, where the precipitated cellulose and hemicellulose are hydrolysed at a temperature in the range from approx. 93.3 to approx. 204.4°C at a pressure from approx. 1.05 to approx. 14 kg/cm 2 in a period from approx. 2 to approx. 10 minutes. 11. Method according to claim 1, where the cellulose is precipitated from the second solution by dilution with methanol. 12. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining a feed material, at least a portion of which is a cellulosic material; dissolution of at least part of the cellulosic material with a first weak sulfuric acid solution having a concentration from approx. 0.5 to approx. 2.0 volume percent at a temperature from approx. 93.3 to approx. 148.9°C at a pressure from approx. 0.35 to approx. 3.5 kg/cm 2 in a period from approx. 2 to approx. 10 minutes; separating the first solution from undissolved cellulosic material; bringing the undissolved cellulosic material into contact with concentrated sulfuric acid at a temperature from approx. -1.1 to approx. 15.6°C in a period from approx. 1 to approx. 10 minutes, thereby forming another solution comprehensively dissolved cellulose and a solid waste; removal of the solid waste from the second solution; precipitation of cellulose from said second solution by dilution with methanol; and hydrolyzing the hemicellulose from the first solution and the precipitated cellulose from the second solution with a weak sulfuric acid solution which has a concentration of approx. 0.5 to approx. 10 volume percent at a temperature from approx. 93.3 to approx. 204.4°C at a pressure from approx. 1.05 to approx. 14 kg/cm 2 in a period from approx. 2 to 10 minutes. 13. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weakly acidic solution to thereby form a first solution comprising hemicellulose; cellulosic material; pressurizing the undissolved cellulosic material with steam to a first pressure state at a temperature in the range from approx. 248.9 to approx. 315.6°C; breaking up the internal structure of the undissolved cellulosic material by passing said undissolved cellulosic material from the first pressure state to another pressure state at a substantially reduced pressure range; and hydrolyzing with another weakly acidic solution the hemicellulose from the first solution and the broken down cellulosic material to thereby form fermentable sugars. 14. Method according to claim 13, where the cellulosic material is a waste material selected from the group consisting of corn residues, forestry material, "feedlot", crops, municipal or industrial waste. 15. Method according to claim 13, where the concentration of the first weakly acidic solution in which said hemicellulose is dissolved is from approx. 0.5 to approx. 2.0 volume percent. 16. Method according to claim 15, where the acid in the first weakly acidic solution is sulfuric acid. 17. Method according to claim 15, where the cellulose-containing material and the first weakly acidic solution are heated to a temperature in the range from approx. 93.3 to approx. 148.9°C at a pressure from approx. 0.35 to approx. 3.5 kg/cm <2> in a period from approx. 2 to approx. 10 minutes. 18. Method according to claim 13, where said first pressure state is in the range from approx. 42 to approx. 105 kg/cm <2> and said second pressure condition is around atmospheric pressure. 19. Method according to claim 13, where said undissolved cellulose-containing material is pressurized with steam to a first pressure state at a temperature in the range from approx. 248.9 to approx. 271.1°C in a period from approx. 10 to approx. 15 minutes. 20. Method according to claim 13, where the second weak acid with which the hemicellulose and the broken-down cellulose-containing material is hydrolysed to fermentable sugars is present in a concentration from approx. 0.5 to approx. 10 percent by volume. 21. Method according to claim 20, where the acid in the second weakly acidic solution is sulfuric acid. 22. Method according to claim 20, where the broken down cellulose-containing material and the hemicellulose are hydrolysed at a temperature in the range from approx. 93.3 to approx. 204.4°C at a pressure from approx. 1.5 to approx. 14 kg/cm 2 in a period from approx. 2 to 10 minutes. 23. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolution of at least part of the cellulosic material with a first weak sulfuric acid solution having a concentration from approx. 0.5 to approx. 2.0 volume percent at a temperature in the range from approx. 93.3 to approx. 148.9 C at a pressure from approx. 0.35 to approx. 3.5 kg/cm 2 in a period from 2 to approx. 10 minutes to thereby form a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; pressurizing the undissolved material with steam to a first pressure state at a temperature in the range from approx. 204.4 to approx. 