Contents

# EVERY SINGLE EQUATION IN CEMENT INDUSTRY

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**P A R T I**

**CEMENT CHEMISTRY**

# Chapter 1

# QUALITY CONTROL FORMULAS

## 1.01 Ignition Loss

Ignition loss is usually determined by tests in a laboratory furnace. It can also be

calculated from the chemical analysis of the kiln feed by the following formula:

## 1.02 Silica Ratio

Large variations of the silica ratio in the clinker can be an indication of poor

uniformity in the kiln feed or the fired coal. Changes in coating formation in the burning zone,

burnability of the clinker, and ring formations within the kiln can often be traced to changes

of the silica ratio in the clinker. As a rule, clinker with a high silica ratio is more difficult to

burn and exhibits poor coating properties. Low silica ratios often lead to ring formations and

low early strength (3 – 7 days) in the cement.

## 1.03 Alumina – Iron Ratio

Clinker with a high alumina – iron ratio, as a rule, produce cement with high early

strength (1 to 3 days) but makes the reaction between the silica and calcium oxide in the

burning zone more difficult.

## 1.04 Lime Saturation Factor

This factor has been used for kiln feed control for many years in Europe and only

recently has also found acceptance by American cement manufactures. When the lime

saturation factor approaches unity, the clinker is difficult to burn and often shows excessive

high free lime contents. A clinker, showing a lime saturation factor of 0,97 or higher

approaches the threshold of being “overlimed” wherein the free lime content could remain at

high levels regardless of how much more fuel the kiln operator is feeding to the kiln.

## 1.05 Hydraulic Ratio

This index is very seldom used any more in modern cement technology for kiln feed

control.

## 1.06 Percent Liquid

Clinker, when burned at a temperature of 1450ºC, Has the following liquid content:

## 1.07 Burn ability Index

This is an indicator of the ease of burning for a given clinker. The higher the index

number, the harder the clinker is to burn.

BF = LSF +10SR – 3(MgO + Alkalis)

(find LSF in 1.04 and SR in 1.02)

## 1.09 Bogue’s Formulas for Clinker and Cement Constituents

For a cement chemist, these formulas are the most important and frequently used

indicators of the chemical properties of a cement or clinker. The constituents calculated by

these formulas, however, are only the potential compositions when the clinker has been

burned and cooled at given conditions. Changes in cooling rate or burning temperature can

modify the true constituent composition to a considerable extent.

a) Bogue’s Formulas for Cement Constituents

b) Bogue Formulas for Clinker Constituents

When appreciable amounts of SO3 and Mn2O3 are present in the clinker, the values of

the chemical analysis have to be recalculated to take into account the amount of CaO that has

been combined with SO3, the amount of free lime present and the Mn2O3.

The values to be used in the Bogue formulas are:

To find the amount of CaO that is combined with SO3 as CaSO4 proceed as follows:

Having determined the appropriate values for the CaO and Fe2O3, one can then

proceed to calculating the potential clinker constituents by using the previously given Bogue

formulas. When the Bogue formulas are used for feed compositions, keep in mind that the

coal ash addition, dust losses, and alkali cycles can alter the final composition of the clinker.

Also use the analysis on a “loss free” basis in the calculations of the constituents.

## 1.10 Total Carbonates

Total carbonates are usually determined analytically by the acid-alkali titration

method. They can also be calculated from the raw (unignited) analysis as follows:

## 1.11 Total Alkalis as Na2O

The total alkali content in terms of sodium oxide is calculated from the loss free

analysis:

## 1.12 Conversion of Raw Analysis to Loss Free Basis

### where

Or = percent of oxide (by weight) on a raw basis

Of = percent of oxide (by weight) on loss free basis

L = percent loss on ignition (by weight)

1.13 Conversion of Kiln Dust Weight to Kiln Feed Weight

Dust collected in a precipitator or bag house of a kiln shows a different loss on ignition

than the kiln feed because it has been partially calcined. For inventory control purpose and in

some kiln operating studies it is often necessary to express the weight of dust in terms of

equivalent feed weight.

## 1.14 Calculation of Total Carbonates from Acid-Alkali Titration

This method is only applicable when the MgO content of the sample is known. Values

from the raw (unignited) basis are used for the calculation.

## 1.15 Percent Calcination

Kiln feed or dust samples taken at any location of the kiln are often investigated for

the apparent degree of calcination the sample has undergone.

