Pulverized coal gasification waste heat utilization system

Abstract

The invention discloses a pulverized coal gasification waste heat utilization system which is established by arranging a multi-stage efficient heat exchanger, the efficient heat exchanger comprises a plurality of vertically arranged anti-blocking tube nests, black water circulates in the anti-blocking tube nests from top to bottom, and the anti-blocking tube nests are in curved surface design; cooling water circulates outside the anti-blocking tube nests from bottom to top, and the cooling water is in contact with black water for heat exchange. According to the pulverized coal gasification waste heat utilization system, black water entering the high-pressure flash tank for flash evaporation is subjected to multi-stage heat exchange treatment, so that the utilization direction of the black water is increased, the use of 0.5 Mpa low-pressure steam in the system is reduced, the boiler load is reduced, and the waste heat utilization rate of a gasification device is increased; the water temperature of the low-pressure grey water in the deoxidization tank reaches 100 DEG C or above through heat exchange, and the problem that a large amount of grey water is emptied in conventional deoxidization is solved.

Description

Technical Field

[0001] The invention relates to the technical field of pulverized coal gasification waste heat utilization, and in particular to a pulverized coal gasification waste heat utilization system. Background Art

[0002] In modern coal gasification technology, the task of the pulverized coal preparation system of the pre-unit of pulverized coal pressurized gasification is to grind and dry the lump raw coal (particle size 100% ≤ 10mm) into micron-grade (particle size 100% ≤ 200μm, water content ≤ 5%) pulverized coal and send it to the gasifier for reaction. The main equipment of the pulverized coal preparation and transportation system includes bag filter, rotary discharge valve, fiber separator, screw conveyor, pulverized coal storage tank, pulverized coal storage tank filter, pulverized coal lock bucket, pulverized coal feeding tank and related pipelines. In order to ensure the safety and stability of the raw coal grinding and separation and pulverized coal pressurized transportation process, steam tracing is required for the relevant equipment and related pipelines. The material temperature in this process is ≥ 90℃ to ensure the stability of material transportation.

[0003] The synthesis gas produced by the reaction of pulverized coal and oxygen in the gasifier is sent to the post-system through quenching water cooling, separation, and washing. The black water (200°C, 4.0MPa) produced by quenching, separation, and washing enters the high-pressure flash tank for flash evaporation (0.6MPa, 159°C), and the black water after flash evaporation enters the low-pressure flash tank for flash evaporation (0.15MPa, 127°C). The black water after flash evaporation in the low-pressure flash tank enters the vacuum flash tank for flash evaporation (-0.04MPa, 80°C), and the black water after vacuum flash evaporation enters the sedimentation tank for sedimentation. The black water at the bottom of the sedimentation tank is filtered to produce coal sludge for takeout, and the supernatant is returned to the ash water tank.

[0004] A low-pressure ash water pump is installed at the bottom of the ash water tank. Part of it is sent to sewage treatment, and part of it is sent to the atmospheric pressure deoxygenation tank for deoxygenation. Deoxygenation is carried out using low-pressure flash steam, and the temperature is ≥100°C. The deoxygenated water after deoxygenation enters the flash steam scrubber and contacts with the high-pressure flash steam in reverse to recover heat. The temperature is about 150°C. After recovering heat, the ash water is pressurized as washing water for synthesis gas. Part of the washing water is sent to the high-pressure flash tank, and part of it is sent to the gasifier as synthesis gas quenching water. The black water after quenching enters the high-pressure flash tank to form a cycle. In the above process, the vacuum flash steam cannot be effectively utilized due to its low temperature (about 80°C), and is forced to use circulating water for cooling, resulting in a large heat loss in the system. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a pulverized coal gasification waste heat utilization system, which can achieve full cascade utilization of energy and reduce system energy consumption.

[0006] To achieve the above object, the present invention provides a high-efficiency heat exchanger, comprising a plurality of vertically arranged anti-blocking tubes, in which black water flows from top to bottom, and the anti-blocking tubes are of curved surface design; The cooling water flows from bottom to top outside the anti-blocking tube array, and the cooling water contacts and exchanges heat with the black water.

[0007] Preferably, the high-efficiency heat exchanger is made of wear-resistant and corrosion-resistant material.

