2. Materials and method The commercial die unit consists of a holder block wherein a taper die with a wearing ring and a split die are fitted. Diameter and length of punch are 60 and 360 mm, respectively. The material used for both, taper die and punch is high carbon high chromium steel. The complete briquetting machine consists of briquetting press, material handling equipment, hammer mill, hot air generator and dryer. To produce 35-mm-dia briquettes, a punch and die unit was designed and developed. Schematic diagram of the commercially available briquetting plant is shown in Fig. 1. Negotiations were initiated with some briquetting plant owners to replace the common 60- mm-dia unit with the smaller punch and die set so that sufficient quantity of 35-mm-dia briquettes could be produced for combustion and gasification trials. Finally, an agreement was made with M/s Vishal Briquettes of Nadiad for this purpose and the 35 mm size punch and die unit was retrofitted in the commercial briquetting machine.