Wet flue gas desulfurization technology

Advantages: Wet flue gas desulfurization technology is a gas-liquid reaction with fast reaction speed and high desulfurization efficiency, generally higher than 90%. The technology is mature and has wide applicability. Wet desulfurization technology is relatively mature, and its production and operation are safe and reliable. It has always occupied a dominant position among many desulfurization technologies, accounting for more than 80% of the total installed desulfurization capacity.

Disadvantages: The product is liquid or sludge, which is difficult to handle, the equipment is severely corrosive, the flue gas needs to be reheated after washing, the energy consumption is high, the floor space is large, and the investment and operating 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, lemon absorption method, etc.

A. Limestone/lime-gypsum method:

Principle: Limestone or lime slurry is used to absorb SO2 in flue gas to generate calcium sulfite. The separated calcium sulfite (CaSO3) can be discarded or oxidized into calcium sulfate (CaSO4) and recycled in the form of gypsum. It is currently the most technically mature and most stable desulfurization process in the world, with a desulfurization efficiency of over 90%.

At present, the traditional limestone/lime-gypsum flue gas desulfurization process is widely used in the current Chinese market. It uses a calcium-based desulfurizer to absorb sulfur dioxide to generate calcium sulfite and calcium sulfate. Due to their low solubility, they are easily Scale and blockage will form in the desulfurization tower and pipelines. Compared with the limestone desulfurization technology, the dual-alkali flue gas desulfurization technology overcomes the shortcomings of the limestone-lime method that are prone to scaling.

B. Indirect limestone-gypsum method:

Common indirect limestone-gypsum methods include: sodium-alkali double alkali method, alkaline aluminum sulfate method and dilute sulfuric acid absorption method. Principle: Sodium alkali, alkaline alumina (Al2O3·nH2O) or dilute sulfuric acid (H2SO4) absorbs SO2, and the resulting absorption liquid reacts with limestone to be regenerated and generate gypsum. This method is simple to operate, has less secondary pollution, has no scaling and clogging problems, and has high desulfurization efficiency, but the quality of the gypsum product produced is poor.

C lemon absorption method:

Principle: Citric acid (H3C6H5O7·H2O) solution has good buffering performance. When SO2 gas passes through the citrate liquid, SO2 in the flue gas reacts with H in the water to form an H2SO3 complex. The SO2 absorption rate is above 99%. . This method is only suitable for low-concentration SO2 flue gas, but is not suitable for high-concentration SO2 gas absorption, and its application range is relatively narrow.

In addition, there are also wet flue gas desulfurization technologies such as seawater desulfurization method, ammonium phosphate compound fertilizer method, and liquid phase catalytic method.