To date, many solutions have been developed in the field of drying and cleaning industrial gases from undesirable components and chemical compounds. One of the popular approaches, which have found wide application in a variety of manufacturing areas, is dry gas cleaning (dry scrubbing).

Besides, in the PZGO’s department of chemical research, we individually develop / select unique adsorbents that most accurately correspond to any special tasks in the industrial gas filtration.

Contact us to ask a question or to request a deep consultation

Despite the fact that the number of technologies in this spectrum is quite large, several approaches deserve special attention. The most promising and cost-effective methods of dry air purification today are physical adsorption and catalytic chemisorption.

Of course, there are electrostatic precipitation techniques, photovoltaic methods and even biological approaches, but, as a rule, their efficiency is inversely proportional to the complexity of the design and the requirements for proper operating conditions. Sorption procedures, in this respect, are much more “unpretentious.”

Adsorption towers / columns

In general, adsorption is a special case of absorption. The difference lies in the fact that the wet absorption involves the retention of pollutants in the entire volume (surface and inner) of the scrubbing liquid (solvent), while adsorption captures the undesired inclusions only in the surface interfacial layer of solid bodies (packing bed substrate material for dry gas cleaning).

When it comes to adsorption (unless otherwise indicated), physical adsorption is implied. This means that the interaction of the adsorbent (filter) and the adsorbate (the gas or air media being treated) proceeds at the micromechanical level, without significant formation of new chemical compounds.

^{Industrial high-performance carbon filter (produced at PZGO LLC)}

There should be a reservation. Since ideal conditions are unattainable in a real industrial climate, dry sorption always involves both physical and chemical interaction (in different proportions).

For example, activated carbon (coal briquettes), with respect to organic pollutants, acts as a physical adsorbent, while in contact with gaseous chlorine, it exhibits chemisorption properties.

As for the general design, the adsorption columns are vertical towers of circular or rectangular cross-section with one or several supporting trays on which packing bed material is placed.

In reference to the filter-bed material, in the dry gas filtration stationary substrate is most often used. This is due to the fact that high adsorption properties, as a rule, are manifested by materials that do not have sufficient physical / abrasive strength. However, in some cases it is rational to use devices that implement the principle of a dry fluidized bed.

^{Industrial air purificator of dry-type}

Unlike chemisorption, adsorption is always a reversible process. Due to the reversibility, the captured substance can be separated from the adsorbent by desorption.

Catalytic chemisorption systems

If physical contact is supplemented by chemical interaction, then this phenomenon is called chemisorption.

Dry-type gas cleaning systems that implement this principle of neutralizing harmful or undesirable substances, as a rule, differ only in the chemical composition of the filtering granules.

But if we analyze the cleaning processes at the micro level, we can see that the nature of the filter changes in the process of chemisorption. New chemical bonds arise and, thus, substances with new physical-and-chemical properties are formed on the surface layer of the adsorbent. In contrast to the “classical” adsorption, visible macro-effects are clearly observed during chemisorption: corrosion, cracking, and / or other surface structure changes.

^{2-chamber dry-type adsorption unit for capturing accidental discharge of gasoline vapors. Adsorbers manufactured in PZGO LLC do not reduce the efficiency even at low temperatures and can be installed outdoors}

Both metallic and non-metallic compounds (elements) can be used as filtering bodies in chemisorption apparatus.

^{Granular aluminized adsorbent for efficient catalytic reactions}

In the overwhelming majority of cases such processes take place with the release of heat, therefore chemisorption towers (as well as ancillary equipment and piping / valving) are usually made of heat-resistant structural materials.

Regeneration of adsorbent

A prerequisite for the efficient operation of dry gas cleaning apparatuses is to conduct periodic regeneration – restoration of the activity of an agent.

As the gas phase is cleared of impurities, an inactive surface layer builds up, which prevents the effective capture of the undesirable components. This implies special measures – to restore the activity of the adsorbent.

^{Most commonly used and effective types of adsorbents: left to right – silica gel, activated carbon, natural zeolite}

There are several regeneration methods, and each of them is rational under certain conditions. Sometimes these measures are a part of the desorption process, and sometimes they are simply aimed at clearing the adsorption bodies / tablets / granules from plaque.

