Abstract
A large amount of heat energy is required for paddy drying processes to evaporate water from paddy grains. Currently, fossil fuels are being used as an energy source to heat air during the drying process. However, fossil fuels cause air pollution, climate change, and disruption of ecological balance. In this study, to reduce the dependence on fossil fuels for paddy drying, a pilot-scale biomass-assisted recirculating mixed-flow drying system (PSBA-RMFD) for drying paddy was designed, installed, and tested. In this PSBA-RMFD, the heat energy required for heating the drying air was provided only by biomass. The PSBA-RMFD comprises a biomass furnace, drying column, vibratory feeder, bucket elevator, and blower. This study is aimed at evaluating the performance of the PSBA-RMFD with a drying capacity of 400 kg/h. The performance metrics of the PSBA-RMFD were specific energy consumption (SEC), specific thermal energy consumption (STEC), specific moisture evaporation rate (SMER), thermal efficiency of the PSBA-RMFD, exergy efficiency of the drying section, and improvement potential of the dryer. From the experiments conducted in this study, the values of the aforementioned performance parameters were as follows: 0.806-8.656 kW h/kg of water evaporated; 0.385-4.136 kW h/kg of water evaporated; 0.122-1.308 kg of water evaporated/kW h; 7.82-83.99%; 15.28-25.64%; and 858.90-1355.62 W, respectively. The paddy moisture content was reduced from 20.90% wet basis (initial weight of 400 kg) to 13.30% wet basis (final weight of 364 kg) in 270 min, with an average temperature of 78.15°C and average relative humidity of 8.55%. The percentage of biomass energy used in the drying system was approximately 47.77% of the overall energy. In addition, the payback period of the PSBA-RMFD was 1.9 years.
Highlights
Indonesia is an agricultural economy-based country with a vast agricultural land and is one of the world’s leading paddy producers
The specific moisture evaporation rate (SMER) was in the range of 0.122–1.308 kg/kW h, with an average of 0.562 kg/kW h
The results showed that the PSBA-RMFD reduced the paddy moisture content from 20.90% to 13.30% in 270 min, with an average temperature of 78.15°C and average relative humidity of 8.55%
Summary
Indonesia is an agricultural economy-based country with a vast agricultural land and is one of the world’s leading paddy producers. Its paddy production in 2019 reached approximately 84 million t. Indonesia is one of the world’s largest paddy consumers, with an annual per capita consumption of approximately 111.58 kg [1]. The harvested paddy contains a high degree of moisture, ranging from 20% to 27% (wet basis). To secure a long shelf life, the paddy is typically dried to a moisture content of 14% (wet basis) [2]. Drying with open sunlight has several advantages, including free and abundant supply of energy from the sun, simplicity of the method, and low initial and maintenance costs; its disadvantages include, the requirement of a large area, which is a function of the solar radiation, long drying times, lowered quality of the dried products, and significant loss of paddy during the drying process
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