Method and equipment for increasing concentration of coal water slurry by utilizing coal gasification fine slag resources

Abstract

The application provides a method for increasing the concentration of coal water slurry by recycling coal gasification fine slag, which comprises the following steps: mixing black water treated by gasification flash treatment and a flocculating agent through a static mixer and then entering a black water settling tank for standing, forming high-concentration coal gasification fine slag water at the bottom of the black water settling tank, and directly sending the coal gasification fine slag water to a mill by a fine slag pump after pressurization; sending crushed coal to a raw coal bin for buffering, metering by a bottom coal weighing feeder and then entering the mill; adding coal water slurry additives and water into the mill, mixing and grinding the coal gasification fine slag, the crushed coal, the coal water slurry additives and the water in the mill to obtain high-concentration coal water slurry. The coal gasification fine slag is recycled to a coal water slurry preparation system, the particle size distribution of the coal water slurry is optimized, the stacking efficiency is improved, the concentration of the coal water slurry is increased, the production cost is reduced, waste is recycled, the gasification efficiency is improved, the gasification consumption is reduced, and the environmental protection benefit and the economic benefit are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal gasification, in particular to a method and equipment for improving the concentration of coal water slurry by utilizing fine slag from coal gasification. BACKGROUND

[0002] Coal gasification is a technology that can efficiently and cleanly utilize coal. After gasification, coal becomes a crude synthetic gas, which is an important raw material source for carbon-based chemical industry. Coal water slurry is a low-pollution, high-efficiency, and pipeline-transportable oil-replacing coal-based fluid fuel and gasification raw material obtained by physical processing of about 60% coal, 39% water, and 1% additives. It changes the traditional combustion mode of coal and shows great environmental protection and energy saving advantages. In recent years, especially after the successful development of environmentally friendly coal water slurry using waste resource technology, the environmental protection benefits of coal water slurry can be greatly improved without increasing costs. Under the guarantee of abundant coal resources in China, coal water slurry has become the most basic and economical clean energy to replace oil, gas, and other energy sources. As a gasification raw material, the slurry concentration of coal water slurry is crucial to gasification, directly affecting gasification consumption, product gas quality, conversion rate, etc. Therefore, under the premise of ensuring good performance of coal water slurry, it is an inevitable trend in the field to continuously research and improve the concentration of coal water slurry.

[0003] The particle size distribution of coal water slurry is a key factor affecting the slurry concentration of coal water slurry. Optimizing the particle size distribution to improve the packing efficiency is an important way to improve the concentration of coal water slurry. Currently, the traditional rod mill slurry preparation process is limited by the conditions of the mill, and the slurry concentration of bituminous coal is generally 58-61%. The particle size distribution of coal slurry prepared by this process is as follows:

[0004]

[0005] To improve the concentration of coal slurry, a special ultrafine grinding equipment is needed to optimize the particle size distribution by adopting a staged grinding process technology. A part (5-10%) of the coal water slurry prepared by the single mill slurry preparation process is further ground by the special ultrafine grinding equipment and then returned to the original mill system to optimize the particle size distribution, achieve a bimodal or

[0006] multi-modal grading to improve the concentration of coal water slurry. The concentration of coal water slurry can reach more than 63%, generally increasing by 2%. The particle size distribution of coal water slurry prepared by the staged grinding process is as follows:

[0007]

[0008] CN107312580A discloses a coal slurry concentration and industrial wastewater treatment process and device, which includes crushing coal, then adding water and dispersing agent, and performing coarse grinding until the particle size is below 50 μm. Part of the coal slurry is ground by a fine grinder and a superfine grinder and then sent to a coal mill. Through three-stage particle size grading, the coal slurry concentration can be increased by 3 percentage points, and the gasification energy consumption can be significantly reduced.

[0009] CN113604261A discloses a method for precise grading by screening with a coal slurry separator, which can fully utilize coal slurry with large particle size, improve utilization rate, avoid repeated work of fine grinders, improve the efficiency of fine grinders, and increase the amount of fine powder in the coal slurry.

