Power plant chemical dosing pumps inject precise quantities of treatment chemicals into boiler water, cooling water, wastewater, and flue gas treatment systems. These pumps handle corrosive chemicals, abrasive slurries, and critical dosing applications where accuracy directly affects plant efficiency and equipment life. This guide covers power plant chemical dosing pump selection, chemical types, materials, and system design.
Power Plant Chemical Dosing Applications
| Application | Chemical | Function | Dosing Point | Pump Type |
|---|---|---|---|---|
| Boiler water treatment | Ammonia (NH3), hydrazine (N2H4), phosphate (Na3PO4), caustic (NaOH), oxygen scavenger | pH control, corrosion prevention, scale prevention, oxygen removal | Boiler feedwater, steam drum, deaerator | Diaphragm metering (PTFE, precise, zero leakage, corrosive) β multiple pumps per chemical |
| Cooling water treatment | Corrosion inhibitor, scale inhibitor, biocide (chlorine/Br), acid (H2SO4 for pH), dispersant | Corrosion/scale control, biological control, pH adjustment | Cooling tower basin, condenser inlet, makeup water | Diaphragm metering (PTFE, corrosive, precise) or peristaltic (abrasive biocide/slurry) |
| Flue gas desulfurization (FGD) | Limestone slurry (CaCO3), caustic (NaOH), lime slurry (Ca(OH)2), inhibitor | SO2 removal (scrubbing), pH control, scale inhibition | Absorber recirculation, slurry feed, makeup | Peristaltic hose pump (abrasive limestone slurry, no impeller, EPDM/NBR hose) or slurry pump (large flow recirculation) + metering (caustic/inhibitor) |
| Wastewater treatment | Coagulant (alum/FeCl3/PAC), flocculant (polymer), caustic/acid (pH), biocide, nutrient (N/P) | Suspended solids removal, pH control, biological treatment | Clarifier inlet, flocculation basin, neutralization | Diaphragm metering (PTFE, corrosive, precise) + peristaltic (polymer viscous, abrasive slurry) |
| Denitrification (SCR/SNCR) | Ammonia (NH3) or urea solution | NOx reduction (selective catalytic/non-catalytic reduction) | SCR reactor injection grid, SNCR furnace injection | Diaphragm metering (PTFE, precise, ammonia corrosive/toxic, zero leakage) or high-pressure injection pump (OEM) |
| Condensate polishing | Ammonia, morpholine, hydrazine, amine | pH control, corrosion prevention in condensate/feedwater cycle | Condensate pump discharge, feedwater line | Diaphragm metering (PTFE, precise, zero leakage, high purity) |
| Flue gas conditioning | Ammonia, SO3, water | Dust resistivity adjustment (for ESP efficiency) | Flue gas duct upstream of ESP | Diaphragm metering (precise, corrosive/toxic, zero leakage) or injection system (OEM) |
| Fire protection | Foam concentrate, corrosion inhibitor | Fire suppression, system corrosion protection | Fire water line, foam system proportioner | Diaphragm metering or proportioning pump (OEM foam system) |
Critical: Diaphragm Metering Pump (Primary Dosing Pump)
Diaphragm metering pumps are the standard for power plant chemical dosing β why:
- Precision: Β±1% accuracy or better β critical for chemical treatment (overdose = waste/corrosion, underdose = scale/corrosion). Flow adjustable via stroke length (manual or automatic) or VFD. Our metering pumps provide accurate dosing.
- Zero leakage: Diaphragm design = no shaft seal = no chemical leakage. Critical for toxic/corrosive chemicals (hydrazine, ammonia, acid, biocide). Safety + environmental compliance. Our diaphragm metering pumps are sealless.
- Corrosion resistance: PTFE wetted parts (diaphragm, check valves, head) handle most power plant chemicals β acid, caustic, ammonia, hydrazine, biocide. For abrasive slurries (limestone, polymer), use peristaltic or special metering with hardened parts.
- Pressure capability: Metering pumps handle high discharge pressure (10β100+ bar) β needed for boiler feedwater (high pressure) and injection into process lines. Our high-pressure metering pumps handle power plant pressures.
- Multiple pumps: Each chemical gets its own metering pump (don't mix chemicals in one pump). Typical power plant has 10β30+ metering pumps for different chemicals. Our multi-pump systems support all chemicals.
