Author Archives: admin

CR Clean Air High Energy Jet Venturi Fume Scrubbers

High Energy Jet Venturi Fume Scrubbers

In 1917 Croll Reynolds began manufacturing vacuum steam ejectors. Starting in the 1950’s this jet venturi design was adapted for use in pollution control. With the passage of the clean air act in the 1970’s, CR developed a high-energy design which could efficiently remove particulate matter.

CR Clean Air’s high energy venturis are so termed because they use the energy from a high velocity gas stream to atomize a liquid stream. The venturis spray nozzles, oriented perpendicular to the gas flow, are specially designed for maximum performance. The high atomization of the liquid and the extreme turbulence in the venturi throat entrain the solid particulate in the liquid phase, resulting in a unit with low utility consumption and maximum performance, and give this scrubber its exceptionally high ability to remove both micron and sub-micron dust particles. These nozzles can handle a wide range of situations, including slurries and can be easily removed and replaced when needed.

High Energy VenturiOur high energy scrubbers are available with a fixed throat design for specific gas flow, or an optional variable throat design which can be adjusted to fluctuating operating conditions. In most applications, a fixed throat venturi is preferable because of its lower initial cost and reduced maintenance due the lack of moving parts.

Variable throat designs, which can be either manual or automated, are typically only utilized for situations where high turndown is required. Our process engineering experts can guide you as to which design will be best suited to meet your requirement.

The gas from the venturi section is normally discharged into a cyclonic separator tank. A spin is imparted as the gas enters the separator so that the liquid is driven to the outside wall via the rotational motion of the gas. The liquid is then collected and returned to the sump where it can be recycled.

At the top of the separator tank, a mist eliminator, typically a Chevron blade type, is ·used to ensure minimal liquid entrainment in the effluent gas, and thus the highest removal efficiency possible. This separator / mist eliminator design is particularly well suited to variable gas flows since it is effective over a wide range of operating conditions.

CR Clean Air custom engineers all of its products to ensure that the equipment is optimized for your plant’s needs. We can provide the jets in either a vertical or horizontal orientation depending on the space available at your location. Our rigorous quality and attention to detail help set us apart. If it has to work, the first time and every time, you can trust CR Clean Air High Energy Jet Venturis.

Performance: For maximum efficiency, it is important that the venturi and corresponding tank be carefully sized for the specific application. Here are some of the reasons it is important to let our specialists help you select the High Energy Scrubber you need:

1 – Particulate Loading – There is a ‘sweet spot” where a high energy venturi will work the best. Too much particulate, and the unit becomes overwhelmed.

Too few particles, and the odds of them “slipping through” particularly with smaller particulate. The ideal particulate loading is a function of both jet size and particle size, but historically 0.4 gr/ft3 (915 mg/m3) of gas flow is optimal for most applications.

2 – Particle Size Distribution – The smaller the particle, the harder it is to entrain. If you have a particle distribution summary, that will help us ensure that from the largest particles to the smallest, the design is optimized as much as possible. All of our venturis will capture 99% of particles larger than 10 micron excepting very heavy particulate loadings. For 10 to 1 micron the amount of capture is 99% except for very lower pressure drop units. For the specific removal in the sub-micron range, our application specialists can apply their property models to determine the exact removal you can expect.

3 – Fixed vs. Variable Throat – For applications where variation in gas flow rate requires throat velocity compensation in order to maintain a specified scrubbing efficiency, CR Clean Air offers variable throat designs.

For small to moderate changes in flow, variable throats are not necessary.

Even when operating ± 20% from the design condition, overall removal rates can be held for a given particle size. This is true because at higher liquid to gas ratios the efficiency increases for a given velocity through the throat. The slightly lower velocity through the throat is compensated by the slightly higher liquid to gas ratio so that the net effect is no difference in performance.

Where higher variations are anticipated, a variable throat is essential. Available with either automatic or manual control, the automatic throat is used where flow conditions vary widely and frequent adjustments are required. For situations where only occasional variations occur, such as during an upset condition, the manually controlled throat is generally sufficient.

