Integrated Unit for Thermal Processing of Polluted Gases - Alternative Arrangement

conference paper

English

Clean air and environment have become priorities at present. It is vitally important to find concrete ways for solving problems connected with environmental protection. This paper shows an efficient and cost effective way for thermal processing of gas wastes incineration of volatile organic compounds and carbon monoxide contained in polluted air. Quite new unique equipment for this purpose has been developed. This unit can be used in various branches of industry (for the treatment of polluted air from paint shops, chemical cleaning systems, degreasing processes, printing machines, gas wastes from various chemical processes, for the thermal treatment of offgases originating in refineries, in production of plastics, pharmaceutical industry, food industry, laboratories etc.). The equipment is characterized by a cylindrical combustion chamber which is placed inside a heat exchanger polluted air preheater. The integration of combustion chamber and air preheater into a highly compact equipment has several advantages. This fully integrated incineration unit has relatively small dimensions owing to its compactness, heat losses from combustion chamber are utilized for preheating polluted air, and fuel (natural gas) flowrate is minimized as well as heat losses to the ambient air. In some cases an autothermal process can occur depending on type and concentration of pollutants. Then the burner (which is placed at the top of combustion chamber) takes only a stabilizing function. It can be said that both investment and operating costs are minimized and this equipment for the thermal treatment of volatile organic compounds and carbon monoxide can easily be placed within industrial units. A mathematical model for the calculation and/or simulation of this equipment has been developed. This model is based on an integration of models of the heat exchanger and the combustion chamber. Basic process parameters were obtained by heat and mass balance calculations using a software system for simulating processes for thermal treatment and/or incineration of wastes. An experimental facility was designed and built as that for a real industrial scale operation (with a capacity of 600 mN3/hr of polluted air). Based on a systematic set of measured data it is possible to verify the relations for thermal and hydraulic calculations, to make necessary correlations of these relations (especially those for the evaluation of heat transfer coefficients and friction factors in the model of the heat exchanger). The acquired data enable also to make a validation of simulation using CFD (Computational Fluid Dynamics). If an excessive concentration of pollutantscombustibles is processed energy of outlet flue gas can be utilized not only for air preheating but also for steam generation or other purposes. Then we can speak about a wastetoenergy system. After testing the above newly developed unit it can be said that this equipment can bring a benefit in a wide scope of applications. (It can also be used in processes where other polluted fluids are treated as e.g. in case of a unit for drying and cleaning natural gas one of first industrial applications.) Several options of arrangement exist according to a specific purpose and requirements (highly compact arrangement, "over pressure", "under pressure", equipment with catalytic bed). It has been shown that a relatively small unit for thermal processing of gas wastes can contribute to maintaining clean environment. However, the experimental facility is also used for teaching purposes and research in various disciplines of process/chemical engineering (like e.g. process heat transfer, process control, modeling, simulation).

polluted gas, incineration, simulation, modelling, thermal treatment,

ŠTULÍŘ, R.; ORAL, J.; BÉBAR, L.; STEHLÍK, P.; TRUNDA, P.

1. 1. 2001

IChemE - Institution of chemical engineers

IChemE, davis Building, 165-189 Railway Terrace, Rugby CV21 3HQ, UK

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