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Development of fouling mitigation methodology at the heat exchanger design stage

Résultats exploitables

The project concerns the development of: -A methodology for optimising the configuration and the design of compact heat exchangers with respect to fouling and for obtaining criteria helpful in selecting heat exchanger type. -Predictive tools for two major classes of applications (cooling water, food products) to assist in taking appropriate measures. -A novel multifunctional computer-aided method for fouling assessment and mitigation For that, several major directions have been investigated and lead to the following information: -Experimental studies on some key aspects of fouling mitigation practices have been performed by UniS, TU-BS, CPERI and GRETh. The effect of use of ion implantation to generate plate heat exchanger surfaces with reduced stickability, evaluation of the adhesive forces between deposit and heat transfer surface, colloidal particle agglomeration and influence of particles on precipitation rate, effect of flow arrangement of the plate heat exchangers have been investigated. -Fouling measurements have been carried out in industrial installations at GRETh and BASF, under carefully controlled conditions, in order to enrich the database on which the proposed new methods have been founded. -For the two systems of major practical significance: cooling water and protein dispersions, the new and available data have been assessed in order to allow improvement of models or development of correlations. -Geometrical configurations of compact heat exchangers (CHE's) less prone to fouling have been identified by numerical simulation of the flow field inside CHE channels by UniS, GRETh, ALT and AlfaLaval Vicarb. -A model fluid, able to describe both rheological and fouling behaviour of an industrial milky dessert have been developed by INRA and DANONE. -A new device, less prone to fouling for dairy products, has been developed, tested and patented by ACTINI. Tests at INRA, based on eggs treatment furnished by DEGUT, have shown a significant improvement in the field of fouling mitigation. -The novel predictive method has been developed by CPERI on the basis of software modules devoted individually to a �fouling data bank, �models/correlations� and �chemistry� calculations. Two main classes of fluids are covered in this project with the following potential benefits: -In the area of food products, fouling mitigation will lead to a significant increase in operating time and hence to increased productivity. For example, a 2 hours increase of operating time corresponds at least to an increase of 10% in productivity. The consumption of water and cleaning agents is reduced by about the same amount. Energy consumption, which is a stronger function of operating time, is even more reduced. In addition, due to better temperature control, the quality of the product and the functionality of the equipment are improved. -Cooling water fouling is an extremely important problem in the chemical processing industry which has been compounded by increasing environmental regulations challenging the usage of water treatment chemicals in open systems and the discharge of water with previously tolerated additive levels from closed systems. At the same time, the supply of cooling water has decreased because of increasing costs, leading to lower cooling water flow velocities and higher outlet temperatures. Both trends increase the tendency of deposits to form on the heat transfer surfaces. In addition to the reduced thermal performance, cooling water fouling tends to increase the corrosion of heat exchangers. Compact heat exchangers can usually be built from more expensive materials because of their smaller heat transfer surface requirements. This increases the life span of equipment. In addition, smaller and lighter heat exchangers require less floor space and support.