Dear Joo,

In a pneumatic conveying system, the ambient air is used.

The maximum Relative Humidity is 100% at ambient temperature.

A higher pressure causes a higher RH and when the RH reaches 100% also condensation

A higher temperature causes a lower RH.

The combination of a changed temperature and a changed pressure determines the occurrence of condensation.

In a pneumatic conveying vacuum system the pressure drops and the temperature will not change significantly (unless very cold material) and the RH decreases.

Therefore in a vacuum system, there will be normally no condensation.

In a pressure system, where the pressure increases and the compressed air will cool down at least to the material temperature, condensation is likely to occur.

To find the location where the condensation starts, the pressure/temperature conditions along the pipeline have to be calculated.

Depending on the ambient conditions, the amount of water can be calculated.

As the local conditions in the pipeline are also known, the eventual condensation can also be calculated.

The chemical formulas will give you the amount of bonded material. (f.i. cement)

It is possible to calculate for the condensed amount of water and for the amount of water vapor.

As the pressure and temperatures are related to the SLR, it can be some work to calculate for all circumstances.

If the material does not bond with water the condensed amount of water will be equally divided over the material and possibly evaporated further in the pipeline, where the pressure goes down and the RH decreases.

If you have NETFramework from Microsoft on your computer (which can also be downloaded) then I can post a VisualBasic file for the calculation of condensation.

Or do you prefer the spreadsheet version? or both?

VisualBasic is nicer.

success

teus ■

Dear Joo,

I will mail you the files.

I understand that you are using compressed plant air (7.5 bar) for your conveying system working at 1.8 bar.

Probably you are using a sonic choke or a flow regulator with a pressure regulator.

Your conveying system must have a safety relieve valve, set at approx 2 bar in order to prevent too high pressures on the pneumatic conveying system.

If the air is compressed to 7.5 bar first and the air is cooled in a tank, the water is already condensed. Lowering the pressure to 1.8 bar will make the RH rather low and the pneumatic conveying system will see no condensation.

A cooling dryer has normally a dew point of about 3 degrC (Otherwise the water would freeze)

success

teus ■

Hi Joo,

Do you use this system a lot? If so, a low pressure oil free screw compressor is the better technology to use as it kills two birds with one stone:

1) It uses far less energy due to it compressing the air only to the required system pressure instead of plant air 8Bar level. ROI's of 12 months are not rare in these circumstances, especially in 24/7 operation mode.

2) Single stage oil free rotary screw compressors compress at much higher discharge temperatures since they comprise not contacting no-contact screws that require no oil injection and no after coolers as found on oil free two-stage dry screws. Hence there is little chance for moisture to drop out into your conveying line. It does require for the material to handle temperatures of around 180-200C at your p2 pressure. ■

Hi Joo,

It is our goal to just deliver the airflow and pressure you need, in other words the least power consumption possible. We offer a 2BarG and a 3 to 3.5BarG dry screw with different rotor profile to optimise total system efficiency and power consumption. Each type also comes with at least two different built in compression ratios that help us match internal pre-compression with your system pressure, which helps optimizing compressor efficiency also. Addtionally we offer gear or pulley sets that accommodate your desired flow conditions in 6% steps, which avoids costly compressor bypass operation. VFD's are also available, which can assist to tune into exactly the flow you need for your system. All compressors are air cooled, which eliminates the need for installing and maintaining a cooling water circuit.

The total life cycle cost for this type equipment is power consumption - not initial equipment cost. Unfortunately, air audits for plant air operation are much more common than in low pressure pneumatic conveying applications. The savings comes from not having to compress air to a high pressure just to bleed it down to the desired lower pressure. If you know how much air your system needs, it is possible to calculate your power savings (not even to mention to "soft cost" of having to potentially maintain a plant air compressor system and its cooler and dewatering systems less). ■

Amendment: The total life cycle cost is dominated by the power consumption - not the initial equipment cost. ■

hello

about the power saving, there is a pneumatic principle, that is if the pressure increase bar, the power is increasing by8%, so if it is possible , using the low pressure to conveying¡£but sometimes, it is no possible to use low pressure air flow to transport bulk solids, so maybe using the raguator and laval nozzle(adjustable) to transport the bulk solid, i think that can in some certain save air flow.

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Originally Posted by Teus Tuinenburg

Dear Joo,

In a pneumatic conveying system, the ambient air is used.

The maximum Relative Humidity is 100% at ambient temperature.

A higher pressure causes a higher RH and when the RH reaches 100% also condensation

A higher temperature causes a lower RH.

The combination of a changed temperature and a changed pressure determines the occurrence of condensation.

In a pneumatic conveying vacuum system the pressure drops and the temperature will not change significantly (unless very cold material) and the RH decreases.

Therefore in a vacuum system, there will be normally no condensation.

In a pressure system, where the pressure increases and the compressed air will cool down at least to the material temperature, condensation is likely to occur.

To find the location where the condensation starts, the pressure/temperature conditions along the pipeline have to be calculated.

Depending on the ambient conditions, the amount of water can be calculated.

As the local conditions in the pipeline are also known, the eventual condensation can also be calculated.

The chemical formulas will give you the amount of bonded material. (f.i. cement)

It is possible to calculate for the condensed amount of water and for the amount of water vapor.

As the pressure and temperatures are related to the SLR, it can be some work to calculate for all circumstances.

If the material does not bond with water the condensed amount of water will be equally divided over the material and possibly evaporated further in the pipeline, where the pressure goes down and the RH decreases.

If you have NETFramework from Microsoft on your computer (which can also be downloaded) then I can post a VisualBasic file for the calculation of condensation.

Or do you prefer the spreadsheet version? or both?

VisualBasic is nicer.

success

teus

Dear sir

I have discussed the possibility of condensation in pneumatic conveying with you extensively . I been pose to address one issue , hence please accept ,y request to

1) Forward the spreadsheet as mentioned by you

2) Forward the visual basic file to help me

regards ■

Originally Posted by Teus Tuinenburg

Dear Joo,

I will mail you the files.

I understand that you are using compressed plant air (7.5 bar) for your conveying system working at 1.8 bar.

Probably you are using a sonic choke or a flow regulator with a pressure regulator.

Your conveying system must have a safety relieve valve, set at approx 2 bar in order to prevent too high pressures on the pneumatic conveying system.

If the air is compressed to 7.5 bar first and the air is cooled in a tank, the water is already condensed. Lowering the pressure to 1.8 bar will make the RH rather low and the pneumatic conveying system will see no condensation.

A cooling dryer has normally a dew point of about 3 degrC (Otherwise the water would freeze)

success

teus

Kind attention Mr Teus

Dear sir

Can you forward the condensation calculation both in Excel and VB to my mail id (chaubey.07@gmail.com)

thanks in anticipation ■

Dea kj,

Attached the Excel file for the calculation of condensation in air.

have a nice day

Teus

Attachments

condensation_5 (ZIP)

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