THERMOSET EPOXY POLYMER CONCRETE FOR THE FABRICATION OF CHEMICAL CONTAINMENT VESSELS.

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Juliana Cameron
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1 THERMOSET EPOXY POLYMER CONCRETE FOR THE FABRICATION OF CHEMICAL CONTAINMENT VESSELS. PAUL LYNCH, PRESIDENT, CAPPAR LIMITED STEVE LOHNES, TECHNICAL DIRECTOR CAPPAR LIMITED CAPPAR LIMITED 33 SELBY ROAD, BRAMPTON, ONTARIO L6W 1K5 TELEPHONE: PRESENTATION DATE: Presented at a meeting of the Thermoset Resin Formulators Association at the Hyatt Regency Montreal in Montreal, Quebec, Canada, September 11 through 12, This paper is presented by invitation of TRFA. It is publicly distributed upon request by the TRFA to assist in the communication of information and viewpoints relevant to the thermoset industry. The paper and its contents have not been reviewed or evaluated by the TRFA and should not be construed as having been adopted or endorsed by the TRFA.

com PRESENTATION DATE: Presented at a meeting of the Thermoset Resin Formulators Association at the Hyatt Regency Montreal in Montreal, Quebec, Canada, September 11 through 12, 2006.

2 Objectives 1. To produce a maintenance free vessel for containing hot acid electrolyte and anodes/cathodes. 2. To formulate a polymer concrete composite that allows a one step fabrication process. 3. To develop a process that produces a consistent polymer concrete composition throughout the vessel. 4. To provide a consistent strength development of the polymer concrete to allow de-molding and re-use of the molds the following day.

To develop a process that produces a consistent polymer concrete composition throughout the vessel. 4.

3 1. To produce a maintenance free vessel for containing hot acid electrolyte and anodes/cathodes. Current Experience: A. Concrete tanks with liners Damage to liners is common. Acid leaks behind the liner and attacks the concrete. Very high maintenance costs for outages, repair cost to tank and the supporting structures. Serious Health & Safety concerns. B. Vinyl Ester composites Much improved performance compared to traditional concrete and liners. The composite is typically a polymer concrete core sandwiched between polymer rich gel coats 3mms in thickness. The thermal co-efficient of linear expansion (TCLE) for the gel coat is higher than that of the core material by a factor of three. The repeated thermal loading/unloading can lead to cracks in the gel coat, acid penetration to the core and subsequent leakage of the tank. Vinyl ester shrinkage can also put the polymer rich gel coats in tension compared to the core and this also contributes to crack development. 2. To formulate a polymer concrete composite that allows a one step fabrication process Our experience: A. With excellent aggregate shape, quality and grading together with vinyl ester chemistry (well proven in the chemical process industries) we anticipated a one-step process. B. With only 7% Vinyl Ester Polymer by weight we expected the polymerisation shrinkage to be insignificant. The low polymer content also controlled the heat of exotherm during cure and subsequent contraction when cooling. Despite our expectations, cracking during fabrication could not be eliminated in a one step process.

Vinyl Ester composites Much improved performance compared to traditional concrete and liners.

4 C. We abandoned the Vinyl Ester polymer and continued our development with Epoxy chemistry. D. Specific epoxy formulations were formulated, tested and approved for different acid solutions/temperatures. 18% Sulphuric Acid up to 70 C. 14% Hydrofluosilicic Acid up to 45 C. Formulation criteria for Epoxy Polymer 1. Chemical Resistance 2. Temperature Resistance 3. Pot Life Reasonable working time. 4. Ambient temperature cure capability. 5. Determination of an effective heat cure schedule to move past the `B stage cure. 6. Low viscosity of Mixed Resins. 7. Ability to wet out the various grades of silica in the aggregate formulation. 8. High mechanical strength. 9. Zero V.O.C. 10. Affordable Epoxy Resin Component Considerations 1. Viscosity reduction was achieved with a Difunctional diluent which would not introduce a chain stopper, compared to a Monofunctional diluent. This was important to maintain chemical/heat resistance. 2. Non-functional diluents were not used because of high performance specification. 3. Bisphenol A epoxy could be used, however Bisphenol F further assisted viscosity reduction and improved chemical/heat resistance.

Formulation criteria for Epoxy Polymer 1. Chemical Resistance 2. Temperature Resistance 3. Pot Life Reasonable working time. 4. Ambient temperature cure capability. 5.

5 4. Novolac Epoxy was not used due to its very high viscosity. This would adversely affect the design mix and flow characteristics. Curing Component Considerations 1. Primarily aliphatic and cycloaliphatic amines were used. Aromatics were not considered due to health & safety concerns. 2. A modest level of adducting was undertaken to reduce corrosivity and make the material safer to use. 3. Adducting also helped to extend pot life and reduce exotherm temperature. 4. The choice of adduct component had to ensure that mechanical properties were not significantly compromised. 5. Finally the adducting had to be limited to avoid significant viscosity increase. 3. To develop a process that produces a consistent polymer concrete composition throughout the vessel. A. The Epoxy Polymer Concrete composite had to flow, release entrapped air from the mixing process and also remain a consistent design mix during the cure period, with little segregation of Polymer and without developing a high exotherm temperature. B. The Aggregate formula was critical to achieve the proper balance of characteristics with only 7.7% polymer by weight, this in turn also provided a low T.C.L.E. C. The development and fine tuning of this composite was enhanced by specific process controls- temperature of ingredients, pouring freshly mixed materials and introducing vibration during placement. Batch sizes of 750 litres avoided batching errors and allowed fast placement of material. 4. To provide a consistent strength development of the polymer concrete to allow de-molding and re-use of the molds the following day.

