Diffusion Apparatus

a device for extracting soluble substances from pulverized solid material. Diffusion apparatus is widely used in the food industry, mainly in the sugar industry, where it is one of the basic types of technological equipment. Water extraction of sugar from sugar-beet shavings or from ground sugarcane is performed in diffusion apparatus.

A distinction is made between diffusion apparatus with periodic and continuous operation. The periodic-operation type includes diffusion banks consisting of an even number (12-16) of diffusers and the same number of preheaters joined into a circular system. The banks operate according to the counterflow principle: the water enters the last diffuser, which contains sugar-beet shavings from which the sugar has already been removed, and gradually becomes enriched with sugar as it is pumped in sequence through all the diffusers from the bottom to the top and is drained from the last diffuser in the form of juice. Such diffusion equipment is extremely cumbersome and requires considerable expenditure of labor for maintenance and repairs.

About half of the plants in the USSR are equipped with continuous-action diffusion apparatus. The most widespread are the vertical single-column and multicolumn, inclined trough, and horizontal rotary diffusers. In the first type, the shavings are moved upward by an auger, blade, or chain conveyer and are unloaded from the upper part of the equipment in pulp form, and the water flows continuously through the column of shavings from top to bottom; the diffusion juice is drained off through a sieve from the lower portion of the column. In inclined diffusion equipment, the shavings are moved from the bottom upward by a pair of parallel belt conveyers and are unloaded in the form of a pulp, with the aid of a paddlewheel. The device is fully automated. In horizontal diffusion apparatus, one- or two-trough helical partitions, which separate the drum into a number of sections, and grids that pass the shavings from section to section in a direction opposite the water flowing along the helical partition, are rigidly fastened to the inner walls of the rotating drum.

Diffusion apparatus with a continuous horizontal perforated belt to move the shavings and a system of counterflow pumps that move the water or juice consecutively through the individual sections of the conveyer also exist. The use of a series of liquid cyclones for extracting sugar from sugar-beet shavings holds promise. The use of continuous-action diffusers makes possible the full automation of the process, the reduction of labor expenditures by a factor of 5-8, a decrease in sugar losses in the pulp, and an increase in overall production efficiency. The output of a diffuser is 1,500-3,000 tons of beets per day.