Andover Technology Partners Page 1 May 6, 2010

To: Elineth Torres

Fm: Jim Staudt

Re: Electrical load for wet scrubbers

From my analysis it appears that there was a mistake in the original memo.

In my original memo I used the following equation: from Reference 1 that says that to estimate

fan kW,

Shaft kW = Q * dp / (367,000 * fan efficiency) E.32

Where Q is in actual cubic meters per hour

dp is in mm H 2 O

Since I didn’t develop that equation, t o be safe, I’ m going to do this from the basics

– Mechanical Engineering 101 :

Fan kW = Q (volume flowrate in cubic meters per second) * dp (pressure difference

in newtons per square me ter)/(1000 W/kW * fan efficiency expressed as a decimal)

From my Feb 26 memo, the gas flowrate is roughly 100000 d scf per short ton clinker. This will

vary from one kiln to another, and is on the high side for a precalciner or preheater kiln

– the

kilns most likely to h ave a scrubber installed for SO 2 due to their size and the economics.

Q is therefore equal to

Tons per second of clinker * 100,000 dscf per ton of clinker * [ (273 0 C +65 0 C )/273 0 C ]

actual cubic feet per standard cubic feet / 35.5 cubic feet per cubic meter

Q = TP S CLINKER * 3847.6 actual cubic meters per sec

We usually don ’t express kiln output in tons per second of clinker. Expressing in tons per hour

of clinker

Q = TP S CLINKER * 3847.6 actual cubic meters per hour/ ( 3600

TPSCLINKER/TPHCLINKER)

Q = 0. 969 * TPHCL INKER actual cubic meters per second

1 The Cement Plant Operations Handbook, Third Edition, International Cement Review , November 2001 

# Andover Technology PartnersAndover Technology Partners Page 2 This of course is dry gas volume and does not account for moisture. For a precalciner and

preheater kiln s , this number is sufficiently high that it should roughly account for moisture

. For

a wet process kiln it may be low. But, the dry kilns are far more important because the age and

inefficiency of the wet kilns is such that no one i s likely to add a scrubber to them.

Now we need to get the pressure drop ( dp ) in newtons per square meter. But, we normally have

dp in inches of water. Since,

1 inch of water column = 249 Newtons per square meter = 249 Pa and

We are assuming 18 inches water column of pressure drop , which ought to be plenty. This

assumes a Monsanto Environmental Control Dynawave scrubber , which has a frothing section

. For a spray tower scrubber , which has also been used in cement kilns, the pressure drop c ould be

about half of that.

d p = 18 IWC * 249 Pa /IWC = 4482 Pa

And, since we will assume a fan efficiency of 0.75, we have the equation:

Shaft power in newton meters per second (or watts)

= Q * dp

= 0.969 * TPHCLINKER ( equals volume in cubic meters per second) * 4482 Newtons

per square meter/0.75

= 5789* TPHCLINKER (shaft power in watts)

For kW divide by 1000 W per kW

Shaft power in kW = 5.789 * TPHCLINKER

, or

Since TPHCLINKER is estimated as TPYCLINKER/(8760*0.9)

Shaft power in kW = 5.79 * TPYCLINKER/(8760*0.9)

Shaft power in kW = 7.34 E

- 4 * TPYCLINKER

Now, for a 150 TPH kiln, this means that shaft power for the fan is:

5.789 *150 = 868 kW

Add roughly 15% for recirculating pump demands, etc. and it results in

Total power in kW = 8.44E

- 4 *TPYCLINKER

Or

, for a 1.2 million ton per year kiln, 1013 kWAndover Technology Partners Page 3 Now, to estimate the cost per year, we multiply times COSTKWH

So,

Annual Cost of Power = 8.44E

- 4* TPYCLINKER * COSTKWH

W here COSTKWH is the cost of power in $/kWhr

A nd TPYCLINKER is the annual clinker output in short tons per year

Hopefully, that spells it out a bit clearer, and it is correct. I apologize for not catching

this earlier. Keep in mind that there are several assumptions made along the way

– gas flowra te,

temperature, pressure drop, load from recirc pumps, etc.

– that impact the actual power

requirement for any particular application. I expect that the results from these calculations

should be pretty representa tive for most applications.