The thermal oil heater, also called organic heat carrier boiler, provides heat energy for production by heating the heat medium oil. It can realize the high-temperature and low-pressure heating without constant water supply. What are the characteristics of the thermal oil heater?
The exhaust gas heat loss of coal-fired boiler is caused by the flue gas removed by final stage heat exchanger. The flue gas will take away a part of heat, mainly including the heat taken away by dry flue gas and the sensible heat with water vapor in the flue gas. What’s more, if the combustible gas in the coal-fired boiler is not completely burned, there will be heat loss as well. Therefore, this kind of heat loss mainly depends on the content of incomplete combustion products in the exhaust smoke.
Influencing factors of slagging on heating surface of boiler
(1) Ash characteristics of pulverized coal
Generally, the softening temperature ST of ash is used as the main indicator of slag formation. Coal with low ash melting point (ST<1200℃) is easy to slag. In addition, the slagging index also includes: silicon ratio, alkali-acid ratio, slagging index, limit viscosity and so on.
（2）Aerodynamic characteristics in the furnace
Improper air flow organization leads to flame center deviation, and the pulverized coal air flow flame adheres to the wall, causing local slagging of the water-cooled wall;
Improper air flow organization, forming flue gas retention vortex area and forming a reducing atmosphere (with CO), reducing the ash melting point and increasing the possibility of slagging.
Excess air coefficient: When the excess air in the furnace is too small, a reducing atmosphere may be generated, and the tendency of slagging will increase accordingly.
（3）Influence of boiler heat lo
Industrial boilers will produce wastes that needs to be treated during the use process, which is what we mentioned of boiler blowdown. What are the methods for boiler blowdown?
1. Regular blowdown
1) The time interval and quantity of discharge depend on the test results of boiler water. It usually do not exceed 5% of the water supply.
2) When the regular blowdown is being made under high load of the boiler, the blowdown of the water-cooled wall header is generally not required to avoid affecting the normal water circulation of the water-cooled wall and forming a tube explosion incident.
2. Continuous blowdown
The amount of blowdown shall be determined according to the test results of the boiler water, and shall be completed by adjusting the needle-shaped angle of the blowdown tube.
Here load means, amount of steam drawn from the boiler. So when the load increases, the specific volume of the steam in the boiler increases reducing the pressure. This inturn demands for more feed water and more amount of fuel to be burnt. So, for any boiler there will be a feed water level control system put in place to measure the water level in drum. As and when the level of water in the drum reduces, the controller sends a signal to the feed water pump to start and stops when the desired water level is reached. This way the steam generation continues to maintain the desired pressure.
Generally, there is moisture in heat medium oil. And, the moisture will be evaporated during the heating process of the oil. If the water vapor is not discharged from the thermal oil heater, it will cause the fluctuation of heat medium oil pressure. However, the oil-gas separator can separate the water vapor from the heat medium oil and discharge it from the heater, which ensures the stable oil pressure.
The dry bottom hopper is formed by bending the lower part of the water wall of the front and rear walls inward. The main function is to gather, cool and automatically discharge ash. It is also convenient for the connection and sealing of the lower header and the ash well.
Biomass-fired boilers need to be shut down for maintenance. Proper maintenance can reduce the damage to the boiler caused by continuous work. Firstly, it is necessary to cut off all power to prevent being struck by lightning. In addition, dust, limescale and carbon deposits should be cleaned up to prevent rust and corrosion of the boiler.
