In the heating furnace process of refineries, the condensation of sulfuric acid vapor generated by the combustion of sulfur-containing fuels is a "hidden killer" that threatens equipment safety and operational efficiency.The acid dew point meter, as a core equipment for accurately monitoring the condensation temperature of sulfuric acid vapor, is becoming a key tool for corrosion prevention and efficiency improvement in the refining industry.

　　1. Sulfuric acid corrosion: the "hidden corrosion threat" of refining equipment

Refinery heating furnaces often use sulfur-containing fuels such as vacuum residue and gas as energy sources. During the combustion process, sulfur elements are oxidized to produce sulfur dioxide (SO ₂), of which 1% -3% is further converted to sulfur trioxide (SO3) under the action of excess oxygen and metal catalysts (such as Fe ₂ O3, V ₂ O ₅). When the flue gas temperature drops below 400 ℃, SO3 combines with water vapor to generate sulfuric acid vapor, and its condensation temperature (acid dew point) can reach 140-160 ℃, much higher than the dew point of pure water. Once the exhaust temperature is below the acid dew point, sulfuric acid droplets will adhere to the surface of the flue and heat exchanger, causing three major hazards: metal corrosion, ash accumulation and blockage, and decreased thermal efficiency. For example, a refinery failed to monitor the acid dew point in a timely manner, resulting in a leakage of the economizer and causing a shutdown for maintenance, resulting in direct economic losses exceeding one million yuan.

　　2. Acid dew point meter: the "smart eye" for precise monitoring

The acid dew point meter achieves real-time monitoring through conductivity sensor technology: a high resistance substrate electrode is arranged on the surface of the probe. When the sulfuric acid liquid film condenses, the conductivity between the electrodes increases, and the temperature corresponding to the current rising to 40-60 μ A is the acid dew point. withChengdu LitongTaking the OFD-1 acid dew point meter as an example, it uses the cooling and heating averaging method to eliminate condensation hysteresis errors, with a measurement accuracy of ± 1 ℃ and a response time of ≤ 60 seconds. It can cover the acid dew point range of -20 ℃ to 150 ℃. In a heating furnace renovation project at a certain refinery, the equipment successfully controlled the exhaust gas temperature to 8 ℃ above the acid dew point, extending the service life of the heat exchanger by 3 years and saving maintenance costs of 2 million yuan per year.

3. Process optimization: from passive response to active prevention and control

The data from the acid dew point meter is not only used for real-time warning, but can also be linked to the combustion control system to achieve closed-loop optimization. By adjusting the excess air coefficient (reducing SO3 generation), controlling the sulfur content of fuel (using low sulfur coal), and optimizing the distribution of flue gas (reducing local low temperature areas), the acid dew point can be reduced by 10-15 ℃. For example, a certain refinery linked an acid dew point meter with a DCS system to ensure combustion efficiency while reducing exhaust gas temperature from 180 ℃ to 165 ℃, increasing thermal efficiency by 1.2% and reducing carbon dioxide emissions by 1200 tons annually.

From passive maintenance to active prevention, acid dew point meters are guarding the "lifeline" of refinery heating furnaces with millimeter level accuracy. With the integration of IoT and AI technology, acid dew point meters will achieve more intelligent predictive maintenance in the future, providing solid support for the green transformation of the refining industry.