Coal gasification black water treatment system capable of recycling waste heat for power generation

Abstract

The utility model discloses a coal gasification black water treatment system capable of recycling waste heat for power generation. The coal gasification black water treatment system comprises a multi-stage flash evaporation unit, a multi-stage waste heat power generation unit, a black water clarifying and fine slag filtering unit and a grey water degassing unit, the multi-stage flash evaporation unit comprises a three-stage flash evaporator, the multi-stage waste heat power generation unit comprises a multi-stage generator set and a multi-stage medium heater, the black water clarifying and fine slag filtering unit comprises a concentration cyclone, the bottom of the concentration cyclone is connected with a filter, an upper outlet of the concentration cyclone is connected with an ash water tank, and the ash water degassing unit comprises a gas remover connected with the medium heater. According to the coal gasification black water treatment system disclosed by the utility model, by arranging the multi-stage flash evaporation unit and the multi-stage waste heat power generation unit, waste heat carried in coal gasification black water is subjected to graded conversion and utilization, and low-grade steam which is a black water flash evaporation byproduct is used for generating power, so that the waste heat is recycled, the energy utilization efficiency of the system is improved, and the energy consumption of the system is reduced. The purposes of energy conservation and consumption reduction of the coal gasification process are achieved, and production cost is saved.

Description

Technical Field

[0001] The utility model relates to the technical field of energy chemical industry and energy conservation, and in particular to a coal gasification black water treatment system with waste heat recoverable for power generation. Background Art

[0002] Coal gasification technology realizes efficient and clean utilization of coal and is the core technology in the field of modern coal chemical industry. Among them, entrained-bed gasification technology has been widely used in industry due to its high gasification temperature, wide range of coal types and high carbon conversion rate. The entrained-bed gasification process mainly includes three parts: raw material preparation, gasification and gasification black water treatment. The black water produced by the entrained-bed gasification process has a high temperature (generally 200℃~250℃) and a large flow rate. The traditional gasification black water treatment system generally treats it through multi-stage flash evaporation heat exchange. The amount of flash steam generated is large and cannot be fully utilized, resulting in a waste of low-temperature waste heat. At the same time, a large amount of circulating water is required to cool it. With the trend of energy conservation and consumption reduction in the energy and chemical industry and environmental protection requirements, reducing the production energy consumption of coal gasification technology and improving the energy utilization rate of the system are issues that need to be urgently addressed. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a coal gasification black water treatment system with waste heat recovery for power generation in view of the deficiencies of the above-mentioned prior art. The system is provided with a multi-stage flash evaporation unit and a multi-stage waste heat power generation unit to perform graded conversion and utilization of waste heat carried in coal gasification black water, and to generate electricity using low-grade steam produced as a byproduct of black water flash evaporation, thereby realizing the recovery and utilization of waste heat, improving the energy utilization efficiency of the system, and solving the problem of efficient utilization of waste heat from coal gasification black water.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is: a coal gasification black water treatment system with waste heat recovery for power generation, characterized in that it includes a multi-stage flash evaporation unit, a multi-stage waste heat power generation unit, a black water clarification and fine residue filtration unit and a gray water degassing unit;

[0005] The multi-stage flash unit comprises a first-stage high-pressure flash evaporator, a second-stage low-pressure flash evaporator and a third-stage vacuum flash evaporator connected in sequence, the inlet of the first-stage high-pressure flash evaporator is connected to the gasifier and the liquid outlet end of the washing tower, and the top outlet of the first-stage high-pressure flash evaporator is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the inlet of the second-stage low-pressure flash evaporator, the top outlet of the second-stage low-pressure flash evaporator is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the inlet of the third-stage vacuum flash evaporator, the top outlet of the third-stage vacuum flash evaporator is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the black water clarification and fine slag filtration unit;

