Introduction:
Cement
production contributes around 8% of the anthropogenic CO2 (carbon dioxide)
emissions globally.
China is the largest cement producer, accounting for about 55% of global
production. India is the world’s second-largest cement producer and consumer,
accounting for over eight per cent of the global installed capacity which is
only expected to grow.
The cement
industry is one of the world’s most energy intensive industries. The sector
contributes about 8% of the global anthropogenic CO2 emission, and
about 60-62% of the greenhouse gas (GHG) emissions are attributed to ‘process
emission’ that happens during clinker manufacturing.
Today’s
need to study the scope of improvements in cement manufacturing process &
technology, The
market offers a wide variety of alternative solutions; besides, this note
provides reviews of opportunities to improve energy efficiency in a cement
plant. However, the technology is constantly developing, so the available
alternatives may change in a upcoming years.
Power Consumption of Cement Manufacturing Units/Plants
The cement industry is high-power consumption industry, power
consumption in the cement grinding process (only grinding excluding
clinkerisation) takes a large percentage in the whole production, electric
power consumption is about 50%-70% of the total power consumption.
With more and more strict Energy
conservation and environmental protection policy published by govt., excess
production capacity, and higher market competition, energy conservation in
cement grinding plant is the main key for Cement Manufacturing to achieve the
purpose of reducing power consumption. Fuel and electricity are the largest
variable cost of production at cement plants. Variable costs are typically
about 50% of overall operating costs, so energy cost is usually the single
largest production cost, besides raw materials. Labor cost is relatively a
small part in the Cement
Manufacturing Plants.
Most of the energy is used in drives of the equipment, a lot of power is consumed in the processes of Raw material crushing, burning of raw material to make clinker, materials transport, cement grinding & cement transport. The cement industry thermal energy (natural gas consumption) is used in the process of heating of the raw meal (about 90% of total gas consumption), which involves clinker production in large kilns. In the most cases natural gas is used as a fuel in place of coal, Easier delivery, heat control are the main advantages of natural gas, there are other fuels can be used in cement rotary kiln, such as biofuels, the only problem is that it might cause pollution with unwanted gas created, or it is not sustainable for a continuous production.
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At present scenario, the cement
grinding system, the major cement grinding equipment includes loop flow ball
mill, roller press, ball mill semi-finishing system, and vertical mill system
(VRM), in which ball mill and vertical mill are 2 main cement grinding systems
in Cement Manufacturing, however all kinds of cement grinding plants have their
own advantages and disadvantages, The innovation and technological upgradation
in progress are constantly happening year to year, and the cement grinding
technology is also developing towards high efficiency and intelligence and
moving to artificial intelligence system.
Some highlights of Cement Manufacturing Units/Plants (in Indian
perspective
Approximate power consuption in cement plant (as per benchmark,CII-2021)
Cost of Production per Ton of cement:
Average electricity consumption for
Production of per ton of cement:
Improvement in usage of green power for
production of cement:
Targets to reduce the emission of CO2
in cement production:
Power Consumption of Cement Manufacturing Plant at Present
At present, the average level of unit energy consumption of Cement
Manufacturing Plants (cement grinding only, except clinkerisation) is at 33
kWh, in some Cement Manufacturing Plants, it could be 40 kWh that is higher than the average number, due to
technology improvement, upgradation of equipment, and new type abrasion
materials, the Cement Manufacturing Plant could reduce the unit energy
consumption of the grinding process to 18.8 kWh per ton of cement. For example,
the power consumption of “Dalmia Cement – Ariyalur” grinding has been reduced
to 22.3 kwh per ton, which is big progress has been made. It could save almost
1/3 of the average electricity consumption.
Power
Consuption For Cement grinding (Benchmark, CII-India 2021):
·
Grinding Power: 18.8 kwh/hr (for PPC)
·
Packing Power :0.65 kwh/hr,
·
Emission of CO2: 468 Kg/MT of Cement
For complete cement plant:
·
Specific power consumption per
ton of cement: International & national benchmark (56.14 kwh/ton, 56.00 kwh/ton)
·
Thermal power consumption per
ton of cement: International & national benchmark (660 kcal/kg, 676 kcal/kg of
clinker), (Best in india - Kotputli Cement Works Unit of ultra tech- 677 kcal/kg of
clinker.)
Upto clinkerisation:
·
Specific
electrical energy consuptin upto clinkerisation: International & national
benchmark (42
kwh/ton, 42.5 kwh/ton)
The followings benchmarks have been set by CII,
India for Cement Manufacturing plant and every plant of india is trying to
achieve the same step by step.
