Techno-economic study of the application of cogeneration to a cement plant
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Gas turbines have the advantage of low operating costs and high reliability. In addition to producing electricity, the high-quality waste heat flow coming out of the turbine can be used in other processes, making the gas turbine a perfect system for combined heat and power (CHP). In this paper, the implementation of a gas turbine for CHP in a cement plant was studied.
AbstractThe production of clinker, the basic component of cement, requires about 3700 kJ/kgcl of thermal energy and 411 kJ/kgcl of electricity. Each year, a plant with a production capacity of 3.3 Mta needs about 47 MWe and 428 MWth. Because cement plants operate with a nearly closed air circuit, turbine exhaust air cannot be injected directly into the system to reduce heat consumption. The only source that has been identified in this study for heat recovery is the preheating of primary air. This preheating, done with turbine exhaust gas, would save up to 3 MW of fuel per year for a plant with a capacity of 3.3 Mta. Under conditions where electricity prices are high enough and gas prices are low enough, this configuration is profitable and would save up to several million per year.
ConclusionsThe aim of this study was to test whether cogeneration with a gas turbine could be implemented in the cement industry. Assuming that the primary air can be effectively preheated, this was conisdered as the entry point for the recovery energy obtained from the hot gases discharged from the gas turbine.
The results show that with a 10000 TPD furnace line, 2.4 MW of fuel input can be saved by increasing the primary air temperature from 50°C to 335°C.
The main disadvantage is that since everything put to use at the gas turbine exhaust is not used, the overall heat consumption of the plant increases, as does local CO2 production. But if you look at the national level, for some countries, thanks to the specific energy mix, overall emissions could also be reduced.