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Sulfuric Acid Storage

Custom fiberglass, with its low maintenance, high performance, heat tolerance, and corrosion resistance is a go-to material in many industries for a multitude of applications.  Sure, ‘custom fiberglass’ sounds expensive. The reality of any situation is always more subtle. When considering the entire range of benefits over time, high-quality custom fiberglass that can be formulated to withstand a variety of acids, bases, chlorides, solvents, and oxidizers and outlast other popular materials of construction such as high-priced nickel alloys is a very cost-effective material.

Fiberglass materials formulated from high quality epoxy vinyl ester resins will outperform stainless steel in chemically aggressive environments including Sulfuric Acid.  For example, in dilute form sulfuric acid is known to be extremely corrosive to carbon steel, yet properly formulated fiberglass can provide corrosion resistance.

With respect to operating environment (i.e. concentration, presence of water vapor, pressure, temperature etc.) many design consideration will need to be addressed. For example, while fiberglass is an exceptional material for many acids, concentrations greater than 75% sulfuric acid may not be suitable for all fiberglass materials—sulfuric acid at these concentrations and greater has an affinity for water—a relationship that has been shown to dehydrate or compromise some fiberglass formulations.  Situations involving high concentrations of sulfuric acid and the presence of water must be carefully analyzed.  Similarly, special attention should be provided where situations involve the diluting of acids.

Per contra, diluted sulfuric acid is very aggressive toward cast iron or steel tanks, but can be stored and handled very well in FRP composite equipment. As a general rule of thumb, FRP composite equipment is best suited for concentrations of 70% sulfuric acid and below. At 75% sulfuric acid, the maximum temperature allowed with vinyl ester resins is 100° to 120°F. As the concentration decreases, the allowable temperature limits increase.

Each job will require an understanding of the design elements that underpin a properly operating system. Although there will be unique challenges inherent to any job—a preferred type of FRP composite vessel for storing sulfuric acid is a non-insulated, vertical, above ground tank. Even underground tanks, with the ground acting as an insulator, may have excessive storage temperatures and additional considerations.

Literature such as Myers, Kytomaa and Smith (2007) described fiberglass materials, as well as, other materials of construction (e.g. steel alloys) as being susceptible to Environmental Stress Corrosion Cracking (ESCC) from exposure to acids. This type of literature is useful in many respects, for example, it provides a ‘lessoned learned’ understanding through case studies of how improperly formulated fiberglass resin matrixes and poorly designed fiberglass materials can lead to unintended results.

To be certain, fiberglass isn’t a panacea, and we understand its limitations and thresholds. When you leverage our design expertise, you’ll gain satisfaction knowing that your materials are optimized for performance. Intellectual or scholarly works also press the importance of improving our understanding of complex relationships—a necessity in operating systems combing a wide range design elements and operating conditions.

For fiberglass products to perform properly in the field, it takes more than just quality manufacturing. Excellent performance requires a high level of engineering and design skills coupled with project related expertise –the kind of expertise that only comes from years of experience. Beetles’ engineers have the experience, the skills, and the knowledge to help you with virtually any project related to fiberglass FRP applications.

Sources:
Myers, T. J., Kytömaa, H. K., & Smith, T. R. (2007). Environmental stress-corrosion cracking of fiberglass: Lessons learned from failures in the chemical industry. Journal of hazardous materials, 142(3), 695-704.

Storing Sulfuric Acid Using Fiberglass as a Material of Construction

storing sulfuric acidChoosing the proper material of construction for acid storage is critical to the success of your project and will depend on a number of factors, such as, storage temperature, concentration or purity, tank size, and costs.  By many accounts carbon steel is the most common material of construction for this application. However, there are other options, for example, fiberglass, which has been employed in some of the most chemically aggressive and corrosive environments in a multitude of industries including chemical processing and storage.  With respect to alloys, as materials of construction, stainless steel, anode protection, and or phenolic or glass linings are sometimes utilized, perhaps less frequently, and their use often contingent upon design specifications.

Fiberglass is a unique material that can be utilized effectively for corrosive storage, including sulfuric acid.  When considering the entire portfolio of benefits an end-user may leverage or enjoy when employing fiberglass it becomes clear that there are multi-functional attributes of fiberglass that may increase its cost-effectiveness.  Further, the constructability of custom fiberglass materials imparts multi-functional qualities that are desirable, such as, ease of installation and design synchronization; fiberglass designed to your specifications will interface with existing infrastructure or plant layout.  You’ll want to refer to a resin manufacture guide and or speak with our team of engineers to discuss specifications and design considerations

Perhaps often overlooked in these types of articles is the interdependence between complex operating systems and their functional components or elements of design (tanks, pipe, etc.). Moreover, fiberglass boasts long-life cycles in extremely corrosive environments and it should be considered that there may exist a significant connection between fiberglass and resiliency of the plant or and or operation, and or sustainability of function regarding plant operations. How does a plant or complex system deal with change or a disturbance in flow of day-to-day operations?  Fiberglass may provide some answers to this question by providing a diverse range of positive attributes. Which is to say, there is something worth exploring or potentially redeeming about the notion of adaptability in the context of the materials used, flexibility of the plant, relationships or connections that exist between life-cycles, cost-effectiveness, service life, ease of repair, and importantly—reduced plant down time.

