At a time when industrial production is booming, the problems of energy efficiency and environmental protection are becoming increasingly serious. On the one hand, all kinds of industrial processes consume a lot of energy, but there is a significant waste of energy; on the other hand, the environmental pollution brought about by the traditional energy utilization methods has also caused great pressure on the ecosystem.
As an effective way to solve these problems, waste heat recovery has gradually become the focus of attention in the industrial field. Among them, waste heat recovery boiler (WHR boiler) is the key equipment in waste heat recovery technology, which plays an irreplaceable role in enhancing thermal efficiency, saving energy and protecting the environment.
Waste heat recovery boiler is a kind of system specialized in recovering all kinds of waste heat generated in the industrial production process. In the production process of iron and steel, non-ferrous metals, chemical industry, cement and other industries, as well as industrial furnaces, waste incinerators, industrial waste incinerators and other equipment operation, will produce a large amount of waste heat.
Waste heat recovery boilers can convert this waste heat into usable and effective thermal energy, which greatly improves the thermal efficiency of industrial production, realizes energy saving and consumption reduction, and at the same time reduces the environmental pollution caused by energy waste, which is an important booster for the sustainable development of industry .
The source conditions of waste heat emitted from different industrial facilities vary greatly. The gas temperature, pressure, corrosivity, dust content and other factors of waste heat vary under different operating conditions.
For example, gas temperatures of up to 1500°C (2732°F), dust contents of up to 400 g/Nm³ (174 gr/dscf), and SOx contents of up to 40% can occur under certain conditions. Such complex and variable conditions place high demands on the design and manufacture of waste heat recovery boilers, requiring extensive experience and strong technical capabilities.
Companies such as Bidragon are able to provide Waste Heat Recovery Boilers for extreme conditions, while Kawasaki has delivered over 500 Waste Heat Recovery Boilers of all types, and has earned a reputation in the industry for superior quality and reliability.
In boilers fueled by oil, gas, or coal, the combustion of the fuel produces high-temperature flue gases, which release a large amount of heat. The high temperature flue gas firstly enters the furnace, then enters the waste heat recovery device in the front smoke box, then flows through the flue pipe, and then enters the waste heat recovery device in the flue of the rear smoke box.
In this series of processes, the heat of the flue gas is continuously transferred to the water in the boiler system. Eventually, the high-temperature flue gas becomes low-temperature flue gas and is discharged into the atmosphere through the flue pipe. Through such a process, the waste heat recovery boiler makes full use of the heat released by fuel combustion, significantly improves the energy utilization rate, and shows good energy saving effect.
The boiler feed water first enters the economizer. Inside the economizer, the water absorbs heat, increases in temperature, and reaches a temperature slightly lower than the saturation temperature at the pressure of the steam drum, and then enters the boiler drum. The water entering the drum mixes with the saturated water in the drum and then enters the evaporator along the drop tube below the drum.
In the evaporator, the water absorbs heat and begins to evaporate, because only part of the water is converted to steam, so the flow in the evaporator is a vapor mixture. After leaving the evaporator, the vapor-water mixture enters the upper end of the cylinder and is separated by vapor-water separation equipment.
Separated water falls into the water space inside the cylinder, re-entering the descending tube to continue to absorb heat to produce steam; while the steam from the upper end of the cylinder into the heated surface (if you don't need saturated steam, only saturated water vapor, you can omit the heated surface), absorbing heat from saturated water vapor into saturated steam. If there is a demand for reheat steam, additional reheaters can also be installed.
Throughout the boiler system, heat is dissipated at several points, such as flue gas, piping heat loss, boiler exhaust, and warm air from heated rooms. It is this otherwise wasted heat that waste heat recovery boilers utilize to generate additional steam for industrial applications.
The principle of operation is similar to that of a regular boiler, but instead of a burner, the source of energy is the high-temperature exhaust gases generated by the industrial process.
The high-temperature exhaust gases enter a large chamber from the process furnace and come into contact with tubes containing cold water within the chamber, where the heat is transferred to the cold water, causing the water temperature to rise until it reaches the boiling point and is converted to steam. The cooled exhaust gas and the resulting steam are then discharged separately from the boiler. When the heated exhaust gas does not have enough energy to evaporate all the water into steam, an auxiliary burner can be activated to increase steam production.
Advantages of Waste Heat Recovery Boilers
Reduced Operating Costs
The fire tube waste heat recovery boiler requires minimal energy and fuel consumption to operate. Compared to other typical industrial boilers, it offers significant reductions in fuel purchases and operating energy consumption. In terms of long-term operation, this can significantly reduce the capital investment in boiler operation, effectively lowering operating costs and improving the economic efficiency of the enterprise.
