How to calculate and recover HCl gas escaping during tank loading

[bigufo]

Hello, I work on a project on the recovery of gases HCl 33 % which escape during the load of this last one in tanks. I want to know if you can help me or propose me a solution for the calculation of this quantity of gas and if you have an idea of a method to get back them. or any information about the evaporation of hcl during loading
thank you very much

 

[Q_Goest]

Hcl has a saturation pressure of 629 psia @ 70 F, so any transfer I would assume is done completely under pressure. The only losses should be when connections are purged to blow out any air that might be in the connector.

Leaky connectors may present some losses too, and Hcl is highly corrosive when exposed to atmosphere. The Hcl equipment I've seen is coated in rust, even the stainless steel. I believe Monel is a better choice for any fittings exposed to Hcl and atmosphere though I'd need to check, I don't have a material compatibility book handy.

What other losses are there? Are you concerned about sending back a partially full tanker of Hcl? Does your company pay for the entire load and not get a complete load off or are you paying by trailer weight? If you're paying by load, doing things to reduce the amount sent back should be fairly obvious. You could pump the trailer down to about 160 psia which corresponds to a saturation temperature of -20 F. That's the point at which many steels can become brittle and you may find the cylinders start to frost up. But even pumping it down to that pressure would help if you're paying by the load and not by trailer weight.

 

[FredGarvin]

From what I have seen, stainless is a no-no with hydrochloric acid of any concentration.

http://www.polyprocessing.com/pdf/literature/PositionStatements/HYDROCHLORIC_ACID.pdf

Go here http://www.xpress-link.net/chemsearch.asp and select Hcl from the list to get a good chemical compatability chart.

 

[bigufo]

HCl evaporation rate

Thank you very much FredGarvin and Q_Goest for your answers,
but the pumping is made under atmospheric conditions (pressure & temperature) and nevertheless there are gases that escape, it is a small quantity but I have to recover it. It can be due to the barbotage caused by the operation of load or a simple natural phenomenon but i need to know the evaporation rate of HCl at these conditions. (i have already an idea for the recovering process in my mind, but the problem is how can i measure or calculate the quantity of gases that escape)
thank you again

 

[FredGarvin]

You may want to post a question in the chemistry section in regards to the evaporation rate. I'll keep hunting to see if I can find anything.

 

[Q_Goest]

The values for saturation pressure and temperature are for pure Hcl, I missed the fact you're operating with some lower volume. What is the concentrations of fluids (mole percent)?

 

[bigufo]

the concentration of HCl is 33%

 

[Q_Goest]

But what is the other 67%? And is that mole percent or volume?

 

[Bystander]

Aq. HCL: you're looking at a few grams of solution lost as vapor per cubic meter of air displaced from the tank; larger losses from mist and aerosol which is going to be a function of tank geometry and filling mechanism (dump from the top and splash, fill from bottom through baffles).

 

[bigufo]

Q Goest: 33% HCl 67% water (mole percent)
Bystander: you're right that is what i need. the loading operation is a dump from the top and splash, and the tank is a horizontal cylinder with a circular opening in the summit for the load. so my question is : is there any correlation between (tank geometry, filling mechanism, the flow rate of the solution, distance of the flexible from solution) and the quantity of gases lost as mist and aerosols? if not do you have any idea to evaluate this quantity?

 

[bigufo]

ok, i admit that it was a difficult question, so i have to deal with the problem using the actual few informations
thank you again