Boilers play a vital role in industrial production. It provides the necessary thermal energy for many industrial processes, and is the basis for the smooth running of many production processes. However, in the face of thermal oil boilers and steam boilers, two common types of industrial boilers, companies often need to carefully consider and compare, in order to make the most suitable choice for their production needs. In this paper, we will conduct a comprehensive and in-depth comparison of thermal oil boilers and steam boilers to provide decision-making reference for industrial practitioners.

Definition of thermal oil boiler

A heat transfer oil boiler is a device that passes through a heat exchange body in which a heat stream circulates and absorbs energy in the form of heat. This energy is derived from the combustion of a variety of energy sources such as biomass, natural gas, light oil or fuels derived from waste.

A thermal oil boiler works by heating the thermal oil and subsequently pumping the heated thermal oil to the parts that need to be heated. At these sites, the heat transfer oil releases heat, which is then returned to the boiler. In this way, the transfer of heat is realized in a closed circuit.

Definition of a steam boiler

A steam boiler is a pressurized vessel that transfers heat to the water in it to produce steam for a variety of applications. Steam boilers produce steam power under pressure by heating water to the boiling point using combustible fuels.

Steam boilers are mainly categorized into fire-tube boilers and water-tube boilers depending on how the water is heated. In a fire tube boiler, the flame or high-temperature flue gas flows inside the tubes and transfers the heat to the water outside the tubes; in a water tube boiler, the water is heated inside the tubes, and the flame and high-temperature flue gas are flushed outside the tubes. The name will be a visual representation of the main difference between the two. Steam boilers produce steam through the piping to the location of the need for heating, where the steam condenses into water, and then through the condensate piping back to the boiler, thus completing the heat transfer in a closed loop.

What is the difference between a steam boiler and a thermal oil boiler?

Cost comparison

Procurement costs

In terms of procurement costs, thermal oil boilers and steam boilers are similarly priced. For the same boiler capacity, thermal oil boilers are slightly less expensive than steam boilers. However, this price difference may vary across brands, models, and configurations.

Running costs

Operating costs are relatively high for thermal oil boilers. This is mainly due to its lower thermal efficiency compared to steam boilers, and generally speaking, the higher the thermal efficiency, the lower the operating costs. In addition, heat transfer oil needs to be replaced regularly, whereas the water in a steam boiler does not need to be replaced so frequently. At the same time, steam boilers need to be equipped with a water treatment system due to water quality requirements, which undoubtedly increases its operating costs, while thermal oil boilers do not have this need.

Comparison of safety performance

Steam boiler pressure issues

In most industrial processes, steam systems must operate at extremely high pressures if the high temperatures required are to be achieved through the steam system. For example, saturated steam systems can reach pressures as high as approximately 1,600 psi at temperatures up to 600° F. Even at temperatures up to 400° F, pressures remain high at approximately 235 psi. Such high pressures increase the safety risks associated with the operation of steam systems.

The low pressure advantage of thermal oil boilers

In contrast, most thermal oil systems are connected to the atmosphere. The discharge pressure of the pump needs only to be sufficient to overcome the frictional resistance of the piping and components while maintaining a turbulent flow of fluid. Even at the maximum operating temperature of 600°F, the vapor pressure of the thermal fluid is only a fraction of atmospheric pressure. This low-pressure operation gives thermal oil boilers a significant safety advantage.

Temperature control comparison

Limitations of temperature control for steam boilers

Steam systems rely heavily on controlling pressure to achieve temperature control. However, this type of temperature control, which relies on a delicate pressure balance, is accurate only up to a fluctuating range of about ±10°F. Even worse, as the system is used over time, problems such as equipment corrosion can gradually affect the stability of the pressure control, resulting in a loss of temperature control accuracy. In addition, heating uniformity of the steam system can be problematic due to different rates of steam condensation and condensate discharge at the heat user, and negative factors such as corrosion and scaling of metal surfaces are not yet taken into account.

Precise temperature control of thermal oil boilers

Manufacturers of thermal oil equipment claim that they are able to control temperature fluctuations to ±1.5°F or less. This highly accurate temperature control is achieved by metering and mixing the cooler return fluid with the hotter fluid from the supply piping. This, coupled with high velocity turbulent fluid flow, ensures precise and uniform temperature control across the entire heat user surface. In addition, thermal oil systems not only provide heat efficiently and uniformly, they also provide cooling efficiently and uniformly. Some thermal oils can even heat at temperatures in excess of 400°F and cool at temperatures down to -40°F and below.

Energy efficiency comparison

Energy losses in steam boilers

In steam heating systems, steam traps and drain operations result in significant energy losses. Steam traps waste energy by discharging condensate while trapping underutilized steam, while periodic venting operations displace large amounts of hot water, also resulting in energy loss.

