Wet vs. Dry Industrial Scrubbers for Air Pollution

Choosing between wet and dry industrial scrubbers for air pollution control involves understanding their distinct mechanisms and efficiencies. According to [Westside Group](https://www.westsidegroup.com.au/), wet and dry scrubbers serve the same primary function of removing pollutants from exhaust streams, but they do so using different methods and are effective against different pollutants.

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Wet and dry scrubbers both work to reduce air pollution by treating exhaust gases. However, there are differences between the mechanisms each type of scrubber uses and the pollutants they best neutralize. Choosing which type of scrubber to invest in for your air pollution control requires knowing how these systems work and their pros and cons.

The Difference Between Wet and Dry Scrubbers

Wet Scrubbers

There are a variety of wet scrubbers that remove pollutants from exhaust gases. These different types of wet scrubbers all work by wetting the gas to separate contaminants. Wet scrubbers are highly effective at acid and contaminant removal.

Wet scrubber types differ in how they expose the exhaust gas to the liquid. These variations of wet scrubbers include the following types:

• Packed bed scrubbers
• Venturi scrubbers
• Spray towers
• Cyclone spray chambers
• Orifice scrubbers

For all wet scrubbers, the proportion of exhaust gas to liquid is vital, as it relates to the surface area contact of the gas with the liquid. The pressure and speed of the incoming exhaust gas also influence how well the scrubber works. The scrubbing liquid also determines what the unit removes from the exhaust gas. While water is common as a liquid, caustic scrubbing liquid may be an option for facilities that must remove acids from the exhaust gas.

Dry Scrubbers

Dry scrubbers offer an alternative to wet scrubbers, which require an additional wastewater disposal system. The cost-effectiveness of these scrubbers makes them popular for use in many facilities that need treatment of polluting exhaust gases.

Dry scrubbers do not use wet products to treat the exhaust gas. Instead, these systems use a dry reagent called a sorbent to either neutralize or separate the acids from the gas. As in wet scrubber systems, dry scrubbers need to maximize surface area contact between the sorbent and the gas to remove as much acid from the exhaust as possible. Filters in the system filter out particulate matter the sorbent cannot impact. After the sorbent passes through the gas, it becomes a hazardous material that requires special disposal.

While wet scrubbers perform better at removing more pollutants, the extra weight and disposal of the wastewater from them increases their operating costs. Dry scrubbers provide a lower-maintenance alternative thanks to their lighter-weight powder waste.

How Do Dry Scrubbers Work?

Step-by-Step Process

Dry scrubbers have a three-step process to remove acids from exhaust gases. By taking out these pollutants, dry scrubbers can reduce the incidence of acid rain and lower harmful air pollution levels.

• Step 1 – The first step requires cooling the exhaust gases to make treating the pollutants easier. Typically, an evaporative cooling unit cools and dilutes the exhaust gas during this stage.
• Step 2 – The next stage exposes the gas to a combination of alkaline reagents in the sorbent mixture. Usually, sorbents are either hydrated lime, sodium sesquicarbonate or sodium bicarbonate, or a mixture of them. This process can occur in one of two ways, depending on the structure of the dry scrubber.
• Step 3 – The third step filters out the pollutant-containing powder through a fabric filter or with an electrostatic precipitator. The former is highly effective and does not require power for operation. The latter can effectively remove particulate matter, too – however, it may use up to 4% of a power facility’s output to maintain its electrostatic charge. Due to the difficulty of cleaning the waste powder to remove pollutants, most plants discard it.

How Do You Choose the Right Scrubber for Your Needs?

Advantages of Wet Scrubbers

Wet scrubbers have several advantages for their use – most notably, their ability to process out more pollutants compared to dry scrubbers. Plus, they reduce fire hazards by keeping flammable pollutants wet inside the tower. These scrubbers are also the only means of pollution control that remove both particulate matter and gases from the exhaust in the same process. Different types of wet scrubbers will perform at varying levels when processing out both particulate and gaseous materials. For instance, spray towers don’t operate as well at removing particulate matter as Venturi scrubbers.

Disadvantages of Wet Scrubbers

The most significant downside to wet scrubbers is the need to dispose of the liquid waste from them. Due to pollutant contamination of this liquid, it requires treatment before disposal. Additionally, wet scrubbers can experience corrosion and require regular maintenance to keep them operating at peak efficiency.

