Each type of dust collector has its own unique manufacturing process and working principle. Bag dust collectors and filter cartridges are generally used to deal with dusty contaminated gases. Sulfur-containing gas cannot be treated. Processing sulfur-containing flue gas requires the use of special dust collector equipment-desulfurization tower or desulfurization dust collector.
Desulfurization processes are also classified into physical absorption methods and chemical absorption methods. In fact, the ultimate purpose of both is to remove sulfur in sulfur-containing gas. How does the desulfurization tower or desulfurization dust collector perform desulfurization? What should be paid attention to in the operation of the desulfurization tower and desulfurization dust collector? Cohan Environmental Protection Editor will briefly introduce you.
1 Basic principles of wet flue gas desulfurization
(1) Basic principles of physical absorption
Gas absorption can be divided into two types: physical absorption and chemical absorption. If no significant chemical reaction occurs in the absorption process, it is simply a process in which the absorbed gas is dissolved in the liquid, which is called physical absorption, such as the absorption of SO2 with water. The characteristic of physical absorption is that as the temperature increases, the amount of absorbed gas decreases. The degree of physical absorption depends on the gas-liquid equilibrium. As long as the partial pressure of the gas phase is greater than the partial pressure of the gas when the liquid phase is in equilibrium, the absorption process will proceed. Because the driving force of the physical absorption process is very small and the absorption rate is low, it is required in engineering design that the partial pressure of the gas phase of the purified gas is greater than the partial pressure of the gas at the time of gas-liquid equilibrium. The physical absorption rate is low, and the physical absorption method is rarely used alone in modern smoke.
(2) Basic principles of chemical absorption method
If the absorbed gas component chemically reacts with the components of the absorption liquid, it is called chemical absorption, for example, the use of an alkaline solution to absorb SO2. The process of applying a solid absorbent to chemically react with the absorbed component and separating it from the flue gas is also a chemical absorption. For example, calcium oxide (CaO) flue gas desulfurization in a furnace is also a chemical absorption. During the chemical absorption process, the absorbed gas reacts with the components of the liquid phase, effectively reducing the partial pressure of the absorbed gas on the solution surface. The driving force of the absorption process is increased, that is, the absorption efficiency is improved and the partial pressure of the gas phase of the absorbed gas is reduced. Therefore, the chemical absorption rate is much larger than the physical absorption rate.
Both physical absorption and chemical absorption are affected by the gas phase diffusion speed (or gas film resistance) and liquid phase diffusion speed (or liquid film resistance). In engineering, it is common to strengthen the gas-liquid two-phase disturbance to eliminate the resistance of the gas film and the liquid film. . In flue gas desulfurization, a large amount of flue gas containing low-concentration SO2 must be continuously and instantly purified. If physical absorption is applied alone, it is difficult to meet SO2 emission standards because of its low purification efficiency. Therefore, chemical absorption is widely used in flue gas desulfurization technology. Chemical absorption method for flue gas desulfurization is relatively mature in technology, rich in operating experience, and practical. It has become the most widely used and most common flue gas desulfurization technology.
In the desulfurization tower and desulfurization duster, the lye is used to wash the SO2 containing flue gas, and the SO2 in the flue gas is chemically absorbed. In order to strengthen the absorption process, improve desulfurization efficiency, and reduce equipment investment and operating costs,
The desulfurization tower and desulfurization dust collector should meet the following basic requirements:
(1) There is a large contact area and a certain contact time between gas and liquid;
(2) Strong gas-liquid disturbance, low absorption resistance and high absorption efficiency of SO2;
(3) The operation is stable, and there must be appropriate operation flexibility;
(4) The pressure drop during airflow should be small;
(5) Simple structure, convenient manufacturing and maintenance, low cost and long service life;
(6) non-scale, non-clog, wear-resistant, corrosion-resistant;
(7) Low energy consumption and no secondary pollution.