For the mercury cell process and the membrane cell process, answer each other questions below.

1. number of reactors: the fewer reactors needed, the cheaper is the plant cost; assume one reactor is needed per desired chemical reaction step in the design (this may overestimate)

2. number of separators: the fewer separators needed, the cheaper is the plant; typically a minimum of 2 separators are needed per reactor (one "crude" and at least one "polishing"), frequently more.

3. phases of materials present: when given the choice liquids are preferred over gases as working fluids while gases in turn are preferable over solids, though often you don’t have a choice because "that’s the way it is". however a reaction path where all the components are liquids would likely be preferred over one where some components are gases or solids unless there was another compelling reason to go with the second reaction path (e. g., a much simpler process or a far superior catalyst). equipment to handle liquids usually is of smaller size (volume) than equipment to handle the same mass of gas. pumps (liquid handling) are cheap to buy and run; compressors are more expensive (gas handling). solids-handling equipment may have low initial capital cost but often high operating and maintenance costs due to frequent and costly breakdowns or frequent replacements – more spares may need to be purchased to minimize downtime. gases are more susceptible to fugitive emission problems than are liquids (or solids, but solids may have potential explosion hazards from dust).

4. process pressure issues: ambient pressures (< about 10 atm) are preferable to high pressures (> 100 atm) which in turn are considerably more preferred than low pressures (< 1 atm). plants operated under vacuum (< 1 atm) are extremely expensive to run.

5. process temperature issues: "ambient" temperatures (~20-250oc) are preferable to high temperatures (> 500oc) which in turn are considerably more preferred to low temperatures (< 0oc).the energy needed by a cryogenic (low-t) operation to achieve a temperature decrease of 10oc below ambient, costs about 10 times the energy needed for a 10oc temperature increase above ambient.

6. process hazards: the process using the least hazardous raw materials and/or intermediates is favored. the process generating the fewest hazardous intermediates, in the least quantities, is favored. the process requiring fewest extremes of t and p is favored. the process generating the least amount of, and least hazardous, waste is favored. (what is a waste? – a product or by-product that has no sale value, and may even cost money for disposal. if the reaction generates a secondary product that can be sold then that is a by-product not a waste. however a by-product can become a waste if the effort to recover it in saleable form – purity, quantity – is so costly that it negates any profit from its sale. for example a plant may generate a dilute acid as by-product but if a market exists for the acid in concentrated form only and the evaporation of water from the acid to get the higher concentration is too expensive then a better option might be to neutralize the acid with caustic to prevent the dilute acid becoming a waste.) etc. in comparing hazards of several processes note that the product must, of necessity, appear in all of these processes, so that any hazards associated with the product are common to all of those processes and are thus a "wash" when comparing the processes.