A Brief Discussion on the Upgrading of China’s Industrial Silicon Industry

Thread Content

A Brief Discussion on the Upgrading of China’s Industrial Silicon Industry Abstract: This paper provides a brief overview of the current status of China’s industrial silicon industry and the necessity for its upgrading. It discusses specific ways to accelerate this upgrading, such as by promoting structural adjustments in the industry, focusing on energy conservation in industrial silicon production, improving waste gas treatment, increasing investment in technology, fostering technological progress and innovation, using industrial silicon furnaces with larger capacity where appropriate, and developing a circular economy to make better use of waste materials. China’s industrial silicon production has grown from nothing to a major producer in the world, ranking first globally in terms of capacity, output, and exports after more than 50 years of development. However, for many years, the production and export of industrial silicon in China have been characterized by uncontrolled development and chaotic competition; as a result, the efficiency of enterprises’ production and product exports has been poor. This situation must be rapidly changed through continuous strengthening and improvement of macro-control, along with efforts from all parties and industrial upgrading. Below are some of my personal thoughts and opinions on this matter, provided for your reference. 1. The current status of China’s industrial silicon industry and the need for upgrading. China’s production of industrial silicon began in 1957, and it has been over 50 years since then. From the late 1950s to the late 1970s, China’s production of industrial silicon was used for domestic needs only, achieving self-sufficiency. China began exporting industrial silicon in 1980, and as export volumes increased rapidly thereafter, industrial silicon production across the country grew at a swift pace. By the end of the 1980s, China’s annual export volume of industrial silicon exceeded 100,000 tons; by the end of the 1990s it rose above 200,000 tons, and in 2007 the export volume increased to nearly 700,000 tons. Currently, China ranks first in the world in terms of production capacity, output, and exports of industrial silicon. China’s annual production of industrial silicon has reached about 1.2 million tons. The number of countries and regions to which industrial silicon is exported is nearly 60, and the annual export volume already accounts for more than half of the total consumption in developed Western countries. China’s production and exports of industrial silicon have a significant impact on the global silicon industry as well as on the development of related industries. There is no doubt that our country is a major producer and exporter of industrial silicon in the world. But it is not a strong exporter of industrial silicon. For many years, the profitability of industrial silicon production and exports has been poor. Since the early 1990s, the price of industrial silicon exported from our country has remained significantly low, often 20–30% lower than the normal prices in the international market, and in some cases even as low as 50% lower. Since the second half of 2007, and particularly since the beginning of 2008, the export prices of industrial silicon in our country have risen significantly. In 2007, the average offshore price for China’s industrial silicon exports for the whole year was 1,381 US dollars per ton, while the average offshore price from January to May this year has risen to 2,001 US dollars per ton. At the same time, however, the price of industrial silicon in the international market was also rising rapidly; during that period, the spot prices of industrial silicon in the United States and the European Union increased from around 2200 dollars per ton to around 3500 dollars per ton. The reason for the consistently low prices of China’s industrial silicon exports is, in addition to the anti-dumping measures imposed by countries such as the United States and the European Union, also related to the reckless expansion of industrial silicon production projects in China, low-level repetitive construction, and disorderly price competition among producers. Since 2004, **a series of macro-control policies have been introduced to continuously strengthen and improve macro-control over resource-based industries that are highly energy-intensive and polluting, including industrial silicon. Under the **increasingly stringent macro-control measures, it can be said that the trend of low-level repetitive construction of industrial silicon projects has been somewhat curbed; outdated production capacities are beginning to be phased out, and there is a growing awareness of energy conservation and environmental protection. However, it must be acknowledged that while these initial achievements have been made, the problem of excessive and uncontrolled expansion over the long term remains severe. The entire silicon industry still has a lot of work to do if it is to truly curb this trend of uncontrolled expansion and eliminate disorderly competition. Since 2008, **a 10% export tariff has been imposed on exported industrial silicon starting from January 1, and the average selling price of electricity across the country was increased by 2.5 cents per kilowatt-hour starting from July 1. These macro-control policies and measures all have a significant impact on the development of China’s silicon industry. Since February this year, provinces and regions in China such as Hunan, Guizhou, Guangdong, and Jiangxi, as well as provinces and regions like Sichuan, Shaanxi, Gansu, and Yunnan, have successively suffered from historically rare low-temperature, snowstorm, and freezing disasters, as well as severe earthquake disasters. These disasters not only caused severe losses to the lives and property of ** and its people, but also led to varying degrees of damage to a considerable number of industrial silicon enterprises in these areas, adversely affecting production and trade. **The increasing intensity of macro-control measures and the successive natural disasters pose serious challenges to the development of China’s industrial silicon industry, yet they also present valuable opportunities for its growth. Prolonged low-level repetitive construction and disorderly competition not only result in poor export performance, but also lead to outdated business operations and equipment, making it difficult to improve technical management levels. In order to help China’s silicon industry overcome its current difficulties, turn it into an industry with an advantage in international competition, and establish it as a solid foundational industry that ensures the rapid development of the national economy and high-tech sectors, we must, under **continuous strengthening and improvement of macro-control, pay attention to and accelerate the implementation of various specific measures and steps for industrial upgrading, so as to promote the upgrading of the industrial silicon sector. 