Method and system for producing low-pressure superheated or saturated steam through coal gasification black water waste heat

Abstract

The invention relates to the technical field of black water waste heat recovery, and provides a method for producing low-pressure superheated or saturated steam by coal gasification black water waste heat, which comprises the following steps: carrying out at least one stage of flash evaporation on high-temperature black water to obtain black water flash evaporation steam with corresponding temperature; steam generated through black water flash evaporation is used as a heat source to heat the intermediate heating medium in an indirect heat exchange mode, and the intermediate heating medium at the first preset temperature is obtained; outlet water of the deaerator is sent out through a deoxygenated water booster pump and is divided into two paths after being preheated by a preheater, heat exchange is conducted on the first path of deoxygenated water and an intermediate heating medium at the first preset temperature, and overheated or saturated steam at the first preset temperature and an intermediate heating medium at the second preset temperature are obtained; and the second path of deoxygenated water exchanges heat with the intermediate heating medium at the second preset temperature, and overheated or saturated steam at the second preset temperature is obtained. By the adoption of the technology, black water waste heat is converted into clean superheated steam or saturated steam, the energy utilization efficiency of the whole plant can be greatly improved, and comprehensive energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology from black water, specifically a method and system for generating low-pressure superheated or saturated steam from waste heat of coal gasification black water. Background Technology

[0002] Coal chemical gasification furnaces produce 200-500 t / h of black water, with a pressure of about 6.0 MPa and a temperature of about 240°C. The black water contains a large amount of heat energy, as well as coal slag, suspended solids, etc. How to efficiently recover and utilize this heat energy is a huge challenge.

[0003] Currently, the mainstream method for waste heat recovery from black water in domestic coal chemical gasification furnaces is a three-stage flash evaporation process, consisting of approximately 0.8 MPa high-pressure flash evaporation, 0.3 MPa low-pressure flash evaporation, and -0.05 MPa vacuum flash evaporation. This flash steam contains non-condensable gases such as carbon monoxide, hydrogen, hydrogen sulfide, and carbon dioxide. The 0.8 MPa saturated steam is used to heat the ash water, raising it from 104°C to 169°C. The 0.3 MPa saturated steam is used to heat the deaerator inlet water. The vacuum flash steam is cooled by circulating water and then separated into gas and water. The non-condensable gases are sent to the flare, while the condensate is returned to the ash water pool for reuse.

[0004] The main disadvantages of the above black water waste heat recovery methods are as follows:

[0005] 1. Severe waste of energy grade: The initial temperature of black water is usually over 220℃, containing a large amount of high-grade heat energy. Traditional processes only recover a portion of low-grade heat energy. This low-grade heat energy can only be used within the system and cannot be integrated into the plant's steam network or steam turbine power generation, resulting in low heat energy recovery efficiency and poor recovery grade. At the same time, a large amount of circulating water is required for cooling, causing huge waste.

[0006] 2. Low product value: The recovered heat exists in the form of low-pressure steam or hot water containing acidic impurities. It is unclean and of low grade, and can only be used within the system. For example, 0.8MPa first-level flash steam is used to heat the grey water from 104 degrees Celsius to 169 degrees Celsius. The unused flash steam is then used to heat the deaerator inlet water. The unused flash steam can only be vented or cooled by circulating water. The condensate is then recovered to the return water tank after gas-liquid separation. The heat is lost to the air through the cooling tower. This recovery method can only utilize part of the heat energy of the black water for heating, and cannot be used for work.

[0007] Although existing technologies include solutions for recovering low-temperature waste heat using the Organic Rankine Cycle (ORC) or improvements for recovering some heat through single-stage heat exchange, none of them systematically solve the fundamental problems such as inefficient utilization of high-grade heat sources, safe isolation between dirty heat sources and clean systems, and poor adaptability to all operating conditions. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method and system for generating low-pressure superheated or saturated steam from waste heat of coal gasification black water. The method employs multi-stage flash evaporation and intermediate heat transfer medium to produce clean superheated or saturated steam, thereby improving steam quality. The steam is then integrated into the plant's steam network, enhancing overall energy utilization efficiency and reducing carbon emissions.

[0009] According to one aspect of the present invention, the present invention provides a method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water, comprising the following steps:

[0010] High-temperature black water at 230℃-260℃ is subjected to at least one stage of flash evaporation to obtain black water flash steam at the corresponding temperature.

[0011] The intermediate heat medium is heated by using the steam produced by black water flash evaporation as a heat source in an indirect heat exchange manner to obtain an intermediate heat medium at a first predetermined temperature.

[0012] The deaerator effluent is sent out through a deaerator water booster pump. After being preheated by a preheater, it is divided into two streams. The first stream of deaerator water is exchanged with an intermediate heat medium at a first predetermined temperature to obtain superheated or saturated steam at the first predetermined temperature and an intermediate heat medium at a second predetermined temperature.

[0013] The second deoxygenated water is exchanged with an intermediate heat medium at a second predetermined temperature to obtain superheated or saturated steam at the second predetermined temperature.

[0014] Furthermore, the high-temperature black water at 230℃-260℃ undergoes at least one stage of flash evaporation to obtain black water flash steam at the corresponding temperature, including:

[0015] High-temperature black water is flashed through multiple flash tanks in stages to obtain black water flash steam at the corresponding temperature;

[0016] The black water flash steam obtained from each stage of flash evaporation is fed into the corresponding steam condenser to exchange heat with the intermediate heat medium and condense.

[0017] The black water after the end flash evaporation is subjected to vacuum flash evaporation, and the black water flash evaporation vapor after vacuum flash evaporation enters the gas-liquid separator for gas-liquid separation.

[0018] The final separated ash water is fed into an ash water tank, while the non-condensable gas is discharged using a vacuum pump. Finally, the flash-evaporated black water is pumped into a slag water tank for treatment.

[0019] Furthermore, the ash water obtained after the flash steam of each level of black water is condensed by heat exchange in the corresponding steam condenser is fed into a cooler for cooling, and then the cooled ash water is fed into a gas-liquid separator for gas-liquid separation. The separated ash water is fed into an ash water tank, and the separated acidic gas is centrally treated.

[0020] Furthermore, the steam produced by black water flash evaporation is used as a heat source to indirectly heat the intermediate heat medium to obtain an intermediate heat medium at a first predetermined temperature, including:

[0021] An intermediate heat medium pressure stabilizing tank is installed at the intermediate heat medium inlet, and steam at a certain pressure is introduced into the intermediate heat medium pressure stabilizing tank for pressure stabilization and regulation. Combined with the intermediate heat medium booster pump set, the intermediate heat medium pipeline is pressurized.

