CN103298918A - Low-grade coal slurry production method, low-grade coal slurry production device, and low-grade coal gasification system - Google Patents

Abstract

An object of the present invention is to provide a simple production method and production device for high-slurry-concentration and low-viscosity low-grade coal slurry suitable for gasification by a pressurized gasifier, and a gasification system including such a production device. The manufacturing method of the low-grade coal slurry of the present invention comprises: heating and drying the coarsely pulverized low-grade coal, and recovering the water vapor discharged from the low-grade coal as condensed water at the same time; The second step is to add the condensed water and dispersant obtained in the first step to the low-grade coal, and liquefy the low-grade coal slurry by wet pulverization. Moreover, the manufacturing apparatus of the low-grade coal slurry of the present invention has: a drying device for heating and drying coarsely pulverized low-grade coal; A recovery device; and a wet crushing device for liquefying low-grade coal slurry by adding condensate and dispersant to the heated and dried low-grade coal.

Description

Method for manufacturing low-grade coal slurry, device for manufacturing low-grade coal slurry, and gasification system for low-grade coal

technical field

The present invention relates to a method and apparatus for producing a slurry of a fuel suitable for a pressurized gasifier from a low-grade coal such as lignite. Also, the present invention relates to a low-grade coal gasification system including a pressurized gasifier using such a slurry as fuel.

Background technique

In recent years, the consumption of energy resources around the world has been rapidly expanding, and the prices of oil, coal, and natural gas, which are major energy sources, have continued to rise. Therefore, how to effectively use these energy sources has become an important issue.

Coal used as a general fuel is not only power generation efficiency and cost, but also high calorific value bituminous coal is used from the viewpoint of safety in logistics such as transportation and storage. However, with the economic growth of emerging countries, the supply and demand of bituminous coal has become tense worldwide.

On the other hand, it is estimated that the buried amount of low-grade coal such as lignite, sub-lignite, or sub-bituminous coal exceeds the buried amount of high-grade coal such as bituminous coal by 600 billion tons or more. However, since low-grade coal has a high water content, when it is used as a fuel for power generation boilers, etc., thermal efficiency is low, and power generation costs become high. In addition, since lignite is highly reactive and has a high risk of spontaneous combustion when it is dried, it is difficult to transport and store, and is hardly used at present.

Also, the emission of carbon dioxide (CO ₂ ) caused by coal power generation is on a global trend of rapid increase, which has become an important factor causing the global warming effect. Since coal emits more CO ₂ per unit of calorific value than oil or natural gas, the demand for reducing CO ₂ emissions is increasing, and developed countries including Japan are curbing the use of coal.

Low-grade coal such as lignite is a promising fuel resource that is very cheap and has a large amount of deposits. However, due to the above-mentioned problems, it is not actually used effectively. Therefore, technical development is underway for a method of gasifying lignite near a coal mine and utilizing the obtained synthesis gas. "Synthetic gas" refers to raw coal gas containing hydrogen (H ₂ ), carbon monoxide (CO), carbon dioxide (CO ₂ ) or methane produced from hydrocarbons such as coal or natural gas, and is used for synthesis of ammonia, Generic term for raw material gases such as methanol synthesis and hydrogen production.

In particular, the method of gasifying low-grade coal such as lignite near coal mines, separating and recovering CO ₂ from the generated synthesis gas, and utilizing it as a CO ₂ -free synthesis gas has attracted attention. For example, the method of gasifying lignite, separating and purifying hydrogen from the resulting synthesis gas, transporting it as liquid hydrogen after liquefaction, and using it as a fuel for gas turbines or gas engines can be expected to be realized in the future hydrogen society .

Regarding the technology of gasifying bituminous coal using a coal gasifier, wet pulverization of bituminous coal to liquefy its slurry, supplying the bituminous coal liquefied with slurry while supplying oxygen to the gasifier operating at high temperature and high pressure Wet oxygen-blown gasifiers are already operating as commercial plants. In addition, a method of finely pulverizing bituminous coal, transporting the pulverized coal in an air stream, and supplying it to the gasifier is also operated as a commercial facility.

