Step-by-step flow control pressure reduction and wastewater recycling system and method for supercritical water gasification system
Through step-by-step flow control pressure reduction and wastewater reuse system, combined with flow control technology and damping water pump, the problem of step-down and CO2 separation of medium and high-pressure systems of coal supercritical water vaporization is solved, and efficient step-down and resource recycling are achieved. Improves system security and economics.
Patent Information
- Application Number
- CN202010167642.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-03-11
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2040-03-11
AI Technical Summary
During the supercritical water vaporization of coal, the traditional pressure reduction method of high-pressure systems leads to wear of backpressure valves, affecting the safe operation of the system, and it is difficult to separate CO2 in the synthesis gas.
The step by step flow control pressure reduction and wastewater reuse system is adopted, and through equipment such as heat recycler, cooler, flow control pressure reduction device, gas-liquid separator and gas-liquid solid three-phase separator, combined with flow control technology and damping water pump, it realizes High-efficiency pressure reduction and separation of gas-liquid solid phases, and use high-pressure water to absorb CO2 for crude separation of synthesis gas.
It effectively reduces the wear risk of backpressure valves, improves system safety and economy, realizes efficient separation of synthesis gas and resource recycling of products, reduces the load of a single pressure reduction device, and improves the operating reliability of the system.
Smart Images
Figure CN111234881B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of coal chemical industry, and particularly relates to a step-by-step flow control pressure reduction and wastewater recycling system and method for a supercritical water gasification system. Background Art
[0002] Coal supercritical water gasification hydrogen production technology is a new and efficient energy conversion and utilization technology. Supercritical water gasification technology uses coal as raw material and does not require drying. Supercritical water ( T c ≥ 373.95 ℃ , P c ≥ 22.064 MPa) as the reaction medium for gasification, coal undergoes steam reforming, gasification and shift reactions in supercritical water.
[0003] During the supercritical water gasification process of coal, the coal mainly undergoes steam reforming reaction (C+H2O → H2 + CO), water gas shift reaction (CO + H2O ⇌ CO2 + H2) and methanation reaction (CO + 3H2 ⇌ CH4+ H2O) in supercritical water. The volume fraction of H2 in the synthesis gas is about 70%, the volume fraction of CO2 is about 25%, and the rest is CH4, CO and some C2 gases (ethane, ethylene and acetylene), so the separation of CO2 in the synthesis gas is a crucial technical issue. Studies have found that the solubility of H2 and CO2 in high-pressure water is very different, so the synthesis gas can be roughly separated by absorbing CO2 with high-pressure water, and then the synthesis gas can be separated and purified for a second time.
[0004] In addition, the ash content in coal is about 10-25%. Since the reaction pressure of the supercritical water gasification reaction is as high as 25-30 MPa, the traditional pressure reduction method of the high-pressure system uses a back-pressure valve to reduce the pressure. However, under such a high pressure difference, the wear of the solid-containing fluid will cause the back-pressure valve to fail, thereby affecting the safe operation of the entire supercritical water gasification hydrogen production system. Summary of the invention
[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a step-by-step flow control pressure reduction and wastewater reuse system and method for a supercritical water gasification system, which can separate the synthesis gas by utilizing different pressures in the system, and achieve pressure reduction through flow control technology. After the pressure reduction, the gas-liquid-solid three-phase products can be separated online and the resource recovery of the products can be realized.
[0006] In order to achieve the above object, the technical solution adopted by the present invention is:
[0007] A step-by-step flow control pressure reduction and wastewater reuse system for a supercritical water gasification system, comprising a regenerator 1, wherein a heat source side inlet of the regenerator 1 is connected to a fluid after a supercritical water gasification reaction, a heat source side outlet of the regenerator 1 is connected to a heat source side inlet of a cooler 2, a heat source side outlet of the cooler 2 is connected to an inlet of a primary flow control pressure reduction device 3, an outlet of the primary flow control pressure reduction device 3 is connected to an inlet of a gas-liquid separator 4, a liquid phase outlet of the gas-liquid separator 4 is connected to an inlet of a back pressure valve 6, an outlet of the back pressure valve 6 is connected to an inlet of a gas-liquid-solid three-phase separator 7, a liquid phase outlet of the gas-liquid-solid three-phase separator 7 is connected to a sulfur recovery device 8, a liquid phase outlet of the sulfur recovery device 8 is connected to an ammonia nitrogen recovery device 9, and a wastewater outlet of the ammonia nitrogen recovery device 9 is connected back to the primary flow control pressure reduction device 3 via a damping water pump A10.