[0006] The multi-stage waste heat power generation unit comprises a multi-stage generator set consisting of a primary generator set, a secondary generator set and a tertiary generator set, and a multi-stage medium heater consisting of a primary medium heater, a secondary medium heater and a tertiary medium heater, wherein the inlet of the primary generator set is connected to the top outlet of the primary high-pressure flash evaporator, and the outlet is connected to the first inlet of the primary medium heater, the inlet of the secondary generator set is connected to the top outlet of the secondary low-pressure flash evaporator, and the outlet is connected to the first inlet of the secondary medium heater, the first inlet of the tertiary medium heater is connected to the top outlet of the tertiary vacuum flash evaporator, and the primary medium heater, the secondary medium heater and the tertiary medium heater are connected to the top outlet of the tertiary vacuum flash evaporator. The second inlet of the heater is connected to the medium collection tank through a pipeline, and a medium circulation pump is provided on the pipeline. The first outlets of the first-stage medium heater and the second-stage medium heater are connected to the ash water degassing unit, respectively. The first outlet of the tertiary medium heater is connected to the gas-water separator. The bottom of the gas-water separator is connected to the ash water degassing unit through a pipeline, and a condensate pump is provided on the pipeline. The top outlet of the gas-water separator is connected to the negative pressure extractor. The second outlets of the first-stage medium heater, the second-stage medium heater and the tertiary medium heater are connected to the inlet of the tertiary generator set, respectively. The outlet of the tertiary generator set is connected to the medium cooler, and the medium cooler is connected to the medium collection tank.

[0007] The black water clarification and fine residue filtering unit comprises a concentrating cyclone, the inlet of the concentrating cyclone is connected to the bottom outlet of the three-stage vacuum flash evaporator through a pipeline, and a cyclone feed pump is provided on the pipeline, the bottom outlet of the concentrating cyclone is connected to the inlet of the filter through a pipeline, and a filter feed pump is provided on the pipeline, the first outlet of the filter is connected to the concentrating cyclone, and the second outlet is used to discharge fine residues, the upper outlet of the concentrating cyclone is connected to the gray water tank, and a gray water pump is provided on the outlet pipeline of the gray water tank;

[0008] The grey water degassing unit comprises a gas remover, the inlet of which is respectively connected to the first outlet of the primary medium heater, the second medium heater and the bottom of the gas-water separator, and a degassing water pump is arranged on the bottom outlet pipe of the gas remover.

[0009] The above-mentioned coal gasification black water treatment system with waste heat recovery for power generation is characterized in that the three-stage vacuum flash evaporator is connected to a vacuum pump.

[0010] The above-mentioned coal gasification black water treatment system with waste heat recovery for power generation is characterized in that the first-stage generator set, the second-stage generator set and the third-stage generator set all include an expander and a generator, and the expander is a screw, scroll or piston expander.

[0011] The above-mentioned coal gasification black water treatment system with waste heat recovery for power generation is characterized in that the medium cooler is a water-cooled or air-cooled condensing device.

[0012] In the above-mentioned coal gasification black water treatment system with waste heat recovery for power generation, the filter is a vacuum belt filter or a centrifugal filter.

[0013] Compared with the prior art, the utility model has the following advantages:

[0014] 1. In the coal gasification black water treatment system of the utility model, multi-stage flash evaporation units and multi-stage waste heat power generation units are arranged to grade the waste heat carried in the coal gasification black water for conversion and utilization, and the low-grade steam produced as a by-product of the black water flash evaporation is used to generate electricity, thereby realizing the recovery and utilization of waste heat, improving the energy utilization efficiency of the system, and achieving the purpose of energy saving and consumption reduction in the coal gasification process.

[0015] 2. In the multi-stage waste heat power generation unit of the utility model, a first-stage generator set and a second-stage generator set are arranged as black water generator sets, and low-temperature flash steam obtained by flash evaporation of black water is used to directly generate electricity. A third-stage generator set is arranged as a medium generator set, and heat exchange gasification of circulating medium is used to generate electricity, so that the heat energy carried in the coal gasification black water is fully converted into electrical energy, further improving the system's recovery rate of waste heat.

[0016] 3. The multi-stage waste heat power generation unit of the utility model adopts a multi-stage medium heater instead of a traditional heat exchanger, and adopts a circulating medium instead of circulating cooling water, which reduces the demand for equipment and reduces the amount of circulating cooling water, thereby effectively reducing system energy consumption and saving production costs.

