Code No: TMS049 Price: 1350 Category: Energy Conservation

Table Of Contents

• Introduction
• Current cement industry profile
• India
• Current manufacturing technology status India/global
• Current energy conservation pattern
• Current status
• Energy conservation measures/technologies
• Energy conservation support infrastructure
• Energy conservation constraints
• Emerging energy conservation technologies
• Energy conservation technology demand potential/savings
• Recommended action plan for energy conservation technologies.
• Annexures The report is supported by 62 annexures: some selected annexures are: Manufacturing process description, Thermal energy balance,
• Energy consumption and capacity utilisation,
• compressed air utilisation, specific energy consumption Vs specific surface cement, Foreign turnkey suppliers,
• cement system flow diagram, Handling municipal waste as fuel,
• Energy saving potential through different Technology (based on Plantcluta)

Cement Industry Profile

Current installed capacity of cement in the country is 64 MnT/year. Total current domestic cement demand in 1990-91 was 40 MnT. The expected demand projected upto 1994-95 is 65 MnT.

Large plants have 92% share of the total capacity, the balance is with mini cement plants. Of the total capacity 84% of plant capacity is in private sector and balance in public sector. Three states M.P., A.P. and Rajasthan together account for 50% of the industry’s capacity.

At present 64% of the capacity is in large size kilns beyond 1000 tpd. Out of this 3000 tpd and above capacity plants form 42% of the capacity. The standards size of the kiln now is 3000 TPD.

Energy efficient dry process plants account for 81% of the industry’s production with wet process constituting around 16%. The balance 3% is semi dry/wet process plants.

Majority 95% of the production is in rotary kilns while less than 5% is in vertical shaft kilns which is generally in use for mini cement plants.

OPC (ordinary Portland Cement) account for 70% of the production. PPC (Portland Pozzolana Cement) for 19% and PSC (Portland slag cement) for 10%. The percentage of OPC has increased to 70% from 21% in 1981-82.

Manufacturing Technology Status

Raw material Preparation Process

Currently mining is generally done with semi-mechanized methods. Computerized mine planning is now being used by few modern plants. Most of the crushing operation is performed with multistage crushers of small capacity. New plants are now shifting to single stage impact crushers. Transportation of the material from the mines is generally with dumpers. Some of the plants are now shifting to belt conveyors using inpit crushing.

RM grinding technology has progressed from the use of open circuit ball mills to close circuit ball mills with high efficiency separators and improved mill internals. Vertical roller mills have now firmly established themselves for these operations.

Use of computerized on line X-ray analyzers for raw mix optimization has become an essential feature for all modern plants.

Burning Process

All plants commissioned after 1970 have been on dry process kilns. From conventional 4-stage preheater kiln system the current trend has been towards New Suspension Preheater (NSP) kilns with precalcinator having 5-stage preheater systems. Of the total capacity 44% is accounted by NSP) kilns, 25% by SP kilns, 16% by long wet process kilns and balance by other.

Most of the modern plants have now adopted computerized kiln control system with few of them having gone for expert systems.

Clinker Grinding

Currently most of the plants are using close circuit ball mills for cement grinding with mechanical separators. Many are shifting to high efficiency separators, improved mill internals and modified flow control diaphragms.

Energy Consumption Pattern

The current energy bill is approx. Rs. 2000 crores in power and fuel (12 million tons of coal/year and 7x106 units of power/year) with roughly equal share of both power and fuel in value.

Coal constitutes almost 99% of the total fuel used in the cement production. In case of power almost 17% of the cement production is through captive power sources requiring around 54 million liters of diesel.

Current Energy Consumption of India compared to World average is indicated below:

Among various countries, Japan Probably exhibits the lowest average thermal energy consumption of 710 kcal/kg and 103 kwh/t for the dry process.

Our energy consumption is almost 12% higher then world average and 17% higher than the best managed countries for dry process. Roughly 15-20% of our total capacity is operating at the world average standards of efficiency.

Among the various process centres in the plant almost 100% of thermal energy is consumed by kilns whereas for power almost 2/3rd consumption is for grinding operations of raw material, cement, and coal.