3 – Once-through vs. Recirculating – Although the majority of our systems recirculate the scrubbing liquid, for small liquid flow rates or high particulate loadings, it often is more beneficial to use a non-recirculating (“once-though”) system. Thankfully, because the nozzles are specifically designed to prevent plugging, high concentrations of solids (up to 20 wt%) can be handled without difficulty – making the once through system less common than they once were.

4 – Systems Components – A CR Clean Air High Energy scrubber is available as individual unit (jet only) for incorporation in your own design or as a complete package systems, including recirculation pumps vales, instruments and controls. From the basic to the complex, we will be there every step of the way to assist you in designing a customized solution to meet your process objectives.

Ease of maintenance: Excepting the variable throat design, the CR Clean Air High Energy Scrubber has no moving parts thus maintenance is minimal. It is recommended that the unit is inspected during normal plant shutdowns. Particular attention should be paid to the spray nozzle, which will wear over time and in some cases, may become clogged. Additionally, the body should also be checked for signs erosion particularly the throat section where the highest velocity occurs. The corresponding separator tank rarely needs maintenance, although the mist eliminator should be given a visual inspection periodically.

It is always advisable to have a spare spray nozzle on hand, since these are custom designed and not a stock item. Most of our clients also keep a spare set of gaskets on hand, and some go as far as to have a spare mist eliminator for the separator tank. Thankfully most of our installations go years, sometimes decades, without any need for service or replacement parts.

 Materials of construction: Given the severe conditions our equipment is typically placed under, material selection is of primary importance. We fabricate out of a wide range of materials, both metallic and non-metallic. From fiberglass reinforced plastics (FRP) to exotic alloys and everything in between we have the capability to supply what you require.

For most low temperature service, FRP is common. We can also fabricate in CPVC, PVDF, polypropylene, HPDE and even offer dual laminates. Metallic options include Carbon steel, stainless steel, duplex stainless, as well Incoloy or Hasteloy alloys. Other alloys are available should your application require it. Additionally, we can offer units with a suitable lining such as rubber or Teflon when necessary.

We work with our clients to identify the material that will offer an appropriate blend of service life vs. initial cost. Given that transient process parameters, from a spike in temperature during an upset, to an otherwise minor component in the gas flow may alter the resistance of materials to attack, your own experience with other equipment in similar service, or the upstream material is often the best guide. When this previous experience is not available we can draw on our extensive case history file to determine what will, and more importantly will not, stand the test of time.

Corporate Brochure

Contact us


NOx Reduction Via Wet Scrubbing

CR Clean Air Two-stage NOx Scrubber

CR Clean Air Two-stage NOx Scrubber

Hello I’m looking to remove NOx….. that’s usually how the conversation starts. Often, the process engineer or plant manager doesn’t have much more information available during the initial discussion.

This is unfortunate, as NOx scrubbers have many configurations depending on the exact gas composition and scrubbing liquids to be used. Over the years we’ve learned the proper questions to ask in order to ensure that the end result is a system that will meet the reduction needs in a cost efficient manner. There are many ways in which NOx can be chemically treated – each having its advantages and its drawbacks.

NOx refers to both the NO and NO2 contained in exhaust gases – the byproduct of a combustion process such as vent gas from a boiler.   Nitrous Oxide (NO) is a colorless gas and is only sparingly soluble in water. NO is inherently difficult to scrub, and can generally only be removed by use of a strong oxidizing agent.

Nitrogen Dioxide (NO2) is orange in appearance, ranging from a reddish orange to almost brown depending on the amount of NO2 present and the gas temperature. It is moderately soluble in water, and can be converted to N2 by use of an appropriate reducing agent.

When designing a NOx mitigation system, the ratio of NO to NO2 has an impact on the optimal design approach. For NO heavy systems, a two stage solution is employed. In the first stage NO is oxidized to NO2. Strong oxidizers are preferable, treatment options include Ozone (O3) injection or Sodium Chlorite, NaClO2. The use of Sodium Chlorite is more cost effective as ozone generation systems are historically cost prohibitive.

