WO2012019574A1 - Method for reprocessing solid and liquid waste from plant oil production - Google Patents

Abstract

The invention relates to a method for reprocessing solid, organic waste occurring in plant oil production, for example palm oil production, said waste being mainly composed of pressing residues of the oil plants and/or oil seeds and oil-containing wastewater, by hydrothermal carbonization (HTC), wherein the oil emulsified in the wastewater is sorbed by the carbon-rich solids arising from the solid waste.

Description

 Process for the treatment of solid and liquid waste from the

 Vegetable oil production

Field of the invention

The invention relates to a process for working up obtained in the production of vegetable oil solid organic waste, mainly consisting of press residues of oil crops and / or oilseeds, and oily wastewater. The invention further relates to the advantageous use of the products of the method according to the invention in the cultivation of oil palms, as well as for energy. In particular, the invention is suitable for use in palm oil production.

State of the art

 In order to meet the demand for fuel from renewable raw materials, such as biodiesel, large palm oil plantations have been created in recent years, especially in Malaysia and Indonesia. The problem with this development, in addition to the loss of virgin forest land to plant these plantations, is the large amount of solid and liquid waste produced by palm oil production.

When pressing out the palm oil in the oil mill about 1, 2 tons of press residues remain as solid waste per ton of palm oil produced, consisting of fruit fibers and palm kernel shells, so-called Empty Fruit Bunches (EFB), left. At the same time, about 3 to 4 m ^{3 of} waste water per produced ton of palm oil, so-called Palm Oil Mill Effluent (POME), is produced by the water washing of the palm oil squeezed out in the oil mill. The wastewater is contaminated with organic components such as oil, fatty acids and carbohydrates polluted wastewater. The problem is that the organic constituents form a stable oil / water emulsion with the water, which complicates the further water treatment.

The solid waste is usually incinerated to produce energy for the oil mill, which is associated with heavy smoke and therefore very stressful for the environment and humans.

Wastewater from oil extraction is collected in sewage ponds. Some of the organic matter is biodegraded anaerobically. In addition to the strong odor nuisance caused by fumigants, carbon dioxide and methane are formed to produce the climate-damaging gases. In order to avoid these disadvantages, the smoke development in the incineration of solid waste and the environmental impact of the biological wastewater treatment, F. Schuchardt described a method in which the treatment of the wastewater by anaerobic biological reactions is carried out in a fermentation reactor, so that Carbon dioxide and methane can be collected and recycled in a climate-friendly manner. The treated wastewater is then mixed in compost rents with biological waste and composted into fertilizer. Important for this method is the use of a special high-performance fermenter or a fixed bed reactor and for the operation of the compost rents the use of a special conversion machine for intensive mixing of the compost; F. Schuchardt, Federal Research Center for Agriculture, Research Report 2/2007; Dr. F. Schuchardt, Bio-Solar Biogas Symposium "Regenerative Energy from the Farm, 05.02.2003 in Heiden; M. Bockisch, Fats and Oils Handbook, AOCS Press, 1993. Description of the invention

 While prior art processes convert waste into compost and biogas, the present invention seeks to provide an alternative process which converts the waste into nutrient-containing water suitable for irrigating the oil crop plantation and produces a carbonaceous solid fuel. the eg mixed with heating oil, is suitable for energy production by burning.

The object is achieved by a method according to the characterizing part of claim 1 in conjunction with the features of its preamble. Further advantageous embodiments of the invention will become apparent from the dependent claims. In the process according to the invention, the solid, organic wastes are comminuted and mixed with the wastewater in a stirred, heated reactor to form a suspension, the pH of the suspension is adjusted in the acidic range, the atmospheric oxygen is removed from the reactor by flushing with inert gas and the reactor closed airtight and pressure-tight and the suspension heated to at least 170 ° C and maintained at elevated pressure for at least 0.5 hours, wherein the solid, organic waste is converted mainly to a carbon-rich solid and wherein the originally contained in the wastewater from the resulting oil, carbon-rich solid is sorbed and then wherein the suspension is cooled, removed from the reactor and separated into a coal and a wastewater fraction.