The energy consumption performance over the year indicated that average heat and power consumption have come down drastically. There has been on an average 2.5 % reduction in specific energy consumption over the years as indicated.

The reduction has generally been due to technology improvements i.e. shifting to SP and NSP kilns from long dry kilns, computerized control, optimization of kiln performance, switching to vertical roller mills, use of high efficiency separator and improved mill internals etc.

Specific energy consumption varies widely from plant to plant depending upon individual specific conditions. The factors effecting energy performance are plant capacity, capacity utilization, technology level, control system, product mix, in addition to may other external factors like quality of raw material (lime), coal and power supply etc. accordingly fixing up of energy consumption norms is a very difficult exercise and has to be based on in depth studies.                                               Back

Current Status of Energy Conservation Measures
Among the major energy conservation measures are:

• House keeping and operational control
• Process optimization
• Product innovation and fuel substation
• Waste heat utilization
• Technology/system upgradation

Among the house keeping measures, correct motor loading, prevention of false air entry in kilns and mills, preventive / condition monitoring play a very useful role in brining down the energy consumption.

Energy auditing and creation of energy conservation cell in the plants are very crucial for the success of energy conservation drive and for creating suitable culture in the organization.

Among the process optimization measures raw mix optimization, ball mill optimization, control of primary air in the kiln and clinker quality improvement play key role.

Diversification of cement quality such as PPC and PSC are known to reduce specific energy significantly. Over the years their percentage has in fact decreased in the overall mix. This may be due to general lack of availability of pozzolanic material near the site and also due to general belief that quality of PPC is inferior to OPC which is infact not true.

Fuel substitution has made a small beginning in the form of lignite in place of coal. Nothing much has been achieved by way of using natural gas or waste fuels.

Among the waste heat utilization measures the use is only being made to the extent of using preheater and cooler exhaust gases for drying raw meal. Beyond this the heat is not recovered. 5-stage preheater system have been installed to further recover heat from waste gases. Use of cogeneration system have not made any beginning.

Among the energy saving technologies the prominent areas are vertical roller mills for RM grinding, use of high efficiency separators in close circuit mills, use of improved mill internals, NSP kilns with latest precalcinator designs and computerized control systems with expert systems.

Support Infrastructure

Among the essential features of support infrastructure are:

• Fuel Poor coal quality, uncertain supply of lignite and non-availability of natural gas.
• Power Unreliable and poor supply
• RM Quality Generally marginal grade lime stone available.

• Cement Adequate capacity, all collaboration ventures Machinery almost 25% import content.
• Instrument Lack of sophisticated instruments for computer process control. Mostly imported.
• System Basic equipment design, detail engineering Design lacking. Basic system know how provided by collaborators
• Consulting Wide range offered but lack in latest design Support and system concept. Lack specialized cadres. Limitation in converting recommendations into practical solutions

• R&D Support Adequate but special energy conservation related projects to be added
• Energy Audit services Adequate
• Energy Mostly exists for large plants but not very Management productive due to multiple roles of the key individual vested with this responsibility

• Govt. Support More needs to be done on legislation front and overcoming of infrastructural bottle necks
  Constraints

The various constraints applicable to the industry are poor quality of coal and power supply; technology obsolescence, non-availability of reliable energy conservation devices; lack of incentives for cogeneration systems; poor reliability of expertise; attitudinal problems among plant personnel; lack of information on technology evaluation; lack of information sharing; deficiency of trained man power; poor training facilities and absence of proper organizational structure etc.  Back           

Emerging Technology Trends

Among the major emerging trends are:

• Use of inpit crushing through mobile crushers and belt conveyors has potential of reducing energy cost by 20-40% in transportation.
• Use of gyrator crushers (600-800 tph). May result in almost 30-50% saving in specific power consumption over jaw crusher.
• Roller mills with external recirculation system for RM grinding resulting in saving in power by 10% compare to systems without external circuit.
• Introduction of roller presses combined with ball mills form/cement grinding. 20-30% power saving may be possible compared to ball mills.