For NaClO2 based systems, the NO is oxidized in the presence of an acid to NO2 as follows:

10 NO + 2 H2SO4 + 5 NaClO2 →10 NO2 + 2 Na2SO4
+ NaCl + 4 HCL

Of course, some clients are hesitant to utilize such a strong chemicals to treat their NO. Thankfully, other chemistries can be utilized under certain conditions. Two alternatives are Hydrogen Peroxide (H2O2) and Sodium Hydroxide (NaOH).

For either of these alternatives to be practical, there needs to be some NO2 present in addition to the NO. Ideally the NO2: NO molar ratio should be 1:1 or greater, since the NO and NO2 react in equal proportion, as follows:

NO + NO2 + 2 H2O2 → 2 HNO3 + H2O
for hydrogen peroxide
NO + NO2 + 2 NaOH → 2 NaNO2 + H2O
for caustic.

It should be noted that of these two options, with regards to dispositioning the wastewater, many facilities find it easier to deal with the nitric acid (HNO3) than the sodium nitrates (NaNO3).

Additionally, hydrogen peroxide systems require smaller towers than caustic systems. This is due to the both lower L/G ratio needed and lower resonance time required in order to ensure full scrubbing.

In summary, given the various ways in which NOx can be treated, it’s best if you let a CR Clean Air process expert put their knowledge to work for you!

Let Us Know What You Think:
We hope this newsletter will provide timely and helpful information to our customers.
Please let us know if there are topics that you would like to see us cover in future issues.

Download our brochure
Contact our sales department


Spare Parts – How to keep Your system Up and Running

Although CR scrubbing systems need very little maintenance to keep them in optimal running condition, they are not maintenance free. Just like a vehicle needs its oil changed and tires rotated periodically, scrubbers need parts replaced from time to time.

Spray Nozzle

Spray Nozzle

All scrubbers, be them a jet venturi, high energy venturi or packed tower, will need their spray nozzles replaced periodically. How frequently replacement is needed depends on the nature of the fluid. Some systems last decades between replacements, others need to be changed out more regularly.

The best way to tell if a nozzle needs replacement is to compare the observed flow rate to what the system was designed for. Too little flow indicates possible plugging of a fouling, and system capacity will drop as a result. Too high of a flow indicates excessive wear, and leads to an unnecessary increase in pumping power and utility use.

Given that our nozzles are made to order, it is better to have a set on hand, rather than wait until right before a scheduled shutdown. A spare set of gaskets is also advisable, in order to ensure that the equipment seals correctly when it is reassembled.

Fresh Mist_Eliminator

Mesh Mist Eliminator

For high energy systems and packed towers, as well as jet / separator tank systems, the mist eliminator element will also need periodic replacement. Although for situations where excessive fouling can be anticipated in advance, wash down nozzles can be integrated into the design, the mist eliminators, particularly the mesh pad designs, do need periodic replacement to ensure optimal liquid removal. Often the first sign of an excessively fouled mist eliminator is an increase in pressure drop through the scrubber.

Tower Packing

Tower Packing

Finally, for the packed towers the packing will need to be periodically replaced. As with mist eliminators, excessive fouling is usually the best indicator that replacement is advisable. Given that each tower is designed with a specific packing size and type to suit the application, its best to contact CR Clean Air for replacement packing as this will ensure that the performance characteristics, including pollutant removal rate and pressure drop, are consistent with the original system design.

Download our brochure
Contact our sales department

CR Clean Air Jet Venturi, Separator Tank and Packed Tower plus Fiber Bed Mist Eliminator

CR Clean Air Jet Venturi, Separator Tank and Packed Tower plus Fiber Bed Mist Eliminator



Ethylene Oxide Scrubbing Systems

The CR Clean Air Group, LLC’s ETO Scrubbing system is ideal for meeting your emission regulations no matter what the source. From tank farms to sterilizers, we can reduce your Ethylene Oxide (ETO) emission to < 1 ppm!

