Many industrial processes result in tail gas wastes that must be flared or incinerated to abide with environmental guidelines. Tail gas incineration occurs in several chemical processes resulting in high-temperature exhaust gas that simply go to the stack, thus wasting all that valuable heat! This paper discusses useful heat recovery and electric power generation utilizing available heat in exhaust gas from tail gas incinerators. Tail gas, which is considered as the main fuel in this study, is typically “free” fuel. Eventhough with low heat content, when the heat is recovered and utilized properly, heat recovery of tail gas will result in significant savings to the plant. The thermodynamic and economic study presented here assumes that heat will be recovered in a wast-heat recovery boiler from the exhaust gas out of the incinerator and will produce enough superheated steam to generate 25 MW in a condensing steam turbine generator. Data for this study were provided by an operating chemical production facility in the southeastern region of the US. Energy analysis and a total project scope cost estimate were developed for this study. Actual costs were obtained for all major equipment. Different thermodynamic scenarios were considered to identify the optimum and most economical energy system design. The main goal of the study was to fulfill the plant’s power and steam requirements and sell the additional power to the local utility. An existing old steam boiler will be retired after the incorporation of the new cogeneration plant. Process steam will be supplied via a steam turbine extraction. The results indicate that the total capital cost of a ± 25% grade estimate for the supply and installation of the 25 MW cogeneration system, is estimated to be $51,000,000 in the fourth quarter of 2008 dollars with escalation through end of 2010, representing $2000/kW. Based on an internal power demand of 12 MW by the chemical plant, a balance of 13 MW is assumed be sold to the local utility. The cost of electricity used for this study was assumed to be 9 cents per kilowatt-hour for purchased power and 6 cents per kilowatt-hour for sold power. The annual plant savings in purchased power is estimated to be over $6,300,000 while the annual plant revenue from selling the remaining power is estimated to be in excess of $6,200,000. The cost analysis, when accounting for operation and maintenance, resulted in a pay back period of less than 4 years and an internal rate of return on investment of over 13 percent after 6 years.
Heat Recovery From Tail Gas Incineration to Generate Power
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Tawfik, TA, & Smith, TP. "Heat Recovery From Tail Gas Incineration to Generate Power." Proceedings of the ASME 2010 Power Conference. ASME 2010 Power Conference. Chicago, Illinois, USA. July 13–15, 2010. pp. 673-683. ASME. https://doi.org/10.1115/POWER2010-27273
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