Wisitsree Wiyaratn

Using a membrane reactor for the oxidative coupling of methane: simulation and optimization

An oxidative coupling of methane (OCM) is a promising process to convert methane into ethylene and ethane; however, it suffers from the relatively low selectivity and yield of ethylene at high methane conversion. In this study, a membrane reactor is applied to the OCM process in order to prevent the deep oxidation of a desirable ethylene product. The mathematical model of OCM process based on mass and energy balances coupled with detailed OCM kinetic model is employed to examine the performance of OCM membrane reactor in terms of CH4 conversion, C2 selectivity, and C2 yield. The influences of key operating parameters (i.e., temperature, methane-to-oxygen feed ratio, and methane flow rate) on the OCM reactor performance are further analyzed. The simulation results indicate that the OCM membrane reactor operated at higher operating temperature and lower methane-to-oxygen feed ratio can improve C2 production. An optimization of the OCM membrane reactor using a surface response methodology is proposed in this work to determine its optimal operating conditions. The central composite design is used to study the interaction of process variables (i.e., temperature, methane-to-oxygen feed ratio, and methane flow rate) and to find the optimum process operation to maximize the C2 products yield.

Voltammetric detection of organohalides by redox catalysis: improved sensitivity by immobilisation within a cubic phase liquid crystal

Two combined strategies are reported for improving the sensitivity of organohalide detection by redox catalysis. These are, improvement of the second order rate constant (k) for catalytic reduction of the organohalide, and improvement of the rate of substrate diffusion. Values of k are calculated for both alkyl and aryl halides, from slow scan rate cyclic voltammograms in homogeneous solution. It is shown that a Zn(ii) porphyrin exhibits higher catalytic rates than the previously used Co(ii) porphyrin or Co(i) salen. Amperometric and rotating disk electrode studies of electropolymerised films of the Zn(ii) porphyrin, reveal that at optimum thickness, mediator-substrate reaction and substrate diffusion are the rate limiting steps. Hence, immobilisation of the Zn(ii) porphyrin within the more open structure of a cubic phase liquid crystal produces an increase in sensitivity of approx. 10 times, and lowers the limit of detection by one order of magnitude. The optimised sensor responds linearly to seven organohalides in the range 0.1 microM to 1.0 microM with a sensitivity of 6.95 A M(-1) cm(-2). Chronoamperometric experiments with a microdisk electrode show that the rate of charge transport in the cubic phase films (apparent diffusion coefficient, D(E)= 5.65 x 10(-10)+/- 0.11 x 10(-10) cm(2) s(-1)) is faster than in the electropolymerised films (D(E)= 3.64 x 10(-11)+/- 0.02 x 10(-11) cm(2) s(-1)). The variation of D(E) with the concentration of Zn(ii) in the cubic phase suggests that diffusion of charge is predominantly by electron self-exchange, rather than by physical movement.

Systematic Layout Planning to Assist Plant Layout: Case Study Pulley Factory

In this study, the application of a systematic plant layout planning (SLP) to assist the optimum design of process areas and locations is proposed. The number of machines and space requirement in pulley factory is determined. The operation process chart, flow of material and activity relationship chart have been investigated. The relationships between machines, operation sections and material flow are used to determine the suitable position of each activity. The SLP method has been employed to design the two alternative plant layouts and compare the performances between new layout and present layout in term of material flow. The new plant layout is modified by moving a disassembly and surface finish that significantly decrease the distance of material flow, so it is effective increasing production.

ENERGY EFFICIENCY EVALUATION FOR A “GREEN” POWER GENERATION PROCESS WITH MINIMUM EFFORT ON CARBON DIOXIDE CAPTURE AND STORAGE

This study evaluates the use of cracking for the removal of carbon from fuels to be used in a power generation process. Unlike conventional power generation systems, the proposed system includes a cracking unit, the function of which is to convert primary fuels into H2 rich syngas and solid carbon, thus avoiding the emission of CO2 and the need for carbon capture and storage (CCS) in the power generation system. Based on the thermodynamic analysis of equilibrium reactions in the cracker, it is demonstrated that the operating temperature has a significant influence on the carbon capture rate achieved and the composition of the syngas. Carbon in the fuel can be captured in solid form from hydrocarbon fuels when operating the cracker at sufficiently high temperatures; however, only a portion of carbon can be captured in a solid form from oxygenated hydrocarbon fuels, with the maximum carbon capture rate being achieved at an optimum temperature. An energy analysis, which takes into account the energy penalty of CCS for the conventional power generation system, reveals that the net available energy from the proposed system is still not as high as that of the conventional system with CCS; however, the solid carbon can be of high commercial value when appropriate technology is employed to convert the carbon byproduct into a high-added-value carbon product such as carbon black or carbon nanotubes (CNTs).

The Study of Extraction Beta-Carotene from Crude Palm Oil for Analysis Economic

The purpose of this project was determined the study of extraction β-carotene from crude palm oil with soxhlet extraction to analysis economic value. Evaluation of β-carotene extraction process was absorbed on resin adsorbents of styene divinyl benzene copolymer, by an addition of isopropanal solvent and hexane in soxhlet extraction process. The result shows that optimum condition for β-carotene adsorption time was 2 hours, soxhlet extraction time was 3 hours for 1 g resin, at 85 °C could extract 21.911% β-carotene by weight of carotene in crude palm oil. The resin could be reused for β-carotene at least 3 times.The extraction could extract 80% β-carotene by weight of carotene in crude palm oil. The process required a total investment of first year 2,059,627 bath, Net Present Value was 334,935.67 bath, benefit per cost was 2.04, the internal rate of return was 35.1% and the pay back period was 4 years. The result that was quite attractive for the cooperatives to invest and a design planning of machine in extraction process was a product layout.

Theoretical analysis ofa multi-stage membrane reactor for oxidative coupling of methane

Abstract Oxidative coupling of methane (OCM) is a promising route for the production of ethylene by fully utilizing the abundance of methane feedstock. In this study, a multistage dense tubular membrane reactor is investigated to improve the performance of OCM. Mathematical model of the membrane reactor based on conservative equations and detailed OCM kinetic model is employed to analyze the effect of key operating parameters such as temperature and methane to oxygen feed ratio, on the efficiency of the OCM process in terms of CH4 conversion, C2H4 selectivity and C2H4 yield. Adjustment of feed distributions at each membrane stage is also studied. The result shows that the multi-stage membrane reactor shows a better performance than the single-stage one. Moreover, a suitable feeding policy can improve the OCM performance.