Use of roller presses alone with high efficiency separators. Upto 50% of specific power requirement compared to simple ball mills.
Use of roller mills for blast furnace slag grinding. Almost 10-15% power saving compared to grinding in ball mills. The power of move than 50% of that required by tube/ball mills could be saved.
  Horizontal impact crusher for clinker grinding. Reduction of power consumption by over 35% compare to conventional system.

•   Use of computerized mill control
•   Enlargement of kiln size to 10000 tpd, kilns with low LD ratio less than 1:10 leading to reduction in radiation losses.
•   Introduction of recirculating feed calciners which may result in fuel savings upto 7-8% compared to conventional calciners.
•   Use of high performance refractory material resulting in saving of fuels upto 2-5%.
•   Computerized refractory control system.
•   Use of waste fuels like waste rubbers, municipal waste and sewage sludge etc. Upto 25% substitution of fuel possible.
•   Use of artificial intelligence system for kilns which may result in fuel savings between 5-7%.
•   Computerized chemical control system resulting in energy savings upto 20%.
•   Introduction of PGNAA (Prompt Gamma Neutron Activation Analyses) technology for chemical control
•   Installation of dense phase conveying system
•   Low temperature clinker which has potential for saving of heat consumption upto 30% and power consumption upto 15%.
•   Electron beam processing technologies for cement.
•   Use of lime stone extenders.

Technology Evaluation

The viability of each of the energy conservation technology option has been discussed in the report. The import highlights are summarized in table below. The most important criteria for implementing energy conservation technologies is the pay back period. Any technology having more than 2 year pay back period does not seem to interest the plant managements.

Technology Demand Potential/Outlook of Energy Saving

Based on detailed consideration of various factors it is assessed that following savings are possible in energy consumption by 1995.

EXPECTED ENERGY SAVINGS - 1995

A total saving of 13-15% (valued at Rs. 286 crores) is possible in power and thermal energy respectively by 1995 over the current average consumption in existing capacity. The envisaged investment is around Rs. 780 crores mostly in technology related areas. The expected investment in energy saving equipments for new projects and substantial expansions may be Rs. 1000 crores over the next 5 years.                                                                                                                         Back

Recommendations

Among the major recommendations are:

• Setting up an apex body to give thrust to various energy conservation programs
• Creation of energy consumption data bank to help formulate energy conservation policies and strategies.
• Development of energy consumption norms from industry, which are specific to individual unique characteristic of plants.
• Evolving of energy information exchange system among various functionaries.
• Introduction of training programs/ refresher courses, setting up of in plant kiln and mill simulators and well conceived HRD program.

• Sponsoring of special R&D projects on energy conservation sulted to Indian conditions.
• Development of engineering capabilities vertical roller mills, roller presses, liner metallurgy, micro processor based control systems, waste fuel handling technologies etc.

• Effecting fuel substitution through use of Natural gas and waste fuels like waste rubber / tyres, municipal wastes etc. upto 25% substitution of fuel may be possible through use of waste fuels.
• Switching over to LSHS (low sulphur heavy stock) based captive power plants in place of DG sets.
• Leaving the balance wet process plants to market forces.
• Among the plant specific measures proposed are:

• Setting up of energy conservation cell
• Conducting energy audit study.
• Setting up of house keeping and operational control standards
• Deter house keeping and controls through proper loading of motors, stopping idle running, PF and Load factor improvement, preventive maintenance and condition monitoring of equipments use of captive power for kiln running and prevention of false air etc.

• Optimization through raw mix optimization, primary air control, ball mill optimization, material fineness control and use of grinding aids, mineralizers, slurry thinners and clinker quality
• Manufacture of blended cements like OPC and PSC.

• Technology upgradation improved mill internals and diaphragms, closed circuit grinding with high efficiency separators, kiln replacements, computerized process controls, increased preheater stages, use of low pressure drop cyclones etc.
  Use of energy saving devices like variable frequency drives, slip power recovery systems, fluid couplings, soft starts, high efficiency fans, flat belts, helical gears etc. the pay back periods are generally less than 2 years for these devices.
  Use of high pressure roller presses for clinker grinding and vertical roller mills for RM grinding for new projects are substantial expansions.

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