Fiber reinforced polymers (FRP by its initials in English) have been used to solve corrosion problems for over 50 years in many industries including chemical processing, mineral processing, pulp and paper and coal power plants. In many applications, fiber reinforced polymers provide superior performance to other building materials. This article shows several instances in which such materials have been used successfully in controlling corrosive environments.
Michael G. Stevens, head of the Scientific Staff of Ashland Inc.
In the early '50s, a central chlor-alkali manufacturing suffered serious corrosion in the heads and heads of their cells. The cells required chlorine replacement in less than a year. In response to this critical need, we developed a new type of polyester resin, based on Chlorendic anhydride. This unsaturated polyester resin chlorinated polyester resin was called Chlorendic. When this material was used together with glass fibers to prepare and heads covered cells, the team's life stretched from 5 to 8 years compared with the original building materials requiring replacement in less than a year. This was the beginning of the use of fiber reinforced polymers (FRP) for corrosion control. Over the next 50 years new materials have been developed for many different applications. Over the years, reinforcing materials also have improved significantly. Innovations in both fields have resulted in a substantially longer life, maintenance free, FRP equipment. The use of FRP resins in various industries will be discussed in this document. This review will provide the reader an overview of where they should be considered FRP materials. The use of FRP also may be more economical in applications that require high-alloy steels or nickel content in stainless steel with a coating or liner. FRPs usually also have lower maintenance requirements compared to the coated steel.
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Wet electrostatic cast zinc epoxy vinyl ester resin made in Spain.
Mineral processing and mining industries
The mining and mineral processing various strong acids used to extract minerals from ores of low quality. The primary acid used in mineral processing is sulfuric acid, which is very corrosive to most metals as well as for concrete. If steel is used for storage tanks or process equipment, should also apply a coating or lining. Most of these coated or lined tanks requires continuous maintenance to keep protected steel. A better option in these applications is to use a team of FRP made with a resin that is resistant to strong acids. The most common resin used for these applications is an epoxy vinyl ester resin bisphenol A. Many pieces of equipment can be manufactured using epoxy vinyl ester resins. These applications include but are not limited to, electrolytic cells, cell extraction, electrowinning, electrostatic precipitators, exhaust fans, ducts, fans, scrubbers, chimneys, inner liners of chimneys, covered with cells, grilles, handrails, storage tanks, sedimentation tanks, pipes, pumps and cooling towers. There are many cases available to support the successful use of epoxy vinyl ester resins for such applications.
Pulp and paper industry
The bleaching process used in making paper is very corrosive. The most common material currently used for paper bleaching is chlorine dioxide. It was discovered that the brominated vinyl ester novolac epoxy resins provide excellent resistance to chlorine dioxide based on trials in paper mills. The types of equipment at a paper mill that can be made of FRP are adequately designed and constructed upstream pipes, towers, tanks, washing drums, drum covers, pipes, scrubbers and hoods. Also available are many cases to demonstrate the feasibility of FRP in these applications.
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FRP Ducts in a power station.
Energy Industry
The energy industry in the U.S. is in the process of installing gas desulfurization units (FGD by its initials in English) in all its coal plants to reduce the amount of acid gases that are emitted by these units. The most effective process to remove these acid gases is the scrubbing system wet FGD. Typically, limestone slurry is used as a means of purification. This will eliminate approximately 99% of sulfur dioxide from flue gas. The debugging environment is highly corrosive to metal, but the scrubbers, limestone slurry pipes, water pipes, ducts and inner liners of chimneys every FRP can be designed and constructed properly. You have to specify the appropriate resin for a long lifetime without maintenance. Other areas in the power plant that can be used in FRP separator gas particles, cooling towers, storage tanks and wiring steps. The FRP has a very competitive cost compared with steel alloys with high nickel content, which otherwise would have to be used in this corrosive environment. The team made of alloys with high nickel content is at least double the cost of FRP equipment comparable. The other option is to use coated or FRP lined steel equipment. Although this is a viable alternative, the maintenance costs tend to be significantly higher for coatings and linings.
Chemical process and oil industry
One of the first uses of FRP was a central chlorine-alkali. We developed a chlorinated polyester resin to withstand the corrosive environment of the cells and covered heads of these. Have also been used epoxy novolac vinyl esters to produce the heads of the cells in chlorine plants. Other areas that can be successfully used FRP components are pipes, storage tanks, gratings and handrails.
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Flue gas scrubber complete FRP (27 x 23.5 meters) with outflow tract in 600 MW power plant on the Ohio River.
The use of FRP has also been expanding in many other chemical processing plants. Some areas are ideal for FRP are those that are present mineral acids and chlorides. The chlorides in water such as salt water or brine are very aggressive to stainless steel. These are ideal applications for FRP, as the team made from isophthalic polyester resin quality corrosion or epoxy vinyl ester resins is almost inert to salt water at temperatures up to 80 ° C (and higher for some resins). These resins have been used for FRP pipes and cooling towers especially when using salt water. Other applications include tanks, reactors, scrubbers, pipes, vents and ducts.
Fiber reinforced polymers provide superior performance to other construction materials
Wastewater Treatment
Facilities wastewater treatment has many applications in the FRP that is currently used. Sodium hypochlorite is currently the preferred material for treating wastewater. The preferred material for storage tanks FRP sodium hypochlorite is constructed from brominated epoxy vinyl ester. When these tanks were manufactured properly, have lasted more than 20 years. The reasons that PKB is the preferred material is primarily its low initial cost, low maintenance costs and long life of the tanks. Other construction materials do not last as long or have a cost of more than double the FRP tank. The odor abatement systems in central wastewater treatment are also made of FRP based on epoxy vinyl ester. Scrubbers, absorption towers, ducts, vents and pipes are all made of FRP.
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Internal Linings FRP chimney.
Keys to a successful application of FRP
To ensure a successful application of FRP is necessary to consider several steps that are key. The first step is to determine if there is an appropriate resin for the service.
The selection of the appropriate resin is very important to a long life. The information required to make the selection of the resin include chemicals used, minimum and maximum concentrations, temperatures, abnormal conditions, requirements and requirements for flame abrasion. With this information, you can select the appropriate resin for the application. Most of the major resin suppliers can help in the selection of the latter through its technical staff consultations or using their published guidelines for selection of resins. The next step is the design of appropriate equipment. This will include the appropriate anti-corrosion lining and construction of the wall structure. The third step is to draft detailed specifications to be followed by the manufacturer and the fourth stage is to make the team. The quality of manufactured equipment is important and must be assessed and approved at an equipment manufacturer based on its ability to meet desired quality requirements in the specification. The next stage is the inspection of equipment manufactured to be performed while being manufactured in transit, once received at the site and prior to commissioning.
Conclusion
The team of FRP has been used successfully to mitigate corrosion in harsh environments since the early 50s. There are many cases which show that the FRP equipment can provide a long useful life. There are many applications where non-alloy steel and stainless steel just can not handle corrosive chemical environments. Currently, many corrosion engineers take into account only if they can find FRP metals appropriate for a given application. In many of these applications, FRP equipment can be used with great success and should be considered as a viable option when searching for material of construction materials for a new team.
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