[0010] As described above, most patents on water coal slurry concentration report that part of the water coal slurry produced by the single mill system is sent to a special superfine grinding device, ground to a finer particle size, and then returned to the single mill system to improve the packing efficiency and thus the water coal slurry concentration. However, the use of special superfine grinding equipment in the grading grinding process requires large investment, is not easy to operate stably, has high power consumption, and consumes a large amount of grinding medium inside the superfine grinder, thereby increasing the operating cost. Therefore, the water coal slurry concentration process needs to be further improved. SUMMARY

[0011] Coal gasification fine slag is obtained by gasifying coal through a gasification quenching process, and then cooling the obtained product in a quenching chamber water bath. The water containing extremely fine carbon and ash particles is called black water. The black water is concentrated and heat is recovered in a flash system to obtain black water containing coal gasification fine slag, which is referred to as black water treated by gasification flash in the following text. The content of coal gasification fine slag in the black water (i.e., solid content) is 0.2wt%-1.5wt%. After the black water is mixed with a flocculating agent and then flocculated and precipitated in a settling tank, a coal gasification fine slag water containing 10wt%-20wt% high-concentration coal gasification fine slag is formed at the bottom. After dehydration by a dehydration device, a filter cake is formed, which is referred to as coal gasification fine slag. The coal gasification fine slag has a moisture content of about 60wt%, a carbon content of 25%-45%, and a calorific value of about 3000 kilocalories / kilogram. Due to the high moisture content of the filter cake, it is difficult to utilize the resource. Generally, it is sent to a slag field for landfill treatment, or to a boiler for blending combustion, or the fine slag is subjected to carbon extraction and graded utilization.

[0012] To solve the problems of improving the concentration of water coal slurry and realizing the resource utilization of coal gasification fine slag, one of the purposes of the present application is to provide a method for improving the concentration of water coal slurry by utilizing coal gasification fine slag. The coal gasification fine slag is recycled back to the water coal slurry preparation system to optimize the particle size distribution of the water coal slurry, improve the packing efficiency, and achieve the purpose of improving the concentration of the water coal slurry. This method saves energy and resources, reduces production costs, realizes the resource utilization of waste, and is beneficial to improving the gasification efficiency, reducing the gasification consumption, and improving the environmental and economic benefits of the plant.

[0013] The above object of the present application is achieved by the following technical solution:

[0014] A method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag resources, comprising the following steps:

[0015] Step 1

[0016] The gasification flash treatment black water is mixed with the flocculating agent through the static mixer 1 and then enters the black water settling tank 2 for standing and separation under the action of gravity. The coal gasification fine slag water containing 10wt%-20wt% coal gasification fine slag is formed at the bottom of the black water settling tank 2, and the coal gasification fine slag water containing 10wt%-20wt% coal gasification fine slag is directly sent to the mill 6 after being pressurized by the fine slag pump 3.

[0017] Step 2

[0018] The crushed coal is sent to the raw coal bin 4 for storage, and then enters the mill 6 after being metered by the bottom coal weighing feeder 5.

[0019] The coal gasification fine slag, the crushed coal, the coal water slurry additive and the water are mixed and ground in the mill 6 to obtain the coal water slurry with a viscosity of 300CP-1300CP (preferably 300CP-600CP) and a concentration of 64-65wt%.

[0020] According to the method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag resources, wherein,

[0021] The particle size distribution of the coal gasification fine slag is as follows:

[0022]

[0023]

[0024] According to the method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag resources, wherein the particle size distribution of the coal water slurry is as follows:

[0025]

[0026] According to the method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag resources, wherein in step 1, the concentration of the flocculating agent (the proportion of the flocculating agent in the gasification flash treatment black water) is 1ppm to 3ppm, preferably 2ppm.

[0027] According to the method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag resources, wherein in step 1, the flocculating agent is a flocculating agent commonly used in the art, such as cationic polyacrylamide.

