Implementation gap for antifouling coating

© 2016 Elsevier Ltd. All rights reserved. Fouling is a chronic problem in many heat transfer systems and leads to regular cleaning of heat exchangers. Antifouling coatings are one mitigation option: The financial attractiveness of installing a coated exchanger depends on trade-offs between capital and operating costs over the lifetime of the unit. Such considerations effectively set bounds on the price of coatings, bounded by manufacturing costs and the maximum saving that can be achieved from fouling mitigation, in a 'value pricing' calculation. The 'value pricing' concept is considered here, for the first time, for heat exchangers subject to asymptotic fouling. An explicit solution to the cleaning scheduling optimisation problem is presented for the case of equal heat capacity flow rates in a counter-current single phase exchanger. A case study is used to illustrate the concepts and key learnings. A sensitivity analysis identifies scenarios where the use of antifouling coatings may be attractive, and also where there is no financial benefit in cleaning a fouled exchanger.Chemours Belgiu

Comparison of fouling of raw milk and whey protein solution on stainless steel and fluorocarbon coated surfaces: Effects on fouling performance, deposit structure and composition

Fouling from raw milk and from whey protein solutions mimicking the protein content of milk have been performed at two length scales, using a microfluidic heat transfer cell and a bench-scale device with hydraulic diameters 1:0mm and 16:1 mm, respectively. The microfluidic cell allows raw milk to be studied in once-through mode and was used to identify polymer coated surfaces to test against stainless steel. Several of the fluorocarbon coated surfaces reduced the mass deposition but the pressure drop and thermal resistance did not match these directly, indicating that the nature and structure of the deposit is affected by the surface. A fluorinated ethylene propylene coating was identified as a promising candidate for large scale tests. At the interface with apolar surfaces, raw milk fouling layers were high in protein whereas a strongly attached mineral-rich layer was present at the interface with steel. The attraction of denatured protein towards apolar surfaces and the formation of a calcium phosphate layer on steel at later stages of fouling are explained with arguments based on the interfacial free energy of these materials in water.The work was funded by Chemours Belgium BVB

Mitigating fouling of heat exchangers with fluoropolymer coatings

Fouling is a chronic problem in many heat transfer systems and results in the need for frequent heat exchanger (HEX) cleaning. In the dairy industry, the associated operating cost and environmental impact are substantial. Antifouling coatings are one mitigation option. In this work, the fouling behaviour of fluoropolymer, polypropylene and stainless steel heat transfer surfaces in processing raw milk and whey protein solution are studied. Methodologies to assess the economics of antifouling coatings are developed and applied. Two experimental apparatuses were designed and constructed to study fouling at surface temperatures around 90 °C. A microfluidic system with a 650 x 2000 µm flow channel enables fouling studies to be carried out by recirculating 2 l of raw milk. The apparatus operates in the laminar flow regime and the capability to probe the local composition of delicate fouling deposit $\textit{in-situ}$ with histological techniques employing confocal laser scanning microscopy. A larger bench-scale apparatus with a 10 x 42 mm flow channel was built to recirculate 17 l of solution in the turbulent flow regime which is more representative of conditions in an industrial plate HEX. Experimental results demonstrate that fluoropolymer coatings can reduce fouling masses from raw milk and whey protein solution by up to 50 %. Surface properties affect the structure and composition of the deposit. At the interface with apolar surfaces raw milk fouling layers are high in protein, whereas a strongly attached mineral-rich layer is present at the interface with steel. Whey protein deposits generated on apolar surfaces are more spongy and have a lower thermal conductivity and/or density than deposits on steel. The attraction of denatured protein towards apolar surfaces and the formation of a calcium phosphate layer on steel at later stages of fouling are explained with arguments based on the interfacial free energy of these materials in water. The financial attractiveness of coatings is considered for HEX subject to linearly and asymptotically increasing fouling resistance and using a spatially resolved fouling model. An explicit solution to the cleaning-scheduling problem is presented for the case of equal heat capacity flow rates in a counter-current HEX. Scenarios where the use of coatings may be attractive or where there is no financial benefit in cleaning a fouled exchanger are identified. Finally, experimental data are used to estimate the economic potential of fluoropolymer coated HEXs in the ultra-high-temperature treatment of milk. In the considered case, the value of a fluoropolymer coating inferred from the reduction in fouling is estimated to be around 2000 US$/m².The sponsorship of this work by Chemours is appreciated

Adhesion and cleaning of foods with complex structure: Effect of oil content and fluoropolymer coating characteristics on the detachment of cake from baking surfaces

The effect of surface coating on the detachment of a complex microstructured food material, was investigated using an improved version of the millimanipulation device described by Ali et al. (2015 \textit{Food & Bioproducts Processing}, Vol. 93, 256–268). The test material was baked sponge cake batter, which contains approximately 27 vol% bubbles in a ‘continuous’ phase of emulsified oil in a flour/syrup suspension. Detachment in the dry state was studied for aluminium, 304 stainless steel and seven different fluoropolymer coatings. The surfaces differed in surface energy and roughness. The shear force required to detach baked cake, the work done, and the mass of residue remaining on the surface were measured. Virtually all samples detached by cohesive or mixed failure, where adhesion to the surface was stronger than or comparable with cohesive interactions within the cake. The shear force was almost independent of surface composition, energy and roughness, but strongly related to the oil content of the cake. The mass of residue was found to be linearly dependent on the calculated work of adhesion of oil to the surface in an aqueous environment. The quantitative findings are consistent with confocal microscopy images of uncooked batter contacting polar and non-polar surfaces which show very different oil spreading behaviour at the batter-substrate interface. The ability of oil to replace water from a surface is shown to be a key factor determining adhesion of these materials.A Jardine Postgraduate Scholarship for YL from the Jardine Foundation and a PhD studentship for OMM from Du Pont/Chemours and is gratefully acknowledged

ecoOcean - games in Fisheries education, communication and science

There is growing realization of the potential for games and experiments as powerful tools for education, outreach and research in many fields of science. Particularly in fisheries management we face a growing demand for stakeholder involvement, which requires new ways in reaching informed decision making. Games and experiments can be used for (i) teaching economic and ecological principles to pupils, students and the general public, (ii) outreach and communication with stakeholders in participatory assessment or management environments, and (iii) collecting scientific data in controlled research experiments. We developed a conceptual approach and realized the fisheries simulation game ecoOcean. This tool has so far primarily been used for dissemination purposes. The great success of the current version of the game is a strong motivation to proceed on these lines. The game shall be further developed to include a higher complexity and enable the simulation of management measures, i.e. the stakeholder can play through management measures. The paper shall rise awareness of the strengths of this new approach to stakeholder involvement. We will describe past and current approaches and draw a vision on future use of games in education, communication and science, using the conceptual approach we have taken with ecoOcean