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Leading waste heat recovery boiler (WHRB) manufacturers in India include Par Boiler Pvt. Ltd., Thermax, ISGEC Heavy Engineering, Forbes Marshall, and Cheema Boilers. These companies design and supply exhaust gas boilers, heat recovery steam generators (HRSG), economisers, and complete WHR systems for cement kilns, DG sets, glass furnaces, steel plants, chemical reactors, gas turbines, and process industry exhausts. A WHRB generates steam or hot water from industrial exhaust gas without burning additional fuel reducing energy cost, cutting CO₂ emissions, and delivering capital payback within 2–4 years for most applications.
Most industrial plants have a flare stack or chimney that burns continuously not because it is disposing of waste gas, but because hot exhaust from a kiln, engine, furnace, or compressor exits through it at 300°C, 400°C, or more. That heat energy has real monetary value. Translated into steam output, it displaces natural gas or coal that the plant would otherwise purchase. Translated into a monthly rupee figure against the capital cost of a recovery system, it typically produces a payback period of 2–4 years.
A waste heat recovery boiler captures this lost energy stream, transfers the heat to water, and produces steam or hot water that the plant can use directly in its processes, heating systems, or power generation without burning a single additional unit of fuel. The boiler has no burner, no fuel system, and no combustion emissions. It is a heat exchanger with a steam generation function, and its input fuel is heat that would otherwise be wasted.
This guide explains how waste heat recovery boilers work, which types suit which industrial applications, what they cost in India in 2026, how to calculate the financial return on investment, and which manufacturers have the engineering capability to design a system that actually delivers the promised performance over its operational life.
A waste heat recovery boiler (WHRB) is a heat exchanger that captures thermal energy from hot industrial exhaust gases from engines, kilns, furnaces, gas turbines, compressors, or chemical reactors and transfers that heat to water to generate steam or hot water without burning any additional fuel. The exhaust gas acts as the "fuel" its thermal energy, which would otherwise be vented to atmosphere as waste, is recovered and converted into productive steam output. Also known as an exhaust gas boiler, heat recovery steam generator (HRSG), or waste heat steam generator.
The working principle of a WHRB is simpler than a fired boiler because there is no combustion. Hot exhaust gas from the industrial source a DG set exhaust manifold, a kiln exit gas duct, a furnace flue, a gas turbine exhaust enters the WHRB and flows over or through heat transfer surfaces (tubes carrying water). Heat transfers from the hot gas to the water through convection and, at higher temperatures, radiation. The water heats up, reaches saturation temperature, and converts to steam. The steam exits through the WHRB steam drum and is distributed to the plant's steam header. The cooled exhaust gas exits the WHRB at a lower temperature through the stack.
Step 1 — Hot exhaust gas entry: Exhaust gas from the industrial source enters the WHRB at the gas inlet duct. Gas temperature at entry depends on the source DG set exhaust typically enters at 380–450°C, cement kiln exhaust at 300–400°C, glass furnace at 400–600°C, gas turbine exhaust at 450–550°C.
Step 2 — Heat transfer through tube bundles: The hot gas flows over tube bundles carrying water. Heat transfers from the gas to the water through convective heat transfer. In high-temperature WHRBs, a radiant section at the gas inlet handles the highest temperature portion of heat transfer before the gas cools enough for efficient convective transfer in downstream tube banks.
Step 3 — Steam generation in the drum: Water heated to saturation temperature in the evaporator tubes rises to the steam drum as a steam-water mixture. Steam and water separate in the drum. Clean, dry saturated steam exits through the steam outlet. Feed water enters the drum continuously from the feed water system to replace the water converted to steam.
Step 4 — Economiser heat recovery: In well-designed WHRBs, an economiser section downstream of the evaporator extracts additional heat from the still-warm exhaust gas to preheat incoming feed water before it enters the drum improving overall heat recovery efficiency and reducing exit gas temperature further.