2. Pathways for industrial upgrading 2.1 Promoting structural adjustments in the industrial silicon industry. With ongoing strengthening of macro-control, and as affected enterprises rebuild, their performance varies – some see improvements while others experience declines – which presents an opportune time for structural adjustments in the industry. Companies in the silicon industry will gradually realize the necessity of accelerating industrial structure adjustment, become more proactive, and speed up the phasing out of outdated production capacities as well as the reduction in the use of small-scale industrial silicon furnaces. Gradually, the industrial structure will shift from high consumption to high efficiency, and from rough processing to refined processing. In the adjustment of the industrial structure, it is also necessary to accelerate corporate restructuring and the consolidation of enterprises in order to form several enterprise groups. Competent enterprise groups can use assets, resources, brands, etc. as links to achieve cross-regional and cross-industry reorganization, thereby promoting the intensification and expansion of industries. Along with the adjustment of the industrial structure, it is also necessary to promote a division of labor and cooperative relationship between small and medium-sized enterprises and large enterprises, as well as to facilitate the rational flow and allocation of production factors. Only by gradually expanding and strengthening enterprises can the competitiveness of China’s silicon industry be enhanced, allowing for more effective efforts to address foreign anti-dumping actions and to overcome price discrimination against Chinese industrial silicon exports in international markets. 2.2 Emphasis on energy conservation in the production of industrial silicon. Energy conservation and emission reduction have gradually become important means of macro-control. Vigorously promoting energy conservation and consumption reduction, as well as improving energy utilization efficiency, should be a long-term strategic task for the development of the industrial silicon industry, and it needs to be given top priority. The energy consumption in the production of industrial silicon involves various aspects, but it is primarily reflected in electricity usage, especially during the smelting process. Typically, melting each ton of industrial silicon requires 12,000 to 14,000 kwh of electricity, and the cost associated with electricity consumption often accounts for 40% or more of the total cost. Efforts to reduce electricity consumption during production, especially in the smelting process, are an aspect that must be given top priority. In the production of industrial silicon, once suitable production processes and equipment are available, along with raw materials that meet the required standards, it is essential to pay close attention to maintaining carbon balance during melting. The molecular ratio of C to SiO2 in the charge entering the reaction zone should be set to 2, so as to prevent an excess of SiC relative to SiO2 during the melting process, thereby achieving high yields with low consumption. In actual production, it is quite difficult to keep the molecular ratio of C to SiO2 in the charge entering the reaction zone at 2 at all times. Relying solely on accurate calculations of the charge, careful batching and mixing, as well as proper feeding and stirring of the material, is not sufficient; it is also necessary to improve the technical skills of the operators working at the furnace. This enables furnace supervisors, team leaders, and actual operators to promptly detect and accurately assess any excess or deficiency of carbon during the melting process, and to make careful adjustments in a timely manner. To reduce power consumption in the smelting of industrial silicon, it is also necessary to address various challenges such as the emission of CO and the capture of SiO, as well as furnace ramming and heat dissipation. During the smelting of industrial silicon, large amounts of CO are generated during the reduction of SiO2. Only by rapidly leaving the reaction zone can the reduction of SiO2 take place. However, during the melting process, a large amount of gaseous SiO product is also generated. SiO mixed with CO gas, if rapidly expelled from the furnace surface along with the CO gas, will result in significant losses of silicon and thermal energy, leading to a decrease in silicon production and increased energy consumption. Therefore, in the melting of industrial silicon, it is necessary to quickly remove CO while at the same time preventing the loss of SiO; these are two conflicting requirements that must be addressed properly in practical operations. In the melting of industrial silicon, it is also necessary to use ramming to force the charge to sink. To carry out furnace ramming, it is necessary to lift the material surface, breaking the closed arc condition; this causes a large amount of heat energy to spread and radiate into the surrounding space, resulting in energy loss and also harming the environment. Tamping the furnace is an essential operation at the furnace front in the melting of industrial silicon; it is also a harmful practice that increases energy losses and SiO escape, reduces product yield, and raises energy consumption. We must recognize the positive and negative effects of this operation, ensuring that the furnace is tapped at the right time and in an appropriate manner, while also reducing heat loss. 2.3 Ensure proper flue gas purification and dust recovery. During the melting of industrial silicon, a large amount of gaseous SiO is produced in the reaction zone; part of this gas escapes from the material surface and reacts with oxygen in the air, rapidly forming SiO2 particles with a particle size of less than 1 μm, which are then carried out of the