[0028] The method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag according to the present application, wherein in step 2, the crushed coal is coal with a size less than 25 mm, preferably less than 20 mm.

[0029] The method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag according to the present application, wherein in step 3, the coal water slurry additive is a compound of naphthalene sulfonic acid methyl condensate and lignin, wherein the content of naphthalene sulfonic acid methyl condensate is 30wt%-50wt% of the compound of naphthalene sulfonic acid methyl condensate and lignin.

[0030] The method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag according to the present application, wherein in step 3, the weight ratio of coal gasification fine slag, crushed coal, coal water slurry additive and water is (8-12):(40-60):(0.06-0.10):(7-9).

[0031] The method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag according to the present application, wherein the coal water slurry is filtered by a roller screen 7 to remove large particle impurities, and then sent to a coal slurry buffer tank 8, and pressurized by a coal slurry buffer tank pump 9, and then sent to a gasification furnace to perform a gasification reaction.

[0032] The method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag according to the present application, wherein the gasification reaction is performed at a temperature of 1000-1500℃, preferably at a temperature of 1200-1400℃ (for example, 1300℃); the gasification reaction is performed at a pressure of 5-8MPa(G), preferably at a pressure of 6-7MPa(G) (for example, 6.5MPa(G)); the volume ratio of oxygen to coal water slurry is (470-520):1.

[0033] The method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag according to the present application, wherein the process flow of the method is as shown in Figure 1

[0034] Another object of the present application is to provide a coal gasification fine slag utilization equipment, comprising:

[0035] a static mixer 1 for mixing the gasification flash treatment black water with a flocculant;

[0036] a black water settling tank 2 for performing a settling treatment on the gasification flash treatment black water;

[0037] a raw coal bin 4 for buffering coal with a size less than 25 mm, and a coal weighing feeder 5 for feeding the coal with a size less than 25 mm to a mill 6;

[0038] a mill 6 for mixing and grinding the coal gasification fine slag, coal water slurry additive, water and coal obtained by the settling separation; ​

[0039] A gasification furnace for gasification treatment of water coal slurry obtained by grinding treatment;

[0040] The static mixer 1, the black water settling tank 2 and the grinder 6 are sequentially in fluid communication, the raw coal bin 4, the coal weighing feeder 5 and the grinder 6 are sequentially in fluid communication, and the grinder 6 and the gasification furnace are in fluid communication.

[0041] According to the coal gasification fine slag resource utilization equipment, the grinder 6 can be a rod grinder or other grinder commonly used in the field.

[0042] According to the coal gasification fine slag resource utilization equipment, a fine slag pump 3 is arranged on a pipeline connecting the black water settling tank 2 and the grinder 6, and the fine slag pump 3 is used to deliver the coal gasification fine slag to the grinder 6.

[0043] According to the coal gasification fine slag resource utilization equipment, a drum screen 7, a coal slurry buffer tank 8 and a coal slurry buffer tank pump 9 are arranged on a pipeline connecting the grinder 6 and the gasification furnace, the drum screen 7 is used to filter out large-particle impurities from the water coal slurry prepared in the grinder 6, the coal slurry buffer tank 8 is used to buffer the filtered water coal slurry, and the coal slurry buffer tank pump 9 is used to deliver the filtered water coal slurry to the gasification furnace.

[0044] Beneficial effects

[0045] The method for improving the concentration of water coal slurry by using coal gasification fine slag has the following characteristics:

[0046] The coal gasification fine slag has a very fine particle size, especially 55-60% of 325 mesh (44 microns). The fine slag produced by the gasification process can be used to optimize the fine particle size distribution of the water coal slurry and improve the packing efficiency, and is sent to the grinder to improve the concentration of the water coal slurry. After mixing, the concentration can be improved by one grinding without secondary grinding, which significantly reduces the production cost of the water coal slurry, avoids the problems of large investment, high operating cost, instability, high power consumption and high internal grinding medium consumption of special ultra-fine grinding equipment;