## PROBLEMS AND SOLUTIONS

Problems and examples shown in this chapter are all subsequent chapters are arranged

in the same sequence as the formulas are presented in the chapter.

**Chapter 2**

**KILN FEED MIX CALCULATIONS**

## 2.01 CaCO3 Required to Obtain a Given C3S in the Clinker

This formula should only be used as a quick reference in times when no other

analytical methods, other than the titration method, is available.

where

A = desired C3S in clinker

a = existing C3S in clinker

## 2.02 Two-Component Mix Calculations

a) To obtain a constant total carbonate content

This method can only be used when the MgCO3 content in the two components is

constant.

where

x = material A needed (percent by weight)

100 – x = material B needed (percent by weight)

C1 = TC in material A (percent by weight)

C2 = TC in material B (percent by weight)

TC = desired total carbonates

b) Percent of each component needed for a desired CaCO3

Use this formula only when the MgCO3 content in the two components is constant.

where

w = weight of material A needed for each 100 unit weights of material B

Cf = CaCO3 desired in mix

C1 = CaCO3 in material A

C2 = CaCO3 in material B

c) To obtain a constant C3S/C2S ratio

Insert the values found from the raw material analysis (on the raw basis)

d) Formulas for mix corrections

Limestone added to a cement rock to correct mix.

where

M = percent CaCO3 desired in mix

F = percent CaCO3 found in mix (before correction)

A = percent limestone already added

L = percent CaCO3 in limestone

X = corrected percent limestone needed to obtain M.

Clay added to a limestone to correct mix.

where

M = percent CaO or CaCO3 desired in mix

F = percent CaO or CaCO3 found in mix

B = percent clay already added

C = percent CaO or CaCO3 in clay

X = percent clay needed to obtain M

## 2.03 Three Component Mix Calculation

a) To obtain a desired LSF and SR

## 2) Desired compound composition

Whatever targets are set, make sure to make:

3) Theoretical compound composition for each component

To be calculated from the raw analysis data. Also make sure to use the proper sigh (+

or -).

Note: Proceed with the calculations only when the sum total of the compounds

corresponds to the total of the oxides, i.e, for L: total oxides = x1 + y1 + z1 , etc.

4) Calculations, auxiliary matrix

5) Weight of each component needed per unit weight of clinker

All weights units can be used, i.e., the results can be expressed in ton/ton, or kg/kg of

clinker. Results obtained must all be positive numbers. If any of the results are negative, the

desired mix cannot be obtained with the given raw materials. Fighter the targets have to be

changed or other suitable raw materials must be selected.

## 2.04 Four – Component Mix Calculation

a) Analysis of components (raw basis)

b) Desired clinker composition

c) Theoretical compound composition for each component

(to be calculated from raw analysis data, make sure to use the proper sign)

d) Raw material costs

(insert here the total costs per ton, for each raw material. These costs will

later be used to determinate the cost of the calculated mix)

Note: The sum total of the oxides of each raw material must equal the

sum total of the compounds of that material.

e) Calculation, auxiliary matrix

note: Make sure to indicate the proper sign in the results.

f) Weight of each component required per unit weight of clinker.

The result can be expressed in terms of kg/kg clinker. Results obtained must all be

positive numbers.

g) Final mix proportions

Note: All results are expressed in terms of a decimal.

h) Cost of the mix

The cost of the mix per unit weight of clinker can be calculated as follows:

## 2.05 Determination of Chemical Composition

When certain properties are required in a mix, a preliminary investigation of the

needed chemical composition can be made by the following trial and error method. This

method is only applicable when Al2O3/Fe2O3 is higher than 0,64.

Desired:

# PROBLEMS AND SOLUTIONS

The sum total of the primary oxides is 97,91 and x1 has been found earlier to be 98,0.

Therefore, this composition is acceptable since the two agree closely with each other.

**Chapter 3**

**KILN FEED SLURRY**

## 3.01 Specific Gravity and Pulp Density of Slurries

## 3.02 Properties of Water

## 3.03 Mass of Slurry Required per Mass of Clinker

Metric units can be employed in this formula.

