The manufacturers of a new oatmeal product want to determine the least expensive way to safeguard and transport their product. They chose lyophilisation (freeze drying), which removes most of the water from the product, making it lighter and therefore less costly to transport over long distances, and substantially increases its shelf life. Lyophilisation also removes some of the impurities introduced by industrial farming methods.

A solid feed stream containing 70 wt% oatmeal, 27% water (ice), and the balance organic impurities enters a heated vacuum chamber at a rate of 1 x 103 kg/hr at a temperature of -10°C. In the vacuum chamber, 97% of the water and 99% of the organic impurities in the feed sublime (vaporise). The dried product in then packaged and shipped. A vapour stream emerges from the chamber at 15°C. During the process, 7.95 x 10° kJ/hr of heat is transferred to the system.

(a)Calculate the compositions and flow rates of the product and waste streams.

(b) Find the temperature of the product stream, using the following values for heat capacity and heat of sublimation and neglecting the contribution of the organic impurities to the energy balance.

C _p [H20(s)] = 2.11 kJ/(kg.°C)

C _p [H20(v)] = 1.86 kJ /(kg.°C)

C _p [oatmeal] = 1.5 kJ/(kg.°C)

(ΔĤsubl) H ₂ O = 2845 KJ/kg

Answer rating: 100% (QA)

a Known feed compostion and flow rate Unkown vapor flow rate and product flow rate There are 3 compo... View the full answer