Flexible power generation cooperative waste treatment system for supercritical thermal power generating unit

Abstract

The invention discloses a supercritical thermal power generating unit flexible power generation cooperative waste treatment system. The system comprises a material conveying system, a supercritical water oxidation reaction system and a waste heat utilization system. According to the invention, supercritical water oxidation treatment of waste water is carried out by using residual steam generated by residual load of the boiler, harmless treatment of waste is carried out by using the residual steam while safe load operation of the boiler is ensured, energy in China is transformed to green and low carbon, and environmental protection is realized. And a feasible system scheme is provided for improving the safe operation of the deep peak regulation unit in China.

Description

Technical Field

[0001] The invention belongs to the field of coal-fired thermal power generation technology and supercritical water oxidation treatment technology, and in particular relates to a supercritical thermal power unit flexible power generation and coordinated waste treatment system. Background Art

[0003] Coal in power plants produces a large amount of coal slime wastewater, which needs to be efficiently and harmlessly treated. Supercritical water oxidation (SCWO) uses the unique physical and chemical properties of supercritical water to achieve efficient oxidation and degradation of toxic and harmful organic pollutants. Supercritical water oxidation can rely on the heat release of the reaction to maintain the heat balance of the system without the need for external heat supplementation; the equipment is small in size, safe, and meets the requirements of closedness. Supercritical water oxidation technology has shown great technical advantages in treating difficult-to-degrade, toxic and harmful organic matter. Summary of the invention

[0004] The purpose of the present invention is to achieve efficient and clean utilization of the residual load of the boiler and to ensure that the boiler operates under a safe load state while performing waste treatment of coal slime wastewater.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a supercritical thermal power unit flexible power generation and waste treatment system is designed, including a material conveying system, a supercritical water oxidation reaction system and a waste heat utilization system, wherein: The material conveying system includes a material blending tank, the outlet of the material blending tank is connected to the material conveying pump and the material inlet of the material preheater A in sequence, the material outlet of the material preheater A is connected to the material inlet of the material preheater B, and finally the material outlet of the material preheater B is connected to the material inlet of the reactor; wherein the heating medium of the material preheater B is the flue gas at the economizer outlet, and the flue gas at the economizer outlet is divided into two paths, the first path enters the air preheater to heat the oxygen required for combustion in the oxygen-enriched boiler, and the second path enters the material preheater B to heat the material, and the flue gas coming out of the air preheater and the material preheater B enters the tail flue gas waste heat utilization device; The supercritical water oxidation reaction system comprises a reactor, wherein the reactor is provided with a steam inlet, an oxidant inlet and a material inlet; wherein the steam inlet to the reactor comes from the outlet steam of an oxygen-enriched combustion boiler, a compressor is arranged before the oxidant inlet of the reactor, and the oxygen required for the reaction is extracted from the oxygen outlet of the air preheater and then pressurized by the compressor before entering the reactor; The waste heat utilization system includes a heat exchanger, the product inlet of the heat exchanger is connected to the product outlet of the reactor, the product outlet of the heat exchanger is connected to the product inlet of the material preheater A, and the product outlet of the material preheater A is connected to the gas-solid-liquid separation device; wherein the cooling medium of the heat exchanger is boiler condensate, and after the boiler condensate is heated, it comes out from the condensate outlet of the heat exchanger and enters the low-pressure heater, deaerator, high-pressure heater and economizer in sequence, and finally enters the boiler.

[0006] The present invention is further improved in that: The steam at the outlet of the oxygen-enriched combustion boiler is divided into two paths, one path enters the steam turbine for power generation, and the other path enters the reactor.

[0007] The heat for heating the material in the material preheater A is the waste heat of the supercritical water oxidation reaction product.

[0008] The compressor is driven by steam generated by the boiler.

[0009] The gas-solid-liquid separation device separates water, CO2 and residue, the separated water is returned to the material preparation tank, the CO2 is sealed, and the remaining residue of the reaction is collected and processed.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. Coordinated power generation and supercritical oxidation treatment of waste: When the boiler needs to reduce the power generation load, the boiler can be kept running at a stable and safe load, and the residual load steam at the boiler outlet, except for the steam turbine for power generation, can be used for supercritical water oxidation treatment of wastewater and sludge, and part of the imported oxygen of the oxygen-enriched combustion boiler can be used as the oxidant required for the supercritical water oxidation reaction. This method can not only maintain the boiler operating at a relatively safe, stable and economic load, reduce the variable load operation conditions of the unit, but also fully utilize the residual load to achieve efficient supercritical water oxidation treatment of organic waste coal sludge wastewater in the power plant while meeting the power supply load, generate certain economic benefits, reduce the operating cost of the deep peak-shaving power station boiler, and improve the safety of unit operation.