## 3.04 Slurry Feed Rate Required

## 3.05 Clinker Production for a Given Slurry Rate

C = clinker rate (long tons per hour)

c = clinker rate (short tons per hour)

w1 = mass slurry per mass of clinker

D = pulp density of slurry (kg/m3)

F = mass dry feed per mass of clinker (tons/ton) or (kg/kg)

G = slurry rate (m3/s)

g = slurry rate (gpm)

M = percent moisture

## 3.06 Clinker Production per Slurry Tank Unit

Note: This formula applies only to the cylindrical portion of the slurry tank.

## 3.07 Specific Gravity of Slurry

## 3.08 Dry Solids per unit Volume of Slurry

CT = tons clinker per meter of slurry tank height

F = mass of dry feed per mass of clinker (kg/kg) or (tons/ton)

R = radius of slurry tank (m)

S = kg solids per m3 of slurry

sgs = specific gravity of dry slurry

sgw = specific gravity of slurry

## PROBLEMS AND SOLUTIONS

3.03 A given kiln uses a slurry of 32 percent moisture and the dry solids rate

has bee found to be 1,593 kg/kg clinker. What is the slurry consumption on this

kiln?

**Chapter 4**

**CHEMICAL AND PHISICAL PROPERTIES OF**

**MATERIALS USED IN CEMENT MANUFACTURING**

## 4.02 Bulk Densities of Common Materials

kg/m3

Aluminum 2595

Asbestos 3045

Brick (basic) 2400-2965

(alu.) 1520-1760

(firecly) 1360-1520

Cement (packed) 1506

(loose) 1200-1440

Clay (loose) 960-1200

Clinker 1440-1700

Coal (loose) 800-865

Coke 480-640

Concrete (reinforced) 2325

Gravel (loose) 1760

Ice 919

Iron (Cast) 7210

Iron Ore 2805

Kiln Feed (dry) 1360

Kiln Dust (loose) 1040

Limestone 1520

Mortar 1665

Fuel Oil 895

Sand 1520

Shale 2480

Slurry (@35 percent H2O) 1682

Steel 7850

Water 1000

## 4.03 Typical Coal Analysis

## 4.04 Typical Fuel Oil Properties

## 4.04 Typical Gaseous Fuel Properties

## 4.05 Barometric Pressure at Different Altitudes

## 4.06 Sieve Sizes

## 4.07 Coefficients of Linear Expansion

## 4.09 Properties of Air

## 4.10 Particulate Concentration in Gases

For gases:

1mg/liter = 24,04 m ppm

1mg/m3 = 0,02404 m ppm

where

m = molecular weight of gas

## 4.11 Selected International Weights

## 4.12 Selected Minerals and Ores

## 4.13 Classification of Minerals

a) Ingeous rock

These are formed by the intrusion or extrusion of magma or by volcanic activity. The

following minerals belong to this group:

Granite : Crystalline quartz and orthoclase

Orthoclase : Feldspar containing potassium

Plagioclase : Feldspar containing calcium and sodium

Quartz : Silicon dioxide

Biolite : A dark green form of mica consisting of silicate of Fe, Mg, K, or Al

Pyroxene : Silicate minerals containing calcium, sodium, magnesium, iron, or

aluminum

Olivine : Silicate of magnesium and iron

Magnetite : Oxide of iron

b) Sedimentary rock

These are formed by deposits of sedimentation. They can also consist of fragments

of rock deposited in water or by precipitation from solutions and organisms. The following

rocks belong to this group:

Gravel Shale Chalk

Sandstone Limestone Marl

Siltstone Gypsum Coral

c) Metamorphic rock

These are minerals that have been changed by the action of heat, pressure, and water.

The following minerals belong to this group:

Gneiss : Laminated or foliated metamorphic rock

Schist : Crystalline metamorphic rock with foliated structure along

parallel planes

Marble : Metamorphic crystallized limestone

Quartzite : Metamorphic sandstone

## 4.14 Chemical Formula and Molecular Weight of Common Minerals

# Chapter 5

FORMULAS AND DATA USED IN COMBUSTION

CALCULATIONS

**5.01 Termochemical Reactions**

## 5.02 Combustion Constants

Note: Volumes at 16oC and 760 mm Hg.

## 5.03 Heat Value of Fuel

The heat value of a fuel is usually determined in a calorimeter. For an approximate

indication, the heat value can also be calculated from the ultimate analysis. Values for C

(carbon), S (sulfur), H (hydrogen), etc., are expressed in terms of percent by weight for coal

and in terms of percent by volume for natural gas.

