Pulp Grinder

a machine in paper and pulp manufacture for producing wood pulp by grinding wood on a rotating abrasive wheel. A distinction is made between periodic-operation grinders (hydraulic and magazine types) and continuous-operation grinders (chain, screw, and ring types) according to the type of mechanisms for clamping the wood to the abrasive wheel. Continuous-operation chain pulp grinders, in which the pulpwood is loaded into a shaft and pressed against the wheel by continuous chains, are the most common type in the USSR.

The main working part of a pulp grinder is the abrasive pulping wheel, which is cylindrical. The wheel may be natural (made of sandstone) or artificial (made of quartz, corundum, or carborundum grains in a cement, ceramic, or other binder). Modern high-capacity pulp grinders use mainly artificial wheels 1,500-1,800 mm in diameter and about 1,400 mm wide, rotating with a peripheral speed of 20-25 m/sec. The pulp grinder is also equipped with apparatus for treating the surface of the wheel (smoothing or notching), a mechanism for automatic control of the pressure of the wood on the wheel, a bath in which the wheel is usually immersed to a depth of 50-70 mm, and spray devices for cooling the wheel and removing the pulp from its surface. The operation of the pulp grinder is controlled by an automatic meter of the amount of wood processed and by recorders of the temperature of the pulp in the bath and of the water pressure in the spray system.

The output of a modern pulp grinder with wheels 1,800 mm in diameter is up to 40 tons of air-dry mass per day at a shaft power of up to 2,200 kilowatts. The main trend in the further improvement of pulp grinders is toward an increase in output to 100-120 tons of pulp per day by increasing the diameter of the pulping wheel to 2,000-2,200 mm, its width to 2,000 mm, and the peripheral speed to 37-45 m/sec.