Handling Hydrochloric Acid
Hydrochloric acid (also known as muriatic acid) is a highly corrosive
solution which plays a prominent role in the production of chemicals,
petroleum, metals, textiles, leather and food products. The pure
solution is colorless, but traces of iron, chloride or organic
matters can impart a yellowish tinge.
Concentrated hydrochloric acid is one of the strongest acids known.
It readily attacks common metals to yield hydrogen, which is explosive
in certain concentrations with air.
Freezing points of HCl solutions
Molarity vs. weight percent HCl solutions
Specific heats of HCl solutions
Heat evolved on infinite dilution of HCl solutions
Vapor pressure of aqueous solutions of HCl acid
Few metals are suitable for uses involving direct contact with
hydrochloric acid due to its extreme corrosiveness. Metals that can be
used often have a very limited range of applications.
Acid dilutions in plastic-lined pipe
One of the more common operations in handling hydrochloric acid in lined
piping is dilution to a lower strength acid. This is usually done
with a mixing tee. There are usually no problems in doing this if the
heat of dilution is taken into consideration during system design.
Therefore, the following points should be considered in the design
and installation of any system in which acid dilution will take
Mixing tees with PTFE nozzles specially designed to disperse the acid
uniformly into the process are available in 1" through 8" sizes.
- Keep the water flowing through the straight run of the
and bring the sulfuric acid in the side outlet.
- Provide check valves in both the acid and water lines to prevent
backflow and unwanted mixing, which could occur if there were a flow
interruption of either stream.
To add a margin of safety, it is recommended that PTFE-lined pipe be
utilized in the immediate mixing area, upstream of both check valves
and approximately 20' downstream of the mixing area.
- Size the piping to ensure turbulent flow for good mixing and a
minimum of hot spots.
- Provide the point for acid dilution as close as possible to the
point at which the diluted acid will be used or stored. This will
minimize the amount of piping required to handle the hot acid.
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