Step 5 — Gas exit and bypass: Cooled exhaust gas exits the WHRB through the outlet duct and stack. A bypass damper system allows exhaust gas to be diverted around the WHRB when the steam is not needed — such as during plant startup, maintenance, or when the process does not require steam without stopping the industrial source equipment.
| WHRB Type | Gas Temperature Range | Steam Pressure | Steam Output | Best Application |
|---|---|---|---|---|
| Fire Tube WHRB | 250°C – 500°C | Up to 18 kg/cm² | 0.2 – 5 TPH | DG set exhaust, small engines, process exhaust |
| Water Tube WHRB | 300°C – 700°C | 10 – 65 kg/cm² | 1 – 100+ TPH | Cement kiln, glass furnace, chemical plant, steel |
| HRSG | 400°C – 600°C | 20 – 100 kg/cm² | 5 – 500+ TPH | Gas turbine exhaust, combined cycle, co-generation |
| Economiser | 150°C – 350°C | Existing boiler pressure | Feed water preheat only | Addition to existing boilers, moderate-temp flue gas |
| Finned Tube WHRB | 200°C – 450°C | Up to 25 kg/cm² | 0.2 – 8 TPH | DG set, compressor, process gas exhaust |
| Radiant + Convective | 600°C – 1,200°C | 20 – 80 kg/cm² | 5 – 150+ TPH | Cement kiln exit, glass furnace, smelting furnace |
| Industry / Source | Exhaust Gas Temperature | Typical Steam Output | WHRB Type | Primary Benefit |
|---|---|---|---|---|
| DG Set (diesel generator) | 380°C – 450°C | 0.3 – 3 TPH per set | Fire tube / Finned tube | Free steam from captive power cost |
| Cement Kiln | 300°C – 450°C | 5 – 30 TPH | Water tube WHRB | Power generation, utility steam |
| Glass Furnace | 400°C – 600°C | 3 – 20 TPH | Radiant + Convective WHRB | Displaces fossil fuel boiler |
| Gas Turbine | 450°C – 550°C | 10 – 200 TPH | HRSG | Combined cycle power, process steam |
| Steel Plant (EAF, Sinter) | 500°C – 1,000°C | 5 – 50 TPH | Radiant + Convective WHRB | Boiler fuel displacement, power |
| Chemical Plant (Reactor / Reformer) | 350°C – 600°C | 2 – 30 TPH | Water tube WHRB | Process steam self-sufficiency |
| Incinerator / Waste-to-Energy | 800°C – 1,100°C | 2 – 30 TPH | Radiant boiler + WHRB | Power generation from waste |
| Ceramic / Tile Kiln | 250°C – 400°C | 0.5 – 5 TPH | Water tube / Fire tube WHRB | Process heating, fuel displacement |
| Fertilizer / Petrochemical | 350°C – 500°C | 5 – 50 TPH | Water tube WHRB / HRSG | Process steam self-supply |
| Existing Industrial Boiler (flue gas) | 180°C – 320°C | Feed water preheat | Economiser | 5–8% boiler fuel saving |
Par Boiler Pvt. Ltd. is one of India's established waste heat recovery boiler manufacturers, designing and supplying exhaust gas boilers, fire tube WHRBs, water tube WHRBs, and finned tube heat recovery systems for industrial applications from its Ahmedabad manufacturing facility. With over 25 years of experience in industrial boiler and heat exchange equipment manufacturing, the company brings engineering depth to WHRB design that goes beyond catalogue-product assembly.
Par Boiler's WHRB range covers fire tube designs for DG set and small engine exhaust (0.2–5 TPH), water tube designs for cement, chemical, and process plant exhaust (1–30 TPH), finned tube systems for lower-temperature process exhaust, and economiser retrofits for existing boiler installations. Each system is designed around the customer's actual exhaust gas data flow rate, temperature, composition, and fouling characteristics rather than a standard specification.
The company's integration of WHRB design with its core industrial boiler range is particularly valuable for plants that need both a primary fired boiler and a waste heat recovery system the two systems can be designed as a coordinated steam supply, with the WHRB generating base load steam from recovered heat and the fired boiler supplementing during peak demand or when the waste heat source is offline.
All WHRB systems are supplied with IBR certification (where required by operating pressure), commissioning support, and after-sales service through the company's national network.
Best for: DG set exhaust recovery, cement and chemical plant WHR, process industry exhaust boilers, economiser retrofits for existing boilers, Gujarat and pan-India industrial plants.
