According to the way of coke oven flue gas pollutant generation, it can be controlled from the source, and the generation of pollutants should be controlled or reduced as much as possible; Furnace heating level, strengthening coke oven operation and management level, etc., but it is difficult to meet the emission requirements of the new version of the "Coking Chemical Industry Pollutant Discharge Standard" (GB16171-2012). Therefore, to meet the emission requirements, the end of coke oven flue gas pollutants Treatment technology (coke oven flue gas desulfurization and denitrification technology) is particularly important.
1. Desulfurization technology
Coke oven flue gas pollutant generation route: SO2 generation route in coke oven flue gas is mainly due to the S-containing substances in the fuel and coke oven "bleeding" so that part of the raw coal gas enters the combustion chamber. .
Commonly used desulfurization technologies are mainly as follows.
1. Wet flue gas desulfurization technology
Most domestic coking plants mostly choose wet flue gas desulfurization technology, using the existing ammonia water in coking for wet desulfurization.
2. Dry flue gas desulfurization technology
3. Semi-dry flue gas desulfurization technology
4. Other flue gas desulfurization methods
In recent years, science and technology have advanced by leaps and bounds. Relevant domestic units have developed some new desulfurization technologies, such as supergravity desulfurization technology, but most of them are still in the experimental stage and need further industrial application verification.
2. Denitrification technology
Formation pathways of NOx in coke oven flue gas
1) Fuel-type NOx: It is produced by the N-containing substances in the fuel and the "leakage" of the coke oven to make part of the raw coal gas during the combustion process (600~800°C); (auxiliary)
2) Rapid NOx, which is rapidly generated near the reaction zone when hydrocarbon fuels are burned too richly; (supplementary)
3) Thermal NOx: It is produced by redox reaction of N2 in the air with oxygen under high temperature conditions (1200~1350℃); (mainly)
Among the common denitrification technologies, selective catalytic reduction (SCR) is currently the mainstream technology for controlling NOx emitted in flue gas.
3. Technical scheme of desulfurization + denitrification process
1. Low temperature catalytic denitrification + ammonia desulfurization
This solution is the mainstream technology in the coking industry at present, the technology is mature and the most widely used.
Features of Low Temperature Catalytic Denitrification Technology
1) The technical route is short, the investment and operating costs are low, and the operation is convenient;
2) The reducing agent of this technology uses concentrated ammonia water, and the denitrification products are N2 and H2O, and the production is safe.
2. Technical characteristics of ammonia desulfurization
1) One-tower structure for desulfurization, mist capture and dust removal, small footprint, short process, low investment and easy operation;
2) The desulfurization tower adopts a plate structure, which can adapt to the fluctuation of flue gas volume;
3) The ammonia method has high desulfurization efficiency and is suitable for fluctuating sulfur content in the flue gas;
4. Basic requirements for electrical automation control of desulfurization and denitrification process
The coke oven flue gas denitrification waste heat utilization system has 2 booster fans for high-voltage load, which are controlled by 10kV frequency converter, adopt conventional comprehensive protection, and introduce PLC control system.
1.UPS system
The system power supply is equipped with UPS power supply, and it is best to configure it according to the dual-machine parallel redundancy, and the UPS is best to choose power frequency.
The control system adopts PLC control system, and the system is redundantly configured.
2. Instrument control system
In order to ensure the normal operation and stable compliance of the desulfurization and denitrification system, the control system of the desulfurization and denitrification device can automatically start and stop, and can automatically complete various real-time detection functions during normal operation, and has a chain function to prevent misoperation. It can perform all operations and monitoring on the HMI operation station; it can display and process process alarms; it can print alarm history and operation reports of relevant important parameters; it can complete the communication with the central control room of the coke oven.
On-line detection and control of each equipment of the desulfurization, denitrification and denitrification system, and through reasonable control system configuration, the chain control of necessary equipment and the optimal control of process parameters are realized. After completion, the control level will reach the normal startup and shutdown of desulfurization and denitrification systems in the control room; normal operation monitoring, operation and accident alarming will be completed.
The desulfurization and denitrification system is equipped with the necessary parameter detection function, that is, the detection and control of parameters such as temperature, pressure and flow of the flue gas before entering the denitration system storage and conveying device and before the denitrification system enters the chimney; denitrification reducing agent storage liquid level detection; Detection and control of SCR reactor pressure difference, temperature and valves; the supplied instruments and control equipment can ensure stability and reliability.
The concentration of nitrogen oxides and sulfur dioxide in the flue gas in the coke oven production process is first detected by the detection system, and the signal of the detection data is fed back to the computer. The agent injection device issues control commands to achieve the purpose of economical operation.
The flue gas detection and control system of the desulfurization and denitrification system has an interface, which is networked with the online flue gas monitoring implemented by the government department, so as to detect and control the desulfurization and denitrification effect at any time.
In order to ensure the stable operation of the waste heat recovery system, in addition to the necessary local display instruments, it is also necessary to equip remote instruments with signal sensors to centralize all the parameters that need to be monitored to the PLC system, and then through PLC programming, and finally on the host computer displayed and operable.
Relying on decades of experience in the chemical industry, Mingsheng Environmental Protection seeks development with the real industry, and with the concept of low-carbon economy and turning waste into treasure, it fundamentally solves the problems of high energy consumption and secondary pollution, and makes ultra-low emission technology, Systematize.
Mingsheng Environmental Protection is willing to unite with all walks of life to shoulder social and historical responsibilities and promote the progress of human civilization.
