Screening and dewatering system and process for coal gasification coarse slag

Abstract

The invention provides a coal gasification coarse slag screening and dewatering system and process, and the screening and dewatering system comprises a coarse slag storage hopper, a rotary screen, a coarse particle storage tank, a fine particle storage tank, a vacuum filter and a drying unit, the drum screen sequentially comprises a rotating shaft, a cylindrical screen mesh, a drum screen shield chute, a feeding port, a discharging port and a flushing water port from inside to outside, wherein the feeding port, the discharging port and the flushing water port are formed in the cylindrical screen mesh. The process comprises the following steps: (1) washing and screening the coal gasification coarse slag to obtain fine particles and coarse particles; (2) drying the coarse particles to obtain coarse particle slag; and (3) performing vacuum filtration and dehydration on the fine particles to obtain fine particle residues and filtrate. According to the screening dehydration system and process, differential dehydration treatment is conducted on coarse slag of different particles, the dehydration effect is improved, waste water can be recycled, and pollutant emission is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of coal chemical industry, and in particular to a coarse slag screening and dehydration process and method. Background Art

[0002] At present, enterprises in coal gasification plants have a relatively wide application of liquid slag gas furnaces. The use of liquid slag gas furnaces effectively improves the recycling efficiency of coal and continuously controls and reduces the emission of pollutants. However, in the actual production process, some solid wastes produced after vaporization still have a certain impact on the ecological environment. The ash from coal gasification is also the main source of solid waste in the actual production process of coal chemical industry. The continuous storage of this waste will also cause the occupied area of ​​land to continue to expand, and it also has a serious impact on the environment. Due to the improvement of environmental protection awareness, waste slag, as a resource that people pay much attention to, is mainly used in various fields of construction. For example, gasification slag can be used for thermal insulation wall materials, and low-carbon slag can be used for building materials or bridge and road construction materials.

[0003] In the process of coal gasification, gasification slag can be divided into coarse slag and fine slag. Among them, the coarse slag is discharged in liquid form under high temperature conditions (1250-1600℃) in the gasifier, and then enters the slag pool. After cooling, the gasified coarse slag is fished out from the slag pool and transferred to the slag transport vehicle. Due to the high water content in the slag (generally about 55%), the slag is continuously drained during the loading process, resulting in a poor environment in the slag water loading area and a large amount of water resources wasted. In addition, during the transportation of the slag truck, black water is continuously drained, causing partial collapse of the slag transportation road surface, seriously affecting the transportation road and the surrounding environment. However, the current common method is to drain water under gravity for 2-4 hours, which greatly limits the processing efficiency of the wet gasification coarse slag. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and to provide a system and process for differential screening and dehydration of coarse coal gasification slag with different particles.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a screening and dehydration system for coal gasification coarse slag, comprising:

[0007] A coarse slag storage hopper is used to provide the coal gasification coarse slag to the drum screen;

[0008] A drum screen is used to receive and screen the coal gasification coarse slag to obtain coarse particles and fine particles; the drum screen comprises, from the inside to the outside, a rotating shaft, a cylindrical screen, a drum screen cover chute, and a feed port, a discharge port, and a flushing water port provided on the cylindrical screen; wherein the rotating shaft passes through the axis of the cylindrical screen so that the cylindrical screen rotates around the rotating shaft, the drum screen cover chute is sleeved on the outside of the cylindrical screen, the feed port is communicated with the outlet of the coarse slag storage hopper, the discharge port is communicated with the coarse particle storage tank, and the drum screen cover chute is communicated with the fine particle storage tank;

[0009] A coarse particle storage tank, used for receiving the coarse particle slag inside the cylindrical screen;

[0010] Fine particle storage tank: used to receive the material in the drum screen guard chute, and the discharge port of the fine particle storage tank is connected to the inlet of the vacuum filter;

[0011] A vacuum filter, used for vacuum filtering the material in the fine particle storage tank to obtain a filtrate and fine particle residue;

[0012] A drying unit is connected to the discharge port on the cylindrical screen to provide hot air to the interior of the cylindrical screen.

