Ensuring optimal pressure for cement pneumatic conveying
How to choose a compressed air system for cement pneumatic conveying ?
Since wet cement is a sticky material, it's important to properly remove it from a storage silo in a processing plant. This is made possible through pneumatic conveying, which uses compressed air to push cement through piping. Keeping this in mind, it's important to use the right air pressure and equipment.
That’s because pneumatic conveying in a cement plant is a low-pressure application. While medium to large air compressors are relevant for many industrial applications, cement plants rely heavily on low-pressure equipment (<4bar(g)), mainly for pneumatic conveying, fluidization, and combustion air. In fact, around 70% of the installed power needed for compressed air in a cement plant goes to low-pressure compressors and blowers (< 4 bar). Of the low-pressure cement applications, pneumatic conveying requires the most power (40%).
Low-pressure compressed air equipment
When it comes to low-pressure compressed air equipment for pneumatic conveying, the traditional solution is a lobe (Roots) blower. However, a screw blower tends to be 30% more efficient. This is because of its design, based on the principle of isentropic compression, covered in our article on types of blowers.
When considering overall operational costs, compressed air equipment makes up most of your energy consumption. Investing in more efficient equipment, like a screw blower, will save you money in the long term. Typically, these machines pay for themselves throughout their lifespan.
You’ll also want to pay make sure your equipment matches the actual pressure level needed. Using equipment that’s too big or too small can result in inefficiencies. Otherwise, you’ll negate the benefits offered by low pressure machines.
The right pressure for pneumatic conveying
There are 2 ways of pneumatic conveying. One is called dilute phase, which requires pressure levels up to 0.3-2.5 bar(g). This is used for materials with a low bulk density. The other type is called dense phase. This needs pressure levels of 1.5-4 bar(g). The exact pressure needed depends on the design of the system.
With this, it’s important to finetune your air pressure. Often, facilities will install a medium air compressor with 7-8 bar(g) of pressure and use a reducing valve. However, with this method you lose around 7% of energy efficiency for each 1 bar(g) of pressure drop.
This is why it makes more sense to use a dedicated blower or compressor. Using the right equipment can save a lot of energy. Additionally, a dedicated unit per conveying line reduces the risk of clogged pipes caused by a sudden pressure drop in the general compressed air net.
Choosing the best equipment
Like with any compressed air equipment, you'll want to conduct a thorough sizing assessment. This will help you understand the pressure levels needed. Our team is available to offer advice on sizing, free of charge.
