A steam generating device applied to a zero liquid discharge system of a coal-fired power plant

Abstract

The present invention is a steam generating device applied to a zero - discharge system for wastewater in a coal - fired power plant. The makeup water tank is provided with a water outlet, and the water outlet is arranged at the bottom of the makeup water tank and is connected to the inlet of the steam generating device through a makeup water pump. A flue gas inlet is arranged on the shell of the steam generating device, and the flue gas inlet is connected to the outlet of a booster fan through a pipeline, leading the low - temperature flue gas at the outlet of the booster fan into the steam generating device. The first outlet of the steam generating device is connected to a flash evaporation device, and the second outlet of the steam generating device is connected to a desulfurization absorption tower. The flash evaporation device includes a flash evaporation tank. The first outlet is a superheated water outlet and is connected to the flash evaporation tank through a pipeline. The top of the flash evaporation tank is connected to a vacuum pump. The flash evaporation tank is provided with a steam outlet, and the steam outlet is connected to an evaporation and concentration system through a steam compressor. The evaporation and concentration system is provided with a water outlet, and the water outlet of the evaporation and concentration system is connected to the makeup water tank through a pipeline.

Description

Technical Field

[0001] The present invention relates to the technical field of steam generating devices, and particularly to a steam generating device applied to a zero-discharge system for wastewater in coal-fired power plants. Background Art

[0002] In the zero-discharge system for wastewater in coal-fired power plants, the users of steam are generally evaporation and concentration systems. The commonly used evaporation and concentration system process is the multi-effect evaporation process, which has the advantages of continuous operation, simple operation, and less maintenance, but requires continuous replenishment of steam as a heat source.

[0003] In coal-fired power plants, low-pressure steam is mainly extracted from the steam drum. The common low-pressure steam parameters are superheated steam at 1.2 MPa and 300 °C, and a temperature and pressure reduction device is required to reduce the temperature and pressure of the steam to saturated steam at about 0.2 MPa and 120 °C for use as the heat source of the multi-effect evaporator. However, this is for the precious steam resources of coal-fired power plants, and the temperature and pressure reduction device also reduces the calorific value of the original superheated steam, and the thermal energy of the original superheated steam cannot be effectively utilized. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the present invention provides a steam generating device applied to a zero-discharge system for wastewater in coal-fired power plants, using the waste heat of the flue gas at the end of the coal-fired power plant as the heat source, and finally generating low-pressure steam for the zero-discharge system of wastewater, achieving the purpose of "treating waste with waste".

[0005] A steam generating device applied to a zero-discharge system for wastewater in coal-fired power plants includes a makeup water tank. The makeup water tank is provided with a water outlet, and the water outlet is arranged at the bottom of the makeup water tank and is connected to the inlet of the steam generating device through a makeup water pump. A flue gas inlet is arranged on the shell of the steam generating device, and the flue gas inlet is connected to the outlet of a booster fan through a pipeline to introduce the low-temperature flue gas at the outlet of the booster fan into the steam generating device. The first outlet of the steam generating device is connected to a flash evaporation device, and the second outlet of the steam generating device is connected to a desulfurization absorption tower. The flash evaporation device includes a flash evaporation tank. The first outlet is a superheated water outlet and is connected to the flash evaporation tank through a pipeline. The top of the flash evaporation tank is connected to a vacuum pump. The flash evaporation tank is provided with a steam outlet, and the steam outlet is connected to an evaporation and concentration system through a steam compressor. The evaporation and concentration system is provided with a water outlet, and the water outlet of the evaporation and concentration system is connected to the makeup water tank through a pipeline.

[0006] Furthermore, for the steam generating device of the zero-discharge system for wastewater, the steam generating device is a shell-and-tube heat exchanger or a finned-tube heat exchanger, and the heat exchanger material is one or a combination of several of carbon steel, stainless steel, copper alloy, aluminum alloy, titanium alloy, nickel-based material, and Hastelloy.