[0017] 4. The coal gasification black water treatment system of the utility model converts the waste heat in the black water into electrical energy. The electricity generated not only meets the operation requirements of the coal gasification black water treatment system, but can also be supplied externally, reducing the cost of increasing electricity capacity.

[0018] 5. The utility model recycles various components in coal gasification black water by setting up black water clarification and fine residue filtration units, and further recycles residual heat energy in the cooled flash steam by setting up gray water degassing units for degassing and heat exchange, thereby improving the efficiency of waste heat utilization.

[0019] The technical solution of the utility model is further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The utility model is a schematic diagram of the structure of the coal gasification black water treatment system with waste heat recovery for power generation.

[0021] Description of reference numerals:

[0022] 1—first-stage high-pressure flash evaporator; 2—second-stage low-pressure flash evaporator; 3—third-stage vacuum flash evaporator;

[0023] 4—first-level generator set; 5—second-level generator set; 6—third-level generator set;

[0024] 7—first-stage medium heater; 8—second-stage medium heater; 9—third-stage medium heater;

[0025] 10—gas-water separator; 11—negative pressure extractor; 12—medium cooler;

[0026] 13—medium collection tank; 14—medium circulation pump; 15—gas remover;

[0027] 16—degassing water pump; 17—condensate pump; 18—feed pump;

[0028] 19—concentrating cyclone; 20—filter feed pump; 21—filter;

[0029] 22—ash water tank; 23—ash water pump. DETAILED DESCRIPTION

[0030] Example 1

[0031] like Figure 1 As shown, the coal gasification black water treatment system with waste heat recovery for power generation in this embodiment includes a multi-stage flash evaporation unit, a multi-stage waste heat power generation unit, a black water clarification and fine slag filtration unit and a gray water degassing unit;

[0032] The multi-stage flash unit comprises a first-stage high-pressure flash evaporator 1, a second-stage low-pressure flash evaporator 2 and a third-stage vacuum flash evaporator 3 which are connected in sequence, the inlet of the first-stage high-pressure flash evaporator 1 is connected to the gasifier and the liquid outlet end of the washing tower, and the top outlet of the first-stage high-pressure flash evaporator 1 is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the inlet of the second-stage low-pressure flash evaporator 2, the top outlet of the second-stage low-pressure flash evaporator 2 is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the inlet of the third-stage vacuum flash evaporator 3, the top outlet of the third-stage vacuum flash evaporator 3 is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the black water clarification and fine slag filtration unit;

[0033] The multi-stage waste heat power generation unit comprises a multi-stage generator set consisting of a primary generator set 4, a secondary generator set 5 and a tertiary generator set 6, and a multi-stage medium heater consisting of a primary medium heater 7, a secondary medium heater 8 and a tertiary medium heater 9. The inlet of the primary generator set 4 is connected to the top outlet of the primary high-pressure flash evaporator 1, and the outlet is connected to the first inlet of the primary medium heater 7. The inlet of the secondary generator set 5 is connected to the top outlet of the secondary low-pressure flash evaporator 2, and the outlet is connected to the first inlet of the secondary medium heater 8. The first inlet of the tertiary medium heater 9 is connected to the top outlet of the tertiary vacuum flash evaporator 3. The second inlet of the primary medium heater 7, the secondary medium heater 8 and the tertiary medium heater 9 are connected to the top outlet of the tertiary vacuum flash evaporator 3. The inlets are respectively connected to the medium collecting tank 13 through pipelines, and a medium circulation pump 14 is provided on the pipelines. The first outlets of the primary medium heater 7 and the secondary medium heater 8 are respectively connected to the ash water degassing unit. The first outlet of the tertiary medium heater 9 is connected to the gas-water separator 10. The bottom of the gas-water separator 10 is connected to the ash water degassing unit through a pipeline, and a condensate pump 17 is provided on the pipeline. The top outlet of the gas-water separator 10 is connected to the negative pressure extractor 11. The second outlets of the primary medium heater 7, the secondary medium heater 8 and the tertiary medium heater 9 are respectively connected to the inlet of the tertiary generator set 6. The outlet of the tertiary generator set 6 is connected to the medium cooler 12, and the medium cooler 12 is connected to the medium collecting tank 13.