[0008] The cold source side channel of the regenerator 1 is a material channel, and the cold source side channel of the cooler 2 is a cooling water channel.
[0009] A secondary flow control and pressure reducing device 5 is arranged between the liquid phase outlet of the gas-liquid separator 4 and the inlet of the back pressure valve 6. The inlet of the secondary flow control and pressure reducing device 5 is connected to the liquid phase outlet of the gas-liquid separator 4, and the outlet is connected to the inlet of the back pressure valve 6. The wastewater outlet of the ammonia nitrogen recovery device 9 is connected back to the secondary flow control and pressure reducing device 5 through the damping water pump B11.
[0010] The fluid pressure after pressure reduction by the primary flow control pressure reducing device 3 is determined according to the solubility of the gas in high-pressure water, and is higher than the saturation pressure corresponding to the fluid temperature and higher than the atmospheric pressure; the fluid pressure after pressure reduction by the secondary flow control pressure reducing device 5 and the back pressure valve 6 is higher than the saturation pressure corresponding to the fluid temperature.
[0011] The temperature of the fluid after passing through the cooler 2 is determined according to the solubility of the gas in high-temperature water.
[0012] A plurality of gas-liquid separators and flow control and pressure reducing devices are connected in series between the secondary flow control and pressure reducing device 5 and the back pressure valve 6 .
[0013] The tail gas separated by the gas-liquid-solid three-phase separator 7 is burned to provide heat for the supercritical water gasification system.
[0014] The present invention also provides a step-by-step flow control pressure reduction and wastewater reuse method based on the step-by-step flow control pressure reduction and wastewater reuse system of the supercritical water gasification system. After the supercritical water gasification reaction, the fluid passes through a regenerator 1 and a cooler 2 to cool down, then passes through a primary flow control pressure reduction device 3 to reduce the pressure, then passes through a gas-liquid separator 4 to perform gas-liquid separation, the resulting liquid phase passes through a back pressure valve 6 to reduce the pressure, then passes through a gas-liquid-solid three-phase separator 7 to perform gas-liquid-solid three-phase separation, the resulting liquid phase enters a sulfur recovery device 8 to recover sulfur, then enters an ammonia nitrogen recovery device 9 to recover ammonia water, and the resulting wastewater is injected back into the primary flow control pressure reduction device 3 through a damping water pump A10, thereby achieving step-by-step flow control pressure reduction and wastewater reuse.
[0015] The liquid phase obtained by the gas-liquid separation in the gas-liquid separator 4 is depressurized again through the secondary flow control pressure reducing device 5, and then enters the back pressure valve 6. The wastewater obtained by the ammonia nitrogen recovery device 9 is injected back into the secondary flow control pressure reducing device 5 through the damping water pump B11.
[0016] Step-by-step flow control and pressure reduction is achieved through the primary flow control and pressure reduction device 3 or its combination with the secondary flow control and pressure reduction device 5, and precise control of the system pressure is achieved through the back pressure valve 6. The pressure control of the primary flow control and pressure reduction device 3 is achieved through the cooperation of the damping water pump A10; the pressure control of the secondary flow control and pressure reduction device 5 is achieved through the cooperation of the damping water pump B11, and the water inlet of the damping water pump A10 and the damping water pump B11 is given priority.
[0017] Compared with the prior art, the present invention utilizes step-by-step flow control pressure reduction technology to achieve low-wear pressure reduction of high-pressure slurry gasified by supercritical water, and couples the two processes of pressure reduction and gas separation together. After passing through the first flow control pressure reduction device, high-pressure water is used to absorb CO2 in the synthesis gas, thereby achieving rough separation of the synthesis gas, making full use of the high solubility of high-pressure water in CO2. Multi-stage pressure reduction can reduce the pressure reduction load on a single pressure reduction device. The first and second pressure reduction devices use flow control technology to reduce pressure to avoid wear. The first and second pressure reduction devices assume the main pressure reduction function in the system, and the back pressure valve assumes the secondary pressure reduction function and precise pressure control function of the system. The reduction in the pressure difference before and after the back pressure valve can reduce the probability of failure of the back pressure valve and increase the safety of system operation. The main function of the first pressure reducing device is to reduce the system to a suitable gas separation pressure. In addition, it can reduce the pressure bearing capacity requirements of the subsequent equipment of the first pressure reducing device and increase the safety and economy of the system. The main function of the second pressure reducing device and the back pressure valve is to obtain a suitable gas-liquid-solid separation pressure, wherein the pressure drop of the second pressure reducing device is greater than the pressure drop of the back pressure valve, and the pressure after the back pressure valve is still suitable for liquid-solid separation. This pressure is used as the power of filtration to achieve liquid-solid separation in the three-phase separator. The gas in the gas-liquid-solid separator overflows from the water according to the dissolution equilibrium, and the tail gas is discharged through the exhaust valve. The tail gas can be directly discharged into the air, or burned to provide heat for the system. The residue discharged from the gas-liquid-solid three-phase separator can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a schematic diagram of the system structure of the present invention.