[0007] Further, for the steam generating device of the zero liquid discharge system, the shell and tube heat exchanger includes a cylindrical shell, and heat exchange tubes are arranged inside the shell. The heat exchange tubes are smooth seamless spiral tubes, with an outer diameter ranging from 10 to 57 mm and a wall thickness of 0.5 to 4.0 mm. Inside the shell, there are successively an insulation layer and an anti-corrosion layer.

[0008] Further, for the steam generating device of the zero liquid discharge system, the finned tube heat exchanger includes a shell, and finned tubes and smooth seamless tubes arranged inside the shell. The finned tubes include transverse fins and longitudinal fins, and the transverse fins and longitudinal fins are installed on the outer surface of the smooth seamless tube. The thickness of the transverse fins and longitudinal fins is 0.5 to 5 mm, the height is 1 to 50 mm, and the spacing between the transverse fins and longitudinal fins is 1 to 50 mm. The outer diameter of the smooth seamless tube is 10 to 57 mm, and the wall thickness is 0.5 to 4 mm.

[0009] Further, for the steam generating device of the zero liquid discharge system, the system includes a control device, and the control device is connected to a make-up water tank, a steam generating device, a booster fan, a flash evaporation device, and a vacuum pump through circuits.

[0010] Further, for the steam generating device of the zero liquid discharge system, the water inlet of the make-up water tank is connected to the evaporated concentrated water and the boiler make-up water. A liquid level gauge is arranged in the make-up water tank, and a solenoid valve is connected to the water inlet of the make-up water tank. The liquid level gauge and the solenoid valve are connected to the control device. The liquid level gauge transmits the detected liquid level information to the control device. When the liquid level gauge detects that the water level in the make-up water tank is lower than the set value, the control device controls the solenoid valve to open to supply water into the make-up water tank.

[0011] Further, for the steam generating device of the zero liquid discharge system, an air extraction hole is opened at the top of the flash evaporation tank, and the air extraction hole is connected to the vacuum pump through an air delivery pipe. The outer wall of the flash evaporation tank is wrapped with a heat insulation layer. The inside of the flash evaporation tank is in a negative pressure state, with a pressure of -98.5 to 0 kPa. A vacuum control valve is arranged between the air delivery pipe and the flash evaporation tank, and the vacuum control valve is connected to the control device. When the absolute vacuum pressure in the flash evaporation tank is -98.5 kPa, the control device controls to simultaneously close the vacuum control valve and the vacuum pump; when the absolute vacuum pressure in the flash evaporation tank is 0 kPa, the control device controls to simultaneously open the vacuum control valve and the vacuum pump.

[0012] Further, for the steam generating device of the zero liquid discharge system for wastewater, the evaporation and concentration system includes the evaporation and concentration device itself, which includes an evaporator, a preheater and a separator arranged on both sides of the evaporator. The preheater is provided with a steam inlet connected to a steam compressor. The evaporator, the preheater and the separator are connected by pipelines. Steam enters the preheater from the steam inlet of the preheater, enters the evaporator through the pipeline from the preheater, enters the separator through the evaporator. The separator is provided with a water outlet, and the water outlet is connected to a makeup water tank through a pipeline.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. The present invention solves well the problem that a large amount of external steam needs to be supplemented in a conventional zero liquid discharge system for wastewater without affecting the boiler efficiency of a coal-fired power plant. It is an ideal steam generation process route for zero liquid discharge of wastewater. The heat source used is the waste heat of the flue gas at the end of a coal-fired power plant, and finally low-pressure steam available for the zero liquid discharge system for wastewater is generated, achieving the purpose of "treating waste with waste".