Have a hot exhaust gas stream you are not recovering? Par Boiler's engineering team reviews your exhaust gas data temperature, flow, composition and calculates recoverable steam output and financial ROI before proposing a system. Contact Par Techno-Heat Pvt. Ltd. for a free WHRB feasibility review.
Thermax is one of India's most established energy and environment engineering companies, with a strong WHR product range covering HRSGs for gas turbines, large-capacity water tube WHRBs for cement and steel industries, and complete waste heat power generation systems. Their technical depth in co-generation and combined cycle plant engineering makes them a strong choice for large WHR projects with power generation objectives.
Best for: Gas turbine HRSG, large cement and steel plant WHR, waste-to-energy, co-generation projects requiring complete system engineering.
ISGEC has significant experience in large-capacity waste heat recovery and process boilers for heavy industries. Their WHRB range serves sugar, chemical, steel, and power plant applications with high-capacity, high-pressure designs backed by in-house pressure vessel engineering capability.
Best for: Large-capacity WHR for sugar, chemical, steel, and power plant applications requiring high-pressure, high-capacity systems.
Forbes Marshall's waste heat recovery product range covers exhaust gas boilers and HRSGs integrated with their steam system engineering capability. Their strength lies in process efficiency optimisation designing WHR systems as part of a comprehensive plant energy management strategy rather than standalone equipment.
Best for: Process industries seeking WHR as part of comprehensive steam system efficiency optimisation.
Cheema Boilers manufactures waste heat recovery boilers and process boilers for cement, sugar, chemical, and power plant applications, with experience in both standard and custom WHRB configurations for diverse exhaust gas sources.
Best for: Cement, sugar, and chemical industry waste heat recovery with standard to custom WHRB configurations.
| Manufacturer | Location | Key WHRB Products | Best For | Core Strength |
|---|---|---|---|---|
| Par Boiler Pvt. Ltd. | Ahmedabad | Fire tube WHRB, water tube WHRB, finned tube, economiser | DG set, cement, chemical, economiser retrofit | 25+ years, custom engineering, integrated boiler supply |
| Thermax | Pune | HRSG, large WHRB, co-gen systems | Gas turbine, large cement/steel, co-generation | Large-scale WHR and co-generation engineering |
| ISGEC Heavy Engineering | Pan-India | Process WHRB, high-pressure WHR | Sugar, steel, chemical, power plant WHR | Heavy engineering, high-capacity, high-pressure |
| Forbes Marshall | Pune | Exhaust gas boiler, HRSG, process WHR | Process industries, steam system efficiency | Integrated process energy optimisation |
| Cheema Boilers | Pan-India | WHRB for cement, sugar, chemical | Cement, sugar, chemical WHR | Diverse WHRB configurations at competitive cost |
The case for waste heat recovery in Indian industrial plants is measurable and specific. Unlike many energy-saving investments where the benefit is estimated, WHRB returns are directly calculable from exhaust gas temperature, flow rate, and the price of the fuel being displaced.
| Benefit | Quantified Impact |
|---|---|
| Fuel cost reduction | Steam generated from WHR displaces purchased fuel savings of ₹5–50 lakh/month depending on plant size and fuel type displaced |
| CO₂ emission reduction | Every tonne of steam generated from waste heat avoids approximately 80–120 kg of CO₂ compared to coal-fired generation |
| No additional fuel cost | WHRB has no burner and burns no fuel steam cost is essentially zero beyond water, power, and maintenance |
| ESG performance improvement | Quantified waste heat recovery improves specific energy consumption (SEC), ISO 50001, and ESG sustainability reporting metrics |
| Stack exit temperature reduction | Reducing exhaust gas exit temperature also reduces the plant's visible plume and convective heat loss from the stack |
| Capital payback period | Typically 2–4 years for most WHRB installations in Indian industrial conditions, depending on fuel cost and operating hours |
Before investing in a waste heat recovery boiler, every plant should calculate the expected return on investment. Here is a worked example for a common DG set application:
| Parameter | DG Set Example (500 kVA) | Cement Kiln Example (500 TPD) |
|---|---|---|
| Exhaust gas temperature | 420°C | 350°C |
| Exit gas temperature (after WHRB) | 180°C | 180°C |
| Steam generated | ~0.7 TPH | ~5 TPH |
| Steam operating hours/month | 480 hrs (20 hrs/day × 24 days) | 600 hrs (25 hrs/day × 24 days) |
| Fuel displaced (natural gas equivalent) | ~1,700 m³/month | ~15,000 m³/month |
| Monthly fuel cost saving (@₹48/m³) | ~₹82,000/month | ~₹7.2 lakh/month |
| Annual saving | ~₹9.8 lakh/year | ~₹86 lakh/year |
| Approximate WHRB cost | ₹12–18 lakh | ₹70–100 lakh |
| Estimated payback period | 15–22 months | 10–14 months |
This is an illustrative calculation using approximate values. Actual steam output, fuel savings, and payback period depend on your specific exhaust gas temperature, flow rate, operating hours, and the fuel being displaced. Par Boiler provides a detailed site-specific feasibility calculation as part of its WHRB project development process.
