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Cement industry

Sector Highlights

Cement is one of the basic construction materials. From the aspect of availability of raw material, cement sector is considered as a very important sector in Nepal. It falls under the category of heavy industry. Nepal has good deposits of the main raw materials namely the calcium carbonate or the Limestone and Silica rich clay that makes environment conducive for growth of cement industry.

At present around 59 cement industries in private sector have been registered in Department of Industry. It is estimated that annual gross consumption of cement in Nepal at present is around 2,500,000 MT. Annual increment of demand for cement in Nepal is considered to be around 20 percent. It is estimated that around six billion NPR of investment has been made by private entrepreneurs in cement sector. Couples of big cement industries of 900 to 1,500 TPD based on rotary kiln technology are in pipe line and some of them will come into operation by next couple of months. It is expected that after some years, Nepal will be self sufficient in Cement.

Census of Manufacturing Establishments carried out in the fiscal year 2006/07 by the Central Bureau of Statistics (CBS) has shown under Nepal Standard Industrial Classification of 2694, the number of manufacturing of Cement, lime and Plaster to be 25 with employment of 2,225 persons. The value of output of these establishments is NPR 6.962 Billion with input of NPR 5.353 Billion and value addition of NPR 1.609 Billion.

Process

Cement manufacturing from Limestone involves following main steps:

  1. Mining
  2. Crushing
  3. Raw meal grinding
  4. Pyro-processing
  5. Cement grinding

Cement manufacturing from clinker involves only the following main steps:

  1. Crushing
  2. Mixing
  3. Milling/Grinding
  4. Weighing & Packing

Process flowchart of limestone based cement plant

Process flowchart of Clinker based cement plant

Energy Use

Main sources of energy used in the Cement industries in Nepal are electricity and coal. Coal is mainly used in the kilns for calcination in limestone based units and in some cases also used for electricity generation in plants having co-generation system. Approximate share of electrical energy used in Nepal's cement industry is 9 %; thermal energy amounts to 91 %.

Figure 1: Energy Use in Cement Industry in Nepal

Baseline study undertaken by GIZ/NEEP in 2012 for the Cement sector has found the specific energy consumption to be considerably above the regional benchmark (see table). That means there are huge saving potentials by implementing energy efficiency and upgrading technologies.

Tabel 1: Specific energy comsuption in Nepalese Cement industries (GIZ/NEEP, 2012)

Major energy consuming section in Nepalese cement plants are:

Thermal equipment (only applicable in limestone based units)

  • Primary/Secondary Crushing
  • Milling (Ball mills and roller mills)
  • Homogenization
  • Calcination
  • Grate cooling (clinker cooling)
  • Fan Systems
  • Dust collection

Electrical equipment

  • Electrical Distribution transformer & Power systems
  • Electrical drives
  • Diesel Generating Sets
  • Compressors
  • Lighting system
  • Co-generation plant
  • Material handling equipments.

References

  • GIZ/NEEPl, 2012: Baseline Study of Selected Sector Industries to assess the Potentials for more efficient use of energy.
  • ESPS-DANIDA, 2000-2005: Cleaner Production report of Cement industry
  • Confederation of Indian Industry: Investors manual for Energy Efficiency
 

Energy Saving Potential

According to a baseline study in 8 energy-intensive industrial sectors of Nepal energy cost of product value in limestone-based cement industries is with 48 % highest, followed by cold storage (38 %), Fixed Chimney brick kilns (31 %) and pulp and paper sector (20 %). In clinker-based industries energy cost amounts to at least 5 % of product value. Energy saving potential on the product cost is estimated to be highest for the Limestone based industry (above 19%).

In clinker based cement industries are estimated to be electricity up to 45,854 MWh could be saved. In limestone based cement industries of Nepal saving potentials amount to 35,390 MWh electrical and 1,598,359 GJ thermal energy (see Table). By implementing energy efficiency monetary savings in clinker-based factories and limestone-based factories amounts to about 38 Crore and 110 Crore Lakh Nepalese Rupee, respectively.

Experience from the past have identified many energy saving options for the cement sector that are highly profitable with payback periods of investment of less than 2 years. The following table shows some implemented examples option in Nepalese cement factories with the respected payback.

Energy Saving Tips

In following areas energy saving opportunties can be achieved:

Mines and Crushers

  • Increase operating capacity of primary & secondary crusher
  • Reduce idle run of crushers and belts
  • Reduce idle operation of dust collection equipment

Raw mill, grinding and Storage

  • Avoid idle running of raw mill conveyor system (Auxiliaries)
  • Avoid idle operation of raw mill lubrication system
  • Optimize starting & stopping sequence of raw mill (to minimise idle running of fans)
  • Minimise false air entry in raw mill system
  • Use vertical roller mill instead of ball mill
  • Control raw meal feed size by installation of tertiary crusher
  • Install belt and bucket elevator in place of pneumatic conveying
  • Installation of efficient mill intervals – diaphragm and liners
  • Install online X-Ray analyser for raw meal
  • Install slip power recovery system / VFD for raw mill fan / ESP fan