The conversion of biomass into high-carbon, solid products, such as coal or coal precursors such as humus, peat and brown coal is known under the name "Hydrothermal Carbonisation" or "HTC" and in the article "Glamor from the pressure cooker", Max Planck Research 2/2006, pages 20 to 25 and document WO 2008/113309 An advantage of this method is that biomass is converted into coal, or its precursors peat, humus, lignite, without thereby carbon-containing exhaust gases, such as carbon dioxide or The only waste product is water, which may still contain dissolved by-products of the HTC reaction. In the present application, the processing of solid and liquid waste of vegetable oil production, to be observed by way of example in the extraction of palm oil, but it is not obvious to use the hydrothermal carbonation, because this is not, as described in the prior art of the HTC process, water and biomass as separate starting materials, but an extremely stable oil / water emulsion and the press residues of the oil crops and / or oilseeds as biomass to be used.

The oil / water emulsion, as our own experiments have shown, so stable that they by conventional means, such as the additions of surfactants, boiling, acidification to a pH of 2, centrifuging or the addition of activated carbon, not too break is. The reason for the high stability of this emulsion is presumably the free fatty acids and glycerides also present in the wastewater, in particular including the monoglycerides, which are very effective emulsifiers. Thereafter, it was not expected that the emulsion would be broken by the HTC process, and that would solve the one important problem of this waste treatment, the treatment of waste water loaded by the oil / water emulsion.

Contrary to this assumption, however, the experiments have led to the surprising result that is transformed by the HTC process contaminated with organic contaminants wastewater palm oil production in an oil-free, with the originating from the plant residues salts and minerals advantageously loaded water, the Irrigation of palm oil plantations is well suited. The oil originally contained in the polluted wastewater is sorbed by the carbon-rich solid resulting from the plant residues. Obviously, during the performance of the HTC process, the cleavage of the emulsion is effected by the chemical and / or biological processes involved in the conversion of the biomass to coal.

The basic and well-known chemical processes of the HTC process are that hydrogen and oxygen atoms from the compounds in which they are present in the biomass, z. As glucose, are dissolved out and connect to H ₂ 0. In order not to interfere with these chemical processes, the process must be carried out under exclusion of air. Air debris must be removed by purging with inert gas prior to heating the suspension from the reactor. The energy balance of these chemical processes is overall positive, the actual amount of energy gain depends of course on the type of biomass used. However, in addition to the energy balance of the chemical processes, the energy balance of the process engineering procedures of the process must also be taken into account. So much heating energy is needed because the HTC process only runs above 170 mi t economic speed. In addition, because of the high temperature level at which the HTC process expires, good thermal insulation of the reactors is required.

In order to operate the process evenly and with a high conversion rate of the biomass, energy is also needed for continuous mixing of the feedstocks. In order to operate the HTC process economically, it is therefore important to use as much as possible of the energy generated by the chemical processes for the heating. For this reason, it is generally recommended that several reactors be operated in parallel and with a common heating system in a time-delayed manner. In principle, the process can be carried out both batchwise and continuously or semicontinuously, with suitable measures for supplying the starting materials and for removing the products being taken in the latter two cases.

Preferred embodiments of the invention

In order to produce a sufficiently large surface area of the solid parts for the economic conversion of the solid waste from vegetable oil production by the method according to the invention, it is advantageous to comminute the solid, organic waste to a suitable particle size prior to mixing into the wastewater contaminated with organic contaminants , In the case of the application of the method in palm oil production, a particle size of 2 to 5 cm has been found to be particularly suitable. In order to be able to provide enough heat energy to maintain the process temperature of at least 170, it is advantageous to adjust the dry matter content of the suspension to 10 to 40% before heating. The chemical processes of the HTC process are accelerated in an acidic environment. Therefore, it is advantageous to adjust the pH of the suspension before heating to a value between 3.0 and 6.9, preferably to 3.0 to 3.5. However, it is necessary to neutralize the oil-free water obtained by the process before use for irrigating the oil crops. Preferably, KOH is used for this purpose.

