A source of mercury-containing wastes
Mercury-containing wastes from different production systems, such as chemicals, petrochemicals, electronics, electrical instruments, measuring instruments, and many other industries to emit a certain amount of mercury-containing wastes. The amount of production varies by industry and process, among which the chemical industry contains the most mercury-containing waste, accounting for more than 50%. Mercury content also varies depending on the industry and technology, the content of the alkali salt slurry mercury emissions of mercury in water is Silver - 300mg / L; salvaged from the cell chamber periodically sweep mercury content of mercury in the slag is about 90% Above; the catalyst that is periodically replaced by the synthetic vinyl chloride industry contains about 4% to 5% of HgCl 2 . Therefore, it is important to properly dispose of mercury-containing waste and recover mercury from it. At present, mercury is recovered by roasting at home and abroad.
Second, the roasting method to recover mercury
1. Basic principle of mercury recovery by calcination The recovery of mercury by calcination method is based on the difference between the boiling point of mercury and the high boiling point of other components in solid waste. By controlling the calcination temperature, mercury is separated from the waste and recovered.
2. Process for recovering mercury by roasting process The process of recovering mercury by roasting method mainly includes mixing, granulating, roasting, condensing, recycling and the like. The operating procedures are as follows:
ï¬ of glass or metal mercury-containing waste, first of crushing processing, and washed with treatment agent; roasting roasting furnace and then made into a granular material; then adding an appropriate amount of lye, granulated by mixing, the humidity The calcination temperature is 400-800 ° C, and the generated mercury vapor is dedusted and sent to the condenser for condensation. After the condensate is refined, mercury with higher purity can be obtained.
ï¬ When mercury-containing waste is roasted, it is accompanied by wastes such as water, gas and slag, which need to be properly treated or disposed of. The composition of the exhaust gas after calcination varies depending on the type of roasting waste. For the harmful substances such as SO 2 and Cl 2 dust contained in the roasting, it is generally required to be treated by a series of purification devices such as a dust remover, a washing chamber, and an adsorber, and discharged after reaching the standard. For the water produced by the roasting system, according to the composition and concentration of the harmful substances contained in it, an appropriate method is selected to treat the discharged pollutants. For the residue after calcination, the mercury dissolution test is required first. If it is unqualified, it needs to be returned to the roasting, and the qualified residue is sent to the landfill for landfill treatment.
3. Application of Calcination to Recover Mercury At home and abroad, the use of roasting to treat mercury-containing waste has more practical experience. Japan's Itzuk Mining has long used this method to treat various mercury-containing wastes. The mine has a roasting unit that processes 3,600 tons of mercury-containing wastes per year, and recovers industrial mercury and fine mercury from mercury-containing wastes for 20 to 30 tons per year.
China's Jilin Chemical Plant and other units also use roasting to treat waste catalysts containing HgCl 2 and recover mercury. Shanghai Medical Instrument Factory uses roasting method to treat mercury-containing glass slag, which is treated with 400kg per month to recover 3~4kg of 99.9% mercury.
Third, the other method of roasting method to recover mercury is characterized by high purity of recovered mercury, and the residue contains less mercury after calcination, so it is a better method of harmless treatment and utilization.
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