We will not dwell on this topic in detail, since it is richerly disclosed on the page devoted to the adsorbers (in our “Articles” section). Suffice it to say that the most common and effective methods of regeneration are steam flushing, calcination, electrostatic impact, and reactivation with air and inert gases.

Felt, fiber and bag filters

The most popular filters for mechanical air cleaning are fiber / fabric / bag filters.

The word “filter” is translated from Latin as “felt“. Indeed, the first filter fabrics were made on the basis of natural felt. Today, there are a great many synthetic and semi-synthetic nonwovens on the market.

Despite the fact that the use of felt and glass fiber in everyday life is extremely wide (exhaust hood, car ventilation, vacuum cleaners), their use for cleaning significant volumes of heavily polluted gas is usually irrational.

^{Nonwoven fiber filter}

However, in large-scale gas cleaning plants and electrostatic precipitators, they sometimes play the role of the final or preparatory aspiration stages and dust collecting lines. For simplicity and convenience, fiber filters (and prefilters) are usually made as replaceable cartridges (cassettes).

^{Types of fibers used in industrial filtration: left to right – felt, corrugated cardboard (accordion), Air-laid paper}

When it comes to technological-scale volumes of thousands of cubic meters per hour, felt and fiber filters cannot cope with this task, quickly clogging up and increasing the pneumohydrodynamic resistance of the system. The same applies to their inability to handle bio-active and high-temperature media as well as explosion- and fire hazardous flows.

^{Compact bag filter produced at PZGO LLC}

Flare gas desulfurization membrane filters

Membrane filters are attributed to a sector-specific class of chemical equipment that selectively captures spot components of a gas stream.

Membrane apparatuses do not have moving parts and function due to the microdisperse structure provided by capillary pores. Filters are made of synthetic materials: nylon, polycarbonate, Teflon, modified cellulose.

The devices show good sulfur oxides absorption, and this makes their use rational in the field of cleaning small volumes of flare gas.

^{On the right in the photo one can see the burning flare gas, which could be cleaned from sulphur compounds using a membrane filter and put into the household needs of the oil platform personnel}

The use of desulfurization membrane filters is in demand in remote areas of oil and gas extraction, where flare gas can be disposed of for minor domestic use (heating of accommodation units, fuel for gas generators and power turbines).

Electrostatic precipitators

Electrostatic phenomena are actively utilized in a variety of household and industrial fields.

In terms of gas cleaning, electrostatic interaction is used both in dust removal and in dry cleaning of streams from gaseous impurities.

The principle of operation of an electrostatic precipitator is based on the attraction of particles having opposite electrical charges. Physical studies conducted on many chemical elements and their compounds, allowed researchers to accurately determine the materials electrical and electronic properties.

^{Compact electrostatic air filter}

As for the design of electrical filters, their main elements are precipitation plates (electrodes), to which a high voltage charge is continuously supplied. Like other gas catchers, electrostatic precipitators require periodic cleaning of the electrodes of the tarnish.

In most cases, the cleaning of the electrodes is carried out by mechanical shaking. However, some manufacturers are experimenting with the pneumatic and magnetic impulse methods.

^{SImple explanation of ESP working principle}

In addition to this, the use of electrostatic precipitators requires the creation of a reliable electrical network, as well as the purchase of related high-voltage equipment.

Equipment reliability index

^{Please note that this rating is based on the ability of the equipment to purify gas from a wide range of gaseous compounds of high chemical and biological activity. Blue color indicates the positions of those types of devices that can be ordered at PZGO LLC.}

Design, manufacture and delivery of dry-type gas cleaning equipment

For any questions regarding the individual design and manufacture of gas cleaning equipment, please contact PZGO LLC in the way that is convenient for you or fill out a questionnaire.

We quickly deliver single adsorption units and complex plants to any city in Europe and Asia. If necessary, we will carry out professional assembling and installation, as well as seamlessly put the equipment into operation, taking into account any technical requirements of the Customer.

PZGO LLC – breathe with ease!