[0022] After the intermediate heat medium is introduced into the last stage steam condenser to exchange heat with the black water flash steam at the corresponding temperature, it exchanges heat with black water flash steam at different temperatures in each stage.

[0023] The intermediate heat medium is obtained at the second predetermined temperature midway, and heat exchange continues to obtain the intermediate heat medium at the first predetermined temperature.

[0024] Furthermore, the deaerator effluent is pumped out via a deaerator booster pump, preheated in a preheater, and then divided into two streams. The first stream of deaerator water exchanges heat with an intermediate heat medium at a first predetermined temperature to obtain superheated or saturated steam at the first predetermined temperature and an intermediate heat medium at a second predetermined temperature, including:

[0025] The first deoxygenated water pipeline is connected to a low-pressure deoxygenated water pressure stabilizing tank. Steam at a certain pressure is introduced into the low-pressure deoxygenated water pressure stabilizing tank for pressure stabilization and regulation. Combined with the low-pressure deoxygenated water booster pump, the deoxygenated water is pressurized.

[0026] The pressurized deoxygenated water passes sequentially through an intermediate preheater, an intermediate steam generator, and an intermediate superheater to obtain superheated or saturated steam at a first predetermined temperature. Meanwhile, the intermediate heat medium at the first predetermined temperature passes sequentially through the intermediate superheater, the intermediate steam generator, and the intermediate preheater to exchange heat with the deoxygenated water, thereby obtaining an intermediate heat medium at a second predetermined temperature.

[0027] Furthermore, the second deoxygenated water is exchanged with an intermediate heat medium at a second predetermined temperature to obtain superheated or saturated steam at the second predetermined temperature, including:

[0028] The second deoxygenated water passes sequentially through a low-level steam generator and a low-level superheater. The steam generated by the low-level steam generator is divided into two paths. One path enters the low-level superheater for heating to obtain superheated or saturated steam at a second predetermined temperature. The other path enters a low-pressure deoxygenated water pressure stabilizing tank, which, in conjunction with a low-pressure deoxygenated water booster pump, pressurizes the first path of deoxygenated water.

[0029] The intermediate heat medium at the second predetermined temperature then passes through the low-stage superheater and the low-stage steam generator in sequence to obtain the intermediate heat medium at the third predetermined temperature.

[0030] The intermediate heat medium at the third predetermined temperature is passed through a low-level preheater and exchanged with deoxygenated water delivered by an atmospheric pressure deoxygenated water booster pump.

[0031] Furthermore, the intermediate heat medium passing through the low-level preheater is connected to the ORC generator set or refrigeration unit, and the intermediate heat medium passing through the ORC generator set or refrigeration unit enters the starting point of the intermediate heat medium pipeline.

[0032] According to one aspect of the present invention, the present invention provides a system for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water, including a black water flash heat exchange unit and a heat utilization unit.

[0033] The black water flash heat exchange unit includes at least one flash tank, at least one steam condenser, a gas-liquid separator, an intermediate heat medium pipeline, and an intermediate heat medium booster pump set. The steam outlet of the flash tank is connected to the inlet of the steam condenser through the steam pipeline, the intermediate heat medium pipeline is connected to the steam condenser, and the gray water outlet of the steam condenser and the steam outlet of the terminal flash tank are respectively connected to the corresponding gas-liquid separators.

[0034] The heat utilization unit includes a deoxygenated water booster pump, a low-level preheater, a primary heat recovery unit, and a secondary heat recovery unit. The deoxygenated water booster pump is connected to the low-level preheater through a deoxygenated water pipeline. The deoxygenated water pipeline connected to the outlet of the low-level preheater is divided into two paths: one path is connected to the primary heat recovery unit, and the other path is connected to the secondary heat recovery unit.

[0035] The primary heat recovery unit includes a low-level superheater and a low-level steam generator. One of the deoxygenated water pipelines passing through the low-level preheater is connected to the low-level steam generator. The steam outlet of the low-level steam generator is connected to the low-level superheater through a steam pipeline.

[0036] The intermediate heat recovery unit includes a low-pressure deoxygenated water pressure stabilizing tank, a low-pressure deoxygenated water booster pump, an intermediate preheater, an intermediate steam generator, and an intermediate superheater. Another deoxygenated water pipeline passing through the low-pressure preheater is connected to the low-pressure deoxygenated water booster pump and is connected to the low-pressure deoxygenated water pressure stabilizing tank. The low-pressure deoxygenated water booster pump is connected to the intermediate preheater through a deoxygenated water pipeline. The intermediate preheater is connected to the intermediate steam generator through a deoxygenated water pipeline. The intermediate steam generator is connected to the intermediate superheater through a steam pipeline.

[0037] Two steam pipelines are led out from the steam outlet of the low-level steam generator. One steam pipeline is connected to the low-level superheater, and the other steam pipeline is connected to the low-pressure deoxygenated water pressure stabilizing tank.

[0038] Furthermore, there are four flash tanks: a primary medium-pressure flash tank, a secondary low-pressure flash tank, a tertiary low-pressure flash tank, and a vacuum flash tank. There are also four steam condensers: two primary flash steam condensers, one secondary flash steam condenser, and one tertiary flash steam condenser. The steam outlet of the primary medium-pressure flash tank is connected in parallel to a pair of primary flash steam condensers via steam pipelines. The condensate outlet of the primary medium-pressure flash tank is connected to the secondary low-pressure flash tank. The steam outlet of the secondary low-pressure flash tank is connected to the secondary flash steam condenser via steam pipelines. The condensate outlet of the secondary low-pressure flash tank is connected to the tertiary low-pressure flash tank. The steam outlet of the tertiary low-pressure flash tank is connected to the tertiary flash steam condenser via steam pipelines. The condensate outlet of the tertiary low-pressure flash tank is connected to the vacuum flash tank. The steam outlet of the vacuum flash tank is connected to a gas-liquid separator via steam pipelines. The ash water outlets of the primary flash steam condensers, secondary flash steam condensers, and tertiary flash steam condensers are connected to their respective gas-liquid separators via coolers.

