New antifoulants for deposit control in MSF and MED plants

New products based on enhanced maleate chemistry have been developed to control the broad range of deposits found in thermal desalination plants. To investigate the performance characteristics of enhanced maleate products, laboratory tests were developed to measure the control of fouling species. The test methods developed for and used in this study provide a further understanding of the key mechanisms of deposit control by additives. The advance performance of products based on enhanced maleate chemistry compared with conventional products currently in use in MSF and MED plants will be presented. Individual product data sets have been combined to produce product performance profiles which can then be used in the selection of additive appropriate to the fouling characteristics of the desalination plant. The enhanced maleates have been successfully tried in both MSF and MED plants. Six months’ data from a 23,000m3/d plant in Saudi Arabia, operated at a top brine temperature of 110°C, will be presented. Also 12- month operational data from an 8000m3/d MED plant in Europe, top brine temperature 62°C, will be presented. The results from these extended field evaluations have confirmed the initial laboratory results.

The laboratory investigation shows that additives vary in performance depending on the type of mechanisms by which they function to control or retard scale formation. The enhanced maleates were found to be superior antifoulants compared to those currently available commercially. The enhanced maleates can be differentiated since EM-1 has all the multi-functional properties required to control deposition and can be used in high-temperature plants. EM-2 has excellent calcium carbonate inhibition and dispersion properties and hence can be used in low-temperature plants. The extended field trials for EM-1 and EM-2 demonstrate their in use scale control performance and confirm the initial laboratory results.