Fluidized-bed reactor modeling for production of silicon by silane pyrolysis

An ideal backmixed reactor model (CSTR) and a fluidized bed bubbling reactor model (FBBR) were developed for silane pyrolysis. Silane decomposition is assumed to occur via two pathways: homogeneous decomposition and heterogeneous chemical vapor deposition (CVD). Both models account for homogeneous and heterogeneous silane decomposition, homogeneous nucleation, coagulation and growth by diffusion of fines, scavenging of fines by large particles, elutriation of fines and CVD growth of large seed particles. At present the models do not account for attrition. The preliminary comparison of the model predictions with experimental results shows reasonable agreement. The CSTR model with no adjustable parameter yields a lower bound on fines formed and upper estimate on production rates. The FBBR model overpredicts the formation of fines but could be matched to experimental data by adjusting the unkown jet emulsion exchange efficients. The models clearly indicate that in order to suppress the formation of fines (smoke) good gas-solid contacting in the grid region must be achieved and the formation of the bubbles suppressed

Standards relevant to transformers – Part III

CIGRÉ counts more than 3,500 experts from all around the world working together to optimise the existing equipment and power systems, including transformers

Standards relevant to transformers – Part IV

Last three parts of this series covered the evolution of Standards / Technical Brochures related to Power Transformers under IEC, IEEE and CIGRE and listed current standards issued by them. Now we see the evolution of transformer standards in Britain and the current position of European Standards (EN) on Transformers

Standards relevant to transformers – Part I

Standards are formulated to meet the generally recognised demands, minimum performance and safety requirements, as well as to make sure that the product from different manufacturers is similar and consistent. A survey is done on the evolution of national standards for transformers and of the range of IEC / IEEE standards available today for transformer engineers. Of course, standards are dynamic and are under continuous revisions and additions. Hence, no claim is made that the listings provided are the latest or include all relevant standards connected with transformers. A listing of standards, if made, as in this contribution in groups – viz. Application guides, Specification, Testing, Transformer Oil, Accessories, Raw Materials, Installation, Operation, Maintenance and Protection, with relevant IEC and IEEE standard numbers for each subject – will be useful as a quick reference for transformer engineers engaged in the selection, procurement, manufacturing, testing, installation, operation, maintenance, and protection of transformers. A list of CIGRE technical brochures relevant to transformers is also included

Standards relevant to transformers – Part II

The first step taken by the American Institute of Electrical Engineers (AIEE, formed in 1884) towards the standardisation of electrical apparatus and methods, was a discussion on the standardization of generators, motors and transformers, which took place simultaneously in New York and Chicago on 29 January 1898. A committee was appointed by the Council of the Institute under the chairmanship of Prof. Francis B. Crocker, and included eminent electrical engineers of the day, such as Charles P. Steinmetz, Lewis B. Stillwell (Niagara Power Company) and Elihu Thomson. The first standard (or ‘rules’, as they were called then), was presented and adopted by the Institute on 26 June 1899. This common standard for generators, motors and transformers was subsequently revised ten times during the next 22 years. In 1907, a standing committee, called the Standards committee, was constituted to continually monitor and revise this standard. This committee continued to grow over the years with several subcommittees to work on individual products required for electric power industry. Over the years, the input into the standardisation rules was also obtained from the Association of Edison Illuminating Companies (AEIC), the Electric Power Club (later to become the National Manufacturers Association, NEMA), the National Electric Light Association (NELA, the forerunner to the Edison Electrical Institute, EEI), and others. In parallel to AIEE, these organisations also began to issue standards. For example, in 1916, NELA issued a report on the standardisation of power ratings, voltages and taps for transformers (probably the first exclusive US), and NEMA standards on transformers that are still in vogue today. AIEE standards committee formed a separate subcommittee (No. 8) for transformers in 1918. Until 1921, transformer standard was a chapter in the common rules of standardization, titled Stationary induction apparatus

Standards relevant to transformers – Part XIII

Transformer engineers may come across some IEEE standards on Industrial Power Systems. Even though not directly related to transformers, these will be referred to in connection with the application and protection of transformers. IEEE Color Books were the most comprehensive collection of recommended practices for industrial power systems, prepared and issued by IEEE. They are being superseded by IEEE 3000 Standard Collections, also known as the 3000 series “dot” standards