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(4 marks) Question 2 (Answer all parts, 48 marks) Figure 1 shows the P&ID for an agitated vacuum filter dryer along with some associated systems. The equipment is to be used to dry a finely divided, combustible, organic solid powder with low toxicity and with a low minimum ignition energy. Previous published studies have shown that the product can be dried safely and in an acceptable time operating with an absolute pressure of 50 mbar and limiting the maximum powder temperature to 40°C. The particulate material is transferred into the filter dryer in suspension in a medium volatility, highly flammable, non-conductive solvent. The wet filter cake is washed using the same solvent, most of which is removed at the end of the filtration step. Focus your answers on the drying phase of the process. (a) Identify and explain three attributes of the materials being processed which present a hazard in terms of the potential for a fire or explosion [2 marks for each, total 6 marks) PLEASE TURN OVER
(b) Propose a basis for safety for the drying operation identifying three distinct aspects of the operation which must be addressed to have a sound basis for safety. In each case explain how this may be achieved using three of the features shown in the figure. [3 marks for each, total 9 marks) (c) Considering the following parameter and guide word combinations, use your knowledge of HAZOP to evaluate the drying operation using the filter dryer shown in Figure 1 and hence develop deviations which could jeopardise the safe operation of the unit. Combination Parameter Guide Word Comments 1 Agitation More 2 Temperature More Applied to the powder bed 3 Inerting Other than In this case air enters the system through an open path to the atmosphere For each of these three given parameter and guide word combinations, complete a HAZOP table using the following format: Suggested HAZOP table format: Parameter & (no marks, you are given this information guide word combination: Deviation (1 mark] Possible [2 marks] cause(s): Consequences: (3 marks] Existing [2 marks] safeguards: Proposed action [3 marks) to further mitigate the risk You need to provide enough detail in each cell in your table to demonstrate that you have understood the deviation, its causes and consequences, and the existing safeguards so that you can make appropriate mitigation recommendations. Writing one word in each cell is unlikely to score a high mark 137 m 11
Agitator motor with variable speed drive pitched agitator blade can be raised and lowered, rotates clockwise to dig & discharge the filter cale, counter clockwise to smooth the cake surface. The agitator blade incorporates a senior to measure the cake temperature TAH 00:04 High capacity bursting dish with a vacuum support plate vents to stack on building roof Wash solvent inter with spray ball to distribute was evenly Flow limited by restriction orifice and line earthed to prevent static build up Mechanical vacuum seal/bearing incorporating with temperature alarm Product spension inlet from cristalliset distribution plate to form an eventer cake Vent line with interlock to prevent intended opening during operation Nitrogen inlet Steam C00 B Cooling water JU00 M 07 END OF RADON ter med Perforated Sportplate Forate receiver chamber tre outlet valve Containe de product discharge wystem feeding reparate packing area dedicated to handling finely divided combustible dists Pilaterace Conden linked to cold ince Vacuum pum discharging to safe vent Condencat receiver rate was receive 1. Porotheated ter drye De repared for 212, CH218 CPU am PC 17.feb 2033 1