A modest level of adducting was undertaken to reduce corrosivity and make the material safer to use. 3. Adducting also helped to extend pot life and reduce exotherm temperature. 4.

6 A. Modest heat curing up to 65 C overnight for 12 hours ensured the Epoxy Polymer Concrete could be easily de-molded with no risk of damage to the product. B. Higher temperature heat curing is not advisable. Heating above the heat distortion temperature of the polymer results in potential distortion during the de-molding and locking within the molds. C. Temperature probes and monitoring overnight confirms the proper heat-cycle has been maintained, before attempting the demolding stage. Independent Testing was undertaken to verify our data Most important was the finite element analysis to model the tanks, taking into account the loading of electrolyte and anodes/cathodes. This coupled with the physical properties of the material allowed maximum stress point locations and potential deflection to be determined. It was re-assuring to note that a :1 margin of safety was concluded from this study. (1) Patent for the new technology Process started in April 1999._ Potential patents with similar technology are searched and examined to contest claims of prior knowledge being used for the patent. Patent scope may be considered too wide. Rewrites and final patent application is completed. Patent must be filed prior to any commercial gain. Patent issued in Canada and in 2001 and in the U.S.A. in (2) Site experiences 1. Automated batching equipment relying on volumetric pumping equipment is not sufficiently accurate with > + 10% variations in A:B ratios and difficulties with the Aggregate dispensing.

Temperature probes and monitoring overnight confirms the proper heat-cycle has been maintained, before attempting the demolding stage.

7 2. Pigmentation of Polymer Concrete prevents the confirmation of consistent mix design throughout the vessel. 3. Batching by weight ensures very accurate and reproducible quality. 4. Store all components at 25 C - 30 C for 48 hours prior to use, to ensure best working viscosities and pot life. (A 3000 lb bulk sack of aggregate is slow to assume the proper temperature.) 5. Controlled heat cure cycle is important. Computer record of this stage ensures it is safe to demold the next day. Demolding without effective cure, can result in product distortion and locking onto the finely engineered molds. Q.C. records are completed for every cell. 6. The condition of the molds must be maintained as new. Any indents must be repaired to maintain a super smooth surface. 7. A build-up of release wax after each mold use, ensures easy and consistent release. The small amount of time invested on this step is very important. 8. Contrary to traditional concrete design, the use of FRP rebar is detrimental to the performance of Epoxy Polymer Concrete. This is because it has a much higher T.C.L.E. (3) and expands upon thermal loading. This has caused the Epoxy Polymer Concrete to crack. (4) 9. Thermal shock-fast and prolonged cooling can cause the cells to crack. If potential exists for thermal shock, then appropriate insulation/protection must be placed at the exposed walls. 10. On site presence during all stages of production is vital to identify and correct the small stuff and fine tune the blueprint for repetitive high quality fabrication. 11. Properly equipped plants with strong Quality Control and Engineering staff will ensure proper records/training and in service evaluation and feed back.

Controlled heat cure cycle is important. Computer record of this stage ensures it is safe to demold the next day.

8 Summary 1. Epoxy Polymer Concrete can be formulated to provide a one step fabrication process and a maintenance free vessel. 2. By the end of 2007, almost 1,000 cells will have been fabricated for Lead and Copper cell house service. 3. The unique silica formulation enables low TCLE, good flow and reliable service through the normal thermal cycling. 4. The results in service coupled with engineering analysis, provides the impetus for future cells to be fabricated with thinner walls to further increase production capacity. References 1. Finite Element Analysis Engineering Reports by Hudu Hydraulics and Engineering Co. Ltd., Fruitvale, B.C. 2. Canadian Patent #2,268,859, US. Patent #6,565, Marshall Industries C-Bar Composite Reinforcing Rod Product Guide Specification. 4. ACI Materials Journal Title No. 98-M36 Effects of Thermal Loads on Concrete Cover of Fiber-Reinforced Polymer Reinforced Elements: Theoretical and Experimental Analysis.

The unique silica formulation enables low TCLE, good flow and reliable service through the normal thermal cycling. 4.

CORROSION ENGINEERING RESIN-BASED POLYMER CONCRETES AND GROUTS

AN ERGONARMOR COMPANY TECHNICAL INFORMATION SPECIFICATION FOR INSTALLATION 07/11 SUPERSEDES 04/00 PAGE 1 OF 6 CORROSION ENGINEERING RESIN-BASED POLYMER CONCRETES AND GROUTS 1. SCOPE 1.1 This specification