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Gas Ratio (gas + ratio)
Selected AbstractsMulti-objective optimization of venturi scrubbers using a three-dimensional model for collection efficiency,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2-3 2003Gopalan Ravi Abstract Multi-objective optimization of a venturi scrubber was carried out using a three-dimensional model for collection efficiency and non-dominated sorting genetic algorithm (NSGA). Two objective functions, namely (a) maximization of the overall collection efficiency, and (b) minimization of the pressure drop were used in this study. Three decision variables including two operating parameters, viz liquid,gas ratio and gas velocity in the throat, and the nozzle configuration, which takes into account the three-dimensional nature of the problem, were used in the optimization. Optimal design curves (non-dominated Pareto sets) and the values of the decision variables corresponding to optimum conditions on the Pareto set for a pilot-scale scrubber were obtained. The liquid to gas (L/G) ratio, which is a key decision variable that determines the uniformity of liquid distribution, and a staggered nozzle configuration can produce uniform liquid distribution in the scrubber. Multiple penetration using nozzles of two different sizes in a triangular staggered arrangement can reduce liquid loading by as much as 50%, consequently reducing the pressure drop in the scrubber. © 2003 Society of Chemical Industry [source] Plasmas for texturing, cleaning, and deposition: towards a one pump down process for heterojunction solar cellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Mario Moreno Abstract Low temperature plasma deposition of a-Si:H thin films has emerged as a promising alternative for high efficiency hetero junction (HJ) solar cells. In this work we study plasma processes for texturing and cleaning c-Si wafers pursuing a low cost dry fabrication process of HJ solar cells. We have studied two independent plasma processes: i) Texturing of c-Si wafers using SF6 - O2 plasmas in a RIE system, in order to reduce the surface reflectance and therefore improve the light trapping. The effects of the RF power and gas ratio on the c-Si surface texture have been studied in detail. Highly textured surfaces, with very low reflectance values (around 6% in the range of 300 , 1000 nm) have been achieved. ii) Etching of the native oxide and passivation of the c-Si surface by plasma, in a standard RF PECVD system. We used SiF4 plasma with optimized conditions for an efficient native oxide removal, and without breaking the vacuum, 40 nm of a-Si:H were deposited in order to passivate the c-Si surface. High effective lifetime values were obtained (,eff , 1.5 ms), providing high implicit open circuit voltages (Voc , 0.713 V) and low surface recombination velocities (Seff < 9 cm s -1). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] GaN on Si substrates for LED and LD applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004Suzuka Nishimura Abstract GaN epitaxial layer has been grown on 2 inch diameter Si substrates by using highly conductive BP buffer crystal. It has been found that the 2-inch GaN on BP/Si wafers are remarkably flat after epitaxial process. BP layer has grown flat and continuously on a large size silicon wafer. GaN has been found to grow continuously on such a substrate.?BP crystals have been found to be highly conductive and controllable depending on the gas ratio. In addition, UV illumination enables us to study the chamber conditions such as contamination by impurity. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Formation and Distribution of Silver Nanoparticles in a Functional Plasma Polymer Matrix and Related Ag+ Release PropertiesPLASMA PROCESSES AND POLYMERS, Issue 7 2010Enrico Körner Abstract Plasma polymer coatings with embedded Ag nanoparticles were deposited in a low pressure RF plasma reactor using an asymmetrical setup with an Ag electrode. The plasma polymer was deposited from a reactive gas/monomer mixture of CO2/C2H4 yielding a functional hydrocarbon matrix. In addition, Ar was simultaneously used to sputter Ag atoms from the Ag electrode, forming nanoparticles within the growing polymer matrix. The influence of the power input, gas ratio and coating thickness on both, the Ag content and the Ag nanoparticle morphology, as well as the distribution in the polymer matrix were investigated. It was found that both increasing the power input and the CO2 ratio result in a higher incorporation of Ag into the matrix. [source] Different Hydrocarbon Accumulation Histories in the Kelasu-Yiqikelike Structural Belt of the Kuqa Foreland BasinACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010WANG Zhaoming Abstract: The Kuqa foreland basin is an important petroliferous basin where gas predominates. The Kela-2 large natural gas reservoir and the Yinan-2, Dabei-1, Tuzi and Dina-11 gas reservoirs have been discovered in the basin up to the present. Natural gases in the Kelasu district and the Yinan district are generated from different source rocks indicated by methane and ethane carbon isotopes. The former is derived from both Jurassic and Triassic source rocks, while the latter is mainly from the Jurassic. Based on its multistage evolution and superposition and the intense tectonic transformation in the basin, the hydrocarbon charging history can be divided into the early and middle Himalayan hydrocarbon accumulation and the late Himalayan redistribution and re-enrichment. The heavier carbon isotope composition and the high natural gas ratio of C1/C1,4 indicate that the accumulated natural gas in the early Himalayan stage is destroyed and the present trapped natural gas was charged mainly in the middle and late Himalayan stages. Comparison and contrast of the oils produced in the Kelasu and Yinan regions indicate the hydrocarbon charging histories in the above two regions are complex and should be characterized by multistage hydrocarbon migration and accumulation. [source] Thermodynamic Equilibrium Calculations for the Reforming of Coke Oven Gas with Gasification GasCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2007B. Li Abstract Thermodynamic analyses of the reforming of coke oven gas with gasification gas for syngas were investigated as a function of coke oven gas-to-gasification gas ratio (1,3), oxygen-to-methane ratio (0,1.56), pressure (25,35,bar) and temperature (700,1100,°C). Thermodynamic equilibrium results indicate that the operating temperature should be approximately 1100,°C and the oxygen-to-methane ratio should be approximately 0.39, where about 80,% CH4 and CO2 can be converted at 30,bar. Increasing the operating pressure shifts the equilibrium toward the reactants (CH4 and CO2); increasing the pressure from 25 to 35,bar decreases the conversion of CO2 from 73.7,% to 67.8,%. The conversion ratio of CO2 is less than that in the absence of O2. For a constant feed gas composition (7,% O2, 31,% gasification gas, and 62,% coke oven gas), a H2/CO ratio of about 2 occurs at temperatures of 950,°C and above. Pressure effects on the H2/CO ratio are negligible for temperatures greater than 750,°C. The steam produced has an effect on the hydrogen selectivity, but its mole fraction decreases with temperature; trace amounts of other secondary products are observed. [source] Absorber intercooling in CO2 absorption by piperazine-promoted potassium carbonateAICHE JOURNAL, Issue 4 2010Jorge M. Plaza Abstract Intercooling was evaluated as a process option in CO2 absorption by piperazine (PZ) promoted potassium carbonate. The system performance with 4.5 m K+/4.5 m PZ was simulated by a model in Aspen Plus® RateSepÔ. The absorber was evaluated for use with a double matrix stripper by optimizing the position of the semilean feed and intercooling stages to maximize CO2 removal. Additionally, a simple absorber system was modeled to observe the effect of intercooling on systems with variable CO2 lean loading. Intercooling increases CO2 removal by as much as 10% with the double matrix configuration. With a simple absorber, the effectiveness of intercooling depends on solvent rate. Near a critical liquid/gas ratio (L/G) there is a large improvement with intercooling. This is related to the position of the temperature bulge. An approximation is proposed to estimate the critical L/G where intercooling may maximize removal. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] | ||||||||||