| WHRB Type | Steam Output | Application | Approx. Price Range (₹) |
|---|---|---|---|
| Small Fire Tube WHRB | 0.2 – 1 TPH | DG set, small engine exhaust | ₹5 lakh – ₹18 lakh |
| Medium Fire Tube / Finned WHRB | 1 – 4 TPH | DG set bank, small process exhaust | ₹18 lakh – ₹55 lakh |
| Water Tube WHRB (medium) | 2 – 10 TPH | Cement kiln, chemical plant, glass | ₹40 lakh – ₹1.5 crore |
| Water Tube WHRB (large) | 10 – 50 TPH | Large cement, steel, chemical, power | ₹1.5 crore – ₹8 crore+ |
| Economiser (retrofit) | Feed water preheat | Existing boiler flue gas | ₹2 lakh – ₹15 lakh |
| HRSG (gas turbine) | 20 – 200+ TPH | Gas turbine exhaust, co-generation | ₹5 crore – ₹50 crore+ |
Prices are indicative 2026 estimates. Actual cost depends on exhaust gas temperature, gas volume, steam output, operating pressure, IBR compliance level, and site-specific installation requirements. Contact Par Boiler for a site-specific quotation and ROI calculation.
Have exhaust gas data for a WHRB feasibility study? Share your exhaust gas temperature, flow rate, and operating hours with Par Boiler's engineering team and receive a detailed steam output calculation and financial ROI analysis. Contact Par Techno-Heat Pvt. Ltd. here.
| Criteria | What to Verify |
|---|---|
| Thermal design capability | Can they provide heat and mass balance calculations for your specific exhaust gas conditions? |
| Reference installations | Ask for WHR installations on your specific exhaust source (DG set, kiln, glass furnace, etc.) |
| IBR certification capability | WHRB above IBR pressure threshold requires IBR-certified design and fabrication |
| Bypass and integration design | WHRB must be safely bypassable when exhaust source maintenance or steam is not needed |
| Fouling and maintenance design | Exhaust gases from cement kilns, DG sets, and industrial processes carry dust tube access for cleaning must be designed in |
| ROI calculation provided | Manufacturer should provide a site-specific steam output and financial payback calculation before order |
| After-sales service | Local service engineers for commissioning, annual inspection, and emergency response |
| Integration with fired boiler | If the plant also has a fired boiler, can the WHRB and fired boiler be coordinated as an integrated steam supply? |
Waste heat recovery boilers typically require less maintenance than fired boilers there is no burner, no combustion system, and no fuel handling. However, the heat transfer surfaces of a WHRB are exposed to exhaust gas that may carry dust, condensable vapours, or corrosive components depending on the industrial source. Tube surface cleanliness directly determines heat transfer efficiency a fouled WHRB generates progressively less steam for the same exhaust gas input.
For structured boiler maintenance guidance applicable to WHRB systems, our industrial boiler maintenance checklist covers the inspection schedule and documentation practices that protect both the equipment and its IBR certification status.
The Indian government has recognised waste heat recovery as a key component of industrial energy efficiency improvement, and several incentive programmes support WHRB investments:
Many industrial plants install a WHRB as a supplementary steam source alongside an existing fired boiler. In this configuration, the WHRB generates base load steam from recovered heat and the fired boiler supplements during periods of higher demand or when the exhaust source is offline for maintenance. This arrangement requires careful steam pressure coordination both the WHRB and the fired boiler must generate steam at compatible pressures for connection to a common steam header.