[0008] Preferably, the black water outlet is arranged obliquely, and a support is provided on the higher side of the black water outlet.

[0009] Preferably, the high-efficiency heat exchanger is made of wear-resistant and corrosion-resistant material.

[0010] A pulverized coal gasification waste heat utilization system is established by arranging multiple stages of the above-mentioned high-efficiency heat exchangers, comprising: (1) The synthesis gas generated after the reaction in the gasifier enters the high-pressure flash tank for flash evaporation through quenching, separation, and washing to produce black water. The high-pressure flash tank is connected to the primary high-efficiency heat exchanger, and the primary high-efficiency heat exchanger is connected to the low-pressure flash tank 1 to flash 0.2~0.3MPa low-pressure steam; (2) The 0.2-0.3 MPa low-pressure steam generated in step (1) is transported to the pulverized coal preparation and transportation system, and the 0.2-0.3 MPa low-pressure steam is used for pulverized coal preparation and transportation heating; (3) After the black water has been heat exchanged in the primary high-efficiency heat exchanger, it passes through the low-pressure flash tank and then through the secondary high-efficiency heat exchanger to exchange heat with the low-pressure gray water from the gray water tank. The low-pressure gray water with an output temperature of ≥100°C from the secondary high-efficiency heat exchanger enters the deoxidation tank; (4) The black water output after heat exchange in the secondary high-efficiency heat exchanger is exchanged with the desalted water added to the system through the tertiary high-efficiency heat exchanger; the black water with an output temperature of ≤80°C from the tertiary high-efficiency heat exchanger is discharged into the second low-pressure flash tank; (5) The black water after the second flash evaporation in the low-pressure flash tank enters the vacuum flash tank for flash evaporation, and the black water after the vacuum flash evaporation enters the sedimentation tank for sedimentation.

[0011] Preferably, the 0.5 MPa steam input pipeline and the 0.2-0.3 MPa steam input pipeline generated by the low-pressure flash tank are connected to the pulverized coal preparation and transportation system via the same valve.

[0012] Preferably, the output end of the low-pressure flash tank 1 is also connected to the input end of the first-stage high-efficiency heat exchanger, and a circulation pump and a desalted water replenishment pipeline are arranged on the connecting pipeline between the output end of the low-pressure flash tank 1 and the input end of the first-stage high-efficiency heat exchanger.

[0013] Preferably, the black water with an output temperature of ≤80°C from the three-stage high-efficiency heat exchanger can be used as flushing water for pump seals, instrument seals or for user heating.

[0014] The pulverized coal gasification waste heat utilization system of the present invention has the following beneficial effects: (1) Reduce the use of 0.5MPa low-pressure steam in the system, reduce boiler load, and improve the utilization rate of waste heat in the gasification device, which can save 0.5MPa steam ≥20t / h; (2) Keep the original design process to facilitate regular inspection of the operation of the high-efficiency heat exchanger; (3) The water temperature of low-pressure ash water in the deaeration tank is raised to above 100°C through heat exchange, reducing the large amount of venting problem existing in conventional deaeration; (4) The low-pressure steam by-product system is equipped with a desalted water replenishment pipeline and two circulating water pumps (one on and one standby to ensure that the standby pump can start automatically when the operating pump fails) to ensure stable steam generation.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a high-efficiency heat exchanger of the present invention; Figure 2 It is a schematic diagram of the overall structure of the pulverized coal gasification waste heat utilization system of the present invention.

[0017] Reference numerals 1. Pulverized coal preparation and transportation system; 2. Gasifier; 3. High-pressure flash tank; 4. Primary high-efficiency heat exchanger; 5. Low-pressure flash tank one; 6. Secondary high-efficiency heat exchanger; 7. Ash water tank; 8. Deoxidation tank; 9. Third-stage high-efficiency heat exchanger; 10. Low-pressure flash tank two; 11. Vacuum flash tank; 12. Sedimentation tank; 13. Circulation pump; 14. Desalted water supply pipeline; 15. Black water inlet; 16. Black water outlet; 17. Cooling water inlet; 18. Cooling water outlet; 19. Support; 20. Anti-blocking tube array. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0019] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products or devices.