315.6°C; breaking up the internal structure of the undissolved cellulosic material by spraying said undissolved cellulosic material from the first pressure state to another pressure state at a substantially reduced pressure range; hydrolyzing the hemicellulose from the first solution and the decomposed cellulosic material with another weak sulfuric acid solution having a concentration from approx. 0.5 to approx. 10% at a temperature from approx. 93.3 more about. 204.4°C at a pressure from approx. 1.05 to approx. 14 kg/cm <2> in a period from approx. 2 to approx. 10 minutes, thereby forming fermentable sugars. 24. Method for producing alcohol from fermentable material, where the method comprises: introducing fermentable material into a first container; producing alcohol and carbon dioxide from the fermentable material by mixing yeast with the fermentable material; removing alcohol vapor and carbon dioxide from the first container under a partial vacuum having a reduced pressure; concentrating the alcohol vapor by passing the alcohol vapor and carbon dioxide through a distillation column under said partial vacuum having a reduced pressure while refluxing a liquid alcohol through the distillation column; and condensation of said alcohol vapor which has been passed through the distillation column, thereby forming liquid alcohol. 25. Method according to claim 24, where the alcohol and carbon dioxide are produced from the fermentable material at a temperature in the range from approx. 29.4 to approx. 35°C for a period of time from approx. 3 to approx. 6 hours. 26. Method according to claim 25, where the yeast concentration is in the range of approx. 100-500 million cells per ml. 27. Method according to claim 25, where non-removed fermentable materials and yeast flow into another container where dead yeast cells are separated from live yeast cells, live yeast cells being recycled to the first container. 28. A method according to claim 24, wherein a gas is sprayed through the first container containing the fermentable material and the yeast, thereby assisting the removal of alcohol vapor from the first container. 29. Method according to claim 28, where the gas is carbon dioxide. 30. Method according to claim 29, where the gas is injected into the first container at a speed of approx. 0.075 to approx. 3.74 dm 3 per minute per liters of fermentable material in the first container. 31. Method according to claim 24, where the partial vacuum has a reduced pressure in the range from approx. 50.8 to approx. 66 cm mercury. 32. Method according to claim 24, where at least part of the partial vacuum is created by the condensation of said alcohol vapor to said liquid alcohol. 33. Method according to claim 32, where at least part of the partial vacuum is created by a mechanical vacuum pump. 34. Method for removing alcohol from a fermenting solution, in a fermentation process for the production of alcohol, which method comprises: spraying a gas through the fermenting solution; and removing the alcohol and gas from the fermenting solution under a partial vacuum having a reduced pressure. 35. Method according to claim 34, where the gas is carbon dioxide which is sprayed through the fermenting solution at a speed of approx. 0.075 to approx. 3.74 dm 3 per minute per liter of fermenting solution. 36. Method according to claim 34, where said partial vacuum has a reduced pressure in the range from approx. 50.8 to approx. 66 cm mercury. 37. Method for producing alcohol from cellulose-containing material, the method comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weakly acidic solution to thereby form a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; bringing the undissolved cellulosic material into contact with concentrated acid at a temperature from approx. -1.1 to approx. 15.6°C to thereby form another solution comprising undissolved cellulose and a solid waste; removing the solid waste from the second solution; precipitation of cellulose from said second solution; hydrolyzing, with another weakly acidic solution, the hemicellulose from the first solution and the precipitated cellulose from the second solution to thereby form fermentable sugars; introducing the fermentable sugars into a first container; producing alcohol and carbon dioxide from the fermentable sugars by mixing yeast with the fermentable sugars; removing alcohol vapor and carbon dioxide from the first container under a partial vacuum having a reduced pressure; concentrating the alcohol vapor by passing the alcohol vapor and the carbon dioxide through a distillation column under said partial vacuum having a reduced pressure while refluxing a liquid alcohol through the distillation column; and condensation of said alcohol vapor which has been passed through the distillation column, thereby forming liquid alcohol. 38. Process for producing alcohol from cellulose-containing material, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weakly acidic solution, thereby forming a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; pressurizing the undissolved cellulosic material with steam to a first pressure state at a temperature in the range from approx. 