Stripping columns and absorpti...
Stripping columns and absorption columns look almost identical. Both are tall vessels filled with internals. Inside each, gas and liquid flow past each other in opposite directions. But they do opposite jobs. An absorption column pulls a target component out of a gas and into a liquid solvent. A stripping column drives that same component back out of the liquid and into a gas. This reversal is not just theory. It sets the operating pressure, the temperature, the solvent, and the internals you specify. In most plants—acid gas treating, sour water handling, carbon capture—the two work as a matched pair. This guide shows exactly how they differ in mass transfer direction, operating conditions, and internals. Then it shows when to choose each, and how they team up in a closed loop.
The core difference between a stripping column and an absorption column is the direction of mass transfer. An absorption column transfers a solute from the gas phase into a liquid solvent, while a stripping column reverses this, transferring the solute from the liquid phase back into a gas. They share hardware but operate under opposite thermodynamic conditions.
An absorption column moves a target component from gas into liquid. Gas enters the column, and a liquid solvent captures the solute as they contact across packing or trays. A stripping column runs the reverse. A loaded liquid enters, and steam or a stripping gas drives the solute back into the vapor. Both are tall vessels with countercurrent flow, so they look the same. In each, a solubility gradient drives the transfer—but the gradient points opposite ways.
The two columns are mirror images that almost always work together. An absorption column loads solute into a solvent, turning it from "lean" to "rich." A stripping column then strips that solute out, returning the solvent to its lean state. The lean solvent goes back to the absorber for reuse. Without this step, the plant would burn through fresh solvent nonstop, which costs too much. That is why solvent-based systems pair an absorber with a stripper, also called a regenerator.
Mass transfer direction reverses because the concentration gradient reverses. In absorption, solute concentration is higher in the gas, so it diffuses gas→liquid until equilibrium. In stripping, solute concentration is higher in the liquid, so conditions are shifted to push it liquid→gas. Solubility, set by temperature and pressure, controls the driving force.
The direction reverses because temperature and pressure control solubility. Two-film theory says the transfer resistance sits in thin gas and liquid films at the interface. The solute must cross both films. Solubility rises with pressure and falls with temperature. So higher pressure or lower temperature pushes solute into the liquid. The driving force equals the gap between the operating line and the equilibrium curve. Absorption keeps that line above equilibrium; stripping keeps it below.
Engineers control this driving force through operating conditions. Absorption uses high pressure and low temperature to force solute into the solvent. Stripping uses low pressure and high temperature to release it. A stripping agent then sweeps the freed vapor away. That agent is usually steam, an inert gas, or vapor made inside a reboiler.
Operating conditions are essentially opposite. Absorption columns run at higher pressure and lower temperature to maximize solute solubility in the solvent. Stripping columns run at lower pressure and higher temperature to reduce solubility and release the solute. This reversal in pressure and temperature is the practical fingerprint distinguishing the two units.
Typical operating windows show this reversal in hard numbers. Absorbers run from near-atmospheric up to several tens of bar, depending on the process. The lean solvent enters at about 40°C. Strippers run near 1.5–2 bar at the top. The reboiler stays at or below 120–122°C to stop amine thermal degradation. These opposite targets are the clearest sign of which unit you are looking at.
The liquid-to-gas ratio and energy load also differ sharply. Absorber design usually sets the L/G ratio at 1.2–1.5 times the minimum. This balances solvent flow against pumping cost. Regeneration energy drives operating cost. It runs about 3.5–5 GJ per tonne of CO₂ for MEA-based systems, and advanced setups reach below 3.5. Nearly all of it lands in the stripper reboiler, which supplies the heat to reverse the absorption reaction.
Internals differ mainly in selection priorities, not basic type—both use packing or trays. Absorption columns favor internals that maximize interfacial area at low pressure drop; stripping columns favor internals that tolerate high temperature and vapor loads. In both, structured packing is increasingly preferred for high-capacity, low-pressure-drop mass transfer duty.
Packing-versus-tray choice follows the service conditions. Structured packing gives high surface area, low pressure drop, and strong mass transfer. That suits large gas-volume absorption and regeneration. Trays handle high liquid loads and fouling-prone streams better, since they are easier to clean. Large carbon capture columns default to structured packing because low pressure drop cuts fan and reboiler energy across huge gas volumes. For packing basics, see structured packing.
Supporting internals matter as much as the packing. A liquid distributor controls how evenly solvent spreads across the bed. Poor distribution raises HETP and hurts separation. A mist eliminator at the top stops solvent carryover and loss. Absorbers and strippers set these up differently, since the stripper runs hotter and carries a heavier vapor load.
