Low-flash steam waste heat utilization system for slag water of coal water slurry gasification furnace

Abstract

The utility model discloses a water-coal-slurry gasification furnace slag water low-flash steam waste heat utilization system, which relates to the technical field of distillation or gas-liquid medium generation exchange, and comprises a low-pressure flash tank, the gas outlet end of the low-pressure flash tank is connected with a waste heat boiler, and flash steam of the low-pressure flash tank is used for heating the waste heat boiler; a steam outlet of the waste heat boiler is connected with a steam turbine, the steam turbine is connected with a generator and used for driving the generator to generate electricity, and a condensate outlet of the waste heat boiler is connected with a condensate tank. A black water recycling pipe is arranged at the bottom of the low-pressure flash tank, is used for recycling black water, and is communicated with the clarifying tank; and the recovery pump is communicated with the ash water tank and is used for pumping the ash condensate into the gasification furnace for cyclic utilization. The low-flash steam is utilized to drive the steam turbine to drag the asynchronous motor to generate electricity, the comprehensive energy utilization rate of the gasification device is improved, and emission reduction and efficiency improvement of the system are achieved. By implementing the low-flash steam waste heat utilization project of the gasification device, the heat of the flash steam is successfully recovered, and the resource waste is avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of distillation or gas-liquid medium exchange, and in particular relates to a water-coal slurry gasification furnace slag water true flash steam waste heat utilization system. Background Art

[0002] The main process for treating slag water in the flash evaporation unit of a water-coal slurry gasifier consists of a cyclone separator, a scrubber, and an evaporative hot water tower. The depressurized black water flashes in the evaporation chamber of the evaporative hot water tower, rapidly dispersing water vapor and some dissolved acid gases. The water vapor then flows through a riser into the upper hot water chamber of the evaporative hot water tower, where it undergoes direct heat exchange with ash water delivered by the low-pressure ash water pump, deoxygenated water delivered by the deoxygenated water booster pump, low-temperature condensate from the conversion system, and condensate from the water-gas conveyor. The water then flows into the high-temperature hot water storage tank.

[0003] The flash steam at the top of the evaporative hot water tower passes through a pressure regulating valve to the stripping tower in the conversion zone as supplementary steam; the other route enters the acid gas condenser. After the acid gas is condensed, it enters the acid gas separator for gas-liquid separation, and then passes through a pressure regulating valve to be incorporated into the flare pipe network for combustion. The acid condensate at the bottom of the acid gas separator is regulated by a liquid level regulating valve and sent to the ash water tank; the black water after preliminary concentration at the bottom of the evaporative hot water tower is controlled by a liquid level regulating valve and sent to the low-pressure flash tank.

[0004] Black water entering the low-pressure flash tank undergoes flash evaporation at low pressure. The flashed gas exits the low-pressure flash tank to deaerator for heating. If the deaerator temperature exceeds the limit, the flash steam is transferred to the low-pressure flash condenser for heat exchange and cooling. It then enters the low-pressure flash separator, where the separated gas is discharged to a safe location. The condensate at the bottom of the low-pressure flash separator flows by gravity into the gray water tank.

[0005] Since the flashed gas is used as heating steam for the deaerator in the low-pressure flash tank after flash evaporation, if the deaerator temperature exceeds the limit, the flash steam is sent to the low-pressure flash condenser for heat exchange and cooling. On the one hand, this causes heat loss and energy waste. On the other hand, due to its poor water quality, it causes long-term blockage of the low-pressure flash cooler, poor heat exchange effect, and affects the long-term stable operation of the entire slag water system. Similar devices have not effectively utilized this part of the heat. Therefore, it is necessary to design a water-coal slurry gasification furnace slag water true flash steam waste heat utilization system to solve the above problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to propose a water-coal slurry gasification furnace slag water true flash steam waste heat utilization system, which solves the problems of large heat loss, poor energy utilization rate and poor water quality in the water-coal slurry gasification furnace slag in the prior art, which easily blocks the machine and leads to poor overall heat exchange effect and affected operation stability. The utility model has the characteristics of improving the comprehensive energy utilization rate of the gasification device, realizing emission reduction and efficiency improvement of the system, successfully recovering the heat of the flash steam, and avoiding waste of resources.

