CONVERSION OF Firewood operated Tea drier to LPG System             A. Description of the process :               PRODUCTS AND DRYING SYSTEM                   The thermal processes of manufacture of tea essentially consists of withering and drying. the average moisture content of green leaf tea varies from 70 - 80% depending on the location. A small part of this moisture is evaporated during withering and the balance during drying. A hot air generator fuelled by firewood is used for delivering the heat required. Since direct firing has to be avoided for fear of contamination of the product by smoke and chute, heat exchangers are provided for heat transfer to the blown air. It is same case with liquid fuels too. The axial flow type propeller fan is generally used in withering troughs for drying, as it has to deliver medium to low volume of air at higher pressures.     B. Limitation of the system :                 1.    The quality and valuation of made tea are influenced by length of drying time, inlet temperature, dryer temperature, air speed and thickness and spread of the wet product. Above all, maintenance of dryer temperature, and its control accuracy play a major role. For materials like tea, which shrink during drying, controlling of the rate of drying is very important, With firewood as fuel, it is difficult to achieve a close control accuracy which ultimately affects the quality of tea.                   2.    Even though basic rate of firewood is cheap, all factors like transportation costs, labour involved in loading, unloading, cutting the logs into small pieces and handling of as and storage space makes it costly                   3.    Wide variation in the quality of fire wood as the ******* ********** make it difficult to assess the correct quantity required to mainrain dryer temperature                   4.    Pilferage of firewood while under transportation or during storage, results in incorrect calculation of consumption figures.             C. What we did :               1. Conversion to LPG :         In the Electrical heating system working height can be fully utilized. But with the LPG burners it requires extra height at the top for combustion, so that the flame does not impinge on the jobs. Hence the working height of the furnace was increased by bringing down the bogie. the furnace was relined with bricks. The height of the door was also increased by welding extra plate at the bottom and additional insulation was provided.                 2. Operations :         The fire wood fired indirect hot air generator was removed and a direct fired hot air blower was bolted to the suction mouth of the hot air blower. An automatic LPG burner was mounted at the inlet portion of the hot air generator. LPG supply to the burner is sourced from a bullet kept in separate yard. The bullet erection, LPG facility and the licensing formalities were done by us. A control panel with automatic temperature controller and other accessories was installed.             D. Results :                 1.    Quality of made tea has improved and production increased after conversion to LPG system.-                   2.    There is reduction in man power and savings in labour costs.                   3.    Pollution is completely eliminated .                   4.    Working environment has become cleaner and worker friendly.                   5.    Down time reduced due to marginal maintenance.                  6.    Temperature control possible with a various of + or - Deg. C.