## 5.04 Conversion from “Gross” to “Net” Heating Value’

The net heating value accounts for the heat losses that are experienced for the

evaporation of the moisture in the fuel as well as the water that is generated by the

combustion of hydrogen. Heating values obtained in the calorimeter are “gross” values and

can be converted to the “net” basis by the following formulas:

In Europe it is the custom to express the heating value or fuel consumption in terms of

the “net” basis whereas in North America the “gross” heating value is generally used.

## 5.05 Analysis of Coal

a) Ultimate analysis

C + H + N + S + O + Ash = 100 percent (by weight)

where

C = percent carbon, H = percent hydrogen, N = percent nitrogen,

S = percent sulfur, O = percent oxygen.

The percent oxygen (O) is not determined by analytical methods but calculated by

difference to make the sum total equal to 100.

b) Proximate analysis

V + free C + ash + m = 100 percent

where

V = percent volatiles,

free C = percent free carbon,

m = percent moisture

The percent free carbon is calculated by difference to make the sum total equal to 100.

## 5.06 Methods of Expressing Solid Fuel Analysis

Analysis of solid fuels should be reported with a note containing a remark in respect to

the method in which the analysis is expressed. The following are the methods (basis)

frequently used:

a) “as analyzed”

b) “dry basis”

c) “as received”

d) “combustible basis” (moisture and ash free)

e) “as fired”

For inventory control purposes it is of advantage to express coal tonnage, heating

value and its composition on the “dry basis” to eliminate the fluctuations coal undergoes

when it is stored and exposed to weathering.

## 5.07 Conversion of Coal Analysis to Different Basis

Let

Y = percent C, S, N, or percent ash

O = percent oxygen

H = percent hydrogen

m = percent moisture

subscript:

a = “as analyzed” basis

d = “dry basis”

r = “as received” basis

f = “as fired” basis

c = “combustible” basis

a) To convert from “as analyzed” to “dry” basis

b) To convert from “dry” to “as received” basis

Multiply all components, except hydrogen, by the factor

c) To convert from “dry” to “as fired” basis

Multiply all components, except hydrogen, by the factor

Note: in b) and c) above, the percent hydrogen is calculated as follows:

d) To convert from „as received” to „dry” basis

Multiply each component, except the hydrogen, by the factor

e) To convert from “combustible” to “as fired” basis

Multiply each component, except the hydrogen, by the factor

f) To convert from “as received” to “combustible” basis

Multiply each component, except the hydrogen, by the factor

The following table shows clearly how the values of a coal analysis and the heating

value can change when the analysis is expressed in different terms.

## 5.08 Typical Coal Ash Analysis

For a cement chemist, it is important to know the chemical composition of the coal

ash. The majority of the ash, during the burning of coal, enters the clinker and modifies its

chemical composition. On coal fired kilns, it is not only important to maintain a uniform kiln

feed but also to fire the kiln with a coal of uniform composition. In plants, where coal

originates from several different suppliers, provisions should be made to blend these coals

before they are fired in the kiln. A typical analysis of coal ash is shown in the following:

## 5.09 Fuel Ignition Temperature

The approximate ignition temperature of various fuels are

ºC

Coal 250

Wood 300

Bunker C oil 200

Diesel fuel 350

Natural gas 550

## 5.10 Percent Coal Ash Absorbed in Clinker

The percent coal ash contained in the clinker can be calculated from the loss-free

analysis of the ash, raw mix, and clinker as follows:

Analysis

## 5.11 Effect of Coal ash on Clinker Composition

Changes in the composition of the clinker as a result of coal ash addition can be

calculated by the following method:

Analysis (loss-free)

## 5.12 Determination of Theoretical Fuel Consumption

Knowing the properties of the coal, kiln feed, and the exit gas allows an engineer to

calculate the coal consumption by using Dr. Kuhl’s formula:

Data needed:

a = constant, 0,266

b = percent carbon in dry coal

c = percent hydrogen in dry coal

d = percent nitrogen in dry coal

e = percent oxygen in dry coal

f = percent sulfur in dry coal

g = percent ash in dry coal

What is the coal consumption on this kiln?

### PROBLEMS AND SOLUTIONS

What is the net heating value of this coal expressed in terms of kcal/kg?