[0007] In order to solve the above technical problems, the technical solutions adopted in this application are:

[0008] The waste heat utilization system of slag water flash steam from water-coal slurry gasification furnace includes a low-pressure flash tank, the gas outlet of the low-pressure flash tank is connected to a waste heat waste boiler, and the flash steam from the low-pressure flash tank heats the waste heat waste boiler; the steam outlet of the waste heat waste boiler is connected to a steam turbine, which is connected to a generator to drive the generator to generate electricity, and the condensate outlet of the waste heat waste boiler is connected to a condensate tank;

[0009] A black water recovery pipe is set at the bottom of the low-pressure flash tank and connected to the external clarification tank for recycling black water; the water outlet at the bottom of the waste heat waste boiler is connected to the ash water tank, the ash water tank is connected to the recovery pump, and the other end of the recovery pump is connected to the gasifier to pump the ash condensate into the gasifier for recycling.

[0010] Preferably, the gas outlet end of the low-pressure flash tank is connected to the flash condenser, and the condensate of the flash condenser is connected to the low-pressure flash separator through a pipeline.

[0011] Preferably, an electric valve is installed at the inlet of the flash condenser to control the low-pressure flash steam to enter the flash condenser.

[0012] Preferably, a circulating water pipeline is provided on the flash condenser for cooling the condensation of the flash condenser, and a regulating valve is installed on the circulating water return pipe of the flash condenser.

[0013] Preferably, two waste heat waste boilers are provided and arranged in parallel, the air inlets of the two waste heat waste boilers are connected to the air outlet of the low-pressure flash tank, and the outlets of the two waste heat waste boilers are connected to the condensate tank.

[0014] Preferably, the condensate tank is equipped with a condensate pump.

[0015] Preferably, the steam turbine is connected to a fully condensing steam turbine for sending steam from the waste heat boiler to the fully condensing steam turbine to drive the generator to generate electricity.

[0016] Preferably, an emergency regulating valve is provided on the outlet gas phase pipeline of the low-pressure flash tank for emergency venting in case of failure of the fully condensing steam turbine.

[0017] Preferably, a steam expansion joint is installed at the inlet of the fully condensing steam turbine.

[0018] The beneficial effects of the utility model are:

[0019] This system uses low-flash steam to drive a steam turbine and asynchronous motor for power generation, improving the comprehensive energy utilization rate of the gasification unit and achieving system emissions reduction and efficiency improvement. The implementation of the gasification unit low-flash steam waste heat utilization project successfully recovers the heat from the flash steam, avoiding resource waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The equipment and connection diagram for the implementation of the utility model;

[0021] Figure 2 This is the overall structural system diagram of the utility model;

[0022] Figure 3 This is a system diagram of the low-pressure flash tank, waste heat boiler and generator of the utility model;

[0023] In the figure: 1. Low-pressure flash tank; 2. Waste heat waste boiler; 4. Generator; 5. Ash water tank; 6. Recovery pump; 7. Flash condenser. DETAILED DESCRIPTION

[0024] Example 1:

[0025] like Figure 1 As shown, the water-coal slurry gasification furnace slag water true flash steam waste heat utilization system includes a low-pressure flash tank 1, the gas outlet of the low-pressure flash tank 1 is connected to the waste heat waste boiler 2, and the flash steam of the low-pressure flash tank 1 heats the waste heat waste boiler 2; the steam outlet of the waste heat waste boiler 2 is connected to the steam turbine 4, and the steam turbine 4 is connected to the generator to drive the generator to generate electricity, and the condensate outlet of the waste heat waste boiler 2 is connected to the condensate tank;

[0026] A black water recovery pipe is provided at the bottom of the low-pressure flash tank 1 and is connected to an external clarification tank for recycling black water; the water outlet at the bottom of the waste heat waste boiler 2 is connected to the ash water tank 5, the ash water tank 5 is connected to the recovery pump 6, and the other end of the recovery pump 6 is connected to the gasifier for pumping the ash condensate into the gasifier for recycling.

[0027] Preferably, the gas outlet end of the low-pressure flash tank 1 is connected to the flash condenser 7, and the condensate of the flash condenser 7 is connected to the low-pressure flash separator 8 through a pipeline.

[0028] Preferably, an electric valve is installed at the inlet of the flash condenser 7 to control the low-pressure flash steam from entering the flash condenser 7 .

[0029] Preferably, a circulating water pipeline is provided on the flash condenser 7 for cooling the condensation of the flash condenser 7 , and a regulating valve is installed on the circulating water return pipe of the flash condenser 7 .

[0030] Preferably, two waste heat waste boilers 2 are provided and arranged in parallel, the air inlets of the two waste heat waste boilers 2 are connected to the air outlet end of the low-pressure flash tank 1, and the outlets of the two waste heat waste boilers 2 are connected to the condensate tank.

[0031] Preferably, the condensate tank is equipped with a condensate pump.

