Use of copper metal balls as internal heat distributor in fixed-bed pyrolyzer of spent coffee ground for biochar production

Narongporn Pungwiwat; Thoranis Deethayat; Nuapon Duongbia; Wassana Kamopas; Tanongkiat Kiatsiriroat

Use of copper metal balls as internal heat distributor in fixed-bed pyrolyzer of spent coffee ground for biochar production

Agriculture and Natural Resources -- formerly Kasetsart Journal (Natural Science), Volume 057, Issue 4, July 2023- August 2023, Pages 579-586

ISSN: 2452-316X(0075-5192)

DOI: doi.org/10.34044/j.anres.2023.57.4.03

Narongporn Pungwiwat^a, Thoranis Deethayat^b,*, Nuapon Duongbia^b, Wassana Kamopas^c, Tanongkiat Kiatsiriroat^b

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^aEnergy Engineering Program, Faculty of Engineering and Graduate School, Chiang Mai University, Chiang Mai 50200, Thailand

^bThermal System Research Laboratory, Department of Mechanical Engineering, Faculty of Engineering, Chiang Mai University, Chiang Mai 50200, Thailand. Research Group for Renewable Energy, Faculty of Engineering, Chiang Mai University, Chiang Mai 50200, Thailand.

^cScience and Technology Research Institute, Chiang Mai University, Chiang Mai 50200, Thailand. Research Group for Renewable Energy, Faculty of Engineering, Chiang Mai University, Chiang Mai 50200, Thailand

^*Corresponding author, e-mail: thoranisdee@gmail.com

Abstract

Importance of the work: Small copper balls were used as internal heat distributor in cylindrical pyrolysis bed of spent coffee ground (SCG) for biochar production. Objectives: To investigate the temperatures of the SCG during pyrolysis including the biochar properties of the SCG beds with and without copper balls. Materials & Methods: 300 g of SCG was pyrolyzed at 500°C under nitrogen atmosphere for 2 hours. Temperature changes and biochar properties at around the axes of the beds with and without metal balls those were the last positions to decompose were investigated. Two placements of metal balls, as layers in the SCG bed and mixing of metal balls with the same weight throughout the bed, were considered. Results: With two layers of 8 mm metal balls in the SCG bed, the temperature rate at around the bed center during decomposition of 200-450°C was 21.32% increase from that without the metal balls. The improvement was better than that of 4 mm metal balls of which the temperature rate was 9.64% increase from the normal bed. For the metal balls mixing throughout the bed, the opposite results were taken due to the high total heat capacity of the metal balls and SCG bed. The biochar properties from the first case were investigated and compared with those from the normal bed. With metal balls, the product properties were similar to those without metal balls except the porosity and CEC which are higher significantly. The biochar was suitable for soil amendment especially the acidic soil. Main finding: Placement of 8 mm copper ball layers could be undertaken as internal heat distributor in SCG bed. The temperature around the bed axis could come closer to that around the heating surface then the decomposition rate was faster which resulted in higher values of porosity, pH and CEC which the main parameters for the soil amendment.

Keywords

Biochar, Copper metal balls, Heat distribution, Slow pyrolysis, Spent coffee ground

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Use of copper metal balls as internal heat distributor in fixed-bed pyrolyzer of spent coffee ground for biochar production

Abstract

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