The Problem: Sealing Evaporator Dome Lids
Frequently used in the pulp and paper industry, multiple effect evaporators boil water through a sequence of vessels held at increasingly lower pressures. Because a reduction in pressure lowers the boiling temperature of water, only the first vessel in the series requires a heating source.
These types of evaporators are used in the “recovery areas” of pulp mills. Each stage of the evaporating process, called an “effect,” further concentrates what’s known as “black liquor,” a byproduct of the wood pulp digestion process. Multiple effect evaporators condense the black liquor — which contains over half the energy of the raw wood material — so that it can be incinerated and used as a biofuel or recovered for cooking chemicals.
The evaporators’ dome lids, however, are prone to leaking if the gaskets used are unreliable or a poor fit for the application. Evaporator gaskets are often large in diameter with a narrow cross section. To save time separating materials through segmented gaskets, many mills use joint sealant to seal the dome lids. Spreading this joint sealant across the large gaskets for multiple effect evaporators, however, ends up creating opportunities for leaks.
The Solution: Welded Gaskets
To prevent leaks and achieve proper plate evaporator sealing, pulp and paper mills should consider using Durlon® welded gaskets. With increased corrosion and chemical resistance, welded gaskets are able to withstand caustic cleaning agents such as chlorine and nitric acid that are often used to clean equipment.
Welded gaskets are also designed to seal the plate pack under the high operating temperatures and wide range of pressures involved in pulp and paper digestion. To accommodate the boiling water in each evaporator effect, these gaskets can resist temperatures up to 245°F, as well as pressures ranging from 10 psig to full vacuum.
With chemical, corrosion, and extreme temperature resistance, welded gaskets are a reliable choice for withstanding the harsh conditions of the paper and pulp industry, thereby minimizing the risk of leakage for both segmented gaskets and joint sealant.
GRI’s Fluid Sealing Solutions
Gasket Resources Inc. (GRI®) offers high-quality welded gasket solutions for a variety of chemical applications. Below are two of our products designed especially for multiple effect evaporators.
- Durlon® 9000/9000N — Tested and approved for extreme temperatures, caustics, and liquid and gaseous dry-chlorine service, this PTFE model is widely used in the pulp and paper industry.
- Durlon® 9200W — A blend of Barium Sulfate and PTFE makes this model resistant to the aggressive chemicals such as caustics, hydrogen peroxide, sodium hypochlorite, nitric acid, liquors, and digesters used in pulp and paper processes.
To learn more about our large welded gaskets for evaporators, talk to our gasket experts today.