[0039] Furthermore, the intermediate heat medium pipeline is connected end to end, and an intermediate heat medium pressure stabilizing tank is also connected to the end of the connection point. The intermediate heat medium pipeline passes through the three-flash steam condenser, the two-flash steam condenser, and the second one-flash steam primary condenser in sequence. In the one-flash steam primary condenser, it splits into two paths. One path continues into the first one-flash steam primary condenser and passes through the intermediate superheater, intermediate steam generator, and intermediate preheater in sequence. The other path merges with the intermediate heat medium pipeline that has passed through the intermediate preheater and enters the low-level superheater. Then, it passes through the low-level steam generator and low-level preheater in sequence, and can be selectively introduced into the ORC generator set. Finally, it returns to the beginning of the intermediate heat medium pipeline.

[0040] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0041] This method and system for generating low-pressure superheated or saturated steam from waste heat of coal gasification black water reduces the temperature of black water from 240℃ to 100℃, recovering a maximum temperature difference of 140℃. The recovered waste heat of the black water is converted into low-pressure superheated or saturated steam, which can be integrated into the plant's steam network for external heating, or used to drive steam turbines for power generation or to drive refrigeration units for cooling. This fully utilizes the waste heat of the black water. The system employs multi-stage flash evaporation, with intermediate heat transfer medium effectively isolated from dirty heat sources, ensuring that the final output is clean superheated or saturated steam that can be connected to the grid. The system has high reliability and stable operation, and the high-grade superheated or saturated steam produced maximizes energy-saving and carbon-reduction benefits. This system uses black water, a relatively dirty heat source, as an energy source to achieve combined heat and power (CHP) and cooling, realizing innovation.

[0042] The method and system for generating low-pressure superheated or saturated steam from waste heat of coal gasification black water may cause leakage in the intermediate heat medium pipeline during the heat exchange process due to the corrosiveness of the black water condensate and black water flash steam. However, this will not affect the generation of superheated or saturated steam in the subsequent deoxygenated water pipeline. Once a leakage occurs, it can be repaired immediately.

[0043] The method and system for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water involves the intermediate heat medium being recycled between the black water flash steam and the deoxygenated water heat exchange equipment at each stage. This allows for the continuous extraction of latent heat from the black water flash steam, which is then transferred to the deoxygenated water. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the present invention;

[0045] Figure 2 This is a schematic diagram of the black water flash heat exchange unit in this invention;

[0046] Figure 3 This is a schematic diagram of the heat utilization unit in this invention;

[0047] Figure 4 This is a schematic diagram of the primary heat recovery unit and the intermediate heat recovery unit of the heat utilization unit in this invention.

[0048] In the diagram: 1. Primary medium-pressure flash tank; 2. Secondary low-pressure flash tank; 3. Tertiary low-pressure flash tank; 4. Vacuum flash tank; 5. Gas-liquid separator; 6. Intermediate heat medium pressure stabilizing tank; 7. Intermediate heat medium booster pump set; 8. First-stage flash steam condenser; 9. Second-stage flash steam condenser; 10. Third-stage flash steam condenser; 11. Cooler; 12. Deoxygenated water booster pump; 13. Low-stage preheater; 14. Low-pressure deoxygenated water pressure stabilizing tank; 15. Low-pressure deoxygenated water booster pump; 16. Intermediate preheater; 17. Intermediate steam generator; 18. Intermediate superheater; 19. Low-stage steam generator; 20. Low-stage superheater. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Please see Figure 1-4 A method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to an embodiment of the present invention includes the following steps:

[0051] High-temperature black water at 230℃-260℃ is subjected to at least one stage of flash evaporation to obtain black water flash steam at the corresponding temperature.

[0052] The intermediate heat medium is heated by using the steam produced by black water flash evaporation as a heat source in an indirect heat exchange manner to obtain an intermediate heat medium at a first predetermined temperature.

[0053] The deaerator outlet water (104℃) is sent out through the deaerator water booster pump. After being preheated by the preheater, it is divided into two streams. One stream of deaerator water is exchanged with the intermediate heat medium at the first predetermined temperature to obtain superheated or saturated steam at the first predetermined temperature and the intermediate heat medium at the second predetermined temperature.

[0054] The deoxygenated water from another source is exchanged with an intermediate heat medium at a second predetermined temperature to obtain superheated or saturated steam at the second predetermined temperature.

[0055] In this embodiment of the invention, high-temperature black water at 230℃-260℃ undergoes at least one stage of flash evaporation to obtain black water flash steam at the corresponding temperature, including:

[0056] High-temperature black water is flashed through multiple flash tanks in stages to obtain black water flash steam at the corresponding temperature;

[0057] The black water flash steam obtained from each stage of flash evaporation is fed into the corresponding steam condenser to exchange heat with the intermediate heat medium and condense.

[0058] The black water after the end flash evaporation is subjected to vacuum flash evaporation, and the black water flash evaporation vapor after vacuum flash evaporation enters the gas-liquid separator for gas-liquid separation.

[0059] The final separated ash water is fed into an ash water tank, while the non-condensable gas is discharged using a vacuum pump. Finally, the flash-evaporated black water is pumped into a slag water tank for treatment.

[0060] In a preferred embodiment, there are preferably four flash tanks, namely a primary medium-pressure flash tank 1, a secondary low-pressure flash tank 2, a tertiary low-pressure flash tank 3, and a vacuum flash tank 4. There are preferably four steam condensers, namely two primary flash steam condensers 8, one secondary flash steam condenser 9, and one tertiary flash steam condenser 10.

[0061] In practical application, black water at 6 MPa and 240°C is first fed into a primary medium-pressure flash tank 1 for flash evaporation, yielding black water flash steam at 2 MPa and 214.91°C, and black water condensate at 2 MPa and 214.91°C. The black water flash steam at 2 MPa and 214.91°C is then fed into two primary flash steam condensers 8 for heat exchange and condensation, yielding two streams of grey water at 2 MPa and 214.91°C. The black water condensate at 2 MPa and 214.91°C obtained from the primary medium-pressure flash tank 1 is then fed into a secondary low-pressure flash tank 2 for flash evaporation, yielding black water flash steam at 0.95 MPa and 182.05°C, and black water condensate at 0.95 MPa and 182.05°C. The black water flash steam at 0.95 MPa and 182.05°C is then fed into a secondary flash steam condenser 9 for heat exchange and condensation, yielding 0.95 MPa and 182.05°C grey water. The black water at 0.95 MPa and 182.05℃ is obtained from the secondary low-pressure flash tank 2. This black water condensate, also at 0.95 MPa and 182.05℃, is then passed into the tertiary low-pressure flash tank 3 for flash evaporation, yielding black water flash steam at 0.35 MPa and 148.07℃, as well as black water condensate at 0.35 MPa and 148.07℃. The black water flash steam at 0.35 MPa and 148.07℃ is then passed into the triple flash steam condenser 10 for heat exchange and condensation, yielding black water at 0.35 MPa and 148.07℃. The black water condensate obtained from the tertiary low-pressure flash tank 3 is then further processed. Black water condensate at MPa and 148.07℃ is fed into vacuum flash tank 4 for vacuum flash evaporation, resulting in black water flash steam at -0.07 MPa and 69.1℃ and black water condensate at -0.07 MPa and 70℃. The black water condensate at -0.07 MPa and 70℃ is sent to the black water settling tank, while the black water flash steam at -0.07 MPa and 69.1℃ is fed into the corresponding gas-liquid separator 5. Non-condensable gases are separated by the gas-liquid separator 5 and extracted by a vacuum pump, while the separated ash water is sent to the ash removal tank.

