Flue Gas Desulfurization

Flue gas desulfurization (FGD) refers to the removal of sulfur oxides (SO2 and SO3) from flue gas or other industrial exhaust gases.

In many countries, local environmental inspectors or governments strictly regulate greenhouse gas emissions such as sulphur dioxide (SO2). Nowadays, for a typical coal-fired thermal power plant, the wet scrubbing flue gas desulfurization device is the most popular, which can generally remove 90% or more of the sulfur dioxide in the flue gas.

Flue gas desulfurization is a technology to control a large number of low-concentration sulfur dioxide emissions, which is mainly used in coal-fired power plants and industrial boilers, and also for the purification and recovery of sulfur-containing tail gas such as sulfur recovery plants, chemical plants, smelters and sulfuric acid plants. If the absorbent is combined with sulfur dioxide to form sludge, it is treated as waste. If the absorbent absorbs or adsorbs sulfur dioxide, it can be converted into by-products with certain economic value, such as elemental sulfur, sulfuric acid or liquid sulfur dioxide.

In wet flue gas desulfurization systems, alkaline substances (usually alkaline solutions, more often alkaline slurries) meet flue gases in spray towers. SO2 in flue gas is dissolved in water to form a dilute acid solution, which then neutralizes with alkaline substances dissolved in water. The sulfites and sulfates produced by the reaction are precipitated from the aqueous solution, depending on the relative solubility of the different salts present in the solution. Wet FGD technology has the advantages of fast desulfurization reaction speed, simple equipment and high desulfurization efficiency.

The wet desulfurization tower is inseparable from the spray layer, which is composed of a spray pipe and a nozzle. These nozzles usually have four types: tangential-flow hollow cone, full cone, double hollow cone, spiral type.

The application environment of the desulfurization nozzle is relatively harsh, the corrosion of sulfurous acid and sulfuric acid, the wear and corrosion caused by calcium sulfite, calcium sulfate and calcium carbonate particles are the primary factors affecting the function and service life of the nozzle. Therefore, the materials used in the desulfurization nozzle are generally silicon carbide or ceramics, which have excellent sulfurous acid and sulfuric acid corrosion resistance, and their wear resistance is 15-30 times that of stainless steel (such as 316L).