Modeling and Optimization of Specific Energy Consumption and Green House Gas Emissions During Drying of Organic Blackberry with Different Pretreatments by Response Surface Methodology

The largest share of greenhouse gases in the world is related to the use of fossil fuels in power plants for electricity generate. Production and emissions of greenhouse gas are more important for the drying process that has high specific energy consumption (SEC). In this study, modeling and optimization of SEC and greenhouse gas emissions including CO2 and NOx during the process of blackberry drying under infrared-hot air combined dryer (at three inlet air temperature levels 50, 60 and 70 ° C) with different pretreatments including of microwave (90, 180 and 360 w), blanching (70, 80 and 90 ° C) and ultrasond (15, 30 and 45 min) were evaluated by response surface methodology. The drying energy was provided by various steam turbines, gas turbines and combined plants using natural gas, heavy oil and gas oil as fuel. The results showed that by increasing the microwave power and ultrosond time decreased quadraticly the amount of SEC (from 185.55 to 55.53 kWh/kg). However, this value decreased linearly (from 208.08 to 88.56 kWh/kg) with increasing blanching temperature. Emissions amount for all greenhouse gas decreased quadraticly (from 194460.67 to 24987.97g for CO2 and from 1074.36 to 106.06 g for NOx) with increasing microwave power, ultrosound time and hot air tepmerature for all turbines with different fuels. However, this amount decreased linearly with increasing blanching temperature (from 218063.85 to 39985.54g for CO2 and from 1204.76 to 169.72 g for NOx). Based on modeling using RSM, optimum conditions for the minimum SEC were determined to be microwave power of 349.7 W and inlet air temperature of 69.8 oC for microwave pretreatment, ultrasound time of 45 min and inlet air temperature of 70 oC for ultrasound pretreatment, blanching temperature of 90 oC and inlet air temperature of 70 oC for blanching pretreatment with disierability mean of 99.8%.