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I'm currently working in a Chemical Plant as an intern, and I was given a task to improve the efficiency of the blower, which is already in place right now, by designing a new blower for the appropriate flow rates.

We have a filling station in the plant for HCl liquid, which fills the HCl (30-32% conc. at 20 m$^3$/hr) into tankers for transportation purposes. The problem is when HCl is filled up in a tank, it releases fumes, which are harmful for the people present near the filling station.

We have to recommend a blower, so that most of the generated fumes can be treated at an appropriate flow rate. But we don't know how to proceed with this, as we wouldn't know about the evaporation rate of HCl while it is flowing inside the tank.

Some technical information:

  1. Temperature, Pressure can be assumed as 30 $^{\circ}$C, 1 atm.
  2. Flow rate of HCl inside tank: 20 m$^3$/hr.
  3. Capacity of Tank: 25 Metric tonnes
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    $\begingroup$ Kudos to you for considering the health of workers! The simplest and most economical way to avoid HCl vapors is to vent (i.e., waste) at a high altitude, like flaring CH4 from petroleum drilling. However, the vented HCl is a raw material if you capture it in H2O - you should be able to get up to about 20% before the vapor pressure of HCl is evident. Run the vented vapors thru a wet column and sell the diluted HCl as a by-product (cheap?). Up to about 20% HCl has no significant odor of HCl. $\endgroup$ Commented Jul 15, 2022 at 13:57
  • $\begingroup$ I don't think these would work. We have to remove fumes from a tanker, which would be filled up and transported to another location. While being filled, the HCl will release fumes, and we need to find the amount of fumes generated, so that we can suck those out with the help of a blower, and transport them back to the HCl storage. I just need the amount of fumes generated, so that I can recommend a blower with an appropriate flow rate, and appropriate pipe diameter which can handle the pressure drop. $\endgroup$ Commented Aug 25, 2022 at 11:46

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When HCl is put into a tank, it releases fumes... And this is not an equilibrium situation (just like pouring a carbonated beverage into a glass can be done rapidly or slowly, releasing various amounts of CO2).

You may be able to get some numbers useful for calculations (if you also specify a range) from the two references below (1 and 2). No. 1 has a nomograph that shows the concentration of HCl in the liquid and vapor, and No.2, which is a fairly large handbook of safe handling for HCl, has a different way of expressing the information:

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Knowing your volumes and tank flow rates and other estimated required flow rates, along with the amount of HCl in the vapor could help decide what kind of pump you need. And don't forget to inquire of your HCl supplier, who might have significant, relatively private, but not actually confidential, information about how other customers succeed (or fail) with their methods of handling this task. Sometimes calculations don't take everything into account, but a successful solution is worthwhile, even if if is "supported" by calculations.

Ref 1: https://pubs.acs.org/doi/10.1021/i460001a002

Ref 2: https://www.jsia.gr.jp/data/handling_02e.pdf

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This is a job for a competent chemical engineer not an intern; find one and suggest hiring a consultant. I am dismayed that HCl gas is released to the atmosphere and think that OSHA should get more involved with your company. Since the air volumes displaced in the delivery tank and the receiving tank are the same [and should be readily determined] a vapor recovery system should be imperative in handling such materials. Look into it. Learn all you can about the overall process. If that fails, get a better internship.

Some things to consider: 30 degrees Celsius seems a very high temperature to be handling concentrated hydrochloric acid; what is going on here? Also work with the same units; convert the masses to volumes; learn about head spaces etc. in the shipping.

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  • $\begingroup$ Thanks for your valuable suggestions, I guess a consultant would give a better answer to this. Answering your question about the temperature, the company is situated in Pondicherry, India. The environment here is quite humid and hot, so I wrote 30 degrees Celsius as the surrounding temperature (average). I assumed this would be the temperature inside the empty tanker as well, not sure if that's the case. $\endgroup$ Commented Aug 28, 2022 at 17:40

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