The purity of polysilicon required by photovoltaic industry is over 99.9999%. At present, the silicon materials produced by most manufacturers in the world adopt the traditional improved Siemens method, which is the most mature and widely used technology. Compared with polysilicon produced by improved Siemens method, granular silicon produced by fluidizedbed reactor (FBR) has smaller volume, and its energy consumption and cost are greatly reduced.
 
Investment reduced by 30%, production power consumption reduced by 65%, and personnel reduced by 30% ...
GCL-POLY recently announced that after the company's fluidizedbed reactor (FBR) granular silicon 10,000 tons project was put into production, after production operation and demonstration by downstream customers, various indicators of granular silicon have made new breakthroughs-life cycle, and the tail carbon, crystal formation rate, yield per unit area and conversion efficiency are all ahead of the industry level.
After the announcement, it attracted great attention from the capital market and photovoltaic industry.
At present, the upstream raw material of photovoltaic power generation is mainly polysilicon prepared by improved Siemens method. After the advent of FBR granular silicon, some experts in the industry judged that granular silicon is expected to trigger a disruptive technological revolution in polysilicon manufacturing. So what kind of process product is FBR granular silicon? What is the difference between it and traditional polysilicon, and why can it rise suddenly? On April 2, the reporter of Digitalpaper conducted an exclusive interview with experts in the industry on these issues.
 
The price and quality of silicon materials are very important for photovoltaic power generation
 
As we all know, photovoltaic industry has a clear and clear industrial chain, and silicon materials, silicon wafers, cells, components and application systems are the five major links in the industrial chain. Among them, silicon materials and silicon wafers are in the upstream of photovoltaic industry chain.
Silicon material not only requires higher threshold of manufacturing and research and development, but also has great demand for capital. At the same time, the price and quality of silicon materials also play a vital role in the cost and efficiency of photovoltaic power generation.
In recent years, the development momentum of photovoltaic industry is getting better and better. In 2020, China's newly installed photovoltaic capacity will be 48.2GW, up 60% year-on-year. Driven by the terminal market and forced by national laws and regulations, all raw material enterprises concentrate on researching and developing new technology of silicon materials. Under this background, granular silicon has gradually entered people's sight.
Silicon is polysilicon, and the purity of polysilicon required by photovoltaic industry is over 99.9999%. At present, the silicon materials produced by most manufacturers in the world adopt the traditional improved Siemens method, which is the most mature and widely used technology.
 "The main principle of the improved Siemens method is to smelt quartz sand in an electric furnace, reduce it into 99% industrial silicon powder, and then react with silicon tetrachloride and hydrogen to obtain trichlorosilane, which is rectified, purified, reduced at high temperature. A series of technological processes such as tail gas recovery will eventually produce rod-shaped polysilicon." Jiang Limin, vice president of GCL-POLY Research Institute, said.
FBR granular silicon is also polysilicon, but compared with modified Siemens polysilicon, granular silicon is smaller and only as big as mung bean. Since 2010, Jiangsu Zhongneng Silicon Industry Technology Development Co., Ltd, a subsidiary of GCL-Poly, has independently developed granular silicon technology, and finally realized mass production of granular silicon by acquiring overseas assets.
 "GCL-Poly's granular silicon is manufactured by the original silane FBR. The raw material trichlorosilane is disproportionated to prepare silane, and the silane is decomposed in a fluidized bed to prepare granular polysilicon. The one-way conversion rate can reach 99%, reducing the tail gas recovery and rectification. The reaction temperature is only 60% of that of the improved Siemens method, which can be continuously produced, and the energy consumption and cost are greatly reduced." Jiang Limin told reporters.
According to the introduction, after the downstream silicon wafer manufacturers get the traditional polysilicon, they still need to break and clean it and then use it for pulling single crystal, while the granular silicon does not need to be broken and cleaned, and can be directly fed to pull single crystal with good fluidity, which is more suitable for a new generation of continuous feeding and direct pulling process compared with the traditional polysilicon.
 
　　Carbon neutralization puts higher demands on the photovoltaic industry chain
 
As early as many years ago, when the photovoltaic industry chain was introduced into China, there were voices questioning the high energy consumption of the photovoltaic industry chain, which caused pollution and greenhouse gas emissions higher than the power generation income.
With the progress of independent technology and practice test, this questioning voice has gradually disappeared. In view of the high energy consumption in the manufacturing of silicon materials and silicon wafers, it not only restricts the cost reduction of photovoltaic power generation, but also affects the realization of the goal of "carbon peaking and carbon neutralization" in China.
According to industry insiders, at present, the highest energy consumption in the photovoltaic industry chain is the manufacturing of silicon materials, accounting for 45%. In May 2020, the Ministry of Industry and Information Technology issued the Standard Conditions for Photovoltaic Manufacturing Industry (2020 Edition) (draft for comments), which stipulated that the comprehensive power consumption of new/expanded polysilicon should not exceed 70 kWh/kg.
 "according to our actual measurement, the comprehensive power consumption of FBR granular silicon is only 18 kwh/kg, far below the industry standard.” Jiang Limin said.
China has promised that the total installed capacity of wind power and solar power will reach more than 1.2 billion kilowatts by 2030, which will drive a large number of photovoltaic power generation projects to be put into operation. Against the specifications of the Ministry of Industry and Information Technology,  the reporter，according to the production process of FBR granular silicon and modified Siemens polysilicon，traced the carbon footprint of polysilicon modules produced by these two in the whole photovoltaic industry chain. It can be seen that the production of 1 GW granular silicon only in the silicon material link can reduce carbon dioxide emissions by 130,000 tons, which is 74% lower than that of the improved Siemens method. From the perspective of the whole industrial chain, the production of 1 GW components can at least reduce carbon dioxide emissions by 47.7%.
Thanks to the advantages of production capacity, cost control and technology, the focus of the world photovoltaic industry has gradually shifted to China. By 2019, China's output in polysilicon, silicon wafers, cells and components has accounted for more than 60% of the world, which are 67%, 97%, 79% and 71% respectively.
Based on the domestic silicon production capacity of about 430,000 tons in 2020, according to Siemens method replaced by FBR, this will definitely reduce carbon dioxide emissions by 19.27 million tons every year. According to the research of Swiss Federal Institute of Technology in Zurich, one hectare of tree planting area can consume 205 tons of carbon dioxide every year, and 19.27 million tons of carbon dioxide needs 94,000 hectares of crown area, which is equivalent to about 94 million trees planted every year.
In order to eliminate backward photovoltaic production capacity, the Ministry of Industry and Information Technology has clearly stated that "photovoltaic manufacturing enterprises should adopt production technologies and equipment with advanced technology, energy conservation and environmental protection, good product quality and low production cost".
Jiang Limin told the reporter of Digitalpaper that after 10 years of research and improvement, FBR granular silicon has solved the problems of large-scale industrialization such as product quality, long-term continuous operation and low cost. In 2019, due to the localization of key equipment and the substitution of key materials, GCL-POLY also led and edited the national standard of granular silicon. In the future, FBR granular silicon will play a vital role in reducing carbon emission in China's photovoltaic industry chain.

 
 
来源：科技日报