Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 255

Briquette manufacture (also known as briquetting) is undergoing resurgence, principally due to the convergence of three critical factors. In fact, the recent developments in briquette processing and binding have dramatically changed the economics of using fuel briquettes as an energy resource. Also, a shortage of fuel wood has become increasingly severe in most of the developing countries. Finally, there has been a steady increase by environmental concerns to address the problem of domestic and urban waste disposal, a dilemma that briquetting can help remedy.

Generally, briquette manufacture (briquetting) involves the collection of combustible materials that are not usable as such because of their low density, and compressing them into a solid fuel product of any convenient shape that can be burned like wood or charcoal. Thus, the material is compressed to form a product of higher bulk density, lower moisture content, and uniform size, shape, and material properties. Briquettes are easier to package and store, cheaper to transport, more convenient to use, and their burning characteristics are better than those of the original organic waste material.

The raw material of a briquette must bind during compression; otherwise, when the briquette is removed from the mold, it will crumble. Improved cohesion can be obtained with a binder but also without, since under high temperature and pressure, some materials such as wood bind naturally. A binder must not cause smoke or gummy deposits, while the creation of excess dust must also be avoided. Two different sorts of binders may be employed. Combustible binders are prepared from natural or synthetic resins, animal manure or treated, dewatered sewage sludge. Non-combustible binders include clay, cement, and other adhesive minerals. Although combustible binders are preferable, non-combustible binders may be suitable if used in sufficiently low concentrations. For example, if organic waste is mixed with too much clay, the briquettes will not easily ignite or burn uniformly. Suitable binders include starch (5 to 10%) or molasses (15 to 25%), although their use can prove expensive. It is important to identify additional, inexpensive materials to serve as briquette binders and the optimum concentrations of the materials. The exact method of preparation depends upon the material being briquetted but, in general, the overall process can be presented as a step-wise operation: Thus:

See also: Briquette, Briquette Binder, Briquette Properties, Briquetting Processes.