[0019] Among them, 1 is a regenerator; 2 is a cooler; 3 is a primary flow control pressure reducing device; 4 is a gas-liquid separator; 5 is a secondary flow control pressure reducing device; 6 is a back pressure valve; 7 is a gas-liquid-solid three-phase separator; 8 is a sulfur recovery device; 9 is an ammonia nitrogen recovery device; 10 is a damping water pump A; 11 is a damping water pump B.
[0020] Figure 2 It is the effect of pressure on the absorption rate of various gases (T=298K). DETAILED DESCRIPTION
[0021] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples. Example
[0022] like Figure 1As shown, a step-by-step flow control pressure reduction and wastewater reuse system of a supercritical water gasification system includes a regenerator 1, a cold source side channel of the regenerator 1 is a material channel, a heat source side inlet of the regenerator 1 is connected to the fluid after the supercritical water gasification reaction, a heat source side outlet of the regenerator 1 is connected to the heat source side inlet of the cooler 2, a heat source side outlet of the cooler 2 is connected to the inlet of a primary flow control pressure reduction device 3, and a cold source side channel of the cooler 2 is a cooling water channel. The outlet of the primary flow control pressure reduction device 3 is connected to the inlet of a gas-liquid separator 4, the liquid phase outlet of the gas-liquid separator 4 is connected to the inlet of a back pressure valve 6, the outlet of the back pressure valve 6 is connected to the inlet of a gas-liquid-solid three-phase separator 7, the liquid phase outlet of the gas-liquid-solid three-phase separator 7 is connected to a sulfur recovery device 8, the liquid phase outlet of the sulfur recovery device 8 is connected to an ammonia nitrogen recovery device 9, and the wastewater outlet of the ammonia nitrogen recovery device 9 is connected back to the primary flow control pressure reduction device 3 through a damping water pump A10.
[0023] According to the structure, the step-by-step flow control pressure reduction and wastewater reuse process of the present invention includes temperature reduction, pressure reduction, gas-liquid-solid separation, energy recovery and resource utilization. Specifically:
[0024] The fluid after the supercritical water gasification reaction is cooled in a step-by-step manner. The fluid after the supercritical water gasification reaction passes through the regenerator 1 to preheat the cold material, and then enters the cooler 2 for cooling. The cooler 2 is used to control the fluid temperature to control the solubility of the generated gas in water. The output heat of the cooler 2 can provide the system with but is not limited to hot water and steam. Subsequently, a step-by-step pressure reduction is adopted. The cooled fluid is reduced in pressure by a primary flow control pressure reducing device 3, and then is separated into gas and liquid by a gas-liquid separator 4. The gas-liquid separator 4 absorbs CO2 in the synthesis gas, and the separated gas is used after subsequent purification treatment; the obtained liquid phase is reduced in pressure again by a back pressure valve 6, and then is separated into gas, liquid and solid by a gas-liquid-solid three-phase separator 7. The separated gas can be directly discharged into the air, or collected and reused. The utilization of the tail gas includes but is not limited to preheating the reaction materials of supercritical water gasification after combustion. The separated solid residue can be recycled, and the utilization includes but is not limited to brick making and building materials; the separated liquid phase can be recycled, specifically, it first enters a sulfur recovery device 8 to recover the sulfur therein, and then enters an ammonia nitrogen recovery device 9, and recovers ammonia nitrogen in the liquid phase by methods such as but not limited to ammonia evaporation. The wastewater obtained by the ammonia nitrogen recovery device 9 is injected back into the primary flow control pressure reducing device 3 through a damping water pump A10, thereby realizing step-by-step flow control pressure reduction and wastewater reuse.
[0025] The fluid pressure after the pressure reduction by the primary flow control pressure reduction device 3 is determined according to the solubility of the gas in the high-pressure water, which can be determined experimentally. Figure 2As the pressure increases, the solubility of the gas in the high-pressure water increases. The absorption rate of CO2 is significantly higher than that of CH4 and H2, and the difference in absorption rate reaches the maximum at about 10-14MPa. In this way, the appropriate pressure reduction pressure is determined. At the same time, the fluid pressure must be higher than the saturation pressure corresponding to the fluid temperature and higher than the atmospheric pressure to keep the water in the liquid phase. For example, the saturation pressure of water at 300°C is 8.59 MPa. As long as the water pressure is greater than 8.59 MPa, water vaporization can be avoided.