248.9 to approx. 315.6°C; breaking up the internal structure of the undissolved cellulosic material by passing the undissolved cellulosic material from the first pressure state to another pressure state at a substantially reduced pressure range; hydrolyzing, with another weakly acid solution, the hemicellulose from the first solution and the broken down cellulosic material, so as to form fermentable sugars; introducing fermentable sugars into a first container; production of alcohol and carbon dioxide from the fermentable sugars by mixing yeast with the fermentable sugars; removal of alcohol vapor and carbon dioxide from it. first the container under a partial vacuum having a reduced pressure; concentrating the alcohol vapor by passing the alcohol vapor and the carbon dioxide through a distillation column under said partial vacuum having a reduced pressure during reflux of a liquid alcohol through the distillation column; and condensation of said alcohol vapor which has been passed through the distillation column, thereby forming liquid alcohol. 1. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weakly acidic solution to thereby form a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; bringing the undissolved cellulosic material into contact with concentrated acid at a temperature in the range from approx. -1.1 to approx. 15.6°C to thereby form another solution comprising dissolved cellulose and a solid waste; removing the solid waste from the second solution; precipitation of cellulose from the second solution; and hydrolyzing with a weakly acidic solution the hemicellulose from the first solution and the precipitated cellulose from the second solution to thereby form fermentable sugars. 2. Method according to claim 1, where the cellulosic material is a waste material selected from the group consisting of corn residues, forestry material, "feedlot", crops, municipal or industrial waste. 3. Method according to claim 1, where the concentration of the first weakly acidic solution in which the hemicellulose is dissolved is from approx. 0.5 to approx. 2.0 volume percent, the acid in the first weakly acidic solution is sulfuric acid, and where the cellulose-containing material and the first weakly acidic solution are heated to a temperature in the range from approx. 93.3 to approx. 148.9°C at a pressure from approx. 0.35 to approx. 3.5 kg/cm <2> in a period from approx. 2 to approx. 10 minutes. 4. Method according to claim 1, where the concentration, calculated by volume, of said concentrated acid solution is from approx. 60 to approx. 90%, and is sulfuric acid. 5. Method according to claim 1, where the second weakly acidic solution with which the precipitated cellulose and hemicellulose is hydrolysed to fermentable sugars has a concentration from approx. 0.5 to approx. 10 percent by volume, the acid in said second weakly acidic solution is sulfuric acid, and where the precipitated cellulose and hemicellulose are hydrolyzed at a temperature in the range from approx. 93.3 to approx. 204.4°C at a pressure 2 from approx. 1.05 to approx. 14 kg/cm in a period from approx. 2 to approx. 10 minutes. 6. Method according to claim 1, where the cellulose is precipitated from the second solution by dilution with methanol. 7. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining a feed material, at least a portion of which is a cellulosic material; dissolution of at least part of the cellulosic material with a first weak sulfuric acid solution having a concentration from approx. 0.5 to approx. 2.0 volume percent at a temperature from approx. 93.3 to approx. 148.9°C at a pressure from approx. 0.3 5 to approx. 3.5 kg/cm 2 in a period from approx. 2 to approx. 10 minutes; separating the first solution from undissolved cellulosic material; bringing the undissolved cellulosic material into contact with concentrated sulfuric acid at a temperature from approx. -1.1 to approx. 15.6°C in a period from approx. 1 to approx. 10 minutes, thereby forming another solution comprising dissolved cellulose and a solid waste; removing the solid waste from the second solution; precipitation of cellulose from said second solution by dilution with methanol; and hydrolyzing the hemicellulose from the first solution and the precipitated cellulose from the second solution with a weak sulfuric acid solution which has a concentration of approx. 0.5 to approx. 10 percent by volume at a temperature ' ' ' ' trip from approx. 93.3 to approx. 204.4 C at a pressure from approx. 1.05 to approx. 14 kg/cm 2 in a period from approx. 2 to 10 minutes. 8. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining1 a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weakly acidic solution to thereby form a first solution comprising hemicellulose; cellulosic material; pressurizing the undissolved cellulosic material with steam to a first pressure state at a temperature in the range from approx. 