[0062] In addition, the two streams of ash water with a pressure of 2 MPa and a temperature of 214.91°C obtained after heat exchange and condensation by the two flash steam condensers 8, the ash water with a pressure of 0.95 MPa and a temperature of 182.05°C obtained after heat exchange and condensation by the two flash steam condensers 9, and the ash water with a pressure of 0.35 MPa and a temperature of 148.07°C obtained after heat exchange and condensation by the three flash steam condensers 10 are respectively fed into coolers for cooling to a temperature of 70°C. The cooled ash water is then fed into a gas-liquid separator for gas-liquid separation. The separated ash water is then fed into an ash water tank, while the separated acidic gases are separately processed.

[0063] In the above process, the heat-side medium of all heat exchange equipment is steam from black water flash evaporation. Since the impurity content in black water flash evaporation steam is much lower than that in black water flash condensate, compared with direct black water heat exchange, using black water flash evaporation steam for heat exchange can effectively improve the operating conditions of heat exchange equipment and significantly reduce the frequency of shutdown and cleaning of heat exchange equipment due to impurity blockage.

[0064] Due to the complex composition of black water, a small amount of non-condensable gases will inevitably exist in the black water flash steam. If the non-condensable gases are not removed in time, they will accumulate as the system runs for a longer period of time, which will gradually have an adverse effect on the heat exchange efficiency of the heat exchange equipment. Therefore, in the above-mentioned staged flash evaporation process, the condensate of the flash steam heat exchange at each stage is sent to the next stage of flash evaporation, which can squeeze the non-condensable gases downstream step by step, and finally concentrate them in the vacuum flash tank at the end, and then be separated and discharged by the gas-liquid separator 5 connected to it.

[0065] In this embodiment of the invention, steam produced by black water flash evaporation is used as a heat source to heat the intermediate heat medium indirectly, thereby obtaining an intermediate heat medium at a first predetermined temperature and an intermediate heat medium at a second predetermined temperature, including:

[0066] An intermediate heat medium pressure stabilizing tank 6 is installed at the intermediate heat medium inlet, and steam at a certain pressure is introduced into the intermediate heat medium pressure stabilizing tank 6 for pressure stabilization and regulation. Combined with the intermediate heat medium booster pump group 7, the intermediate heat medium pipeline is pressurized.

[0067] After the intermediate heat medium is introduced into the last stage steam condenser to exchange heat with the black water flash steam at the corresponding temperature, it exchanges heat with black water flash steam at different temperatures in each stage.

[0068] The intermediate heat medium is obtained at the second predetermined temperature midway, and heat exchange continues to obtain the intermediate heat medium at the first predetermined temperature.

[0069] In a preferred embodiment, the intermediate heat medium at the first predetermined temperature is 2.5 MPa and 200°C, and the intermediate heat medium at the second predetermined temperature is 2.5 MPa and 180°C.

[0070] In practical use, 1.5-2 MPa of steam is introduced into the intermediate heat medium pressure stabilizing tank 6 to stabilize the intermediate heat medium pressure at a suitable level. Then, the intermediate heat medium booster pump set 7 pressurizes the medium, sending the 2.5 MPa, 70℃ intermediate heat medium into the triple flash steam condenser 10 for heat exchange with 0.35 MPa, 148.07℃ black water flash steam, yielding an intermediate heat medium of 2.5 MPa, 120℃. This 2.5 MPa, 120℃ intermediate heat medium is then introduced into the second flash steam condenser 9 for heat exchange with 0.95 MPa, 182.05℃ black water flash steam, yielding an intermediate heat medium of 2.5 MPa, 164.29℃. Finally, this 2.5 MPa, 164.29℃ intermediate heat medium is introduced into the second single flash steam condenser 8 for heat exchange with 2 MPa, 214.91℃ black water flash steam, yielding an intermediate heat medium of 2.5 MPa. The intermediate heat medium at MPa and 180℃ (second predetermined temperature) is divided into two paths.

[0071] A 2.5 MPa, 180°C intermediate heat medium is introduced into the first flash steam stage condenser 8, and continues to exchange heat with the 2 MPa, 214.91°C black water flash steam to obtain an intermediate heat medium of 2.5 MPa, 200°C (first predetermined temperature).

[0072] The intermediate heat medium at the second predetermined temperature from another source is combined with the intermediate heat medium at the second predetermined temperature obtained from the intermediate preheater 16 and then fed into the low-level superheater 20 for heat exchange with the deoxygenated water.

[0073] The intermediate heat medium after extracting latent heat from the flash steam of black water at various levels using the above process is used as a heat source to heat deoxygenated water, producing saturated or superheated steam at one or more pressures.

[0074] In this embodiment of the invention, the deaerator effluent is sent out via a deaerator booster pump, preheated by a preheater, and then divided into two streams. The first stream of deaerator water is exchanged with an intermediate heat medium at a first predetermined temperature to obtain superheated or saturated steam at the first predetermined temperature and an intermediate heat medium at a second predetermined temperature, including:

[0075] The first deoxygenated water pipeline is connected to a low-pressure deoxygenated water pressure stabilizing tank 14. Steam at a certain pressure is introduced into the low-pressure deoxygenated water pressure stabilizing tank 14 to stabilize and regulate the pressure. Combined with the low-pressure deoxygenated water booster pump 15, the deoxygenated water is pressurized.

