New technologies for solar energy silicon—Cost analysis of dichlorosilane process

New technologies for producing polysilicon are being developed to provide lower cost material for solar cells which convert sunlight into electricity. This article presents results for a process to produce dichlorosilane (DCS) as a silicon source material for solar energy silicon. Major benefits of dichlorosilane include faster chemical vapor deposition of silicon and higher chemical equilibrium yield for silicon production. Hemlock Semiconductor Corporation has recently demonstrated that under comparable conditions and for rods up tp 42 mm dia., deposition rates and conversions for dichlorosilane are approximately twice those for trichlorosilane. Cost, sensitivity and profitability analysis results are presented based on a preliminary process design of a plant to produce dichlorosilane by the DCS process. Profitability analysis indicates a sales price of $1.29–$1.47/kg of dichlorosilane (1980 dollars) at a 0–15 per cent discounted cash flow rate of return after taxes. These results indicate good potential for dichlorosilane as a silicon source material to provide lower cost material for solar cells.     

Development and integration of new processes consuming carbon dioxide in multi-plant chemical production complexes

Fourteen new energy-efficient and environmentally acceptable catalytic processes have been identified that can use excess high-purity carbon dioxide as a raw material available in a chemical production complex. The complex in the lower Mississippi River Corridor was used to show how these new plants could be integrated into this existing infrastructure using the chemical complex analysis system. Eighty-six published articles of laboratory and pilot plant experiments were reviewed that describe new methods and catalysts to use carbon dioxide for producing commercially important products. A methodology for selecting the new energy-efficient processes was developed based on process operating conditions, energy requirements, catalysts, product demand and revenue, market penetration and economic, environmental and sustainable costs. Based on the methodology for selecting new processes, 20 were identified as candidates for new energy efficient and environmentally acceptable plants. These processes were simulated using HYSYS, and a value-added economic analysis was evaluated for each process. From these, 14 of the most promising were integrated in a superstructure that included plants in the existing chemical production complex in the lower Mississippi River corridor (base case). The optimum configuration of plants was determined based on the triple bottom line that includes sales, economic, environmental and sustainable costs using the chemical complex analysis system. From 18 new processes in the superstructure, the optimum structure had seven new processes including acetic acid, graphite, formic acid, methylamines, propylene and synthesis gas production. With the additional plants in the optimal structure the triple bottom line increased from $343 million per year to $506 million per year and energy use increased from 2,150 TJ/year to 5,791 TJ/year. Multicriteria optimization has been used with Monte Carlo simulation to determine the sensitivity of prices, costs, and sustainability credits/cost to the optimal structure of a chemical production complex. In essence, for each Pareto optimal solution, there is a cumulative probability distribution function that is the probability as a function of the triple bottom line. This information provides a quantitative assessment of the optimum profit versus sustainable credits/cost, and the risk (probability) that the triple bottom line will meet expectations. The capabilities of the chemical complex analysis system have been demonstrated, and this methodology could be applied to other chemical complexes in the world for reduced emissions and energy savings. The system was developed by industry–university collaboration, and the program with users manual and tutorial can be downloaded at no cost from the LSU Mineral Processing Research Institutes website .     

New technologies for solar energy silicon: Cost analysis of BCL process

New technologies for producing polysilicon are being developed to provide lower cost material for solar cells which convert sunlight into electricity. This article presents results for the BCL Process (Battelle Columbus Laboratories), which produces the solar-cell silicon by reduction of silicon tetrachloride with zinc vapor. The UCC Silane Process (Union Carbide Corporation) was reported in a previous article.Cost, sensitivity and profitability analysis results are presented based on a preliminary process design of a plant to produce 1000 metric tons/year of silicon by the BCL Process. Profitability analysis indicates a sales price of 12.1–19.4$/kg of silicon (1980 dollars) at a 0–25 per cent DCF rate of return on investment after taxes. These results indicate good potential for meeting the goal of providing lower cost material for silicon solar cells.     

Application of factor method for minimum reflux: Multiple feed distillation columns

Analytical equations for determining the minimum reflux ratio of multiple feed distillation columns are presented by using a factor method. For the method, a factor which converts feed flow to minimum reflux ratio is used. The factor is a function of the feed concentration and thermal condition. The calculation steps for determining minimum reflux ratio of multiple feed columns are summarized. A computer program is available (microcomputer or mainframe). Application of the factor method for minimum reflux ratio is illustrated by several examples.     

A prototype system for economic,environmental and sustainable optimization of a chemical complex

A prototype of a chemical complex analysis system has been developed and used to demonstrate optimization of a chemical complex. The system incorporates economic, environmental and sustainable costs, and solves a MINLP for the best configuration of plants. It was applied to expanding production of sulfuric and phosphoric acid capacities and to evaluating heat recovery options at a major chemical company, and the results were compared to the company's case study. The system selected the better of two sites for required new phosphoric and sulfuric acids production capacities and selected, sited, and sized the optional heat-recovery and power-generation facilities. System capability was demonstrated by duplicating and expanding the industrial case study. A second application of the prototype was based on an agricultural chemical complex with ten multiple plant production units as found in the Baton Rouge–New Orleans, Mississippi river corridor. The optimal configuration of units was determined based on economic, environmental and sustainable costs. A comparison of the current configuration with the optimal one was made, and sensitivity to cost and prices was analyzed. The profit increased about 7.8% from the base case to the optimal solution. Also, environmental cost declined about 17%, and sustainability costs increased about 1.5%. These results illustrated the capability of the system to select an optimum configuration of plants in an agricultural chemical complex and to incorporate economic, environmental and sustainable costs. A brief sensitivity study gave predictable results and demonstrated additional capabilities of the system. Electronic Publication     

New technologies for solar energy silicon: Cost analysis of UCC Silane Process

New technologies for producing polysilicon are being developed to provide lower cost material for solar cells which convert sunlight into electricity. This article presents results for the UCC Silane Process (Union Carbide Corporation Silane Process). Other processes being developed will be presented in forthcoming articles.

Cost, sensitivity and profitability analysis results are presented based on a preliminary process design of a plant to produce 1000 metric tons/yr of silicon by the UCC Silane Process. The profitability results indicate a sales price of 9.88 $/kg of silicon (1975 dollars) at a 20 per cent DCF return on investment after taxes. These results indicate good potential for meeting the 1975 LSA cost goal of $10 per kg.