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چکیده
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Today, global warming as a consequence of consuming fossil fuels has become a global concern. Fossil fuels used in power plants to generate power have the highest contribution to the emission of greenhouse gases (GHG) worldwide. Considering the large share of the agriculture sector in power consumption, the processing and drying industries account for the highest energy consumption in this sector. Formation and emission of GHG are associated with farm practices. These emissions are more important in the drying process because it is required large amounts of energy. This study examined GHG emissions (NOX, CO2 and SO2) during the drying of pistacia atlantica samples using 5 different types of dryers, namely hot air (HA), hybrid hot aireInfrared (HAeIR), hybrid hot airemicrowave (HAeMW), continuous multistage (CMS) conveyor dryer, and hybrid collector-equipped hot air - solar (HAeSolar) dryers. Different types of turbines (steam, gas, and combined) running on natural gas, heavy oil and gasoil were used to supply their energy requirements. Results indicated that the highest (340.97 kWh/kg) and lowest (6.01 kWh/kg) specific energy consumption (SEC) occurred in CMS and HAeMW dryers, respectively. In general, the highest NOx, CO2 and SO2 emissions were 357336.6, 1974.21 and 5210.02 g, respectively, in the continuous dryer at 40 C using an air velocity of 1.5 m/s and a conveyor speed of 10.5 mm/s for one kg of dried crop. The lowest NOx, CO2 and SO2 emissions were also 2704.5, 11.47 and 0 g, respectively, in the HAeMW dryer at 70 C using an air velocity of 0.5 m/s exposed to 630 W of microwave power for one kg of dried crop. The experimental results showed that GHG emissions for all dryers were reduced with the increase in the air temperature and reduction in the inlet air velocity. In the IR, MWand CMS, GHG emissions were lower at an increased IR power, increased MWpower, and low conveyor speed, respectively.
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