Question

A chemical company propose to build a formaldehyde production plant using catalytic oxidation of methanol method. As a group of engineers in the company, you are assigned to write a material balance proposal for the plant. The material balance proposal should consider the following steps; a) Introduce background and reactions involve in the production of formaldehyde through catalytic oxidation of methanol method. Hence, identify the required raw materials for the process. b) Propose a process flow diagram, which consider mixer, reactor and separator as the main equipment. Unreacted reactants should be recycled, however 20% of the unreacted methanol should be send to the product stream of the separator as product stabilizer. 2 c) State basis of calculation and solve the material balance when overall conversion of methanol is within (80-90) %. Ratio on the amount of feed reactants should be fixed accordingly before entering the reactor. d) Present the material balance summary (from part c) in a form of table. The summary should consist of the mole and mass flowrates and compositions of each stream. Material balance of the process should be validated as a conclusion to prove the proposed design. e) You propose to further purify the produced formaldehyde from separator (part c) through reducing the amount of water content by 50%. The purification process should be performed in a condenser and consider only the water that condense. Determine composition of the gas and liquid outlet streams of the condenser. The produced formaldehyde gas mixture from separator enters the condenser at temperature of 120oC and should be cooled at constant pressure in the range of (500-600) mm Hg. In the condenser, vapour is in equilibrium with liquid, and the vapour is ideal. Use the pre-determined composition of water in gas outlet stream to determine the Tdp and set the outlet temperature of the gas mixture. The outlet temperature should not be set below the Tdp of methanol and formaldehyde of the mixture. Justify and prove your choice. f) The produced formaldehyde from condenser (part e) is then pump to a 300 L storage tank. The gas temperature should be set within (20-30)oC. Identify the suitable pressure to be set for the storage when the gas mixture is considered as i) an ideal gas and ii) non-ideal gas. Evaluate and discuss on the determined pressure.

Answer 1

The process flowsheet and the material balance on various systems are shown below .

Some random data is assumed and calculations are performed.

Answer to the first 4 parts is provided below.