[0047] The high-concentration coal gasification fine slag water at the bottom of the black water settling tank is sent to the grinder, and the residual carbon and waste water in the fine slag are fully resource utilized, so that the residual carbon in the fine slag can be used twice, the utilization rate of carbon is improved, and the water used for gasification and slurry preparation is saved; avoiding direct filling of the fine slag in the slag field, saving the slag transportation cost and filling disposal cost, and having good environmental protection and economic benefits;

[0048] After the coal gasification fine slag is resourcefully utilized by the coal water slurry concentration, the coal water slurry particle size distribution is better, the accumulation efficiency is higher, the particle size of 325 mesh (44 microns) accounts for 30-40%, and the coal water slurry concentration is increased by more than 3% than the conventional single mill slurry process;

[0049] After the coal water slurry is concentrated, the coal gasification reaction occurs in the gasification furnace, the oxygen consumption of the gasification furnace is reduced, the coal consumption is reduced, the gasification gas production is increased, the effective gas concentration is increased, and good economic benefits are generated;

[0050] The process technology is simple, operable, stable, and the produced coal water slurry has excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The process flow chart of the method for increasing the coal water slurry concentration for the gasification fine slag resource utilization.

[0052] REFERENCE NUMERALS

[0053] 1, static mixer, 2, black water settling tank, 3, fine slag pump, 4, raw coal bin, 5, coal weighing feeder, 6, mill, 7, drum screen, 8, coal slurry buffer tank, 9, coal slurry buffer tank pump DETAILED DESCRIPTION

[0054] Water coal slurry concentration determination:

[0055] Determined according to GB / T 18856.2-2008 (Test methods for coal water slurry Part 2: Determination of concentration).

[0056] Water coal slurry apparent viscosity determination:

[0057] Determined according to GB / T 18856.4-2008 (Test methods for coal water slurry Part 4: Determination of apparent viscosity).

[0058] Water coal slurry particle size distribution determination:

[0059] 1 Analysis method

[0060] The determination of the coal water slurry particle size distribution adopts the sieving-drying-weighing method.

[0061] 2 Analysis principle

[0062] The coal particles of different particle sizes are separated by using standard sieves, then put into an oven for drying and weighed respectively, and then the mass percentage of each particle size coal particle is calculated to obtain the particle size distribution of the coal slurry.

[0063] 3 Instruments and equipment

[0064] 3.1 Standard analysis sieve: 20 mesh, 40 mesh, 120 mesh, 200 mesh and 325 mesh;

[0065] 3.2 Industrial balance: sensitivity 0.01 g;

[0066] 3.3 Drying oven: with blower device, and accuracy 0.1 °C.

[0067] 4 Analysis procedure

[0068] After the coal slurry with known solid content (concentration) is stirred uniformly, 30-50 g (weighed to 0.01 g) is weighed, placed in the top layer (20 mesh) of the standard analysis nest sieve, and washed with water until no coal particles pass through the bottom layer sieve hole (with the washing water not turning black). The coal particles loaded in each layer of the standard sieve are placed in the drying oven at 105-110 °C for 1 h, and after cooling, the dry coal is transferred to a weighing bottle and weighed separately.

[0069] 5 Analysis results

[0070] The particle size distribution of the coal slurry is calculated according to the following formula:

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] Standard sieve (wt%, passing rate)

[0078]

[0079] The crushed coal smaller than 20 mm is sent to the raw coal bin 4 for buffering, and after metering by the bottom coal weighing feeder 5, it is fed into the mill 6 at a flow rate of 430 t / h. The coal water slurry additive (wherein the coal water slurry additive is a composite of naphthalene sulfonic acid methyl condensate and lignin, and the content of the naphthalene sulfonic acid methyl condensate is 40 wt% of the composite of naphthalene sulfonic acid methyl condensate and lignin, and the coal water slurry additive is prepared into a solution with a concentration of 8% by using water, and the flow rate is 8 t / h) and water (flow rate 65 t / h) are fed into the mill 6. The coal gasification fine slag, crushed coal, coal water slurry additive and water are mixed and ground in the mill 6 to prepare a qualified coal water slurry with a certain particle size distribution, a viscosity of 600 CP and a concentration of 64.8%.

