Water treatment system for regulating coal gas water pH with carbon dioxide

Abstract

The utility model provides a kind of water treatment system for adjusting coal gas water pH by carbon dioxide, including oil separation tank, adjusting pool, dissolved air flotation machine and dross tank, the water inlet of oil separation tank is connected with coal gas water inlet pipe, the water outlet of oil separation tank is connected with the water inlet of adjusting pool, the water outlet of adjusting pool is connected with the water inlet of dissolved air flotation machine, the water outlet of dissolved air flotation machine is connected with the import of hydrolytic acidification pool, and the dreg outlet of dissolved air flotation machine is connected with the import of dross tank;Micro-porous aerator is equipped in adjusting pool, the air inlet of micro-porous aerator is connected with carbon dioxide pipe, and adjusting valve is installed on carbon dioxide pipe;pH detector is installed in adjusting pool, and oxygen concentration analyzer is installed outside adjusting pool. By carbon dioxide adjusting wastewater pH, replace sulfuric acid dosing to adjust pH, reduce the content of sulfate in wastewater, reduce the addition amount of soda in rear-end hardening system, reduce soda consumption, improve economic benefit.

Description

Technical Field

[0001] This utility model relates to the field of water treatment, specifically to a water treatment system that uses carbon dioxide to adjust the pH of coal gas water. Background Technology

[0002] During the coal gasification process, coal reacts with gasifying agent in the BGL gasifier to generate crude coal gas, which carries substances such as tar, phenols, ammonia, and sulfides. These substances are condensed and dissolved in water during the subsequent washing and cooling process, forming coal gas water containing a three-phase mixture of gas, liquid, and solid.

[0003] The wastewater treatment process for coal gasification typically includes steps such as sedimentation, coagulation, acidification, biological treatment, and membrane separation. Among these, the acidification unit requires precise adjustment of the wastewater's pH value to meet system operating parameter requirements. Currently, concentrated sulfuric acid (93% H₂SO₄) or dilute hydrochloric acid (31% HCl) is commonly used as a neutralizing agent for pH adjustment of alkaline wastewater. While this process effectively adjusts the pH value, it introduces SO₄²⁻ into the water system. 2− or Cl − Plasma significantly increases the ion concentration in water, leading to increased system conductivity and salt enrichment. When implementing zero-discharge wastewater treatment, the final zero-discharge process requires evaporation and crystallization to remove all salts. This creates a process paradox between the increased ion load in the upstream process and the downstream evaporation and crystallization process, increasing both the upstream treatment load and downstream energy consumption. This results in reduced resource utilization efficiency and economic losses, significantly contradicting the green and low-carbon development strategies of industrial enterprises. Utility Model Content

[0004] The purpose of this invention is to provide a water treatment system that uses carbon dioxide to adjust the pH of coal gas water.

[0005] This utility model is implemented by the following technical solution:

[0006] A water treatment system for adjusting the pH of coal gas-water using carbon dioxide includes an oil separator, an equalization tank, a dissolved air flotation (DAF) machine, and a scum tank. The inlet of the oil separator is connected to the coal gas-water inlet pipe, the outlet of the oil separator is connected to the inlet of the equalization tank, the outlet of the equalization tank is connected to the inlet of the DAF machine, the outlet of the DAF machine is connected to the inlet of the hydrolysis acidification tank, and the scum discharge port of the DAF machine is connected to the inlet of the scum tank.

[0007] The regulating tank is equipped with a microporous aerator, the air inlet of which is connected to a carbon dioxide pipe, and a regulating valve is installed on the carbon dioxide pipe.

[0008] A pH meter is installed inside the equalization tank, and an oxygen concentration analyzer is installed outside the equalization tank. The signal output terminals of the pH meter and the oxygen concentration analyzer are electrically connected to the signal input terminal of the regulating valve.

[0009] Preferably, a return water pipe is connected to the gas-water inlet pipe, a gas-water shut-off valve is installed at the inlet of the oil separator, and a return water shut-off valve is installed on the return water pipe.

[0010] Preferably, the outlet of the scum pool is connected to the inlet of the screw feeder; a level gauge is installed at the top of the scum pool, and the signal output terminal of the level gauge is electrically connected to the signal input terminal of the screw feeder.

[0011] The advantages of this invention are: It uses carbon dioxide to adjust the pH of wastewater, replacing sulfuric acid, thus reducing the sulfate content in the wastewater, weakening the reaction intensity of sulfur-oxidizing bacteria, reducing the generation of waste gases such as hydrogen sulfide, reducing the amount of soda ash added in the downstream hardening system, lowering soda ash consumption, and improving economic efficiency. A pH meter is used to monitor the equalization tank and control the opening of the regulating valve to ensure the wastewater pH is between 8.3 and 8.8, facilitating flocculation in the scum tank. An oxygen concentration analyzer is used to monitor the oxygen concentration in the air near the equalization tank; when the oxygen concentration is below 18.5%, the regulating valve is fully closed to prevent the risk of worker asphyxiation due to carbon dioxide leakage. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of this utility model.