[0034] The black water clarification and fine residue filtering unit comprises a concentrating cyclone 19, the inlet of the concentrating cyclone 19 is connected to the bottom outlet of the three-stage vacuum flash evaporator 3 through a pipeline, and a cyclone feed pump 18 is provided on the pipeline, the bottom outlet of the concentrating cyclone 19 is connected to the inlet of a filter 21 through a pipeline, and a filter feed pump 20 is provided on the pipeline, the first outlet of the filter 21 is connected to the concentrating cyclone 19, and the second outlet is used to discharge fine residues, the upper outlet of the concentrating cyclone 19 is connected to the gray water tank 22, and a gray water pump 23 is provided on the outlet pipeline of the gray water tank 22;

[0035] The ash water degassing unit includes a gas remover 15, the inlet of which is respectively connected to the first outlet of the primary medium heater 7, the second medium heater 8 and the bottom of the gas-water separator 10, and a degassing water pump 16 is provided on the bottom outlet pipe of the gas remover 15.

[0036] In the coal gasification black water treatment system of the present embodiment, a multi-stage flash evaporation unit is provided to perform graded flash evaporation on the coal gasification black water, including the gasification black water and the washing black water from the gasifier and the washing tower; a multi-stage waste heat power generation unit is provided to generate electricity from the flash steam obtained by flash evaporation; a black water clarification and fine residue filtration unit is provided to separate, settle and utilize the concentrated black water obtained by flash evaporation; and a gray water degassing unit is provided to degas and exchange heat between the cooled flash steam and the condensate generated during the flash steam utilization process.

[0037] Specifically, in the multi-stage flash unit of the present embodiment, a first-stage high-pressure flash evaporator 1, a second-stage low-pressure flash evaporator 2 and a third-stage vacuum flash evaporator 3 are arranged in sequence, and the inlet of the first-stage high-pressure flash evaporator 1 is connected to the liquid outlet end of the gasifier and the washing tower, the top outlet is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the inlet of the second-stage low-pressure flash evaporator 2. The first-stage high-pressure flash evaporator 1 is used to perform high-pressure flash evaporation on the gasification black water discharged from the gasifier and the washing black water discharged from the washing tower to obtain first-stage flash steam and first-stage concentrated black water, and the first-stage flash steam is sent to the multi-stage waste heat power generation unit through the top outlet for subsequent use in power generation, and the first-stage concentrated black water is sent to the second-stage low-pressure flash evaporator 2 for low-pressure flash evaporation , obtain secondary flash steam and secondary concentrated black water, and connect the top outlet of the secondary low-pressure flash evaporator 2 with the multi-stage waste heat power generation unit, and connect the bottom outlet with the inlet of the tertiary vacuum flash evaporator 3, so as to send the secondary flash steam to the multi-stage waste heat power generation unit for subsequent power generation, and send the secondary concentrated black water to the tertiary vacuum flash evaporator 3 for vacuum flash evaporation, so as to obtain tertiary flash steam and tertiary concentrated black water, and connect the top outlet of the tertiary vacuum flash evaporator 3 with the multi-stage waste heat power generation unit, and connect the bottom outlet with the black water clarification and fine residue filtration unit, so as to send the tertiary flash steam to the multi-stage waste heat power generation unit for utilization, and send the tertiary concentrated black water to the black water clarification and fine residue filtration unit for separation and sedimentation utilization. Therefore, in this embodiment, a multi-stage flash evaporation unit consisting of a high-pressure flash evaporator 1, a secondary low-pressure flash evaporator 2 and a tertiary vacuum flash evaporator 3 connected in sequence is set up to perform high-pressure, low-pressure and vacuum flash evaporation on the gasified black water and the washed black water in sequence, and the waste heat carried in each black water is converted into the form of flash steam, thereby achieving graded and sufficient conversion of the waste heat carried in the gasified black water and the washed black water.