248.9 to approx. 315.6°C; breaking up the internal structure of the undissolved cellulosic material by passing said undissolved cellulosic material from the first pressure state to another pressure state at a substantially reduced pressure range; and hydrolyzing with another weakly acidic solution the hemicellulose from the first solution and the broken down cellulosic material to thereby form fermentable sugars. 9. Method according to claim 8, where the cellulosic material is a waste material selected from the group consisting of corn residues, forestry material, "feedlot", crops, municipal or industrial waste. 10. Method according to claim 8, where the concentration of the first weakly acidic solution in which said hemicellulose is dissolved is from approx. 0.5 to approx. 2.0 volume percent, where the acid in the first weakly acidic solution is sulfuric acid, and where the cellulose-containing material and the first weakly acidic solution are heated to a temperature in the range from approx. 93.3 to approx. 148.9°C at a pressure from approx. 0.35 to approx. 3.5 kg/cm 2 in a period from approx. 2 to approx. 10 minutes. 11. Method according to claim 8, where said first pressure state is in the range from approx. 42 to approx. 105 kg/cm <2> and said second pressure state is around atmospheric pressure. ' .■ < ' •' 12. Method according to claim 8, where said undissolved cellulose-containing material is pressurized with steam to a first pressure state at a temperature in the range from approx. 248.9 to approx. 271.1°C in a period from approx. 10 to approx. 15 minutes. 13. Method according to claim 8, where the second weak acid with which the hemicellulose and the broken-down cellulose-containing material is hydrolysed into fermentable sugars is present in a concentration from approx. 0.5 to approx. 10 percent by volume, the acid in the second weakly acidic solution is sulfuric acid, and where the broken-down cellulose-containing material and the hemicellulose are hydrolyzed at a temperature in the range from approx. 93.3 to approx. 204.4°C at a pressure from approx. 1.5 to approx. 14 kg/cm 2 in a period from approx. 2 to 10 minutes. 14. Process for converting cellulosic material into fermentable sugars, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolution of at least part of the cellulosic material with a first weak sulfuric acid solution having a concentration from approx. 0.5 to approx. 2.0 volume percent at a temperature in the range from approx. 93.3 to approx. 148.9°C at a pressure from approx. 0.35 to approx. 3.5 kg/cm 2 in a period from 2 to approx. 10 minutes to thereby form a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; pressurizing the undissolved material with steam to a first pressure state at a temperature in the range from approx. 204.4 to approx. 315.6°C; breaking up the internal structure of the undissolved cellulosic material by spraying said undissolved cellulosic material from the first pressure state to another pressure state at a substantially reduced pressure range; hydrolyzing the hemicellulose from the first solution and the broken-down cellulosic material with another weak sulfuric acid solution having a concentration from approx. 0.5 to approx. 10% at a temperature from approx. 9 3.3 to approx. 204.4°C at a pressure from approx. 1.05 to approx. 14 kg/cm <2> in a period from approx. 2 to approx. 10 minutes, thereby forming fermentable sugars. 15. Method for producing alcohol from*fermentable material, where the method includes: introducing fermentable material into a first container; producing alcohol and carbon dioxide from the fermentable material by mixing yeast with the fermentable material; removing alcohol vapor and carbon dioxide from the first container under a partial vacuum having a reduced pressure; concentrating the alcohol vapor by passing the alcohol dainpen and carbon dioxide through a distillation column under said partial vacuum having a reduced pressure while refluxing a liquid alcohol through the distillation column; and condensation of said alcohol vapor which has been passed through the distillation column, thereby forming liquid alcohol. 16. Method according to claim 15, where the alcohol and carbon dioxide are produced from the fermentable material at a temperature in the range from approx. 29.4 to approx. 35°C for a period of time from approx. 3 to approx. 6 hours, the fermentation concentration is in the range from approx. 100-500 million cells per ml, and where non-removed fermentable materials and yeast flow into another container where dead yeast cells are separated from live yeast cells, live yeast cells being recycled to the first container. 17. Method according to claim 15, where a gas is sprayed through the first container containing the fermentable material and the yeast, to thereby assist the removal of alcohol vapor from the first container. 