07 · Acetone Recovery Unit
Where acetone vapour is lost
Acetone is the first solvent on our list of recoverable VOCs for a reason: it is used in large quantities and it evaporates easily, so a great deal of it leaves plants through vents rather than in product. Typical sources are:
- Tray, vacuum and fluid-bed dryers and centrifuges in pharmaceutical and fine-chemical plants
- Reactor and distillation vents during charging, heating and nitrogen purging
- Cellulose acetate, adhesive and coating lines
- Storage-tank breathing and tanker loading
Acetone is inexpensive per litre, but vent losses add up quickly. In the 2004 study below, a single 487 m³/hr vent carrying 123 g/m³ of acetone was losing about ₹185 lakh of solvent a year.
Why acetone is hard on activated carbon
- Heat and fire risk. Ketones such as acetone release a lot of heat when they adsorb on carbon, which can create hot spots and bed fires.
- Batch operation. Carbon beds work in cycles, need at least two beds, steam or vacuum regeneration and periodic carbon replacement.
- Water in the product. Acetone mixes completely with water, so steam-regenerated carbon gives an acetone–water condensate that usually needs distillation before reuse.
Absorption avoids all three: the acetone dissolves into a liquid at ambient temperature, the process runs continuously, and there is no carbon to heat up or replace. See the full comparison of VOC recovery technologies.
How a Genosorb® acetone recovery unit works
- 01
Vent gas enters the absorber
Acetone-laden gas from dryers, reactors or tanks is collected and fed to the absorption column at ambient or below-ambient temperature.
- 02
Genosorb absorbs the acetone
Genosorb 300, the grade made for polar solvents such as ketones, alcohols and esters, dissolves the acetone out of the gas.
- 03
Clean gas leaves
The treated gas is released within its emission limit.
- 04
Acetone is stripped and condensed
The loaded absorbent is heated in a stripper; the acetone vapour that comes off is condensed into liquid acetone.
- 05
Absorbent is recycled
The regenerated Genosorb is cooled and returned to the absorber, with heat exchanged between the hot and cold streams to save energy.
More detail on the absorber, stripper and heat integration is on how Genosorb VOC recovery works.
Operating cost: absorption vs refrigeration vs carbon adsorption
| Technology | Operating cost (₹ per kg recovered) |
|---|---|
| Absorption (Genosorb®) | 2.27 |
| Refrigeration | 5.70 |
| Activated carbon adsorption | 7.47 |
From “VOC recovery from gaseous streams” by Dr D M Mohunta, CCDC (2004). Costs are in 2004 rupees and show how the technologies compare with each other, not today’s prices. Read the original study.
On this stream, absorption cost less than a third as much as carbon adsorption for every kilogram of acetone recovered.
When the acetone concentration is low
Some acetone vents are large and very dilute — tens of thousands of cubic metres an hour at a few hundred ppm. For these, a rotary concentrator is added ahead of the absorber. It raises the concentration up to 30×, so the recovery plant can be a fraction of the size.
What we need to size an acetone recovery unit
- Vent gas flow in m³/hr, its range, and whether it is continuous or batch
- Acetone concentration, and any other solvents in the stream
- Gas temperature, pressure and moisture
- Operating hours per year and what you pay for acetone
- What the recovered acetone will be used for
If you do not have these figures, CCDC can measure your vent losses on site. Start with a feasibility study.
Frequently asked questions
Can recovered acetone be reused in our process?
In most cases, yes. The condensed acetone can go back into the same process, into a less critical step, into equipment cleaning, or be sold. The achievable purity depends on what else is in the vent, and CCDC confirms it in the feasibility study. Pharmaceutical plants should also follow their own quality procedures for reusing recovered solvent.
Is absorption safe for acetone streams?
Absorption takes place in a liquid at ambient temperature, so there are no carbon beds to heat up — the main fire risk when ketones are adsorbed on activated carbon. As with any solvent system, CCDC designs the plant to keep vapour concentrations safely below the lower explosive limit.
What recovery efficiency can an acetone recovery unit achieve?
Genosorb systems are designed for 95–99.9% recovery. The target for each plant is set by its emission limit and the value of the acetone; the 2004 cost study on this page was based on 90% recovery.
Can the same unit handle acetone mixed with other solvents?
Yes. Genosorb absorbs both polar and non-polar solvents, and CCDC’s mobile pilot plant has run on mixtures of up to six solvents at once. The absorbent grade or blend is matched to the mixture.