23.2.3 Technical questions

1.  Discuss the merits of the process from waste minimization perspective ?

Ans: In this flow sheet, the raw material itself is used as a solvent to extract the product. Also, one of the reactants (water) is used as another absorbent. The usage of raw materials and intermediates in the process as absorbents itself is very attractive from waste minimization perspective as waste water streams are not produced significantly. Also, the solvent used is benzene itself which reduces the complexity of using another solvent and subsequent safety related issues.

2. Comment upon the corrosion issues of the processes ?

Ans: HCl is very corrosive and therefore, enough precaution shall be taken towards the plant and process design.

3. What impurities are removed in the unit B scrubber using water ?

Ans: Benzyl chloride has limited solubility with water. Therefore, it is expected that benzyl chloride is dissolved to some extent in the unit B scrubber where benzyl chloride as an impurity in minor amounts can be removed from phenol.

4.   Why do you think make up HCl is required ?

Ans: Some HCl gets reacted to form poly benzyl chlorides. Some HCl gets lost as a vapour in various operations. Therefore, some make up HCl is definitely required in the process though, HCl is largely regenerated.

5. Compared to other Benzene based phenol production processes, what advantage this process has towards phenol production ?

Ans: In this process, very little quantities of other raw materials are required. These are HCl. Air is inexpensive and is freely available. Therefore, the plant can be build easily as many other auxillary processes are not required provided benzene is available in large quantities in the vicinity. However, one basic drawback is that the fixed costs of units will be high in this case as HCl is involved.