[0080] The particle size distribution of the coal water slurry is as follows:

[0081]

[0082] The coal water slurry is filtered by the mill drum screen 7 to remove large particle impurities, and then is sent to the coal water slurry buffer tank 8. The coal water slurry buffer tank pump 9 pressurizes the coal water slurry, and then the coal water slurry is sent to the gasification furnace. The process burner sprays the coal water slurry into the gasification furnace, and the coal water slurry is partially oxidized with pure oxygen at about 1300°C and 6.5 MPa (G). The volume ratio of oxygen to coal water slurry is 490:1, and the coal water gas mainly composed of hydrogen and carbon monoxide is generated.

[0083] Example 2

[0084] A 600,000 tons / year methanol plant: The black water treated by gasification flash treatment and the flocculating agent (concentration 2 ppm) are mixed by the static mixer 1, and then are sent to the black water settling tank 2. The black water is settled in the black water settling tank 2, and the settling separation is performed under the action of the flocculating agent. The coal gasification fine slag water containing 20 wt% coal gasification fine slag is formed at the bottom of the black water settling tank 2. The coal gasification fine slag water containing 20 wt% coal gasification fine slag is directly pressurized by the fine slag pump 3 at a flow rate of 30 t / h, and then is sent to the mill 6.

[0085] The particle size distribution of the coal gasification fine slag is as follows:

[0086]

[0087] The crushed coal with a particle size less than 25 mm is sent to the raw coal bin 4 for storage. The crushed coal is metered by the bottom coal weighing feeder 5, and then is sent to the mill 6 at a flow rate of 150 t / h. The coal water slurry additive (the coal water slurry additive is a composite of naphthalene sulfonic acid methyl condensate and lignin, and the content of the naphthalene sulfonic acid methyl condensate is 45 wt% of the composite of naphthalene sulfonic acid methyl condensate and lignin. The coal water slurry additive is prepared into a solution with a concentration of 8% by using water, and the flow rate is 3 t / h) and water (flow rate 23.0 t / h) are sent to the mill 6. The coal gasification fine slag, the crushed coal, the coal water slurry additive and the water are mixed and ground in the mill 6 to prepare the qualified coal water slurry with a certain particle size distribution, a viscosity of 710 CP and a concentration of 64.9%.

[0088] The particle size distribution of the coal water slurry is as follows:

[0089]

[0090] The coal water slurry is filtered by the mill drum screen 7 to remove large particle impurities, and then is sent to the coal water slurry buffer tank 8. The coal water slurry buffer tank pump 9 pressurizes the coal water slurry, and then the coal water slurry is sent to the gasification furnace. The process burner sprays the coal water slurry into the gasification furnace, and the coal water slurry is partially oxidized with pure oxygen at about 1300°C and 6.5 MPa (G). The volume ratio of oxygen to coal water slurry is 500:1, and the coal water gas mainly composed of hydrogen and carbon monoxide is generated.

Claims

1. A method for increasing the concentration of coal water slurry by utilizing coal gasification fine slag, comprising the following steps: Step 1 mixing the black water treated by gasification flash treatment with a flocculant through a static mixer (1) and then feeding the mixture into a black water settling tank (2) to stand and separate under the action of gravity, and forming coal gasification fine slag water containing 10 wt%-20 wt% coal gasification fine slag at the bottom of the black water settling tank (2), and directly feeding the coal gasification fine slag water containing 10 wt%-20 wt% coal gasification fine slag into a mill (6) after pressurization by a fine slag pump (3); Step 2 feeding the crushed coal into a raw coal bin (4) to be temporarily stored, and then feeding the crushed coal into the mill (6) after metering by a bottom coal weighing feeder (5); Step 3 adding coal water slurry additive and water into the mill (6), and mixing and grinding the coal gasification fine slag, the crushed coal, the coal water slurry additive and the water in the mill (6) to obtain coal water slurry; In step 3, the feed into the mill is composed of the coal gasification fine slag water containing 10 wt%-20 wt% coal gasification fine slag, the crushed coal, the coal water slurry additive and the water; The weight ratio of the coal gasification fine slag, the crushed coal, the coal water slurry additive and the water is (8-12) : (40-60) : (0.06-0.10) : (7-9) ; The particle size distribution of the coal gasification fine slag is as follows: Standard sieve wt%, passing rate 14 mesh 100 40 mesh 93-98 200 mesh 60-65 325 mesh 55-60. 2.The method according to claim 1, wherein the viscosity of the obtained coal water slurry is 300 CP-1300 CP, and the concentration is 64-65 wt%.