When bituminous coal is gasified using a pressurized gasifier, handling and transportation will be facilitated by adding additives such as water and a dispersant to pulverized bituminous coal to make the bituminous coal a slurry. In addition, since the price per unit of heat is lower than that of heavy oil, etc., it attracts attention as a fuel alternative to petroleum.

When coal is supplied as a slurry to a pressurized gasifier, low viscosity makes handling and transportation easier, but energy efficiency decreases when the slurry concentration (coal concentration) becomes low. In particular, low-grade coal such as lignite has a higher water content than bituminous coal, so energy efficiency significantly decreases when the slurry concentration decreases. Therefore, a method for producing a high-concentration and low-viscosity low-grade coal slurry has been sought.

Here, Patent Document 1 discloses a method for obtaining a slurry with as high a coal content as possible (about 70% by weight) at a preferred apparent viscosity of about 1000 cP using low-grade coal as a raw material coal , when mixing the dehydrated filter cake, water and dispersant, the mixing is divided into two stages. In the first stage, no dispersant is added or a small amount of dispersant is added to the degree of no flow, and then the filter cake and water are mixed. kneading, and when the kneaded product becomes a paste, a dispersant is added for further kneading.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 11-335680.

Contents of the invention

The problem to be solved by the invention

Since lignite also has a moisture content of 30 to 70%, when water is further added to liquefy the slurry, the total moisture in the slurry (the sum of the moisture contained in the lignite and the moisture outside the lignite as the dispersion medium of the slurry) becomes extremely high, a large amount of heat is consumed due to water evaporation in the pressurized gasifier, and the energy efficiency becomes extremely low. Therefore, a method of liquefying a low-grade coal-water slurry such as lignite with a high water content and supplying it to a pressurized gasifier for gasification has hardly been studied conventionally.

FIG. 2 is a schematic process diagram of the slurry production method disclosed in Patent Document 1. FIG. The slurry production method disclosed in Patent Document 1 can produce high-concentration slurry even when lignite or subbituminous coal with high hygroscopicity and high water content (30 to 70% by weight) and hydrophilic surface is used.

In the slurry production method disclosed in Patent Document 1 (claim 3), in the first step (crushing step), water is added to lignite or sub-bituminous coal, and a low-concentration slurry (10-40 weight%). However, water conservancy infrastructure is often incomplete near coal mines, and it is difficult to predictably secure large amounts of water.

Next, the slurry modified by hot water treatment (pressure 12-15MPa, temperature 250-330°C) in the second step (modification step) is dehydrated in the third step (dehydration step) to become Dehydrated filter cake. However, since the dehydrated filter cake has no fluidity, its handling and transportation are difficult. Next, in the fourth step (first kneading step), the dehydrated filter cake is kneaded and reslurried, but since it becomes a paste without fluidity, its handling and transportation become difficult. In addition, fine pulverization of lignite or the like cannot be expected during kneading.

In addition, in the fifth step (second kneading step), a dispersant is added to prepare an aqueous slurry, but it is difficult to uniformly disperse the dispersant during kneading.

An object of the present invention is to provide a simple method for producing a low-grade coal slurry having a high slurry concentration and low viscosity, which is suitable for gasification by a pressurized gasifier.

means of solving problems

The inventors of the present invention have intensively studied in order to solve the above-mentioned conventional technical problems of producing low-grade coal slurry. As a result, it was found that instead of adding water from the outside to the pulverized low-grade coal to slurry it, if the water vapor generated during evaporation and dehydration after heating and drying the low-grade coal is recovered and used as condensed water, it is possible The moisture contained inside the low-grade coal is reduced, and the moisture outside the low-grade coal serving as a dispersion medium is increased. Also, the inventors have found that the total water content in the slurry is the same as in the prior art even when low-grade coal is used as the raw material coal by doing so, and that a low-viscosity slurry that is easy to handle and transport can be obtained, and completed the present invention.

