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How harmful is fouling to industrial boilers?

How harmful is fouling to industrial boilers?

Industrial boilers are one of the necessary equipment in many industrial industries. The high-temperature steam output by the boiler and the heat it brings can provide a source of power for the industrialized process. Zhengzhou Fangkuai Boiler Factory, as a company with many years of cooperation experience in the field of industrial boilers, has a lot of knowledge about boiler operation, maintenance, and maintenance. Today, I will tell you how much damage is caused by scaling to industrial boilers.

First of all, after the formation of scale inside the industrial boiler, the heat transfer performance of the heating surface becomes poor, and the heat released when the fuel is burned cannot be quickly transferred to the boiler water; therefore, a large amount of heat is taken away by the flue gas, causing the exhaust gas temperature to rise and increase The heat loss of exhaust gas reduces the thermal efficiency of the boiler.

Secondly, it may cause overheating and low strength of the metal, endangering safety. The steel used for the heating surface of industrial boilers is generally carbon steel. During use, the metal wall temperature is allowed to be below 450 ℃; when the boiler is in normal operation, the metal wall temperature is generally below 280 ℃. When there is no scale on the heating surface of the boiler, the metal can quickly transfer heat to the water after being heated. At this time, the temperature difference between the two is about 30 ℃. However, if scale accumulates on the heated surface, the temperature difference between the two will increase. For example: when the heating surface of a boiler with a working pressure of 1.25Mpa has 1 mm thick scale (mixed scale), the temperature difference between the metal wall and the boiler water will reach about 200 ℃; when the scale reaches 3 mm, the metal wall temperature will rise to 580 ℃, far exceeds the allowable temperature of steel. At this time, the tensile strength of the steel will be reduced, and the pressure components of the boiler will overheat, bulge, deform, leak, and even explode under the action of internal pressure. The measured data shows that the metal wall temperature increases as the scale thickness increases. The thicker the scale, the higher the metal wall temperature, and the greater the probability of accidents.

The water circulation of industrial boilers has two forms: natural water circulation and forced water circulation. The natural water cycle is a water cycle that relies on the pressure difference caused by the difference in the specific gravity of soda and water in the riser pipe and the down pipe. Forced water circulation depends on the mechanical power of the water pump to force the circulation. Regardless of which form of water circulation, it is designed and calculated, which means that there is enough circulation cross-sectional area. When scale builds up on the inner wall of the furnace tube, the circulation area in the tube is reduced, the flow resistance increases, the normal water circulation is destroyed, and the metal wall temperature toward the fire surface rises. When the pipeline is blocked by scale, the water circulation is completely stopped, and the metal wall temperature is higher, and pipe burst accidents will occur for a long time.

Once the industrial boiler scales, it must be removed quickly, so as to ensure the safe and economical operation of the boiler. The later the scale builds up, the more medicine is consumed, and the more money is invested. For example, if the average fouling of a 1t/h boiler is 3 mm, 0.5 tons of chemicals are required to remove the fouling once. After increasing according to the different boiler tonnage, the required reagent will increase by one-third, and the investment capital will increase accordingly.

The service life of general industrial boilers can run continuously for about 20 years under normal use conditions. However, most of the boilers of the current use units have not reached this life. There are many reasons for this, one of which is the influence of scale. The drum has a bulge, and after digging and repairing it, it should be properly reduced in pressure to ensure safety. In this way, for units that require high steam pressure, they have to replace a new boiler.

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