Low-pressure process steam from waste heat
How a specialty chemicals plant using 250 kg/h of low-pressure steam can make it with a steam-generating heat pump running on warm cooling water, and what it saves against a furnace-oil fired steam boiler.
▶Video: Low-pressure steam from waste heat
V07 · 2–2.5 minWater-source R245fa heat pumps making 2 bar steam up to 120 °C
Video coming soon01Problem statement
- High-pressure boiler for low-pressure duty. Reactor jackets and the reboiler need steam at only about 2 bar, but the boiler makes 8–10 bar steam that is throttled down.
- Warm water rejected. Reactor cooling and condenser water at 55–60 °C goes to the cooling tower, while fuel is burnt for steam.
- Small boiler, poor efficiency. A small boiler on batch load cycles often and runs well below its rated efficiency.
- 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 plant makes specialty chemicals in batch reactors over two shifts. It uses about 250 kg/h of low-pressure steam for reactor jackets and a solvent recovery reboiler, and rejects warm water from reactor cooling and condensers at 55–60 °C.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Reactor jacket heating | Steam 2 bar, ~120 °C | 150 kg/h × 16 h × 2,329 kJ/kg (condensate 90 °C to steam) | 1,553 |
| Solvent recovery reboiler | Steam 2 bar, ~120 °C | 100 kg/h × 16 h × 2,329 kJ/kg | 1,035 |
| Storage and pipework standing losses | – | about 5% | 129 |
| Total useful heat | 2,717 | ||
Averaged over 16 running hours, the heat pumps need about 170 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
- A Customized water-source, R245fa machine of about 170 kW, a built-to-duty machine on the SE-WWUHT circuit (reference module SE-WWUHT-27, 27 kW).
- Heat source: warm reactor and condenser cooling water at about 58 °C. Cooling the reactor and condenser water is a by-product, so the cooling tower carries less load.
- The furnace-oil fired steam boiler stays connected behind a normally closed valve as standby.
- Warm water from reactor cooling and condensers, at about 58 °C, is collected in a buffer tank and fed to the steam-generating heat pump evaporator.
- The heat pump makes 2 bar steam at about 120 °C directly into the low-pressure header serving the reactor jackets and reboiler.
- The existing boiler feeds the same header through its pressure-reducing station as standby.
Selected equipment
| Machine | Customized water-source, R245fa |
|---|---|
| Capacity | about 170 kW, built to duty |
| Concept | a built-to-duty machine on the SE-WWUHT circuit (reference module SE-WWUHT-27, 27 kW) |
| COP used | 2.93 (estimate) |
| Supply temperature | 120 °C |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
The heat pump holds the low-pressure header at 2 bar. The boiler PRV is set slightly lower, so boiler steam enters only if the heat pump cannot keep up. Reactor and reboiler controllers set their own steam flow. The cooling tower stays on the source loop to take any surplus heat.
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 | – | – |
| CO₂ per year | – | – |
06Benefits
Steam from rejected heat
Heat that went to the cooling tower now makes process steam.
Boiler runs less
The boiler covers only peaks and standby, which cuts fuel and cycling losses.
Less cooling-tower load
Reactor and condenser heat goes to the heat pump, saving tower fan power and make-up water.
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.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Low-pressure steam users, flows and pressures
- Warm water sources, flows and temperatures
- Batch schedule and hours
- Boiler fuel use and condensate return
- 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
- Temperature limit. Heat-pump steam is about 120 °C. Users that need higher temperatures must stay on boiler steam.
- Source availability. Batch processes give uneven warm water. Size the source buffer tank so the heat pump runs steadily through a batch cycle.
- Condensate return. Return condensate to the heat pump feed. Hotter feed raises steam output from the same machine.
- 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.
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
Low-pressure process steam from waste heat
How a specialty chemicals plant using 250 kg/h of low-pressure steam can make it with a steam-generating heat pump running on warm cooling water, and what it saves against a furnace-oil fired steam boiler.
▶Video: Low-pressure steam from waste heat
V07 · 2–2.5 minWater-source R245fa heat pumps making 2 bar steam up to 120 °C
Video coming soon01Problem statement
- High-pressure boiler for low-pressure duty. Reactor jackets and the reboiler need steam at only about 2 bar, but the boiler makes 8–10 bar steam that is throttled down.
- Warm water rejected. Reactor cooling and condenser water at 55–60 °C goes to the cooling tower, while fuel is burnt for steam.
- Small boiler, poor efficiency. A small boiler on batch load cycles often and runs well below its rated efficiency.
- 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 plant makes specialty chemicals in batch reactors over two shifts. It uses about 250 kg/h of low-pressure steam for reactor jackets and a solvent recovery reboiler, and rejects warm water from reactor cooling and condensers at 55–60 °C.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Reactor jacket heating | Steam 2 bar, ~120 °C | 150 kg/h × 16 h × 2,329 kJ/kg (condensate 90 °C to steam) | 1,553 |
| Solvent recovery reboiler | Steam 2 bar, ~120 °C | 100 kg/h × 16 h × 2,329 kJ/kg | 1,035 |
| Storage and pipework standing losses | – | about 5% | 129 |
| Total useful heat | 2,717 | ||
Averaged over 16 running hours, the heat pumps need about 170 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
- A Customized water-source, R245fa machine of about 170 kW, a built-to-duty machine on the SE-WWUHT circuit (reference module SE-WWUHT-27, 27 kW).
- Heat source: warm reactor and condenser cooling water at about 58 °C. Cooling the reactor and condenser water is a by-product, so the cooling tower carries less load.
- The furnace-oil fired steam boiler stays connected behind a normally closed valve as standby.
- Warm water from reactor cooling and condensers, at about 58 °C, is collected in a buffer tank and fed to the steam-generating heat pump evaporator.
- The heat pump makes 2 bar steam at about 120 °C directly into the low-pressure header serving the reactor jackets and reboiler.
- The existing boiler feeds the same header through its pressure-reducing station as standby.
Selected equipment
| Machine | Customized water-source, R245fa |
|---|---|
| Capacity | about 170 kW, built to duty |
| Concept | a built-to-duty machine on the SE-WWUHT circuit (reference module SE-WWUHT-27, 27 kW) |
| COP used | 2.93 (estimate) |
| Supply temperature | 120 °C |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
The heat pump holds the low-pressure header at 2 bar. The boiler PRV is set slightly lower, so boiler steam enters only if the heat pump cannot keep up. Reactor and reboiler controllers set their own steam flow. The cooling tower stays on the source loop to take any surplus heat.
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 | – | – |
| CO₂ per year | – | – |
06Benefits
Steam from rejected heat
Heat that went to the cooling tower now makes process steam.
Boiler runs less
The boiler covers only peaks and standby, which cuts fuel and cycling losses.
Less cooling-tower load
Reactor and condenser heat goes to the heat pump, saving tower fan power and make-up water.
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.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Low-pressure steam users, flows and pressures
- Warm water sources, flows and temperatures
- Batch schedule and hours
- Boiler fuel use and condensate return
- 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
- Temperature limit. Heat-pump steam is about 120 °C. Users that need higher temperatures must stay on boiler steam.
- Source availability. Batch processes give uneven warm water. Size the source buffer tank so the heat pump runs steadily through a batch cycle.
- Condensate return. Return condensate to the heat pump feed. Hotter feed raises steam output from the same machine.
- 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.
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.