The usual binder is starch from any source, whichever is the cheapest of topioca,corn,maize or tamarind seed. It doesn't have to be an edible grade. Although other binders have been used such as china clay and molasses these do not produce as satisfactory a briquette as starch. Binders which produce an objectionable odour or smoke on burning are not acceptable for the domestic market. The binding agent also needs to be fairly resistant to fermentation and bacterial attack during storage to meet market fluctuations. All these considerations tend to favour starch as the best all-round binder.

The filler( if used) is selected on price - it has to cost less by weight than charcoal, be not abrasive to the machinery and free of objectionable odour on burning. Calcium carbonate/ bentonite in powder form fits the requirements. Sources are: ground limestone, chalk and ground shells.

The manufacturing process is as follows:

First the powder charcoal must be screened to reduce it to a uniform size and remove gross impurities. In case of lump, solid pieces are left out in screening, Hammer mills are used to again powder them. The screen analysis of the ground charcoal is the coarsest which will give a satisfactory briquette with minimum binder usage.

The ground & screened charcoal powder is next mixed with the binder and filler, (if used). If starch is the binder it must first be cooked (gelatinised) with hot water before adding to the mixer. A Muller type  mixer is normal and proper mixing is essential to reduce binder consumption to the minimum.

The mixture then passes to the briquetting machine either screw, ram, or roller type.

Out of the screw & Ram type machines, the briquettes are continuously extruded & punched respectively. In these types the dies can be made to produce the briquettes in the shape of cylindrical,square,hexogonal.

Out of the Roller type briquetting machine, the briquettes are pressed to the shape of the cavities provided in the roller dies. In this type the dies cavities are made to produce the briquettes in the shapes of oval or pillow.

The briquettes may be selected in the required shapes and the die is adopted to the machineThe pressed briquettes are next dried to complete the binding operation. When the water is dried out from the gelatinised starch it sticks the charcoal particles together to form a stable briquette which will retain its form right up to the point of combustion. The briquettes usually contain about 10% of binder and about 30% of water before drying down to about 2- 5% moisture content. The normal dryer is a continuous tunnel dryer which carries the briquettes through without allowing them to tumble. Heat for drying out the water is a significant operating cost. It can also be suggested to go for sun drying if sufficient sun light is available. Even tray drier is also advisable if the quantity is less.

When the briquettes are cool they can be packed for the market in paper or plastic sacks of about 5 kg.or as per convenience in marketing .

Depending upon the quantity/capacities ,shape of the briquette & availability of the sunlight, the project needs the briquetting machine along with screener, hammermill, grinder, mixer, conveyors, drier.

To view the images of different shapes out of Screw Type, Ram Type with hole & without hole, oval shape and pillow shape out of roller press briquetting machines click here