Dear Shin Ho Kwon,

Pneumatic conveying systems for cement and barite (and bentonite) are typically products, used in the offshore industry.

These installations work with high pressure systems (4.5 to 5.6 bar) and low compressor volumes.

This makes it possible to use 6”connection hoses between a PSV (platform supply vessel) and a drilling rig and still reach an acceptable conveying rate.

Visit:

http://www.carlsengroup.com/

You indicate that you have executed 2 different calculations.

-A previous calculation

-The "Pneumatic Conveying Design Guide" method by David Mills with scaling up.

2 different calculations with 2 different outcomes must be considered as a warning.

One must be wrong and when you do not know which one is wrong, it could well be possible that they are both wrong.

And if you know which calculation is wrong, the next question would be why and where.

That is why calculation algorithms have to be correlated to existing installations.

The conveying properties of materials is depending on particle size (distribution), particle density and stickiness.

If one of these changes, the calculation changes (required air velocity and pressure drop)

However, the used materials show a fairly consistent behavior, as they also have to meets application standards.

Unless you are planning to enter the pneumatic conveying business, there is no point in starting your own research and even then, it would be as inventing the wheel again.

Have a nice day

Teus ■

Dear Shi Ho Kwon,

I ran your installations through “quick modeling “ and found the following results:

Barite:

56 tons/hr at 3.5 bar

vbegin = 6.5 m/sec

vend = 28.8 m/sec

Cement:

79.6 tons/hr at 4.7 bar

vbegin = 6 m/sec

vend = 35 m/sec

Assumed are standard ambient conditions and sea level.

Which current technology are you referring to?

Have a nice day

Teus ■

Dear Shin Ho Kwon,

I calculated the example [Length = 163m, Bore = 53mm, Bends - 17*90degree, D/d = 4] that you refer to for cement.

The diagram A 2.7 (b) (cement) gives 12 tons/hr at 4.0 bar at an airflow rate of 0.0855 kg/sec.

My computer calculation results in:

10.8 tons/hr at 4.0 bar at an airflow rate of 0.0855 kg/sec.

Considering the uncertainties about the conveying conditions (s.a. temperature, cement properties, etc.), this result is reasonably acceptable.

My calculation method is described in:

https://news.bulk-online.com/pneumat...veying/65.html

For a pneumatic conveying calculation, I need the following information:

-geometric description of pipe line (horizontal length, vertical length, number of bends, diameter(s))

-Ambient conditions (Ambient temperature, intake temperature, altitude above sea level, RH)

-Material properties (Material, particle density, bulk density, particle size (distribution), temperature)

-Capacity or airflow.

-feeding system (pressure tank, screw feeder, rotary lock)

If you can supply this information for the above test and specialized engineering company data, I can recalculate and possibly compare the differences.

Note:

At high conveying pressures, the capacity-pressure curve becomes rather flat (low value of d(Cap)/d(p)), which results in high pressure fluctuations as a result of a small feeding fluctuation.

It is a well-known fact that the pneumatic conveying capacity of barite is less than the capacity for cement.

[/quote]

According to their calculation, the transfer rate of barite is 100ton/hr. However, test results was over.

[/quote]

Obviously there is a mismatch between the calculation and the test.

This is not uncommon.

However, where the mismatch is generated is not so easy.

Although there are a lot of studies and books that describe the physics of pneumatic conveying, they seldom provide a user-friendly and/or reliable calculation method.

Although the principle of pneumatic conveying is simple, the calculation is far from that.

A pneumatic conveying calculation becomes complex, because of the inter related influences between velocity and pressure, SLR, temperatures, compressor characteristics, etc.

At this moment, I am not planning to publish the calculation method.

I gave the results in #4 of this thread.

Barite:

56 tons/hr at 3.5 bar

vbegin = 6.5 m/sec

vend = 28.8 m/sec

Cement:

79.6 tons/hr at 4.7 bar

vbegin = 6 m/sec

vend = 35 m/sec

Assumed are standard ambient conditions and sea level.

Have a nice day

Teus ■

Dear Shin Ho Kwon,

I modeled the installation as follows:

horizontal length = 60 m

vertical length = 19 m

number of bends = 23

Compressor barite = 0.358 m3/sec (1290 m3/hr)

Compressor cement = 0.4333 m3/sec(1560 m3/hr)

conveying pressure = 4.7 bar

BARITE:

pipe line diameter 5” (128 mm) – capacity = 66.6 tons/hr at 4.7 bar

pipe line diameter 6” (154 mm) – capacity = 97.6 tons/hr at 4.7 bar

pipe line diameter 8” (203 mm) – capacity = 188 tons/hr at 4.7 bar

CEMENT:

pipe line diameter 5” (128 mm) – capacity = 79.6 tons/hr at 4.7 bar

pipe line diameter 6” (154 mm) – capacity = 113 tons/hr at 4.7 bar

pipe line diameter 8” (203 mm) – capacity = 210 tons/hr at 4.7 bar

Note that I used the same compressors for the 5”, 6” and 8” installations.