[0013] In some specific embodiments, the cylindrical screen is provided with sieve holes of 1 to 1.5 mm (for example, 1.1 mm, 1.2 mm, 1.4 mm), so that the spiral channel is connected to the drum screen guard chute. The inner wall of the cylindrical screen is also provided with spiral push blades, and the cavity between the spiral push blades, the rotating shaft and the cylindrical screen forms a spiral channel; in the specific screening and dehydration process, the cylindrical screen rotates driven by the rotating shaft, and the spiral push blades arranged on its inner wall also rotate with the cylindrical screen. Under the disturbance of the rotation and the spiral push blades, the fine particles with a particle size smaller than the sieve hole in the screen pass through the sieve hole and fall into the drum screen guard chute and gather, and then flow into the fine particle storage tank from the drum screen guard chute; the coarse particles with a particle size larger than the sieve hole roll in the space of the spiral channel and move to the rear end of the screen under the push of the spiral push blades.

[0014] In some specific implementations, the spacing between each of the spiral push blades is 400-450 mm, for example, 410 mm, 420 mm, 440 mm.

[0015] In some specific embodiments, the filtrate outlet on the vacuum filter is connected to a filtrate tank for collecting the filtrate via a pipeline, and a filtrate tank pump is also provided on the pipeline; in some preferred embodiments, the filtrate tank is connected to the flushing water outlet.

[0016] In some specific embodiments, an agitator is disposed inside the fine particle storage tank to ensure that the fine particles in the storage tank are not easy to sink to the bottom.

[0017] In some specific embodiments, the fine particles and water in the fine particle storage tank are transported to the vacuum filter through the discharge port by a pump for dehydration. Specifically, the screening and dehydration system also includes a fine particle storage hopper for receiving the fine particle residue obtained by filtration of the vacuum filter.

[0018] In the screening and dehydration system provided by the present invention, the drying unit includes a hot air furnace and a blower arranged at the tail of the hot air furnace, a hot air duct is arranged inside the hot air furnace, one end of the hot air duct is connected to the air outlet of the blower, and a hot air outlet is opened at the other end of the hot air duct, and the hot air outlet is connected to the discharge port of the cylindrical screen, so that hot air is sent into the interior of the cylindrical screen to remove moisture on the outer surface of large particles of coarse slag in the screen.

[0019] In some specific embodiments, the screening and dehydration system further includes a dust removal system, which includes a cyclone separator, a bag dust collector and an induced draft fan connected in sequence; the air inlet of the cyclone separator is connected to the cavity formed between the drum screen guard chute and the cylindrical screen through a pipeline, and the gas phase outlet of the cyclone separator is connected to the inlet of the bag dust collector. The gas in the cavity is drawn by the induced draft fan and discharged after passing through the cyclone separator and the bag dust collector. In some specific embodiments, the sewage at the bottom of the cyclone separator can also be returned to the vacuum filter for filtration.

[0020] In a second aspect, the present invention provides a screening and dehydration process for coal gasification coarse slag, using the above-mentioned screening and dehydration system, the screening and dehydration process comprises the following steps:

[0021] (1) Coal gasification slag is washed and screened to obtain fine particles and coarse particles;

[0022] (2) The coarse particles are dried to obtain coarse particle slag;

[0023] (3) Dehydrating the fine particles by vacuum filtration to obtain fine particle residue and filtrate.

[0024] In a specific embodiment of the process of the present invention, the drying process in step (2) is carried out at 600-900° C. In some preferred embodiments, the hot air volume for the drying process is 500-700 m 3 / h, for example, 550m 3 / h,600m 3 / h,650m 3 / h.

