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Application of Zhengguang ion exchange resin in polysilicon production

Release time: 2022-01-26

The rapid development of global economy has brought huge consumption of energy.  Due to the non-renewable nature of traditional energy sources such as oil, coal and natural gas, human beings are facing great challenges in energy sources and consumption, and the situation will become more and more severe.  The solutions are as follows :(1) improve scientific and technological progress, develop new production technology and reduce production energy consumption; (2) Develop new energy sources, such as solar energy, wind energy, hydrogen energy, tidal energy and biomass energy, so as to diversify the available energy sources and reduce dependence on oil, coal and natural gas.

As a kind of clean energy, solar energy occupies an important position in the new energy category because of its "inexhaustible and inexhaustible" characteristic.  Polysilicon is the most important material for solar cells.  In recent 3~5 years, polysilicon industry has developed rapidly in the world, especially in China.  Existing domestic and international mainstream technology, solar energy polysilicon mainly adopts improved Siemens method, silane method, the improved Siemens method accounted for about 80% of the chemical hydrogen silicon required for the production of polysilicon theory consumption ~ 5 t/t, but because of the reduction reaction selectivity is not high, equipment design is reasonable, the craft is not perfect, and many other factors, the actual consumption is much higher than the theoretical value,  At the beginning of the operation of polysilicon production unit, the single consumption of trichloro silicon reached more than 20t/t. In recent years, with the continuous progress of technology, the single consumption has gradually decreased to 8-10t /t.  It is estimated that the capacity of polysilicon projects already built and under construction in China will reach tens of thousands of tons per year.  In this way, it is bound to drive a large demand for trichlorosilane.  As the most important raw material in the process of polysilicon production, trichloro silicon in China from the real large-scale industrial production started to the present, although it is only a few years, but the development speed is amazing.  From the initial period of ~ 4kT /a in 2004, to 300~ 400kT /a in 2009.  
The modified Siemens process and silane disproportionation process are the process of purifying and separating the material and then reducing or decompactifying it.  In the process of purification and separation, impurity boron is difficult to remove and easy to enrich in the system, which has a great impact on product quality.  In addition, during the production process, the system will produce a certain amount of dichlorodihydrosilicon, which belongs to the class A hazard source and is easy to corrode the system equipment pipeline. How to effectively use it is a major problem for polysilicon manufacturers.  Macroporous adsorption resins for boron removal and catalytic resins for disdisproportionation of dichlorodihydrosilicon have been developed and applied in polysilicon production.  
In polysilicon production, boron and phosphorus in raw materials mainly exist in the form of boron trichloride and phosphorus trichloride, which affect the product quality.  Boron, phosphorus removal can be used in polysilicon has been of boron or phosphorus chelating resin with high selectivity, the functional groups on the chelating resin with boron or phosphorus form stable ligand, under the condition of reasonable design process, which can realize the boron or phosphorus content in the liquid chemical hydrogen silicon reduced to 5 parts per the following, from thousands of parts per so as to achieve the goal of boron, phosphorus removal.  Polysilicon raw material can provide high quality and stable raw material for distillation section by removing boron and phosphorus by chelating resin, which can reduce the load of distillation section, improve the yield and reduce the energy consumption of the product.  
Dichloro dihydrogen silicon boiling point only 8.3 ℃, 58 ℃, spontaneous combustion stability of strong corrosive gases, white smoke produced in the air, in the flame, high fever, the combustion or explosion happens, not easy to spot long-term storage, so two chlorine two recycling and utilization of hydrogen silicon can not only effectively eliminate the safety hidden trouble, but also to a certain extent reduce the production cost.  The Di disproportionation process, developed and applied by UCC, is an important method for the recovery of dichlorodihydrogen silicon.  
Di disproportionation working principle: catalytic resin  
Main reaction: SiH2Cl2+ SiCl4 → 2SiHCl3  
Side reaction: SiH3Cl+ SiCl4 →2SiH2Cl2  
2SiH3Cl → SiCl4 + 2SiH2Cl2  
Di disproportionation catalysts are mainly cyanide, activated carbon, chloride, heterocyclic, amine or amine salt and amide, supported catalyst, widely used is alkaline macroporous catalytic resin.  
Will liquid dichloride dihydrogen silicon and silicon tetrachloride according to certain proportion of mixed in pipeline mixer, mixing after send buffer tank, again through the pump to the disproportionation preheater, after preheating material sent to the catalytic reactions in fixed bed reactor, reaction products after cooler, then send purification system, through the disproportionation reaction,  Most of dichlorodihydrosilicon and equal mole of silicon tetrachloride are converted to trichlorodihydrosilicon, effectively recovering dichlorodihydrosilicon and silicon tetrachloride.  
In disproportionation reaction, the dichlorodihydrosilicon conversion will increase until reaching a stable value when the feed ratio of dichlorodihydrosilicon increases.  As the reaction temperature increases, the conversion rate of dichlorodihydrosilicon will increase, but the excessively high temperature catalyzes the fall off of the active group of the resin and leads to a decline in the conversion rate, thus controlling the temperature change of the reactor, which is generally 80℃.  In the process of disdisproportionation reaction, SiH2Cl2, SiCl4, SiHCl3, SiH3Cl and SiH4 are involved. They have a common characteristic. Under the action of appropriate catalyst, the chemical bond between chlorine atom and hydrogen atom and silicon atom can be opened freely, so that the chlorine atom and hydrogen atom surrounding silicon atom can transfer to each other.  And transfer the balance after the formation of the mixture depends on the properties of chlorine atoms and the ratio of silicon atoms, as a result, in particular the bed under the pressure of chlorine atoms and the higher the ratio of silicon atoms, dichloro dihydrogen silicon conversion rate is higher, the higher the temperature of the catalyst, the higher activity, open the higher chloride silicone key ability, dichloro dihydrogen silicon conversion rate is higher.  

As a leading ion exchange resin manufacturer in China, Zhengguang is manufacturing an extensive resin series,
and delivering the supporting equipment and EPC project of separation & purification process.


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