Our approach compose of three major components: high efficiency packed column(s), a reactor tank and solution feed tank.

First, ETO laden gas is absorbed into the liquid phase by use our high density packing which provides an optimal volume to surface area ratio.

Next, this absorbed ETO is converted to Ethylene Glycol (EG) in the reactor tank. The addition of an acid catalyst to the scrubbing loop minimizes the overall tank size required, which is designed ensure maximum conversion of ETO to EG.

The liquid leaving the reactor tank, being a being virtual EO free, can be recycled through a heat exchanger back to the packed tower. As EO is absorbed and converted, the volume of liquid being recirculated will necessarily increase. For this reason our systems use a solution feed tank.

This tank allows sufficient capacity for the liquid level to swell over time, enabling the system to run continuously, with virtually no waste streams. Further, since the byproduct of the EO conversion is high quality Ethylene Glycol, many of our customers either reuse or sell this valuable byproduct.

We have a wide range of designs available, from simple systems to full automation. We custom engineer each system in accordance with your requirements. Let us put our expertise to work for you!

To get a quote
Download our corporate brochure

The CR Clean Air Group Team:
Gregory D. MacLeod, P.E. SALES MANAGER


Wet Scrubber Solutions from the CR Clean Air Group, LLC

The Clean Air Group, LLC offers a complete line of scrubbers and packed towers. The CR Clean Air brand of venturi scrubber and packed towers are commonly utilized to treat plant effluent to guard against release of such toxic substances as HCL, chlorine, ammonia, Ethylene Oxide (ETO) and NOx, and can also recapture valuable byproducts, such as organic solvents and particulates.

The Clean Air Group, LLC has been involved in the design and manufacture of scrubbers for over 40 years. Our equipment is found in the Power, Chemical, Petrochemical and Paper industries, as well as Food, Pharmaceutical and Textile industries.

Download our corporate brochure

The following is a series of mini‐case histories representative of our experience:

The emergency plan at a specialty chemical plant located in the Midwest relies on aThe Clean Air Group, LLC Packed Tower. In the unlikely event of a catastrophic release of ammonia from the plant’s refrigeration system due to an unexpected rupture, our once‐through tower would remove ammonia at an efficiency of 99% for a single valve release, and well over 90% over the entire range of operation.


Wet-ScrubbersA local chemical provider has never had a serious spill of phosphorus oxychloride (POC13), but its dedicated unloading facility is prepared for the worst case scenario. The stand-by emergency scrubbing protocol relies on a two-stageThe Clean Air Group, LLC system consisting of a 1st stage jet venturifume scrubber followed by a 2nd stage counter current packed tower to handle both POC13 and HCL emissions.

Speaking of HCL, we have a long history in providing HCL emission control systems to meet regulatory requirements while recovering byproduct for sale. This schematic below shows venturis and a heat exchanger for HCL recovery, as well as packed towers for tail gas scrubbing. Overall emissions from this system are typically 2 ppm or less.


In a tightened economy, it’s more important than ever to specify a pollution control system that serves your precise needs with the removal rate your local regulations demand. Overdesign increases purchase price and operating costs… under design results in an inadequate system, not capable of doing the job you require and possibly incurring fines for non‐performance.

The Clean Air Group, LLC ’s application engineers have years of experience in designing and optimizing units and systems. We do not deal in “standard” off‐the‐shelf models that “come close” to meeting the customer’s needs.

The Clean Air Group, LLC quotes systems with the highest efficiency and custom designs every order to meet each customers unique needs. Energy efficient solutions are inherit in CR’s design approach, and our proprietary software allows us to respond quickly and efficiently to even the most demanding application. We have over 40 years’ experience in the design and supply of a wide range of pollution control solutions.

