Batch chemical plants handle a large amount of powder.
Powder, powder here and there…
If you construct piping using the same concept as for gases and liquids, you will definitely fail.
I’m stuck and there’s nothing I can do
This problem was only noticed once production started.
At that time, there is nothing the equipment shop can do, and they will only receive complaints.
I feel helpless.
To avoid such painful experiences, we have summarized the basic concepts of powder piping to avoid failures at the design and construction stages.
Characteristics of powder
We will introduce the characteristics of powders handled in batch chemical plants, with a focus on piping design.
Powder is clogged
Anyone who has ever handled powder will understand this.
Or rather, wouldn’t Japanese people use table pepper when eating ramen at home? That is very easy to understand.
To add pepper, turn the pepper upside down and shake the container. I thought the pepper wouldn’t fall out, so when I checked inside the glass container, it appeared to be clogged.
The same thing can happen with powder in pipes.
Of course, it depends on the type of powder. What kind of powder is handled in a chemical plant? It is difficult to generalize as it depends on the.
However, batch chemical plants are designed with the assumption that they will clog. I get suspicious.
Powder dances
The powder will fly.
Just like pepper and flour, the powders handled in batch chemical plants fly around. It is a fine powder.
It doesn’t just clog , it dances.
This requires a dedicated dust collection line.
How to transfer powder
When transferring powder, gravity fall is the basic principle.
When do you need to transfer powder?
- Powder is placed in a reaction vessel containing liquid in advance.
- Transfer the powder produced in the container to another location
Simply put, that’s about it.
The reality is that we want to avoid handling it as a powder as much as possible.
There are not many ways to transport that powder. Let’s briefly consider the steps to take after transferring the powder in the paper bag to a container.
- Throw it into another device under its own weight.
- Transfer to another device using a mechanical screw, etc.
- Transfer by force using compressed air, etc.
Among these, dead weight is the most important principle.
Mechanical screws require the purchase of equipment, and compressed air requires power.
There are other reasons besides this, but the above understanding is sufficient as a basic idea.
There’s nothing better than a low-cost self-weight drop.
Dead weight falling piping is straight
If powder tends to clog easily, piping should be designed to avoid clogging as much as possible.
Specifically, drop it straight .
A rotary valve secures a constant amount of feed while dropping by its own weight.
So far it’s a simple story. However, in reality, there are many cases where this is not the case.
Looking at the site, most of the dead weight drop piping is distorted.
The reason is quite simple.
- Because proper instructions were not given during installation work.
- Because the piping diagram doesn’t give proper instructions.
- This is because they have not considered what to do when the center of the equipment that connects the piping is shifted.
When updating equipment at a site like this, be sure to take appropriate measures.
- The position of the equipment foundation is determined using a laser so that the position of the equipment does not shift.
- After the foundation work is completed, on-site verification will be carried out before equipment installation.
- Instead of forcing the pipes to deform and connect them when they become misaligned, use expansion joints to connect them.
If you don’t take these measures, the construction will progress and you will realize at the end that distorted equipment has been installed.
Once the process has progressed to this stage, it is the customer, the operator, who is in trouble.
Both machine shops and drawing shops must remember this principle.
dust collection line
Powders handled in batch chemical plants fly around and must be collected.
This is absolutely necessary when transferring powder by gravity fall.
If you do not do this, you will be covered in powder.
This is not only a problem in terms of product loss, but also in terms of environmental health for workers.
Collect powder with a suction-type dust collector.
There are several types of dust collectors, and there are many problems.
When designing piping, flow velocity design and flange notch are important.
In particular, if the flange cut depth is not carefully considered, it will be impossible to clean or unblock the dust collection line.
Reasons to avoid pneumatic transport of powder
Pneumatic transport is not used to transport powder in batch chemical plants.
Since pneumatic transportation has a common image among the general public, we will look at the advantages and disadvantages of pneumatic transportation and explain the reasons why pneumatic transportation should be avoided.
merit
Pneumatic transportation has the following advantages over mechanical transportation.
