SCAVENGING HEAT FROM INCINERATORS: CASE OF A MEDICAL WASTE INCINERATOR AT ZOMBA CENTRAL HOSPITAL, MALAWI.

Abstract

A medical waste incinerator is an application of combustion in a furnace for thermal treatment of wastes. Energy can be recovered from medical waste incinerators and utilized for other purposes as a means of energy conservation. The aim of this study was to recover heat generated in the medical waste incinerator at Zomba Central Hospital for possible reuse. This was achieved by measuring temperature distribution in the incinerator so as to determine optimum position for a heat exchanger, designing an optimum heat exchanger based on the temperature distribution and assessing the performance of the whole heat scavenging system. Highest and consistently higher temperatures (up to 500°C) were observed at the back of the incinerator compared to the front which reached 148°C. This was due to the insulation of the incinerator’s back surface. Hence the heat exchanger optimum position was found to be the back of the incinerator. Optimum flow rate of water through the heat exchanger was found to be 3.75 x 10-5m3/sec. At this flow rate, heat gained was 10.87 J/s or 39.132 kWh. The use of the heat-scavenging system would save the hospital about MK1590 (US$ 2.21) worth of electricity bill per every 810L of water heated per day and MK47670 (US$ 66.17) per month against an investment cost of MK80000 (US$ 112).