Experimental Study of Chemical De-scaling-I: Effect of Acid Concentration

Chemical cleaning is employed frequently for de-scaling exchangers in combination with other cleaning methods. A customized chemical solution is circulated through the scaled apparatus for certain time following drainage and washing. Many cycles of cleaning may be necessary to reach satisfactory de-scaling level. The composition of the cleaning liquor is very important for efficient de-scaling. The scale from an industrial boiler is treated with four different acid solutions at five different strengths to study their dissolving effect on the scale/deposits in the tubes of the boilers. Results reveal that 5% solution of HCl is the most effective to dissolve the scale in a specified time at room temperature. Sulfuric acid shows very poor de-scaling properties under the test conditions. The order of effectiveness to dissolve the scale deposits is HCL > HNO3> HCOOH> H2SO4. Hydrochloric acid may provide 30-50% savings on the circulation time as compared to HNO3 based on the rate of dissolution. 1 NFC Institute of Engineering & Fertilizer Research, Faisalabad, 2 Department of chemical engineering and Environmental Technology Graz University of Technology, Austria, E-mail: [email protected] 3 Institute of Chemical Engineering & Technology, University of the Punjab, Quaid-e-Azam Campus, 54590 Lahore, Pakistan Journal of Faculty of Engineering & Technology, 2007-2008