recycled

In the process of drying carrots using a parallel flow drying system, the material with a moisture content of 85% enters the drying system at a rate of 500 Kg / hour to produce dry carrots with a moisture content of 20%. If it is known that hot air used as the drying medium has a humidity ratio of 0.006 Kg of water per Kg of dry air and the flow of hot air enters the system at a rate of 200 Kg of air for each dry matter produced, calculate the ratio of humidity to air leaving the system assuming that the system is under steady state conditions.

One way to make coal “cleaner” is to gasify the coal into “city gas”. In a proposed molten-iron coal gasification process pulverized coal of up to 3 mm size is blown into a molten iron bath and oxygen and steam are blown in from the bottom of the vessel. Materials such as lime for settling the slag, or steam for batch cooling and hydrogen generation can be injected at the same time. The sulfur in the coal reacts with lime to form calcium sulfide, which dissolves into the slag. The process operates at atmospheric pressure and 1400 to 1500°C. Under these conditions, coal volatiles escape immediately and are cracked. The carbon conversion rate is said to be above 98% and the gas is typically 65 to 70% CO, 25 to 35% hydrogen, and less than 2% carbon dioxide. Sulfur content of the gas is less than 20 ppm. Assume that the product gas is 68% Co, 30% H2, and 2% CO2. Calculate the enthalpy change that occurs on the cooling of 1000 m3 of the gas at 1475 °C and 1 atm to 25°C and 1 atm.

Magnesium metal, a gray solid, is heated in a crucible in the presence of oxygen. A white powder is collected from the crucible. This is an example of A) a chemical change B) a separation C) a mixture D) a physical change