Specifically, the present invention relates to the first step of: heating and drying coarsely pulverized low-grade coal while recovering water vapor discharged from the low-grade coal as condensed water; A method for producing low-grade coal slurry in the second step of adding the condensed water and dispersant obtained in the first step to coal, and liquefying the low-grade coal slurry by wet pulverization.

In the first step, the water contained in the coarsely pulverized low-grade coal is discharged as water vapor, thereby drying the low-grade coal. Also, since the fine structure of the surface of the low-grade coal is clogged by heating tar components, or the surface hydrophilic functional groups are changed to hydrophobic functional groups, it can also be expected that the discharged water is reabsorbed by the low-grade coal.

Here, low-grade coal refers to lignite, sub-bituminous coal, sub-lignite or mixture thereof, but it is preferred that the present invention is particularly applicable to lignite.

In the second step, the reformed low-grade coal is wet pulverized and then slurried, but cooled by recovering the water vapor (self-discharged water) discharged from the low-grade coal in the first step, and the It is recycled as condensed water and utilized, even in the vicinity of coal mines with less water resources, low-grade coal slurry can be prepared.

Preferably, the heat drying in the first step is performed by indirect heat treatment at 100°C or higher and 200°C or lower.

Preferably, the moisture content of the low-grade coal after the first step is 15% by weight or less. The moisture content of the low-grade coal mentioned here refers to the percentage of the moisture contained in the low-grade coal to the total weight of the low-grade coal.

Preferably, the slurry concentration in the second step is not less than 40% by weight and not more than 65% by weight. The slurry concentration mentioned here refers to the percentage by weight calculated based on the dry coal basis (the weight after converting the moisture content as 0% by weight, that is, the dry basis) of the low-grade coal contained in the slurry.

Preferably, the manufacturing method of the low-grade coal slurry includes a third step of further performing a high-speed stirring treatment on the obtained slurry after the second step. By performing the high-speed stirring treatment, the stability of the slurry is increased, and it is also possible to store the slurry before supplying it to the pressurized gasification furnace. the

Preferably, the dispersant is a polystyrene dispersant, a naphthalenesulfonic acid dispersant, a methacrylic acid dispersant or a ligninsulfonic acid dispersant, and the amount added to the slurry is relative to the low-grade coal 0.2% by weight or more and 2% by weight or less of the dry weight of the

Also, the present invention relates to a drying device for heating and drying coarsely pulverized low-grade coal; a condensate recovery device for recovering water vapor discharged from the low-grade coal by heating and drying as condensed water; In the final low-grade coal, condensate and dispersant are added to liquefy the low-grade coal slurry, which is a low-grade coal slurry manufacturing device for the wet pulverization device.

Preferably, the drying device is an indirect heating type drying device that is easy to increase in size.

Preferably, the manufacturing device of the low-grade coal slurry of the present invention further includes a dry pulverization device for coarsely pulverizing the low-grade coal.

Preferably, the manufacturing device of the low-grade coal slurry of the present invention has a stirring device for further performing a high-speed stirring process on the slurry obtained by the wet pulverization device.

In addition, the present invention relates to: a manufacturing device of the low-grade coal slurry; a transport pipe for transporting the slurry obtained from the wet pulverization device or the agitation device; A gasification system for low-grade coal in a pressurized gasifier.

The above object, other objects, features, and advantages of the present invention will be clarified from the detailed description of the following preferred embodiments with reference to the accompanying drawings.

Invention effect

According to the present invention, a low-grade coal slurry having a high slurry concentration and low viscosity suitable for gasification by a pressurized gasifier can be easily produced. In addition, it is also possible to efficiently gasify low-grade coal such as lignite, which has not been effectively utilized conventionally, using a pressurized gasifier.

Description of drawings

Fig. 1 is a schematic structural diagram showing an example of a device for implementing the manufacturing method of low-grade coal slurry of the present invention;

FIG. 2 is a schematic process diagram of a method for producing a low-grade coal slurry disclosed in Patent Document 1. FIG.

Detailed ways

Hereinafter, the present invention will be described in detail. In addition, this invention is not limited to the following description.