[0038] In the multi-stage waste heat power generation unit of this embodiment, a multi-stage generator set consisting of a primary generator set 4, a secondary generator set 5 and a tertiary generator set 6 is provided to generate electricity from flash steam, and a multi-stage medium heater consisting of a primary medium heater 7, a secondary medium heater 8 and a tertiary medium heater 9 is provided to heat the medium using the waste heat in the flash steam after power generation; specifically, the inlet of the primary generator set 4 is connected to the top outlet of the primary high-pressure flash evaporator 1, and the outlet is connected to the first inlet of the primary medium heater 7, and the primary flash steam fed into the top outlet of the primary high-pressure flash evaporator 1 is used by the primary generator set 4 to generate electricity, and the generated electricity is sent to the power grid, and the power generation expansion The primary flash steam after work is sent to the primary medium heater 7 through the outlet to exchange heat with the circulating medium. The inlet of the secondary generator set 5 is connected to the top outlet of the secondary low-pressure flash evaporator 2, and the outlet is connected to the first inlet of the secondary medium heater 8. The secondary generator set 5 is used to generate electricity from the secondary flash steam sent into the secondary low-pressure flash evaporator 2, and the generated electricity is sent to the power grid. The secondary flash steam after power generation and expansion is sent to the secondary medium heater 8 through the outlet to exchange heat with the circulating medium. The first inlet of the tertiary medium heater 9 is connected to the top outlet of the tertiary vacuum flash evaporator 3, so that the tertiary flash steam generated in the tertiary vacuum flash evaporator 3 is sent to the tertiary medium Heat is exchanged with the circulating medium in the heater 9; the second inlets of the primary medium heater 7, the secondary medium heater 8 and the tertiary medium heater 9 are connected to the medium collecting tank 13 through pipelines, and a medium circulation pump 14 is provided on the pipeline. The circulating medium collected and stored in the medium collecting tank 13 is quickly transported to the primary medium heater 7, the secondary medium heater 8 and the tertiary medium heater 9 by the medium circulation pump 14, so as to ensure the smooth heat exchange of the circulating medium in each medium heater; the first outlets of the primary medium heater 7 and the secondary medium heater 8 are connected to the ash water degassing unit respectively, so as to The flash steam cooled after heat exchange with the circulating medium is sent to the ash water degassing unit to participate in degassing and heat exchange. The first outlet of the tertiary medium heater 9 is connected to the gas-water separator 10, so that the tertiary flash steam cooled after heat exchange with the circulating medium in the tertiary medium heater 9 is sent to the gas-water separator 10 for gas-liquid separation to obtain condensate and non-condensable gas. The bottom of the gas-water separator 10 is connected to the ash water degassing unit through a pipeline, and a condensate pump 17 is arranged on the pipeline. The top outlet of the gas-water separator 10 is connected to the negative pressure extractor 11, so that the condensate is sent to the ash water degassing unit to participate in degassing and heat exchange under the action of the condensate pump 17, and the non-condensable gas is discharged and vented through the negative pressure extractor 11;By setting the second outlets of the first-stage medium heater 7, the second-stage medium heater 8 and the third-stage medium heater 9 to be connected to the inlet of the third-stage generator set 6 respectively, and the outlet of the third-stage generator set 6 is connected to the medium cooler 12, so that the circulating medium gasified after heat exchange in the first-stage medium heater 7, the second-stage medium heater 8 and the third-stage medium heater 9 is sent to the third-stage generator set 6 for power generation, and the generated electricity is sent to the power grid. The circulating medium after power generation is sent to the medium cooler 12 through the outlet for cooling, and then sent to the medium collection tank 13 for collection and storage, and under the action of the medium circulation pump 14, it is quickly transported to the first-stage medium heater 7, the second-stage medium heater 8 and the third-stage medium heater 9 for recycling. Therefore, in the multi-stage waste heat power generation unit of this embodiment, by setting a multi-stage generator set and a multi-stage medium heater, the heat energy carried in the flash steam is directly converted into electrical energy in stages, and the residual heat energy is indirectly converted into electrical energy through the circulating medium, so that the waste heat carried in the coal gasification black water is fully utilized in stages. ;

[0039] Usually, the circulating medium in each medium heater is an organic medium with a critical temperature greater than 50° C. and a boiling point less than 30° C. Commonly used circulating media are n-butane, isobutane or chloropentafluoropropane.

