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 place: Keep the water flowing through the straight run of the mixing tee, 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. Mixing tees with PTFE nozzles specially designed to disperse the acid uniformly into the process are available in 1" through 8" sizes. 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.