FIG. 1 is a schematic configuration diagram showing an example of an apparatus for implementing the method for producing a low-grade coal slurry according to the present invention. First, low-grade coal is coarsely pulverized by the dry pulverization device 1 . At this time, it is preferable that the low-grade coal is coarsely pulverized so that particles having a particle size of 3 mm or less (particles passed through a sieve with a mesh size of 3 mm) account for 70% by weight or more, preferably 90% by weight of particles having a particle size of 3 mm or less above.

Next, the coarsely pulverized low-grade coal is supplied to the indirect heating type drying device 2 to be dried. As the indirect heating type drying device 2 , for example, a steam tube dryer, a single-shaft indirect heating type dryer, or a twin-shaft indirect heating type dryer can be used. Preferably, the heating and drying conditions are such that the temperature is not less than 100°C and not more than 200°C. By drying under such temperature conditions, the particle size remains almost unchanged, but the water contained in the low-grade coal is discharged to the outside as water vapor (evaporative dehydration).

Preferably, the low-grade coal is dried to a moisture content of 15% by weight or less, preferably 10% by weight or less, through the indirect heating drying device 2 . Also, depending on the heating conditions, since coking coal components clog the fine structure of the surface of the low-grade coal, the moisture after discharge becomes difficult to be reabsorbed by the low-grade coal, and the hydrophobicity of the surface of the low-grade coal is also expected to increase. The low-grade coal dried by the indirect heating type drying device 2 is supplied to a wet pulverization device 5 via a conveyor 4 .

On the other hand, the water vapor discharged from the low-grade coal coarsely pulverized in the indirect heating drying device 2 is supplied to the condensed water recovery device 3 to be cooled and recovered as condensed water. All or part of the collected condensed water and the dispersant are also supplied to the wet pulverization device 5 . Then, the low-grade coal is finely pulverized by the wet pulverizing device 5 to prepare low-grade coal slurry.

As the condensed water recovery device 3, for example, an air-cooled condenser or a water-cooled condenser can be used. As the wet pulverization device 5, for example, a wet ball mill or a media agitation type pulverizer can be used. Alternatively, the remaining condensate can be discarded or used for any other purpose.

Preferably, the amount of water supplied to the wet pulverization device 5 is adjusted so that the concentration of the low-grade coal slurry is in the range of 40 to 65% by weight calculated on a dry basis, and only the recovered condensed water is used And in the case of insufficient water, add the required amount of water by other methods. In addition, it is preferable to finely pulverize the low-grade coal slurry so that the low-grade coal particles with a particle size of 74 μm or less (low-grade coal particles passing through 200 mesh) account for 30 to 90% of the total low-grade coal particles.

As the dispersant, a polystyrene-based dispersant, a naphthalenesulfonic acid-based dispersant, a methacrylic acid-based dispersant, or a ligninsulfonic acid-based dispersant can be used. Preferably, the dispersant is added so that its concentration in the low-grade coal slurry is 0.2% by weight or more and 2% by weight or less relative to the dry weight of the low-grade coal contained in the low-grade coal slurry.

In addition to the dispersant, the stability of the slurry can be further improved by adding a stabilizer such as carboxymethyl cellulose and/or a thickener such as xanthan gum to the low-grade coal slurry. Preferably, the stabilizer or thickener is adjusted so that its concentration in the low-grade coal slurry is 0.001-0.05% by weight.

Even though the total water content of the low-grade coal slurry obtained by the present invention is the same as that of the conventional low-grade coal slurry, the low-grade coal contains less water and has more water as a dispersion medium. Therefore, it has higher concentration and lower viscosity than conventional low-grade coal slurry, and has physical properties suitable for gasification by a pressurized gasifier.

In the present invention, when slurrying after mixing water and coarsely pulverized low-grade coal, since a dispersant is also added at the same time, unlike the method disclosed in Patent Document 1, the dispersant can be uniformly dispersed in the slurry .

As in Patent Document 1, in the case of wet pulverization of a low-concentration slurry, a particle size distribution with fewer fine particles is formed. On the other hand, in the present invention, since the low-grade coal-water mixture with a very high concentration is wet-ground, the wet-ground low-grade coal has an ideal particle size distribution with many fine particles.

