Corrosion of the ulcerated surfaces in the heat exchanger tubes of the alkylation reactor
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1. Basic information on the equipment: The alkylation reactor R-2201ABC has dimensions of Φ2300×14000 mm. Its tube bundle is of the U-tube type, with specifications of Φ1600×11300 mm; there are a total of 615 tubes in this bundle, made of 10# material. The rear side of the equipment is equipped with a mixing tank, while the front side features a U-tube type heat exchange tube bundle. An inner sleeve is present inside the equipment, and the tube bundle is installed within this inner sleeve. 2. Operating conditions (1) Shell side: The medium in the shell side is a mixture of hydrocarbon feed and sulfuric acid, where the hydrocarbon feed consists of olefin feed and recycled coolant; the media involved are degassed butane, recycled isobutane, and recycled coolant. The sulfuric acid is 90-93% pure. The mass ratio of hydrocarbon oil to sulfuric acid in the shell side is 34.6% for hydrocarbon oil and 65.4% for sulfuric acid; the flow rate is 42-48/h. The temperature at the inlet of the shell side is 2-3°C, while the temperature at the outlet is 7.48°C. The pressure in the reactor’s shell side is 0.51-0.57 MPa. (2) Tube side: The tube side product is the reaction product, with media including isobutane, C3 hydrocarbons, n-butane, alkylated oil, and dimethyl ether. The flow rate in the reactor’s tube side is 49 t/h, the operating temperature is 5°C, and the operating pressure is 0.05 MPa. 3. The corrosion mainly occurs on the outer wall of the tube bundle, with sulfuric acid playing a key role in this process. Severe ulcerative corrosion appears on the surface of the heat exchange tubes; this problem usually occurs after about half a year of use. Take a look at what good anti-corrosion methods are available
A common problem in the heat exchangers of alkylation reactors is corrosion of the tube bundle surfaces caused by sulfuric acid during operation. Here are some feasible anti-corrosion measures: 1. Material selection: – It is possible to consider using materials with greater acid resistance, such as titanium or high-nickel alloys (e.g., Hastelloy C-276), which can better resist corrosion by sulfuric acid. 2. Corrosion-resistant coating: Applying a corrosion-resistant coating with strong acid resistance to the surface of the tube bundle, such as an epoxy resin coating or a polyurethane coating, can effectively prevent direct contact between the medium and the metal. 3. Cathodic protection: – Cathodic protection technology is used to maintain the heat exchanger tubes at a more negative potential by applying an external current, thereby slowing down or preventing corrosion. 4. Adjustment of operating conditions: – Reduce the concentration of sulfuric acid in the shell side and increase the operating temperature to reduce the corrosion rate. - Adjust the flow rate and operating pressure to minimize the erosion of the pipeline walls by the medium. 5. Regular inspection and maintenance: – Regularly check for corrosion in the heat exchanger tubes, and promptly clean them or replace those that are severely damaged. - Implement a strict maintenance plan, including regular chemical cleaning and inspections, to extend the equipment’s lifespan. By implementing the above methods, the corrosion of the ulcerated surfaces on the heat exchange tube bundles in the alkylation reactor can be effectively reduced. .
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Generally, Hastelloy or enamel can be used, right?