What Does Bed Depth Mean?
Bed depth is the height of the resin or filter media in an ion exchange column after it has been properly conditioned for effective operation, usually expressed in inches. This depth excludes any supporting bed.
A bed of resin can be used either to remove unwanted ions from a solution passed through it or to accumulate a valuable mineral from water, which can later be recovered from the resin.
The pressure drop through a resin bed primarily depends on the bed depth and the flow velocity of the water. It is further influenced by the particle size distribution of the resin and by the viscosity, and thus temperature, of the water.
Corrosionpedia Explains Bed Depth
Bed depth is the height of the ion exchange or filter media in the vessel after preparation for service. The bed is a mass of ion exchange resin particles or filter media contained in an ion-exchange column. The quantity of resin required depends on the water flow, total hardness and time desired between regeneration cycles.
For effective regeneration, the design of the vessels should give a maximum resin bed depth, while limiting the pressure drop across the resin bed to ~1 bar. The optimum column diameter must be a balance between the resin bed height, the ratio of resin height to diameter (H/D) and the linear velocity. H/D should be in the range of 2/3 to 3/2.
Vessel sizing should be adjusted to allow for resin expansion. Typical resin bed depth is 1.2 m (4 ft) for co-current and block regeneration systems and 2 m (6.5 ft) for counter-current packed bed systems.
Most resin manufacturers' strong-acid cation capacity data is based on conventional regeneration techniques in a laboratory column containing a 30-inch-deep resin bed. Assuming that all other factors remain constant, a 24-inch bed has approximately 10% to 15% less capacity than a 30-inch bed, and a 60-inch bed has 5% to 15% more capacity.
Sorbent bed height strongly affects the volume of the solution treated or throughput volume. Bed depth has an appreciable effect on gel cation capacity. Parameters such as bed depth can be critical, as well as ensuring a means of retaining the bed in a fixed location. In most applications the process improves if the bed depth is increased.