- Lines are concise
- No dust scattering or foreign matter contamination
The reason why the line is concise is that it can be transported by piping.
There is no need to install large machines.
With piping, there is a high degree of freedom in construction, and transportation lines can be kept compact.
Since it can be transported via piping, it is easy to control dust scattering and foreign matter contamination.
Demerit
There are many disadvantages to air transportation.
- high cost
- cause static electricity ignition
- block
The cost is high because the power cost for pneumatic transportation is high.
It takes more power to create air to feed that volume of powder than to feed that volume of powder using a motor.
Most of the powders handled in batch chemical plants are organic substances.
That is why powders handled in batch chemical plants are prone to static electricity buildup.
Blockage is also a scary factor in air transportation.
Although there is a possibility of blockage with mechanical or hydraulic transportation, we believe that pneumatic transportation is one rank higher in danger.
The reason is that it uses compressed air.
If a blockage occurs during transportation, compressed air will be present in the pipes.
When attempting to disassemble the pipe to remove the blockage, compressed air is suddenly released into the atmosphere.
When the compressed air pressure is removed, the air expands rapidly.
Things to consider for powder piping
Here is a summary of things to consider when designing powder piping.
Consider the following model.
We are considering the case where powder falls under its own weight using a commonly manufactured pipe.
Let’s line up the elements that block the powder.
- piping is installed at a slope, it will accumulate.
- surface of the piping is rough, it will accumulate.
- inner diameter of the gasket is smaller than the inner diameter of the pipe, it will accumulate.
- there is too much welding wave from the piping, it will accumulate.
These are things that come to mind when trying to eliminate buildup from a geometric perspective, but they tend to be forgotten when trying to design piping.
Installation slope
If the piping is not installed vertically but on a slope, there is an element of accumulation.
If the pipes are installed horizontally, almost no flow will occur.
Even if the pipe has a slope, whether or not it will flow will depend on the size relationship with the angle of repose of the powder.
If you want to have a multi-purpose idea, it would be a good idea to install the piping in a completely vertical direction.
It’s okay for a little while.
If you tilt the piping because of this kind of indulgence, there is a high probability that you will regret it.
When installing equipment, determine the equipment position and nozzle position so that the piping is vertical.
Normally, the piping is connected after the installation location of the equipment has been determined, so the design order is reversed.
Surface roughness
The surface roughness of piping can also cause powder to accumulate.
However, in rare cases this becomes a major factor.
Other factors are far more influential.
To reduce surface roughness, use buffing or processed materials.
Both polishing and processed materials can extend delivery times and increase costs.
I would like to use it while determining the effect of surface roughness.
Gasket inner diameter
If the inner diameter of the gasket is smaller than the inner diameter of the pipe, it will naturally accumulate.
Even for slurry-based gaskets, careful attention is often paid to the inner diameter of the gasket, so many engineers are probably aware of this.
However, even on lines where dry cakes fall under their own weight, there are cases in which the inner diameter of the gasket is not taken into consideration.
If you see these lines, replace the gasket.
Welding Uranami
The back waves of welding are also a source of powder accumulation.
Even if you do buffing, it takes a lot of effort to completely remove it.
It can’t be helped if some unevenness remains.
If you’re going to get hung up on this, you should probably pay more attention to the slope of the piping and gaskets.
Longitudinal welding can be prevented by seamless piping, but circumferential welding with flanges, elbows, etc. cannot be prevented.
Especially for piping with many elbows, it is difficult to visually monitor the back waves at each weld.
reference
Powder piping is notorious for its many troubles.
Try to keep the piping simple to avoid problems as much as possible.
Related article
If you want to know more, check out the article below.
Related information
lastly
We explained the concept of powder piping in batch chemical plants.
Powder will clog and fly around. Powder transport is basically carried out by falling under its own weight, and pneumatic transport is generally not used.
When designing powder piping, consider factors such as slope, surface roughness, gasket inner diameter, and wave.
Please feel free to post any concerns, questions, or concerns you may have regarding the design, maintenance, and operation of chemical plants in the comments section. (The comment section is at the bottom of this article.)
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