Which is better for flue gas desulfurization?

At present, there are dozens of flue gas desulfurization technologies. According to whether water is added in the desulfurization process and the dry and wet forms of desulfurization products, flue gas desulfurization can be divided into three categories: wet, semi-dry and dry desulfurization processes. Wet flue gas desulfurization technology is the most mature and has been applied in large-scale industrialization, but due to the high investment cost, the process and equipment need to be optimized. Dry flue gas desulfurization technology has no problems such as corrosion and condensation, but the desulfurization rate is much lower than that of wet desulfurization technology, which will not be adopted in general power plants. It is necessary to further develop dry desulfurization technology based on new desulfurization principles. Semi-dry desulfurization technology has high desulfurization rate, but it is not suitable for large-capacity combustion equipment. Select the most suitable desulfurization method under different working conditions to obtain the maximum economic benefit.

1 wet flue gas desulfurization technology

Advantages: Wet flue gas desulfurization technology is a gas-liquid reaction, with fast reaction speed, high desulfurization efficiency, generally higher than 90%, mature technology and wide application. Wet desulfurization technology is mature, and the production operation is safe and reliable. Among many desulfurization technologies, it always occupies a dominant position, 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 corrosive, the washed flue gas needs to be reheated, the energy consumption is high, the floor space is large, and the investment and operation costs are 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 power plants.

Classification: Commonly used wet flue gas desulfurization technologies include limestone-gypsum method, indirect limestone-gypsum method and lemon absorption method.

Limestone/lime-gypsum method:

Principle: SO2 in flue gas is absorbed by limestone or lime slurry to generate calcium sulfite. The separated calcium sulfite (CaSO _ 3) can be discarded or oxidized into calcium sulfate (CaSO _ 4), which can be recovered in the form of gypsum. It is the most mature and stable desulfurization process in the world at present, and the desulfurization efficiency reaches over 90%.

At present, the traditional limestone/lime-gypsum flue gas desulfurization process is widely used in China market. Calcium sulfite and calcium sulfate produced by calcium-based desulfurizer absorbing sulfur dioxide are easy to form scaling and blockage in desulfurization tower and pipeline because of their low solubility. Compared with limestone desulfurization technology, double alkali flue gas desulfurization technology overcomes the shortcoming of easy scaling of limestone-lime method.

B. indirect limestone-gypsum method:

Common indirect limestone-gypsum methods are: sodium-alkali double alkali method, basic aluminum sulfate method and dilute sulfuric acid absorption method. Principle: Sodium alkali, basic alumina (Al2O3 &; Dot; NH2O) or dilute sulfuric acid (H2SO4) absorbs SO2, and the generated absorption solution reacts with limestone to regenerate gypsum. This method has the advantages of simple operation, less secondary pollution, no scaling and blockage, high desulfurization efficiency, but poor quality of gypsum products.

C lemon absorption method:

Principle: citric acid (h3c6h5o7 &; Dot; H2O) solution has good buffering performance. When SO2 gas passes through citrate liquid, SO2 in flue gas reacts with H in water to form H2SO3 complex, and the SO2 absorption rate is over 99%.