Types of Waste Heat Recovery Boilers and Their Industrial Applications

Waste Heat Recovery Boilers generate large volumes of waste heat through manufacturing & process operations that escape into atmosphere resulting in energy losses. A Waste Heat Recovery Boiler is a suitable solution, which recover heat from hot exhaust gases to produce steam or thermal energy. Various types of Waste Heat Recovery Boilers can be used based on temperature and gas flow of the heat source, pressure and flow rate of the steam and required operating temperatures & flow rates of other heating fluids.

What Is a Waste Heat Recovery Boiler?

Waste Heat Recovery Boiler is a type of heat recovery equipment that absorbs the heat content of hot industrial waste gases. The generated steam is then utilized for process heating, generation of electricity and production of hot water, and for various industrial applications. This saves on fuel costs and enhances plant energy efficiency. The basic principle is: Hot exhaust gas ->Heat Transfer-> Water heating -> Steam generation -> Industrial applications

Types of Waste Heat Recovery Boilers

1. Fire Tube Waste Heat Recovery Boiler

In fire tube boiler hot flue gas pass through tube while water passes through outer of the tube. The heat transfer takes place from tube wall & heats the water to produce steam. The fire tube boiler is most suitable for medium temperature, pressure and steam duty. Design of fire tube boiler is simple & can apply in industry.

Applications:

• Food processing
• Chemical industries
• Textile industries
• Manufacturing plants
• Process heating systems

2. Water Tube Waste Heat Recovery Boiler

In this type of boiler, water passes through the tubes but hot gases are around the tubes transferring the heat to water within the tubes. They are efficient with use at high temperature and high pressure and can be made in larger capacities of steam.

Applications:

• Power plants
• Steel plants
• Cement industries
• Refineries
• Petrochemical industries

3. Coil-Type Waste Heat Recovery Boiler

These type of boiler use manufactured tubes or coils which facilitate hot gas to transfer heat onto the boiler water or another working fluid. Their relatively compact nature make them efficient to installation when limited space is available. They can also be manufactured based on the available exhaust temperature, volume flowrate as well as steam quality (quantity) demand.

Applications:

• Industrial furnaces
• Chemical plants
• Metal processing
• Process heating
• Manufacturing facilities

4. Combination Fire and Water Tube Boiler

Combining designs from the two styles - fire tube boilers combine features of the first two designs and can be designed on demand for waste heat applications. When used with steam to provide flexible heat recovery and suitable for the varying requirements of the varying industrial conditions, the operation is well achieved by designing for the waste heat parameters and for the steam production requirements of a site.

Applications:

• Chemical processing
• Oil and gas facilities
• Manufacturing plants
• Process industries
• Energy-intensive industries

5. Heat Recovery Steam Generator (HRSG)

A Heat Recovery Steam Generator (HRSG) is a particular type of waste heat recovery boiler. HRSG's are particularly widely used on gas turbines. Gas turbines have high amounts of heat in their exhaust, the HRSG recovers heat and makes steam (the steam could then power either the industrial plant or a further electric generator via a steam turbine).

Applications:

• Combined-cycle power plants
• Gas turbine plants
• Cogeneration systems
• Large industrial facilities
• Power generation plants

Industrial Applications of Waste Heat Recovery Boilers

Cement Industry

Cement plants consume large amounts of energy in high temperature kilns and other thermal operations, such emissions produce large hot flue gas stream which can be utilized by waste heat recovery boilers for power generation.

Steel Industry

The energy consumed in the electric arc and induction furnaces, reheating and auxiliary units for high temperatures can be effectively utilized with the help of a waste heat recovery system that will convert the wasted heat energy into useful form of energy such as heat or steam.

Chemical Industry

Waste heat sources encountered during reactor, furnaces, dryer operations in chemical plants are substantial. The recovered heat is used in steam generation for such operations as process heating, evaporation, drying.

Oil & Gas Sector

Refineries as well as petrochemical plants use high temperature furnaces and process heaters. High temperature exhaust gas from these furnaces and heaters can be used to generate steam utilizing waste heat recovery boilers. This steam is subsequently used in refinery operation and as utility source.

Power Generation

Power plant technology extensively utilizes the waste heat recovery concept. The exhaust gas of gas turbine in combined cycle power plants can pass through an HRSG to generate steam. This steam could run a steam turbine thereby further generating electricity.

Food Processing Sector

Steam used in food processing plants for cooking, sterilization, drying, cleaning and other operations may be obtained through recovery from heat of ovens, dryers and furnaces.

Textile Industry

In the dyeing, drying and finishing operations in the textile sector the demands of thermal energy is quite high. With proper waste heat recovery system the exhaust heat could be use to develop steam and process heat.

Glass and Ceramic Industries

Glass and ceramics are produced at high temperatures and waste gases at high temperature is emitted. These high temperature waste gases can be utilized in waste heat recovery boilers for generating useful steam/ heat.

Benefits of Waste Heat Recovery Boilers

Waste heat recovery boilers offer several advantages to industrial facilities:

• Reduced Fuel Consumption: Recovered heat reduces the amount of additional fuel required for steam generation.
• Improved Energy Efficiency: Waste heat is converted into useful energy instead of being released into the atmosphere.
• Lower Operating Costs: Reduced fuel consumption can lower overall energy expenses.
• Reduced Environmental Impact: Better utilization of waste heat can reduce the need for additional fuel combustion and associated emissions.
• Improved Process Efficiency: Recovered steam can be integrated directly into industrial processes.
• Better Waste Heat Utilization: Heat that was previously considered waste becomes a valuable energy resource.

Factors to Consider When Selecting a Waste Heat Recovery Boiler

Before selecting a boiler, industries should evaluate:

• Exhaust gas temperature
• Gas flow rate
• Gas composition
• Required steam capacity
• Steam pressure and temperature
• Operating hours
• Available installation space
• Heat recovery requirements
• Maintenance requirements
• Corrosion and fouling potential

The boiler should be designed according to the characteristics of the waste heat source and the specific energy requirements of the plant.

Conclusion

Waste heat recovery boilers are an effective solution for industries looking to recover unused thermal energy and improve overall energy efficiency. With different types available, such as fire tube, water tube, coil-type, combination boilers, and HRSGs, industries can select a system based on their process requirements, waste gas conditions, and steam needs. By choosing the right technology and working with experienced Waste Heat Recovery Boiler Manufacturers in India, businesses can reduce fuel consumption, lower operating costs, improve process efficiency, and make better use of available waste heat