From what I remember as seasonal in a pulverised coal powerplant the ash is so light anyway it flows like water after is collected in the bag house and then removed so it is an easy product to convey.

The bottom ash was pumped to a vacuum filter for later disposal from what I remember.

You may need to pipeline pig the lines from the vessel outward to clean them.

When was the compressor last checked for efficiency or new?

leon ■

Dear seahill,

In the blow tank, the fly ash – air mixture is formed with an SLR that generates the designed pipe line pressure of the conveying system.

The tank outlet configuration in combination with the design pressure and tank air flow determines the SLR.

In general, more tank air mixes more fly ash.

This is the way, the SLR is regulated by diverting the total air flow between the tank and the by-pass, which is connected shortly after the blow tank.

The tank outlet configuration can also be arranged that the by-pass is closed or not necessary.

Whether your installation can be upgraded to a higher capacity, depends on how far it is underused at this moment and whether the design is already optimal.

A calculation of the existing design can indicate the possibility of improvement.

With the existing pipeline, there is a maximum conveying capacity, which cannot be exceeded.

To execute such a calculation, it is necessary to know the pipe line geometry, tank size, fly ash particle size, fly ash particle density, fly ash bulk density, air compressor displacement, present capacity at the reached pressure.

Your installation (5” – 600 m) could have a capacity of approx. 20 tons/hr at 2.5 bar.

Have a nice day

Teus ■

seahill

A lot has to do with the product you want to handle and just how "optimized" you want the system to be.

The ability of the material to become "aerated" or 'fluidized" and more importantly, the ability of that material to retain it's "aeration" has a great deal to do whether or not air assists are needed along the convey line or if putting all the air into the tank will suffice.

I have experience and installed systems for some very nice Class A Geldart materials which are a mile in length with all the air put into the system at the beginning only.

I have recently done a system for a material which looks like a Class A material but acts like a "sieve" in that it has very poor aeration retention. The end result was a pressure tank line charger with air assists every 3' along the line.

Many systems which put all the air into the beginning work well BUT end up wasting energy and can very well be doing significant damage to the product and/or pipe line due to an excessive velocity profile.

On the other hand, fully optimizing and designing a dense phase system with air assists can get more expensive and turn into a nightmare if the product changes physical characteristics. ■

Dear Seahill,

In all my also [limited] previous experience I found various types of blow vessels; from bottom discharge to top discharge, single, twin, double, series of vessels, with and without by-pass. The by-pass function to control the SLR (see Tues' reply) can also be executed directly at the blow tank itself with one nozzle delivering the conveying gas flow, and a second nozzle delivering the SLR control air. This is often done for single/twin vessel arrangements.

If you have a sketch of your vessel arrangement it should become clear.

Regards, Sven ■