This means that the airflow for the 5”and 6”installation can be lowered.

At high conveying pressures (> 4.7 bar), the capacity-pressure curve becomes rather flat (low value of d(Cap)/d(p)), which results in high pressure fluctuations (instable conveying) as a result of a small feeding fluctuation.

Normally, cement, barite and bentonite as applied in the offshore industry, are conveyed with the same pneumatic conveying installation.

Visit:

http://www.carlsengroup.com/

Have you asked the specialized engineering company to substantiate their calculations?

Take care,

Teus ■

In reality you will never achieve 4.7 barg at 80m. You will be lucky to reach 2 - 2.5 barg.

This will lead to higher pick up velocities and with the suggested airflows and lower conveying

pressures you will move into lean phase. Questions is will the SLR high enough to chock the

line or not at these velocities. Commercially the system is not viable one.

You are too high on air flows you need to look at reducing the air flows and bring back the system

into dense phase. It is standard to step the pipes if your conveying pressure is above 2 barg to reduce

the exit velocity. ■

Dear Mantoo,

I must confess, that I have never witnessed a system that operated at 4.5 bar or over.

However, I operated a cement conveying system that reached 3.2 bar to 3.4 bar on a 10”/12” pipeline with a length of approx. 150 m.

Reaching a high pressure is only possible if the feeding is enough to reach the necessary SLR.

I calculated the volumetric loading ratio of the 2 material for the 6”installations:

barite:

0.1037 m3of material/m3 of air at the intake

mixture density at the intake = 197 kg/m3

SLR = 65.4 (Which is not an extreme value)

cement:

0.1829 m3of material/m3 of air at the intake

mixture density at the intake = 227.9 kg/m3

SLR = 78.2 (Which is not an extreme value)

I agree that systems above 2 bar should have a stepped pipeline.

However, in reality, a significant number of installations are built with one pipe diameter along the whole length.

As a consequence, the airflow is designed for the intake velocity and therefore the end velocity is somewhat too high.

This effect is stronger at higher conveying pressures.

Nevertheless, all pneumatic conveying installations on board of supply vessels and drilling rigs are designed for 5.6 bar to 6.0 bar at 5”or 6” lines.

See the link I gave earlier in this thread.

Calculations indicate that up to 4.5 or 5 bar, the conveying is stable plus the slope of the capacity curve is steep enough to absorb feeding fluctuations below the 5.6 bar.

I agree also with your argument that a shore based installation is best be designed for 2.5 bar.

Have a nice day

Teus ■

Dear Shin Ho Kwon,

Since you are interested in the pneumatic conveying properties of cement and not in the chemical and structural properties, the only properties that are relevant, are the suspension velocity and fluidizability.

These 2 properties are related to the particle size distribution.

OPC and OWC are, in terms of pneumatic conveying, comparable as long as the particle size distributions are comparable.

Rather than calculating a drillship pneumatic conveying system for barite, cement and bentonite yourself, it is better to rely on a well-known equipment supplier:

http://www.carlsengroup.com/

Pneumatic conveying calculations for offshore installations, where high conveying pressures of 4.5 bar to 5.6 bar are commonly used, are difficult to solve, due to the flat capacity-pressure curve.

Take care

Teus ■

Dear Shin Ho Kwon,

Cement manufacturers who produce different types of cement present the differences in terms of:

-chemical composition

-curing times

-ultimate strength

-etc.

These data are not relevant for pneumatic conveying.

Furthermore, the cement can be delivered in various particle sizes given in microns or the so called Blaine number.

Blaine = 20303*SQRT(micron) in cm2/gram

The difference between OPC and OWC is negligible apart from the particle size.

However, OPC as well as OWC can be ordered with different Blaine numbers.

The particle size in combination with the particle density (resulting in the suspension velocity) is the only relevant pneumatic conveying property for calculating.

(The solid loss factor is probably the same)

Note, that the SLF is related to the calculation algorithm.

Somehow, I missed your reply #10 in which you present a table of cases.

I notice that the particle size of 12 micron is very fine for cement.

I come back later on these cases.

It might be easier to supply the previous field data and that I recalculate the field data and after that apply the derived values in the various cases.

Have a nice day

Teus ■