Techno-Economic Assessment of Biomass based Cogeneration Potential in KTDA managed tea factories

Abstract

Kenya is a leading country in the production and trade of black CTC tea in the world. Every year the country produces in excess of 300 million kilograms of made tea with KTDA accounting for about 60% of this. But this production calls for huge supply of both thermal and electrical power to the tea factories to meet their process heat and electrical power demands. About 15% of total energy required in tea production is electrical while thermal accounts for 85%. Electrical power demand is mate primarily from the national grid while process heat is mate through own steam generation from combustion of biomass based fuels such as wood fuel, briquettes and also combustion of fuel oil in oil burning boilers/heaters. Operation of tea factories especially withering and drying, means there is always a constant demand for electrical and thermal energies in 1:6 ratio. This concurrent energy demand, mean that tea factories can install technically and economically feasible biomass based cogeneration units that expand steam through double stage turbine systems. The expansion of the steam results in quantifiable electrical power generation, while extraction of steam at lower pressures provides process steam for drying and withering process. Successful operation of Finlay’s Saosa tea factory woodchip cogeneration plant in Kericho since 2009 shows that biomass cogeneration is a viable and feasible option for KTDA tea factories. Based on their current feedstock (biomass) consumption levels, the 58 KTDA tea factories have the potential to generate more than 30 MW electrical power and more than 264 MW of thermal power. Technologies like Combined Heat and Power systems (cogeneration) help in improving fuel use efficiency at the same time helping tea factories achieve their pollution control. This paper presents a discussion on energy utilization in the tea factories, quantifies the cogeneration potential that is available in the tea factories based on current energy utilization and goes ahead to present possible lifetime cost of power generated.