[0025] The above technical solution has the following technical effects:

[0026] The present invention provides a screening and dehydration system by utilizing the different moisture contents and types of different particle sizes of coarse slag from coal gasification, that is, the moisture content in the coarse particles is mainly concentrated on the outer surface, and the moisture content in the fine particles is distributed on the outer surface and internal pores. A differentiated screening process is performed on particles with different moisture contents, thereby improving the dehydration effect. At the same time, the waste water from the screening process can be recycled, thereby reducing pollutant emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A specific implementation of the screening and dehydration system provided by the present invention;

[0028] Figure 2 for Figure 1 Schematic diagram of the structure of the medium cylindrical screen;

[0029] Among them, 1. coarse slag storage hopper, 2. drum screen guard chute, 3. fine particle storage tank, 4. vacuum filter, 5. coarse particle storage tank, 6. drum screen, 7. rotating shaft, 8. spiral push blade, 9. sieve hole, 10. filtrate tank, 11. filtrate tank pump, 12. agitator, 13. hot air furnace, 14. blower, 15. fine particle storage hopper, 16. cyclone separator, 17. bag dust collector, 18. induced draft fan, 19. cylindrical screen. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0031] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0032] The screening and dehydration system used in the following embodiments of the present invention is as follows: Figure 1 As shown, the system includes:

[0033] The coarse slag storage hopper 1 is used to provide the coal gasification coarse slag raw material to the drum screen 6;

[0034] The drum screen 6 is used to receive the gasification coarse slag from the coarse slag storage hopper 1 and screen it to obtain coarse particles and fine particles; the drum screen 6 includes a rotating shaft 7, a cylindrical screen 19, a drum screen shield chute 2, and a feed port, a discharge port and a flushing water port provided on the cylindrical screen 19 in order from the inside to the outside; wherein the rotating shaft 7 passes through the axis of the cylindrical screen 19 so that the cylindrical screen 19 rotates around the rotating shaft 7, and the drum screen shield chute 2 is sleeved on the outside of the cylindrical screen 19. The feed port on the cylindrical screen 19 is connected to the outlet of the coarse slag storage hopper 1, the discharge port is connected to the coarse particle storage tank 5, and the drum screen shield chute 2 is connected to the fine particle storage tank 3.

[0035] The coarse particle storage tank 5 is used to receive the coarse particle slag inside the cylindrical screen 19;

[0036] Fine particle storage tank 3: used to receive the material in the drum screen guard chute 2, and the discharge port of the fine particle storage tank 3 is connected to the inlet of the vacuum filter 4;

[0037] The vacuum filter 4 is used to vacuum filter the material in the fine particle storage tank 3 to obtain a filtrate and fine particle residue;

[0038] The drying unit is connected to the discharge port of the cylindrical screen 19 to provide hot air to the inside of the cylindrical screen 19 .

[0039] like Figure 2 As shown, the inner wall of the cylindrical screen 19 is also provided with a spiral push blade 8, and the cavity between the spiral push blade 8, the rotating shaft 7 and the cylindrical screen 19 forms a spiral channel; the cylindrical screen 19 is provided with a sieve hole 9 of 1 to 1.5 mm. In order to improve the screening efficiency, the surface of the cylindrical screen 19 can be provided with as many sieve holes 9 as possible, and the sieve holes 9 make the spiral channel connected with the drum screen guard chute 2. In the specific screening process, the gasification coarse slag is roughly divided into coarse particles larger than the sieve hole diameter and fine particles smaller than the sieve hole diameter after passing through the cylindrical screen 19; specifically, the fine particles smaller than the particle size of the sieve hole 9 and the flushing water leak out of the cylindrical screen 19 through the sieve hole 9, fall into the drum screen guard chute 2, gather and collect in the fine particle storage tank 3, while the coarse particles larger than the particle size of the sieve hole 9 are pushed backward in the spiral channel, and finally the coarse particles are subjected to hot air drying in the second half of the cylindrical screen 19 and discharged from the discharge port.

