How to choose a boiler with high temperature heating? Difference between Thermal Oil Boiler and Molten Salt Boiler

April 06, 2021

In some special industries, it is necessary to use a high temperature above 200℃, or even four to five hundred degrees. However, the pressure and temperature of the traditional boiler are directly proportional, and it is difficult to reach a temperature above 300℃.

In the "boiler circle", molten salt furnaces and thermal oil boilers are called high-temperature heating boilers. When choosing a high-temperature heating boiler, many people will encounter this problem: Is it better to use a molten salt boiler or a thermal oil boiler?

Both have their pros and cons. First of all, let us understand the working principle and product characteristics of molten salt boiler and thermal oil boiler, and then make the right choice according to the difference between them.

The working principle of molten salt boiler

The gas-fired molten salt boiler puts the powdery deep salt into the melting tank, and it is heated and melted by the high-pressure steam heating tube or electric heating tube installed in the tank. The viscosity of the molten salt heated in the tank can be circulated by a circulating pump. After the entire system is in a fluid and circulating state, it is pumped to the heat carrier furnace to further circulate and increase the temperature to reach the usable temperature.

Features of molten salt boiler

Advantage

1. It can obtain higher working temperature under lower operating pressure, and can be used as high temperature heat source below 500℃.

2. The heating temperature is stable, and the load-temperature adjustment can be performed accurately. It can operate stably in the adjustable load section and has automatic operation control and safety monitoring devices.

3. Closed circuit heating, high heat utilization efficiency and remarkable energy saving effect.

Disadvantages

1. Molten salt is solid at room temperature and must be preheated before starting. When the boiler is shut down, all the molten salt in the system must be returned to the storage tank. Therefore, it is more complicated to start and stop the boiler.

The working principle of thermal oil boiler

The organic heat carrier (heat transfer oil) is used as the heat transfer medium, and the heat transfer oil is forced to circulate in the system through the high temperature oil pump, so that it is heated repeatedly, so as to meet the purpose of continuously obtaining the required heat energy by the heat-requiring equipment; and Meet the requirements of process temperature set in the production process and high-precision temperature control.

Features of thermal oil boiler

Advantage

1. The thermal oil boiler system can use any liquid and gas fuel, and the thermal efficiency is above 90%;

2. The operating pressure of the thermal system of the thermal oil boiler is low, and the system is safe and reliable;

3. The thermal oil boiler system is generally supplied by skid-mounted, simple installation and no special foundation is required;

4. The medium of the thermal oil boiler system is not corrosive to the equipment. When the temperature is lower than 300℃, the thermal oil can be used continuously for more than 10 years without any quality change;

5. The thermal oil boiler system is simple to operate, maintenance-free, and can be fully automated and unattended;

Disadvantages

1. The maximum temperature of the thermal oil boiler is about 320℃. Generally, the heating equipment above 300℃ must use the molten salt boiler. However, EPCB's thermal oil boiler can reach a maximum of 420°C. Some users have already started operation of the thermal oil boiler, and the effect is not bad. Details:

Compare the difference between molten salt boiler and thermal oil boiler

1. Thermal efficiency comparison

Under the same temperature demand, the thermal efficiency of a thermal oil boiler is similar to that of a molten salt boiler with the same fuel. The thermal efficiency of the molten salt boiler is slightly higher than that of the thermal oil boiler.

2. Comparison of purchase cost

The price of thermal oil boiler is similar to that of molten salt boiler. Under the same boiler capacity, the price of a thermal oil boiler is slightly lower than that of a molten salt boiler.

3. Comparison of operating cost

Because of the different combustion medium, the fuel price is different, and the operating cost of the molten salt boiler is higher than that of the thermal oil boiler.

4. Use medium comparison

The medium used in the thermal oil boiler is thermal oil, while the medium used in the molten salt boiler is molten salt. This is the fundamental difference between thermal oil boiler and molten salt boiler.

5. Comparison of structure types

The structure of the thermal oil furnace can be horizontal or vertical, while the type of gas-fired molten salt boiler can only be vertical, which is determined by the properties of two different heat carriers.

6. Temperature comparison

Thermal oil boilers can provide temperatures up to 350°C, while molten salt boiler can provide overheating temperatures up to 550°C.

7. Operational comparison.

The startup and shutdown of the thermal oil boiler is a long process, and the molten salt boiler takes longer, because the molten salt is solid at room temperature, it must be waste heat before starting, and the molten salt may be returned to the storage tank when the boiler is shut down.

8. Safety comparison

In the case of system leakage caused by the accident, the thermal oil will burn when it meets the open flame, and the potential safety hazard is greater. In contrast, molten salt boilers are safer.

9. Comparison of applicable industries

The molten salt boiler can provide a process temperature of 180℃～550℃ for melamine, phthalic anhydride, maleic anhydride, acrylic acid, alumina, urea, o-phenylphenol anhydride, cyanide, solid caustic soda, cracked oil, refrigerant and other chemicals.

The thermal oil boiler can provide a process temperature of 300℃ for use in the petrochemical industry, plastic rubber, leather industry, textile printing and dyeing, painting and paint, wood processing, papermaking and printing, building materials, pharmaceutical industry, metal processing, food industry, etc.

Conclusion:

The exhaust gas temperature of the thermal oil boiler and the system molten salt boiler system is very high, especially the molten salt boiler system can reach a maximum of 550°C. I strongly recommend that you purchase a waste heat boiler whether you are buying a thermal oil boiler or a molten salt boiler. The waste heat boiler can be used to produce hot water, steam or power generation. The boiler system equipped with a waste heat boiler can achieve a higher thermal efficiency of 90~98% (according to the fuel oil condition).

When buying a boiler, you should consult an engineer and then determine which boiler to choose. I hope this article will enable you to understand the difference between a thermal oil boiler and a molten salt boiler, and will help you in the process of choosing a boiler.