[0076] The pressurized deoxygenated water passes sequentially through the intermediate preheater 16, the intermediate steam generator 17, and the intermediate superheater 18 to obtain superheated steam at a first predetermined temperature. Meanwhile, the intermediate heat medium at the first predetermined temperature passes sequentially through the intermediate superheater 18, the intermediate steam generator 17, and the intermediate preheater 16 to exchange heat with the deoxygenated water, thereby obtaining an intermediate heat medium at a second predetermined temperature.

[0077] In a preferred embodiment, the intermediate heat medium at the first predetermined temperature is 2.5 MPa and 200°C, and the superheated steam at the first predetermined temperature is superheated steam at 0.5 MPa and 190°C.

[0078] In practical use, the deaerator effluent is pressurized by a deaerator water booster pump, and deaerator water at 0.1-0.2 MPa and 104°C is sent to the low-stage preheater 13 for preheating to obtain deaerator water at 0.1-0.2 MPa and 120.53°C. The obtained deaerator water is divided into two streams. The first stream is connected to a low-pressure deaerator water stabilizing tank 14. Steam at 0.1-0.2 MPa and 120.53°C is introduced into the low-pressure deaerator water stabilizing tank 14, and combined with the low-pressure deaerator water booster pump 15, the deaerator water is further heated. Water is pressurized to obtain deoxygenated water at 0.5 MPa and 120°C. The deoxygenated water is then sent to the intermediate preheater 16 for preheating to obtain deoxygenated water at 0.5 MPa and 151.8°C. The deoxygenated water at 0.5 MPa and 151.8°C is then sent to the intermediate steam generator 17 for evaporation to obtain steam at 0.5 MPa and 151.8°C. The steam at 0.5 MPa and 151.8°C is then fed into the intermediate superheater 18 to obtain superheated steam at 0.5 MPa and 190°C.

[0079] When using an intermediate heat medium as a heat source to heat deoxygenated water, the intermediate heat medium at a first predetermined temperature (2.5 MPa, 200°C) is first passed into the intermediate superheater 18 to exchange heat with steam at 0.5 MPa, 151.8°C, resulting in an intermediate heat medium at 2.5 MPa, 198.73°C. This intermediate heat medium at 2.5 MPa, 198.73°C is then passed into the intermediate steam generator 17 to exchange heat with deoxygenated water at 0.5 MPa, 151.8°C, resulting in an intermediate heat medium at 2.5 MPa, 182°C. Finally, this intermediate heat medium at 2.5 MPa, 182°C is passed into the intermediate preheater 16 to exchange heat with deoxygenated water at 0.5 MPa, 120°C, resulting in an intermediate heat medium at a second predetermined temperature (2.5 MPa, 180°C). This second predetermined temperature (2.5 MPa, 180°C) can then be... The intermediate heat medium (MPa, 180℃) and the intermediate heat medium at the second predetermined temperature obtained from the flash steam primary condenser 8 are combined and fed into the low-level superheater 20 to continue heat exchange.

[0080] In this embodiment of the invention, heat exchange is performed between the second deoxygenated water and an intermediate heat medium at a second predetermined temperature to obtain superheated saturated steam at the second predetermined temperature, including:

[0081] The second deoxygenated water passes sequentially through a low-level steam generator 19 and a low-level superheater 20. The steam generated by the low-level steam generator 19 is divided into two paths. One path enters the low-level superheater 20 for heating to obtain superheated saturated steam at the second predetermined temperature. The other path enters the low-pressure deoxygenated water pressure stabilizing tank 14, which, together with the low-pressure deoxygenated water booster pump 15, pressurizes the first path of deoxygenated water.

[0082] The intermediate heat medium at the second predetermined temperature then passes through the low-level superheater 20 and the low-level steam generator 19 in sequence to obtain the intermediate heat medium at the third predetermined temperature.

[0083] The intermediate heat medium at the third predetermined temperature is introduced into the low-level preheater 13 to exchange heat with the deoxygenated water delivered by the atmospheric pressure deoxygenated water booster pump.

[0084] In a preferred embodiment, the superheated steam at the second predetermined temperature is superheated steam at 0.1 MPa and 145°C, and the intermediate heat medium at the third predetermined temperature is intermediate heat medium at 2.5 MPa and 130°C.

[0085] In practical use, the second deoxygenated water is first passed into the low-level steam generator 19 for evaporation to obtain steam at 0.1-0.2 MPa and 120.53℃.

[0086] The steam obtained at 0.1-0.2 MPa and 120.53°C is divided into two streams. One stream enters the low-level superheater 20 for heating to obtain superheated steam at 0.1 MPa and 145°C. The other stream enters the low-pressure deoxygenated water pressure stabilizing tank 14 and, together with the low-pressure deoxygenated water booster pump 15, pressurizes the first stream of deoxygenated water.

[0087] Since the deoxygenated water between the low-level preheater 13 and the low-level evaporator is saturated, in order to avoid flash evaporation of the deoxygenated water due to pressure drop, the cold side steam of the low-level steam generator 19 must be introduced as pressure-stabilizing steam to the low-pressure deoxygenated water pressure stabilizing tank 14 to maintain the pressure of the deoxygenated water in the low-pressure deoxygenated water pressure stabilizing tank 14. At the same time, the head of the low-pressure deoxygenated water booster pump 15 is reduced to reduce the power consumption of the motor in the low-pressure deoxygenated water booster pump 15.

[0088] When using an intermediate heat medium as a heat source to heat deoxygenated water, the intermediate heat medium at the second predetermined temperature (2.5 MPa, 180°C) is first introduced into the low-stage superheater 20 to exchange heat with steam at 0.1 MPa, 120.53°C, to obtain an intermediate heat medium at 2.5 MPa, 160°C. The obtained intermediate heat medium at 2.5 MPa, 160°C is then introduced into the low-stage steam generator 19 to exchange heat with deoxygenated water at 0.1 MPa, 120.53°C, to obtain an intermediate heat medium at 2.5 MPa, 130°C, which is the intermediate heat medium at the third predetermined temperature.

[0089] The intermediate heat medium at the third predetermined temperature can be introduced into the low-level preheater 13 to exchange heat with the deoxygenated water at 0.1 MPa and 104°C delivered by the atmospheric pressure deoxygenated water booster pump, to obtain an intermediate heat medium at 2.5 MPa and 125°C.

[0090] In this embodiment of the invention, the intermediate heat medium passing through the low-level preheater 13 is connected to the ORC generator set or the refrigeration unit, and the intermediate heat medium passing through the ORC generator set or the refrigeration unit is recycled at the starting point of the intermediate heat medium pipeline.

