Optimization for the production of ammonia from urea in a semi-batch reactor for safe feedstock in power plants: Experimental and statistical studies

Urea hydrolysis for production of ammonia, in different application areas require safe use of ammonia, for removal of the NO(x) contaminates contained in a flue gas stream and increase in the efficiency of an electrostatic precipitator for the removal of fly ash from the flue gas stream. The single and combined effects of operating parameters such as initial feed concentrations, temperatures, reaction times, and stirring speeds on the production of ammonia from urea were analyzed using response surface methodology (RSM). Analysis of variance (ANOVA) showed a high coefficient of determination value (R(2) = 0.967) and satisfactory prediction second order regression model was derived. The optimum production conditions determined for semi-batch reactor were temperature 178 degrees C, initial feed concentration 22.24 wt% of urea, time of reaction 43.2 min and stirring speed 1045 rpm. At optimum conversion conditions, the conversion of urea for production of ammonia was found to be >= 13%

Statistical modelling and optimization of hydrolysis of urea to generate ammonia for flue gas conditioning

The present study is concerned with the technique of producing a relatively small quantity of ammonia which can be used safely in a coal-fired thermal power plant to improve the efficiency of electrostatic precipitator by removing the suspended particulate material mostly fly ash, from the flue gas. In this work hydrolysis of urea has been conducted in a batch reactor at atmospheric pressure to study the different reaction variables such as reaction temperature, initial concentration and stirring speed on the conversion by using design expert software. A 2(3) full factorial central composite design (CCD) has been employed and a quadratic model equation has been developed. The study reveals that conversion increases exponentially with an increase in temperature, stirring speed and feed concentration. However the stirring speed has the greatest effect on the conversion with concentration and temperature exerting least and moderate effect respectively. The values of equilibrium conversion obtained through the developed models are found to agree well with their corresponding experimental counterparts with a satisfactory correlation coefficient of 93%. The developed quadratic model was optimized using quadratic programming to maximize conversion of urea within experimental range studied. The optimum production condition has been found to be at the temperature of 130 degrees C, feed concentration of 4.16 mol/l and stirring speed of 400 rpm and the corresponding conversion, 63.242%. (C) 2010 Elsevier B.V. All rights reserved

Kinetic studies on hydrolysis of urea in a semi-batch reactor at atmospheric pressure for safe use of ammonia in a power plant for flue gas conditioning

With growing industrialization in power sector, air is being polluted with a host of substances-most conspicuously with suspended particulate matter emanating from coal-fired thermal power plants. Flue gas conditioning, especially in such power plants, requires in situ generation of ammonia. In the present paper, experiments for kinetic study of hydrolysis of urea have been conducted using a borosil glass reactor, first without stirring followed by with stirring. The Study reveals that conversion increases exponentially with an increase in temperature and feed concentration. Furthermore. the effect of stirring speed, temperature and concentration on conversion has been studied. Using collision theory. temperature dependency of forward rate constant has been developed from which activation energy of the reaction and the frequency factors have been calculated. It has been observed that the forward rate constant increases with an increase in temperature. The activation energy and frequency factor with stirring has been found to be 59.85 kJ/mol and 3.9 x 10(6) min(-1) respectively with correlation co-efficient and standard deviation being 0.98% and +/- 0.1% in that order. (C) 2009 Elsevier B.V. All rights reserved

Optimization of ammonia production from urea in continuous process using ASPEN Plus and computational fluid dynamics study of the reactor used for hydrolysis process

The present study addresses the methods and means to safely produce relatively small amounts (i.e., up to 50 kg/h) of ammonia. The optimization and simulation study conducted for continuous process and effect of operation conditions like reaction temperature, initial feed concentration and pressure on ammonia production carried out using ASPEN Plus. Also, a computational fluid dynamics (CFD) model was proposed to simulate the hydrolysis of urea for synthesis of ammonia. A series of parametric studies to investigate flow rates, thermal boundary conditions and reactor geometry was performed for hydrolysis of urea and the optimized operating conditions and reactor geometry were obtained. Detailed three-dimensional flow, heat and chemistry simulations of ammonia, carbon dioxide and ammonium carbamate. The study demonstrates that simulation is a useful tool for diagnosing hydrolysis reactor mixing pathologies and for identifying practical countermeasures that could improve process performance. (C) 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved