Tannery drum water heated efficiently
How a tannery processing 5 tonnes of wet-blue a day can make all its 35–60 °C drum water with heat pumps, against a diesel-fired hot-water generator.
▶Video: Heat pumps for textile and leather processing
V03 · 2–2.5 minDyeing, pre-treatment and tanning, with heat recovered from hot drain water
Video coming soon01Problem statement
- Precise floats need precise water. Retanning and fatliquoring floats must be at 50 to 60 °C. Water that is too hot spoils the emulsion, and water that is too cool slows penetration.
- Mixing hot and cold by hand. Operators often blend boiler water with cold water at the drum, so float temperatures vary batch to batch.
- Low-temperature job, high-temperature fuel. A fired generator burning diesel is used for water that only needs to reach 60 °C.
- Losses between fuel and process. Burning diesel 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 tannery processes 5 tonnes of shaved wet-blue a day into crust and finished leather. Drums run pickling, tanning, retanning, dyeing and fatliquoring on two shifts.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Fatliquoring floats | 55–60 °C | 5,000 kg × 1.5 L/kg = 7,500 L, 28 → 60 °C | 279 |
| Retanning and dyeing floats | 40–50 °C | 5,000 kg × 2 L/kg = 10,000 L, 28 → 50 °C | 255 |
| Pickling and tanning floats | 35–40 °C | 10,000 L/day, 28 → 40 °C | 139 |
| Warm washes | 45 °C | 15,000 L/day, 28 → 45 °C | 296 |
| Storage and pipework standing losses | – | about 5% | 48 |
| Total useful heat | 1,018 | ||
Averaged over 20 running hours, the heat pumps need about 51 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-SHT-16C (64 kW total) (SE-SHT cascade heat pump) delivering 65 °C, covering the day's 1,018 kWh in about 15.9 running hours.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The diesel-fired hot-water generator stays connected behind a normally closed valve as standby.
- The heat pumps charge a storage tank at 65 °C. Fresh drum water is heated through PHE-201 so drum water never mixes with the heating loop.
- Thermostatic mixing at each drum header delivers floats at the recipe temperature.
- A separate warm wash tank at 45 °C covers the large wash volumes between process steps.
Selected equipment
| Model | SE-SHT-16C × 4 |
|---|---|
| Heating capacity | 16 kW each, 64 kW total |
| COP | 2.7 at A20 °C / W90 °C (data sheet T1) |
| Power input | about 23.8 kW total at rated conditions |
| Rating | cascade R410A + R515B, rated 90 °C, 95 °C maximum |
| Supply temperature | 65 °C |
| Storage | 2,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 starts the heat pumps below 60 °C and stops them at 65 °C. TIC-201 holds the drum fill water at set-point, and TIC-202 keeps the wash tank at 45 °C. The diesel generator stays as standby for peak days.
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 wet-blue | – | – |
| CO₂ per year | – | – |
06Benefits
Repeatable floats
Water at the right temperature for each step gives more even dye uptake and fatliquor penetration.
Low-temperature efficiency
At 65 °C supply the heat pumps run at a high efficiency all year.
Ready at batch start
Stored hot water fills drums at once, so drum cycles start on time.
Lower energy cost
Each kWh of electricity delivers about 2.7 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
- Wet-blue or rawhide processed per day
- Float ratios and temperatures per process step
- Number of drums and fill schedule
- Present diesel use for hot water
- Water hardness
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Chrome and acids. Keep the heating loop closed and away from tanning floats. Use stainless steel on the fresh-water side of PHE-201.
- Corrosive atmosphere. Tannery air carries hydrogen sulphide and ammonia. Site heat pumps upwind of beamhouse and ETP, and specify coated coils.
- Water hardness. Soft water helps both leather quality and the exchanger. Use softened water for fill if available.
- Electrical. About 24 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Winter output. The SE-SHT cascade gives about 80% of rated output at 7 °C ambient and still runs at −20 °C. Size on the coldest design day for northern sites.
- 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.
