Reliable additives for boiler water, cooling circuits, membrane systems and waste water treatment in power plants & CHP plants

Why the choice is crucial
Materials (steel vs. copper alloys), pressure/temperature and boiler design determine whether AVT(R) (reducing), AVT(O)/OT (oxygenated treatment) or phosphate/Na/PO₄ regimes are appropriate. The wrong strategy will lead to FAC (flow-accelerated corrosion), phosphate heateout, turbine deposits or conductivity fluctuations.

Proven selection logic

• All-ferrous, once-through/HRSG & ultra-high pressure: often AVT(O)/OT (targeted, low O₂ flow) to minimize FAC in feed/econ areas.

• Copper-containing systems / older drum boilers: preferably AVT(R) (reducing conditions with oxygen binders), as Cu alloys tolerate OT poorly.

• Drum boiler with phosphate control: Coordinated/congruent phosphate (Na/PO₄ ratio) for deposit control in the drum boiler; avoid phosphate hideout through close conductivity and Na/PO₄ monitoring.

• Film formers/FFS (Film-Forming Substances): as a supplementary measure (not a substitute) for passive layer stabilization in start/stop-intensive HRSG operations - OEM and IAPWS-compliant use.

Additives & conversion (ALMA AQUA)

• Alkalization (ammonia/amines) for the specified pH window in feed/condensate.

• Oxygen binders (e.g. sulphite systems or modern alternatives) for AVT(R).

• Phosphates for drum boilers with Na/PO₄ regime, monitored via CACE (cationic conductivity) & sodium.

• Film formers with controlled dosing and verification (e.g. by means of organic-sensitive measured variables) for layer integrity.

Monitoring - what counts
CACE & specific conductivity, Fe/Cu transport (ppb trend), sodium/silicon in vapor/condensate, dissolved O₂ (depending on regime), differential pressures/temperatures in high-risk FAC zones.

Main drivers of the damage

• FAC: too low oxide layer stability in weakly reducing, high flow velocities/high turbulence.

• Pitting under deposits: metallic particles/salts promote underfilm corrosion.

• Turbine sensitivity: minimal carrier impurities (Na⁺, SiO₂, organics) lead to deposits/erosion.

Protection concept with additives & operation

• Alkalizing agents (ammonia/amines): operate within the OEM/IAPWS pH window; use neutralizing amines with a suitable distribution number for long returns.

• AVT(O)/OT for all-ferrous HRSG: small addition of O₂ for oxide layer stabilization; AVT(R) for Cu alloys.

• Film former (FFA/FFP) as a thin hydrophobic protective film in problematic return/moisture zones; dosage & verification documented.

• Condensate treatment: CPU/Polisher (strong acid cation/anion) limit trace ions; bypass strategies for resin protection.

• Cleanliness: sidestream filter & rinsing strategies against particle transport.

Monitoring & limit indicators
CACE trend, Fe/Cu-ppb (transport), Na & silicate in steam/condensate, O₂ depending on regime, TOC/UV-254 (organic inputs in FFS), Δp increases as fouling indicator.

System features
High heat loads, large surface areas and changing raw water (surface/brackish water, partial flow RO) create scaling, MIC/biofouling and corrosion risks. At the same time, water balance and desalination are economically critical.

Chemical control (ALMA AQUA)

• Hardness stabilizers/antiscalants: Inhibition of CaCO₃, CaSO₄, Ba/Sr sulphates, silicate; operation according to saturation indices/project data.

• Corrosion inhibitors: phosphonate/organic systems suitable for CS/Cu/Al materials; zinc-free options for environmental requirements.

• Biocides: rotating oxidative/non-oxidative program against MIC/biofilm; defoamer for stable cooling tower hydraulics.

• Dispersants: Particle/silt control, keep deposits mobile.

Operating & measurement concept

• Optimize number of cycles/desalination vs. raw water & environmental requirements.

• Online KPIs: pH, conductivity, ORP, turbidity/SDI, nutrients, ΔT/Δp.

• Side stream filtration (1-5 %) reduces particle/biofouling.

• Material protection: sacrificial anodes/ICCP on exposed components, check compatibility with inhibitors.

Origin & loads
Waste water from cooling systems/boilers, rinsing and cleaning water, ion exchanger regenerates. Typical loads: hardness/salts, phosphates, iron/copper, organic residues, biocides.

Treatment chain (modular)

• Precipitation/flocculation & pH control: separation of metals/phosphate/silicate; polymers for dewaterable flocs.

• Oxidative stages (e.g. peroxide-based) for COD/color reduction, detoxification of reactive species.

• Membrane routes: UF as protection, RO for recovery; with high salt load possibly EFC/crystallizers or ZLD concepts.

• Circulation: RO permeate as make-up/feed water; return concentrate to chemical-physical line.

Additive compatibility
ALMA AQUA formulations are RO/UF compatible, minimize scaling/fouling and are selected so that downstream (Bio/RO) is not impaired.

Benefit

• Safe limit values and reduced disposal costs

• Water reuse (permeate) reduces raw water and energy requirements

• Predictable operating costs thanks to sludge-optimized precipitation/flocculation packages

Why load changes are critical
Modern CHP plants and HRSG (Heat Recovery Steam Generators) often operate in flex mode - fast starts, frequent load changes, partial load. This puts enormous strain on the water chemistry: pH fluctuations, oxygen ingress, FAC risks and unstable passive layers are the result.

Additive strategies for flexible driving

• Fast-reacting oxygen binders: prevent corrosion peaks when starting up.

• Amine combinations with a high distribution number: ensure uniform pH in long returns even at changing temperatures.

• Film formers (FFS): protect against repeated condensation & evaporation cycles through stable hydrophobic layers.

• Phosphate strategy in the drum boiler: closely monitored (Na/PO₄ ratio) to avoid "hideout" effects at partial load.

Monitoring & operating instructions

• Online O₂, conductivity (CACE), Fe transport & Δp trends.

• Automated dosing, coupled to load changes.

• Periodic metal analysis (Fe/Cu) for FAC prevention.

Practical benefits
Even in flex mode, the boiler, HRSG and pipe systems remain protected, downtime corrosion is avoided and availability for grid control operation is ensured.

Why film formers are increasingly important
Film-forming substances (FFS) based on amides/amines are used as a supplement to classic AVT/OT regimes. They create ultra-thin protective layers on metal surfaces and protect particularly sensitive areas such as wet returns, air coolers or low-temperature condensation zones. However, incorrect application can cause turbine deposits, foam or analytical problems.

Application and dosing strategy

• Introduction with defined "initial dose", then switch to low continuous dosing.

• Combination with AVT(O)/AVT(R), no replacement - pH control remains central.

• Dosing points: ideal in feed water or directly in front of CPU outlet to ensure homogeneous distribution.

• CIP & cleaning: no residues in resins, therefore check compatibility.

Proof & control of effectiveness

• Indirect evidence via Fe transport (ppb trend): decreasing values confirm protective effect.

• Organic monitoring (TOC/UV-254): peaks that are too high indicate overdosing or degradation products.

• Visual inspections during revisions (coating pattern, surface gloss).

• Carry out OEM/IAPWS-compliant test series before widespread use.

Practical benefits
Film formers provide additional protection at critical weak points, reduce FAC risks in the return flow and extend the service life of the system - when used in a controlled manner with reliable monitoring.