Optimization of Ceramic Insulation of Cooking Stoves Using Carbonized Organic Waste

Abstract

Many households and small hotels in Kenya source their energy from biomass; mainly wood and charcoal. For the urban poor, their energy source is basically charcoal. With increasing population, rural urban migration, tough economic times, the use of charcoal must be as efficient as possible. In cognizance of this need, development of energy efficient biomass (charcoal) cook stoves is paramount. The cook stoves with high efficiency will ensure that during cooking, most of the energy from the fuel goes to the cooking pan and heat losses are minimized. The main objective of the project was to optimize the insulating properties of ceramic insulation used in ceramic cook stoves using carbonized organic waste as the burnout additive. Carbonized organic waste herein referred to as char was collected and ground to fine dust. The char was used as a burnout medium in the clay to create pores, reduce density and increase porosity thereby improving insulation properties of the fired clay. Optimization was achieved by using different ratios of clay to char. Testing of biomass cook stove is provided for in ISO- 19867-0; the harmonized laboratory test protocol. Described in part 1 of the protocol is the standard test sequence for determination of emissions, performance, safety and durability. Adopted in this project were 410g of charcoal, 5 kg of water and a duration of 30min. The quantity of fuel used, rise in water temperature and amount water evaporated were measured. The real time emissions of Carbon monoxide (CO) and fine inhalable particles of up to 2.5 micrometers diameters (PM2.5) were continuously monitored using sensors. The results showed that the apparent porosity of the sample increased from 34% with no char to 87% when the sample had 50% char. On the other hand, the bulk density reduced from 2.8 g/cm3 with no char to 1.2 g/m3 with 50% char. The prototype thermal efficiency was better at 33% compared to the 25.8%.for the control cook stove. The prototype and control cook stove cooking power were 0.97kW and 0.71kW respectively. Another important outcome of this study was to do with emissions. The prototype PM2.5 emissions estimated to be 76 mg/MJd and CO emissions at 21 g/MJd which were lower than the Kenya standard KS 1814:2019 maximum emission of 137 mg/MJd and 25 g/MJd respectively.

Fuel saving per month using the prototype for heating and cooking would be 112kgs of charcoal. This study has shown that when clay was mixed with char, there was a significant increase in desirable characteristics, which results in increased efficiency of biomass (charcoal) cook stoves and lower emissions.