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
Tannery drum water heated efficiently
How a tannery processing 5 tonnes of wet-blue a day can make all its 35–60 °C drum water with heat pumps, against a diesel-fired hot-water generator.
▶Video: Heat pumps for textile and leather processing
V03 · 2–2.5 minDyeing, pre-treatment and tanning, with heat recovered from hot drain water
Video coming soon01Problem statement
- Precise floats need precise water. Retanning and fatliquoring floats must be at 50 to 60 °C. Water that is too hot spoils the emulsion, and water that is too cool slows penetration.
- Mixing hot and cold by hand. Operators often blend boiler water with cold water at the drum, so float temperatures vary batch to batch.
- Low-temperature job, high-temperature fuel. A fired generator burning diesel is used for water that only needs to reach 60 °C.
- Losses between fuel and process. Burning diesel 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 tannery processes 5 tonnes of shaved wet-blue a day into crust and finished leather. Drums run pickling, tanning, retanning, dyeing and fatliquoring on two shifts.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Fatliquoring floats | 55–60 °C | 5,000 kg × 1.5 L/kg = 7,500 L, 28 → 60 °C | 279 |
| Retanning and dyeing floats | 40–50 °C | 5,000 kg × 2 L/kg = 10,000 L, 28 → 50 °C | 255 |
| Pickling and tanning floats | 35–40 °C | 10,000 L/day, 28 → 40 °C | 139 |
| Warm washes | 45 °C | 15,000 L/day, 28 → 45 °C | 296 |
| Storage and pipework standing losses | – | about 5% | 48 |
| Total useful heat | 1,018 | ||
Averaged over 20 running hours, the heat pumps need about 51 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-SHT-16C (64 kW total) (SE-SHT cascade heat pump) delivering 65 °C, covering the day's 1,018 kWh in about 15.9 running hours.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The diesel-fired hot-water generator stays connected behind a normally closed valve as standby.
- The heat pumps charge a storage tank at 65 °C. Fresh drum water is heated through PHE-201 so drum water never mixes with the heating loop.
- Thermostatic mixing at each drum header delivers floats at the recipe temperature.
- A separate warm wash tank at 45 °C covers the large wash volumes between process steps.
Selected equipment
| Model | SE-SHT-16C × 4 |
|---|---|
| Heating capacity | 16 kW each, 64 kW total |
| COP | 2.7 at A20 °C / W90 °C (data sheet T1) |
| Power input | about 23.8 kW total at rated conditions |
| Rating | cascade R410A + R515B, rated 90 °C, 95 °C maximum |
| Supply temperature | 65 °C |
| Storage | 2,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 starts the heat pumps below 60 °C and stops them at 65 °C. TIC-201 holds the drum fill water at set-point, and TIC-202 keeps the wash tank at 45 °C. The diesel generator stays as standby for peak days.
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 wet-blue | – | – |
| CO₂ per year | – | – |
06Benefits
Repeatable floats
Water at the right temperature for each step gives more even dye uptake and fatliquor penetration.
Low-temperature efficiency
At 65 °C supply the heat pumps run at a high efficiency all year.
Ready at batch start
Stored hot water fills drums at once, so drum cycles start on time.
Lower energy cost
Each kWh of electricity delivers about 2.7 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
- Wet-blue or rawhide processed per day
- Float ratios and temperatures per process step
- Number of drums and fill schedule
- Present diesel use for hot water
- Water hardness
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Chrome and acids. Keep the heating loop closed and away from tanning floats. Use stainless steel on the fresh-water side of PHE-201.
- Corrosive atmosphere. Tannery air carries hydrogen sulphide and ammonia. Site heat pumps upwind of beamhouse and ETP, and specify coated coils.
- Water hardness. Soft water helps both leather quality and the exchanger. Use softened water for fill if available.
- Electrical. About 24 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Winter output. The SE-SHT cascade gives about 80% of rated output at 7 °C ambient and still runs at −20 °C. Size on the coldest design day for northern sites.
- 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.
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.