The low-grade coal slurry obtained by the wet crushing device 5 is stored in the slurry tank 6 . Preferably, the low-grade coal slurry in the slurry tank 6 is stirred by the mixer 7 (low-speed mixer) in advance. Thereafter, the low-grade coal slurry is supplied from the slurry tank 6 to the stirring device 10 through the transfer pipe 9 provided with the transfer pump 8 . By using the stirring device 10 (high-speed stirrer) to perform high-speed stirring treatment on the low-grade coal slurry, the stability of the low-grade coal slurry can be increased, thereby preventing separation of the low-grade coal.

As the stirring device 10, a line mixer or a mixing tank with a high-speed stirrer can be used. In the case of using an in-line mixer, the preferred rotation speed is 500-5000 rpm, and the residence time of the low-grade coal slurry is 10 seconds-2 minutes. The low-grade coal slurry (finished product slurry) after the high-speed stirring process is supplied to the pressurized gasification furnace through the delivery pipe 13 provided with the delivery pump 12 .

In addition, the stirring device 10 has an arbitrary structure, and in the case of immediately supplying the low-grade coal slurry in the slurry tank 6 to the pressurized gasifier, the stirring device may not be provided. At this time, the low-grade coal slurry is supplied from the slurry tank 6 to the pressurized gasifier through the transfer pipe 9 .

The low-grade coal slurry supplied to the pressurized gasifier (coal pressurized gasifier of the wet coal feeding method) is gasified there and converted into synthesis gas. The obtained synthesis gas is purified into hydrogen by separating impurities such as CO and CO ₂ as necessary. Preferably, the separated _CO2 is immobilized. Also, it is preferable to immobilize the separated CO after being oxidized to CO ₂ . In this way, a system for gasifying low-grade coal as a raw material in a pressurized gasifier is constituted.

[Example]

(first process)

Lignite (Lignite from Australia (Loy Yang lignite)) having the properties shown in Table 1 is roughly pulverized using a hammer crusher so that particles with a particle size of 3 mm or less are 90% by weight or more (the amount of particles passing through a sieve with a mesh size of 3 mm) The particles are 90% by weight or more of the whole lignite). The roughly pulverized lignite was put into an indirect heating dryer (a small steam tube dryer manufactured by Kawasaki Heavy Industries) and dried at 0.1 MPa and 180° C. for one hour to obtain dried lignite with a total moisture content of 10% by weight. The water vapor discharged from the indirect heating type dryer is cooled by a water-cooled condenser and recovered as condensed water.

[Table 1]

。

.

(second process)

Condensed water and a polystyrene-based dispersant were added to 3 kg of dry lignite, and then put into a wet ball mill (φ300 mm×L300 mm, volume: about 21 L). The amount of condensed water added was adjusted so that condensed water was 49% by weight relative to the total weight of lignite (dry coal basis), condensed water and polystyrene. Moreover, 0.7 weight% of polystyrene type dispersants were added with respect to dry lignite.

The condensed water and the polystyrene-based dispersant put into the wet ball mill were pulverized in batches to obtain a lignite slurry in which the lignite passed through 200 mesh was 85% by weight of the whole lignite. The concentration of the lignite slurry was 50% by weight on a dry coal basis, and the apparent viscosity was 1.8 Pa·s (1800 cP) under the conditions of a shear rate of 100 sec ^-1 and a temperature of 25°C. Moreover, when this lignite slurry was left to stand at room temperature (room temperature) for 7 days in a polyethylene container with an inner volume of 500 mL, the amount of lignite sedimentation was about 10% by volume.

(third process)

The 50 lignite slurry obtained in the above second step was further treated with a high-speed mixer (manufactured by PRIMIX Corporation, TK HOMO MIXER MARK II 2.5 type) at 1000 rpm for one minute. The apparent viscosity of the lignite slurry after the high-speed stirring treatment was 1.2 Pa·s (1200 cP) under the conditions of a shear rate of 100 sec ^-1 and a temperature of 25°C. After the lignite slurry after the high-speed stirring treatment was left to stand at room temperature (room temperature) for 7 days in a polyethylene container with an inner volume of 500 mL, the lignite sedimentation amount was about 7% by volume. Thus, it was confirmed that the stability of the lignite slurry obtained in the second step was increased by further performing the high-speed stirring treatment.