There are so may researcher groups are working on different cement
grinding methods and processes, it has made in-depth research and comparison on
technical requirements. It is said that the semi-final grinding process
can effectively solve the problem of the current combined grinding phenomenon,
and further improve grinding efficiency by using a roller press system with
ball mill grinding with high efficiency.
Thermal Energy Consumption in Cement Plant at A Glance:
The production process in cement plants is typically energy-intensive
and it requires a large amount of resources. A typical well-equipped plant
consumes about 3-4 GJ of energy to produce one ton of cement, the benchmark has
been set in India by CII (FY2021) is 476 kcal/kg of cement ie 2.83 GJ of
energy.
Improvement in Cement Grinding Process for productive cement quality:
- Control of the proportion of finished products
produced by the roller press system is the most appropriate. The specific
surface area is more than the average, the residual sieve residue of 45um
is nil. The cement capacity performance is the best at this time.
- Control mining powder quality, blending raw
materials, types and ratio.
- It is suggested that the cement production
line includes the compatibility test of cement and concrete
superplasticizer, and compare the correlation between cement composition,
ratio table, particle distribution and cement performance.
- Usage of artificial intelligence in cement
grinding process is very beneficial to reduce the electric power consumption
and higher quality of cement.
- Some researchers’ studies suggest that
capturing the carbon dioxide emissions before it enters to the atmosphere
and storing it away through reverse calcination is the most effective method
to de-carbonise the cement industry, reverse calcination could sequester
up to 5% of cement’s emissions at present, it could be extended to 30%
with the upgradation & improvement in technology. This process can be
further enhanced by employing green energy instead of conventional fossil
fuels to perform the process of calcination, noted the RBI.
- Cement Ball Mill Control System will help to increase
the productivity
a.
Control the fineness of raw material. The fineness of feed material is
48% ~ 52%, and that of outlet material is 32% ~ 35%.
b. Flowing Rate
Control. The flow rate of materials in the ball mill controlled, & the
partition in the ball mill is forced to pass through the compartment; the
discharge grate plate ventilation area is adjusted to select the use proper
scheme, and the hollow part of the activation ring is blocked to adjust the
material flow rate.
c. Semi-final grinding
needs very fine management to achieve the best results, from the host
selection, admixture, clinker, parameter determination, adjustment, control
tools, and other continuous research and performance-based adjustment.
Commitment of Various Cement plants in India
· Mahendra Singhi, who is the managing director
and chief executive officer of Dalmia Cement (Bharat) and the former president
of the Cement Manufacturers Association, emphasised that the Indian cement
sector is “the most energy and carbon-efficient globally” (when compared to
cement sectors in other countries) and has the “lowest carbon footprints on
account of early and voluntary actions from within the sector.”
“Despite
price sensitivity, we are the lowest carbon footprints producer globally. In my
view, it is the only way forward. Our early actions have made the sector ready
for bigger and deeper changes,” he said.
Asked
if a government regulation will push the cement industry to take giant strides
on the issue, Singhi emphasised that the “regulations on energy and
sustainability are already advancing.”
“For
example, SEBI has introduced the BRSR (Business Responsibility and
Sustainability Reporting) disclosures for top-1,000 companies in India. At the
same time, regulations may not be needed in a system where the industry itself
is proactive and taking self-motivated actions and targets,” he said.
Talking
about his own company, Singhi said they are committed to becoming net-zero.
“Dalmia Cement was the first cement group to commit to becoming carbon negative
on account of a circular economy, energy efficiency, non-fossil power
generation, electric mobility, use of green hydrogen, sustainable biomass use
as a fuel and carbon capture and utilisation,” he said while adding that they
demonstrated that decarbonisation of the industry makes business sense. In
2018, Dalmia cement announced the target of becoming carbon negative by 2040.
·
In 2021, another major cement player in India, ACC
Limited, announced 2030 carbon emission reduction targets committing to reduce
its CO2 intensity in cement operations from “511 kg in 2018 to 409 kg CO2 per
ton of cementitious material by 2030.” It signed the “Business Ambition for
1.5°C pledge and joined the Race to Zero campaign of the United Nations
Framework Convention on Climate Change.”
·
According to the RBI, India’s domestic cement industry has made
“remarkable progress in reducing CO2 emission levels by about 36 per cent from
1.12t/t to 0.719t/t of cement produced between 1996 and 2017.” To further
reduce it by half and “achieve the target of 0.35t CO2/t of cement by 2050, the
cement industry requires an investment of $29 billion to $50 billion,” it
notes.
References:
1. https://qz.com/
2. https://www.statista.com
3. Systematicx institutional research
4. CII, India
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