CBA2 Liquid Ring Vacuum Compressor for High-Capacity, Low-Pressure Gas Duties

Some gas duties are about volume rather than pressure. A vent header, a filter station or a recovery unit may need hundreds of cubic metres per minute moved from vacuum or near-atmospheric suction to a modest positive pressure. The gas is often wet, vapour-laden, or corrosive.

This is the job of a liquid ring vacuum compressor. The CBA2 liquid ring vacuum compressor from Kenflo covers 0.5 to 1,400 m³/min at a discharge pressure of 0 to 0.25 MPa(G), about 2.5 bar(g). It is built for high capacity at medium and low discharge pressure, and it sits alongside the higher-pressure CBK model in Kenflo’s liquid ring compressor range.

This article explains what a vacuum compressor does, the design features behind the CBA2, its material options, and the process duties where Kenflo’s liquid ring vacuum compressors are used.

What a Liquid Ring Vacuum Compressor Does

The same liquid ring machine can work as a vacuum pump or as a compressor, which is why the industry often calls it a vacuum compressor. On the suction side, it draws gas from below atmospheric pressure. On the discharge side, it delivers that gas at a low positive pressure to a header, a condenser or the next process step.

The ring liquid sets the achievable vacuum. As suction pressure approaches the liquid’s vapour pressure, the liquid begins to flash, and the released vapour takes up capacity. As a general guide, a single-stage machine sealed with water at 15 °C reaches about 0.06 bar absolute when pumping air.

On the compression side, the gas stays in close contact with the ring liquid, which absorbs much of the heat of compression. The process runs close to isothermal and the discharge temperature stays low. Compared with traditional vacuum pumps, this makes the liquid ring machine far more tolerant of wet, dirty and vapour-laden gas.

CBA2 vs CBK at a Glance

The CBA2 moves close to ten times the volume of the CBK, while the CBK reaches almost three times the pressure. When a duty needs more than 0.25 MPa(G), the CBK takes over for high-discharge-pressure service up to 0.7 MPa(G).

Design Features Behind the CBA2

Axial suction and discharge

Gas enters and leaves the CBA2 axially, through ports at the ends of the casing. This gives a direct gas path into and out of the impeller cells, an arrangement well suited to the large volumes the CBA2 is built to move.

Only one rotating part

The impeller assembly is the only moving part. Inside a liquid ring machine, there is no metal-to-metal contact in the compression chamber: the rotating liquid, not sliding vanes or pistons, seals and compresses the gas. With nothing rubbing inside the casing, there are few wear parts, and no lubricating oil contacts the process gas.

Reconfigured wet-end profile for long-term operation

Kenflo has reconfigured the profile of the CBA2’s wet end, the parts in contact with the gas and the ring liquid, for long-term operation. The result is a machine designed to hold its performance through long running periods in continuous process duty.

High energy saving and low maintenance

The CBA2 is designed for high energy saving with low maintenance. In vapour-laden service, there is an added benefit. Vapours that condense at the ring-liquid temperature shrink the volume the compressor must handle, giving a capacity bonus that dry machines cannot use.

Suited to flammable and corrosive process streams

Near-isothermal compression keeps discharge temperatures low, which matters when the gas is flammable. When a non-flammable liquid such as water forms the ring, published tests show that a liquid ring compressor can act as a flame arrester. For corrosive gases, the CBA2 can be built in a wide range of materials, covered in the next section.

Material Options from Cast Iron to Hastelloy

The CBA2 offers the widest material range in Kenflo’s compressor line. Wetted-end parts are available in:

• Standard construction (carbon steel + cast iron)
• SS304, SS304L and SS316L
• Duplex stainless steel
• Titanium alloy
• Hastelloy, and other materials

This range lets you match the machine to the duty instead of over-specifying it. Chlorine service shows the logic. In low-pressure dry chlorine compression sealed with concentrated sulfuric acid, nodular cast iron can serve, because the acid leaves little risk of rust. Wet chlorine, by contrast, calls for titanium. The choice of seal liquid therefore shapes the material choice as much as the gas does.

Typical Duties for Kenflo Liquid Ring Vacuum Compressors

Kenflo lists the following duties for its liquid ring vacuum compressors and complete packages. They fall into five groups.

Vacuum filtration. In PTA vacuum filtration, rotary vacuum filters recover terephthalic acid crystals from the slurry. In benzol-ketone dewaxing, liquid ring machines pull vacuum on rotary drum or disc filters that may hold inert nitrogen and chilled ketone solvent. Both duties combine large gas volumes with vapour and carryover, which liquid ring machines handle well.

Off-gas and vapour recovery. This group covers rubber tail gas compression, solvent recovery, and service in styrene, VAC (vinyl acetate), methanol and glycol production, the polyether industry and wax oil hydrogenation. Because almost any compatible liquid can form the ring, including the solvent being recovered, the machine suits solvent and vapour recovery.

Pressure swing adsorption. In PSA units that regenerate under vacuum, the vacuum compressor lowers the bed pressure so that the adsorbed components desorb. Water ring machines are an established choice for this step.

Acetylene compression in the BCD industry. Acetylene is a feedstock for 1,4-butanediol (BDO) production and is highly explosive. A water-sealed liquid ring compressor keeps the acetylene cool and saturated with water during compression, an arrangement long used for explosive gases.

Ash-sluicing water treatment. Kenflo liquid ring vacuum compressors and complete equipment are also used in ash-sluicing water treatment.

When CBA2 Is Not the Right Choice

• Discharge pressure above 0.25 MPa(G). Move to the CBK for up to 0.7 MPa(G), or to Kenflo’s 2BWX tandem package for an ultimate discharge pressure of 1.3 MPa(G).
• Deeper vacuum than a single stage can reach. A two-stage liquid ring vacuum pump extends the range; with 15 °C water, two-stage machines typically reach about 0.03 bar absolute.

Conclusion

The CBA2 is a high-capacity gas compressor for vacuum and low-pressure duties, moving up to 1,400 m³/min at discharge pressures up to 0.25 MPa(G). Axial porting, a single rotating part, a reworked wet end, and material options from cast iron to Hastelloy make it a dependable low-pressure gas compressor for wet, flammable, and corrosive process streams.

Guangdong Kenflo Pump Co., Ltd. has built pumps since 1954 and supplies complete compression packages, including auxiliary equipment, instrumentation and controls. To confirm whether the CBA2 fits your process, contact the Kenflo engineering team.