Par Boiler's engineering team handles this integration as part of the project scope, ensuring that the WHRB steam outlet pressure, the fired boiler operating pressure, and the plant's steam distribution system are correctly matched. For a comprehensive understanding of how industrial boiler systems integrate at the plant level, see our guide on steam boiler systems in India design, efficiency, and applications.
For plants evaluating whether to start with a WHRB or an economiser retrofit as a lower-capital first step, our guide on how to improve boiler efficiency covers economiser additions, air preheaters, and other heat recovery measures that can be implemented incrementally without full WHRB installation.
A waste heat recovery boiler (WHRB) is a heat exchanger that captures thermal energy from hot industrial exhaust gases from engines, kilns, furnaces, gas turbines, or process reactors and uses that heat to generate steam or hot water without burning any additional fuel. It converts energy that would otherwise be lost up the chimney into productive steam for plant use, reducing purchased fuel consumption and CO₂ emissions.
Par Boiler Pvt. Ltd., Thermax, ISGEC Heavy Engineering, Forbes Marshall, and Cheema Boilers are among the leading WHRB manufacturers in India. The best choice depends on your exhaust gas temperature, flow rate, required steam output, pressure, and whether you need WHRB integrated with a fired boiler system.
Hot exhaust gas from the industrial source flows over or through heat transfer surfaces (tubes carrying water) inside the WHRB. Heat transfers from the hot gas to the water through convection and radiation. The water heats to saturation temperature and converts to steam, which exits through the steam drum. The cooled exhaust gas exits at a lower temperature through the stack. No fuel is burned the exhaust gas is the energy source.
Main types include: fire tube WHRB (small to medium, DG set exhaust), water tube WHRB (large capacity, cement kiln, glass furnace), HRSG or heat recovery steam generator (gas turbine exhaust, co-generation), finned tube WHRB (lower temperature, compact design), radiant + convective WHRB (very high temperature kiln and furnace exhaust), and economisers (feed water preheating from boiler flue gas).
DG set operators (free steam from captive power exhaust), cement manufacturers (kiln exhaust), glass plants (furnace exhaust), steel plants (electric arc furnace, sinter plant exhaust), chemical and fertilizer plants (reactor and reformer exhaust), gas turbine-based co-generation plants (turbine exhaust), ceramic and tile manufacturers (kiln exhaust), and waste-to-energy facilities are the primary users of waste heat recovery boilers in India.
A 500 kVA DG set generating exhaust at approximately 420°C produces approximately 0.6–0.9 TPH of steam at 8–10 kg/cm² from a correctly sized WHRB. The actual figure depends on the engine's exhaust gas mass flow rate, inlet temperature, and the exit gas temperature achieved. Larger DG sets (1,000 kVA and above) can produce 1–2 TPH or more per set.
WHRB prices in India range from ₹5 lakh for small fire tube units for single DG set exhaust (0.2–1 TPH) to ₹8 crore and above for large water tube WHRBs for cement kiln or glass furnace applications (10–50 TPH). A medium fire tube WHRB for a 500 kVA DG set typically costs ₹12–18 lakh including installation.
For most Indian industrial applications, WHRB payback periods range from 10 months to 4 years depending on the scale of heat recovery, the fuel being displaced, and operating hours. DG set WHRBs typically pay back in 15–24 months. Cement kiln and glass furnace WHRBs often achieve payback in 10–18 months due to higher heat availability and the value of the power generated from the recovered steam.
Yes, if the WHRB operates above the IBR pressure threshold steam pressure above 1 kg/cm² and vessel capacity above 22.75 litres. Most industrial WHRBs generating process steam operate above this threshold and require IBR certification including design approval, material certification, hydraulic pressure testing, and annual inspection. Par Boiler supplies IBR-certified WHRBs with complete documentation.
A waste heat recovery boiler (WHRB) is the general term for any boiler using industrial exhaust heat as its energy source. A heat recovery steam generator (HRSG) specifically refers to large-capacity, multi-pressure waste heat boilers designed for gas turbine exhaust in combined cycle and co-generation power plants. An HRSG typically has multiple drum systems (high-pressure and low-pressure), superheaters, and economisers in a single unit. All HRSGs are WHRBs, but not all WHRBs are HRSGs.
