Pump selection for sodium carbonate methanol solution
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Our company uses methanol with a concentration of approximately 99%. After mixing sodium carbonate into the methanol solution and stirring it thoroughly, it is pumped through a pump. Currently, it’s basically 4 tons of sodium carbonate and 6 tons of methanol. Since the solubility of sodium carbonate in methanol is very low, most of the sodium carbonate remains in granular form; moreover, there is a possibility that lumps of alkali may also be present. Now, I would like to ask all the experts: from a safety and convenience standpoint, what kind of pump would be most suitable?
Considering that methanol is a flammable and toxic substance, it is necessary to use leak-free pumps for safety reasons. The main types of leak-free pumps available at present are canned pumps and magnetic drive pumps. Among canned pumps, there is a type with external cooling and slurry separation capabilities that can meet the requirements of such applications; magnetic drive pumps can also fulfill these needs. However, considering that solid sodium carbonate particles can wear out components such as the rotor, this may lead to high maintenance costs. In fact, methanol itself isn’t very hazardous. At the concentration you mentioned, it would be perfectly fine to use a stainless steel pump with an open impeller. This is how we’re using it currently.
Stainless steel pumps are prone to problems; if there’s any friction, it can lead to serious issues. Are there any wear-resistant screw pumps or something similar?
It’s better not to consider magnetic drive pumps for this kind of application; they break down as soon as they’re used, so there’s no point in repairing them. Is it possible to use a semi-open impeller centrifugal pump, the type with a liner? What considerations led the OP to choose a screw pump?
The poster can opt for an open-impeller centrifugal pump. The key considerations are the choice of materials and seals. The materials should be corrosion- and wear-resistant, such as CD4MCu. For seals, double seals or tandem seals made of hard-to-hard materials can be chosen!
For this pump, it is recommended to use a magnetic drive pump. It requires no external flushing, can handle environments with solid particles without any issues, and is easy to maintain. If you’re interested, I have a complete solution available; please feel free to contact me!
Primarily from a safety perspective, if it has a mechanical seal, there’s a risk that the seal might get damaged, leading to direct friction between the seal and the shaft; this could ignite the methanol, which would be problematic.
The impeller suitable for this material is essentially determined to be an open impeller, but there is still no clear idea as to what type of pump to use. In terms of mechanical seals, the main concern is the potential hazards that may arise from dry running due to damaged mechanical seals.
We used magnetic pumps before; perhaps the quality of the manufacturer we chose wasn’t very good, as they became unusable in less than half a year. Currently, we’re also considering magnetic pumps, which are relatively safe.
For solid particles of what size, a hose pump can be considered; it doesn’t leak
Hose pumps have no impellers, so the aforementioned problems do not occur