[0040] In the black water clarification and fine residue filtering unit of the present embodiment, a concentrating cyclone 19 is provided, and the inlet of the concentrating cyclone 19 is connected to the bottom outlet of the three-stage vacuum flash evaporator 3 through a pipeline, and a cyclone feed pump 18 is provided on the pipeline. The three-stage concentrated black water in the three-stage vacuum flash evaporator 3 is fed into the concentrating cyclone 19 for separation and sedimentation to achieve clarification by the pressurization effect of the cyclone feed pump 18, so as to obtain clarified gray water and black water containing residue. The bottom outlet of the concentrating cyclone 19 is connected to the inlet of the filter 21 through a pipeline, and a filter feed pump 20 is provided on the pipeline, so that the black water containing residue is filtered out in the filter 21. The feed pump 20 is used to feed the material into the filter 21 for dehydration and filtration to obtain fine slag and black water. The first outlet of the filter 21 is connected to the concentrating cyclone 19 so that the black water returns to the concentrating cyclone 19 as supplementary water to participate in separation and sedimentation, and the fine slag is discharged through the second outlet and sent to the subsequent process for treatment. The upper outlet of the concentrating cyclone 19 is connected to the gray water tank 22, and the gray water pump 23 is provided on the outlet pipe of the gray water tank 22, so that the clarified gray water in the concentrating cyclone 19 overflows from the upper part to the gray water tank 22 for storage, and is pumped out for recycling under the action of the gray water pump 23. Therefore, in the black water clarification and fine slag filtration unit of this embodiment, the concentrated black water finally obtained by flash evaporation is treated separately after solid-liquid separation and sedimentation by providing the concentrating cyclone 19 and the filter 21, so as to realize the recycling of various components in the coal gasification black water.

[0041] In the ash water degassing unit of the present embodiment, a gas remover 15 is provided, and the inlet of the gas remover 15 is respectively connected to the first outlet of the primary medium heater 7, the second medium heater 8 and the bottom of the gas-water separator 10, so that the flash steam of each level cooled down after heat exchange with the circulating medium in the primary medium heater 7 and the second medium heater 8 enters the gas remover 15, and the condensate obtained by gas-liquid separation in the water separator 10 also enters the gas remover 15 under the action of the condensate pump 17. These three streams contact and perform degassing and heat exchange in the gas remover 15 to generate non-condensable gas and water. By providing a degassing water pump 16 on the bottom outlet pipe of the gas remover 15, the water is sent out for recycling through the degassing water pump 16, and the non-condensable gas is discharged from the top of the degassing water pump 16. Therefore, in the ash water degassing unit of the present embodiment, the gas remover 15 is provided to recycle the residual heat energy in the flash steam cooled down after power generation and heat exchange with the circulating medium, thereby further improving the waste heat utilization efficiency.

[0042] Furthermore, the three-stage vacuum flash evaporator 3 is connected with a vacuum pump to provide vacuum flash evaporation conditions for the three-stage vacuum flash evaporator 3.

[0043] Furthermore, the first-stage generator set 4, the second-stage generator set 5 and the third-stage generator set 6 all include an expander and a generator, and the expander is a screw, scroll or piston expander.

[0044] Furthermore, the medium cooler 12 is a water-cooled or air-cooled condensing device.

[0045] Furthermore, the filter 21 is a vacuum belt filter or a centrifugal filter.