[0015] 2. The present invention can cope with the different amounts of low-pressure steam required for the zero liquid discharge system to treat different water qualities and water volumes, ensure the stable operation of the whole system, and at the same time can treat waste with waste to meet the design requirements of resource reuse and environmental friendliness, and has a wide application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] Embodiment 1:

[0019] As Figure 1As shown in the figure, a steam generating device applied to a zero-discharge system for waste water in a coal-fired power plant includes a makeup water tank 4. The makeup water tank is provided with a water outlet, and the water outlet is arranged at the bottom of the makeup water tank 4 and is connected to the inlet of the steam generating device 6 through a makeup water pump 5. A flue gas inlet is arranged on the shell of the steam generating device, and the flue gas inlet is connected to the outlet of a booster fan 1 through a pipeline to introduce the low-temperature flue gas at the outlet of the booster fan into the steam generating device. The first outlet of the steam generating device is connected to a flash evaporation device 7, and the second outlet of the steam generating device is connected to a desulfurization absorption tower 10. The flash evaporation device includes a flash evaporation tank. The first outlet is a superheated water outlet and is connected to the flash evaporation tank through a pipeline. The top of the flash evaporation tank is connected to a vacuum pump 9. The flash evaporation tank is provided with a steam outlet, and the steam outlet is connected to an evaporation and concentration system through a steam compressor. The evaporation and concentration system 8 is provided with a water outlet, and the water outlet of the evaporation and concentration system is connected to the makeup water tank through a pipeline.

[0020] Further, for the steam generating device of the zero-discharge system for waste water, the heat source used by the steam generating system is the low-temperature flue gas after the booster fan and before the desulfurization absorption tower in the coal-fired power plant, and its temperature is 70 - 120 °C. The medium passing through the steam generating device is the effluent of the boiler makeup water treatment system in the coal-fired power plant / the condensate recovered by condensing the steam flashed by this system in the subsequent evaporation and concentration system.

[0021] Further, for the steam generating device of the zero-discharge system for waste water, the steam generating device is a shell-and-tube heat exchanger or a finned-tube heat exchanger, and the heat exchanger material is a combination of one or more of carbon steel, stainless steel, copper alloy, aluminum alloy, titanium alloy, nickel-based material, and Hastelloy.

[0022] Further, for the steam generating device of the zero-discharge system for waste water, the shell-and-tube heat exchanger includes a cylindrical shell, and heat exchange tubes are arranged inside the shell. The heat exchange tubes are smooth seamless spiral tubes, with an outer diameter range of 10 - 57 mm and a wall thickness of 0.5 - 4.0 mm. The inside of the shell sequentially includes a heat insulation layer and an anti-corrosion layer. By setting the smooth seamless spiral tubes, the problem of thermal expansion of the heat exchange tubes is solved, and the service life of the shell-and-tube heat exchanger is improved. By setting the spiral tubes, the heat exchange area can be increased, thereby greatly improving the heat exchange effect and making more efficient use of energy, which has a relatively positive effect in the field of heat exchange. By setting the heat insulation layer, the sensible heat loss is reduced, and the sensible heat utilization rate is improved. By setting the anti-corrosion layer, the corrosion of harmful substances to the heat exchanger is reduced, the anti-corrosion ability of the heat exchanger is increased, and the service life of the heat exchanger is increased.

[0023] Further, for the steam generating device of the zero liquid discharge system for wastewater, the finned tube heat exchanger includes a housing, and finned tubes and smooth seamless tubes arranged inside the housing. The finned tubes include transverse fins and longitudinal fins. The transverse fins and longitudinal fins are installed on the outer surface of the smooth seamless tubes. The thickness of the transverse fins and longitudinal fins is 0.5 - 5 mm, the height is 1 - 50 mm, the distance between the transverse fins and the longitudinal fins is 1 - 50 mm, the outer diameter of the smooth seamless tube is 10 - 57 mm, and the wall thickness is 0.5 - 4 mm.

[0024] Further, for the steam generating device of the zero liquid discharge system for wastewater, the system includes a control device. The control device is connected to a make-up water tank, a steam generating device, a booster fan, a flash evaporation device, and a vacuum pump through circuits, and controls the operation and stop of the make-up water tank, the steam generating device, the booster fan, the flash evaporation device, and the vacuum pump.

