Neco Model Questions Vol1 2023 Agricultural Science Question 4

A farmer harvests 1 tonne of fresh cassava roots with an initial moisture content of 60 % (wet basis). He wishes to produce dried cassava chips with a final moisture content of 10 % (wet basis). The drying kiln operates at a constant temperature of 60 °C and the inlet air has a relative humidity of 30 %. The saturation humidity ratio at 60 °C is 0.044 kg water per kg dry air, and the latent heat of vaporisation of water at this temperature is 2,430 kJ kg⁻¹. Air flows through the kiln at 2,000 m³ h⁻¹; the density of dry air at standard conditions is 1.2 kg m⁻³. Assuming the air leaves the kiln at 80 % relative humidity (same temperature) and that drying is limited by the amount of water that can be removed by the air stream, calculate the minimum drying time (in hours, to one decimal place) required to achieve the desired moisture reduction. Ignore heat losses.