[0040] In some specific implementations, the spacing between each spiral push blade 8 is 400-450 mm, for example, 420 mm, 440 mm.

[0041] In some specific embodiments, the filtrate outlet on the vacuum filter 4 is connected to a filtrate tank 10 for collecting the filtrate through a pipeline, and a filtrate tank pump 11 is also provided on the pipeline; in some preferred embodiments, the filtrate tank 10 is connected to a flushing water outlet provided on the cylindrical screen 19, so that the filtrate can be recycled as flushing water, and excess water is regularly discharged into the gasification system.

[0042] In some specific embodiments, a stirrer 12 is disposed inside the fine particle storage tank 3 to ensure that the slag and water are mixed without precipitation. The fine particles and water in the fine particle storage tank 3 are transported to the vacuum filter 4 through a pump.

[0043] The drying unit in the screening and dehydration system provided by the present invention comprises a hot air stove 13 and a blower 14 connected to the rear end of the hot air stove 13; specifically, a hot air duct is arranged inside the hot air stove 13, one end of the hot air duct is connected to the air outlet of the blower 14, and a hot air outlet is provided at the other end of the hot air duct, and the hot air outlet is connected to the discharge port of the cylindrical screen 19 to send hot air into the inside of the cylindrical screen 19. In the specific screening and dehydration process, the coarse particles in the cylindrical screen 19 are dried with hot air to remove the moisture on the outer surface, and then enter the coarse particle storage tank 5 through the discharge port on the cylindrical screen 19.

[0044] In some specific embodiments, the screening and dehydration system further includes a fine particle storage hopper 15 for collecting the fine particle slag obtained by filtration by the vacuum filter 4, and then transporting the fine particle slag out of the screening system by a slag truck.

[0045] In some specific embodiments, the screening and dehydration system further includes a dust removal system, which includes a cyclone separator 16, a bag dust collector 17 and an induced draft fan 18 connected in sequence; specifically, the air inlet of the cyclone separator 16 is connected to the cavity formed between the drum screen guard chute 2 and the cylindrical screen 19 through a pipeline, and the gas phase outlet of the cyclone separator 16 is connected to the inlet of the bag dust collector 17. The gas in the cavity is drawn by the induced draft fan 18 and discharged after passing through the cyclone separator 16 and the bag dust collector 17. In some specific embodiments, the sewage at the bottom of the cyclone separator 16 enters the vacuum filter 4.

[0046] Example 1

[0047] The above dehydration and screening system is used to screen the gasification coarse slag (the coarse slag obtained from the liquid slag discharged from the gasifier under high temperature conditions and entering the slag pool for cooling, with a moisture content of 55%):

[0048] (1) The gasification slag enters the screening and dehydration system from the slag storage hopper, and is washed and screened by the flushing water in the cylindrical screen to obtain fine particles and coarse particles;

[0049] (2) The coarse particles are dried in the drying unit to obtain coarse particle slag. The heating temperature of the hot air furnace is 900°C and the hot air volume is 700m 3 / h;

[0050] (3) The fine particles are vacuum filtered and dehydrated in a vacuum filter to obtain fine particle residue and filtrate.

[0051] After testing, the moisture content of coarse-grained slag is 20%, and the moisture content of fine-grained slag is 50%. According to the proportion of the two types of particles (coarse particles with a particle size greater than 1 mm account for 80%, and fine particles with a particle size less than 1 mm account for 20%), the overall moisture content of the coarse slag is 26% after screening and dehydration, which is a significant decrease from the original moisture content in the coarse slag.

[0052] Example 2

[0053] The above dehydration and screening system is used to screen the gasification coarse slag (the coarse slag obtained from the liquid slag discharged from the gasifier under high temperature conditions and entering the slag pool for cooling, with a moisture content of 55%):

[0054] (1) The gasification slag enters the screening and dehydration system from the slag storage hopper, and is washed and screened by the flushing water in the cylindrical screen to obtain fine particles and coarse particles;

[0055] (2) The coarse particles are dried in the drying unit to obtain coarse particle slag. The heating temperature of the hot air furnace is 600°C and the hot air volume is 700m 3 / h;

[0056] (3) The fine particles are vacuum filtered and dehydrated in a vacuum filter to obtain fine particle residue and filtrate.