Efficient operation of thermal oil boilers

The operating efficiency of thermal oil heating systems is much higher. With lower operating costs and better process control, an efficient thermal oil heating system can save a plant money and valuable resources.

Environmental impact comparison

Steam boiler water treatment and discharge issues

In steam systems, chemical treatment of water is required to reduce equipment corrosion. However, chemically treated water cannot be discharged directly into the sewer due to the presence of harmful chemicals and high water temperatures. This requires companies to invest additional costs to treat this wastewater to meet environmental requirements.

Environmental Advantages of Heat Transfer Oil

Heat transfer oil is relatively easy to dispose of. It can be mixed with other used lubricants and sent to a local industrial oil recycler for reprocessing into a useful product. This gives heat transfer oil an environmental advantage over steam boilers.

Temperature and Pressure Capability Comparison

Temperature and Pressure Limitations of Steam Boilers

Steam systems have certain limitations in terms of temperature and pressure. Typically, steam-based systems can only operate up to 350°F before operating at pressures above 425 PSIG, which may not be sufficient in some industrial processes with high temperature requirements.

Wide temperature range and low pressure benefits of thermal oil boilers

Heat transfer oil systems are capable of providing a wider temperature range and higher maximum temperatures. When using thermal oil, these systems have a temperature range of 0 - 750° F. And, while achieving such a wide temperature range, thermal oil systems require lower pressure. Most thermal oils operating below 600°F do not require any vapor pressure, and the maximum system pressure is only that generated by the centrifugal circulation pump. Even high-temperature synthetic heat transfer fluids operating up to 750°F require less than 100 PSIG of vapor pressure, while steam systems require more than 3,200 PSIG of operating pressure to reach 750°F.

Comparison of application scenarios

Applications for steam boilers

Steam boilers are indispensable in industrial processes that require steam. For example, in the power generation industry, steam is a key power source that drives turbines to generate electricity; in the food and pharmaceutical industries, steam is used to sterilize and disinfect products to ensure hygiene and safety; and in the apparel manufacturing industry, steam is used in the curing and ironing process to improve product quality.

Application scenarios of thermal oil boiler

Thermal oil boilers are more suitable for processes that require heat but not direct steam. In the chemical industry, such as polymerization and condensation and other chemical reactions, the need for precise temperature control, thermal oil boilers can meet this demand; in the oil refining industry, the heating process in the distillation tower is also often used thermal oil boilers; in the process of plastics and rubber manufacturing, as well as the heating of the edible oil industry, the thermal oil boiler also plays an important role.

Summary of the advantages of the two boilers

Advantages of thermal oil boilers

The thermal oil boiler has several significant advantages. Firstly, it is capable of heating thermal oil to temperatures of up to 300 degrees Celsius or more without the need for high pressure in the system. This feature avoids the risk of high pressures that steam systems have to endure in order to reach high temperatures. Secondly, because they do not need to operate under high pressure, thermal oil boilers present a lower safety risk, with the risk of explosion significantly lower than that of water and steam boilers. Further, by using thermal oil, the system does not form scale in the piping and equipment as it does in steam boilers, reducing the problems of reduced efficiency, increased maintenance requirements and higher costs due to scale. The lower risk of corrosion and lack of scale formation makes thermal oil boilers typically last longer and cost less to maintain than steam or hot water boilers.

Advantages of Steam Boilers

Steam boilers also offer many advantages. Modern steam boilers efficiently convert energy into steam, thereby reducing fuel costs and saving energy. They are used in a wide range of applications across a number of industries, including textiles, food, chemical, pharmaceutical and energy, and can be used for a variety of purposes, including heating and sterilizing. Steam boilers that use electricity or natural gas as fuel are characterized by low emissions and meet environmental requirements. Steam boilers are able to generate large amounts of steam in a short period of time, which is especially beneficial for industrial processes where steam is in high demand and time is of the essence. Steam boilers made of high-quality materials have a long service life and high reliability, which can be further extended through regular maintenance. In addition, state-of-the-art steam boilers are equipped with automatic control systems that allow the user to easily control temperature, pressure and steam flow. At the same time, steam boilers are available in a wide range of fuel options, including solid, liquid, gas, and electric power, allowing companies to choose the most economical fuel solution based on their actual situation.

Conclusion

There are many differences between thermal oil boilers and steam boilers in terms of operating principles, cost, safety, temperature control, energy efficiency, environmental impact, temperature and pressure capabilities, and application scenarios, and each has unique advantages. When choosing which boiler to use, companies need to consider their own production process requirements, budget, safety standards, environmental requirements and other factors.

Before making a decision, it is recommended that enterprises and professional boiler suppliers or industry experts for in-depth communication to ensure that the selected type of boiler can maximize the long-term development to meet the needs of enterprises, to achieve efficient, safe, economical and environmentally friendly production operations.