Improved Analytical Approach for Fuel Demand Re-Evaluation in Liquid and Gaseous Waste Thermal Processing Units

presentation, poster

en

The operation of many processes in the chemical and process industries is associated with the production of liquid and gaseous wastes containing harmful substances that cannot be discharged into the environment and must first be treated. For this purpose, Waste Thermal Processing Units (or WTPUs) are often applied to thermal treatement of the pollutants contained in the treated waste. The heart of WTPU is an incinerator where liquid or gaseous waste is injected and harmful pollutants are thermally decomposed there under high temperatures ranging between 500-1100 °C. Externally supplied fuel is burned in the furnace to maintain prescribed temperatures. The thermal treatment of the waste and the combustion of the fuel subsequently produce flue gases which can be used then for energy purposes, for example to generate heating steam. This is a reliable process, but its operation involves considerable operating costs in the form of high external fuel demand to maintain the prescribed temperatures inside the incinerator. However, the energy demand of WTPU can be significantly reduced by appropriate utilization of the heat contained in the flue gas for technological purposes such as preheating the gaseous waste before its injection into the incinerator. In the case of liquid waste, a steam-heated evaporator can be applied to reduce the liquid fraction of the waste. However, the evaluation of the external fuel savings in relation to the thermal pre-treatment of the waste depends on a number of parameters and leads to the solution of complex non-linear heat and mass balances of WTPU, which are then dealt with by expert institutions owning commercial software, which is associated with high financial costs for the elaboration of particular studies. This discourages potential investors, and existing WTPUs continue to operate inefficiently. In this conference paper, a very accurate and easily applicable analytical approach is presented to determine the achievable fuel savings depending on the above mentioned heat utilization of the produced flue gas. The accuracy of the developed mathematical relationships is subsequently verified on case studies of WTPUs treating gaseous and liquid wastes, where the deviation between the calculated fuel savings using the developed method and the results of non-linear simulations was less than 0.5% in all cases.

The operation of many processes in the chemical and process industries is associated with the production of liquid and gaseous wastes containing harmful substances that cannot be discharged into the environment and must first be treated. For this purpose, Waste Thermal Processing Units (or WTPUs) are often applied to thermal treatement of the pollutants contained in the treated waste. The heart of WTPU is an incinerator where liquid or gaseous waste is injected and harmful pollutants are thermally decomposed there under high temperatures ranging between 500-1100 °C. Externally supplied fuel is burned in the furnace to maintain prescribed temperatures. The thermal treatment of the waste and the combustion of the fuel subsequently produce flue gases which can be used then for energy purposes, for example to generate heating steam. This is a reliable process, but its operation involves considerable operating costs in the form of high external fuel demand to maintain the prescribed temperatures inside the incinerator. However, the energy demand of WTPU can be significantly reduced by appropriate utilization of the heat contained in the flue gas for technological purposes such as preheating the gaseous waste before its injection into the incinerator. In the case of liquid waste, a steam-heated evaporator can be applied to reduce the liquid fraction of the waste. However, the evaluation of the external fuel savings in relation to the thermal pre-treatment of the waste depends on a number of parameters and leads to the solution of complex non-linear heat and mass balances of WTPU, which are then dealt with by expert institutions owning commercial software, which is associated with high financial costs for the elaboration of particular studies. This discourages potential investors, and existing WTPUs continue to operate inefficiently. In this conference paper, a very accurate and easily applicable analytical approach is presented to determine the achievable fuel savings depending on the above mentioned heat utilization of the produced flue gas. The accuracy of the developed mathematical relationships is subsequently verified on case studies of WTPUs treating gaseous and liquid wastes, where the deviation between the calculated fuel savings using the developed method and the results of non-linear simulations was less than 0.5% in all cases.

Liquid waste processing unit;gaseous waste processing unit;fuel saving calculation;waste thermal decomposition;analytical approach

05.10.2021

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