Hot effluent becomes the dye house heat source
How a textile dye house processing 10 tonnes of fabric a day can recover heat from its 40 °C effluent to make process hot water, and what it saves against a briquette-fired 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
- Hot water goes down the drain. Dye baths and rinses are discharged at 40–60 °C, so a large share of the boiler's heat leaves the plant with the effluent.
- ETP struggles with hot effluent. Biological treatment works best below about 35 °C. Hot effluent has to be cooled in open tanks or a cooling tower before aeration.
- Fuel handling and ash. Briquette boilers need fuel storage, manual feeding and ash disposal, and fuel quality varies by season.
- 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 dyes and finishes knitted cotton fabric, about 10 tonnes a day, in soft-flow and jet machines over three shifts. Hot dye baths and wash-off water drain to an equalisation tank at 40–45 °C before the effluent treatment plant.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Dyeing machine fill water | 35 → 75 °C | 40,000 L/day (10 t fabric × 1:8 liquor ratio, half the baths hot), 35 → 75 °C | 1,858 |
| Soaping and hot wash-off | 60 °C | 20,000 L/day, 30 → 60 °C | 697 |
| Storage and pipework standing losses | – | about 5% | 128 |
| Total useful heat | 2,682 | ||
Averaged over 20 running hours, the heat pumps need about 134 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
- 5 × SE-WWUHT-27 (135 kW total) (SE-WWUHT water-source, R245fa) delivering 85 °C, covering the day's 2,682 kWh in about 19.9 running hours.
- A 4,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: dye house effluent after screening at about 40 °C. Cooling the effluent to 25–30 °C before biological treatment is a by-product.
- The biomass-briquette fired steam boiler stays connected behind a normally closed valve as standby.
- Screened effluent from the equalisation tank is pumped through a cleanable effluent heat exchanger. A clean intermediate water loop carries the heat to the heat pump evaporators.
- The heat pumps make 80–85 °C water into a storage tank that fills the dyeing machines at 75 °C, so the steam only handles the final ramp to dyeing temperature.
- Soaping and hot wash-off water is heated through its own PHE from the same tank.
- Effluent leaves the recovery exchanger at 25–30 °C and goes straight to biological treatment.
Selected equipment
| Model | SE-WWUHT-27 × 5 |
|---|---|
| Heating capacity | 27 kW each, 135 kW total |
| COP | 2.9 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 | 85 °C |
| Storage | 4,500 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 top of the tank starts the heat pumps below 78 °C and stops them at 84 °C. A flow switch and TT on the effluent loop stop the heat pumps if the equalisation tank runs low or the effluent falls below 30 °C. TIC-202 holds the wash-off water at 60 °C. The boiler stays connected to the machines for final heating and as standby.
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 fabric | – | – |
| CO₂ per year | – | – |
06Benefits
Cooler effluent for the ETP
Effluent reaches the aeration tank at 25–30 °C, which helps biology and removes the need for a separate effluent cooler.
Faster machine cycles
Machines fill with 75 °C water, so heating time per batch is shorter.
Smaller boiler load
The boiler only covers final ramp-up, which cuts fuel handling and ash.
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
- Effluent flow per hour and temperature profile across the day
- Fabric processed per day and liquor ratio
- Hot water and steam use per machine cycle
- ETP inlet temperature limit
- Effluent pH and TDS
- 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
- Fouling and lint. Effluent carries lint, fibres and sizing. Use a self-cleaning screen and a wide-gap or open-channel exchanger that can be opened for cleaning. Never send raw effluent through the heat pump itself.
- Chemistry. Effluent can be alkaline and saline. Choose stainless steel 316 or better for the effluent-side exchanger.
- Flow balance. Effluent flow is batchy. The equalisation tank and the hot water tank together smooth both sides.
- 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
Hot effluent becomes the dye house heat source
How a textile dye house processing 10 tonnes of fabric a day can recover heat from its 40 °C effluent to make process hot water, and what it saves against a briquette-fired 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
- Hot water goes down the drain. Dye baths and rinses are discharged at 40–60 °C, so a large share of the boiler's heat leaves the plant with the effluent.
- ETP struggles with hot effluent. Biological treatment works best below about 35 °C. Hot effluent has to be cooled in open tanks or a cooling tower before aeration.
- Fuel handling and ash. Briquette boilers need fuel storage, manual feeding and ash disposal, and fuel quality varies by season.
- 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 dyes and finishes knitted cotton fabric, about 10 tonnes a day, in soft-flow and jet machines over three shifts. Hot dye baths and wash-off water drain to an equalisation tank at 40–45 °C before the effluent treatment plant.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Dyeing machine fill water | 35 → 75 °C | 40,000 L/day (10 t fabric × 1:8 liquor ratio, half the baths hot), 35 → 75 °C | 1,858 |
| Soaping and hot wash-off | 60 °C | 20,000 L/day, 30 → 60 °C | 697 |
| Storage and pipework standing losses | – | about 5% | 128 |
| Total useful heat | 2,682 | ||
Averaged over 20 running hours, the heat pumps need about 134 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
- 5 × SE-WWUHT-27 (135 kW total) (SE-WWUHT water-source, R245fa) delivering 85 °C, covering the day's 2,682 kWh in about 19.9 running hours.
- A 4,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: dye house effluent after screening at about 40 °C. Cooling the effluent to 25–30 °C before biological treatment is a by-product.
- The biomass-briquette fired steam boiler stays connected behind a normally closed valve as standby.
- Screened effluent from the equalisation tank is pumped through a cleanable effluent heat exchanger. A clean intermediate water loop carries the heat to the heat pump evaporators.
- The heat pumps make 80–85 °C water into a storage tank that fills the dyeing machines at 75 °C, so the steam only handles the final ramp to dyeing temperature.
- Soaping and hot wash-off water is heated through its own PHE from the same tank.
- Effluent leaves the recovery exchanger at 25–30 °C and goes straight to biological treatment.
Selected equipment
| Model | SE-WWUHT-27 × 5 |
|---|---|
| Heating capacity | 27 kW each, 135 kW total |
| COP | 2.9 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 | 85 °C |
| Storage | 4,500 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 top of the tank starts the heat pumps below 78 °C and stops them at 84 °C. A flow switch and TT on the effluent loop stop the heat pumps if the equalisation tank runs low or the effluent falls below 30 °C. TIC-202 holds the wash-off water at 60 °C. The boiler stays connected to the machines for final heating and as standby.
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 fabric | – | – |
| CO₂ per year | – | – |
06Benefits
Cooler effluent for the ETP
Effluent reaches the aeration tank at 25–30 °C, which helps biology and removes the need for a separate effluent cooler.
Faster machine cycles
Machines fill with 75 °C water, so heating time per batch is shorter.
Smaller boiler load
The boiler only covers final ramp-up, which cuts fuel handling and ash.
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
- Effluent flow per hour and temperature profile across the day
- Fabric processed per day and liquor ratio
- Hot water and steam use per machine cycle
- ETP inlet temperature limit
- Effluent pH and TDS
- 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
- Fouling and lint. Effluent carries lint, fibres and sizing. Use a self-cleaning screen and a wide-gap or open-channel exchanger that can be opened for cleaning. Never send raw effluent through the heat pump itself.
- Chemistry. Effluent can be alkaline and saline. Choose stainless steel 316 or better for the effluent-side exchanger.
- Flow balance. Effluent flow is batchy. The equalisation tank and the hot water tank together smooth both sides.
- 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.