The internal structure of the equipment when dehydrating materials using molecular sieves
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Hello everyone, our company is now preparing to install a vertical equipment for molecular sieve dehydration (moisture content <10ppm), DN600, cylinder section 3000mm, and elliptical heads at both ends. The upper and lower heads have hand holes for loading and unloading molecular sieves respectively. After the molecular sieve is installed in the cylinder, the material enters from the lower head through the metering pump and is discharged from the upper head with a flow rate of 120L/h. We are now worried that during actual use, a phenomenon similar to turbulence will occur. At a slow flow rate, materials in the middle of the cylinder can flow smoothly, but few materials will flow through the molecular sieve within the inner wall of the cylinder. How much molecular sieve actually plays a role in dehydration depends on the normal distribution form of the material when it flows in the vertical direction. If the peak top and peak bottom are similar, it can basically meet the dehydration needs. ； If the difference is large, it will cause dehydration failure and frequent regeneration of the molecular sieve. Now we have made changes to it, that is, adding an orifice plate and annular pressure ring to the lower head and cylinder section, and using stainless steel wire mesh to distribute the material for the first time before entering the molecular sieve. We planned to add the same distributor to the middle section of the cylinder for secondary distribution of the material. However, we gave up because of the installation size and the inconvenience of assembly and disassembly of the molecular sieve. Do you think there will be a normal distribution inside this dehydration equipment? If so, what kind of distribution would it be? Is it possible to add a distributor? Is there a better way to improve it? I hope you will feel free to enlighten me and participate in the discussion.
Still no reply, how can I change the discussion to asking for help...
There will be no turbulence at your speed. There is already an orifice plate underneath as a distributor. No need for the middle. If you want better results, you can lay a layer of 15 cm high inert porcelain balls with a diameter of 10-12 mm before installing the molecular sieves. Place a layer of wire mesh on the porcelain balls and install the molecular sieves on top. That also plays a better distribution role.
In the process of imagining the extremely slow rise of the liquid, after the molecular sieve it has just contacted is saturated, will the liquid move closer? It is basically a process of rising vertically along the molecular sieve in a small space? If the flow rate increases, will the liquid be spread wider? In addition, when the flow rate is small, will the liquid change its vertical upward form under the action of gravity? How much influence does gravity play in liquid distribution? The biggest worry now is that the utilization rate of the molecular sieve in the equipment is low. It needs to be regenerated before more than half of it reaches saturation, which will seriously affect production.
The normal distribution of liquid flow rate you mentioned corresponds to an empty pipe. Now that the equipment is filled with molecular sieves, the flow channel is actually countless winding gaps. You can see how the relevant content of filtration in chemical engineering principles handles this situation. In short, it is unlikely that the situation you mentioned will occur. Once the initial distribution is done, there should be no big problem.
“Regeneration is required before more than half of it reaches saturation, which will greatly affect production. Whether or not regeneration is needed can be judged from the moisture content of the exported materials. Regeneration will occur when it is greater than a certain value. There will always be a gap between design calculations and actual application conditions.
To be on the safe side, molecular sieves need to be regenerated when the water content is generally around 8ppm. I hope that the distributor added below can achieve a very uniform distribution effect, and I also hope that the material can be diffused in an ideal way, completely soaked, and maximize the use of molecular sieves. If you have a glass column with a large enough diameter, you can do an experiment. After setting the flow rate, carefully observe how the flow goes. . .
Sir, it is best to install a moisture meter that can analyze moisture online. It is the safest way to regenerate when the outlet reaches a certain level of moisture. If it is too expensive to buy instruments, the only option is to take samples and analyze the water content every day. By the way, have you done the molecular screening? I make molecular sieves. You can contact me. QQ: 53748807