Process design engineers a rayon manufacturing plant suggest introducing a new p

Question

Process design engineers a rayon manufacturing plant suggest introducing a new process that uses the solvent formaldehyde. Preliminary evaluations suggest that the new process will add a slight amount of formaldehyde vapors to the plant atmosphere, perhaps 1ppm by volume, in addition to current levels of the other air contaminants listed in below. The plant engineer has had foresight to invite the safety and health manager to join the design team for an additional perspective into the design process Perform calculations and evaluate the potential impact of new process proposal on the safety and health of workers in the plant. What recommendation would you make to the design team? Exposure Levels Morning Exposure 4 hour Afternoon exposure 4 hour 0.5ppm (p/m) 0.2mg/m Acetic anhydride Sodium hydroxide Ammonium Sulfide Calcium bisulfide Carbon disulfide Sodium sulfide Sodium sulfite ppm 5 ppm 4 ppm 0.7 mg/m3 0.5mg/m3 1 ppm 0.3mg/m3 4 ppm 8 ppm 6 ppm 0.8mg/m3 0.5mg/m3

Explanation / Answer

Formal dehyde is a natural occuring organic compound with formula CH2O.

It's a highly toxic systematic poison that is absorbed well by inhalation.

The limitations of formal dehyde is 0.1ppm by volume.When formal dehyde is present in the air higher than 0.1ppm, some people may have health effects, such as :

Recommendations:

Since the exposure is upto 1ppm, the limits is to be kept to 0.1ppm, keeping in view good health conditions of workers.

Evaluation:

a)Acetic Anhydride - Permissible Limits -5ppm.

Since, the exposure is with in limit, it is permissible.

b) Sodium Hydroxide - Permissible Limits - 2mg/m3

It's corrisive , and with in the permisible limits.

c) Aluminium Sulfide - Permissible Limits - It's safe unless it comes in contact with water.

d) Calcium Bisulfide - Permissible limits -0.3ppm.

Since, it's exposure is 5ppm in morning and 8ppm in afternoon hours, ithas to be limited to 0.3ppm to maintain air pollution.

e)Sodium Sulfide -Permissible Limits - 10ppm.

The exposures are with in the permissible limits, hence safe.

f) Sodium Sulfite - The thersold limit value is 5ppm over 8 shift.

The total exposure is 0.5 +0.5 =1 ppm which is with in limit.

Conclusion :

The exposure of Calcium Bisulfide and Formal Dehyde is beyond the limitation, it has to be critically examined for maintaining air pollution standards.

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