Yes. The WHRB generates steam at a compatible pressure and connects to the plant's common steam header alongside the existing fired boiler. The WHRB provides base load steam from recovered heat; the fired boiler supplements during peak demand or when the exhaust source is offline. Pressure matching between the WHRB and fired boiler is a critical design requirement that the manufacturer must address explicitly.
An economiser is a heat exchanger installed in a boiler's flue gas path that preheats incoming feed water using residual heat from the flue gas. It does not generate steam independently it improves the efficiency of an existing steam boiler by reducing the fuel needed to heat the feed water from ambient to the boiler operating temperature. A full WHRB generates steam independently from an external exhaust gas source. Both are forms of waste heat recovery, but an economiser is simpler, cheaper, and easier to retrofit to existing boilers.
Steam output is calculated from the exhaust gas heat content (mass flow rate × specific heat × temperature drop) and the boiler's heat transfer efficiency. The key inputs are: exhaust gas mass flow (kg/hr), inlet temperature (°C), exit temperature achieved (°C), and heat transfer efficiency of the WHRB design. Par Boiler's engineering team performs this calculation from your actual exhaust gas data and provides guaranteed steam output in the supply specification.
A practical minimum of approximately 250–300°C exhaust gas inlet temperature is required for a WHRB to generate steam economically at useful pressure (8–18 kg/cm²). Below this temperature, steam generation is theoretically possible but the temperature driving force is small, requiring very large heat transfer surface area and making the economics marginal. For lower exhaust temperatures (150–250°C), an economiser for feed water preheating is typically a better investment than a full WHRB.
Yes. Waste heat recovery investments can benefit from: BEE PAT scheme energy savings certificate (ESCert) generation, accelerated depreciation under the Income Tax Act for energy efficiency equipment, concessional finance from SIDBI and banks for energy efficiency projects, and State SEDA schemes that vary by state. The financial case is strong even without incentives the incentives improve the already-positive ROI further.
Yes, indirectly. High-pressure steam from a WHRB can drive a backpressure or condensing steam turbine to generate electricity. This configuration where exhaust heat generates steam that drives a turbine for power and the exhaust steam serves process heating is called co-generation or combined heat and power (CHP). Cement kiln WHRB co-generation projects in India generate captive power from kiln exhaust heat that would otherwise be wasted.
A well-maintained WHRB typically lasts 15–25 years. The primary degradation mechanisms are tube fouling from exhaust gas deposits (managed through regular cleaning) and, for high-temperature applications, potential thermal fatigue if the system experiences frequent rapid temperature cycling. Correct design of thermal expansion allowances and operating procedures that avoid rapid thermal shock protect against thermal fatigue.
Daily monitoring of steam output and exhaust exit temperature. Weekly drum level and safety valve checks. Monthly tube surface inspection through access ports. Annual full internal inspection, tube cleaning, IBR statutory inspection (where applicable), and safety valve testing. WHRB maintenance is significantly less intensive than a fired boiler because there is no combustion system, no burner, and no fuel handling the primary maintenance task is keeping heat transfer surfaces clean.
Three reasons dominate: (1) Exhaust gas temperature or flow rate is lower in actual operation than the design basis WHRB was designed from optimistic assumptions rather than measured data. (2) Exhaust source (DG set, kiln) runs fewer hours than projected steam output is proportional to operating hours. (3) Tube fouling reduces heat transfer efficiency over time due to inadequate maintenance or incorrect tube material specification for the exhaust gas composition.
Three steps: (1) Measure your exhaust gas temperature, approximate flow rate, and operating hours per day. (2) Share this data with a WHRB manufacturer for a feasibility study this should produce an estimated steam output, fuel saving, and payback period at no cost. (3) If the ROI is acceptable, proceed to a detailed design quotation. Par Boiler provides the feasibility study from exhaust gas data as a standard part of project development contact the engineering team to start the process.
Par Techno-Heat Pvt. Ltd. designs and manufactures waste heat recovery boilers fire tube, water tube, finned tube, and economiser systems for DG set, cement kiln, chemical plant, glass furnace, and process industry exhaust heat recovery across India.
Share your exhaust gas temperature, flow rate, and operating hours and receive a free steam output calculation and financial ROI estimate no obligation before the numbers are on the table.
