CAMOUFLAGED REALITIES AND FACTS IN A SMOKE HOUSE FOR DRYING RSS

Abstrak

More than ninety percent of the latex produced in India is converted into ribbed smoked sheets (RSS) which is the oldest method of processing, widely adopted by rubber growers due to its simplicity and  minimal cost of processing. The country has established over 500 group processing centers under rubber producer’s society with an aim of producing quality rubber sheets. Sheet rubber processing involves various stages viz. sieving, bulking, standardization, coagulation of latex, sheeting, dripping and drying in a smoke house. Firewood is used as fuel in the biomass furnace attached to the smoke house, which is a traditional practice of drying in the rubber processing industry. Bioenergy generated during the treatment of latex processing effluent is also used in smoke houses as alternative energy. In order to monitor the energy efficiency in a conventional smoke house, heat balance and pollution level were studied. The smoke house (5.46 x 3.35 x 4.64 m) temperature at different points was monitored for heat loss assessment and heat distribution pattern in upper, middle and lower convective zones. The temperature was found to vary between 43 to 63^oC during the entire smoke drying process. It was observed that drying RSS of 750 kg per batch in the smoke house consumed 3550 MJ for the required moisture content of 0.5 % within 70 h (4 days) during non-rainy hours. Out of the total heat energy supplied, only 858.5 MJ (24.2 %) of the input heat was utilized and the rest was lost in stored energy, 420 MJ (12%) walls and door loss, 881 MJ (25.1%) exhaust loss, 1240 MJ (34.5%) moisture in fuel, 106.5 MJ (3.0%) and the rest 42.6 MJ (1.2%) being unaccountable. Isothermal contour was drawn for the temperature distribution inside the smoke house at different altitude points. Higher temperature was maintained at the upper convective zone, which led to maximum heat loss through chimneys. Average daily biogas generated was 10 cum from 5000 liters of effluent processed and the biogas fuel was retrofitted in the smoke furnace for an average of 4 hours as heat supplement (703 MJ). Firewood reduction of 26 kg (19.8%) was achieved with alternate biogas fuel for the drying process. The composition of exhaust gas emission was found to be CO₂ (5.5 %), CO(8.5 %), O₂ (14 %) and SOx and NOx (<1 %), the greenhouse gases leading to global warming. Altering air supply and providing proper insulation in the smoke house are recommended for considerable reduction of heat loss and greenhouse gases. Switching over to cleaner, renewable energy sources for drying RSS is also recommended for environmental sustainability in rubber processing industries.

Keywords: biogas, emission, heat balance, RSS, rubber processing, smoke house, temperature