5.10 Given the following analysis on a loss free basis;

What percent ash does the clinker contain?

**Chapter 6**

**pH: HYDROGEN – ION – CONCENTRATIONS**

## 6.01 Definition of pH

The pH value of a chemical is indicated by the negative log of the hydrogen-ionconcentration

(hc +).

**6.02 Calculation of pH**

# P A R T II

B U R N I NG

**Chapter 7**

**TECHNICAL INVESTIGATION OF**

**KILN PERFORMANCRE**

## Introduction

The significant formulas for a study of the kiln performance and efficiency are given.

An engineer should follow the sequence in which the formulas are presented herein as many

calculation require the results obtained from earlier computations.

To simplify the engineers task, all the formulas are presented in the form of work

sheets that can be used to arrange the study in an orderly fashion. At the conclusion,

a summary sheet is also given to compile all the significant results of this study.

Data, formulas, and results are presented in metric system units by using the

appropriate worksheets in this chapter.

These worksheets can also be used to perform studies of parts of the kiln system

(e.g., the cooler operation). The reader should have no difficulties in selecting the appropriate

formulas from the worksheets in these instances.

For a complete study, it is essential that the kiln data be selected during a time when

the kiln operates in a stable and uniform manner.

## 7.01 Technical Information on kiln Equipment

Plant location:____________________________________ Kiln: _____________________

Kiln

Process: ___________________________________________________________________

Manufactured by: ____________________________________________________________

Year placed in operation: ______________________________________________________

Types of clinker produced: _____________________________________________________

Types of fuel burned: _________________________________________________________

Primary air source: ___________________________________________________________

Feeder type: ________________________________________________________________

Type of dust collector: ________________________________________________________

Dust processing: _____________________________________________________________

Preheater

Type: _____________________________________________________________________

Manufactured by: ___________________________________________________________

Year: _____________________________________________________________________

Cooler

Type: ____________________________________________________________________

Manufactured by: ___________________________________________________________

Year: _____________________________________________________________________

Other kiln equipment

Function Type Hp

……….. …….. ………

……….. …….. …………

……….. …….. …………

Date of investigation:_________________________________________________________

Tested by: _________________________________________________________________

# Chapter 8& 9

KILN PERFORMANCE AND EFFICIENCY

**Data needed**

Fuel Analysis (Oil or Coal – as Fired)

AA = Percent ash = ………..

AH = Percent hydrogen = ………..

AC = Percent carbon = ………..

AN = Percent nitrogen = ………..

AO = Percent oxygen = ………..

AS = Percent sulfur = ………..

AM = Percent moisture = ………..

AQ = Heat value (kcal/kg) = ………..

AJ = Heat value (kJ/kg) = ………..

CALCULATIONS

**9.01 Amount of Feed Required to Produce One Kilogram of Clinker**

**9.03 Potential Clinker Compounds and Clinker Factors**

Page 102 and 103 are missed

## 9.11 Products of Combustion

Note: For natural gas firing, use the formula 13.08 in chapter 13.

## 9.12 Weight of Gases from the Feed

Note: The assumption is made that wasted dust has been 50% calcined. Find a, b, f in 9.01

and k2 in 9.02.

## 9.13 Total Weight of Kiln Exit Gases

Adding the products in 9.11 and 9.12 gives the total weight of exit gas

## 9.14 Percent Moisture in Kiln Gas

## 9.15 Density of Kiln Exit Gas

a) At 0 C, 760 mm Hg

b) At prevailing pressures and temperatures

## 9.16 Volume of Moist Kiln Exit Gas

### 9.17 Kiln Performance Factors

a) Cooler air factor

b) Primary air velocity

c) Specific kiln surface area loading.

d) Specific kiln volume loading.

Using the “inside lining” kiln volume, the specific volume loading in terms of daily metric

tons production is calculated as follows:

e) Specific thermal loading of the burning zone.

**Chapter 10 & 11**

**HEAT BALANCE**

In the appendix, the reader will find graphs for the mean specific heat of gases and

solids that will be used in the ensuing calculations. In all the formulas given, “Q” denotes the

heat content (kcal/kg), “QJ” , and “c8” the mean specific heat in terms of (kcal/kg)(C), “cJ”

in terms of (kJ/kg)©.

