Increasing Bed Depth Research Articles

The use of coal spoils as feed materials for alumina recovery by acid-leaching routes: 2. The effect of the calcination conditions on the leaching properties of the colliery spoil

The results of muffle furnace calcination experiments, in which the temperature of the bed of colliery tailings was measured as a function of the nominal furnace temperature, are presented. ΔT, the increase in the bed temperature due to oxidation of the coal particles in the tailings was found to increase with increasing calorific value of the tailings and with increasing bed depth. ΔT values up to 150 K were measured at a bed loading of 5.6 kg m −2. The results of differential thermal analysis (DTA) and thermogravimetric (TG) analysis of the tailings, in both oxidising and inert atmospheres, and of reference clay mineral samples are also presented. The dependence of the leaching properties of the tailings and clay mineral samples on their thermal history was investigated. There was a marked increase in the rates of extraction of both aluminium and iron in the temperature range 823–1123 K. Above 1173 K the rate of extraction of aluminium decreased sharply. These results have been interpreted in terms of the various phase changes and chemical reactions undergone by the clay and non-clay minerals present in the tailings. Practical aspects of the controlled calcination of colliery tailings are discussed, and it is concluded that calcination in a fluidised bed combustor is the only suitable method on an industrial scale.

Dehydration of potato

SummaryDrying behaviour of potato in a natural convection, solar dryer was investigated. In drying experiments conducted at low air velocity, as found in the solar dryer, it was shown that air flow conditions are of critical importance for drying behaviour. As a result of the presence of extensive, external mass transport resistances in deep bed drying, the air flow behaviour of the bed was more important than the drying behaviour of the single pieces. Thus, for deep bed solar drying, 10x10 mm french cut potatoes dried faster than 5 mm slices. (This result was opposite to that found for drying in thin layers). Drying time was noted to increase less rapidly than bed depth increased, so overall dryer productivity increased with increasing bed depth, within the constraint that drying be completable in 1 day.

Combustion Mechanisms in Wood Fired Boilers

The emissions from combustion of wood residue fuel in an experimental spreader-stoker boiler were measured at the Fairplay Test Facility at Oregon State University. Stack gases were monitored to determine levels of excess air, opacity, and particulate loading. Particulate emissions were measured to determine the effects of underfire air flow rate and fuel bed depth on particulate carry over rate. An experiment conducted at four energy release rates and two fuel bed depths indicated that increased bed depth has the effect of reducing particulate emissions and that the effect increases as energy release rate increases. The experiment also showed increased energy release rate has the effect of increasing particulate emissions. The effects were found to be statistically significant.

Behavior of Radionuclides on Ion‐Exchange Resins

This article discusses a study of the behavior of radionuclides on ion exchange resins used for the decontamination of cooling water in a nuclear reactor. The principal objectives of the investigation were identification of the nuclides, measurement of their relative concentration as a function of bed depth, and interpretation of these data in the light of the effective performance of the system. Results showed that, in the cation, anion, and mixed‐bed columns, the concentration of radionuclides on the resin decreased with increasing bed depth. At the same time, the overall half‐life of the retained materials simultaneously increased. As anticipated, considerable variation with depth was observed in relative radionuclide composition, the shorter‐lived materials predominating near the surface, the longer‐lived near the bottom of each column. The data emphasize the care required in using data on gross radioactivity removals for the evaluation of the efficiency of an ion exchange system. This is true because the effluent, although exhibiting a “satisfactory” reduction in gross activity, may actually contain a significantly greater proportion, as well as actual concentration, of longer lived radionuclides.