[0011] 2. Efficient utilization of waste heat: In the present invention, the waste heat of the product after supercritical water oxidation treatment is efficiently utilized in a graded manner. Among them, the first stage of waste heat utilization is to heat the boiler condensate, increase the temperature of the water in the low-pressure heater, reduce the steam extraction of the steam turbine, and improve the power generation efficiency of the boiler unit; the second stage of waste heat utilization is to preheat the material, reduce the heat absorption of the material in the reactor, and ensure the efficient supercritical water oxidation reaction in the reactor.

[0012] 3. The risk of low-temperature corrosion of the low-temperature heating surface of the unit is reduced: the temperature of the water in the low-pressure heater is increased by utilizing waste heat, thereby increasing the wall temperature of the economizer, avoiding low-temperature corrosion of the economizer tube wall, increasing the flue gas temperature at the economizer outlet, further reducing the amount of flue gas inlet to the air preheater, and reducing the risk of low-temperature corrosion and wear of the air preheater; the flue gas at the economizer outlet is divided into two paths, one path enters the air preheater to heat oxygen, and the other path enters the material preheater B to heat the material. Since the material preheater B has been preheated by the material preheater A, the wall temperature of the material preheater B is relatively high, which reduces the risk of low-temperature corrosion of the heating surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall structure of Example 1 of the present invention.

[0014] Among them, 1- low-pressure heater; 2- deaerator and high-pressure heater; 3- economizer; 4- air separator; 5- air preheater; 6- oxygen-enriched combustion boiler body; 7- compressor; 8- material mixing tank; 9- material conveying pump; 10- tail flue gas waste heat utilization device; 11- material preheater A; 12- material preheater B; 13- reactor; 14- gas-solid-liquid separator; 15- heat exchanger. DETAILED DESCRIPTION

[0015] The specific implementation modes of the present invention are described below in conjunction with the accompanying drawings and examples. However, the following examples are only used to illustrate the present invention in detail and do not limit the scope of the present invention in any way.

[0016] Example 1: See Figure 1 , a supercritical thermal power unit flexible power generation and waste treatment system, including a material conveying system, a supercritical water oxidation reaction system and a waste heat utilization system, wherein: In the material conveying system, the coal slime wastewater enters the material blending tank 8 and then passes through the material conveying pump 9, and then passes through the material preheater A 11 and the material preheater B 12 in sequence before entering the reactor 13. Among them, the heat for heating the material in the material preheater A 11 is the waste heat of the supercritical water oxidation reaction product; the heating medium of the material preheater B 12 is the flue gas at the outlet of the economizer 3, and the flue gas at the outlet of the economizer 3 is divided into two paths, the first path enters the air preheater 5 to heat the oxygen required for combustion in the oxygen-enriched boiler, and the second path enters the material preheater B 12 to heat the material, and the flue gas coming out of the air preheater 5 and the material preheater B 12 enters the tail flue gas waste heat utilization device 10; The supercritical water oxidation reaction system includes a reactor 13, which is provided with a steam inlet, an oxidant inlet and a material inlet. The steam inlet of the reactor 8 comes from the outlet steam of the oxygen-enriched combustion boiler. The oxidant required for the reaction is a part of oxygen extracted from the oxygen outlet of the air preheater 5 and then pressurized by the compressor 7 and enters the reactor 13. The compressor 7 is driven by the steam generated by the boiler. In the waste heat utilization system, the product after the reactor 13 passes through the heat exchanger 15 and enters the material preheater A 11 to heat the material. The product cooled by the material preheater A 11 enters the gas-solid-liquid separation device 9 to separate water, CO2 and residue. The separated water returns to the material blending tank, CO2 is sealed, and the remaining residue of the reaction is collected and processed. Among them, the cooling medium of the heat exchanger 15 is boiler condensate. After being heated, the boiler condensate comes out from the condensate outlet of the heat exchanger 15 and enters the low-pressure heater 1, the deaerator and the high-pressure heater 2 and the economizer 3 in sequence, and finally enters the boiler.

[0017] Principle and process of the present invention: When the boiler needs to reduce the power generation load when operating under the safe load, the boiler can be maintained under the safe load, a part of the steam is used to supply the turbine to generate power, and the remaining part of the steam enters the reactor 13 for supercritical water oxidation reaction. Coal slime wastewater is the material in the supercritical water oxidation treatment system. After entering the material blending tank 8, the material is sequentially transported to the material preheater A 11 and the material preheater B 12 by the material delivery pump 9 for preheating before entering the reactor 13. The oxidant is the oxygen at the inlet of the oxygen-enriched combustion boiler 6, which enters the reactor 13 after being pressurized by the compressor 7.