They are paired because solvent must be reused to be economical. The absorption column captures the solute into solvent, producing a "rich" stream; the stripping column then regenerates that solvent by driving the solute out, returning a "lean" stream to the absorber. This closed loop makes continuous, cost-effective separation possible.
The two columns form a continuous loop around the solvent. Gas enters the absorber, and the solvent leaves the bottom as a rich stream. That rich solvent passes through a lean-rich heat exchanger, which preheats it before the stripper. In the stripper, heat drives the solute out and the solvent turns lean again. The lean solvent returns to the absorber to start over. The heat exchanger recovers energy between the two streams, cutting the reboiler load.
Post-combustion carbon capture is the clearest example of this loop. Flue gas enters the absorber, and an amine solvent captures the CO₂, targeting 90% or higher removal. The rich amine flows to the stripper, where low-pressure steam reverses the reaction and frees the CO₂. The released CO₂ is then purified and compressed for storage or use. Industry case studies at large power plants run exactly this absorber-stripper pair. For the full process, see post-combustion carbon capture.
Each column excels at opposite ends of a separation. Absorption columns offer efficient, low-temperature solute capture but consume solvent and add pumping load. Stripping columns enable solvent regeneration and high solute recovery but carry a heavy thermal energy penalty. Choosing correctly means weighing energy cost against recovery and solvent economics.
Absorption columns have three main strengths. They run at low temperature, work with chemical or physical solvents, and reach high removal rates. The trade-offs are also clear. Solvent make-up adds cost, high L/G ratios raise pumping load, and the column needs a demister to stop carryover. These downsides push most designs toward solvent regeneration rather than single-pass use.
Stripping columns pay off in recovery and reuse. They regenerate the solvent in a closed loop, recover a high fraction of the solute, and can produce a high-purity CO₂ or product stream. The costs are heat and heat damage. Reboiler energy runs 3.5–5 GJ per tonne of CO₂, high temperature risks solvent thermal degradation, and the capital cost is higher. The reboiler is where most of the operating expense sits.
Choose an absorption column when the goal is to remove or recover a component from a gas stream—flue gas cleanup, acid gas treating, gas purification. Choose a stripping column when the goal is to remove a volatile component from a liquid or regenerate a loaded solvent. In most solvent-based plants, you need both.
The feed phase decides the unit. Choose an absorber when the feed is a gas and you need to pull out a pollutant or recover a component—CO₂, H₂S, or VOCs moving into a liquid. Choose a stripper when the feed is a loaded liquid, such as sour water or rich solvent that needs regeneration. Three variables drive the call: feed phase, target purity, and energy budget. Most solvent-based plants need both units in series.
Internals selection follows the column choice. Match structured or random packing to the column diameter and gas volume. Pick the distributor type by the required distribution quality, and the demister type by the carryover risk. Design the column for no more than 70% flooding to hold stable operation. Getting these choices right is where separation performance is won. For selection support, contact our process engineering team.
No. Scrubbing usually means absorption, where a liquid captures a component from a gas. Stripping is the reverse, moving a component from a liquid into a gas, though steam stripping is sometimes loosely called the same thing.
Not at the same time. The hardware looks alike, but the two need opposite pressure and temperature, so plants use two separate columns. A single vessel switching between both roles is rare and only fits special batch cases.
The reboiler must supply heat to generate stripping vapor and reverse the absorption reaction. For MEA-based carbon capture, this regeneration energy runs about 3.5–5 GJ per tonne of CO₂, making it the largest operating cost.
They use the same packing families, but the selection priorities differ. Structured packing works across both because it offers high surface area and low pressure drop, while the stripper version must also handle higher temperature and vapor load.
The absorber captures CO₂ from flue gas into an amine solvent. The stripper then regenerates that solvent and releases the CO₂ for compression, so the two columns form the core of a post-combustion capture plant.
Stripping and absorption columns are two sides of the same separation. The absorber moves a solute from gas into liquid at higher pressure and lower temperature. The stripper reverses that transfer at lower pressure and higher temperature to regenerate the solvent. Their internals share the same families—packing, trays, distributors, demisters—but are specified for opposite priorities. The two rarely work alone. Paired in a closed lean-rich loop, they make continuous, low-cost separation possible, from acid gas treating to post-combustion carbon capture. Getting the split right between the two units, and matching each with the correct internals, directly drives separation efficiency, energy cost, and solvent economics. If you are designing or retrofitting either column, the internals selection is where performance is won or lost.
EN 
CN
EN
RU
AR
JA
DE
FR
ES