Critical: Peristaltic Hose Pump (Abrasive / Viscous / Slurry Dosing)
For chemicals that damage diaphragm metering pumps:
- Limestone slurry (FGD): 10β30% solids, highly abrasive β diaphragm check valves clog/wear. Use peristaltic hose pump β (1) no impeller/check valves (only hose contacts fluid), (2) handles abrasive slurry, (3) self-priming, (4) reversible (clear blockages), (5) EPDM or NBR hose (abrasion + chemical resistance). Hose life 2000β8000 hours depending on abrasion. Our peristaltic pumps handle FGD limestone slurry.
- Polymer (flocculant): Viscous, shear-sensitive (polymer chains break = reduced effectiveness), slippery. Use peristaltic (low shear, no check valves to clog) or progressive cavity. Our peristaltic pumps handle polymer gently.
- Lime slurry: Abrasive + settling (hardens if stopped). Use peristaltic (no dead zones, flushable) or slurry pump. Flush after shutdown. Our peristaltic pumps handle lime slurry.
- Activated carbon slurry: Abrasive, for mercury removal. Use peristaltic or slurry pump.
Critical: Chemical Compatibility (Material Selection)
| Chemical | Concentration | Temp | Wetted Material | Elastomer | Pump Type |
|---|---|---|---|---|---|
| Sulfuric acid (H2SO4) | 10β98% | Ambientβ50Β°C | PTFE, 316L (dilute only), cast iron (concentrated οΌ90% β passivates) | PTFE, EPDM (dilute), Viton (concentrated) | Diaphragm metering (PTFE) or fluoroplastic (large flow) |
| Hydrochloric acid (HCl) | 5β37% | Ambientβ50Β°C | PTFE, PVDF, 316L (dilute, low temp) | PTFE, EPDM, Viton | Diaphragm metering (PTFE) or fluoroplastic |
| Caustic soda (NaOH) | 10β50% | Ambientβ80Β°C | 316L, carbon steel (concentrated, ambient), PTFE | EPDM, PTFE, NBR (dilute) | Diaphragm metering (316L/PTFE) or 316SS centrifugal (large flow) |
| Ammonia (NH3) | 10β30% aqueous | Ambient | 316L, carbon steel, PTFE | EPDM, PTFE (NBR check β ammonia may swell) | Diaphragm metering (PTFE, zero leakage β toxic) |
| Hydrazine (N2H4) | 10β35% | Ambient | 316L, PTFE | PTFE, EPDM (check compatibility) | Diaphragm metering (PTFE, zero leakage β toxic/carcinogenic) |
| Phosphate (Na3PO4) | 5β20% | Ambientβ60Β°C | 316L, PTFE | EPDM, PTFE | Diaphragm metering |
| Chlorine / biocide | Gas or 10β15% solution | Ambient | PTFE, PVDF, 316L (dilute, check) | PTFE, EPDM (check β chlorine attacks some elastomers) | Diaphragm metering (PTFE, zero leakage β toxic) or chlorine feeder (OEM) |
| Limestone slurry (FGD) | 10β30% solids | Ambientβ60Β°C | Hardened cast iron, high-chrome, rubber-lined | EPDM, NBR (abrasion-resistant hose) | Peristaltic hose (dosing) or slurry pump (recirculation) |
| Polymer (flocculant) | 0.1β1% solution | Ambient | 316L, PTFE | EPDM, NBR (low shear) | Peristaltic (low shear) or progressive cavity |
| Coagulant (FeCl3/alum/PAC) | 10β40% | Ambient | 316L (FeCl3 corrosive β check), PTFE, PVDF | EPDM, PTFE, Viton | Diaphragm metering (PTFE) or peristaltic |
Critical: Dosing System Design
- Redundancy: Critical dosing (boiler water, FGD) requires 100% backup pump (duty/standby). Auto-switch on failure. Our systems include redundant pumps.
- Calibration: Metering pumps need calibration columns (measure actual flow over time) and flow verification. Dose based on feedwater flow (ratio control) or residual measurement (feedback control). Automated systems use PLC + flow meter + residual analyzer.
- Chemical tank materials: HDPE/FRP for acid, carbon steel (lined) for caustic, 316L for ammonia/phos, rubber-lined for slurry. Proper venting, containment (diking), secondary containment.