furnace along with the furnace gases. These SiO2 particles are very fine (the smallest being 0.01 μm). It has a low density, strong adhesiveness, and high cohesion; it does not settle easily, but it can pollute the environment and harm human health. From the perspective of environmental protection and fulfilling social responsibilities, industrial silicon manufacturers must treat the flue gases from electric furnaces in order to reduce or even eliminate dust emissions. Compared to other pollutants, the dust emitted from industrial silicon furnaces has another notable feature: due to its fine particle size and high purity (with a SiO2 content of 90–94%, and in some cases as high as 98%), it holds significant practical value in various fields such as construction materials and the chemical industry. It is already being used in industrial and engineering applications. The amount of SiO2 dust recovered from the flue gas of industrial silicon furnaces varies depending on the operating conditions of the furnace; generally, 0.3 to 0.5 tons of SiO2 powder can be recovered per ton of silicon produced. Previously, such recycled materials were discarded as waste, but now they have become valuable new materials used in various fields such as construction and the chemical industry. Today, the technologies for treating flue gas and recovering dust from industrial silicon furnaces are highly mature, with dry bag filtration technology being widely used in practice in production. All industrial silicon companies should attach great importance to flue gas treatment and dust recovery, whether from the perspective of implementing energy-saving and emission-reduction policies, protecting the environment, and fulfilling social responsibilities, or from the standpoint of their own development, improving corporate profitability, as well as optimizing waste recycling and new product development. In terms of emission reduction, in addition to focusing on improving the treatment of flue gases and the recovery of dust from industrial silicon furnaces, industrial silicon manufacturers should also pay attention to the dust generated during the crushing, screening, and transportation of raw materials such as silica, charcoal, and petroleum coke, as well as of the final silicon product, and take measures to purify and recover this dust. 2.4 Increase investment in technology to promote technological progress and innovation. Industrial silicon is mainly divided into two categories based on its uses: silicon for metallurgical purposes and silicon for chemical applications. Silicon used in metallurgy is primarily employed in metallurgical applications such as the production of aluminum-silicon alloys. Silicon for chemical use is employed in the production of silicone, semiconductor materials, and solar-grade silicon, among other applications. Globally, metallurgical silicon and chemical silicon each account for roughly half. However, since the late 1990s, the amount of silicon used in chemical applications in the EU and the US has exceeded that used in metallurgical applications, and this trend continues, with silicon for chemical use accounting for an increasingly larger proportion. In other words, economic development and continuous technological progress are placing increasing demands on the types of industrial silicon as well as on the quality of its products. As a result, new technologies must be introduced to industrial silicon production, including the selection of high-quality raw materials, improvements in process conditions, and innovations in refining methods. The proportion of science and technology in products must continue to increase in order to meet the demands of new developments. Before the mid-1990s, China’s industrial silicon products were mainly of grade 553.441, and the majority of them were exported and used as silicon for metallurgical purposes. Since the end of the last century, China’s industrial silicon manufacturers and related enterprises have gradually increased their investment in research and development in areas such as raw material selection, improvement of processing equipment, and innovation in refining methods. Today, they are able to produce products of various grades, including 2202 and 1101, to meet the needs of different customers. Some of these enterprises can also produce silicon with very low levels of phosphorus and boron, as well as electronic-grade silicon suitable for the electronics industry, and solar-grade silicon with a silicon content of 99.99% or higher. In terms of improving product quality and expanding the range of products, our country has achieved good results by increasing investment in science and technology as well as fostering technological innovation. In the future, it is necessary to continue improving product quality and expanding the range of products, to focus on energy conservation and emission reduction, to increase the sources of high-quality minerals and reducing agents, to reduce product costs, and to enhance the international competitiveness of the industrial silicon industry. All of these require attention and increased investment in science and technology, as well as efforts to drive technological progress and innovation. 2.5 Appropriate use of industrial silicon furnaces with larger capacity: As macro-control is continuously strengthened, for some enterprises or enterprise groups that have undergone mergers and reorganizations, or for regions that have the conditions to supply energy and raw materials, it is necessary to research, develop, and appropriately construct several industrial silicon furnaces with a capacity of 20,000–30,000 kVA or even higher, if there is indeed a need to expand production. This is beneficial for adopting certain advanced technologies for flue gas treatment, the recovery and utilization of dust and energy, saving investment and reducing floor space, as well as for the long-term development of the entire silicon industry. However, for the small and medium-sized industrial silicon furnaces with capacities of 6300 kVA and around 10,000 kVA that are already in operation, aside from those that were designed poorly as a result of reckless expansion in recent years, were built carelessly, and have very poor performance metrics, such furnaces should be phased out. On the other hand, those small and medium-sized industrial silicon furnaces that were carefully designed or underwent thorough improvements after being put into operation, resulting in