Rare earth smelting flue gas treatment
Flue gas generated from rare earth smelting process contains a large amount of pollutants such as sulfur dioxide, nitrogen oxides and dust, which have serious harm to the environment and human health. Due to the characteristics of rare earth smelting flue gas, it is necessary to carry out rare earth smelting flue gas treatment.
The main pollutants in rare earth smelting flue gas are sulfur dioxide, nitrogen oxides and dust. Sulfur dioxide in the flue gas is mainly from the oxidation of sulfur dioxide and the formation of sulfide in the smelting process. Nitrogen oxides are mainly the result of high temperature reaction of nitrogen in the air with oxygen in the air during smelting process or thermal cracking of nitrogen oxides. Dust mainly comes from the feed ore and some smelting processes.
In the treatment of rare earth smelting flue gas, according to the characteristics of flue gas, chemical methods such as desulfurization and denitrification, as well as physical methods such as dust removal, wet scrubber and electrostatic precipitation, are commonly used.
Firstly, desulfurization and denitrification generally use limestone, slaked lime or high calcium fly ash as desulfurizing agent. When the flue gas passes through the desulfurization and denitrification device, the sulfur dioxide and nitrogen oxides in the flue gas react with the desulfurizing agent, and the sulfur dioxide and nitrogen oxides are removed from the flue gas, so as to achieve the purpose of desulfurization and denitrification.
Secondly, dust removal refers to the use of special dust removal equipment to separate the suspended particles (dust) from the flue gas by gravity, inertia, centrifugal force and electrostatic force, and collect them directly or after the condensation of water vapor, so as to reduce the dust concentration in the flue gas.
Thirdly, wet scrubbing technology is a method to reduce the pollutant concentration in flue gas by gas-liquid contact. In the process of rare earth smelting, wet scrubbing technology is mainly used to reduce the dust concentration in the flue gas. That is, the dust particles in the flue gas are absorbed by liquid droplets with certain surface tension, so as to reduce the dust concentration in the flue gas.
Finally, electrostatic precipitation (ESP) is the most widely used method for removing particulate dust from flue gas. In this technology, the electric field of high voltage is used to form a corona on the electrodes. Under the action of corona discharge, the dust particles in the flue gas are ionized, charged and then collected on the ground electrode. Electrostatic precipitation can also be used for simultaneous desulfurization and denitrification.
In summary, there are mainly four approaches to the treatment of rare earth smelting flue gas, i.e. desulfurization and denitrification, dust removal, wet scrubbing and electrostatic precipitation. In order to achieve the effect of environmental protection, it is necessary to select a reasonable treatment process according to the on-site flue gas composition and concentration.