HEAT INPUT

## 11.01 Heat Input from the Combustion of Fuel

## 11.02 Heat Input from Sensible Heat in Fuel

## 11.03 Organic Substance in Kiln Feed

It is assumed that the organic matter in the kiln feed has a constant heat value of

5028 kcal/kg and 21,036 kJ/kg.

## 11.04 Heat Input from Sensible Heat in Kiln Feed

## 11.05 Heat Input from Cooler Air Sensible Heat

## 11.06 Heat Input from Primary Air Sensible Heat

Include in this calculation only that amount of primary air which originates from the

atmosphere. Do not include the fraction of primary air that has its origin from the cooler.

## 11.07 Heat Input from Infiltrated Air Sensible Heat

When the temperature in the area where the majority of the infiltration takes place, is

significantly different from “T”, use the appropriate temperature for this calculation.

HEATS OUTPUTS

## 11.08 Heat Required for Clinker Formation

For “Q” in terms of kcal/kg, the result of 9.04 can be entered here directly.

Q = ………kcal/kg clinker

In the International system of units (SI) this heat fraction is calculated as follow:

## 11.09 Heat Loss with Kiln Exit Gas

The heat loss in the exit gas is calculated from the heat content of each individual gas

component. The weights of these components has been calculated in 9.13.

In terms of the International system of units (SI):

## 11.10 Heat Loss Due to Moisture in Feed of Slurry

The total weight of water, (wtotal H2O) can be found in 9.13. The remits obtained represents only the amount of heat that has to be expanded to turn the given weight of water into steam at 0 ºC. The heat losses associated with raising this steam to the kiln exit gas

temperature have been included in 11.09.

## 11.11 Heat Loss Due to Moisture in Feed or Slurry

## 11.12 Heat Loss with Clinker at Cooler Discharge

## 11. 13 Heat Loss at Cooler Stack

## 11.14 Heat Losses by Radiation on Kiln Shell

In the appendix find the heat transfer coefficient qm (kcal/ m2 h C) and qJ (kJ/ m2 h C) for

the average shell temperature, Tz, in each zone of the kiln.

## 11.15 Heat Loss Due to Calcination of Wasted Kiln Dust

Calculate first the percent calcination of the kiln dust:

Second, calculate the total carbonates in the kiln dust:

Note: Include this heat loss in the heat balance only for that fraction of the dust that is

wasted and not returned to the kiln

(find a, b in 9.01 and k2 in 9.02).

### Heat Balance

**Note: Unaccounted losses are calculated by difference**

**Chapter 12**

**TECHNICAL INVESTIGATION OF**

**THREE KILN MODELS**

### Introduction

Models of wet process, a dry process, and a suspension preheater kiln are given here

and their performance characteristics have bee calculated in accordance to formulas given

in this chapter. The data are selected values of kiln parameters typical to these types of kilns

when they are operated efficiently and properly maintained.

Data

Fuel analysis

(applied to all three kilns and stated on a “as fired” basis)

Summary of Kiln Performance Study Results

Note: Unaccounted losses are calculated by difference to make the two sides equal.

Note: Unaccounted losses are calculated by difference to make the two sides equal.

Note: Unaccounted losses are calculated by difference to make the two sides equal.

**Chapter 13**

**COEFFICIENT, AND**

**COMPUTATION FOR NATURAL GAS FIRING**

Compiled in this chapter, are the important parameters an engineer needs to complete

a kiln investigation as outlined in Chapters 8 through 11.

Here the engineer will find the graphs that show him at a glance the appropriate

specific heat and heat transfer coefficient to be used for his computations. The reader

is advised to make use of the appropriate graphs and formulas in accordance with the

particular system of units employed for his study.

The formulas shown in Chapter 8 through 9 apply to kilns fired with coal or fuel oil.

In this chapter, the appropriate formulas for gas firing which should be used in Chapter 8

and 9 are also shown.

## 13.01 Mean Specific Heat of Clinker (Base: 0 ºC)

## 13.02 Mean Specific Heat of Raw Materials (Base: 0 ºC)

Temperature (ºC)

**13.03 Mean Specific Heat of Exit Gas Components (Base: 0 ºC)**

## 13.04 Mean Specific Heat of Fuels (Base: 0 ºC)

## 13.05 Mean Specific Heat of Water Vapor (Base: 0 ºC)

## 13.06 Heat Transfer Coefficients for Heat Loss on Kiln Shell

## 13.13 Computations for Natural Gas Firing

Analysis of natural gas fuels are usually expressed in terms of percent by volume with

is the same as molar proportions. The formulas given below allow for combustion

calculations in terms of the unit production of clinker. Hence, the results obtained are

expressed in the same terms as the results computed in this study for liquid and solid fuels.