Based on the above description, many improvements and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description is given as an illustration only, and is provided for the purpose of teaching the best mode for carrying out the present invention to those skilled in the art. Substantial changes may be made in its structural and/or functional details without departing from the spirit of the invention.

Industrial Applicability

The method for producing low-grade coal slurry, the device for producing low-grade coal slurry, and the gasification system for low-grade coal of the present invention are useful in the field of fuel or energy.

Symbol Description

1: Dry crushing device;

2: Indirect heating drying device;

3: Condensed water recovery device (condenser);

4: Conveyor;

5: wet crushing device;

6: slurry tank;

7: mixer (low speed mixer);

8, 12: pump for delivery;

9, 13: Conveyor piping;

10: Stirring device (high-speed mixer);

11: Motor.

Claims (11)

1. the manufacture method of low grade coal slurries is characterized in that, the manufacture method of described low grade coal slurries has:

Low grade coal after the coarse reduction is carried out heat drying, and the water vapour that will discharge from low grade coal is as first operation of water of condensation recovery simultaneously; With

In the low grade coal after heat drying is handled, be added on the water of condensation and the dispersion agent that obtain in first operation, by wet pulverization second operation that low grade coal is slurried.

2. the manufacture method of low grade coal slurries according to claim 1 is characterized in that, the heat drying of described first operation is handled by the indirect heating below 200 ℃ more than 100 ℃ and carried out.

3. the manufacture method of low grade coal slurries according to claim 1 is characterized in that, the water ratio of the low grade coal after described first operation is below the 15 weight %.

4. the manufacture method of low grade coal slurries according to claim 1 is characterized in that, the concentration of slurry in described second operation is below the above 65 weight % of 40 weight %.

5. the manufacture method of low grade coal slurries according to claim 1 is characterized in that,

Described dispersion agent is polystyrene type dispersion agent, naphthene sulfonic acid class dispersion agent, methacrylic dispersion agent or sulfomethylated lignin acids dispersion agent,

The addition that described dispersion agent adds to slurries is with respect to more than the 0.2 weight % of the dry weight of low grade coal below the 2 weight %.

6. according to the manufacture method of any described low grade coal slurries in the claim 1 to 5, it is characterized in that the manufacture method of described low grade coal slurries has after described second operation, the slurries that obtain are carried out the 3rd operation that high-speed stirring is handled.

7. the manufacturing installation of low grade coal slurries is characterized in that, the manufacturing installation of described low grade coal slurries has:

Low grade coal after the coarse reduction is carried out the drying installation of heat drying;

The condensate water recovery device that will reclaim as water of condensation by the water vapour that heat drying is discharged from low grade coal; With

In the low grade coal behind heat drying, add water of condensation and dispersion agent, the wet pulverization device that low grade coal is slurried.

8. the manufacturing installation of low grade coal slurries according to claim 7 is characterized in that, described drying installation is the indirect heating type drying installation.

9. the manufacturing installation of low grade coal slurries according to claim 7 is characterized in that, the manufacturing installation of described low grade coal slurries also possesses the dry ground device that low grade coal is carried out coarse reduction.

10. the manufacturing installation of low grade coal slurries according to claim 7 is characterized in that, the manufacturing installation of described low grade coal slurries has the whipping appts that the slurries that obtain by described wet pulverization device is further carried out the high-speed stirring processing.

11. the gasification system of a low grade coal is characterized in that, the gasification system of described low grade coal has:

The manufacturing installation of the described low grade coal slurries of claim 7;

The conveying pipe arrangement that the slurries that obtain from described wet pulverization device or described whipping appts are carried; With

To the pressurized-gasification furnace that gasifies by the slurries of carrying pipe arrangement to carry.

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