graphitization petroleum coke

Pubdate: 07-30 2021

Graphitic cathode carbon block solves the problem of boiler sulfur corrosion protection

graphitization petroleum cokegraphitization petroleum cokegraphitization petroleum coke

The sulfur corrosion of the boiler refers to the corrosion of the boiler by the combination of the water vapor in the flue gas and the sulfur trioxide generated after the combustion of sulfur. The most common sulfur corrosion is the low-temperature sulfur corrosion that occurs on the heating surface of the boiler tail.

Low-temperature sulfur corrosion often occurs in the cold end of the air preheater and the economizer where the feed water temperature is low. When the temperature of the heating surface is lower than the dew point of the flue gas, the sulfuric acid formed by the combination of the water vapor in the flue gas and the sulfur trioxide generated after the sulfur combustion will condense on the heating surface, severely corroding the heating surface and causing “ash blocking” , Zhisheng Weihua high temperature flue gas anticorrosive coating can effectively solve the problem of boiler sulfur corrosion.

When the flue gas is reduced to the vaporization point, when only water vapor is contained in the flue gas without sulfur trioxide, the flue gas dew point actually refers to the water vapor break point in the flue gas, that is, the condensation of water vapor in the flue gas (condensation). )temperature. This temperature is related to the partial pressure of water vapor in the flue gas. The higher the partial pressure of water vapor, the higher the dew point temperature. The water vapor dew point of flue gas produced by burning different fuels is roughly as shown in the table below.

It can be seen from the above table that the dew point temperature of water vapor in the flue gas does not exceed 50°C, which is much lower than the exhaust gas temperature of the boiler, so it is difficult for pure water vapor to condense on the heated surface.

If there is sulfur trioxide in the flue gas, the situation is very different.

After the sulfur in the fuel is burned, sulfur dioxide is formed. When the excess air coefficient is large, the excess oxygen is large, and the temperature is not too high, a small amount of sulfur dioxide continues to oxidize to form sulfur trioxide:

This reaction is a reversible exothermic reaction, which is difficult to carry out at high temperature and low oxygen content; even if the temperature is not high and the oxygen supply is sufficient, the generated sulfur trioxide is also very limited. Measured data at home and abroad show that the conversion rate of sulfur trioxide (volume of SO3 in flue gas/(SO3+SO2) volume) is 1%~2% for chain grate furnaces; 0.5%~1.5% for pulverized coal furnaces The furnace is 0.5%~1%; the oil burner is 0.5%~2%. The sulfur dioxide in the flue gas has no obvious corrosive effect on the heating surface. Although the content of sulfur trioxide is very small, it can combine with the water vapor in the flue gas to form sulfuric acid vapor, which will significantly increase the dew point temperature of the flue gas. As long as there is a very small amount of sulfuric acid vapor, the dew point (acid dew point) of the flue gas will increase to above 100°C. The increase in dew point temperature means that sulfuric acid vapor may condense when it encounters a higher temperature wall. Acid dew not only corrodes the metal wall, but also causes the ash in the flue gas to condense on the metal wall. The ash accumulates more and more, and finally blocks the smoke.气 Channel.

The long-term on-site research and development personnel of Zhisheng Weihua high-temperature flue gas anticorrosive coating found that in order to avoid low-temperature sulfur corrosion, the following technical measures can be adopted:

(1) Use hot air or steam to heat cold air to increase the air temperature at the inlet of the air preheater, thereby increasing the wall temperature of the preheater to be higher than the dew point temperature.

(2) The low-oxygen combustion method is adopted to reduce the amount of SO3 generated.

(3) Corrosion-resistant materials such as glass and ceramics are used to manufacture cold-end air preheaters. Although traditional glass and ceramic anti-corrosion materials have good anti-corrosion properties, they have poor adhesion, cumbersome construction and difficult subsequent repairs. , Resulting in short service life and poor anti-corrosion effect.

After long-term field research and development, after years of research and experimentation, Zhisheng Weihua scientific research personnel successfully launched ZS-1041 flue gas anticorrosive coating. The main components of the coating are nano powder, ceramic beads, silicon carbide, boron nitride, and fine-crystalline alumina. , Ultra-fine zinc oxide, titanium oxide, etc., made into cermet functional fillers to improve the wear resistance and corrosion resistance of the coating. Use inorganic fibers to enhance the impact resistance of the coating. ZS-1041 flue gas anticorrosive paint coating has the following characteristics: long-term anticorrosion: excellent corrosion resistance, resistance to medium corrosion such as H2S in the flue gas, and resistance to acid and alkali corrosion in flue and other equipment. Wear resistance: Ceramic functional fillers composed of multiple components cooperate to give the coating excellent wear resistance and corrosion resistance. Super adhesion: strong adhesion between the coating and the substrate. The metal oxide nanomaterials and rare earth oxide ultrafine powders contained in the coating composition help the coating form a dense interfacial transition layer and make it comprehensive thermodynamics The nature matches the matrix. High temperature resistance: 600°C heat resistance, long coating service life: Long coating service life, good durability, and damaged coatings can be easily repaired. There is no pollution to the environment in the process of preparation, painting and coating formation.

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