ENERGY MODELING OF THE PYROPROCESSING OF CLINKER IN A ROTARY CEMENT KILN

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ENERGY MODELING OF THE PYROPROCESSING OF

CLINKER IN A ROTARY CEMENT KILN

Presented by

VEN V. VENKATESAN, PE, CEM

VGA Engineering Consultants, Inc.

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Presenter

Ven is working in the field of energy management for the past 33 years.

A Master’s degree holder in Chemical Engineering, with specialization in Plant Design, he has conducted Energy Audits over 120 energy intensive process industries located around the world and identified energy savings worth over $100 millions/yr.

Worked as Energy Manager in a Petroleum refinery and also in an integrated Steel Mill complex.

Twice awarded certificates of appreciations by US Dept. of Energy, for outstanding leadership & exceptional skills.

For more details about Ven, kindly visit: http://www.vgaec.com

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ENERGY MODELING OF THE PYROPROCESSING OF CLINKER IN A ROTARY CEMENT KILN

The main raw material for the cement manufacturing is the Lime stone. Pyro-procesing is a 2-step process (Calcination and Clinkerization) through which powdered limestone is converted into clinker. The CO2 in limestone is removed during Calcination & the powdered mass is fused into lumps at temperatures of 2600oF during Clinkerization.

The Pyro-processing (PP) section of a dry-process cement plant consists of the following major equipment

1. Cyclone Preheaters (4 - 6 stages of cyclones preheating the feed)

2. Pre Calciner (where fuel-fired flash furnaces complete the Calcination)

3. Rotary Kiln (where the calcined-powder is fused into Clinkers)

4. Grate Cooler (where the Clinker is cooled for further handling)

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Simplified block diagram of Pyro-processing

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Equipment line-up of Pyro-processing

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The energy model is a mathematical model, where the operating process parameters are linked to the energy consumption of Pyro-procesing (PP)

Typical operational parameters in the PP section are:

- Raw Meal feed rate to the Kiln system,

- Fuel firing rates at Precalciner & at the Rotary Kiln,

- Total air supply to the PP section

- Operating temperatures maintained at the PP section

Energy Model is useful to analyze & evaluate the operational improvements at the PP section.

ENERGY MODEL OF PYRO-PROCESSING

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Sankey diagram from the Pyro-processing Energy Model

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The energy model is useful to analyze / evaluate the operational improvements at the Pyroprocessing (PP) section.

Typical operational improvements in the PP section are:

- Increase feed rate, by minimizing the false air ingress in the Preheaters

- Increase feed rate, by controlling the excess air at Kiln & PC burners

- Maximize the secondary & tertiary air temperatures, by optimizing the Cooler air balance-point

- Minimize the radiation losses, by fixing with improved insulation

UTILIZATION OF THE ENERGY MODEL

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Basis: 4000 tpd Clinker

Reference ambient temp: 25oC4000 4000 4240 4240 4240

HEAT INPUTHeat input through Raw Meal

Clinker production rate T/hr 166.7 166.7 176.7 176.7 176.7Raw Meal feed rate (@ 0.65 Clinker to Raw meal ratio) T/hr 256 256 272 272 272

Raw Meal feed temperature (typically around 70 to 100oC) oC 75 75 75 75 75Heat content of the Raw Meal GCals/hr 3.50 3.50 3.71 3.71 3.71Share of Heat input by Raw Meal 2.3% 2.4% 2.4% 2.5% 2.5%

Required Heat input from Fuel (from Heat balance based on Heat Output)Heat Input through Coal GCals/hr 145.64 144.34 151.50 142.80 141.80Share of Heat input by Coal (Fuel) 97.7% 97.6% 97.6% 97.5% 97.5%Heating Value of Coal kcals/kg 7032 7032 7032 7032 7032Quantity of Coal fired at both the Kiln & Precalciner T/hr 20.71 20.53 21.55 20.31 20.17

TOTAL HEAT INPUT TO THE KILN SYSTEM GCals/hr 149.14 147.84 155.21 146.51 145.51

HEAT OUTPUTHeat in Clinker

Temperature of Clinker when coming out of Cooler oC 120 120 180 180 180Sensible heat in Clinker GCals/hr 3.01 3.01 5.20 5.20 5.20Share of Heat taken out by Clinker 2.0% 2.0% 3.4% 3.6% 3.6%

Heat of ClinkerizationTypical value of Clinkerization heat in Cement Kilns kCals.kg of Cl. 423 423 423 423 423Heat absorbed by the Clinkerization process GCals/hr 70.50 70.50 74.73 74.73 74.73Share of Heat consumed by the Clinkerisation process 47.3% 47.7% 48.1% 51.0% 51.4%

