Solvent recovery reboilers heated from condenser water
How a plant recovering 2,800 kg of solvent a day can heat its column reboilers with heat pumps that take heat from the condenser cooling water, against a furnace-oil 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
- Heat in, heat out. Every kilogram boiled in the reboiler is condensed again in the condenser, and that heat goes to the cooling tower.
- Low-boiling solvents, high-pressure steam. Methanol and IPA boil at 65 to 82 °C, yet reboilers are fed with plant steam at much higher temperature.
- Cooling tower load. Column condensers are among the largest cooling tower loads on site, adding fan power, make-up water and treatment cost.
- Losses between fuel and process. Burning furnace oil 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 solvent recovery unit serves an API and chemical site. It runs a continuous methanol column recovering about 2,000 kg a day and a batch still recovering 800 kg of isopropyl alcohol a day.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Methanol column reboiler | Bottoms 68–70 °C | 2,000 kg/day distillate × (reflux 1.5 + 1) × 1,100 kJ/kg | 1,528 |
| Spent solvent feed preheat | 30 → 65 °C | 3,000 L/day, cp 2.8 kJ/kg·K, density 0.85 kg/L | 69 |
| IPA batch still | Pot 82–90 °C | 800 kg/day distillate × (reflux 1 + 1) × 665 kJ/kg | 296 |
| Storage and pipework standing losses | – | about 5% | 95 |
| Total useful heat | 1,988 | ||
Averaged over 20 running hours, the heat pumps need about 99 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 105 °C, covering the day's 1,988 kWh in about 18.4 running hours.
- A 3,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: column condenser cooling water at about 45 °C. Taking heat from the condenser water cuts the cooling tower load by the same amount.
- The furnace-oil fired steam boiler stays connected behind a normally closed valve as standby.
- Condenser cooling water is taken at about 45 °C, cooled through the heat pump evaporator and returned to the condensers.
- The heat pumps make hot water at 100–105 °C for the reboiler and the batch still jacket.
- The cooling tower stays in circuit to reject any surplus heat and to cover start-up.
Selected equipment
| Model | SE-WWUHT-27 × 4 |
|---|---|
| Heating capacity | 27 kW each, 108 kW total |
| COP | 2.4 estimated for a 45 °C source (the data sheet is rated on a 60/55 °C source) |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 105 °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 holds the hot-water tank between 98 and 105 °C. TIC-201 controls reboiler duty from the column bottom temperature, and TIC-202 follows the batch still recipe. If hot water falls short, the existing steam reboiler valve opens 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 solvent recovered | – | – |
| CO₂ per year | – | – |
06Benefits
Heat reused in a loop
Condenser heat returns to the reboiler, so the column needs far less outside energy.
Gentler reboiler
Hot water at 100–105 °C reduces fouling and degradation of residues compared with high-pressure steam.
Lighter cooling tower
Heat taken from the condenser water no longer goes to the tower.
Lower energy cost
Each kWh of electricity delivers about 2.4 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
- Solvents recovered, quantities and boiling points
- Column reflux ratios and reboiler duties
- Condenser water flow and temperatures
- Steam use for solvent recovery
- Area classification and available safe-area space
- 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
- Flammable solvents. Keep heat pumps and tank outside the classified area. Only water circuits enter the solvent plant.
- Leak detection. A condenser tube leak can put solvent into the cooling water. Fit a conductivity or LEL check on the source loop before the heat pump.
- High-boiling solvents. Toluene, DMF and similar solvents boil above the heat pump range. Run them under vacuum or keep them on steam.
- 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
Solvent recovery reboilers heated from condenser water
How a plant recovering 2,800 kg of solvent a day can heat its column reboilers with heat pumps that take heat from the condenser cooling water, against a furnace-oil 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
- Heat in, heat out. Every kilogram boiled in the reboiler is condensed again in the condenser, and that heat goes to the cooling tower.
- Low-boiling solvents, high-pressure steam. Methanol and IPA boil at 65 to 82 °C, yet reboilers are fed with plant steam at much higher temperature.
- Cooling tower load. Column condensers are among the largest cooling tower loads on site, adding fan power, make-up water and treatment cost.
- Losses between fuel and process. Burning furnace oil 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 solvent recovery unit serves an API and chemical site. It runs a continuous methanol column recovering about 2,000 kg a day and a batch still recovering 800 kg of isopropyl alcohol a day.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Methanol column reboiler | Bottoms 68–70 °C | 2,000 kg/day distillate × (reflux 1.5 + 1) × 1,100 kJ/kg | 1,528 |
| Spent solvent feed preheat | 30 → 65 °C | 3,000 L/day, cp 2.8 kJ/kg·K, density 0.85 kg/L | 69 |
| IPA batch still | Pot 82–90 °C | 800 kg/day distillate × (reflux 1 + 1) × 665 kJ/kg | 296 |
| Storage and pipework standing losses | – | about 5% | 95 |
| Total useful heat | 1,988 | ||
Averaged over 20 running hours, the heat pumps need about 99 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 105 °C, covering the day's 1,988 kWh in about 18.4 running hours.
- A 3,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: column condenser cooling water at about 45 °C. Taking heat from the condenser water cuts the cooling tower load by the same amount.
- The furnace-oil fired steam boiler stays connected behind a normally closed valve as standby.
- Condenser cooling water is taken at about 45 °C, cooled through the heat pump evaporator and returned to the condensers.
- The heat pumps make hot water at 100–105 °C for the reboiler and the batch still jacket.
- The cooling tower stays in circuit to reject any surplus heat and to cover start-up.
Selected equipment
| Model | SE-WWUHT-27 × 4 |
|---|---|
| Heating capacity | 27 kW each, 108 kW total |
| COP | 2.4 estimated for a 45 °C source (the data sheet is rated on a 60/55 °C source) |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 105 °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 holds the hot-water tank between 98 and 105 °C. TIC-201 controls reboiler duty from the column bottom temperature, and TIC-202 follows the batch still recipe. If hot water falls short, the existing steam reboiler valve opens 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 solvent recovered | – | – |
| CO₂ per year | – | – |
06Benefits
Heat reused in a loop
Condenser heat returns to the reboiler, so the column needs far less outside energy.
Gentler reboiler
Hot water at 100–105 °C reduces fouling and degradation of residues compared with high-pressure steam.
Lighter cooling tower
Heat taken from the condenser water no longer goes to the tower.
Lower energy cost
Each kWh of electricity delivers about 2.4 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
- Solvents recovered, quantities and boiling points
- Column reflux ratios and reboiler duties
- Condenser water flow and temperatures
- Steam use for solvent recovery
- Area classification and available safe-area space
- 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
- Flammable solvents. Keep heat pumps and tank outside the classified area. Only water circuits enter the solvent plant.
- Leak detection. A condenser tube leak can put solvent into the cooling water. Fit a conductivity or LEL check on the source loop before the heat pump.
- High-boiling solvents. Toluene, DMF and similar solvents boil above the heat pump range. Run them under vacuum or keep them on steam.
- 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.