Zhengjie Chen

Thermodynamic Estimation of Silicon Tetrachloride to Trichlorosilane by a Low Temperature Hydrogenation Technique

The chemical reactions in the SiCl4-Si-H2 system using a low temperature hydrogenation technique related to the Siemens process were studied based on thermodynamics. The diagrams of standard Gibbs free energy of formation and equilibrium constants for seven reactions used as a function of temperature in this system were calculated and plotted for a temperature range of 473 K to 1073 K. It showed that the lower the temperature, the larger the conversion ratio of SiCl4. The equilibrium composition of gaseous species in the SiCl4-Si-H2 system with different initial SiCl4/H2 ratio and systematic pressure was calculated and the corresponding conversion ratio of SiCl4 was obtained. The conversion ratio was improved by increasing the initial ratio of H2 in raw materials and the systematic pressure but was reduced with the increase of temperature. The conversion ratio of SiCl4 reached 0.41 with an initial SiCl4/H2 ratio of 1/5 and a systematic pressure of 5 MPa at 473 K.

An Innovative Metal Ions Sensitive “Test Paper” Based on Virgin Nanoporous Silicon Wafer: Highly Selective to Copper(II)

Developing an innovative “Test Paper” based on virgin nanoporous silicon (NPSi) which shows intense visible emission and excellent fluorescence stability. The visual fluorescence quenching “Test Paper” was highly selective and sensitive recognizing Cu2+ at μmol/L level. Within the concentration range of 5 × 10−7 ~50 × 10−7mol/L, the linear regression equation of IPL = 1226.3-13.6[CCu2+] (R = 0.99) was established for Cu2+ quantitative detection. And finally, Cu2+ fluorescence quenching mechanism of NPSi prober was proposed by studying the surface chemistry change of NPSi and metal ions immersed-NPSi using XPS characterization. The results indicate that SiHx species obviously contribute to the PL emission of NPSi, and the introduce of oxidization state and the nonradiative recombination center are responsible for the PL quenching. These results demonstrate how virgin NPSi wafer can serve as Cu2+ sensor. This work is of great significant to promote the development of simple instruments that could realize rapid, visible and real-time detection of various toxic metal ions.

Predicting the Electricity Consumption and the Exergetic Efficiency of a Submerged Arc Furnace with Raw Materials using an Artificial Neural Network

The problem of higher electricity consumption and lower exergy efficiency in the submerged arc furnace process of the silicon industry needs to be urgently solved. However, various raw materials play important roles in the electricity consumption and exergy efficiency of a submerged arc furnace during silicon production. An artificial neural network (ANN) method was used to model the final strain of the electricity consumption and exergy efficiency with varying silica, coke, coal and electrode. The measured strain versus predicted strain by the model was compared using the R2 coefficient. The results showed that the exergy efficiency and the electricity consumption values of the testing data are R2= 0.9918 and R2 = 0.9896, respectively, in a very short time with low error levels. They clearly indicate the adequacy of the model proposed for prediction of the exergy efficiency and the electricity consumption with different raw materials in the mixture of carbonaceous raw materials in the furnace. Additionally, there is good agreement between the actual and predicted values. Therefore, this developed ANN model is useful to guide the decision about the use of raw materials in silicon production under the condition of lower electricity consumption and higher exergy efficiency.

Application of a Waste Carbon Material as the Carbonaceous Reductant During Silicon Production

It is important to study the application of alternative carbon reductants for industrial silicon smelting to reduce consumption of carbonaceous reducing agents, electricity, and CO2 emissions during silicon production. In this study, an industrial experiment was carried out in an 8 MVA submerged arc furnace using waste carbon material in place of approximately 20% partial reducing agents. The system was analyzed for silicon yield, power consumption, overall energy efficiency, CO2 emissions, and the utilization rate of carbonaceous materials. The system improved the efficiency of carbonaceous materials and decreased power consumption using alternative carbon reductants. The results have showed that use of waste carbon materials reduced carbon emissions per ton silicon by more than 19.14% and specific CO2 emissions decreased to 0.865 t.

A Study of the Performance of Submerged Arc Furnace Smelting of Industrial Silicon

The consumption of energy and carbonaceous reductants is one of the more important factors that significantly influence the cost of industrial silicon production. The effect of raw materials on the silicon yield and the energy consumption in the process of producing silicon was investigated in this study using data collected from various submerged arc furnaces. Following analysis of a large quantity of industrial data, the results showed that a 12.5 MVA submerged arc furnace was the most efficient in utilizing the consumption of coal. In addition, the 8 MVA furnaces consumed the petroleum coke (petcoke) more efficiently in a silicon production process. To decrease the raw materials consumption and the energy loss in an industrial silicon production process, the petcoke/coal ratios for the 8 MVA and 12.5 MVA furnaces should be 1.25∼1.4 and 0.4∼0.6, respectively, for the production of one ton of silicon.

The Effect of K-feldspar and Silica as Fluxing Agent on the Production Process of Phosphorus Furnace

Reducing energy and sustainable using of natural mineral resources offer challenges in energy production and environment. In this study, an efficient methodology is proposed for using K-feldspar as fluxing agent instead of silica in phosphorus furnace. Thermodynamic analysis of the process indicated the decomposition temperature of phosphate could be reduced by as much as 103 ∘C using K-feldspar. A series of experiments were conducted at the same acidity of 0.8. At the same potassium gasification rate of 96%, the high temperature melting results showed operating temperature of the silica system was 1300 ∘C while K-feldspar system operated at 1200 ∘C When phosphorus conversion rate was close, the residual flow temperature of the K-feldspar system was 180 ∘C lower than the silica. This was due to the residual quantity and different fluxing agents. The viscosity results indicated the spread out areas were similar at 1253 ∘C for K-feldspar while at 1432 ∘C for silica. This illustrated operating temperature was reduced about 180 ∘C and potash fertilizer was produced using K-feldspar in phosphorus furnace. The significance of this result will mean improved energy and cost savings for this process.

CO2 Gasification of Catalysts-Loaded Petroleum Coke at Different Grinding Medium

The gasification reactivity of PC (petroleum coke), strengthened by addition of different potassium carbonate proportions using different grinding medium, was investigated by using thermogravimetric analysis (TGA). Results showed that the gasification reactivity of PC not only increased with the increase of catalyst-loaded, but also showed the effective improvement by anhydrous alcohol. The PC was mixed with potassium carbonate [K2CO3] catalyst at 0.5%, 0.8%, 1.0% and 1.5%, and then ground wet with distilled water. The CO2-gasification rate of PC was only 77.35%, 80.55%, 84.07% and 85.88% under the gasification temperature 1100 °C and holding time 120 min, at different K2CO3 respectively. However, when the PC was ground in anhydrous alcohol at the same condition of catalyst-loading, the gasification rate of PC reached 95.43%, 96.63%, 95.50% and 95.61% at the holding time of 108 min, 101 min, 74 min and 35 min, respectively. It was shown by FTIR, SEM and EDX determinations that the anhydrous alcohol used as the grinding medium can further improve the gasification reactivity of PC when compared with the distilled water.