[0091] During the circulation process, the intermediate heat medium can be directly returned to the black water flash steam heat exchanger after exchanging heat with the deoxygenated water at the low-temperature end. Alternatively, the intermediate heat medium can be used as a heat source to send to the ORC generator set for power generation. After further cooling of the intermediate heat medium, it can be returned to the black water flash steam heat exchanger.

[0092] This invention provides a system for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water, including a black water flash heat exchange unit and a heat utilization unit.

[0093] By setting up a black water flash evaporation heat exchange unit, high-temperature black water undergoes single-stage or multi-stage flash evaporation. The steam produced by each stage of flash evaporation is condensed through a stepped heat exchange using an intermediate heat medium, thereby extracting the latent heat from the steam.

[0094] Then, through the heat utilization unit, the heat medium after extracting latent heat from the flash steam of black water at all levels is used as a heat source to heat the deoxygenated water, producing saturated or superheated steam at one or more pressures. The recovered waste heat of black water is converted into low-pressure superheated or saturated steam, which can be connected to the whole plant's steam pipeline network for external heating, or it can drive the steam turbine to do work and generate electricity, making full use of the waste heat of black water.

[0095] In this embodiment of the invention, the black water flash heat exchange unit includes at least one flash tank, at least one steam condenser, a gas-liquid separator 5, an intermediate heat medium pipeline, and an intermediate heat medium booster pump group 7. The steam outlet of the flash tank is connected to the inlet of the steam condenser through the steam pipeline, the intermediate heat medium pipeline is connected to the steam condenser, and the ash water outlet of the steam condenser and the steam outlet of the terminal flash tank are respectively connected to the gas-liquid separator 5 through coolers.

[0096] In a preferred embodiment, there are preferably four flash tanks, namely a primary flash tank 1, a secondary low-pressure flash tank 2, a tertiary low-pressure flash tank 3, and a vacuum flash tank 4. There are preferably four steam condensers, namely two primary flash steam condensers 8, one secondary flash steam condenser 9, and one tertiary flash steam condenser 10.

[0097] Specifically, the steam outlet of the first-stage medium-pressure flash tank 1 is connected in parallel to a pair of first-stage flash steam condensers 8 via a steam pipeline. The condensate outlet of the first-stage medium-pressure flash tank 1 is connected to the second-stage low-pressure flash tank 2. The steam outlet of the second-stage low-pressure flash tank 2 is connected to the second-stage flash steam condenser 9 via a steam pipeline. The condensate outlet of the second-stage low-pressure flash tank 2 is connected to the third-stage low-pressure flash tank 3. The steam outlet of the third-stage low-pressure flash tank 3 is connected to the third-stage flash steam condenser 10 via a steam pipeline. The condensate outlet of the third-stage low-pressure flash tank 3 is connected to the vacuum flash tank 4. The steam outlet of the vacuum flash tank 4 is connected to the corresponding gas-liquid separator 5 via a steam pipeline. The ash water outlets of the first-stage flash steam condenser 8, the second-stage flash steam condenser 9, and the third-stage flash steam condenser 10 are respectively connected to the corresponding gas-liquid separator 5 via coolers.

[0098] In this embodiment of the invention, the intermediate heat medium pipeline is connected end to end, and an intermediate heat medium pressure stabilizing tank 6 is also connected to the rear end of the connection between the two ends of the intermediate heat medium pipeline.

[0099] The intermediate heat medium returning to the black water flash steam heat exchanger must have its pressure stabilized at a suitable level by the intermediate heat medium pressure stabilizing tank 6, and then be pressurized by the intermediate heat medium booster pump group 7 before being sent to the black water flash steam heat exchangers at each stage.

[0100] Since the intermediate heat medium needs to reach a high temperature, in order to maintain the pressure of the intermediate heat medium during circulation without a large drop, an external steam line must be introduced as the stabilizing steam for the intermediate heat medium pressure tank 6 to maintain the pump inlet pressure of the intermediate heat medium booster pump, thereby reducing the required head of the intermediate heat medium booster pump group 7 as much as possible and reducing its power consumption.

[0101] In this embodiment of the invention, the heat utilization unit includes a deoxygenated water booster pump 12, a low-level preheater 13, a primary heat recovery section and a secondary heat recovery section. The deoxygenated water booster pump 12 is connected to the low-level preheater 13 through a deoxygenated water pipeline. The deoxygenated water pipeline connected to the outlet of the low-level preheater 13 is divided into two paths, one of which is connected to the primary heat recovery section and the other of which is connected to the secondary heat recovery section.

[0102] In a preferred embodiment, the primary heat recovery unit includes a low-level superheater 20 and a low-level steam generator 19. A deoxygenated water pipeline from the low-level preheater 13 is connected to the low-level steam generator 19, and the steam outlet of the low-level steam generator 19 is connected to the low-level superheater 20 via a steam pipeline.

[0103] After being preheated by the low-level preheater 13, the deoxygenated water is directly fed into the low-level steam generator 19 to evaporate into superheated steam. Then, it enters the low-level superheater 20 for further heating, producing pressurized steam.

[0104] In a preferred embodiment, the intermediate heat recovery unit includes a low-pressure deoxygenated water pressure stabilizing tank 14, a low-pressure deoxygenated water booster pump 15, an intermediate preheater 16, an intermediate steam generator 17, and an intermediate superheater 18. Another deoxygenated water pipeline through the low-pressure preheater 13 is connected to the low-pressure deoxygenated water booster pump 15 and is connected to the low-pressure deoxygenated water pressure stabilizing tank 14. The low-pressure deoxygenated water booster pump 15 is connected to the intermediate preheater 16 through a deoxygenated water pipeline. The intermediate preheater 16 is connected to the intermediate steam generator 17 through a deoxygenated water pipeline. The intermediate steam generator 17 is connected to the intermediate superheater 18 through a steam pipeline.

[0105] The deoxygenated water, after being preheated by the low-level preheater 13, is then pressurized by the low-pressure deoxygenated water booster pump 15, and undergoes intermediate preheating, intermediate evaporation, and intermediate superheating processes to produce steam at a different pressure.

