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Renewable energies: practically inexhaustible - like our ideas.
Renewable energies, also known as regenerative or alternative energies, are energy sources that are either practically inexhaustible or quickly regenerate themselves. "Renewable" should not be understood in the physical sense: energy can neither be created nor destroyed, but merely transformed into different forms.
Sustainable, usable energy resources include wind energy, water power, solar energy, geothermal energy and renewable raw materials. Renewable energies and energy efficiency are the most important elements of modern, sustainable energy management. In this context, it is essential to have processes that obtain or provide energy with the minimum depletion of resources.
The EPC Group has the technologies that enable renewable raw materials and natural sources of energy to be used efficiently in a wide range of applications. Our engineers and teams of developers combine their years of experience and their know-how to plan and deliver complete plants for the solar industry and the generation of biogenic fuels, including the necessary ancillary plants. We respond quickly and methodically to new market developments, legal directives and trends. We aim to provide high-quality technological solutions that meet requirements and give our customers long-term competitive advantages.
The method of producing ultrapure silicon from metallurgic silicon is based on the thermal decomposition of highly pure, rectified chlorosilanes or silanes to form silicon with the separation and recycling of gaseous byproducts. The conventional commercial technology passes through the stage of producing trichlorosilane in a fluidized-bed reactor from metallurgic grade silicon and hydrogen chloride. The trichlorosilane is then subjected to multi-stage rectification until the purity required for the desired application is reached (solar grade or electronic grade). The thermal decomposition of trichlorosilane in a chemical vapor deposition (CVD) reactor to form silicon at 900 °C creates a mixture of gaseous by-products, which have to be prepared for recycling (vent gas recovery) back into the process. We have optimized the process for producing ultrapure silicon from monosilane. It now offers a significantly higher efficiency as temperatures are only around 600 °C, and the collection efficiency has been increased to almost 100% in comparison to the mere 25% achieved by conventional processes. Monosilane is obtained by the disproportionation of trichlorosilane and recirculation of the disproportionation products. Trichlorosilane is thus required in both methods.
The gas mixture produced by the thermal decomposition of trichlorosilane in a chemical vapor deposition (CVD) reactor has to be separated into its constituent parts before the individual products can be recirculated. The monosilane method does not need these cycles, however Vent Gas Recovery is still part of our range or products.
The monosilane synthesis gas is stored temporarily in vacuum-insulated containers prior to further processing or filling. The containers are equipped with a pressure build-up vaporizer and an internal cooling coil to facilitate cooling. The containers are a special product of our subsidiary company, CRYOTEC, which specializes in special cryogenic applications.
Silicon tetrachloride is the main by-product of both the production of trichlorosilane from metallurgic silicon with HCl in a fluidized-bed reactor and the disproportionation of trichlorosilane. The thermal decomposition of trichlorosilane in a CVD reactor also creates large quantities of silicon tetrachloride. The silicon tetrachloride is converted with hydrogen into trichlorosilane in a conversion reactor. This process can be run homogeneously with hydrogen at approximately 1,000 °C in graphite reactors. We use the more elegant heterogeneous method of controlling the process by feeding silicon into a fluidized-bed reactor.