[0020] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0021] Embodiment 1 A high efficiency heat exchanger, the structure of which is as follows Figure 1 As shown, the high-efficiency heat exchanger is installed vertically, and the upper part of one end is a black water inlet 15. Black water flows downward from a high place to reduce the risk of dust accumulation in the pipeline. A black water outlet 16 is provided at the lower part on the opposite side of the black water inlet. The black water outlet is inclined, and a support 19 is provided on the higher side to ensure that black water does not accumulate at the bottom and avoid blockage of the black water outlet. A cooling water inlet 17 is provided below the same side as the black water inlet 15 of the high-efficiency heat exchanger, and a cooling water outlet 18 is provided above the same side as the black water outlet 16.

[0022] The high-efficiency heat exchanger is made of 316L stainless steel, which has the ability to resist corrosion and erosion. The high-efficiency heat exchanger has anti-blocking tubes 20 arranged vertically inside, with black water flowing inside the anti-blocking tubes 20 and cooling water flowing outside. The surface structure of the anti-blocking tubes 20 is designed in a curved surface, so that the flow state of black water changes repeatedly when flowing through the tube wall, avoiding scaling of the anti-blocking tubes 20.

[0023] Embodiment 2 A pulverized coal gasification waste heat utilization system is established using the high-efficiency heat exchanger in Example 1. Figure 2 As shown, after the raw coal is crushed by the pulverized coal preparation and transportation system 1, the micron-sized pulverized coal is transported to the gasifier 2 for reaction. The synthesis gas produced after the reaction in the gasifier 2 is sent to the post-system through quenching, separation and washing. The black water (200°C, 4.0MPa) produced by quenching, separation and washing enters the high-pressure flash tank 3 for flash evaporation (0.6MPa, 159°C).

[0024] A primary high-efficiency heat exchanger 4 is set at the bottom of the high-pressure flash tank 3. After the black water is heat exchanged by the primary high-efficiency heat exchanger, the temperature drops from 159°C to 130°C, and the 2.0MPa desalted water is heated from 104°C to 127°C, and steam is produced as a by-product. The black water outlet of the primary high-efficiency heat exchanger 4 is connected to the low-pressure flash tank 5, which flashes 0.2~0.3MPa low-pressure steam. The low-pressure steam generated by the low-pressure flash tank 5 is transported to the pulverized coal preparation and transportation system 1, which can replace the existing 0.5MPa steam pulverized coal preparation and coal transportation heat tracing.

[0025] The 0.5MPa steam tracing used by the pulverized coal preparation and transportation system 1 and the 0.2~0.3MPa steam generated by the low-pressure flash tank 5 can be switched and used by adding a manual valve. When the 0.2~0.3MPa steam generated by the low-pressure flash tank 5 does not meet the demand, the valve can be adjusted to add 0.5MPa steam to ensure the insulation effect.

[0026] The output end of the low-pressure flash tank 5 is also connected to the input end of the primary high-efficiency heat exchanger 4, and a circulating pump 13 and a desalted water supply pipeline 14 are arranged on the connecting pipeline. The circulating pump 13 and the desalted water supply pipeline 14 are one on and one off, and the standby pump can be automatically started when the operating pump fails to supply desalted water to the primary high-efficiency heat exchanger 4, ensuring stable operation of the system.

[0027] The black water after heat exchange in the primary high-efficiency heat exchanger 4 passes through the low-pressure flash tank 5 and then through the secondary high-efficiency heat exchanger 6 to exchange heat with the low-pressure gray water from the gray water tank 7, ensuring that the temperature of the low-pressure gray water is ≥100°C before entering the deoxidation tank 8.

[0028] The temperature of black water after passing through the secondary high-efficiency heat exchanger is reduced from 127℃ to 105℃, and the temperature of gray water is increased from 80℃ to above 100℃. After being output from the secondary high-efficiency heat exchanger, the black water continues to exchange heat with the desalted water added to the system through the tertiary high-efficiency heat exchanger 9. The black water temperature after passing through the tertiary high-efficiency heat exchanger 9 is ≤80℃ and is discharged into the low-pressure flash tank 2 10 (0.15MPa, 127℃). At the same time, the desalted water after heat exchange in the tertiary high-efficiency heat exchanger 9 can be used as flushing water for the seals of various pumps and instruments or for user heating.

