Industrial silicon industry chain structure
Silicon industry is an important part of China's non-ferrous metal industry, which has been widely concerned at home and abroad in recent years. Industrial silicon, also known as metallic silicon, is formed by high-temperature reduction reaction of carbonaceous reductants such as silicon ore (mainly composed of silicon dioxide), charcoal, coal and petroleum coke. Its impurities mainly include iron, aluminum and calcium. According to the content of iron, aluminum and calcium, it can be divided into 553, 441, 411, 421, 3303, 3305, 2202, 2502, 1501 and 1101.
The upstream of the industrial silicon industry is the manufacturing of chemical raw materials, mainly including silicon block, thermoelectricity, reductant, petroleum coke, etc. the downstream products are mainly divided into polysilicon, organosilicon and aluminum alloy, and the terminal applications are mainly electronic devices, daily chemical products, photovoltaic, semiconductor, automobile manufacturing, real estate and other fields. Industrial silicon plays a special role in China's economic and social development. It is an indispensable and important material for the development of new energy and new material industries, showing a broad application prospect.
Upstream of industrial silicon
Silicon ore is the most important raw material for industrial silicon smelting. It is also the general name of vein quartz, quartzite and quartz sandstone. Pure silica can be used as quartz glass (1718, 29.00, 1.72%) or refined monocrystalline silicon. The appearance of crystalline silica is generally milky white, gray white, light yellow and reddish brown. It has bright luster, smooth and continuous section, with sharp edges and corners, and great hardness and strength. The vein quartz is dense and massive, pure white, translucent, greasy and shiny, the cross section is shell shaped, and the quartz crystal particles are mostly more than 2mm, which can be recognized by the naked eye. Quartz sand mainly refers to river sand, sea sand, weathered sand, etc. with more silicon dioxide. In addition to silicon dioxide, it also contains iron oxide, clay, mica and organic impurities. Quartz sand can be divided into quartz sand, quartz powder, ultra-fine silica powder, cristobalite and high-purity quartz according to the grade and processing degree of the ore body.
In terms of silica resource types, the quantity of quartzite in China is 2.09 billion tons, accounting for 53.35% of China's silica resource reserves; 1.23 billion tons of natural quartz sand, accounting for 31.5%; The second is quartz sandstone and vein quartz, which are 560million tons and 400million tons respectively, accounting for 14.22% and 0.93%.
In terms of geographical distribution, there are 150 silica mines in China. Quartzite ores are mostly distributed in Qinghai, Liaoning, Shanxi and other places; quartzite sandstone ores are mostly distributed in Sichuan, Hunan, Jiangsu, Zhejiang, Shandong and other places; Quartz sand is mainly distributed in the coastal areas of Fujian, Guangdong, the south of Guangxi, the northwest of Hainan and the north of Shandong, as well as in the east of Xiliao River, the middle reaches of the Yellow River, Panyang lake and Luoma Lake. Gangue deposits are scattered in the metamorphic rock areas of Xichuan, Heilongjiang and Hubei. There are 31 mineral reserves in Northwest China, with a total of 1.91 billion tons of ore reserves, accounting for 48% of the total ore reserves in China. They are mainly quartzite ores distributed in Datong, Qinghai and Hanzhong, Shaanxi, quartz placers in Shenmu, Ningxia Huinong, Xinjiang Kuche, Gansu, and quartz placers in Lanzhou, Gansu, Changji, Xinjiang and Guyuan, Ningxia. In addition, the utilization rate of retained reserves in Northwest China is 7%.
In addition to silicon ore, the upstream raw materials of industrial silicon also include petroleum coke, charcoal, bituminous coal and other reductants. In the reduction reaction, the carbonaceous reductant mainly provides sufficient reduced carbon for the reaction, and is also the main conductor of current in the submerged arc furnace. Industrial silicon of different quality grades can also be obtained by changing the type and amount of reducing agent.