[0046] The use process of the utility model coal gasification black water treatment system is:

[0047] Step 1: send the gasified black water and washed black water from the gasifier and the washing tower into the first-level high-pressure flash evaporator 1 for high-pressure flash evaporation to obtain first-level flash steam and first-level concentrated black water, and then send the first-level flash steam into the first-level generator set 4 through the top outlet to generate electricity, and the generated electricity is sent to the power grid. The first-level flash steam after power generation expansion and work is sent into the first-level medium heater 7 through the outlet to exchange heat with the circulating medium to obtain cooled first-level flash steam and gasified circulating medium;

[0048] The primary concentrated black water is sent to the secondary low-pressure flash evaporator 2 for low-pressure flash evaporation to obtain secondary flash steam and secondary concentrated black water, and then the secondary flash steam is sent to the secondary generator set 5 through the top outlet to generate electricity, and the generated electricity is sent to the power grid. The secondary flash steam after power generation expansion and work is sent to the secondary medium heater 8 through the outlet to exchange heat with the circulating medium to obtain cooled secondary flash steam and gasified circulating medium;

[0049] The secondary concentrated black water is sent to the tertiary vacuum flash evaporator 3 for vacuum flash evaporation to obtain tertiary flash steam and tertiary concentrated black water, and then the tertiary flash steam is sent to the tertiary medium heater 9 to exchange heat with the circulating medium to obtain cooled tertiary flash steam and gasified circulating medium;

[0050] Step 2: The gasified circulating medium obtained in the primary medium heater 7, the secondary medium heater 8 and the tertiary medium heater 9 is sent to the tertiary generator set 6 for power generation, and the generated electricity is sent to the power grid. The circulating medium after power generation is sent to the medium cooler 12 through the outlet for cooling, and then sent to the medium collecting tank 13 for collection and storage, and under the action of the medium circulation pump 14, it is quickly transported to the primary medium heater 7, the secondary medium heater 8 and the tertiary medium heater 9 for recycling;

[0051] Step 3: The cooled primary and secondary flash steam obtained in the primary medium heater 7 and the secondary medium heater 8 are sent to the gas stripper 15, and the cooled third-stage flash steam obtained in the third-stage medium heater 9 is sent to the gas-water separator 10 for gas-liquid separation to obtain condensate and non-condensable gas, and the condensate is sent to the gas stripper 15 by using the condensate pump 17, and degassed and heat-exchanged with the cooled primary and secondary flash steam to generate non-condensable gas and water, and the non-condensable gas is discharged from the top of the degassing water pump 16, and the water is sent out by the degassing water pump 16 for recycling;

[0052] Step 4: The tertiary concentrated black water obtained in step 1 is fed into the concentrating cyclone 19 under the pressure of the cyclone feed pump 18 to separate and settle to obtain clarified gray water and slag-containing black water. The slag-containing black water is fed into the filter 21 by the filter feed pump 20 for dehydration and filtration to obtain fine slag and black water. The black water is returned to the concentrating cyclone 19 as supplementary water to participate in separation and sedimentation, while the fine slag is discharged through the second outlet and sent to the subsequent process for treatment, and the clarified gray water is stored in the gray water tank 22 through overflow, and is pumped out for recycling by the gray water pump 23.

[0053] In actual use, an appropriate amount of flocculant is usually added during the separation and sedimentation of the three-stage concentrated black water to enhance the sedimentation effect of the slag-containing black water. The conventional amount of flocculant added is 60ppm to 80ppm.

[0054] The above is only a preferred embodiment of the utility model, and does not limit the utility model in any way. Any simple modification, change and equivalent change made to the above embodiment according to the essence of the utility model technology still falls within the protection scope of the technical solution of the utility model.