[0025] Further, for the steam generating device of the zero liquid discharge system for wastewater, the water inlet of the make-up water tank 4 is connected to the evaporated concentrated water 2 and the boiler make-up water 3. A liquid level gauge is arranged in the make-up water tank, and a solenoid valve is connected to the water inlet of the make-up water tank. The liquid level gauge and the solenoid valve are connected to the control device. The liquid level gauge detects the liquid level in the make-up water tank, and then remotely transmits the detected liquid level signal to the centralized control device. The upper and lower limit values of the liquid level in the pressure stabilizing make-up water tank are set through the control device. When the liquid level gauge detects that the water level in the make-up water tank is lower than the set minimum value, the control device controls the solenoid valve to open to supply water into the make-up water tank. When the liquid level gauge detects that the water level in the make-up water tank is higher than the set maximum value, the control device controls the solenoid valve to close to stop the water supply into the make-up water tank, so as to achieve the purpose of automatic water supply. When the liquid level in the make-up water tank is within the range of the upper and lower limit values, it indicates that the make-up water tank is operating normally, and the water supply into the make-up water tank is stopped. When the liquid level in the tank is lower than the lower limit value, it indicates that the make-up water tank is short of water, and the control device automatically controls the program to run and opens the water source to supply water into the make-up water tank. When operating normally, the design of the liquid level gauge ensures the stable pressure in the make-up water tank.

[0026] Further, for the steam generating device of the zero liquid discharge system for wastewater, an air extraction hole is opened at the top of the flash evaporation tank. The air extraction hole is connected to the vacuum pump through an air delivery pipe. The outer wall of the flash evaporation tank is wrapped with a heat insulation layer. The inside of the flash evaporation tank is in a negative pressure state, and its pressure is -98.5 - 0 kPa. A vacuum control valve is arranged between the air delivery pipe and the flash evaporation tank. The vacuum control valve is connected to the control device. When the absolute vacuum pressure in the flash evaporation tank is -98.5 kPa, the control device controls to simultaneously close the vacuum control valve and the vacuum pump. When the absolute vacuum pressure in the flash evaporation tank is 0 kPa, the control device controls to simultaneously open the vacuum control valve and the vacuum pump. A demister is also arranged inside the flash evaporation tank. The demister is used to remove the foam in the flash evaporation tank. The demister is connected to the control device. When the vacuum control valve is opened, the control device controls the demister to open.

[0027] Furthermore, for the steam generating device of the zero liquid discharge system, the evaporation and concentration system includes the evaporation and concentration device itself, and the evaporation and concentration device itself includes an evaporator, a preheater and a separator arranged on both sides of the evaporator. The preheater is provided with a steam inlet connected to a steam compressor. The evaporator, the preheater and the separator are connected by pipelines. Steam enters the preheater from the steam inlet of the preheater, enters the evaporator through the pipeline from the preheater, enters the separator through the evaporator, and the separator is provided with a water outlet, and the water outlet is connected to a make-up water tank through a pipeline. The steam entering from the steam inlet is low-pressure saturated steam, with a pressure of: 25 - 200 kPa and a temperature of: 65 - 120 °C.