Advantages of Dry Scrubbers

Dry scrubbers work well to remove sulfur dioxide and hydrochloride. They have lower use costs because the waste they produce does not require additional treatment and weighs less than the wastewater from wet scrubbers. For existing facilities that require additional exhaust processing, dry scrubbers require less space. In some cases, you can even retrofit them into existing areas. For removing particulate matter, fabric filters work very efficiently with dry scrubbers. Plus, these models have very low maintenance costs.

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Disadvantages of Dry Scrubbers

Dry scrubbers are not ideal for all facilities. The greatest disadvantage to these scrubbers is their inability to remove all pollutants. Plus, they do not remove as many acids from gases as wet scrubbers. While sufficient, dry scrubbers do not perform as well as wet scrubbers for air pollution control.

Common Applications

Wet Scrubbers

Common uses of wet scrubbers are for facilities that process propane and natural gas. Additionally, any type of facility that requires the removal of particulate matter and treatment of gaseous pollutants in the most thorough manner possible should use wet scrubbers.

Dry Scrubbers

Industrial applications of dry scrubbers include the removal of acids from their exhaust gases. Typically, facilities that lack the space or funds for a separate wastewater treatment system to handle water waste from wet scrubbers benefit most from using dry scrubbers. Therefore, these types of scrubbers find use in most types of plants, including energy production, manufacturing, and waste treatment facilities.

Other Types of Industrial Scrubbers

While wet and dry scrubbers are the two most commonly used types of industrial scrubbers, electrostatic precipitators are another option. Often, this device combines with a dry scrubber to act as a particulate filter. However, it can also work as a standalone scrubber in some applications, with a removal rate of up to 99% of particulate matter from gas.

An electrostatic precipitator (ESP) requires construction and a static charge to match the type of dust or contaminants it removes. The exhaust gas stream passes through perforated discharge plates to control the flow. Discharge electrodes charge the gas with either a positive or negative charge, depending on what particles the system removes. As the charged gas passes by the collection pipe or plate, the charged particles stick to the pipes or plates because the collection surfaces carry an opposite charge. The final step requires cleaning off the collection plates or pipes to prepare them for more processing.

ESPs can remove the collected pollutant with a dry or wet method. The most common method is the dry process which uses a rapper to vibrate the collection plates or pipes to knock off the pollutant. In wet models, water rinses off the particles. Facilities that have sticky particulate matter that may not come off effectively using a rapper benefit more from using a wet ESP.

Disposing of the pollutants removed with ESP depends on the type of particle and what method you use to remove it. For example, dry ESPs that remove particulate matter from coal-fired power plants gather soot and ash, also known as fly ash. In the United States, facilities recycle up to 43% of this fly ash to cut down on greenhouse gases and eliminate disposal problems.

MACH Engineering can design the right wet scrubber for your facility or help you determine if a rental scrubber will better meet your needs. With so many factors at play, the specifics of the wet scrubbers require expert design to achieve the desired results. Trust us at MACH Engineering to assist with design, installation supervision, tower internals, packing and service. Contact us today for more information.

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Fiberglass: History, Characteristics, Types, Forms, and ...

Fiberglass, a composite material made of woven glass fibers bound together by resin, has gained remarkable recognition due to its distinctive qualities. It is the top choice in industries ranging from construction to aerospace for its durability, resistance to corrosion, and lightweight properties.

This article explores the history, key traits, different types, various forms, and exceptional properties of fiberglass. Read on to find out more about this material. 

What Is Fiberglass?

Fiberglass, otherwise known as glass-reinforced plastic (GRP) or glass-fiber-reinforced plastic (GFRP), is a composite material made from extremely fine fibers of glass. These glass fibers are typically woven into a fabric-like mat or used as a reinforcement material in a plastic resin matrix. The resulting composite material combines the strength and durability of glass with the flexibility and moldability of plastic.

What Is the History of Fiberglass?

The history of fiberglass begins with ancient civilizations like the Phoenicians and Egyptians, who first experimented with glass fibers for decorative purposes. However, these early endeavors were limited in scope, producing only coarse fibers, and the true potential of fiberglass remained unrealized.

Fast forward to the late 19th century; John Player developed a revolutionary process for mass-producing glass strands, primarily for insulation. In 1880, Herman Hammesfahr received a patent for fiberglass cloth interwoven with silk, making it both durable and flame-retardant. These developments laid the foundation for future innovations.