Kiln

  • Install CO and O2 analyser at kiln inlet and preheating outlet
  • Maintain proper kiln seal (inlet and outlet) to avoid false air infiltration
  • Reduce leakages in the pre-heater system
  • Utilise the cooler waste heat for fly ash / slag / coal
  • Install soft starters for clinker breaker
  • Install VFD for cooler fans and cooler ID fans
  • Optimize the cooler exhaust chimney height to reduce the exhaust fan power consumption
  • Install water spray in cooler to minimise fan power consumption
  • Install system for firing waste tyre, bark, rice husk, groundnut shell and urban waste in pre-calciner
  • Conversion from pneumatic conveying of kiln feed to mechanical mode
  • Conversion from single channel to multichannel burners
  • Replace planetary cooler with grate cooler
  • Replace conventional coolers (planetary / grate) with high efficiency coolers

Coal yard & coal mill

  • Elimination of spontaneous combustion, by proper stacking
  • Avoid idle running of coal conveyor & crusher
  • Optimise starting & stopping sequence of coal mill to reduce idle operation of fans
  • Maintain higher residue for pre-calciner firing
  • Increase residue of coal mix, if possible

Cement Grinding, Storage & Packing

  • Water spraying on the clinker at cooler outlet (Temp above 90oC, consumes more grinding energy)
  • Reduce cement mil vents and recirculate to reduce cement loss
  • Avoid idle running clinker conveyor – dust collector fan
  • Avoid idle running of cement silo exhaust fans
  • Optimise starting & stopping sequence of cement mill to avoid idle running
  • Increase production of blended cement (PPC and PSC)
  • Use of grinding aids
  • Optimise water spray compressor capacity
  • Optimise cement grinding fineness – Install particle size analyser and optimise the particle
    size distribution
  • Install belt conveyor / screw conveyor / bucket elevator system instead of pneumatic conveying
  • Installation of roller press / impact crusher / VRM as a pre-grinder before the ball mill

Compressors & Compressed Air System

  • Eliminate compressor air leakages by a vigorous maintenance programme
  • Maintain compressed air filters in good condition
  • Install compressed air traps for receivers
  • Optimise compressor discharge pressure
  • Install screw compressors with VFD in place of old compressors
  • Replace multiple small units with single larger units
  • Install intermediate control system for compressed air systems

Electrical System

  • Avoid unnecessary lighting during day time
  • Use energy efficient lighting
  • Distribute load on transformer network in an optimum manner
  • Improve power factor
  • Individual compensation
  • Group compensation
  • Centralised compensation
  • Replace over sized motors
  • Replace with energy efficient motors
  • Use VFD for low / partial loads
  • Convert delta to star connection for motors loaded below 50% of full load (for occasional peak load provide automatic-star-delta-convertor)
  • Install energy saver in fluorescent lighting circuit
  • Fixing of light fixtures at optimum height
  • Operate lighting system at lower voltage (say 360 V in 3 phase)
  • Use servo stabiliser in lighting circuits
  • Replace conventional fluorescent tubes (40 W) with slim tubes (36 W)
  • Optimise system operating voltage level
  • Install demand controller for maximum utilisation of demand
  • Use of electronic ballast in place of conventional chokes

DG Sets

  • Increase loading on DG sets
  • Install VFD for cooling tower pumps and fans
  • Convert electrical heating furnace to thermal heating
  • Install WHR system in DG set for preheating furnace oil
  • Install low pressure drop cyclones for pre-heater
  • Install latest high-level control systems for kiln, raw mill and cement mills
  • Install WHR systems to recover heat from pre-heater and cooler exhaust

References

  • NEEP/GIZ-Nepal, 2012: Baseline study of selected sector Industries
  • ESPS-DANIDA, 2000-2005: Cleaner Production report of pulp and paper industry
  • Confederation of Indian Industry: Investors manual for Energy Efficiency
 
 

EEC Factsheet: Energy Efficiency for Cement Industry in Nepal - This fact-sheet summarizes energy saving potentials in Nepalese cement sector. It also give information on monetary savings by implementing energy audit and energy efficiency options in the industries. The fact-sheet is based on the findings of "Baseline Study of Selected Sector Industries to assess the Potentials for more Efficient use of Energy in Nepal" conducted by GIZ/NEEP Program in 2012.

Industrial Efficiency Technology Database – Cement  Institute for Industrial Productivity's package of databases on technology, policy, financing and supply chain initiatives that are publicly available and offered free of charge, as part of our mandate to increase industrial energy productivity in energy-intensive sectors. It aims to help decision makers identify technologies and measures that improve productivity and profits while reducing energy consumption and CO2 emissions in industry, and assist companies in assessing the cost-effectiveness of energy efficiency investment options.

Energy Manager Training India – Cement Sector Knowledge base and platform for energy auditors in India established by Bureau of Energy Efficiency India and supported by Indo-German Energy Program (IGEN). The webpage contains a database of industrial processes and respective energy saving measures as well as a directory of energy efficiency professionals and technology suppliers from India.

Energy Efficiency Guide for Industry in Asia – Case Studies Best practices fact sheets of cement industries from various Asian countries that were audited and implemented energy efficiency measures during UNEP funded project on t"Greenhouse Gas Emission Reduction from Industry in Asia and the Pacific" (GERIAP) until 2006.

Benchmarking and Energy Saving Tool (BEST) for Cement "Benchmarking and Energy Saving Tool (BEST) for Cement" is a process-level benchmarking tool developed by Lawrence Berkeley National Laboratory and Energy Research Institute in China.