[0032] Preferably, the steam turbine 4 is connected to a fully condensing steam turbine for sending steam from the waste heat boiler 2 to the fully condensing steam turbine to drive a generator to generate electricity.

[0033] Preferably, an emergency regulating valve is provided on the outlet gas phase pipeline of the low-pressure flash tank 1 for emergency venting in case of failure of the fully condensing steam turbine.

[0034] Preferably, a steam expansion joint is installed at the inlet of the fully condensing steam turbine.

[0035] Example 2:

[0036] like Figure 2-Figure 3 As shown, this embodiment provides a water-coal slurry gasification furnace slag water low flash steam waste heat utilization system, including a low-pressure flash tank 1, the air outlet of the low-pressure flash tank 1 is connected to a flash condenser 7 through a pipeline, and the flash condenser 7 cools the flash steam; the condensate of the flash condenser 7 is connected to a low-pressure flash separator 8, that is, an atmospheric vacuum pump separator, through a pipeline, and the system vacuum degree is adjusted by the frequency conversion of the vacuum pump. After separation, the gas is discharged to a safe place to realize gas phase emptying; the condensate at the bottom of the flash condenser 7 is recovered by the low-pressure flash separator 8 to realize liquid phase recovery, and the liquid phase recovery means that the liquid flows into the ash water tank 5; the liquid at the bottom of the low-pressure flash tank 1 and the vacuum pump separator flows into the ash water tank by gravity, and the re-concentrated black water enters the clarification tank after being mixed with the flocculant in the static mixer.

[0037] The flash condenser 7 is provided with a circulating water pipe, which is used to cool the condensation of the flash condenser 7. A regulating valve is installed on the circulating water return pipe of the flash condenser 7. When the power generation load is adjusted, the steam can be cut off remotely to allow low-flash steam to enter the flash condenser 7, avoiding the low-flash overpressure safety valve from tripping due to untimely operation.

[0038] The existing system, consisting of the high-pressure flash tank 1, flash condenser 7, low-pressure flash separator, and vacuum pump, is described below as the original process. Black water entering the low-pressure flash tank undergoes flash evaporation at low pressure. The flashed gas exits the low-pressure flash tank and is used as heating steam in the deaerator. If the deaerator overheats, the flash steam is transferred to the low-pressure flash condenser for heat exchange and cooling. It then enters the low-pressure flash separator, where the separated gas is discharged to a safe location. The condensate at the bottom of the low-pressure flash separator flows by gravity into the gray water tank.

[0039] In this embodiment, the gas outlet end of the low-pressure flash tank 1 is also connected to two waste heat waste boilers 2 through a pipeline. The two waste heat waste boilers 2 are arranged in parallel. The condensate outlet of the waste heat waste boiler 2 is connected to a condensate tank through a pipeline. A condensate pump is installed in the condensate tank, and the condensate pump can pump away the condensate.

[0040] A water inlet pipe is installed on the waste heat boiler 2, which is connected to an external water supply device, such as a water pump. The water pump is used to transport desalinated water into the waste heat boiler 2. The steam in the low-pressure flash tank 1 can heat the water in the waste heat boiler 2 and generate steam.

[0041] The steam outlets of the two waste heat boilers 2 are connected to steam turbines 4 via pipes. Steam turbines 4 are fully condensing steam turbines, with their outputs fixedly connected to the inputs of electric motors for generating electricity. In other words, in this application, the fully condensing steam turbines are connected to the steam outlets of the two waste heat boilers 2, and the steam is used to drive the fully condensing steam turbines. The waste heat boilers 2 are preferably low-pressure waste heat boilers.

[0042] In addition, a valve is added before entering the true flash condenser 7, that is, an electric valve is added for isolation and standby. The low flash steam no longer flows to the true flash condenser 7, and the true flash steam (flash steam, pressure of about 0.2 MPa (A), temperature of about 133 ° C, single furnace flow rate of 30 t / h)) is led to the low-pressure waste heat waste boiler. The heat exchange area of ​​the low-pressure waste heat waste boiler is 1127 m2. Two units can generate 50 t / h of waste heat steam after leaving the waste boiler with a pressure of 0.127 MPa. The condensate of the waste heat boiler flows into the condensate tank through the pipeline. The condensate in the condensate tank is sent to the sedimentation tank through the condensate pump. The steam generated inside the waste heat boiler 2 is sent to the fully condensing steam turbine through the pipeline, and the steam turbine drives the generator to generate electricity.