18. Method according to claim 17, where the gas is carbon dioxide, and where the gas is injected into the first container ' • " ' 3 at a rate of from about 0.075 to about 3.74 dm per minute per liters of fermentable material in the first container. 19. Method according to claim 15, where the partial vacuum has a reduced pressure in the range from approx. 50.8 to approx. 66 cm mercury. 20. Method according to claim 15, where at least part of the partial vacuum is created by the condensation of said alcohol vapor to said liquid alcohol, and where at least part of the partial vacuum is created by a mechanical vacuum pump. 21 Method for removing alcohol from a fermenting solution, in a fermentation process for the production of alcohol, which method comprises: spraying a gas through the fermenting up- . solution; and removing the alcohol and gas from the fermenting solution under a partial vacuum having a reduced pressure. 22. Method according to claim 21, where the gas is carbon dioxide which is sprayed through the fermenting solution at a speed of approx. 0.075 to approx. 3.74 dm 3 per minute per liter of fermenting solution. 23. Method according to claim 21, where said partial vacuum has a reduced pressure in the range from approx. 50.8 to approx. 66 cm mercury. 24. Process for producing alcohol from cellulose-containing material, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weakly acidic solution to thereby form a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; bringing the undissolved cellulosic material into contact with concentrated acid at a temperature from approx. -1.1 to approx. 15.6°C to thereby form another solution comprising undissolved cellulose and a solid waste; ' .. < ■ removing the solid waste from the second solution; precipitation of cellulose from said second solution; hydrolyzing, with another weakly acidic solution, the hemicellulose from the first solution and the precipitated cellulose from the second solution to thereby form fermentable sugars; introducing the fermentable sugars into a first container; producing alcohol and carbon dioxide from the fermentable sugars by mixing yeast with the fermentable sugars; removing alcohol vapor and carbon dioxide from the first container under a partial vacuum having a reduced pressure; concentrating the alcohol vapor by passing the alcohol vapor and the carbon dioxide through a distillation column under said partial vacuum having a reduced pressure while refluxing a liquid alcohol through the distillation column; and condensation of said alcohol vapor which has been passed through the distillation column, thereby forming liquid alcohol. 25. Process for producing alcohol from cellulose-containing material, the process comprising: obtaining a feed material of which at least a part is a cellulosic material; dissolving at least a portion of the cellulosic material with a first weakly acidic solution, thereby forming a first solution comprising hemicellulose; separating the first solution from undissolved cellulosic material; pressurizing the undissolved cellulosic material with steam to a first pressure state at a temperature in the range from approx. 248.9 to approx. 315.6°C; breaking up the internal structure of the undissolved cellulosic material by passing the undissolved cellulosic material from the first pressure state to another pressure state at a substantially reduced pressure range; hydrolysis, with another slightly acidic solution, of the hemicellulose from the first solution and the broken down cellulosic material, thereby forming fermentable sugars; introducing fermentable sugars into a first container; producing alcohol and carbon dioxide from the fermentable sugars by mixing yeast with the fermentable sugars; removing alcohol vapor and carbon dioxide from the first container under a partial vacuum having a reduced pressure; concentrating the alcohol vapor by passing the alcohol vapor and carbon dioxide through a distillation column under said partial vacuum having a reduced pressure during reflux of a liquid alcohol through the distillation column; and condensation of said alcohol vapor which has been passed through the distillation column, thereby forming liquid alcohol. 26. Method for delignification of cellulosic material, comprising the following steps: providing a feed material at least a portion of which is a cellulosic material; pressurizing the feed material with steam to a first pressure state at a temperature in the range from approx. 204.4 to approx. 315.6°C; and breaking up the internal structure of at least part of the cellulose-containing material by spraying this material from the first pressure state to a substantially reduced second pressure state, the sprayed cellulose-containing material being substantially delignified so that it can therefore easily be hydrolyzed into fermentable sugars. 27. Method according to claim 26, further comprising hydrolyzing the sprayed cellulosic material with a weak acid solution, in order thereby to give fermentable sugars.