Technology Package

The package comprises two major parts, pyrolysis and briquetting, details of which are below:

Pyrolysis Pyrolysis is a process in which biomass is charred for partial removable of volatiles. The pyrolysis temperature ranges between 250-500 deg C. The process, once started, will continue automatically and charcoal is obtained at approximately 500 deg C.

The Brick Beehive Pyrolyser, also known as the Stable Pyrolyser, is made of bricks and fine clay, and has many advantages such as:

• simple to construct

• low capital investment good yield

• suitable for domestic and industrial applications

• simple to operate

• relatively unaffected by thermal stresses

It has a domed roof and its wall is fully in contact with air. There are two doors, one on top and the other near the base, for proper loading and unloading of biomass and charcoal, and the doors are oriented keeping in mind prevailing wind directions. After filling biomass in the pyrolyser, the bottom door is closed. The biomass is set on fire from the upper door after which it is closed by metallic sheet and clay. Carbonization of the biomass is controlled by the air inlet holes. Each pyrolysis operation with a 100 kg. char yield takes between 6-8 hours and can be repeated daily or as per need.

Details of a Pyrolyser of 100 Kg. char yield capacities are as below:

Briquetting The principle of briquetting consists of applying pressure to small pieces of char particles and compacting them. The briquettes could be solid pieces or in the form of hollow cylinders. Binders are substances such as molasses, starch, clay, resin, lime etc., which are used to bind particles of the primary material. The qualities of good binders include good binding ability, low cost, good smell while burning ready availability etc. The charcoal obtained after pyrolysis is first crushed into fine powder with the help of wooden or metallic rollers. After fine grinding, 7-10% (by weight) binders are mixed into the char powder. About 4-6% clay is also mixed to increase the agglomeration of the mixture. The mixture is stirred well for homogeneity. It is then converted into briquettes in a briquetting machine, which could be of the following types:

• Power operated

• Manual

• Bullock operated

In the manually operated machine, the die box is filled with the mixture and closed. The mixture is compacted by applying pressure on the punch with connecting rod, opening the lid and then applying a small amount of pressure on punch. The briquettes are taken out and dried in the sun. These briquettes are smokeless and do not produce unpleasant smell when burning.

The following is a typical example of conversion flow: Assuming a pyrolyser capacity of about 425 kgs. and 15 firings per month, total biomass pyrolised would be about 6400 kgs. This would yield about 2100 kgs (roughly one third) of charcoal. To this is added - binder (molasses), 10% by weight and clay, 8% by weight. This yields about 2478 kgs. of briquettes.

Use of briquettes for domestic purposes increases efficiency of use about 30-40% above the 9-15% of wood. The briquettes also prevent the problem of smoke and is hygienic and less energy intensive. The calorific values of briquettes of this biomass are equivalent to Grade B and Grade C coal as tabulated below:

• Grade B coal 4500-5000 kcal/kg.

• Grade C Coal 3500-4500 kcal/kg

• Lantana Briquettes 5100 kcal/kg.

Binders Various kinds of binders can be used depending on availability. Some of the more common varieties are:

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