Increase Steam Production
Adding a waste heat recovery boiler to an industrial system is equivalent to adding an additional source of steam production. This allows companies to significantly increase steam production capacity to meet growing production demand or to provide steam to support additional industrial processes, helping to expand production and improve productivity.
Reduced Fuel Consumption
Because most of the energy in a waste heat recovery boiler comes from exhaust gases, the amount of fuel required to produce steam, even when an auxiliary burner is required, is far less than in a boiler that relies solely on combustion for heat. As can be seen from actual case data, companies using waste heat recovery boilers can realize significant savings in fuel consumption, further reducing production costs while at the same time reducing their reliance on traditional energy sources.
Reduced Emissions
In most cases, waste heat recovery boilers do not need to burn natural gas or biomass, and therefore do not add significant emissions to the system. Even if an auxiliary burner needs to be activated, the additional emissions generated are much lower than with conventional boilers. This advantage not only meets the requirements of increasingly stringent environmental regulations, but also conforms to the trend of industrial development in the direction of green and clean, and establishes a good environmental image for enterprises.
During the chemical production process, a large amount of waste gas and waste liquid rich in heat energy will be generated. Waste heat recovery boilers can capture this waste heat, on the one hand, to reduce waste emissions, reduce environmental pollution; on the other hand, the recovered heat is converted into steam or hot water, reapplied to the chemical production process, improve the efficiency of energy use, reduce production costs, and achieve a win-win situation for both economic and environmental benefits.
The iron and steel smelting process produces a large amount of high-temperature waste gas, which contains considerable heat energy. Utilizing waste heat recovery boilers to recover this waste heat can provide a stable supply of steam for iron and steel production, meet the thermal energy demand in the production process, effectively reduce the energy consumption of iron and steel enterprises, and enhance the competitiveness of enterprises in the market.
In the process of power production such as thermal power generation and nuclear power generation, the amount of waste heat generated is huge. Waste heat recovery boilers can recycle this waste heat, which not only improves the efficiency of energy utilization and reduces energy waste, but also reduces the environmental pollution caused by waste heat emissions, which is of great significance in promoting the development of the electric power industry in a sustainable direction.
In the manufacturing process of cement, glass and other building materials, a large amount of waste heat will also be generated. Through the application of waste heat recovery boilers, these waste heat can be recycled and utilized to provide the required thermal energy for the production of building materials, reduce the dependence on external energy sources, lower production costs, and at the same time help the building materials industry to achieve the goal of energy saving and emission reduction.
Comparison Between Waste Heat Recovery Boilers And Conventional Boilers
Conventional boilers rely on the combustion of coal, oil, natural gas and other fuels to generate heat; whereas waste heat recovery boilers mainly utilize waste heat generated by industrial processes, and only use auxiliary burners under special circumstances (such as when the waste heat energy is insufficient) without the need for specialized combustion systems, which reduces the demand for conventional fuels from the root.
With no combustion system, the structure of waste heat recovery boilers is relatively simple. At the same time, they utilize the exhaust gases generated by the industrial process as the flow power and do not need to be equipped with fans for ventilation, further simplifying the equipment structure and reducing energy consumption. In contrast, conventional boilers usually have complex combustion chambers and ventilation systems, and the equipment structure is more complicated.
Waste heat recovery boilers are able to operate under multiple pressures, an operation mode that significantly improves heat recovery efficiency. In contrast, many conventional boilers can only be operated at a single or limited pressure, with relatively low heat recovery efficiency. In the heat transfer method, the waste heat recovery boiler mainly relies on convection heat transfer, compared with some conventional boilers to radiation-based heat transfer, more efficient in the waste heat utilization scenario.
Waste heat recovery boilers often use special finned tube design, which can effectively strengthen the heat transfer effect; conventional boilers mostly use membrane water-cooled wall structure. Different heat transfer components design, the boiler's heat transfer performance and the overall operating effect has an important impact, so that the waste heat recovery boiler in the utilization of waste heat more advantageous.
Waste heat recovery boilers play a key role in the industrial field due to their unique working principle and significant advantages. From the definition, workflow to application areas, and then compared with conventional boilers, we clearly see its great value in energy saving and consumption reduction, capacity enhancement, and environmental protection.
With the deepening of the concept of sustainable industrial development, as well as the increasing pressure on energy and the environment, the waste heat recovery boiler is bound to usher in a broader space for development. In the future, its technology is expected to be further innovated and upgraded, and the scope of application will continue to expand, contributing more to the green transformation of global industry.