[0043] An emergency regulating valve is installed on the gas phase pipeline at the outlet of the flash tank to vent the steam in the event of a turbine failure, allowing the low-pressure flash steam to be processed through the original process. After the flash steam waste heat utilization project is implemented, the low-pressure steam turbine system can replace the vacuum flash condensation and vacuum pumping system, enabling emergency switching in the event of a failure. This allows for a "one-in-operation, one-in-standby" vacuum flash system, ensuring stable operation of the gasification flash unit.

[0044] Through actual operational tests, the flash steam system operating pressure was 0.2 MPa(A), and the low-pressure flash condenser was shut down, improving the flash separation effect. The net power generation of the steam turbine generator set reached a maximum of 5 kW·h. The auxiliary power consumption of the steam turbine was approximately 1.3 kW·h. Assuming an annual turbine operating time of 8,000 hours and an electricity price of 0.67 yuan / kW·h, the annual economic benefit was 3.7 × 8,000 × 0.67 = 1.983 million yuan. Because the flash steam contains a high content of fine ash and has poor steam quality, unstable operating conditions were experienced during initial operation. By adding a regulating valve to the flash steam pipeline, the switching problem between the two systems was resolved. By adding a steam expansion joint at the inlet of the fully condensing steam turbine, the high vibration after turbine startup was resolved.

[0045] The primary heat loss in the slag water treatment unit of a water-coal slurry gasification plant occurs in the flash evaporation system. A waste heat power generation system has been added to the vacuum flash evaporation system, utilizing low-flash steam to drive a steam turbine, which in turn drives an asynchronous motor for power generation. This improves the comprehensive energy utilization rate of the gasification plant and achieves system-wide emission reduction and efficiency improvement. The implementation of the low-flash steam waste heat utilization project for the gasification plant successfully recovers the heat from the low-flash steam, avoiding resource waste. This breaks the conventional practice of using circulating water for cooling low-flash steam, which results in heat waste. By utilizing a fully condensing steam turbine for power generation, this technology for utilizing low-flash steam waste heat from pulverized coal gasification plants has been pioneered. This technology provides valuable insights and applications for both pressurized pulverized coal gasification plants and water-coal slurry gasification plants, and possesses promising application prospects. Furthermore, the vacuum pump system of the ultra-low-pressure steam turbine unit partially replaces the original vacuum flash evaporation system, ensuring emergency switching in the event of a fault, improving the operational stability of the gasification plant, and achieving significant economic and social benefits. In this embodiment, a recovery pump 6 is also provided, connected to the ash water tank 5, for pumping ash condensate into the gasifier for recycling.

Claims

1. A water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system, characterized by: The invention comprises a low-pressure flash tank (1), wherein the gas outlet of the low-pressure flash tank (1) is connected to a waste heat waste boiler (2), and the flash steam of the low-pressure flash tank (1) heats the waste heat waste boiler (2); the steam outlet of the waste heat waste boiler (2) is connected to a steam turbine (4), and the steam turbine (4) is connected to a generator; the condensate outlet of the waste heat waste boiler (2) is connected to a condensate tank; a black water recovery pipe is provided at the bottom of the low-pressure flash tank (1) and is connected to an external clarification tank; the water outlet end at the bottom of the waste heat waste boiler (2) is connected to an ash water tank (5), and the ash water tank (5) is connected to a recovery pump (6), and the other end of the recovery pump (6) is connected to a gasifier to pump the ash condensate into the gasifier for recycling.

2. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 1, characterized in that: The gas outlet end of the low-pressure flash tank (1) is connected to the flash condenser (7), and the condensate of the flash condenser (7) is connected to the low-pressure flash separator (8) through a pipeline.

3. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 2, characterized in that: An electric valve is installed at the inlet of the flash condenser (7).

4. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 3, characterized in that: The flash condenser (7) is provided with a circulating water pipeline, and a regulating valve is installed on the circulating water return pipe of the flash condenser (7).

5. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 3, characterized in that: Two waste heat waste boilers (2) are provided and arranged in parallel, the air inlets of the two waste heat waste boilers (2) are both connected to the air outlet end of the low-pressure flash tank (1), and the outlets of the two waste heat waste boilers (2) are both connected to a condensate tank.

6. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 5, characterized in that: The condensate tank is equipped with a condensate pump.

7. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 1, characterized in that: The steam turbine (4) is connected to a fully condensing steam turbine.

8. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 1, characterized in that: An emergency regulating valve is provided on the outlet gas phase pipeline of the low-pressure flash tank (1).

9. The water-coal slurry gasification furnace slag water low-flash steam waste heat utilization system according to claim 7, characterized in that: A steam expansion joint is installed at the inlet of the fully condensing steam turbine.

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