[0057] After testing, the moisture content of coarse-grained slag was 24%, and the moisture content of fine-grained slag was 50%. According to the proportion of the two types of particles (coarse particles with a particle size greater than 1 mm accounted for 80%, and fine particles with a particle size less than 1 mm accounted for 20%), after screening and dehydration, the overall moisture content of the coarse slag was 30%, which was significantly lower than the original moisture content in the coarse slag.

[0058] Example 3

[0059] The above dehydration and screening system is used to screen the gasification coarse slag (the coarse slag obtained from the liquid slag discharged from the gasifier under high temperature conditions and entering the slag pool for cooling, with a moisture content of 55%):

[0060] (1) The gasification slag enters the screening and dehydration system from the slag storage hopper, and is washed and screened by the flushing water in the cylindrical screen to obtain fine particles and coarse particles;

[0061] (2) The coarse particles are dried in the drying unit to obtain coarse particle slag. The heating temperature of the hot air furnace is 900°C and the hot air volume is 500m 3 / h;

[0062] (3) The fine particles are vacuum filtered and dehydrated in a vacuum filter to obtain fine particle residue and filtrate.

[0063] After testing, the moisture content of coarse-grained slag was 26%, and the moisture content of fine-grained slag was 50%. According to the proportion of the two types of particles (coarse particles with a particle size greater than 1 mm accounted for 80%, and fine particles with a particle size less than 1 mm accounted for 20%), the overall moisture content of the coarse slag was 31% after screening and dehydration, which was a significant decrease from the original moisture content in the coarse slag.

[0064] Example 4

[0065] The above dehydration and screening system is used to screen the gasification coarse slag (the coarse slag obtained from the liquid slag discharged from the gasifier under high temperature conditions and entering the slag pool for cooling, with a moisture content of 55%):

[0066] (1) The gasification slag enters the screening and dehydration system from the slag storage hopper, and is washed and screened by the flushing water in the cylindrical screen to obtain fine particles and coarse particles;

[0067] (2) The coarse particles are dried in the drying unit to obtain coarse particle slag. The heating temperature of the hot air furnace is 600°C and the hot air volume is 500m 3 / h;

[0068] (3) The fine particles are vacuum filtered and dehydrated in a vacuum filter to obtain fine particle slag and filtrate. After testing, the moisture content of the coarse particle slag is 28%, and the moisture content of the fine particle slag is 50%. According to the proportion of the two types of particles (coarse particles with a particle size greater than 1 mm account for 80%, and fine particles with a particle size less than 1 mm account for 20%), the overall moisture content of the coarse slag after screening and dehydration is 32%, which is significantly lower than the original moisture content of the coarse slag.

[0069] Comparative Example 1

[0070] The above dehydration and screening system is used to screen the gasification coarse slag (the coarse slag obtained from the liquid slag discharged from the gasifier under high temperature conditions and entering the slag pool for cooling, with a moisture content of 55%):

[0071] (1) Coal gasification coarse slag is added to the screening and dehydration system from the coarse slag storage hopper, and is washed and screened by the flushing water in the cylindrical screen to obtain fine particles and coarse particles;

[0072] (2) The hot air furnace of the drying unit is not turned on and the coarse particles are not dried;

[0073] (3) The fine particles are vacuum filtered and dehydrated in a vacuum filter to obtain fine particle residue and filtrate.

[0074] After testing, the moisture content of coarse-grained slag is 40%, and the moisture content of fine-grained slag is 50%. According to the proportion of the two types of particles (coarse particles with a particle size greater than 1 mm account for 80%, and fine particles with a particle size less than 1 mm account for 20%), the overall moisture content of the coarse slag is 42% after screening and dehydration, which is lower than the original moisture content of the coarse slag.