Data required:

Combustion air required (items 9.07 and 9.07 for natural gas firing)

Weight of combustion air entering kiln (items 8.08 and 9.08 for natural gas firing)

Products of combustion (items 8.11 and 9.11 for natural gas firing).

**Chapter 14**

**USEFUL FORMULAS IN**

**KILN DESIGN AND OPERATION**

## 14.1 Cooling of Kiln Exit Gases by Water

Any moisture introduced into the gas stream is ultimately transferred into superheated

steam and, in doing so, absorbs heat and cools the exit gases. The equations can be solved

for any one of the unknowns if the other variables are known.

## 14.02 Kiln Feed Residence Time

The approximate time taken by the feed to travel the length of the kiln can be

calculated by the following formulas:

where

T = travel time (min)

L = length of kiln (m)

N = kiln speed (RPM)

D = kiln diameter (m)

S = slope of kiln (m/m)

**14.03 Kiln Slope Conversion**

Slope is often expressed also as a percent of the kiln length

L = kiln length (m)

## 14.04 Kiln Sulfur Balance

If a kiln performance study has been completed in Chapter 8 and 9, the necessary data

below can be obtained from the data sheet given in these chapters.

Note : Exit gas concentrations are calculated by difference to make the two sides equal

in the total.

## 14.05 The Standard Coal Factor, Combustion Air Requirements

To determine the approximate combustion air needed to burn a given unit weight

of coal, the formulas given below can be used when no ultimate coal analysis is available.

The combustion air requirements include here 5% excess air.

kg air/kg coal = 10,478 SCF

SCF = standard coal factor

a = percent moisture in coal (as fired)

B = heat value of coal (kcal/kg as fired

## 14.6 Cooler Performance

## 14.07 Combustion Air Required for Natural Gas Firing

In the absence of a complete analysis of the gas, the air requirements can be estimated from

the following table. This table is based on natural gas with a heating value of 9345 kcal/m3

## 14.8 Products of Combustion on Natural Gas Firing

One standard cubic meter of natural gas, when burned, yields the following

combustion products:

CO2 = 2,0778 kg

H2O = 1,6340 kg

N2 = 11,1003 kg

O2 = 0,3669 kg

Total = 15,179 kg

## 14.9 Percent Loading of the Kiln

## 14.10 Cross – Sectional Loading of the Kiln

The formulas given here are applicable in the metric system of units

## 14.11 Flame Propagation Speed

For coal fired kilns, the primary air velocity should be at least twice as high as the

flame propagation speed to prevent flash backs of the flame. Flame propagation is usually

considerably lower than the velocity needed to convey coal dust by means of primary air into

the kiln. Therefore, the minimum velocity necessary to convey coal without settling in ducts

takes precedence over flame propagation speed when setting air flow rates or designing new

burners (minimum velocity needed in ducts to prevent settling: 35 m/s). Coal burners are

usually designed to deliver a tip velocity of 45 to 70 m/s.

## 14.12 Kiln Drive Horsepower

a) Friction horsepower

b) Load horsepower

Total kiln drive horsepower

## 14.13 Theoretical Exit Gas Composition, by Volume

In chapter 9, Section 9.13, the total weight of the exit gas components were

calculated. In many studies, it is desirable to express this composition in terms of percent

by volume. The following steps are taken to accomplish this.

Step 1: Convert weights of each component into kg – moles as follows:

Step 2: To obtain the percent by volume of any component, divide the moles of the

component by the total moles of gas.

## 14.14 Conversion of Specific Heat Consumption into Annualized Costs

For U.S. currency:

For any other currency denomination:

a = fuel costs (dollars/ton)

b = fuel heat value (Btu/lb)

c = kiln output (tph)

d = percent operating time (decimal)

A = cost per kg fuel

85

B = fuel heat value (kcal/kg)

C = kiln output (kg/h)

Qe = specific heat consumption (Btu/t)

Qm = specific heat consumption (kcal/kg cl.)

## 14.15 Theoretical Flame Temperature

(This formula applies only to oil or coal fired kilns)