Corrosion-resistant screw vacuum pump
Thread Content
In recent years, the domestic screw pump market has developed at a rapid pace, and its use in the chemical industry has also increased significantly. Currently, various manufacturers offer different types of corrosion-resistant screw pumps. These can be divided into two main categories: those with coatings (including Teflon coatings, Hastelloy coatings, PEK coatings, etc.), and those whose screws are made directly from corrosion-resistant materials (such as duplex steel, ferritic stainless steel, and titanium). Everyone has used that type; is there any direct comparison between them, and which one is more suitable for chemical processing environments?
First of all, manufacturers are already using duplex steel screw pumps; it’s been two or three months now, in hydrogen chloride environments, the rotors have completely worn out； Titanium? Let’s not talk about how durable they are for now; let’s first consider whether they’re affordable. A liquid ring pump costs 700,000 yuan, and it seems to have a power consumption of around 18.5 KW. How much does a titanium screw pump cost? How many can afford it? I’m not sure how long a screw pump with a Hastelloy lining will last, but Hastelloy Roots pumps generally last about half a year under normal operating conditions; after that, they need to be sent back to the factory for re-coating. Coatings work well on liquid ring pumps, as these pumps are designed to be more robust, whereas screw pumps are quite delicate. I’m not entirely sure about Teflon coatings or PEK coatings in the case of screw pumps
The price of titanium screws for screw pumps doesn’t seem to be high; as far as I know, there are established manufacturers producing them, and the prices are relatively acceptable. However, the issue of hydrogen chloride is really difficult to address; the temperature inside the screw is also high. At present, it seems that the best approach is to find solutions through process optimization, as relying solely on corrosion-resistant materials is quite challenging.
We use screw vacuum pumps quite often; corrosive gases containing air and condensate are not very suitable for them. It can be used only when proper upstream protection is in place. The material we use is quite ordinary – nickel-plated cast iron – and it performs satisfactorily when used in nitration waste sulfuric acid and nitric acid-containing waste phosphoric acid. Rotary screw compressors are required for the high-concentration sulfuric acid project.
In my opinion, using metal materials with hydrochloric acid is like using a meat ball to fight a dog: lol. For applications involving hydrochloric acid, non-metallic materials must be used, as they are cost-effective and available in sufficient quantities:victory:
Firstly, at rest and under non-frictional high temperatures, non-metallic materials do offer good cost-performance for resisting chloride ion corrosion; but what about components used in driven or transmitting equipment?
Even with media such as hydrochloric acid, titanium materials may not be suitable for use. However, we do have a solution for screw vacuum pumps. Although those we use are also cast and coated with an anti-corrosion layer, the special coating we employ boasts advantages such as wear resistance, high-temperature resistance, strong corrosion resistance, and the ability to remain in place without peeling off. The greatest advantage of using this coating is... First, cost. Second, it’s cost; third, it’s still cost. . .
Corrosion is not just a material issue; addressing it at the source of the manufacturing process or through engineering solutions can be more effective than simply replacing the materials. Screw vacuum pumps operate at relatively high temperatures, and there are very few materials that can withstand corrosive gases under such conditions.