In the water treatment industry, chlorine disinfection remains the mainstream method. However, chlorine itself is a highly toxic and corrosive gas; a leak in the chlorination room can reach lethal concentrations within minutes. Therefore, any water treatment plant or wastewater treatment facility using chlorine disinfection must be equipped with a reliable chlorine eliminator to neutralize accidentally released chlorine into harmless salts before discharge. Recently, in our company's (Hebei Jiarui FRP Co., Ltd.) production workshop, a batch of Chlorine Scavenger Tanks, specially customized for a Brazilian client, has entered the final winding and assembly stage. After completing hydrostatic testing and internal lining inspection, this batch of equipment will be shipped to the project site in Brazil via Tianjin Port.
Why does the water treatment industry choose GRP tanks as the main body of chlorine eliminators?
The interior of a chlorine eliminator tank is in constant contact with sodium hydroxide solution (concentration typically between 2% and 5%), while intermittently enduring the strong oxidizing effect of hypochlorite. Metallic materials perform poorly under these conditions: carbon steel develops extensive pitting corrosion within months; while 316L stainless steel offers temporary resistance, stress corrosion cracking still occurs in the weld heat-affected zone under chloride ion conditions. In contrast, fiberglass reinforced plastic (GRP) tanks, with their natural chemical inertness and structural design flexibility, are ideal for eliminating the need for a separate tank body. A GRP tank with a vinyl ester resin liner can withstand long-term corrosion from alkali solutions and hypochlorites, and its overall weight is only one-quarter that of a carbon steel tank of the same specifications-a significant advantage for international transport and on-site lifting.
The Chlorine Scavenger Tank produced by our company features an internal Pall ring packing layer and a gas distributor. All internal surfaces in contact with the medium utilize a double-layer lamination process: the inner liner is made of isophthalic unsaturated polyester resin (which has passed a 10% sodium hypochlorite solution immersion test), and the structural layer is formed using alkali-free glass fiber yarn wound on a computer-controlled winding machine. During the factory inspection, the client paid particular attention to the tank's resistance to negative pressure-because elimination tanks in water treatment plants are sometimes accidentally pumped out. Our company demonstrated a pressure-holding test under a specified negative pressure, and the tank showed no obvious deformation or fiber peeling.
Production Site Visit: From Mold Winding to Final Inspection
Walking into our composite materials workshop, you can see this Chlorine Scavenger Tank undergoing its final sanding stage before being coated with an anti-UV topcoat. The production process is roughly as follows: First, a release agent and resin primer are applied to the steel mold; then, the inner lining layer is wound, requiring a resin content of over 85% to ensure density; next is the cross-winding of the structural layers, with fiber tension controlled by a closed-loop sensor, with a deviation not exceeding ±3%; finally, a gel coat layer rich in UV absorbers is wound around the outside of the tank-in most parts of Brazil, the sun is intense, and this layer is crucial to prevent resin aging.
A noteworthy detail is that chlorine neutralization tanks must have multiple process openings pre-drilled in the tank wall: a chlorine inlet pipe, an alkali circulation outlet, a maintenance manhole at the packing support plate, a top vent, and a level gauge interface. Stress concentration at the edges of these openings is a common cause of GRP tank failure. Our approach is to locally reinforce all openings-by wrapping an additional 5-8 layers of fiberglass cloth, and using resin rounding for the opening edges. This is explicitly listed as a mandatory requirement in the technical specifications for the Brazilian project.
Factory Capacity and Similar Project Experience
Our company has the capacity to produce over 200 large fiberglass storage tanks annually, with over 50 GRP tanks for chlorine neutralization already shipped. Compared to metal neutralization tanks, our fiberglass tanks have had zero leakage incidents due to corrosion during five years of post-delivery follow-up visits-this is primarily attributed to the manual lamination process of the inner lining and the control of curing time. Each layer of resin and chopped strand mat is thoroughly compacted with rollers, and after air bubbles are removed, a full 48-hour room temperature curing time is allowed, rather than using heat to accelerate curing.
This Chlorine Scavenger Tank has now completed pinhole discharge testing of the inner lining and ultrasonic thickness measurement of the structural layers. The filler will be added last before packaging. We will also include a detailed installation manual and an air-filled plug for on-site airtightness testing. For the water treatment industry, a reliably operating chlorine eliminator may never go unnoticed by the public-but every second it operates is a precaution against a potential disaster.