Development of circulating fluidized bed adsorber

Abstract

A new fluidized bed which is divided in a looplike shape by a partition wall has been developed for recovering trace elements from a large quantity of industrial water. The bed, a circulating fluidized bed applicable to a liquid-solid two-phase flow, is called a circulating fluidized bed adsorber (CFBA). Adsorbent particles are mixed and carried along with water in the CFBA. At the upper part of the bed, the adsorbent particles are separated from the water flow and recycled in the bed; the depleted water flows out of a water outlet. The CFBA is operated at two to three times higher velocity than conventional liquid-solid contacting systems. The pressure drop in the CFBA is in proportion to the amount of adsorbent suspended in the contacting section. Characteristics of the CFBA, including design considerations, are described.

Uranium adsorption characteristics of a circulating fluidized‐bed adsorber

“…Smaller adsorbent particles are carried over more easily than larger ones. Thus, the working velocity region, in which the adsorbent particles circulate well in the CFBA without deposition and carryover, becomes lower and narrower as the particles become smaller (Nakamura et al, 1990). The appropriate adsorbent particle size should be determined from the viewpoints of both the adsorption rate and the working velocity region.…”

“…Adsorbent particles stay in the packing section for a considerable portion of total adsorption period. They slowly move downward, and their presence prevents a backward flow of freshly supplied water (Nakamura et al, 1990). We assumed that the uranium adsorption is negligible, but the intraparticle transport of uranium took place in the packing section.…”

“…The performance comparable to a conventional fluidized bed could be obtained in these beds (Ito et al, 1991). Excessive increase in the contacting section height, however, causes the increase in pressure drop through the bed (Nakamura et al, 1990). Thus, the contacting section height should be designed considering both the uranium adsorption rate and the energy consumption to the force transporting the seawater.…”

“…Outline of CFBA Figure 1 shows CFBA used in the experiments, whose principle was previously described (Nakamura et al, 1990) and is only briefly outlined here. Water fed into the vessel from a nozzle (water inlet) develops a jet along the horizontal bottom wall and mixes with the adsorbent particles falling through a slit (particle nozzle) from the packing section.…”

“…New contacting devices that overcome deficiencies of conventional fixedand fluidized-bed contactors are urgently needed. For this purpose, we developed a new type of fluidized bed, called a circulating fluidized-bed adsorber (CFBA) (Nakamura et al, 1990). CFBA consists of two rectangular pipes separated by a vertical partition wall.…”