A process description for a reagent mixing and delivery system is provided below. NaHS (a dry powder) is delivered by truck to the mine site in 25 kg bags. The

dry NaHS powder is mixed with water in a mixing tank to 5% strength. The resultant NaHS solution is then sent to a storage tank, which is large enough to store one week's supply of 5% strength reagent solution.The fumes from the solutions are hazardous, and need to be sent to a scrubber before release to the atmosphere. Therefore, there is a connection for vapour discharge from both the mixing tank and the storage tank to the scrubber to treat vapour from the tanks before release to the atmosphere. Another reagent, SMBS, is similarly mixed with water and stored in another parallel reagent mixing and delivery system. Similarly, the vapour from SMBS solution is hazardous, and is sent to a scrubber for treatment before release to the atmosphere. There are therefore two parallel reagent mixing and storage systems. The two reagent mixing and storage systems are similar, so in order to allow for plant flexibility, it is proposed to connect each mixing tank with both storage tanks in the parallel trains. This would allow for storage of excess reagent from one train in the second train if required during the operation. Draw a PFD for the two interconnected reagent and mixing systems. Below is a copy of icons that may be useful to use in your PFD: marks)The vapours from SMBS solutions and NaHS solutions are not compatible and can aggressively react producing heat and corrosive liquids when they come into contact. Conduct a HAZOP for the vapour feed lines from the mixing tank and storage tank to one of the scrubbers. Conduct the HAZOP for the process variable "Flow" only. A risk matrix is provided below for use when conducting the HAZOP. Are there any design changes that you would propose to this system as a result of conducting the HAZOP? Discuss.