Paper machine process water heated from effluent
How a 60 tonne-per-day kraft paper mill can heat shower and white water with a water-source heat pump running on warm effluent, and what it saves against a biomass-fired steam boiler.
▶Video: Waste-heat recovery heat pumps
V10 · 2–2.5 minLifting warm water from condensers, effluent and process cooling to useful heat
Video coming soon01Problem statement
- Steam injected into water. Mills often heat shower and white water by direct steam injection, which loses condensate and wastes boiler feedwater treatment.
- Warm effluent goes to drain. Effluent at 35–45 °C carries a lot of low-grade heat straight to the treatment plant.
- Cold water hurts drainage. Cooler stock and shower water drain more slowly on the wire, which cuts machine speed and raises dryer steam use.
- Losses between fuel and process. Burning briquettes in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference plant is a recycled-fibre kraft paper mill making about 60 tonnes a day of packaging grades. It runs one machine round the clock, with effluent leaving the save-all at around 40 °C.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Shower water heating | 30 → 55 °C | 40,000 L/day fresh water, 30 → 55 °C | 1,161 |
| White water / wire pit make-up | 35 → 45 °C | 30,000 L/day, 35 → 45 °C | 348 |
| Chemical preparation and felt wash | 30 → 60 °C | 10,000 L/day, 30 → 60 °C | 348 |
| Storage and pipework standing losses | – | about 5% | 93 |
| Total useful heat | 1,951 | ||
Averaged over 20 running hours, the heat pumps need about 98 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 4 × SE-WWUHT-27 (108 kW total) (SE-WWUHT water-source, R245fa) delivering 70 °C, covering the day's 1,951 kWh in about 18.1 running hours.
- A 3,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: warm mill effluent / clarified white water at about 40 °C. Cooling the effluent before the treatment plant helps the biological stage, which works best below about 37 °C.
- The biomass-fired steam boiler stays connected behind a normally closed valve as standby.
- A wide-gap exchanger on clarified effluent recovers heat at about 40 °C into a clean loop feeding the heat pump evaporator.
- The heat pump supplies 70 °C water to exchangers on shower water, white water make-up and chemical preparation.
- Steam injection points stay in place as standby.
Selected equipment
| Model | SE-WWUHT-27 × 4 |
|---|---|
| Heating capacity | 27 kW each, 108 kW total |
| COP | 2.93 estimated for a 40 °C source (the data sheet is rated on a 60/55 °C source) |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 70 °C |
| Storage | 3,500 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the tank top starts the heat pump below 65 °C and stops it at 70 °C, if the source loop is above 30 °C. TIC-201 holds shower water at 55 °C and TIC-202 holds wire pit temperature. TIC-203 holds the chemical preparation tank. Steam injection valves open only if a user stays below set point.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of paper | – | – |
| CO₂ per year | – | – |
06Benefits
Better drainage on the wire
Warmer stock and showers improve dewatering, which can reduce dryer steam per tonne.
Condensate saved
Removing direct steam injection keeps more condensate returning to the boiler.
Uses heat already in the mill
The effluent is warm anyway. The heat pump returns that heat to the process.
Lower energy cost
Each kWh of electricity delivers about 2.9 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Paper output per day and grades
- Shower, white water and chemical prep flows and temperatures
- Effluent flow and temperature
- Steam used for water heating
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Fibre and fouling. Use wide-gap or spiral exchangers on effluent and plan regular cleaning. Fibres and fillers foul standard plates quickly.
- Biological growth. Warm white water encourages slime. Coordinate with the biocide programme when temperatures change.
- Source stream. The source must give up roughly two-thirds of the heat delivered. Confirm its flow and temperature over a full production day, and filter it before the evaporator.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.
Talk to us
Paper machine process water heated from effluent
How a 60 tonne-per-day kraft paper mill can heat shower and white water with a water-source heat pump running on warm effluent, and what it saves against a biomass-fired steam boiler.
▶Video: Waste-heat recovery heat pumps
V10 · 2–2.5 minLifting warm water from condensers, effluent and process cooling to useful heat
Video coming soon01Problem statement
- Steam injected into water. Mills often heat shower and white water by direct steam injection, which loses condensate and wastes boiler feedwater treatment.
- Warm effluent goes to drain. Effluent at 35–45 °C carries a lot of low-grade heat straight to the treatment plant.
- Cold water hurts drainage. Cooler stock and shower water drain more slowly on the wire, which cuts machine speed and raises dryer steam use.
- Losses between fuel and process. Burning briquettes in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference plant is a recycled-fibre kraft paper mill making about 60 tonnes a day of packaging grades. It runs one machine round the clock, with effluent leaving the save-all at around 40 °C.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Shower water heating | 30 → 55 °C | 40,000 L/day fresh water, 30 → 55 °C | 1,161 |
| White water / wire pit make-up | 35 → 45 °C | 30,000 L/day, 35 → 45 °C | 348 |
| Chemical preparation and felt wash | 30 → 60 °C | 10,000 L/day, 30 → 60 °C | 348 |
| Storage and pipework standing losses | – | about 5% | 93 |
| Total useful heat | 1,951 | ||
Averaged over 20 running hours, the heat pumps need about 98 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 4 × SE-WWUHT-27 (108 kW total) (SE-WWUHT water-source, R245fa) delivering 70 °C, covering the day's 1,951 kWh in about 18.1 running hours.
- A 3,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: warm mill effluent / clarified white water at about 40 °C. Cooling the effluent before the treatment plant helps the biological stage, which works best below about 37 °C.
- The biomass-fired steam boiler stays connected behind a normally closed valve as standby.
- A wide-gap exchanger on clarified effluent recovers heat at about 40 °C into a clean loop feeding the heat pump evaporator.
- The heat pump supplies 70 °C water to exchangers on shower water, white water make-up and chemical preparation.
- Steam injection points stay in place as standby.
Selected equipment
| Model | SE-WWUHT-27 × 4 |
|---|---|
| Heating capacity | 27 kW each, 108 kW total |
| COP | 2.93 estimated for a 40 °C source (the data sheet is rated on a 60/55 °C source) |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 70 °C |
| Storage | 3,500 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the tank top starts the heat pump below 65 °C and stops it at 70 °C, if the source loop is above 30 °C. TIC-201 holds shower water at 55 °C and TIC-202 holds wire pit temperature. TIC-203 holds the chemical preparation tank. Steam injection valves open only if a user stays below set point.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of paper | – | – |
| CO₂ per year | – | – |
06Benefits
Better drainage on the wire
Warmer stock and showers improve dewatering, which can reduce dryer steam per tonne.
Condensate saved
Removing direct steam injection keeps more condensate returning to the boiler.
Uses heat already in the mill
The effluent is warm anyway. The heat pump returns that heat to the process.
Lower energy cost
Each kWh of electricity delivers about 2.9 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Paper output per day and grades
- Shower, white water and chemical prep flows and temperatures
- Effluent flow and temperature
- Steam used for water heating
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Fibre and fouling. Use wide-gap or spiral exchangers on effluent and plan regular cleaning. Fibres and fillers foul standard plates quickly.
- Biological growth. Warm white water encourages slime. Coordinate with the biocide programme when temperatures change.
- Source stream. The source must give up roughly two-thirds of the heat delivered. Confirm its flow and temperature over a full production day, and filter it before the evaporator.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.