Corrosion Problems with Wet Scrubbers

Corrosion is one of the most challenging and costly issues seen across all markets worldwide. Billions of dollars are spent dealing with the effects and in the prevention of corrosion. Engineers are tasked with the job of designing in such a way that minimizes the effects of corrosion. Luckily there are many high performance materials and systems for engineers to utilize in their efforts to combat the effects of corrosion. Cost and material availability must be weighed against long term performance of a system. Air pollution control engineers must consider the following design criteria when designing wet scrubbing

  1. Technical performance: Does the unit consistently meet the specified air cleaning efficiency?
  2. Reliability: What are its weaknesses and how can we protect against damage or failure?
  3. Outage: How much of an outage can be tolerated without loss and how quickly can the unit be repaired or replaced?
  4. Cost: What is the most cost effective system? Every air scrubber application must be analyzed carefully and technical performance standards must be met.

In many cases today, a whole plant may be forced to shut down if an air pollution control device fails. The engineer selecting an air control device has to make a judgement on how much corrosion can be tolerated and how much of a problem the operator will have in restoring normal operations when corrosion becomes intolerable. Corrosion in a wet scrubber can cause the plastic random packing to become brittle, weaken internals, erode the column shell and damage monitoring equipment. Since we are usually collecting potentially corrosive substances with a wet scrubber, we must be especially careful about the application and selection of materials.

There are many different highly corrosion resistant metals and plastics to consider when selecting materials of construction for a system. These higher performing materials can extend the life of a system but also be very expensive. This trade-off between cost and reliability may cause problems and may lead to a full scale economic analysis to show exactly what is gained from the extra investment in corrosion resistance materials.

Engineers must address several essential questions regarding wet scrubbers and corrosion. First, What affect will corrosive compounds in the scrubbing liquid have on the system and what must be done to assure reliability of service? Secondly, Will the pH of the liquid stabilize at an acceptable point or will it continually drop if nothing is don to correct it? And lastly, Can the liquid be treated with chemicals for removal of devolved gases or can the particulate mater be filtered out? The answers to these questions will have to be found for each scrubber and be incorporated in the design. In effect, all of the components of the system including the piping, pumps, tanks, instrumentation, plastic random packing and internals must be designed for the intended service.

In order to address their customer’s concerns regarding their wet scrubbers and corrosion, KemFlo offers their plastic random packing in a variety of high performance resins. Kemflo’s Tripacks, Pall Rings and Plastic Saddles are offered in Polypropylene, Polypropylene NSF, Polypropylene Glass Filled, Polyvinylchloride PVC, CPVC, Kynar PVDF, Tefzel ETFE, Teflon PFA, and Halar resins. For more information please visit

Water Treatment and Maintenance

Some of the most critical maintenance issues regarding air scrubbers and air strippers are scaling, fouling and disinfection. Scaling is the precipitation and deposition of water-insoluble salts on to column internals and plastic tower packing. Fouling is the formation of deposits other than salts and which may be due to corrosion or biological growth. Disinfection is required if the water is required to be potable or safe for human consumption. It is important that these potential issues are addressed an any maintenance program to help ensure optimal performance from your system.

Scaling can be one of the more complicated maintenance issues to deal with and requires constant attention. In order to prevent scaling the water pH must be adjusted by adding strong acids and bases to prevent salts from building up. It should be noted that the geometry or configuration of plastic random packing has little or no affect in regards to scaling. The rate of scale build-up on column internals is directly related to the water quality. Ammonia and Hydrogen Sulfide are two of the most common water contaminates which require that the water pH be adjusted so that effective air stripping and scrubbing can occur. Ammonia is a weak base while Hydrogen is a weak acid. The hardness and pH of the water must be maintained to prevent scaling problems due to water contaminates such as Ammonia and Hydrogen sulfide.

A maintenance program which includes regular evaluation of the water quality in an air stripping or scrubbing column is the best way to avoid costly shutdowns, repairs or replacements. A proper maintenance and cleaning program should be implemented, which may include acid or caustic washing of the plastic tower packing and internals. Scaling in a column can develop on plastic random packing and other internals like liquid distributors, redistributors, bed limiters or packing supports, requiring these products to be changed out for new ones. Scaling also affects the overall efficiency of a system by restricting flow and reducing liquid gas contact.

Disinfection refers to the elimination of microorganisms typically found in drinking water sources. Some of the more common microorganisms found in drinking water sources include Cryptosporidium, Giardia Lamblia and Legionella. The most common forms of disinfection include chlorination and ozonation which kill organisms by oxidation. UV or Ultraviolet disinfection, which kills organisms with ultraviolet radiation is also fairly common. Chlorination is by far the most common disinfectant in the United States of America. Ozonation is more commonly utilized in Europe.

The importance of developing a proper maintenance plan before an air stripper or scrubber goes into service can not be overstated. Protect the investment you made in your column by reducing or eliminating the affects that scaling and fouling has on plastic tower packing and internals.

KemFlo Pollution Control Products

For over 30 years, KemFlo has been manufacturing high quality injection molded products for the industrial, agricultural, environmental, construction and medical industries. Kemflo offers product design and engineering, prototyping, mold design, mold making and has complete assembly capabilities. All products are subject to Kemflo’s quality assurance process where all parts are evaluated for fit and function, engineering requirements and product validation.

One of Kemflo’s most successful product lines is their plastic random media which is known as Kempac. Kemflo manufacturers this product for a variety of applications such as air scrubbing, air stripping, distillation, biofiltration, absorption, extraction, dehumidification and degasification. This product helps to provide an important stage in a column where gas liquid contact can occur. The performance of plastic random media is dependent on maintaining good liquid and gas distribution throughout the system. This is accomplished through high performance product design which includes a unique network of ribs, drip points and struts which ensures maximum liquid gas contact. The overall design of the column is very important in achieving maximum efficiency. Design considerations include the selection of the type and size of the media, column height, column diameter and internals such as packing supports, bed limiters, mist eliminators, liquid distributors and redistributors. Some things to consider in selecting the most efficient plastic random media for your application include geometric surface area, pressure drop, uniform liquid distribution, uniform gas distribution, operating temperatures and gas / liquid contaminants.

In order to meet their customer’s most demanding requirements Kemflo manufactures Kempac in a spherical or Tripack style, saddle style and ring style plastic random media in three different sizes and multiple resins. Some of the resins available include Polypropylene, Polyethylene, Polypropylene glass filled, Polyvinylchloride, CPVC, Kynar, Teflon and Halar. All resins that Kemflo uses in their manufacturing process are traceable back to the resin supplier as part of their quality assurance program. NSF certified Polypropylene product is also available which meets NSF standard 61 for water treatment plant applications. Other specialty resins are available upon request.

The benefits of utilizing KemFlo’s plastic random media include high active service areas, low pressure drops, high operating capacities, excellent gas and liquid dispersion characteristics, resist nesting and high mass and heat transfer rates. KemFlo customers receive a high performance product at a economical price. Kempac is available in 5 and 10 cubic foot boxes and ships from either our facility in Richmond Hill, Ontario or our warehouse in Houston, Texas.

KemFlo’s primary goal is to provide cost effective product solutions with the highest level of quality for our customers. This is accomplished by using innovative methods supported by a long history of experience and by utilizing the latest technological advancements and sound engineering solutions. For more information on products manufactured by KemFlo please visit our website at or