Whether it’s an air leak or an unoptimized design, there are several factors that can affect the energy efficiency in pneumatic conveying systems. Fortunately, most of these are easily mitigated if you know what to look for. Continue reading to learn how to save energy in pneumatic conveying systems using five simple tips.
Energy Efficiency in Pneumatic Conveying Systems
By default, pneumatic conveying systems are highly efficient at transporting materials. By utilising the kinetic energy of air within a closed system, they have minimal environmental impact and suffer little material loss. With this in mind, pneumatic conveying systems are much more energy efficient than mechanical systems, for example.
However, their high energy consumption can challenge energy efficiency, and this can be compounded by several factors. Leakages and pressure loss, for example, can massively impact the energy efficiency of a pneumatic conveying system by forcing it to work harder to transport the materials. Even oversized components can drive up the system’s energy consumption.
Luckily, there are a few solutions for how to save energy in pneumatic conveying systems, from optimizing their design and choosing the right sized components, to minimizing pressure drops and checking the solids loading ratio.
Optimize the design of your pneumatic conveying system
Improving the energy efficiency in pneumatic conveying systems starts with optimizing the design of your specific system. There are a number of ways you can do this, but here are our top three:
- Ensure pipes and tubes are the correct length and are kept as simple as possible. Unnecessarily long conveying lines with excessive direction changes can increase energy consumption, the likelihood of pressure drops, and, in turn, energy losses.
- Optimize the conveying velocity to ensure it’s at the correct value for the material you’re conveying. If it’s too high, for example, it will increase energy consumption. One way you can optimize conveying velocity is by adjusting the blower speed. You can also use conveying line injectors to maintain an optimum conveying velocity.
- Ensure the bulk solids feeder is operating at the right speed. The feeder’s operating speed should closely match the material’s discharge rate. If it’s going too fast, the lines could block very quickly, causing pressure drops. If it’s going too slow, the system will be using more energy than is needed.
Ensure you’re using the right sized components
Oversizing components is a common issue with pneumatic conveying systems. In these cases, bigger isn’t always better, because components that are too large could result in unnecessary energy consumption, such as with large cylinders where the required air volume level will be much higher.
When selecting pneumatic components, always ensure your sizing requirements are accurate. This will maximize the energy efficiency of your system. For example, compact cylinders with reduced diameters can lead to 15% energy savings in pneumatic conveying systems.
Optimize the solids loading ratio
In a pneumatic conveying line, the solids loading ratio refers to the ratio between air and material (in pounds). Increasing this ratio increases the energy efficiency in pneumatic conveying systems because it means a decrease in velocity and air volume. By reducing these parameters (within a suitable range, of course), you can optimize the conveying rate because the system will require less energy.
Here are a few ways you can check and optimize the solids loading ratio:
- Conduct pilot plant tests to calculate the solids loading ratio properly
- Check the solids loading ratio periodically and recalculate if needed
- Hire a professional to inspect the system and check your calculations are correct
Check for and minimize pressure drops
Pressure drops are one of the biggest causes of poor energy efficiency in pneumatic conveying systems. When there’s a loss in pressure, the system will struggle to convey the material through the pipelines, resulting in blockages that can stop the air flow, increase energy consumption, and even halt production.
Look out for these three common causes of pressure drops so you can resolve them before they become an issue:
- Overfeeding: If too much material is being fed into the conveying line, there won’t be enough pressure to move the material through the pipelines. Always ensure that the lines are being fed at the correct rate based on the material you’re conveying.
- Air flow rate: As with overfeeding, a low air flow rate can cause blockages, pressure loss, and high energy consumption. You can mitigate this issue by following a number of air requirements, like ensuring the air flow rate has been calculated for the specific material you’re conveying, that the air movers have enough output capability, and that the air flow rate corresponds to the air velocity.
- Air leaks: Air leaks are one of the fundamental factors to prevent when optimizing the energy efficiency in pneumatic conveying systems. Line leaks often occur at pipe joints and cause your system to waste a lot of energy as it has to work harder to maintain the correct pressure level.
If you notice your system’s energy consumption has suddenly skyrocketed, an air leak could be behind it. If this is the case, you should be able to hear and feel it, but you should also inspect components like couplings, flanges, gauge ports, and valves. You can also test the integrity of all connections by pressurizing the system and spraying it with soap bubble solution.
Make an inspection checklist
Finally, one of the best things you can do when looking at how to save energy in pneumatic conveying systems is to make an inspection checklist that you can run through periodically.
In addition to what we’ve already mentioned, some of the key things to include are:
- Check pressure regulators to ensure correct consumption of compressed air
- Ensure rotary valve clearances aren’t too high and are in good condition
- Look for material buildup inside the pipelines to avoid blockages
- If using a multiple pick-up point system, make sure to isolate unused feeders
- Ensure there aren’t any cracks in filters and cooler housings
- Make sure that there aren’t any tight elbow transitions
- Check that the baghouse is operating on a clean-air vs. dirty-air differential-pressure cleaning cycle to avoid unnecessary air injection