[0106] Since the deoxygenated water between the low-stage preheater 13 and the low-stage evaporator is saturated, to avoid flash evaporation of the deoxygenated water due to pressure drop, steam from the cold side of the low-stage steam generator 19 must be used as pressure-stabilizing steam to the low-pressure deoxygenated water pressure stabilizing tank 14. This maintains the stable pressure of the deoxygenated water in the low-pressure deoxygenated water pressure stabilizing tank 14 and simultaneously reduces the head of the low-pressure deoxygenated water booster pump, thereby reducing the power consumption of the low-pressure deoxygenated water booster pump motor. Therefore, two steam pipelines can be led out from the steam outlet of the low-stage steam generator 19: one steam pipeline connects to the low-stage superheater 20, and the other steam pipeline connects to the low-pressure deoxygenated water pressure stabilizing tank 14.

[0107] As for the routing of the intermediate heat medium pipeline, the intermediate heat medium pipeline passes sequentially through the three-flash steam condenser 10, the two-flash steam condenser 9, and the second one-flash steam primary condenser 8. In the one-flash steam primary condenser 8, it splits into two paths. One path continues into the first one-flash steam primary condenser 8 and passes sequentially through the intermediate superheater 18, the intermediate steam generator 17, and the intermediate preheater 16. The other path merges with the intermediate heat medium pipeline that has passed through the intermediate preheater 16 and enters the low-level superheater 20. Then, it passes sequentially through the low-heat steam generator, the low-level preheater 13, and the ORC generator set, and finally returns to the starting end of the intermediate heat medium pipeline, realizing the recycling of the intermediate heat medium.

[0108] Taking a petrochemical company as an example, the above embodiments demonstrate their benefits in application. The company has eight gasifiers in its first and second phases, each producing approximately 400-500 t / h of black water at 240℃. Using the waste heat utilization technology of this invention, a single unit can produce 13.5 t / h of 0.4 MPaG steam and 19.5 t / h of 0.1 MPaG steam. The remaining intermediate heat medium heat is used to drive a refrigeration unit, generating approximately 8.62 MW of cooling capacity. The 0.1 MPaG steam is used to drive a steam turbine unit for power generation, with a power generation efficiency of up to 35% and a power generation capacity of up to 4.17 MW, generating an annual power generation benefit of 17.53 million yuan. The 0.4 MPaG steam annually is equivalent to 8158 tons of standard coal, with a current standard coal price of 305.7 yuan / ton, resulting in a benefit of 2.494 million yuan. The refrigeration capacity is equivalent to 8891.3 tons / year of standard coal, resulting in a benefit of 2.718 million yuan. The comprehensive economic benefit is 22.743 million yuan / year.

[0109] Comparing the economic benefits of ORC power generation technology, four gasifiers require one 9MW generator set, with a net power generation of 7050KW and an annual power generation benefit of 29.61 million yuan, equivalent to an annual power generation benefit of 7.4025 million yuan per gasifier. Compared with the comparative scheme, the present invention has a significant advantage in terms of overall economic benefits.

[0110] In summary, during operation, the intermediate heat medium circulates between the flash steam from the black water at each stage and the heat exchange equipment for the deoxygenated water at each stage. It continuously extracts latent heat from the flash steam and transfers the extracted heat to the deoxygenated water, producing superheated steam. This superheated steam can be integrated into the plant's steam network for external heating, or it can drive a steam turbine to generate electricity or a refrigeration unit for cooling. Through these methods, the waste heat from the black water is fully utilized. The system employs multi-stage flash evaporation, intermediate heat medium heat extraction, and clean superheated steam production, resulting in high system reliability, stable operation, and the production of high-grade superheated steam. This maximizes energy conservation and carbon reduction benefits. The system utilizes black water, a relatively polluted heat source, as an energy source to achieve combined heat and power (CHP), representing an innovative approach.

[0111] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water, characterized in that, Includes the following steps: High-temperature black water is subjected to at least one stage of flash evaporation to obtain black water flash steam at the corresponding temperature; The intermediate heat medium is heated by using the steam produced by black water flash evaporation as a heat source in an indirect heat exchange manner to obtain an intermediate heat medium at a first predetermined temperature. The deaerator effluent is sent out through a deaerator water booster pump. After being preheated by a preheater, it is divided into two streams. The first stream of deaerator water is exchanged with an intermediate heat medium at a first predetermined temperature to obtain superheated or saturated steam at the first predetermined temperature and an intermediate heat medium at a second predetermined temperature. The second deoxygenated water is exchanged with an intermediate heat medium at a second predetermined temperature to obtain superheated or saturated steam at the second predetermined temperature.

2. The method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 1, characterized in that: High-temperature black water is subjected to at least one stage of flash evaporation to obtain black water flash steam at the corresponding temperature, including: High-temperature black water is flashed through multiple flash tanks in stages to obtain black water flash steam at the corresponding temperature; The black water flash steam obtained from each stage of flash evaporation is fed into the corresponding steam condenser to exchange heat with the intermediate heat medium and condense. The black water after the end flash evaporation is subjected to vacuum flash evaporation, and the black water flash evaporation vapor after vacuum flash evaporation enters the gas-liquid separator for gas-liquid separation. The final separated ash water is fed into an ash water tank, while the non-condensable gas is discharged using a vacuum pump. Finally, the flash-evaporated black water is pumped into a slag water tank for treatment.

3. The method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 2, characterized in that: The ash water obtained after the flash steam of each level of black water is condensed by heat exchange in the corresponding steam condenser is fed into a cooler for cooling. The cooled ash water is then fed into a gas-liquid separator for gas-liquid separation. The separated ash water is fed into an ash water tank, and the separated acidic gases are centrally processed.

4. The method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 3, characterized in that: The intermediate heat medium is heated indirectly by using steam produced from black water flash evaporation as a heat source to obtain an intermediate heat medium at a first predetermined temperature, comprising: An intermediate heat medium pressure stabilizing tank is installed at the intermediate heat medium inlet, and steam at a certain pressure is introduced into the intermediate heat medium pressure stabilizing tank for pressure stabilization and regulation. Combined with the intermediate heat medium booster pump set, the intermediate heat medium pipeline is pressurized. After the intermediate heat medium is introduced into the last stage steam condenser to exchange heat with the black water flash steam at the corresponding temperature, it exchanges heat with black water flash steam at different temperatures in each stage. The intermediate heat medium is obtained at the second predetermined temperature midway, and heat exchange continues to obtain the intermediate heat medium at the first predetermined temperature.

