Condensation in fly ash handling pipes - again-Mr.ken rad & Mr.cc flow

[rkarthik]

thanks for the advice. but i am at the suppliers end. the compressors flow as measured near the system is around 700 cfm. The orginal designer is not accepting for dryer system. so from our end we have identified some critical points where the jamming occurs and it also coincided the lowest temperature points on the pipeline. can we suggest some boosters like injectors on those vulnerable areas will a protable compressor which suits there cracking pressure.And secondly while running in dual tank ( the system is designed for dual tank mode) than in single tank the jamming is less frequent.But for maintenance reasons we have to run in single tank also.But surely we are thinking of dryer and will any heating of the input flyash to the system will be helpful?

 

[quark]

Are you required to do the conveying at an air temperature of 150[sup]0[/sup]C? Otherwise if you can cool down the air using an aftercooler (water cooled exchanger)at your operating pressure, you can reduce the jamming problem.

The main problem may occur at potential pressure dropping part of the piping like valves, bends etc. Even if you are cooling the air to ambient temperature (i.e pressure dew point at ambient temperature) it's atmospheric dew point further reduces. So there will be less likely chance of condensation even if you are reducing the air temperature to that of ambient.

Using boosters seems to be wastage of energy.

At what pressure your are conveying and what is the pressure drop?

Note: Though I didn't receive your reply to my comments in your last post, I again posted here because your problem seems interesting to me.


Regards,

 

[rkarthik]

Thanks for the info. Sorry I didnt notice your previous reply.The climatic conditions we are facing is really extreme one. During summer it can touch even 45-50 deg C max and during winter its between 1-4 deg C.So its a real challenge.The conveying air near the compressor is around 150-160 deg C. Near the tanks and the bypass valve system its around 130 deg C(insulated). During winters if we measure along the 974 mts( 950 mts -horz & 24 mts -vert, with 8 90deg & 1 45 deg bend) pipeline the temperature varies from 35 deg at 100 mts after tank to 4-5 deg C at almost 400mts.And jamming really starts after 400 mts for 100 mts and before the vertical line which is around 24 mts.If i understand your solution ,then chilling equipment is sufficient. But my other friends were asking me to go for a dryer.but this will reduce the compressor pr. which isesently 45 psi max and thereby reduce my capacity.the line pressure reaches a max of 18-20 psi if the system pr is set at 40 psi.The compressor is designed to deliver 900 cfm but as measured near tanks its around 800 to 850 cfm which is within acceptable range.I thought boosters might help in reducing the jamming tendency near the prone areas.

 

[ccfowler]

It makes sense to me that the plugging problem is more severe while operating in single tank mode. The periods of interruption in flow provide better opportunities for the troublesome combination of moisture and ash particles to attach to the pipe wall and commence the formation of plugs. (Locally relatively more air and less ash along with periods of time for particle attachments to form and grow.)

Reasonable efforts to remove moisture from the compressed air just make sense. The use of air dryers may be nice, but it is best to think in terms of what is practical for the particular installation. Any amount of moisture removed between the compressor and the conveying system is that much moisture no longer available to combine with ash in the pipeline. Perfectly dry air is not necessary. Instead, for the specific ash and circumstances, there is likely to be a correlation between the level of moisture concentration in the compressed air supply and the rate of plug deposit formation in the system.

Portable air compressors are not likely to include high performance air drying, so they may provide a mixed benefit to the system.

 

[quark]

I did a rough calculation of your system. If you are using cooling water from cooling tower to cool compressed air to even 45deg.C at the pressrue of 45psi (gauge, I presume) and you expand it again to ambient pressure, the air temperature becomes 40 deg.C

But in this condition the dew point is 30deg.C. Even cooling the air with water and removing the condensate will give you better advantage. (condensate removal is approximately 0.5kg/min with an ambient condition of 40deg.C DBT and 60% RH.

Dryer is a better option but initial cost and relevance to the process are the factors you have to consider.