Gas Scrubbing from Monmouth Plastics

Monmouth Plastics supplies a range of airborne contaminant control solutions. These solutions prevent uncontrolled release of harmful substances into the atmosphere, and are an effective means of reducing atmospheric pollution caused by industry.

Pollutants removed by the systems we supply may be particulates, gaseous chemicals, or a mixture of the two.

The solutions we provide are tailored to the nature of the contaminant, and the air volume to be treated. We can offer filtration systems, or Gas scrubbers.

Gas Scrubber


Gas Scrubbers are an effective means of removing many types of airborne contamination. There are various designs which are used in different applications, however they all operate on a similar principle – passing contaminated air through a system which encourages contamination to be left behind in a liquid. The liquid acts as a filter capturing the harmful substance, allowing purified air to leave the scrubber. The liquid may then be recirculated back through the scrubber to capture more contaminants. Due to the way scrubbers operate they can handle large concentrations of pollutants continuously, and may offer lower lifetime running costs than filtration systems since there is no need to replace filtration media.

Please feel free to Contact Us for more information or alternatively visit the pages below for details on different gas scrubber types.

Environmental pollution by airborne vapours, gases, fumes, odours and particles is becoming increasingly unacceptable and new government legislation and guidelines are forcing companies to review how and what contaminants they release to atmosphere.

Monmouth Plastics offer many different solutions to the problems associated with gas and vapour discharge. The most conventional and still hugely popular method is packed tower scrubbing…

A packed tower scrubber removes soluble and noxious gases, and mists with droplet sizes greater than 5 µm, from gas streams. Contaminant gases, such as hydrochloric acid, sulphur dioxide and ammonia vapour, are made to flow through a bed packed with media. The media can be plastic, ceramic or stainless steel rings or saddles, designed to provide a high surface area yet allow a high throughput. A scrubbing liquor is pumped through the bed, intimately mixes with the gas stream and dissolves the contaminant gases. Mist droplets impinge on the wetted surfaces of the packing or are captured on in-built mist elimination mesh or plates.

Packed tower scrubbers are not designed to remove particulate material - they tend to become blocked. However, some particulate materials are soluble in scrubbing liquor, and these can be separated effectively.

Packed Tower Gas Scrubber

Packed tower scrubbers are not designed to remove particulate material - they tend to become blocked. However, some particulate materials are soluble in scrubbing liquor, and these can be separated effectively.

The scrubbing liquor is usually passed counter current to the gas stream, but it can flow co-current or crosscurrent. Counter current flows can achieve the highest efficiency of mass transfer but co-current can be more effective if blockages are likely to be a problem. After passing through the packed tower, it may be possible to regenerate the liquor for recycling and reuse. Otherwise, the liquid discharge may have to be treated before disposal.

There are many variations on the packed tower design. For example, in bio scrubbers, micro organisms are cultivated on the surface of the packing to treat gaseous pollutants of organic origin. Although most packed tower scrubbers are tall vertical structures, they can be horizontal for low-profile requirements.

Packed tower scrubbers are used in sewage treatment facilities, metal finishing operations and the paper and chemical industries for the efficient removal of acid gases, odours and mists. Different scrubbing liquors are employed to dissolve, neutralise or oxidise contaminant gases. Water, hydrogen peroxide, caustic soda and ozone gas can all be used to treat particular pollutants. Sulphur dioxide, for example, can be removed with more than 99 % efficiency.

Venturi Gas Scrubber

Venturi scrubbers are among the most effective means of removing submicron particulate material from gas streams. Reactive trace gases can also be removed.

Venturi scrubbers operate by passing either the gas or a scrubbing liquor through a constriction (the Venturi) at high velocity. This creates a high relative velocity between the gas and the liquid, which causes intimate mixing and increases the chances of particles impinging on the scrubbing liquor. The liquid-gas mixture is then passed through a built-in cyclone or baffle plates, where the slurry droplets are collected. The slurry is returned to a sump for recycling or treatment and disposal. Venturi scrubbers are self-cleaning and have no moving internal components.

There are three types of venturi scrubber. In the conventional venturi scrubber, the gas stream is passed through the venturi and the liquor is entrained, whereas in the similar water jet eductor, the scrubbing liquor is passed through the venturi nozzle and the contaminated gas is entrained into the stream of liquor. The self-induced spray scrubber achieves intimate mixing by passing the contaminated gas through a constriction partly submerged in scrubbing liquor. This creates a spray in which particulate material is scrubbed. 


Venturi scrubbers remove particles and liquid droplets larger than 0•1 µm. They are ideal for gas flows containing high particulate levels and are particularly suitable for the collection of inflammable vapours. They are used in the fertiliser, chemical, paper, metalworking and mining industries.

Water jet eductors will remove sticky or gummy particulate material from a gas stream. Self-induced spray scrubbers have a lower operating pressure drop and can be slightly less efficient at particle separation; they are generally not used for trace gas removal.


Venturi scrubbers with high efficiencies of submicron particle removal have relatively high power consumptions and operating costs. A typical venturi scrubber may have a gas flow of about 8000 m3/hour. It would require a 3 kW fan to drive the gas, and a 1 kW pump to recirculate the scrubbing liquor. Self-induced spray scrubbers have slightly lower operating costs.

In some venturi’s the cross sectional area of the throat can be varied to keep the operating pressure drop constant. In this way, a constant efficiency can be maintained in spite of variations in throughput.