To get a quote

The CR Clean Air Group, LLC’s Team:
Gregory D. MacLeod, P.E. SALES MANAGER


Our Scrubbing Technologies

JET VENTURI SCRUBBER: Motivating fluid through propietary design. The Jet Venturi Scrubber utilizes a liquid motivated ejector design to entrain contaminated gases, generally without the need for a blower. The relatively high liquid-to-gas ratio, liquid atomization, and open internal design provide effective scrubbing of heavily contaminated gases with minimal maintenance and virtually unlimited turndown capabilities. Its ability to handle wide ranging conditions makes the Jet Venturi one of the most flexible designs available. It is often used as a first stage in a multi-stage air pollution control system.

PACKED TOWER SCRUBBER: Utilizing the most modern packing designs to provide contact between gas and liquid streams, the Packed Tower Scrubber achieves the extremely low toxic gas discharge limits required to meet emission standards.

HIGH ENERGY VENTURI SCRUBBER: Energy from a high-velocity dust laden gas stream is used to atomize a liquid stream and to generate cyclonic gas flow in the separator.

Download our brochure

Problem Solved: Jet-Venturi Scrubber System Cleans Hydrochloric Acid (HCI) Fumes

Jet_Venturi_ScrubberA CR CleanAir two-stage Jet-Venturi scrubber/packed tower system solved a number of hydrochloric acid (HCI) pollution problems for an Albany, Oregon, electronics company.

The Zirconium Extraction Div. of Teledyne Wah Chang produces high-quality reactor-grade zirconium and hafnium ozide using a chemical separation process, which produces silicon tetrachloride (SiCI4) as a byproduct.

This crude inorganic chemical is stored in a tank farm, processed into pure SiCI4 , and sold as a raw material to other chemical processors. As it comes into contact with moisture, the silicon tetrachloride generates hydrochloric acid (HCI) fumes.

EPA required the elimination of fugitive emissions. And the plant also needed a scrubber system to protect tank farm workers from potentially hazardous fumes that might escape.

A two-stage system-Model 18 x 18-66V Jet-Venturi Fume Scrubber/Separator unit and 48T-12H Packed Tower-from the Clean Air Group were selected for three reasons.

  • It could handle the sticky gel formed when silicon tetrachloride decomposed in water
  • It has a high liquid-to-gas ration that provides efficient gas scrubbing of HCI
  • Any HCI that may escape is easily scrubbed by the packed tower.

For the second stage of the process, a scrubber material in the packed tower handles residual low concentrations of SiCI4 and HCI. It channels the gas flow upward, through a packed bed; the scrubbing liquid flows down by gravity over the packing.

The packing material had to be selected carefully to prevent solids plugging. Molded polypropylene loops, called Spiral Pac®, were used to obtain a maximum mass transfer area. Liquids and gases come in contact with inside and outside surfaces, preventing gel buildup and providing the high HCI scrubbing capacity.

Full case study here.

Download our corporate brochure


CR Clean Air High Energy Venturi Fume Scrubbers

The CR Clean Air Group’s High Energy (HE) Venturi Fume Scrubbers use energy from a high velocity gas stream to atomize a liquid stream.

This venturi fume scrubber is particularly well suited to collecting smaller particles where standard Jet Venturi scrubbers or similar systems are ineffective for the amount of energy required.

The High Energy Venturi Fume scrubber is designed without moving parts for long-term service and thus requires little or no maintenance,

The High Energy Ventury Fume Scrubbers are available with a fixed throat design for a specific gas flow, or with a variable throat design which can be adjusted to fluctuating operating conditions.

The High Energy Ventury Fume Scrubbersre either of simple construction, using a fixed throat designed for a specific gas flow; or they can have a variable throat design which can be adjusted to the operating conditions.

The High Energy Ventury Fume Scrubbers require little or no maintenance, as there are no internal moving parts to wear or come out of alignment. The liquid is introduced through spray nozzles that can be easily removed through the flanges provided. The use of spray nozzles allows the Venturi scrubber to be installed horizontally as well as in the conventional vertical position.

Download our corporate brochure

Contact Us

High_Energy_Venturi_Scrubbers High_Energy_Venturi_Scrubbers