[0029] The output end of the low-pressure flash tank 10 is connected to the input end of the vacuum flash tank 11. The black water after flash evaporation in the low-pressure flash tank 10 enters the vacuum flash tank 11 for flash evaporation (-0.04MPa, 80°C), and the black water after vacuum flash evaporation enters the sedimentation tank 12 for sedimentation.

[0030] Therefore, the waste heat utilization system of pulverized coal gasification of the present invention is designed with a stepped waste heat utilization system on the basis of retaining the original design. The low-pressure steam flashed after the first-level heat exchange can replace the existing 0.5MPa steam for pulverized coal preparation and coal transportation heating, reduce boiler load, improve the waste heat utilization rate of the gasification device, and save 0.5MPa steam ≥ 20t / h; the black water from the second-level heat exchange can be heat exchanged with the low-pressure ash water from the ash water tank to ensure that the low-pressure ash water temperature is ≥100°C before entering the deoxygenation tank, reducing the large-scale venting problem existing in conventional deoxygenation.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A high efficiency heat exchanger, characterized in that: It includes a number of vertically arranged anti-blocking tubes, in which black water flows from top to bottom, and the anti-blocking tubes are of curved design; The cooling water flows from bottom to top outside the anti-blocking tube array, and the cooling water contacts and exchanges heat with the black water.

2. A high efficiency heat exchanger according to claim 1, characterized in that: The high-efficiency heat exchanger is made of wear-resistant and corrosion-resistant material.

3. A high efficiency heat exchanger according to claim 1, characterized in that: The black water outlet is tilted, and a support is provided on the higher side of the black water outlet.

4. A pulverized coal gasification waste heat utilization system, characterized in that: The method is established by arranging multiple stages of the high-efficiency heat exchanger according to any one of claims 1 to 3, including: (1) The synthesis gas generated after the reaction in the gasifier enters the high-pressure flash tank for flash evaporation through quenching, separation, and washing to produce black water. The high-pressure flash tank is connected to the primary high-efficiency heat exchanger, and the primary high-efficiency heat exchanger is connected to the low-pressure flash tank 1 to flash 0.2~0.3MPa low-pressure steam; (2) The 0.2-0.3 MPa low-pressure steam generated in step (1) is transported to the pulverized coal preparation and transportation system, and the 0.2-0.3 MPa low-pressure steam is used for pulverized coal preparation and transportation heating; (3) After the black water has been heat exchanged in the primary high-efficiency heat exchanger, it passes through the low-pressure flash tank and then through the secondary high-efficiency heat exchanger to exchange heat with the low-pressure gray water from the gray water tank. The low-pressure gray water with an output temperature of ≥100°C from the secondary high-efficiency heat exchanger enters the deoxidation tank; (4) The black water output after heat exchange in the secondary high-efficiency heat exchanger is exchanged with the desalted water added to the system through the tertiary high-efficiency heat exchanger; the black water with an output temperature of ≤80°C from the tertiary high-efficiency heat exchanger is discharged into the second low-pressure flash tank; (5) The black water after the second flash evaporation in the low-pressure flash tank enters the vacuum flash tank for flash evaporation, and the black water after the vacuum flash evaporation enters the sedimentation tank for sedimentation.

5. The pulverized coal gasification waste heat utilization system according to claim 4, characterized in that: The 0.5MPa steam input pipeline and the 0.2~0.3MPa steam input pipeline generated by the low-pressure flash tank are connected to the pulverized coal preparation and transportation system through the same valve.

6. The pulverized coal gasification waste heat utilization system according to claim 4, characterized in that: The output end of the low-pressure flash tank 1 is also connected to the input end of the first-stage high-efficiency heat exchanger. A circulating pump and a desalted water supply pipeline are arranged on the connecting pipeline between the output end of the low-pressure flash tank 1 and the input end of the first-stage high-efficiency heat exchanger.

7. The pulverized coal gasification waste heat utilization system according to claim 4, characterized in that: The black water with output temperature ≤80℃ from the three-stage high-efficiency heat exchanger can be used as flushing water for pump seals, instrument seals or for user heating.

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