Seeking advice on autoclave material issues

According to the conditions specified on the first floor, this reactor is not a high-pressure reactor but rather a medium-pressure reactor (25x10^5/10^6=2.5 MPa). In accordance with the requirements of HG20581-1998, carbon steel or low-alloy steel can be used, but weld stress relief heat treatment must be carried out. If this equipment has a gas space of at least 0.025 m^3 at its top, it is classified as a category III vessel. Therefore, manufacturers that possess the appropriate qualifications for manufacturing pressure vessels and have the necessary heat treatment equipment can produce this reactor.

Using carbon steel on the 2nd floor is definitely not an option, as chloride ions are present; stainless steels such as 304 and 316L are also not suitable

There’s something wrong with what was said on the third floor – what impact do chloride ions really have on carbon steel? Those ions only have an effect on austenitic stainless steels. As for carbon steel, as mentioned on the second floor, there are points that need further consideration; after all, mixtures containing such media are strong electrolytes that cause severe corrosion of carbon steel. In the past, cast iron and carbon steel were used, but corrosion was a serious problem. Nowadays, alloyed cast iron, stainless steel, titanium, engineering plastics, as well as various anti-corrosion linings and electrochemical protection methods are generally employed to prevent corrosion. As for which company can do it, the original poster might as well ask which ones have done it before. See how it works, and then make a decision

Personally, I think stainless steel definitely won’t work; the chloride ion concentration is high, and alkalis at temperatures over 200 degrees either won’t work； Titanium is also not suitable, as it is at risk of hydrogen embrittlement in strongly alkaline environments ； Carbon steel is widely used for storing and transporting alkalis at temperatures above 80 degrees and concentrations below 30%. However, when the concentration or temperature exceeds certain limits, the rate of corrosion in carbon steel increases rapidly, posing a risk of stress corrosion ； Ceramics, glass, and enamel are not resistant to strong alkalis ； Graphite can theoretically withstand NaOH at all temperatures and concentrations, but the impermeable resin used with it cannot meet the requirements regarding temperature and concentration ； The estimate for FRP isn’t feasible either; at least the resin inside cannot withstand such temperatures. Among metals, gold, silver, platinum, and nickel are excellent alkali-resistant materials; among non-metals, rubber is also a good material ； Some plastics will work as well, but the temperature is limited. Polytetrafluoroethylene (PTFE) has good resistance to alkalis, but a temperature of 220 degrees represents its limit for use; currently, the highest operating temperature for PTFE available on the market is around 230 degrees (or 260 degrees?) It’s unclear); was there any over-temperature during operation? Is there negative pressure? Therefore, careful consideration is needed before using PTFE. So I think the best option to consider is using nickel-based materials for composite panels; although they are expensive, they have a long service life and require no frequent maintenance, making them economical overall ； (Some factories use chemical plating or electroplating with nickel to protect steel equipment in order to save nickel.) ； As long as the quality of the coating is ensured, the service life of the steel can be extended – but I still think there are risks; who can guarantee that the coating is completely problem-free? And how is nickel plating applied to the kettle mentioned here? ) This post was last edited by ekguo on 2009-2-8 17:17 ]

It’s really difficult to choose materials for this item; it will likely require special materials

Using nickel-based alloys also presents problems here, as they are not very suitable for processing composite sheets together with carbon steel

As analyzed above, carbon steel and stainless steel are not suitable; given the properties of titanium, the following issues exist: 1. There is a risk of hydrogen embrittlement in strong alkaline environments； 2. Operating temperature: 220 degrees, exceeding the normal operating range ； Based on this, nickel-based alloy materials such as HC276 and INCOL600 can be recommended. The specific choice of material usually needs to be determined through coupon testing; other methods rely on analytical values or empirical data. If economic costs are a consideration, composite plates made from the aforementioned materials can also be used. It should also be noted that nickel-based alloys are required for mixing devices and seals in reaction vessels. Nanjing Baose Co., Ltd. is a company that recommends such materials

:lol:P:P:P:P

Under these operating conditions, neither Hastelloy C-276 nor Inconel 625 is a suitable material, as stress corrosion can occur easily under such conditions! Pure nickel also doesn’t work; it has very poor corrosion resistance in alkaline solutions with high chloride content! In this operating condition, the most suitable material is zirconium, but it is expensive; titanium is not suitable as it poses a risk of hydrogen embrittlement and may also suffer from pitting (due to high chloride levels and temperatures above 124 degrees), although a titanium-palladium alloy can be used