5. The method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 4, characterized in that: The deaerator effluent is pumped out via a deaerator booster pump, preheated in a preheater, and then divided into two streams. The first stream of deaerator water exchanges heat with an intermediate heat medium at a first predetermined temperature to obtain superheated or saturated steam at the first predetermined temperature and an intermediate heat medium at a second predetermined temperature, including: The first deoxygenated water pipeline is connected to a low-pressure deoxygenated water pressure stabilizing tank. Steam at a certain pressure is introduced into the low-pressure deoxygenated water pressure stabilizing tank for pressure stabilization and regulation. Combined with the low-pressure deoxygenated water booster pump, the deoxygenated water is pressurized. The pressurized deoxygenated water passes sequentially through an intermediate preheater, an intermediate steam generator, and an intermediate superheater to obtain superheated or saturated steam at a first predetermined temperature. Meanwhile, the intermediate heat medium at the first predetermined temperature passes sequentially through the intermediate superheater, the intermediate steam generator, and the intermediate preheater to exchange heat with the deoxygenated water, thereby obtaining an intermediate heat medium at a second predetermined temperature.

6. The method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 5, characterized in that: The second deoxygenated water is exchanged with an intermediate heat medium at a second predetermined temperature to obtain superheated or saturated steam at the second predetermined temperature, including: The second deoxygenated water passes sequentially through a low-level steam generator and a low-level superheater. The steam generated by the low-level steam generator is divided into two paths. One path enters the low-level superheater for heating to obtain superheated or saturated steam at a second predetermined temperature. The other path enters a low-pressure deoxygenated water pressure stabilizing tank, which, in conjunction with a low-pressure deoxygenated water booster pump, pressurizes the first path of deoxygenated water. The intermediate heat medium at the second predetermined temperature then passes through the low-stage superheater and the low-stage steam generator in sequence to obtain the intermediate heat medium at the third predetermined temperature. The intermediate heat medium at the third predetermined temperature is introduced into the low-level preheater to exchange heat with the deoxygenated water delivered by the deoxygenated water booster pump.

7. The method for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 1, characterized in that: The intermediate heat medium passing through the low-level preheater is connected to the ORC generator set or refrigeration unit, and the intermediate heat medium passing through the ORC generator set or refrigeration unit is connected to the starting point of the intermediate heat medium pipeline.

8. A system for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water, characterized in that, Includes a black water flash heat exchange unit and a heat utilization unit; The black water flash heat exchange unit includes at least one flash tank, at least one steam condenser, at least one gas-liquid separator (5), an intermediate heat medium pipeline, and an intermediate heat medium booster pump group (7). The steam outlet of the flash tank is connected to the inlet of the steam condenser through the steam pipeline, the intermediate heat medium pipeline is connected to the steam condenser, and the gray water outlet of the steam condenser and the steam outlet of the end flash tank are respectively connected to the corresponding gas-liquid separator (5). The heat utilization unit includes a deoxygenated water booster pump (12), a low-level preheater (13), a primary heat recovery section and a secondary heat recovery section. The deoxygenated water booster pump is connected to the low-level preheater (13) through a deoxygenated water pipeline. The deoxygenated water pipeline connected to the outlet of the low-level preheater (13) is divided into two paths, one of which is connected to the primary heat recovery section and the other of which is connected to the secondary heat recovery section. The primary heat recovery unit includes a low-level superheater (20) and a low-level steam generator (19). A deoxygenated water pipeline passing through the low-level preheater (13) is connected to the low-level steam generator (19). The steam outlet of the low-level steam generator (19) is connected to the low-level superheater (20) through a steam pipeline. The intermediate heat recovery unit includes a low-pressure deoxygenated water pressure stabilizing tank (14), a low-pressure deoxygenated water booster pump (15), an intermediate preheater (16), an intermediate steam generator (17), and an intermediate superheater (18). Another deoxygenated water pipeline passing through the low-pressure preheater (13) is connected to the low-pressure deoxygenated water booster pump (15) and connected to the low-pressure deoxygenated water pressure stabilizing tank (14). The low-pressure deoxygenated water booster pump (15) is connected to the intermediate preheater (16) through the deoxygenated water pipeline. The intermediate preheater (16) is connected to the intermediate steam generator (17) through the deoxygenated water pipeline. The intermediate steam generator (17) is connected to the intermediate superheater (18) through the steam pipeline. The steam outlet of the low-level steam generator (19) leads to two steam pipelines. One steam pipeline is connected to the low-level superheater (20), and the other steam pipeline is connected to the low-pressure deoxygenated water pressure stabilizing tank (14).

9. A system for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 8, characterized in that: There are four flash tanks: a primary medium-pressure flash tank (1), a secondary low-pressure flash tank (2), a tertiary low-pressure flash tank (3), and a vacuum flash tank (4). There are four steam condensers: two primary flash steam condensers (8), one secondary flash steam condenser (9), and one tertiary flash steam condenser (10). The steam outlet of the primary medium-pressure flash tank (1) is connected in parallel to a pair of primary flash steam condensers (8) via a steam pipeline. The condensate outlet of the primary medium-pressure flash tank (1) is connected to the secondary low-pressure flash tank (2). The steam outlet of the secondary low-pressure flash tank (2) is connected to the secondary... The condensate outlet of the flash condenser (9) and the secondary low-pressure flash tank (2) is connected to the tertiary low-pressure flash tank (3). The steam outlet of the tertiary low-pressure flash tank (3) is connected to the third flash condenser (10) through a steam pipeline. The condensate outlet of the tertiary low-pressure flash tank (3) is connected to the vacuum flash tank (4). The steam outlet of the vacuum flash tank (4) is connected to the corresponding gas-liquid separator (5) through a steam pipeline. The ash water outlets of the first flash condenser (8), the second flash condenser (9) and the third flash condenser (10) are respectively connected to the corresponding gas-liquid separator (5) through a cooler (11).

10. A system for producing low-pressure superheated or saturated steam from waste heat of coal gasification black water according to claim 9, characterized in that: The intermediate heat medium pipeline is connected end to end. The intermediate heat medium pressure tank (6) is also connected to the end of the connection point of the intermediate heat medium pipeline. The intermediate heat medium pipeline passes through the three-flash steam condenser (10), the two-flash steam condenser (9), and the second one-flash steam primary condenser (8) in sequence. It splits into two paths in the one-flash steam primary condenser (8). One path continues into the first one-flash steam primary condenser (8) and passes through the intermediate superheater (18), the intermediate steam generator (17), and the intermediate preheater (16) in sequence. The other path merges with the intermediate heat medium pipeline that passed through the intermediate preheater (16) and enters the low-level superheater (20). It then passes through the low-level steam generator (19), the low-level preheater (13), the ORC generator set in sequence, and finally returns to the beginning of the intermediate heat medium pipeline.

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