Selection of container material
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The medium is 85–90% sulfuric acid, with various organic substances and water present; the proportions of these components are 5–8% and 3–5%, respectively. The operating pressure is 0.6 Mpa, and a negative pressure exists during the production process, amounting to around 1 M water column. The material must be able to withstand temperatures of 250 degrees as well as temperature fluctuations. The volume of the container is 8–10 cubic meters. Coiled tube heating using heat transfer oil is employed, along with agitators; after the reaction, the material turns into a solid state, and the agitators must be capable of stirring it. This is an intermittent operation. Please select material
Titanium or titanium composite plates are used, along with all-titanium stirrers. Considering both safety and market prices, using titanium composite plates may be a safer and more cost-effective option； Duplex steel 2205 can also be considered (the manufacturing cycle may be shorter), but it is necessary to ensure the proportion of the duplex phase in the material, especially in the welds.
Try using (carbon steel + PTFE PFA coating).
Our workshop currently has a dozen or so such devices: enamel-lined mixers with external tube heating, available in capacities ranging from a few cubic meters to several dozen cubic meters! Looking at the label, the medium is 85% sulfuric acid.
Non-metallic materials cannot withstand temperatures of 250 degrees! If it’s possible to lower the boiling point by reducing pressure (by increasing negative pressure), then non-metallic materials can be utilized. I would like to ask what kind of solid is formed after the material evaporates and reacts (crystals, or a solid mass)?
Enameling should work fine; it can be used with sulfuric acid of any concentration at temperatures below 260 degrees.
1. High-silicon cast iron: It exhibits good corrosion resistance to sulfuric acid at all concentrations and temperatures up to the boiling point, but its mechanical properties are poor; owners would need to use agitators, which is likely not a practical solution. 2. Titanium and titanium alloys: They are not suitable either due to the high corrosion rate in sulfuric acid at concentrations of 85–90%. 3. Tantalum: It exhibits good corrosion resistance to sulfuric acid at concentrations of 75% or less. 4. Ceramics are resistant to sulfuric acid at all temperatures, with a temperature tolerance of up to 200 degrees. 5. Like glass and ceramics, it can withstand temperatures of up to 300 degrees, but due to issues related to molding and stress variations, it is not suitable for use in this application. Glass is mainly used in pipelines.