Claims

1. A coal gasification black water treatment system with waste heat recovery for power generation, characterized in that: It includes a multi-stage flash unit, a multi-stage waste heat power generation unit, a black water clarification and fine residue filtration unit and a grey water degassing unit; The multi-stage flash unit comprises a first-stage high-pressure flash evaporator (1), a second-stage low-pressure flash evaporator (2) and a third-stage vacuum flash evaporator (3) which are connected in sequence, the inlet of the first-stage high-pressure flash evaporator (1) is connected to the gasifier and the liquid outlet of the washing tower, and the top outlet of the first-stage high-pressure flash evaporator (1) is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the inlet of the second-stage low-pressure flash evaporator (2), the top outlet of the second-stage low-pressure flash evaporator (2) is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the inlet of the third-stage vacuum flash evaporator (3), the top outlet of the third-stage vacuum flash evaporator (3) is connected to the multi-stage waste heat power generation unit, and the bottom outlet is connected to the black water clarification and fine residue filtering unit; The multi-stage waste heat power generation unit comprises a multi-stage generator set consisting of a primary generator set (4), a secondary generator set (5) and a tertiary generator set (6), and a multi-stage medium heater consisting of a primary medium heater (7), a secondary medium heater (8) and a tertiary medium heater (9), wherein the inlet of the primary generator set (4) is connected to the top outlet of the primary high-pressure flash evaporator (1), and the outlet is connected to the first inlet of the primary medium heater (7), the inlet of the secondary generator set (5) is connected to the top outlet of the secondary low-pressure flash evaporator (2), and the outlet is connected to the first inlet of the secondary medium heater (8), the first inlet of the tertiary medium heater (9) is connected to the top outlet of the tertiary vacuum flash evaporator (3), and the second inlets of the primary medium heater (7), the secondary medium heater (8) and the tertiary medium heater (9) are connected to the top outlet of the tertiary vacuum flash evaporator (3). The first outlets of the first-stage medium heater (7) and the second-stage medium heater (8) are respectively connected to the medium collecting tank (13) through pipelines, and a medium circulation pump (14) is arranged on the pipeline. The first outlets of the first-stage medium heater (7) and the second-stage medium heater (8) are respectively connected to the ash water degassing unit. The first outlet of the tertiary medium heater (9) is connected to the gas-water separator (10). The bottom of the gas-water separator (10) is connected to the ash water degassing unit through a pipeline, and a condensate pump (17) is arranged on the pipeline. The top outlet of the gas-water separator (10) is connected to the negative pressure extractor (11). The second outlets of the first-stage medium heater (7), the second-stage medium heater (8) and the tertiary medium heater (9) are respectively connected to the inlet of the tertiary generator set (6). The outlet of the tertiary generator set (6) is connected to the medium cooler (12), and the medium cooler (12) is connected to the medium collecting tank (13); The black water clarification and fine residue filtering unit comprises a concentrating cyclone (19), the inlet of the concentrating cyclone (19) is connected to the bottom outlet of the three-stage vacuum flash evaporator (3) through a pipeline, and a cyclone feed pump (18) is arranged on the pipeline, the bottom outlet of the concentrating cyclone (19) is connected to the inlet of a filter (21) through a pipeline, and a filter feed pump (20) is arranged on the pipeline, the first outlet of the filter (21) is connected to the concentrating cyclone (19), and the second outlet is used to discharge fine residue, the upper outlet of the concentrating cyclone (19) is connected to the gray water tank (22), and a gray water pump (23) is arranged on the outlet pipeline of the gray water tank (22); The grey water degassing unit comprises a gas remover (15), the inlet of which is respectively connected to the first outlet of the primary medium heater (7), the second medium heater (8) and the bottom of the gas-water separator (10), and a degassing water pump (16) is provided on the bottom outlet pipeline of the gas remover (15).

2. The coal gasification black water treatment system with waste heat recovery for power generation according to claim 1 is characterized in that: The three-stage vacuum flash evaporator (3) is matched with a vacuum pump.

3. The coal gasification black water treatment system with waste heat recovery for power generation according to claim 1 is characterized in that: The first-stage generator set (4), the second-stage generator set (5) and the third-stage generator set (6) all include an expander and a generator, and the expander is a screw, scroll or piston expander.

4. The coal gasification black water treatment system with waste heat recovery for power generation according to claim 1 is characterized in that: The medium cooler (12) is a water-cooled or air-cooled condensing device.

5. The coal gasification black water treatment system with waste heat recovery for power generation according to claim 1 is characterized in that: The filter (21) is a vacuum belt filter or a centrifugal filter.

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