Utilization of wood waste products as fuel for heat production

Technical justification for use of wood waste products
as fuel for production of thermal energy

Wood of various types consists of cellulose (40-50%), lignine (16-33%), hemicellulose (15-30%), extractable substances and inorganic impurities (1-2%). Cellulose and hemicellulose are polysaccharide (carbohydrated polymers). Lignine consists of phenyl propane structural units; methoxyl and phenolic prevail in lignine from functional groups.

Wood and its components are easily exposed to various chemical transformations at rather low temperatures, under influence of oxygen from air and sun rays (processes of rotting). Thus a significant amount of low-molecular connections is formed: sugars, phenols, furfurol, aromatic and aliphatic hydrocarbons, etc. All these substances, being harmful enough in their majority, will penetrate into subsoil waters, into the atmosphere and cause negatively influence on the environment. When solid industrial wastes are being recycled, technological compounds used in manufacture get into the environment as well. For example, when 1 m3 of plywood trimmings are recycled for heat production about 50 kg of phenolic resin can get into the environment.

Utilization of wood waste products as fuel for production of thermal energy has a number of advantages:

• Low ash content of wood waste products - not exceeding 0,1-0,2% - goes into solid waste products;
• There is no sulfur in wood waste products;
• Low corrosion activity of flue gases;
• Emission of carbonic gas is reduced since waste products actually emit the same volume of СО2 when burn or rot.
• Emission of harmful substances into the atmosphere decreases considerably since at working temperature in the combustion chamber (reaching 700-1100°С) all extraneous chemical compounds are completely or partly decomposed, including phenolic resins;
• There is an opportunity to use damp wood waste products;
• Low price: burning of 3 kg of wood fuel releases the quantity of heat equivalent to burning of 1 kg of oil fuel or 1 m³ of natural gas.