[0075] Comparative Example 2

[0076] The above dehydration and screening system is used to screen the gasification coarse slag (the coarse slag obtained from the liquid slag discharged from the gasifier under high temperature conditions and entering the slag pool for cooling, with a moisture content of 55%):

[0077] (1) Coal gasification coarse slag is added to the screening and dehydration system from the coarse slag storage hopper, and is washed and screened by the flushing water in the cylindrical screen to obtain fine particles and coarse particles;

[0078] (2) The coarse particles are dried in the drying unit to obtain coarse particle slag. The heating temperature of the hot air furnace is 600-900°C and the air volume is 200-400m 3 / h;

[0079] (3) The fine particles are vacuum filtered and dehydrated in a vacuum filter 4 to obtain fine particle residue and filtrate.

[0080] After testing, the moisture content of coarse-grained slag is 30%, and the moisture content of fine-grained slag is 50%. According to the proportion of the two types of particles (coarse particles with a particle size greater than 1 mm account for 80%, and fine particles with a particle size less than 1 mm account for 20%), the overall moisture content of the coarse slag is 34% after screening and dehydration, which is lower than the original moisture content of the coarse slag (55%).

[0081] Comparative Example 3

[0082] The vibrating screen introduced in the document "Application of Vibrating Screen in Coal Gasification Slag Dehydration Technology" by Gao Pengcheng and Li Gang is used to dehydrate coal gasification slag (the slag obtained from liquid slag discharged from the gas furnace under high temperature conditions and cooled in the slag pool, with a moisture content of 55%). The vibrating screen is dehydrated by the principle of destroying the surface water tension of the particles by the exciting force. The vibrating screen consists of a drive motor, a vibrator, a box, a screen plate, a shock absorber, a water collection tank and other components (see the specific structure in the article). Figure 2 shown).

[0083] Under the action of the exciting force, the box and the screen plate make reciprocating linear motion together, and the material is thrown up and jumps forward on the screen plate to make linear motion. Under the action of the exciting force, the tension of water on the surface of the coal gasification slag is changed, and the water and the coal gasification slag are separated from each other. The water flows down through the pores of the screen plate into the water collecting tank for recycling, and the slag continues to move forward until the water is removed. The dried slag enters the discharge trough and is loaded on the conveyor belt.

[0084] The above-mentioned vibration screen is used to dehydrate the crude slag from coal gasification. The moisture content of the crude slag after dehydration can only be reduced to about 40%, but the removed water still contains fine particles and has not been processed.

[0085] Comparative Example 4

[0086] The vacuum ceramic filter provided by CN221309829U (name: A vacuum degree adjustment system for vacuum filtration and dehydration of gasification coarse slag) is used to dehydrate the gasification coarse slag (the coarse slag obtained from the liquid slag discharged from the gas furnace under high temperature conditions and cooled in the slag pool, with a moisture content of 55%). The vacuum ceramic filter performs solid-liquid separation based on the principle of capillary action, and has the advantages of high filtration efficiency, low production cost, energy saving and consumption reduction, clean and environmental protection, etc.

[0087] The ceramic filter is mainly composed of the slag bin body, vacuum piping system, ash discharge system (discharge valve and vibrator), backwash piping system, and frame. The ceramic filter plate is the core component of the ceramic filter. It is a new type of porous functional ceramic material. It is covered with criss-crossing and interconnected capillary pores (pore size of about 1.5μm). Due to the capillary action, after the ceramic filter plate contacts the slurry to be filtered, the liquid automatically enters the microporous channel without external force, and the solid is blocked on the surface of the filter plate.

[0088] The gasification slag is dehydrated by using a vacuum ceramic filter. Since the gaps between the coarse particles are large, the dehydration effect is better near the ceramic filter plate, but the dehydration effect is poor away from the ceramic filter plate. The moisture content of the slag can only be reduced to about 40%.

