First, the source of sulfur dioxide gas
SO 2 is currently the most harmful of air pollutants. China's annual emissions reached 15.2 million tons, ranking third in the world, causing environmental pollution and waste of sulfur resources.
Gold in the production process, SO 2 gas from the main sulfur ore. Flue gas containing SO 2 roasting pyrite, gold concentrate and the generated Alchemy.
Second, the purification and recovery of sulfur dioxide flue gas
(1) Recovery of high concentration sulfur dioxide gas
Such a sulfur dioxide flue gas contains a SO 2 concentration of 3.5% (volume percentage: V SO2 /V air) or more as a high concentration SO 2 flue gas. The contact method is used to produce sulfuric acid, which is free from pollution in the effluent atmosphere, and at the same time, the recovery of flue gas into a product, which has both economic benefits and air purification.
(2) Treatment of low concentration sulfur dioxide gas
1. Low-concentration SO 2 -containing flue gas, using high-altitude emission measures (usually a high chimney of about 50 m). However, in the case of rainy weather and low air pressure, SO 2 gas will be particularly sensitive to crops and fruit trees and vegetables, especially vegetables and beans. Therefore, it needs to be processed.
2, limestone - lime method
Purifying the exhaust gas with lime to remove SO 2 is the most effective conventional method. In some cases, when the concentration of SO 2 to be removed is very low, it is effective to use sodium hydroxide or sodium carbonate.
Although lime-purified exhaust gas can meet atmospheric regulations, there is a problem of handling gypsum solid waste generated by the reaction of SO 2 with lime. Gypsum produced, which may have other harmful elements such as arsenic , cadmium , lead , mercury, etc.
SO 2 emissions regulations vary widely across states in the United States. The following formula is used by the US state of Nevada to calculate the allowable sulfur emission formula (because Nevada has found a large number of difficult-to-lead gold deposits):
E=0.292×P 0.904
Where: E - allowable sulfur (S) emissions, kg / h;
P—Total sulphur (S) emissions in minerals, kg/h.
It should be noted that the above formula represents the emission of sulfur; in order to obtain the allowable amount of SO 2 emissions, the above formula E must also be multiplied by 2. In addition, the sulfur in the feed is indicative of total sulfur, including sulfur in the sulfide and other sulfur compounds.
If the above formula for sulfur emissions indicates that there is an equivalent of 250 tons of SO 2 emissions per year, then the roasting operation will be subject to lengthy and expensive “point emissions†reviews. Therefore, it is desirable to keep the SO 2 emissions below 250 t.
If the amount of SO 2 produced by the calcination is large, a highly efficient purification system is required to ensure that the SO 2 emissions are less than 250 t. In order to achieve such high purification efficiency, it is not technically feasible or expensive. Of course, if the amount of SO 2 in the exhaust gas is reduced, only a lower purification efficiency is required. As described above, any amount of SO 2 that is fixed by reacting with CaO or MgO upon firing will reduce the amount of SO 2 entering the exhaust gas. Therefore, it is important to evaluate and increase the fixation of SO 2 when testing according to the roasting scheme.
3. Activated carbon dry recovery
The Changsha Mine Research Institute believes that the use of activated carbon to recover SO 2 by experiments is not only technically feasible, but also has certain economic benefits.
Third, sodium alkali absorption treatment and recovery of sulfur dioxide
The sodium alkali absorption method uses Na 2 CO 3 or NaOH to absorb SO 2 in the flue gas, and a higher concentration of SO 2 gas and Na 2 SO 4 can be obtained.
Alkaline absorbent has more advantages: (1) the absorbent does not volatilize during the washing process; (2) has higher solubility; (3) there is no scaling and clogging problem in the absorption system; (4) high absorption capacity . According to different regeneration methods, there are sodium sulfite circulation method, sodium salt-acid decomposition method, and sodium sulfite method. Among them, the sodium sulfite cycle-thermal regeneration method develops rapidly.
The sodium sulfite cycle method uses NaOH or Na 2 CO 3 solution as the initial absorbent to absorb SO 2 in the flue gas at a low temperature, and generates Na 2 SO 3 , and Na 2 SO 3 continues to absorb SO 2 to form NaHSO 3 , which will contain The absorption liquid of Na 2 SO 3 -NaHSO 3 is thermally regenerated, releasing pure SO 2 gas, which can be sent to prepare liquid SO 2 or sulfuric acid and sulfur, and the Na 2 SO 3 crystal is obtained by heating and regeneration, and separated by solid-liquid separation. It is dissolved in water and returned to the absorption system.
Fourth, the adsorption method removes sulfur dioxide
Common activated carbon adsorbent, activated coal, activated alumina, zeolite, silica gel adsorbing SO 2. The adsorption process has physical adsorption and chemical adsorption. The adsorbed SO 2 is resolved by heating or decompression.
There are many different types of Forged flanges, such as weld neck flange, Plate Flange , Slip On Flange, Blind Flange , Socket Weld Flange, Threaded Flange, spectacle flange (sometimes it is called figure-8 blind flange), lap joint flange and so on.
Main materials are carbon steel, alloy steel and stainless steel. For carbon steel, ASTM A105 & A105N are required by most project.304/304L,316/316L,321,etc belong to stainless Steel Flange . The sealing face of forged flanges in common use is raised face(RF), flat face(FF) and ring type joint(RTJ). As one of largest flange suppliers in China, we commit ourselves to providing best quality and delivery time.
Forged Flange
Pipe Flange,Pipe Flange Types,Steel Flange,High Pressure Steel Flange
CANGZHOU HENGJIA PIPELINE CO.,LTD , https://www.hj-pipeline.com