good technical and economic indicators such as low electricity consumption, should continue to operate as long as the production needs and conditions are met, and need not be eliminated as outdated production capacity. From the perspective of macro-control and management, it is necessary to encourage and support the development and construction of large-capacity industrial silicon furnaces. However, it is not advisable to continuously pursue larger furnace capacities and eliminate small and medium-sized industrial silicon furnaces without distinguishing between good and bad ones. Using the performance of various energy-saving and emission-reduction indicators as a criterion for choosing a furnace is far better than making decisions solely based on the furnace’s capacity. Our country has a vast territory, and the quality and quantity of raw materials and energy vary from one region to another. Small and medium-sized furnaces are more flexible than large-capacity ones, making it easier to start and stop them, as well as to make use of certain scattered surplus electricity and seasonal hydroelectric power. Furthermore, considering the diversity of applications for industrial silicon, the amount of this material used in high-tech fields such as the production of polysilicon and monocrystalline silicon is not large; however, the requirements regarding the quality of the raw material are quite high. To produce industrial silicon for these purposes, large-scale industrial silicon furnaces similar to those used in metallurgical applications are needed, which also presents difficulties in practice. Therefore, it is correct to generally require the use of high-capacity industrial silicon, but it is inappropriate to assume that, regardless of the type of industrial silicon being produced, the same high capacity must be used as in the case of ferrosilicon. 2.6 Develop a circular economy and improve the recycling of waste residues and other materials. Only by developing a circular economy, enhancing resource conservation, and improving the efficiency of resource utilization can the sustainable development capacity of the industrial silicon industry be continuously strengthened. Cooling water used in the production of industrial silicon, crushed silicon that does not meet the required particle size for the final product during silicon block crushing, and crushed materials derived from silica and reducing agents that fail to meet the specified particle size requirements after crushing and screening – all of these should be reused in the production process, either directly or after some treatment. Some industrial silicon companies have already combined the washed wood charcoal powder with petroleum coke and crushed coal, using water glass as a binder to form pellets, which are then used as reducing agents after drying. The silicon carbide and other materials removed from the furnace during major overhauls of industrial silicon furnaces can either be reused in the furnace or sold for use in the steel industry. The crushed silica that does not meet the required particle size specifications is unsuitable for use in the production of industrial silicon, as some of it contains high levels of impurities or affects the permeability of the charge; however, it can be sold or utilized in some new \"sand industries\". Some of these silica fragments can be used, just like quartz sand, in the casting of automobile components, engine blocks, cylinder heads, etc. They can also be used to manufacture permeable bricks with high strength and good water permeability, which are employed for paving flower beds, parking lots, sports fields, and even road surfaces. During the melting of industrial silicon, a large amount of gaseous SiO is produced in the reaction zone; a small portion of this gas escapes from the surface of the material and reacts with oxygen in the air to form SiO2 nanoparticles, which need to be recovered by the purification system. As mentioned above, these micro-powders can be used in products. A large amount of CO gas is also generated in the reaction zone, which must be rapidly removed from the feed surface. In the raw furnace gas emerging from the material surface, the CO content typically ranges from 60 to 75%, with 5 to 10% H2 present as well (H2 is generated through the reaction CO + H2O → CO2 + H2). When the industrial silicon furnace is well sealed and the original furnace gas is not mixed with large amounts of external air, recovering this original gas containing CO and H2 can be used in the chemical industry for various organic syntheses, such as the production of paraffins, alkenes, methanol, ethylene glycol, and others. Under normal circumstances, the recovered gas can also be used as fuel at any time according to the user’s needs. In industrial silicon furnaces where the airtightness is not very good, gases such as CO and H2 that escape from the material surface, as well as the volatile components of reducing agents present in the feedstock and any excess carbon in it, all react with oxygen in the air at the surface of the material, resulting in the release of large amounts of energy. How to recover and utilize this energy represents an area with great potential in efforts to save energy in industrial silicon production. After being recovered, this energy can be used for power generation and in many other applications that require heat energy. If this energy is recovered well, it can amount to about 25% of the electrical power required for silicon production. 3. Conclusion As a major global producer and exporter of industrial silicon, our country has seen poor productivity and export performance over the years. To change this unfavorable situation, we must, under continuous strengthening and improvement of macro-control, accelerate the upgrading of the industrial silicon industry. In line with the requirements of the scientific development concept, we need to focus on energy conservation, emission reduction, and resource efficiency, increase investment in science and technology, and speed up the shift in the economic growth pattern of this industry from one based on quantity to one based on efficiency. This will enable us to pursue a new path of development characterized by high levels of technological advancement, good economic returns, low consumption of resources and energy, minimal environmental pollution, and full utilization of human resources. This post was last edited by eastchen on 2009-4-6 18:11]