Solutions

Alkali Recovery Boiler Deposit & Surface Protection

Use inspection evidence, deposit location, ash chemistry, temperature distribution and safe access to define the maintenance direction.

Application conditions Contact technical team

Operating background

An inspection-led maintenance route for alkali recovery boiler interiors, using deposit distribution, gas-passage restriction and hot-service surface condition to define cleaning, examination and follow-up priorities.

Why the problem develops

Inorganic salts and ash accumulate where gas flow, temperature distribution and surface geometry favour deposition. Restricted passages and persistent deposits can conceal or concentrate local hot-service deterioration.

Application conditions

Industries: Pulp & Paper
Equipment: Recovery boiler · Tube bank · Superheater · Internal gas passage
Main exposure: Recovery-boiler deposits, ash chemistry, hot gas flow, restricted passages and surfaces revealed during a controlled shutdown inspection.
Temperature characteristic: Temperature distribution and thermal history are reviewed as operating evidence; no coating or cleaning decision is based on an assumed uniform boiler temperature.
Operating mode: High-temperature recovery service followed by planned shutdown, access, deposit documentation, cleaning and surface examination.
Primary failure mode: Heavy or uneven deposits, narrowed gas passages, concealed surface attack, local discoloration, roughening or deterioration visible after cleaning.
Application challenge: Securing safe access, preserving evidence before cleaning, distinguishing deposit from substrate damage and examining restricted areas after deposits are removed.

Common signs

Heavy or uneven deposits, narrowed gas passages, concealed surface attack, local discoloration, roughening or deterioration visible after cleaning.

Protection objectives

Map deposit severity and gas-passage restriction before cleaning alters the evidence.
Expose representative surfaces for condition assessment without confusing deposits with substrate loss.
Use inspection findings to prioritize cleaning, further examination and maintenance planning.

Recommended coating system

Solution design principles

Document deposit location, texture and restriction before disturbing the boiler interior.
Select cleaning and examination areas that represent both heavy-deposit and apparently normal zones.
Separate observations from conclusions that require thickness measurement, material testing or specialist boiler assessment.

Surface preparation

Treat deposit removal as an inspection-enabling operation, not as generic coating preparation.
Use a controlled method that exposes the underlying surface without creating damage that could be mistaken for service deterioration.
Mark and photograph the same locations before and after cleaning so the condition record remains traceable.

Key quality controls

Record location, access direction, deposit coverage and gas-passage condition with consistent references.
Compare cleaned and uncleaned representative zones and identify areas requiring further examination.
Keep photographs, observations and any subsequent inspection results linked to the same boiler location map.

Common mistakes

Cleaning the entire accessible area before the original deposit pattern has been documented.
Treating deposit thickness or colour alone as proof of underlying metal condition.
Recommending a surface system before hot-service deterioration and maintenance access have been evaluated.

Inspection, maintenance and repair

Compare deposit and surface maps between planned outages using the same location references.
Prioritize recurring restrictions and locally deteriorated surfaces for more detailed inspection.
Feed confirmed operating and inspection findings into the next cleaning and maintenance plan.

Application workflow

Plan safe outage access

Define inspection zones, access limitations and location references before entering the boiler.

Document deposits in place

Record distribution, severity and restricted passages before cleaning changes the evidence.

Clean representative areas

Expose selected surfaces with a controlled method and retain before-and-after location records.

Assess the revealed condition

Separate residual deposits from visible surface deterioration and identify where further inspection is needed.

Set maintenance priorities

Use the mapped evidence to plan cleaning, examination and follow-up for the next outage cycle.

Suitable scope

Condition assessment and maintenance planning for accessible alkali recovery boiler surfaces during a managed outage.

Use limitations

Visual evidence alone does not establish remaining thickness, material integrity or product suitability. Suspected loss or cracking requires the appropriate engineering and inspection method.

Frequently asked questions

Why should recovery-boiler deposits be documented before cleaning?

Their distribution and the locations of restricted gas passages are operating evidence. Removing them first can erase information needed to select representative inspection areas.

Does a heavy deposit prove that the underlying surface is damaged?

No. Deposit severity and substrate condition must be recorded separately. Cleaning and the appropriate inspection method are needed before drawing conclusions about the surface.

What should an outage inspection record contain?

Use consistent location references for access, deposit coverage, gas-passage restriction, cleaned condition, visible deterioration and any areas referred for further examination.

When is further engineering inspection required?

Suspected cracking, material loss, deformation or uncertain remaining integrity should be referred for the appropriate boiler inspection rather than judged from photographs alone.

DAYU-X

Review the protection approach for your equipment

Describe the equipment, medium, operating temperature and failure signs so the protection direction can be assessed.

Contact technical team