Straw pyrolysis carbonization technology

Technical overview

Straw pyrolysis carbonization is a process in which crop straw is converted into straw charcoal, straw gas, tar, wood vinegar and other products by using special carbonization equipment to cut the chemical bonds of hydrocarbons in biomacromolecules under anaerobic or limited conditions using heat energy. This technology can convert crop straw from low-grade energy into pollution-free, easy-to-store and high-grade "biocoal" energy. In addition, the sulfur content and ash content of straw charcoal are lower than those of coal powder, and the fuel quality is better than that of ordinary coal powder. It is a clean utilization technology for crop straw.

Technical points

Straw pretreatment and feeding

The straw is crushed by a crusher, and the length is generally not more than 5mm. After the crushed straw is dried to a moisture content of about 6% in a drying furnace or dryer, it directly enters the carbonization furnace through the feeding system. The crushed and dried straw can also be made into various shapes such as granules, rods, blocks, etc. by using a molding machine. The general specifications are 50~60 mm in outer diameter, 30~50 mm in length, and 12~15 mm in inner diameter. The produced straw charcoal can be used as a molding fuel for barbecue charcoal or heating charcoal.

Carbonization treatment

Carbonization is a pyrolysis process that can be divided into 4 stages.

Drying. The temperature is generally 120~150℃.

The pre-carbonization temperature is generally 150~275℃. Under the condition of oxygen isolation, the chemical composition of the straw begins to change, and some unstable components such as hemicellulose and lignin begin to decompose to produce carbon dioxide, carbon monoxide, and a small amount of acetic acid. The drying stage and the pre-carbonization stage are both endothermic reaction stages, and external heat energy is required to ensure the reaction.

The carbonization temperature is generally 275~450℃. The pyrolysis reaction of straw is violent, producing a large amount of methane, carbon dioxide, carbon monoxide, acetic acid, tar, etc. This stage is an exothermic reaction stage, and no external heat is required.

Combustion. The temperature is generally 450~550℃. Under the combined action of external heat supply and internal reaction heat release, the formed charcoal is burned. At this stage, the internal part of the straw charcoal changes, the porosity increases, a porous medium begins to form, and the specific surface area begins to increase.

Carbonization products and their applications

Straw charcoal. It has high carbon content, rich pore structure, large specific surface area, and stable physical and chemical properties. It is widely used as a fuel charcoal fertilizer raw material, soil conditioner, etc.

Combustible gas. After separation and purification, it is used for heating and gas supply.

Wood vinegar. It contains many trace substances and active factors, and has strong bactericidal, anti-inflammatory, insect repellent, virus killing, cell activation, and keratin softening functions. It is used in agriculture, animal husbandry, living environment, medical beauty and other fields.

Tar. It is mainly used in construction, metallurgy, energy and other fields.