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What are the advantages and disadvantages of tail gas desulfurization and denitrification?

At present, there are dozens of tail gas desulfurization technologies. According to whether water is added during the desulfurization process and the dry and wet form of the desulfurization product, tail gas desulfurization is divided into three types: wet, semi-dry and dry. Wet desulfurization technology is relatively mature, with high efficiency and simple operation.

1. Wet tail gas desulfurization technology

Advantages: The wet tail gas desulfurization technology is a gas-liquid reaction, the reaction speed is fast, the desulfurization efficiency is high, generally higher than 90%, the technology is mature, and it is widely used. The wet desulfurization technology is relatively mature, and the production operation is safe and reliable. It has been in a leading position in many desulfurization technologies, accounting for more than 80% of the total installed capacity of desulfurization.

Disadvantages: The product is liquid or sludge, which is difficult to handle, the equipment is seriously corroded, the flue gas after washing needs to be reheated, the energy consumption is high, the floor space is large, and the investment and operation cost is high. The system is complex, the equipment is huge, the water consumption is large, and the one-time investment is high, so it is generally suitable for large-scale power plants.

2. Dry tail gas desulfurization technology

Advantages: Dry tail gas desulfurization technology is a gas-identical reaction. Compared with the wet desulfurization system, it has the advantages of simple equipment, small footprint, low investment and operating costs, convenient operation, low energy consumption, easy product treatment, and no sewage treatment system.

Disadvantages: But the reaction speed is slow, the desulfurization rate is low, and the advanced technology can reach 60-80%. However, at present, this method has low desulfurization efficiency, low utilization rate of absorbent, serious wear and scaling, difficult equipment maintenance, low equipment operation stability and reliability, and short service life, which limit the application of this method.

3. Semi-dry tail gas desulfurization technology

Semi-dry desulfurization includes spray drying desulfurization, semi-dry and semi-wet desulfurization, powder spouted bed desulfurization and flue gas jet desulfurization.

Denitrification technology can be divided into pre-combustion denitrification and post-combustion denitrification

Denitrification before combustion: 1. Hydrodenitrification, 2. Washing, 3. Low-temperature combustion, 4. Low-oxygen combustion, 5. FBC combustion technology, 6. Using low-NOx burners, 7. Coal concentration and dilution separation, 8. Flue gas recirculation technology.

Post-combustion denitrification: 1. Selective non-catalytic reduction denitration (SNCR), 2. Selective catalytic reduction denitration (SCR), 3. Activated carbon adsorption, 4. Electron beam denitration technology.

Advantages of denitration: This method has high denitration efficiency and relatively low price. At present, it has been widely used in domestic and foreign projects, and has become the mainstream technology of power station flue gas denitrification.

Disadvantages of denitration: the fuel contains sulfur, and a certain amount of SO3 will be produced when it is burned. After adding the catalyst, under aerobic conditions, the content of SO3 increases significantly, and the excess NH3 forms NH4HSO4. NH4HSO4 is corrosive and viscous and can damage tailpipe equipment. Although the production of SO3 is limited, its impact cannot be underestimated. In addition, catalyst poisoning cannot be ignored.

For the desulfurization and denitration technology of boiler enterprises, most of the existing boiler manufacturers in my country use coal or gas as the combustion medium. For coal-fired boilers, the mature process in my country is FGD (using absorbent or adsorbent to remove sulfur dioxide from flue gas), and denitrification is mainly SCR technology of selective catalytic reduction.