dear kevinjcg

I have no direct experience with carbon black, although I spoke to some operators who conveyed such a kind of material in the past in the port of Rotterdam.

It was well conveyable in dilute or lean phase with a pneumatic unloader system, sucking the material into blowtanks and pressure conveying it to a silo.

The achieved loading ratio must have been approx 35 – 40 kg/kg

From your data I cannot read the material density and the average particle size.

You mention :

-8-15 tons/hr

-5 – 7,5 m3/min # 300 – 450 m3/hr

-loading ratio 10 – 15 kg carbon black per kg of air

Assuming an air density of 1,2 kg/m3 this will result in :

450*1,2*18= 8100 kg/hr # 8,1 tons/hr , which is far less than the 15 tons/hr you mention.

Furthermore I cannot understand the difference between a blowtank of 1,5 m3 and a pressure vessel of 9 m3, their function in the system and their influence on the capacity.

(continuous pipeline capacity or system capacity (incl pressurizing and purging time))

Also the difference in pressure of the blowtank, bypass and the pressure vessel.

How is your system set up?

You are also talking about dense conveying with a loading ratio of 10 – 15.

As I have no direct experience with dense phase conveying, I would consider a loading ratio of 10-15 extreme lean phase.

May be other forum members can enlighten me on this subject.

Then be careful with conveying Carbob Black powser.

It can be almost carbon dust and very sensitive to ignition and explosive.

May be lean phase is the more safe way to convey so that the MAC-value is not reached.

(MAC = Maximal Acceptable Concentration)

Although there will be certainly some places in the system where the MAC-value is reached, but there will be presumably no ignition sources.

Again, be careful, I do not want this to be your last question.

People in the coal fired power plant business must know a lot more of the handling of this product.

looking forward to hear from you ■

dear kevinjcg,

Carbon black can be conveyed pneumatically, that is for sure.

Because I do not have material data concerning this material, I cannot perform a calculation.

A full testresult would enable me to determine such a factor and then make predictable calculations.

Regarding your remark whether this is dilute or dense phase please note the following :

At a loading ratio of 15 the volume ratio is calculated as follows :

material density 2700 kg/m3

air density at 1 bar(o) 1,2*2=2,4 kg/m3

material volume / air volume = 15 * 2,4 / 2700 = 0,0133 or 1,33 %

or 1,33 ltrs of carbon black on 98,7 ltrs of air

I would say that this is not really dense phase but dilute phase.

Although I am aware of different types of pneumatic conveying from dilute- to plug conveying, and only have real experience in cement, flyash, alumina and recently with Calcium Carbonite with loading ratios up to 80 – 100 maximum, I am still puzzled what the real definition of dense phase is compared to dilute or lean phase.

best wishes ■

dear kevinjcg

particle size = 0.5 mm (average)

With a material density of 2700 kg/m3 this results in:

suspension (floating) velocity at atmospheric conditions :

v(susp) = sqrt (4/3 * density(prod)/density(air) * particle size/dragfactor)

v(susp) = sqrt (4/3 * 2700/1.2 * 0.0005/0.6) = 1.6 m/sec

The minimum conveying air velocity should then be approx. 8 m/sec

The air velocity at the end of the pipeline (where almost atmospheric conditions are)

is calculated :

Diam = 175 mm

A= 0.0240 m2

volume = 7.5 m3/min # 0.125 m3/sec

v-air = 0.125/0.0240 = 5.2 m/sec

This is lower than the minimum required air velocity and also different from your 9m

If the solid rating is “low” then dilute phase conveying

If the solid rating is “high” then dense phase conveying

solid rating = kgs of product / kgs of air

solid rating = (vol. of product * density of product) / (vol. of air * density of air)

solid rating = volume ratio (product/air) * density ratio (product/air)

In most cases the volume ratio (product/air) is very low and the density ratio (product/air) is very high.

The multiplication of the two results in the normally used values for loading ratios (high for short conveying lines and low for long conveying lines)

The density of the product/air mixture is easily calculated as :

density mixture = (mass of product + mass of air) / (volume of product + volume of air)

mass of air = approx. volume of air * 1.2

Example : density mixture = (8100 + 1.2 * 7.5 * 60) / (8100/2700 + 7.5*60) = 19 kg/m3

success ■

dear kevinjcg

I already have modeled a pipeline for you as follows:

-horizontal length = 131 m

-vertical length = 18 m

-1st length of 97 m – diameter 150 mm

-2nd length of 52 m – diameter 175 mm

Based on dia 175 mm and 10 m/sec air velocity a pumpvolume of 0,24 m3/sec # 14,4 m3/min

product: Carbon black

Bulk density = 370 kg/m3

Material density = 2700 kg/m3 (from data from internet somewhere )

particle size = 0,5 mm # 500 micron

Calculated suspension velocity under atmospheric conditions approx. 1,6 m/sec

This would allow me to start a calculation, but I do not have the material loss factor for Carbon Black.

( If carbon black is comparable with cement, than conveying is no problem)

But, if I understand your posts correctly, you already have done some trial tests.

If you can give me the results of those tests, then I can determine the material factors for Carbon Black.

Those data should give :

-pipeline geometry

-achieved capacity at corresponding pressure

-air-volume of compressor

-material density

-bulk density

-particle size

-fluidizable or not fluidizable product

-any information you might consider usefull

If you can help me with this information, I will come back with a calculation and/or comment.

best regards ■

The answer to this question is a definite YES. During the last 15 years I have been involved in the selection of dense phase conveying systems for carbon black from small systems up to 20,000 lbs/hr capacity. In this selection process I concluded that dense phase conveying systems for carbon black are definitely feasible if they are correctly designed and operated. Carbon black beads are made from furnace soot (called fluff), using a binder. These beads can easily revert to fluff if the system velocity is too high or the impact angles are too harsh. To prevent formation of excessive fluff, use a terminal velocity as low as possible but not more than about 10 ft sec. For these low velocities only the bypass type of dense phase system is feasible. In my opinion the design of this system is better left to the vendors who have extensive experience in carbon black, although any body with the dense phase design tools can takle this problem. The key is to minimize conveying velocity by using minimum air in the front and gradually introduce secondary air as needed. Also use extra long radius bends to minimize attrition of the beads.

Regards,

Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

dear kevinjcg,

have you had a look at thread

\Fire & Explosionprotection - Safety Aspects > Pneumatic conveying of Activted Carbon

Further I let you in the hands of Mr Agarwal, because he has much more experience with this product than I have.

Success ■