Claims

1. A screening and dehydration system for coal gasification coarse slag, characterized in that: The screening and dehydration system comprises: A coarse slag storage hopper is used to provide the coal gasification coarse slag to the drum screen; A drum screen is used to receive and screen the coal gasification coarse slag to obtain coarse particles and fine particles; the drum screen comprises, from the inside to the outside, a rotating shaft, a cylindrical screen, a drum screen cover chute, and a feed port, a discharge port, and a flushing water port provided on the cylindrical screen; wherein the rotating shaft passes through the axis of the cylindrical screen so that the cylindrical screen rotates around the rotating shaft, the drum screen cover chute is sleeved on the outside of the cylindrical screen, the feed port is communicated with the outlet of the coarse slag storage hopper, the discharge port is communicated with the coarse particle storage tank, and the drum screen cover chute is communicated with the fine particle storage tank; A coarse particle storage tank, used for receiving the coarse particle slag inside the cylindrical screen; Fine particle storage tank: used to receive the material in the drum screen guard chute, and the discharge port of the fine particle storage tank is connected to the inlet of the vacuum filter; A vacuum filter, used for vacuum filtering the material in the fine particle storage tank to obtain a filtrate and fine particle residue; A drying unit is connected to the discharge port on the cylindrical screen to provide hot air to the interior of the cylindrical screen.

2. The screening and dehydration system according to claim 1, characterized in that: The inner wall of the cylindrical screen is also provided with a spiral push blade, and the cavity between the spiral push blade, the rotating shaft and the cylindrical screen forms a spiral channel; The cylindrical screen is provided with screen holes of 1 to 1.5 mm, so that the spiral channel is connected with the drum screen guard chute.

3. The screening and dehydration system according to claim 2, characterized in that: The distance between each of the spiral pushing blades is 400-450 mm.

4. The screening and dehydration system according to claim 3, characterized in that: The filtrate outlet on the vacuum filter is connected to a filtrate tank for collecting the filtrate through a pipeline, and a filtrate tank pump is also provided on the pipeline; Preferably, the filtrate tank is connected to the flushing water outlet.

5. The screening and dehydration system according to claim 4, characterized in that: The fine particle storage tank is provided with an agitator inside.

6. The screening and dehydration system according to any one of claims 1 to 5, characterized in that: The drying unit includes a hot air furnace and a blower arranged at the rear of the hot air furnace. A hot air duct is arranged inside the hot air furnace. One end of the hot air duct is connected to the air outlet of the blower. A hot air outlet is opened at the other end of the hot air duct. The hot air outlet is connected to the discharge port of the cylindrical screen to supply hot air into the interior of the cylindrical screen.

7. The screening and dehydration system according to claim 6, characterized in that: The screening and dehydration system also includes a fine particle storage hopper for receiving fine particle residues obtained by filtration by the vacuum filter.

8. The screening and dehydration system according to claim 7, characterized in that: The screening and dehydration system also includes a dust removal system, which includes a cyclone separator, a bag dust collector and an induced draft fan connected in sequence; The air inlet of the cyclone separator is connected to the cavity formed between the drum screen guard chute and the cylindrical screen through a pipeline, and the gas phase outlet of the cyclone separator is connected to the inlet of the bag filter.

9. A screening and dehydration process for coal gasification coarse slag, characterized in that: Utilizing the screening and dehydration system according to any one of claims 1 to 8, the screening and dehydration process comprises the following steps: (1) Coal gasification slag is washed and screened to obtain fine particles and coarse particles; (2) The coarse particles are dried to obtain coarse particle slag; (3) Dehydrating the fine particles by vacuum filtration to obtain fine particle residue and filtrate.

10. The screening and dehydration process according to claim 9, characterized in that: In step (2), the drying process is performed at 600 to 900° C.; Preferably, the hot air volume for the drying process is 500-700m 3 / h.

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