Dry-ice blasting

Dry-ice blasting projects solid CO2 pellets or shaved dry ice through a compressed-air nozzle onto a fouled surface. The cleaning action combines mechanical impact, rapid cooling of the deposit and sublimation of the dry ice from solid to gas. Because the blasting medium disappears as CO2 gas, the main waste stream is the removed deposit itself rather than spent grit, water or slurry.

Where it appears

Dry-ice blasting is used during outages on boiler casings, heat-exchanger externals, fan rotors, duct interiors, motors, switchgear, moulds and production equipment where added water or abrasive residue would be unacceptable. In power and process plants it is most attractive for localised cleaning around access doors, burners, dampers, inspection ports and surfaces that can tolerate thermal shock but not standing water.

Operating limits

The process needs dry compressed air, good nozzle access and a safe exhaust path for displaced dust and CO2. It is not a deep online cleaning method: crews must enter or work near the equipment, deposits must be reachable, and the unit is normally shut down, cooled and isolated. Very thick slag, sintered ash or chemically bonded scale may require hydroblasting, mechanical tools or explosive cleaning instead.

Safety and maintenance context

The main hazards are flying debris, high noise, cold burns, oxygen displacement in confined spaces, dust inhalation and poor visibility. Confined-space ventilation and gas monitoring are important because CO2 can accumulate at low points. Dry-ice blasting can also chill brittle components and elastomer seals, so cleaning procedures should identify sensitive instruments, gaskets and coatings before work starts.

Position relative to acoustic cleaning

Dry-ice blasting is a corrective offline activity. Sonic horns are preventive online devices intended to keep friable deposits from reaching the stage where an outage crew must remove them manually. On a well-run site the two methods can be complementary: horns extend the operating campaign, while dry-ice blasting cleans local residual deposits during planned access.

Planning notes

A useful dry-ice job starts with access planning. The crew needs nozzle reach, lighting, ventilation, debris collection and a way to protect instruments, refractory edges and soft seals. The site also needs to decide whether dislodged material is ordinary housekeeping dust or a regulated waste stream. Dry-ice blasting can leave equipment visibly clean, but it does not remove root causes such as poor gas distribution, sticky ash chemistry or failed online cleaners. A post-cleaning inspection should record where deposits were thickest so permanent cleaning coverage can be improved.

Practical limits

Dry-ice blasting is useful when a plant needs a dry, low-residue cleaning method around electrical equipment, fan casings, baghouse clean sides or heat-transfer surfaces that cannot be soaked. It still requires outage access, ventilation, oxygen monitoring in confined spaces, hearing protection and a clear plan for dislodged material. The removed deposit does not disappear; ash, corrosion scale or product residue still has to be collected safely.

The method is often chosen for local restoration rather than continuous fouling control. If the same surface blinds or bridges again soon after cleaning, the root cause may be gas temperature, moisture ingress, sticky chemistry, poor ash evacuation or an ineffective online cleaning cycle. Acoustic cleaners can reduce how often dry-ice work is needed when deposits are dry and friable, but they do not replace manual or blasting methods for hardened scale, sinter, refractory damage or oil-bound residue.