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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Crystallization Of Hydrochloric Acid Problem in Pickling System
Q. WHAT MAKES HYDROCHLORIC ACID CRYSTALIZE? WE HAVE A PUMP THAT IS BECOMING BLOCKED AT THE DISCHARGE AND IMPELLER WITH CRYSTALIZED HCl.THE CONCENTRATION IS ABOUT 32%.
SCOTT W. WRIGHTSTEEL - HUGER, South Carolina.
2007
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2007 A. The short answer is: something that's not hydrochloric acid. Pure HCl might freeze, but only at subzero temperatures.  Dave Wichern Consultant - The Bronx, New York 2007 A. Hydrochloric acid is a gas - hydrogen chloride - dissolved in water. It does not crystalise, at all, ever.  Geoff Smith Hampshire, England A. HCl does not crystallize. What you're likely seeing is metal salts. You'll likely have to reduce the metal concentration of your HCl. Get a metal analysis done and then look at solubility charts.  Jeffrey Holmes, CEF Spartanburg, South Carolina 2007 A. Hydrochloric acid of 32 wt% freezes at -43 °C, so perhaps unlikely. - Goleta, California 
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from. 2007 |
A. Strange that the discharge of the pump is getting blocked. The fluid velocity should make sure it is clear at all times. Is it blocking while the pump is stopped ? If so perhaps flush some clean acid/water to ensure pump remain with 'clean' liquid in - often you can get settlement of solids from product, congregating at the bottom of the tank, and the pump is mounted at the bottom so could be this.
The discharge especially should not clog as it should be smaller than the pump suction bore, so velocities will be really high ? If it is a solids matter, then you will have added issues of bearing lubrication if it is a mag-drive - which needs its own special set of rules applied to overcome these associated issues.
pumps - Northants, England
2007
Is there a pickling additive to prevent crystallization?
Q. We have a pickling line in Belgium, Europe and we have the same problem with our FeCl concentration in combination with low temperature.
The valves are getting blocked by crystallization.
Reducing the concentration of iron in the liquid is a solution, but that makes the process less efficient.
Is there a product we can add to the acid to prevent crystallization?
pickling - Evergem, Belgium
January 21, 2015
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
A. It would be possible to add a chelating agent such as tetrasodium EDTA to increase the solubility of iron. But the cure might be worse than the disease, since it would adversely impact waste treatment.
Tom Rochester
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.
January 24, 2015
A. We have crystallization problem too, but I think if we set two valves in upward and downward of line to circulating the water to dissolving crystals, maybe we succeed and solve the problem. I haven't tried like this but it seems executable.
maasum maasumichlorine - iran, urmia
September 21, 2015
Q. Will adding an inhibitor help to eliminate this problem or could that be the root cause of the issue?
Larry Malone- Mobile, Alabama
October 2, 2017
A. Keeping Sodium chloride(Common salt) in excess will solve the problem of crystallization of Iron.
Shankaranarayanan Narayanaswamy- Belgaum, Karnataka, India
October 6, 2017
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