Design of high-pressure reactors: material selection issues
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Our company is going to install a high-pressure reactor. The basic operating conditions are as follows: Operating temperature: 300–310°C, pressure: 10–11 MPa. Properties of the medium: The main component is water, with a pH of 9–9.5; it contains approximately 0.5% chloride ions, 1.5% hydrogen peroxide (H2O2), and about 2% ethanol. Plus 10% solid phase material. The volume of the material is approximately 700 L; it needs to be raised from room temperature to the desired temperature within about 3 hours, and then maintained at that temperature for 8–10 hours. I consulted two manufacturers – one suggested using a titanium composite plate with circular end caps on top and bottom, without flanges, and offered a lower price. Another person said that the titanium composite plate did not meet the requirements of the operating conditions, suggesting the use of a Hastelloy composite plate with a flat-top head. The price is high. What suggestions do you all have? Will titanium composite plates work? After all, it’s cheaper. I would appreciate your guidance. Thank you!
With a material volume of 700 L, the diameter of the equipment should be at least DN800. Considering the operating temperature and medium conditions, titanium composite plates can be used. What are the reasons for believing that the titanium composite plate does not meet the operational requirements? Which grade is specified in the quotation for nickel-based alloys?
The salesperson said, “Due to the overall flange-lined tube structure made of titanium, the maximum temperature is 180 degrees, which certainly does not meet your company’s process requirements. There is no issue with pressure, but for safety and durability, we recommend using Hastelloy material.” The substrate is Q345R.
Oh. The maximum operating temperature for titanium composite plates is 350, while the maximum allowable temperature for titanium-lined structures is generally 250. However, the upper limit of operating temperature should be determined based on the main materials and structure; I don’t think temperature is the issue with this device.
If considering welded structures, nickel-based alloys are certainly better. The choice of laminated material depends primarily on the suitability of the medium.
Thank you, I’ve learned something. Do you think that, under our operating conditions, the titanium composite plate should be able to meet the requirements, with perhaps just an increased pressure tolerance for the base material? After all, Hastelloy composite plates are twice as expensive as titanium composite plates.
You’re welcome! I think the pressure and temperature are fine; the substrate is a pressure-bearing component, and as long as its strength meets the requirements, it’s normal to use high-pressure titanium steel composite plates in such equipment. I’m not an expert on materials; based on my limited knowledge, titanium can be used.
If a nickel-based alloy is used, domestic grades can also be chosen; they are cheaper and not necessarily of the Hastelloy type.
Okay, thank you. I consulted a few more companies, and all of them said that titanium composite plates could be used. The prices were exactly half of those for Hastelloy; so I’ll go with titanium after all. It costs hundreds of thousands, haha. Let’s give them a bit more headroom for pressure.
OP, it’s not a matter of designing for extra margin; titanium-steel composites can fully meet the usage requirements. The key aspects of titanium-steel composite plate manufacturing equipment are the source of materials, a reasonable design structure, proper manufacturing and welding processes, as well as the selection of manufacturers with sufficient capabilities and reliable manufacturing techniques; for the materials, it is necessary to use composite plates from reputable manufacturers.
Titanium cannot withstand the corrosion of hydrogen peroxide at this temperature! Moreover, the strength may be insufficient, and hydrogen embrittlement may occur under these conditions!