The Suitability of Various Forms of Rice Husk Ash as Desiccant

Abstract

<abstract> Abstract. The suitability of various forms of rice husk ash (RHA) as desiccant was investigated by determining their maximum moisture up-take (MMU) and cost-normalized moisture buffering capacity (NM) at eight relative humidity levels. The forms of RHA were uncontrolled open heap burning designated (UOH), pre-boiled laboratory furnace fired ash (PLF), reflux before laboratory furnace firing (RLX), and boiler furnace fired ash (LBF). Silica gel was used as control desiccant. The relative humidities were 30% to 100% at 10% intervals. Similarly, the relative humidity ranges at which moisture buffering capacity (M-value) were determined were 30% to 40%, 40% to 50%, until 90% to 100%. The study was undertaken using a 4x8 and 4x7 two-factor experimental designs for MMU and M-value, respectively, all replicated thrice. The MMUs were determined by gravimetric method. The NMs of the different inorganic desiccants were compared to the NM of RHA form with the best MMU using ANOVA at α=0.05. It was found that relative humidity and relative humidity range had significant effect on MMU and M-values. M Stat C software was used to separate the means showed significant difference existed. At saturation, for example, MMU of the various forms of RHA was of the order UOH>RXL>PLF>LBF. In terms of NM, UOH ash form did better than all the other ashes as well as other common inorganic commercially available desiccants. The use of calcium sulphate, alumina gel, molecular sieve, silica gel, calcium oxide, and calcium chloride would cost as much as 90, 86, 47, 31, 29, and 4 times, respectively, that of UOH ash. RHA, therefore, has high potential as an economic substitute for inorganic desiccants even in the humid tropics.