Re: Dense Phase Pneumatic Convey Plug
Dear Quinn,
Recalculating your system, it should perform approx. 16 tons/hr at 2.5 bar for limestone powder of 35 micron.
Bigger particles ( a pea = 2.5 mm) in the material should not create problems, as long as the bigger particles are not dominant in the mixture. (Particle size distribution?)
For a 3.5 inch pipe, an airflow of approx. 4.5 m3/min should be sufficient.
The application of injectors is then not required.
For evaluation the performance of the installation it is necessary to know the parameters:
-air flow
- pneumatic conveying regime. Plug-flow?
-pressure
-capacity
-kettle opening pressure. (lower opening pressure can prevent initial blocking)
-Valve condition (specially the discharge valve)
-Control and effect of injectors. Are the settings according to the design?
More accurate information about the behaviour of the installation is necessary.
have nice day
Teus ■
Teus
Dense Phase Line Plugging Problem
Dear Quinn,
The first thing you should do is to somehow find out the air flow rate to allow you to calculate the pick-up velocity. A very low pick-up velocity may be your main problem.
If you send full details of your conveying system, I will try to help you .
Regards,
Amrit Agarwal
Consulting Engineer
Pneumatic Conveying Consulting
Email: polypcc@aol.com ■
Re: Dense Phase Pneumatic Convey Plug
Originally Posted by Quinn
Not much information is known on the air flow characteristics.
...................
Plugging begins right at the first vertical elbow. The larger limestone particles seem to get stuck while the fine powder is pushed threw. The initial problem is getting the pipe fully unplugged, when the line is clear, attempting to convey plugs the line again.
Any ideas or suggestions??
Thanks
Air injectors......Where, when & why were these fitted? You need to determine the actual localised airflows with this sort of issue. With & without the injected air. Are you running at the characteristics mentioned by Teus? ■
Re: Dense Phase Pneumatic Convey Plug
Louis,
The air injectors are located on the limestone piping running to the day hoppers. There are about 10 injectors throughout the piping. They were put in when the system was made in 1990. The reason for the injectors is unknown, I assume the engineer on the project at that time seemed to think that they were needed.
We are currently clearing out and replacing the diverter pinch valves at the end of the piping line. We have 4 day hoppers(A,B,C,and D) that feed the limstone into the burners. Two valves break off to hoppers A,B and C,D. From here four more valves break off to each A, B, C and D. At the control panel you may select which hopper you would like to convey to by opening and closing the pinch valve at the corresponding hopper.
Teus,
The majority of the limestone is NOT powder, average size is about 1.5mm but range is 35 micron to 2.5mm.
Amrit,
An air flow meter has been ordered!! ■
Re: Dense Phase Pneumatic Convey Plug
Dear quinn,
The 1.5mm limestone particles have a suspension velocity of approx 8 m/sec.
For the bigger particles, an airflow of approx 7.5 m/min should be sufficient, creating an end velocity of approx. 26 m/sec.
The estimated capacity is then still approx. 16 tons/hr at 2.5 bar.
(SLR =30.2)
The injectors are not necessary and if they are still used, they might be the cause of your problem.
Suppose they inject too much air in the pipeline, causing backflow towards the beginning of the pipeline and reduce the velocity right after the intake, resulting in a blockage.
A conveying test can be executed quite easily (after checking the air supply volume).
Isolate all the injectors and start feeding the system with an increasing amount of limestone and note at least the occurring pressures and if possible the capacities.
A rental compressor of 7.5 m3/min can also be used, to be certain of the airflow.
success
Teus ■
Teus
Re: Dense Phase Pneumatic Convey Plug
Dear
Your quiry caught me to reply you. Part of your query seems you have opted for couple of way to go. Well its pretty difficult to take a orrange from different basket if bot have same property. Point is i would say look, to in densephase power saving and with intensified engineering approach will be the impeccable way for key barometer. Decisively if you want to go for power saving and want to be more maintenence free , you should opt for densephase. Ihave mountable reason and inclined to believe on densephase. Apprantly iam from engineering proposal side, and have had my full attention drew towards pneumatic handling system. Its maint free coupled with other advantage like continuity of flow force me to prefer the pneumatic conveying. I am very much supportive to the reply you got from Panel of experts. There is divided opinion on your quiry, but to bridge-out the other perception i would say , Consecutively pneumatic handling become the latent demand now a days . Again specially in this competitive market , you have to have the multi approach strategy whcich will patronage you to get you the concrete platform.
rahul ■
Help
Hello to all,
I am new here and I am trying to get some help in designing pneumatic conveyors.
I need to design a lean phase system to transport calcined alumina. I know the conveying rate is 11 t/h and the horizontal and vertical distances are 80 m and 19 m respectively. The number of 90 degree bends is 6. I need to calculate the air flow rate and the pipe diameter. Does anyone have any suggestion for a solid loading ratio for calcined alumina? I also need to select a suitable blower for the system. I hope you guys can help me.
Regards,
Tony ■
Re: Dense Phase Pneumatic Convey Plug
Dear Tony,
Are you referring to:
-pressure system
-vacuum system
What are the alumina properties?
-particle size distribution
-material density
-bulk density
-temperature
Then you have to decide how the pneumatic conveying system will be fed:
-single- or double kettle system
-rotary valve (not recommended because of high abrasivness of alumina)
Is there any backpressure at the end of the pipeline (silo or process)
Alumina (Al2O3) is known for its, sometimes, difficult behaviour in pneumatic conveying.
In this respect, it might be better to choose a low-pressure system.
Therefore, such an installation must be controlled very accurately.
Calculating the airflow and pipe diameter is one step but designing the complete system with components (valves etc.) and automated controls requires just as much or more skill and experience.
Have nice day
Teus
PS May be, it is better to open this question in a separate thread. ■
Teus
Dense Phase Pneumatic Convey Plug
I am currently working to unplug a dense phase convey line which transports limestone to coal feeders. It is an old and poorly designed system which seemed to have troubles from the beginning.
The setup includes a Cyclonaire DPG-5B conveyor which feeds limestone of various sizes from powder to about half of a pea. Compressed air is used at 100 psi.
Pipe diameter is 3.5 inches. Standard steel pipe is used with cast iron elbows. The flow begins at ground level and travels horizontally 8 ft. until the first vertical elbow. From here is goes a vertical distance of 52 ft. 10 in. to another vertical elbow. Then horizontal 31 ft. to a horizontal elbow. Then 113 ft horizontally to a vertical elbow which then goes vertical another 8 ft to the last vertical elbow. Lastly it travels 15 ft horizontal to the feeder. Air injectors are located throughout the piping.
Not much information is known on the air flow characteristics. Air flow and tank pressure are controlled by two poppet valves near the DPG conveyor but there are no gauges showing pressure or flow. Two pressure regulators show a pressure around 100 psi before each valve.
Plugging begins right at the first vertical elbow. The larger limestone particles seem to get stuck while the fine powder is pushed threw. The initial problem is getting the pipe fully unplugged, when the line is clear, attempting to convey plugs the line again.
Any ideas or suggestions??
Thanks ■