- Piping: 316L (caustic, ammonia, phosphate), PTFE/PVDF (acid, chlorine), rubber-lined (slurry). Flush connections (for slurry pumps). Proper slope/drain.
- Safety: Toxic chemicals (hydrazine, ammonia, chlorine, acid) require: (1) zero-leakage pumps (diaphragm/peristaltic), (2) secondary containment, (3) fume hood/ventilation, (4) gas detection (ammonia, chlorine), (5) PPE, (6) emergency shower/eyewash, (7) leak detection. Safety first. Our zero-leakage pumps support safe chemical handling.
- Automation: Modern power plants use automated chemical dosing β PLC controls pump speed/stroke based on: feedwater flow (ratio), pH/residual/conductivity (feedback), boiler load, time. Data logging for compliance. Our metering pumps support 4-20mA / VFD / Profibus control.
Critical: Common Problems
- Problem 1: Metering pump check valves clog (slurry). Limestone/lime slurry clogs check valves β no dosing. Solution: peristaltic hose pump (no check valves), flush after shutdown, larger tubing. Our peristaltic pumps avoid check valve clogging.
- Problem 2: Chemical leak (packing/seal failure). Toxic chemical leak β safety/environmental. Solution: diaphragm metering (zero leakage, no shaft seal), double diaphragm with leak detection. Our sealless pumps prevent leaks.
- Problem 3: Inaccurate dosing (pump not calibrated). Over/under dose β scale/corrosion/waste. Solution: calibration column, flow meter, residual feedback, regular calibration, ratio control. Our automated systems maintain accurate dosing.
- Problem 4: Elastomer failure (wrong material). EPDM in concentrated acid, NBR in ammonia β seal failure. Solution: match elastomer to chemical (PTFE for universal chemical resistance, EPDM for caustic/water, Viton for oil/concentrated acid). Our engineers specify correct materials.
- Problem 5: Polymer shear degradation (gear/metering pump). High shear breaks polymer chains β poor flocculation. Solution: peristaltic (low shear), progressive cavity, avoid gear pump. Our low-shear pumps preserve polymer.
- Problem 6: Ammonia/hydrazine vapor lock. Volatile chemicals vaporize in pump β vapor binding. Solution: flooded suction (tank above pump), back pressure valve, PTFE wetted, proper venting. Our pumps handle volatile chemicals with proper system design.
Selection Summary
- Boiler water (ammonia/hydrazine/phosphate/caustic): Diaphragm metering (PTFE, precise Β±1%, zero leakage, toxic chemical, high pressure, multiple pumps)
- Cooling water (inhibitor/biocide/acid): Diaphragm metering (PTFE, corrosive, precise) + peristaltic (abrasive biocide/slurry)
- FGD (limestone slurry/caustic): Peristaltic hose pump (abrasive slurry, no impeller/check valves, EPDM/NBR hose) + slurry pump (large recirculation) + metering (caustic/inhibitor)
- Wastewater (coagulant/polymer/acid/caustic): Diaphragm metering (PTFE, corrosive, precise) + peristaltic (polymer low shear, slurry)
- Denitrification (ammonia/urea): Diaphragm metering (PTFE, precise, toxic zero leakage, high pressure injection)
- Condensate polishing (ammonia/amine/hydrazine): Diaphragm metering (PTFE, high purity, zero leakage, precise)
- Critical: power plant dosing = PRECISION (Β±1% metering, ratio/feedback control) + ZERO LEAKAGE (diaphragm sealless for toxic/corrosive) + ABRASION HANDLING (peristaltic for limestone/lime/polymer slurry) + MATERIAL COMPATIBILITY (PTFE universal, EPDM caustic/water, Viton oil/acid, 316L general) + REDUNDANCY (duty/standby critical) + SAFETY (toxic chemical containment, gas detection, PPE) + AUTOMATION (PLC, flow meter, residual feedback, data logging)
- Our diaphragm metering pumps cover most corrosive/precise dosing; peristaltic hose pumps cover abrasive slurry/polymer; slurry pumps cover large-flow FGD recirculation; fluoroplastic pumps cover large-flow acid. For power plant chemical dosing system design, talk to our power plant engineers with your chemical list, concentrations, flow rates, and dosing points.