To avoid too strong boiling of the suspension in the reactor, which can lead to contamination of the reactor lid and in the cover existing measuring and safety valve stub, it is advantageous if in the reactor, before heating, by introducing inert gas, an elevated pressure, preferably from 5 to 15 bar, is generated.

In order to run the HTC process at economical speed, it is necessary to set an increased operating temperature. On the other hand, temperatures that are too high should be avoided as they burden the equipment and fittings used and lead to unnecessary energy losses. It is therefore advantageous to carry out the process at an operating temperature between 170 and 320 ^* 0. Depending on the desired degree of conversion (so-called degree of coalification) of the solid, biological waste used to peat, humus, lignite and / or hard coal, the residence time of the suspension at operating temperature is to be selected. For the present application, in which a fuel is to be obtained as the product of the process, it is desired to convert the biomass as far as possible into a carbon-rich solid, such as coal. Residence times between 0.5 and 16 hours have proved to be advantageous.

After the HTC process has ended, the suspension is separated into a solid fraction and a wastewater fraction by means of mechanical separation processes, preferably decantation, filtration or centrifugation, or combinations thereof. A preferred embodiment of the invention is the use of hardwood-rich solid product as a fuel, individually or in admixture with other fuels, eg. B. can be used as a suspension after mixing in heating or heavy oil.

A further preferred development of the invention consists in the use of the treated waste water for the irrigation of plants, preferably oil plants, wherein the waste water is previously neutralized, preferably with KOH.

Industrial Applicability

 The invention provides a process for working up solid and liquid wastes from vegetable oil production, which is distinguished by its simple apparatus and in which products are obtained which are unproblematic with regard to their disposal or which even advantageously take place at the location of the oil - Plantation can be recycled. These advantages make the use of the process according to the invention in palm oil production in tropical countries attractive.

Claims

claims: 1. A process for the treatment of solid organic waste and wastewater produced in vegetable oil production, the solid waste consisting mainly of press residues of oilseeds or oilseeds and the wastewater contains, among other organic impurities, vegetable oil residues that are emulsified in the wastewater, wherein the solid crushed organic waste and mixed with the wastewater in a stirred, heated reactor to a suspension, the pH of the suspension is adjusted in the acidic range, the atmospheric oxygen is removed by purging with inert gas from the reactor, the reactor gas-tight and the suspension heated to at least 170 ^* Ό and at least 0.5 hours at increased em pressure is maintained, wherein the solid organic waste is converted primarily to a carbon-rich solid and wherein the emulsion from waste water and vegetable oil residues broken and the oil resulting from the k ohlstoffreichen solid is sorbed and wherein the suspension is then cooled, removed from the reactor and separated into a solid and a waste water fraction. 2. The method of claim 1, wherein the solid, organic wastes are comminuted to a particle size of 2 to 5 cm.  3. The method according to any one of the preceding claims, wherein the dry matter content of the suspension is adjusted to 10 to 40% before heating. 4. The method according to any one of the preceding claims, wherein the pH of the suspension, before heating, to a value between 3.0 and 6.9, preferably adjusted to 3.0 to 3.5.  5. The method according to any one of the preceding claims, wherein in the reactor, before heating, by introducing inert gas, an elevated pressure, preferably from 5 to 15 bar, is generated.  6. The method according to any one of the preceding claims, wherein the suspension is heated to temperatures between 170 and 320 ° C and ge hold. A process according to any one of the preceding claims, wherein the suspension is held above 1700 for between 0.5 and 16 hours. 8. The method according to any one of the preceding claims, wherein the separation of the suspension into a solids and a waste water fraction by means of mechanical separation processes, preferably the decantation, filtration or centrifugation, takes place. Use of the high-carbon solid produced according to any one of the preceding claims as a fuel, singly or in admixture with other fuels.  10. Use of the treated according to one of the preceding claims wastewater for watering plants, preferably the oil plants, wherein it is previously, preferably with KOH, neutralized.