[0018] After the supercritical water oxidation reaction is completed, the product first passes through the heat exchanger 15 to heat the boiler condensate. The heated condensate passes through the low-pressure heater 1, the deaerator, the high-pressure heater 2 and the economizer 3 and then enters the boiler. The product coming out of the heat exchanger 15 passes through the material preheater A 11 to heat the material. Then, the cooled product passes through the gas-liquid separation device 14 to separate water, CO2 and residue. The separated water is returned to the material preparation tank 8, the separated CO2 is sealed, and finally the remaining reaction residue is collected and processed.

[0019] Since the temperature of the water in the low-pressure heater is increased by the heat exchanger 15, the wall temperature of the economizer is increased, the flue gas temperature at the economizer outlet is increased, and low-temperature corrosion of the economizer tube wall is avoided; further, the flue gas volume at the air preheater 5 can be appropriately reduced to reduce the risk of low-temperature corrosion of the heating surface. Therefore, the flue gas at the economizer outlet is divided into two paths, one path enters the air preheater 5 to heat oxygen, and the other path enters the material preheater B 12 to heat the material. Since the material preheater B 12 has been preheated by the material preheater A 11, the wall temperature of the material preheater B 12 is relatively high, which also avoids the risk of low-temperature corrosion. The flue gas from the outlets of the air preheater 5 and the material preheater B 12 enters the tail flue gas waste heat utilization device 10 for efficient waste heat utilization of the tail flue gas.

[0020] The present invention has been described in detail above with reference to the accompanying drawings and embodiments; however, those skilled in the art will appreciate that, without departing from the concept of the present invention, the specific parameters in the above embodiments may be changed, or related components and structures may be replaced by equivalents, thereby forming multiple specific embodiments, which are all within the common variation range of the present invention and will not be described in detail one by one.

Claims

1. A supercritical thermal power unit flexible power generation and waste treatment system, characterized in that: It includes material conveying system, supercritical water oxidation reaction system and waste heat utilization system, among which: The material conveying system comprises a material blending tank (8), the outlet of the material blending tank (8) is connected to a material conveying pump (9) and a material inlet of a material preheater A (11) in sequence, the material outlet of the material preheater A (11) is connected to a material inlet of a material preheater B (12), and the material outlet of the material preheater B (12) is connected to a material inlet of a reactor (13); wherein the heating medium of the material preheater B (12) is the flue gas at the outlet of the economizer (3), the flue gas at the outlet of the economizer (3) is divided into two paths, the first path enters the air preheater (5) to heat the oxygen required for combustion in the oxygen-enriched boiler, and the second path enters the material preheater B (12) to heat the material, and the flue gas coming out of the air preheater (5) and the material preheater B (12) enters the tail flue gas waste heat utilization device (10); The supercritical water oxidation reaction system comprises a reactor (13), wherein the reactor (13) is provided with a steam inlet, an oxidant inlet and a material inlet; wherein the steam inlet of the reactor (13) comes from the steam outlet of the oxygen-enriched combustion boiler, a compressor (7) is provided before the oxidant inlet of the reactor (13), and oxygen required for the reaction is a portion of oxygen extracted from the oxygen outlet of the air preheater (5), which is pressurized by the compressor (7) and then enters the reactor (13); The waste heat utilization system comprises a heat exchanger (15), wherein the product inlet of the heat exchanger (15) is connected to the product outlet of the reactor (13), the product outlet of the heat exchanger (15) is connected to the product inlet of the material preheater A (11), and the product outlet of the material preheater A (11) is connected to the gas-solid-liquid separation device (9); wherein the cooling medium of the heat exchanger (15) is boiler condensate, and the boiler condensate is heated and then flows out of the condensate outlet of the heat exchanger (15) and enters the low-pressure heater (1), the deaerator, the high-pressure heater (2) and the economizer (3) in sequence, and finally enters the boiler.

2. The supercritical thermal power unit flexible power generation and waste treatment system according to claim 1 is characterized in that: The steam at the outlet of the oxygen-enriched combustion boiler is divided into two paths, one path enters the steam turbine for power generation, and the other path enters the reactor (13).

3. The supercritical thermal power unit flexible power generation and waste treatment system according to claim 1 is characterized in that: The heat for heating the material in the material preheater A (11) is the waste heat of the supercritical water oxidation reaction product.

4. The supercritical thermal power unit flexible power generation and waste treatment system according to claim 1 is characterized in that: The compressor (7) is driven by steam generated by the boiler.

5. The supercritical thermal power unit flexible power generation and waste treatment system according to claim 1 is characterized in that: The gas-solid-liquid separation device (14) separates water, CO2 and residue; the separated water is returned to the material preparation tank, the CO2 is sealed, and the residue left over from the reaction is collected and processed.

Images