Experimental study on scale inhibition performance of a green scale inhibitor polyaspartic acid

Static and dynamic experiments were carried out to validate scale inhibition performance of a green scale inhibitor-polyaspartic acid (PASP). From the static experiment, it was shown that below 60°C, polyaspartic acid is very effective in scale inhibition, with the scale inhibition ratio exceeding 90% with only 3 mg/L PASP for the 600 mg/L hardness solution. For a higher hardness solution of 800 mg/L, the scale inhibition ratio can also reach 90% with 6 and 12 mg/L PASP at 30 and 60°C respectively. The SEM photographs of CaCO₃ crystals indicate that the crystal structure transforms from a compact stick-shape to a loose shape so that the scale can be washed away easily instead of being deposited on the heat transfer surface. The dynamic experimental results show that almost no scales formed on the heat transfer surface and the fouling thermal resistance decreases extraordinarily if PASP is added in the solution. Supported by the Special Funds for Major State Basic Research Projects of China (Grant No. 2007CB206904), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (Grant No. 00084)