3. The method of claim 1 or 2, wherein, The particle size distribution of the coal water slurry is as follows: Standard sieve wt%, passing rate 8 mesh 100 14 mesh ≥98 40 mesh 93-98 200 mesh 35-50 325 mesh 30-40.

4. The method of claim 1, wherein, In step 1, the concentration of the flocculant is 1 ppm to 3 ppm.

5. The method of any one of claims 1-2 and 4, wherein, In step 2, the crushed coal is crushed coal smaller than 25 mm.

6. The method of claim 3, wherein, In step 2, the crushed coal is crushed coal smaller than 20 mm.

7. The method of any one of claims 1-2, 4, and 6, wherein, In step 3, the coal water slurry additive is a composite of naphthalene sulfonate formaldehyde condensate and lignin, and the content of the naphthalene sulfonate formaldehyde condensate is 30 wt%-50 wt% of the composite of naphthalene sulfonate formaldehyde condensate and lignin.

8. The method of claim 7, wherein, After filtering out large particle impurities by a drum screen 7, the coal water slurry is fed into a coal slurry buffer tank (8), pressurized by a coal slurry buffer tank pump (9) and then fed into a gasification furnace to perform gasification reaction.

9. The method of any one of claims 1-2, 4, 6, and 8, wherein, The gasification reaction is performed at a temperature of 1000-1500 ℃, and the gasification reaction is performed at a pressure of 5-8 MPaG.

10. The method of claim 7, wherein, The gasification reaction is performed at a temperature of 1200-1400 ℃, and the gasification reaction is performed at a pressure of 6-7 MPaG. 11.A device for utilizing coal gasification fine slag according to any one of claims 1-10, comprising: a static mixer (1) for mixing the black water treated by gasification flash treatment with a flocculant; a black water settling tank (2) for settling the black water treated by gasification flash treatment; a raw coal bin (4) for temporarily storing coal smaller than 25 mm and a coal weighing feeder (5) for feeding the coal smaller than 25 mm into a mill (6). A mill (6) for mixing and grinding the coal gasification fine slag, water coal slurry additive, water and coal obtained by sedimentation separation; A gasification furnace for gasification treatment of the water coal slurry obtained by grinding treatment; The static mixer (1), the black water sedimentation tank (2) and the mill (6) are sequentially in fluid communication, the raw coal bin (4), the coal weighing feeder (5) and the mill (6) are sequentially in fluid communication, and the mill (6) and the gasification furnace are in fluid communication.

12. The apparatus of claim 11, wherein, A fine slag pump (3) is arranged on the pipeline connecting the black water sedimentation tank (2) and the mill (6), wherein the fine slag pump (3) is used for conveying the coal gasification fine slag to the mill (6).

13. The apparatus of claim 11 or 12, wherein, A drum screen (7), a coal slurry buffer tank (8) and a coal slurry buffer tank pump (9) are arranged on the pipeline connecting the mill (6) and the gasification furnace, wherein the drum screen (7) is used for filtering out large particle impurities from the water coal slurry prepared in the mill (6), the coal slurry buffer tank (8) is used for buffering the filtered water coal slurry, and the coal slurry buffer tank pump (9) is used for conveying the filtered water coal slurry to the gasification furnace.

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