[0028] The above description shows and describes the preferred embodiments of the present invention. As mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the inventive concept described herein through the above teachings or the techniques or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A steam generating device applied to a zero liquid discharge system of a coal-fired power plant, characterized in that: It includes a water replenishing tank (4). The water replenishing tank is provided with a water outlet which is arranged at the bottom of the water replenishing tank and is connected to the inlet of a steam generating device (6) through a water replenishing pump (5). A flue gas inlet is arranged on the shell of the steam generating device. The flue gas inlet is connected to the outlet of a booster fan (1) through a pipeline, and the low-temperature flue gas at the outlet of the booster fan is led into the steam generating device. The first outlet of the steam generating device is connected to a flash evaporation device (7), and the second outlet of the steam generating device is connected to a desulfurization absorption tower (10). The flash evaporation device includes a flash evaporation tank. The first outlet is a superheated water outlet, and the superheated water outlet is connected to the flash evaporation tank through a pipeline. The top of the flash evaporation tank is connected to a vacuum pump (9). The flash evaporation tank is provided with a steam outlet, and the steam outlet is connected to an evaporation and concentration system (8) through a steam compressor. The evaporation and concentration system is provided with a water outlet, and the water outlet of the evaporation and concentration system is connected to the water replenishing tank through a pipeline; The water inlet of the water replenishing tank (4) is connected to evaporation concentrated water (2) and boiler make-up water (3). A liquid level gauge is arranged in the water replenishing tank. The water inlet of the water replenishing tank is connected with a solenoid valve. The liquid level gauge and the solenoid valve are connected to a control device. The liquid level gauge transmits the detected liquid level information to the control device. When the liquid level gauge detects that the water level in the water replenishing tank is lower than the set value, the control device controls the solenoid valve to open to supply water into the water replenishing tank; An air extraction hole is opened at the top of the flash evaporation tank. The air extraction hole is connected to the vacuum pump through an air delivery pipe. The outer wall of the flash evaporation tank is wrapped with a heat insulation layer. The inside of the flash evaporation tank is in a negative pressure state, and its pressure is -98.5 - 0 kPa. A vacuum control valve is arranged between the air delivery pipe and the flash evaporation tank. The vacuum control valve is connected to the control device. When the absolute vacuum pressure in the flash evaporation tank is -98.5 kPa, the control device controls to simultaneously close the vacuum control valve and the vacuum pump; when the absolute vacuum pressure in the flash evaporation tank is 0 kPa, the control device controls to simultaneously open the vacuum control valve and the vacuum pump; The evaporation and concentration system includes an evaporation and concentration device. The evaporation and concentration device includes an evaporator, a preheater and a separator arranged on both sides of the evaporator. The preheater is provided with a steam inlet connected to the steam compressor. The evaporator, the preheater and the separator are connected by pipelines. Steam enters the preheater from the steam inlet of the preheater, enters the evaporator through the pipeline from the preheater, enters the separator through the evaporator. The separator is provided with a water outlet, and the water outlet is connected to the water replenishing tank through a pipeline.

2. The steam generating device applied to the zero discharge system of the waste water of a coal-fired power plant according to claim 1, wherein: The steam generating device is a shell-and-tube heat exchanger or a finned-tube heat exchanger. The heat exchanger material is a combination of one or more of carbon steel, stainless steel, copper alloy, aluminum alloy, titanium alloy, and nickel-based materials.

3. The steam generating device applied to the zero liquid discharge system of a coal-fired power plant according to claim 2, wherein: The shell-and-tube heat exchanger includes a cylindrical shell. Heat exchange tubes are arranged in the shell. The heat exchange tubes are smooth seamless spiral tubes, with an outer diameter range of 10 - 57 mm and a wall thickness of 0.5 - 4.0 mm. The inside of the shell sequentially includes a heat insulation layer and an anti-corrosion layer.

4. The steam generating device applied to the zero - discharge system of coal - fired power plant wastewater according to claim 3, wherein: The finned tube heat exchanger includes a shell, and finned tubes and smooth seamless tubes arranged inside the shell. The finned tubes include transverse fins and longitudinal fins. The transverse fins and longitudinal fins are installed on the outer surface of the smooth seamless tube. The thickness of the transverse fins and longitudinal fins is 0.5 - 5 mm, the height is 1 - 50 mm, the spacing between the transverse fins and longitudinal fins is 1 - 50 mm. The outer diameter of the smooth seamless tube is 10 - 57 mm, and the wall thickness is 0.5 - 4 mm.

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