[0026] The pressure control of the primary flow control pressure reducing device 3 is realized by the damping water pump A10, and the water inlet of the damping water pump A10 is preferred. The fluid pressure after the pressure reduction by the back pressure valve 6 is also higher than the saturation pressure corresponding to the fluid temperature after the pressure reduction, and higher than the atmospheric pressure, so that the water is kept in the liquid phase to avoid the vaporization of water.
[0027] The temperature of the fluid after passing through the cooler 2 is determined according to the solubility of the gas in the high-temperature water. Example
[0028] like Figure 1 As shown, a step-by-step flow control pressure reduction and wastewater reuse system of a supercritical water gasification system is provided. On the basis of Example 1, a secondary flow control pressure reduction device 5 is added between the liquid phase outlet of the gas-liquid separator 4 and the inlet of the back pressure valve 6, that is, the inlet of the secondary flow control pressure reduction device 5 is connected to the liquid phase outlet of the gas-liquid separator 4, and the outlet is connected to the inlet of the back pressure valve 6, and the wastewater outlet of the ammonia nitrogen recovery device 9 is connected back to the secondary flow control pressure reduction device 5 through the damping water pump B11.
[0029] Under this structure, the liquid phase obtained by gas-liquid separation in the gas-liquid separator 4 is depressurized again through the secondary flow control pressure reducing device 5, and then enters the back pressure valve 6. The wastewater obtained by the ammonia nitrogen recovery device 9 is injected back into the secondary flow control pressure reducing device 5 through the damping water pump B11.
[0030] At this time, step-by-step flow control and pressure reduction are achieved through the combination of the primary flow control and pressure reduction device 3 and the secondary flow control and pressure reduction device 5, and precise control of the system pressure is achieved through the back pressure valve 6. The pressure control of the primary flow control and pressure reduction device 3 is achieved through the cooperation of the damping water pump A10; the pressure control of the secondary flow control and pressure reduction device 5 is achieved through the cooperation of the damping water pump B11, and the water inlet of the damping water pump A10 and the damping water pump B11 is given priority.
[0031] The fluid pressure after the pressure reduction by the secondary flow control pressure reducing device 5 and the back pressure valve 6 is also higher than the saturation pressure corresponding to the fluid temperature after the pressure reduction, and is higher than the atmospheric pressure.
[0032] In the present invention, the primary flow control pressure reducing device 3 and the secondary flow control pressure reducing device 5 use flow control technology to reduce the fluid pressure after the supercritical water gasification reaction. Example
[0033] On the basis of Example 2, this example provides specific optional parameters. The fluid (600°C, 25 MPa) after the supercritical water gasification reaction is preheated by the regenerator 1 to preheat the cold material, and the hot fluid temperature is reduced to 200°C. Then, it enters the cooler 2 to be further cooled to 80°C, and then enters the first-level pressure reducing device 3 to be reduced in pressure to 10 MPa. The pressure is controlled by the damping water pump 11. Then, it enters the gas-liquid-solid separator 4 for rough separation to obtain hydrogen-rich synthesis gas. The liquid phase of the gas-liquid separator 4 enters the second pressure reducing device 5 to reduce the pressure to 1 MPa. The pressure is controlled by the damping water pump 12, and then enters the back pressure valve to be reduced to 0.5 MPa. The fluid after pressure reduction enters the gas-liquid-solid three-phase separator 7, wherein the separated tail gas is discharged through the top of the gas-liquid-solid three-phase separator 7, the separated residue is discharged through the slag discharge valve at the bottom of the gas-liquid-solid three-phase separator 7, and the separated waste water is discharged through the liquid discharge port of the gas-liquid-solid three-phase separator 7, and then oxygen is introduced into the waste water to oxidize the sulfur therein into sulfur element for separation, and then the waste water enters the ammonia nitrogen recovery device to recover the ammonia nitrogen.
[0034] In more embodiments of the present invention, more stages of gas-liquid separators and flow control and pressure reducing devices can be connected in series between the secondary flow control and pressure reducing device 5 and the back pressure valve 6 according to actual needs.