[0013] In the diagram: 1. Oil separator; 2. Equalization tank; 3. Dissolved air flotation machine; 4. Scum tank; 5. Gas and water inlet pipe; 6. Microporous aerator; 7. Carbon dioxide pipe; 8. Regulating valve; 9. pH meter; 10. Oxygen concentration analyzer; 11. Return water pipe; 12. Gas and water shut-off valve; 13. Return water shut-off valve; 14. Screw feeder; 15. Level gauge. Detailed Implementation

[0014] like Figure 1As shown, a water treatment system for adjusting the pH of coal gas-water using carbon dioxide includes an oil separator 1, an equalization tank 2, a dissolved air flotation (DAF) machine 3, and a scum tank 4. The inlet of the oil separator 1 is connected to the coal gas-water inlet pipe 5, the outlet of the oil separator 1 is connected to the inlet of the equalization tank 2, the outlet of the equalization tank 2 is connected to the inlet of the DAF machine 3, the outlet of the DAF machine 3 is connected to the inlet of the hydrolysis acidification tank, and the scum discharge port of the DAF machine 3 is connected to the inlet of the scum tank 4. A microporous aerator 6 is installed inside the equalization tank 2, and the air inlet of the microporous aerator 6 is connected to a carbon dioxide pipe 7. A regulating valve 8 is installed on the carbon dioxide pipe 7. A pH meter 9 is installed inside the equalization tank 2, and an oxygen concentration analyzer 10 is installed outside the equalization tank 2. The signal output terminals of the pH meter 9 and the oxygen concentration analyzer 10 are electrically connected to the signal input terminal of the regulating valve 8.

[0015] The coal gas water comes from the phenol and ammonia recovery section and enters the oil separator 1 from the coal gas water inlet pipe 5. Under the action of gravity, the substances are separated by the density difference between them. Heavy oil with a relative density greater than 1 sinks and floating oil with a relative density less than 1 floats. The coal gas water completes the stratification and separation in the oil separator sedimentation tank. After the oil separation treatment, the oil content in the wastewater is reduced to 140mg / L. This wastewater is sent to the equalization tank 2 through the overflow pipe.

[0016] In the equalization tank 2, carbon dioxide is injected into the wastewater through the microporous aerator 6 and mixed thoroughly to adjust the pH of the wastewater to 8.3-8.8. The adjusted wastewater is then pumped into the dissolved air flotation machine 3.

[0017] In the dissolved air flotation unit 3, coagulant PAC (polyaluminum chloride) and flocculant PAM (polyacrylamide) are first added. Under the action of PAC and PAM, the colloids, particles and oil in the wastewater are destabilized and flocculated to form larger flocs. Under the propulsion of surface static pressure, buoyancy and hydraulic force of the flotation unit, the flocs gradually float to the water surface and eventually aggregate into scum. The scum is scraped out by the intermittently operating scum scraper and overflows from the scum discharge port into the scum pool 4. The scum in the scum pool 4 is sent to the boiler for incineration.

[0018] pH meter 9 is used to detect the pH of wastewater in equalization tank 2. The opening of regulating valve 8 is controlled by the detected value to keep the pH between 8.3 and 8.8 so as to facilitate flocculation in scum tank 4. When the pH is lower than 8.3, the opening of regulating valve 8 is reduced by controlling the DCS system or PLC. When the pH is higher than 8.8, the opening of regulating valve 8 is increased.

[0019] Meanwhile, the oxygen concentration analyzer 10 is used to detect the oxygen concentration of the air near the equalization tank 2. When the oxygen concentration is lower than 18.5%, the control valve 8 is fully closed to avoid the risk of workers suffocating in the surrounding environment due to carbon dioxide leakage.

[0020] A return water pipe 11 is connected to the gas-water inlet pipe 5. A gas-water shut-off valve 12 is installed at the inlet of the oil separator 1. A return water shut-off valve 13 is installed on the return water pipe 11. After a system failure, the gas-water shut-off valve 12 is closed and the return water shut-off valve 13 is opened to guide the gas-water back to the gas-water pool for storage, so as to avoid the oil content in the drainage exceeding the standard due to the failure.

[0021] The outlet of the scum pool 4 is connected to the inlet of the screw feeder 14. Since the amount of scum entering the scum pool 4 is not constant, a level gauge 15 is installed at the top of the scum pool 4 to avoid the screw feeder 14 running idle due to periodic discharge. The signal output terminal of the level gauge 15 is electrically connected to the signal input terminal of the screw feeder 14. The level gauge 15 measures the liquid level in the scum pool 4. When the liquid level in the scum pool 4 reaches its maximum, the screw feeder 14 starts to discharge the scum.

[0022] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A water treatment system that uses carbon dioxide to adjust the pH of coal gas water, characterized in that, It includes an oil separator, an equalization tank, a dissolved air flotation (DAF) machine, and a scum tank. The inlet of the oil separator is connected to the gas-water inlet pipe, the outlet of the oil separator is connected to the inlet of the equalization tank, the outlet of the equalization tank is connected to the inlet of the DAF machine, the outlet of the DAF machine is connected to the inlet of the hydrolysis acidification tank, and the scum discharge port of the DAF machine is connected to the inlet of the scum tank. The regulating tank is equipped with a microporous aerator, the air inlet of which is connected to a carbon dioxide pipe, and a regulating valve is installed on the carbon dioxide pipe. A pH meter is installed inside the equalization tank, and an oxygen concentration analyzer is installed outside the equalization tank. The signal output terminals of the pH meter and the oxygen concentration analyzer are electrically connected to the signal input terminal of the regulating valve.

2. The water treatment system for adjusting the pH of coal gas water using carbon dioxide according to claim 1, characterized in that, A return water pipe is connected to the gas-water inlet pipe, a gas-water shut-off valve is installed at the inlet of the oil separator, and a return water shut-off valve is installed on the return water pipe.

3. The water treatment system for adjusting the pH of coal gas water using carbon dioxide according to claim 1 or 2, characterized in that, The outlet of the scum pool is connected to the inlet of the screw feeder; a level gauge is installed at the top of the scum pool, and the signal output terminal of the level gauge is electrically connected to the signal input terminal of the screw feeder.

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