Heat content of Preheater exhaust gasesPreheater exhaust gases comprises of fluegases from coal combustion, CO2 released from Calcination and False air Ingress in the Preheater sectionsCO2 release from Calcination of Raw Meal

CaCO3 content in Raw Meal 78% 78% 78% 78% 78%

CO2 release from Raw Meal Calcination T/hr 56.4 56.4 59.8 59.8 59.8

Reported Coal/Clinker ratio at But Son 0.123 0.123 0.123 0.123 0.123Amount of Comb. Air requiried to burn this coal T/hr 197.5 197.5 214.3 214.3 214.3Stack gas quantity at no excess air (theoretical stack gas) T/hr 213.2 215.1 228.0 228.0 228.0Moles of Fluesgas from combustion of coal kg Moles/hr 7351 7417 7862 7862 7862

Moles of CO2 formed from calcination of raw meal kg Moles/hr 1282 1282 1359 1359 1359

Total quantity of gases passing the PH section in ideal conditions kg Moles/hr 8633 8699 9221 9221 9221Excess air is added at the burner and through openings in PH/PC/Kiln sections(leaks) to raise the free Oxygen from zero %.

Oxy content of stack gas as measured at PH outlet (O2%) by Vol 4.15% 3.00% 3.00% 3.00% 3.00%

Total stack gas quantity at PH outlet (@ the measured O2% levels)

Excess Air added at Burner & as False Air 24.6% 16.7% 16.7% 16.7% 16.7%

Moles of air added at Burner & as False Air up to PH fan kg Moles/hr 2126 1450 1537 1537 1537Total quantity of stack gases entering PH fan kg Moles/hr 10759 10149 10758 10758 10758

Total volume of stack gases entering PH fan NM3/hr 241001 227342 240982 240982 240982Total mass of stack gases leaving the PH fan kgs/hr 312010 294326 311986 311986 311986

Typical temperature of the stack gases leaving PH fan oC 354 354 354 354 354Heat content in the PH gases GCals/hr 39.10 36.88 39.10 39.10 39.10Share of Heat taken out by Preheater exhaust gases 26.2% 24.9% 25.2% 26.7% 26.9%

Improved Insulation at Preheater section

Observed Condition

At 10% less False Air

Earlier Improved kiln rate

At optimized Cooler air flowUnit

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Basis: 4000 tpd Clinker

Reference ambient temp: 25oC4000 4000 4240 4240 4240

HEAT OUTPUT (contd . . .)Heat content in the Cooler vent air

Total Cooler air supply at the Clinker NM3/hr 441667 441667 441667 353333 353333Total Cooler air supply at the Clinker kgs/hr 571801 571801 571801 457440 457440Air is suuplied for combustion as Secondary & Tertiary air Total Combustion Air supplied kgs/hr 246150 230424 250052 250052 250052Estimated share of Primary Air of the total combustion air 10% 10% 10% 10% 10%Primary Air supplied directly from Fans kgs/hr 24615 23042 25005 25005 25005Secondary & Tertiary air supply from Cooler kgs/hr 209227 195860 212544 212544 212544Vented air quantity from the Cooler kgs/hr 362573 375940 359257 244897 244897

Temperature of the Cooler vent air oC 240 240 240 240 240Heat content in the Cooler vent air GCals/hr 27.58 28.60 27.33 18.63 18.63Share of Heat taken out by Cooler vent Air 18.5% 19.3% 17.6% 12.7% 12.8%

Heat lost by radiation from the Kiln systemRadiation heat loss at Kiln sectionTotal outside surface area of the Kiln sq.m 1356 1356 1356 1356 1356Radiation heat loss from the Kiln system (@6% estimated) GCals/hr 8.95 8.85 8.85 8.85 7.85Radiation Loss in the total heat output from the Kiln system 6.0% 6.0% 5.7% 6.0% 5.4%

TOTAL HEAT OUTPUT FROM THE KILN SYSTEM GCals/hr 149.14 147.84 155.21 146.51 145.51

Specific Heat Consumption kCals/kg of Cl. 873.8 866.1 857.6 808.3 802.6

Btu/lb of Cl 1576 1562 1547 1458 1448

Savings in Heat input kCals / kg of Clinker 7.79 16.3 49.2 5.7

Annual Heat Savings at improved Clinker rate GCal / Yr 10899.03 24173.06 73084.35 8400.00

Reduction in specific heat consumption Btu/lb of Cl 14 15 89 10

Energy Savings - by each improvement actions US$ /Yr $81,200 $180,100 $544,400 $62,600

Improved Insulation at Preheater section

Observed Condition

At 10% less False Air

Earlier Improved kiln rate

At optimized Cooler air flowUnit

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Any Questions ?

ENERGY MODELING OF THE PYROPROCESSING OF CLINKER IN A ROTARY CEMENT KILN

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