Characteristics of spent coffee ground as a fuel and combustion test in a small boiler (6.5 kW)

Spent Coffee Grotind is a residue of coffee drink mainly used at a coffee shop. Spent coffee ground is used as an odor removal, manure in flowerpot and so on. However most of spent coffee ground is discarded as garbage. In this study, we investigated characteristics of spent coffee ground as a fuel and combustion characteristics in a small boiler system (6.5 kW based on input lower heating value), such as CO, NOR, O-2 and heating characteristic of heating boiler. Drying of spent coffee ground in the open air condition takes less than 6 days in case of height of 11 mm. More than 96% of spend coffee ground is between 100 and 500 gm in particle size. Lower heating value of spent coffee ground used as fuel is about 18.8 MJ/kg (4500 kcal/kg at water content 10%). Combustion chamber of the boiler is a crucible type with primary and secondary air supply and heat exchanger is one through type. Spent coffee ground consumption as a fuel of the boiler is about 1.17 kg/hr. O-2 concentration of the flue gas of the boiler is about 17.8% which is higher than a commercial domestic gas boiler or a domestic wood pellet boiler. CO and NOx concentration are 643 and 163 ppm respectively. (C) 2017 Elsevier Ltd. All rights reserved.