Claims
1. A step-by-step flow control pressure reduction and wastewater recycling system for a supercritical water gasification system, characterized in that: The invention comprises a regenerator (1), wherein the heat source side inlet of the regenerator (1) is connected to the fluid after the supercritical water gasification reaction, the heat source side outlet of the regenerator (1) is connected to the heat source side inlet of a cooler (2), the heat source side outlet of the cooler (2) is connected to the inlet of a primary flow control pressure reduction device (3), the outlet of the primary flow control pressure reduction device (3) is connected to the inlet of a gas-liquid separator (4), a secondary flow control pressure reduction device (5) is arranged between the liquid phase outlet of the gas-liquid separator (4) and the inlet of a back pressure valve (6), the inlet of the secondary flow control pressure reduction device (5) is connected to the liquid phase outlet of the gas-liquid separator (4), and the outlet is connected to the inlet of the back pressure valve (6). The inlet of the regenerator (1) and the outlet of the back pressure valve (6) are connected to the inlet of the gas-liquid-solid three-phase separator (7); the liquid phase outlet of the gas-liquid-solid three-phase separator (7) is connected to the sulfur recovery device (8); the liquid phase outlet of the sulfur recovery device (8) is connected to the ammonia nitrogen recovery device (9); the wastewater outlet of the ammonia nitrogen recovery device (9) is connected back to the primary flow control pressure reduction device (3) through a damping water pump A (10); the cold source side channel of the regenerator (1) is a material channel, and the cold source side channel of the cooler (2) is a cooling water channel; the wastewater outlet of the ammonia nitrogen recovery device (9) is also connected back to the secondary flow control pressure reduction device (5) through a damping water pump B (11).
2. The step-by-step flow control pressure reduction and wastewater recycling system of the supercritical water gasification system according to claim 1, characterized in that: The pressure of the fluid after the pressure reduction by the primary flow control pressure reducing device (3) is determined according to the solubility of the gas in the high-pressure water, and is higher than the saturation pressure corresponding to the temperature of the fluid and higher than the atmospheric pressure; the pressure of the fluid after the pressure reduction by the secondary flow control pressure reducing device (5) and the back pressure valve (6) is higher than the saturation pressure corresponding to the temperature of the fluid.
3. The step-by-step flow control pressure reduction and wastewater recycling system of the supercritical water gasification system according to claim 1, characterized in that: The temperature of the fluid after passing through the cooler (2) is determined according to the solubility of the gas in high-temperature water.
4. The step-by-step flow control pressure reduction and wastewater recycling system of the supercritical water gasification system according to claim 1, characterized in that: A plurality of stages of gas-liquid separators and flow control and pressure reduction devices are connected in series between the secondary flow control and pressure reduction device (5) and the back pressure valve (6).
5. The step-by-step flow control pressure reduction and wastewater recycling system of the supercritical water gasification system according to claim 1, characterized in that: The tail gas separated by the gas-liquid-solid three-phase separator (7) is burned to provide heat for the supercritical water gasification system.
6. The step-by-step flow control pressure reduction and wastewater reuse method of the supercritical water gasification system and wastewater reuse system according to claim 1, characterized in that: After the supercritical water gasification reaction, the fluid passes through a regenerator (1) and a cooler (2) to reduce the temperature, then passes through a primary flow control pressure reduction device (3) to reduce the pressure, then passes through a gas-liquid separator (4) to separate the gas and liquid, the liquid phase obtained by the gas-liquid separation in the gas-liquid separator (4) passes through a secondary flow control pressure reduction device (5) to reduce the pressure again, then enters a back pressure valve (6), then passes through a gas-liquid-solid three-phase separator (7) to separate the gas-liquid-solid three-phase, the obtained liquid phase enters a sulfur recovery device (8) to recover sulfur, then enters an ammonia nitrogen recovery device (9) to recover ammonia water, the obtained waste water is injected back into the primary flow control pressure reduction device (3) through a damping water pump A (10), and the waste water obtained by the ammonia nitrogen recovery device (9) is injected back into the secondary flow control pressure reduction device (5) through a damping water pump B (11), thereby realizing step-by-step flow control pressure reduction and waste water reuse.
7. The step-by-step flow control pressure reduction and wastewater reuse method according to claim 6, characterized in that: Step-by-step flow control and pressure reduction are achieved by combining a primary flow control and pressure reduction device (3) with a secondary flow control and pressure reduction device (5), and precise control of system pressure is achieved by a back pressure valve (6). Pressure control of the primary flow control and pressure reduction device (3) is achieved by cooperating with a damping water pump A (10); and pressure control of the secondary flow control and pressure reduction device (5) is achieved by cooperating with a damping water pump B (11).