In the 1930s, a chance discovery in Toledo, Ohio, changed the trajectory of fiberglass history. Dale Kleist, a researcher at Owens-Illinois, accidentally created a shower of fine glass fibers while attempting to weld glass blocks. Recognizing the potential of this accidental discovery, engineers refined the process of producing glass fibers efficiently and inexpensively, patenting it in 1933. This marked a crucial turning point, with the first commercially successful glass fiber product—an air filter—hitting the market in 1932.

What Is the Other Term for Fiberglass?

Fiberglass is also called: GRP, short for glass-reinforced plastic or polyester; FRP, which stands for fiber-reinforced plastic; or glass-fiber reinforced plastic (GFRP). The terminology used depends on the location and the industry or sector that uses it. 

How Is Fiberglass Made?

The manufacturing process of fiberglass starts with the careful selection and preparation of raw materials, including: limestone, silica sand, soda ash, and various additives like borax, magnesite, nepheline syenite, feldspar, kaolin clay, and alumina. Waste glass, or cullet, can also be used as raw material. These materials are meticulously measured and mixed together—a step known as batching—before it is introduced into a furnace. The furnace is crucial for melting these raw materials into molten glass, with temperatures reaching around 1,371 °C (2,500 °F). Precise temperature control is maintained to ensure a smooth and continuous flow of molten glass.

The molten glass is directed to various forming processes depending on the desired fiberglass type. Various processes can be used to create fibers, including the direct melt process in which molten glass is formed into fibers straight from the furnace, or the use of glass marbles of roughly 1.6 cm (0.62 in.) in diameter that allows visual inspection for impurities. Examples of these processes include passing molten glass through bushings that are electrically heated and have very small orifices, resulting in fine filaments. A continuous filament process involves winding the filaments at high speed to produce long, continuous fibers. A staple-fiber process rapidly cools the filaments with jets of air, breaking them into shorter lengths. Chopped fiber can be obtained by cutting the long-staple strand into shorter lengths.

What Is the Typical Duration Required to Manufacture Fiberglass?

There is no exact duration required to manufacture fiberglass. The time it will take depends on different factors like: the desired fiberglass type, specific product or application, product complexity, the manufacturing process used, the scale of production, curing time, automation, and finishing operations. Some simple fiberglass products may be manufactured in a matter of hours or days, while more complex items may take several weeks or even months to complete. The specific timeline for a fiberglass manufacturing project should be discussed with a manufacturer, as it depends on the product's unique characteristics and the production facility's capabilities.

What Is the Importance of Fiberglass in the Manufacturing Industry?

The importance of fiberglass in the manufacturing industry lies in its unique blend of properties. Not only is it lightweight, but it is also stronger than most traditional materials. Besides this, it can withstand harsh conditions without warping and buckling. This is why it is implemented in such a wide range of applications, from construction and pool and bath manufacturing to printed circuit boards and sporting equipment.

What Are the Characteristics of Fiberglass?

The main characteristics of fiberglass are as follows:

1. Durable and strong.
2. Stiff.
3. Lightweight.
4. Fire resistant. 
5. Excellent insulation material. 
6. Exceptional chemical resistance.
7. High corrosion resistance.
8. Dimensionally stable material.
9. Insensitive to temperature and humidity changes.
10. Resists warping, bending, distortion, or shrinking.
11. Moisture resistant.

What Is the Color of Fiberglass?

Fiberglass itself is typically whitish, almost colorless, or transparent in color. However, it can be manufactured and coated in various colors depending on the specific application and requirements. The color of fiberglass products can range from white or gray to black or other custom colors, depending on the additives, coatings, or dyes used during the manufacturing process. PTFE-coated fiberglass fabrics, tapes, and belts are commonly tan in color, often referred to as "natural" within the industry.

What Does Fiberglass Look Like?

Fiberglass typically appears as a fine, thread-like material made of glass. It can be in the form of filaments, mats, or woven fabrics, depending on its intended use. The color of fiberglass can vary but is often white or translucent. It may also be coated or treated with other materials, which can affect its appearance. Overall, fiberglass has a fibrous and somewhat translucent appearance.

Contact us to discuss your requirements of underground fiberglass tanks. Our experienced sales team can help you identify the options that best suit your needs.