Corrosion resistance is chief among concerns for any firm handling acids or other corrosives such as sulfuric acid. Corrosion resistance of fiberglass is a function both of resin content and the specific resin used in the laminate.  Generally speaking, the higher the resin content, the more corrosion resistant the laminate.  The inherent corrosion resistant characteristic of our fiberglass materials makes it a cost-effective, strong, lightweight solution for corrosion resistant equipment applications in the chemical process industries. The selection of the proper type and thickness of the corrosion barrier/liner can more than double the service life of the material. When storing or handling sulfuric acid, the addition of a corrosion barrier/liner is essential and can become an important cost savings to the end- user, providing the lowest cost per year of service life.

There are few good options for storing sulfuric acid.  Fiberglass is an exceptional material of construction when considering the entire portfolio of benefits is imparts to the end-user, and a highly effective option for the storage of sulfuric acid.  Fiberglass benefits include: high strength-to-weight ratio, can be customized/formulated for corrosion resistance, abrasion resistance, smoke retardance, posses long life-cycles when compared to other materials, ease of repair, and overall durability. 

Corrosion Resistant FRP in Sulphuric Acid Processing Plants

Recently, Ashland Performance Materials put out an interesting white paper about the use of FRP in Sulphuric Acid (H2SO4) processing plants. G. Bruce Garret, John Recar, and Don Kelley’s “Fiberglass Reinforced Plastics Applications in Gas Cleaning Systems of Sulfuric Acid Plants” looks at the benefits of using FRP in sulphuric acid processing plants, rather than other materials like lead-lined steel or brick.

‘The development and application of fiberglass reinforced plastics construction over the last 20 years have made lead and brick-lined equipment a thing of the past for sulphuric acid plant gas cleaning systems.” The low cost of FRP, when compared with other traditional materials, also makes FRP an attractive and cost effective solution.

The two most common types of H2SO4 processing plants are sulfur burning (hot gas design) and metallurgical/spent acid regeneration (cold gas design). In the second type of plant, metallurgical/spent acid regeneration, “by-product SO2 gas from smelter processing sulfides of iron, copper, zinc, lead, nickel, molybdenum, or other metal is used.” This gas contains a number of contaminates and, “If not removed, the contaminants will reduce product acid quality, foul the mist eliminators and catalyst beds, and accelerate corrosion of equipment in the acid plant.” This is where FRP comes in.

Purifying the gas from these plants is a corrosive job and, in the past, the equipment designed to handle these jobs was created from “lead-lined steel with acid-proof or carbon brick added for protection.” However, this material solution left a lot to be desired. In addition to be requiring long construction times, plant down time, and intensive on-going maintenance this solution also posed health hazards.

The introduction and continuing improvements to FRP technology over the last 20 years has made FRP the preferred material solution for gas purifying equipment in H2SO4 processing plants. In addition to natural corrosion resistance, FRP allows for easier maintenance, repairs, and is a lower cost material solution.

The clear advantages of FRP have made FRP the standard material solution for all types of storage and handling equipment in the H2SO4 processing industry.

The Storage of Sulfuric Acid in FRP Composite Tanks

Sulfuric acid (H2SO4) is a chemical that presents unique handling and storage problems. In the higher concentration ranges (96% to 97%), sulfuric acid (66Be’) can be stored in cast iron or carbon steel.  High concentrations of sulphuric acid, however, are very detrimental to FRP composite equipment. At these higher concentrations, sulfuric acid must not come in contact with FRP laminates.

Diluted sulfuric acid, on the other hand, is very aggressive toward cast iron or steel tanks, but can be stored and handled very well in FRP composite equipment. FRP composite equipment is best suited for concentrations of 70% sulfuric acid and below. At 75% sulfuric acid, the maximum temperature allowed with vinyl ester resins is 100° to 120°F. As the concentration decreases, the allowable temperature limits increase.

The procedure for dilution of concentrated sulphuric acid that has worked best in fiberglass composite vessels is as follows:

1. First, add to the storage vessel the entire amount of water required to achieve the desired solution concentration.

2. Then add the concentrated acid slowly into the center of tank by using one of the following suggested fittings:
a) an FRP top nozzle with a PVC flanged down pipe.
b) a PVC coupling and down pipe.
c) a 316 stainless steel coupling with a 316 stainless steel down pipe. The reason the concentrated sulfuric acid is added to the tank center is to prevent concentrated acid from coming in contact with an FRP composite nozzle, or sidewalls of the tank. The concentrated acid should not be allowed to drop onto the liquid surface. Introduce the concentrated sulfuric acid 2” to 3” below the liquid surface. One method of accomplishing this is to create vortex by adding baffles from the bottom of the tank to the height that concentrated acid is first added to the tank. Another alternate method is to extend the down pipe 6” below
the liquid surface.

3. During the dilution process, the mixture must be continually agitated to insure adequate dilution and prevent high concentrations of sulfuric acid from settling and damaging the FRP composite tank. To insure adequate dilution, a rubber-coated agitator, or pumping the tank continuously through a side bottom drain,is required. Circulation through any nozzle on the tank bottom could result in heavy viscous concentrated acid settling to the tank bottom and destroying the FRP composite tank below the nozzle.

4. The dilution of sulfuric acid generates considerable amounts of heat. The temperature of the diluted sulfuric acid must be controlled below 150°F for finished concentrations of 50% or less, and 140°F for 50-70% sulfuric acid solutions. This can be accomplished by regulating the flow rate of concentrated sulfuric acid addition, or by external cooling of the tank contents.

5. The preferred type of FRP composite vessel for storing sulfuric acid is a non-insulated, vertical, above ground tank. Even underground tanks, with the ground acting as an insulator, may have excessive storage temperatures.

6. Sulfuric acid (H2SO4) with trace organic impurities can cause reduced service life of FRP composite laminates.

Contact us today about your fiberglass pipe and fiberglass tank requirements.