Adopting Best Practices: Cement industry uses technology to improve energy efficiency

Cement industry uses technology to improve energy efficiency

The Indian cement industry is one of the most efficient in the world. Over the years, it has made efforts to reduce its carbon footprint by adopting the best available technologies and environmental practices. Gradually moving on to the goal of decarbonisation in order to lessen the impact on the environment, the cement industry is actively focusing on energy efficiency as well as renewable energy technologies.

Industry overview

India is the world’s second largest cement market, both in production and consumption. The installed cement manufacturing capacity stands at about 545 million tonnes (mt), accounting for 8 per cent of the global cement capacity. Of the total installed capacity, 98 per cent is with the private sector and 2 per cent with the public sector. The top 20 companies account for nearly 70 per cent of the total production. While housing and real estate sectors account for nearly 65 per cent of the total cement demand in the country, public infrastructure accounted for a 25 per cent share and industrial development for a 10 per cent share. High government spending on infrastructure and housing, and rising per capita incomes have been the key growth drivers of the cement industry.

PAT performance

The Bureau of Energy Efficiency’s (BEE) Perform, Achieve, Trade (PAT) Cycle I (2012-15) included 478 units (designated consumers or DCs) from eight energy-intensive sectors, including cement. The minimum annual energy consumption of each DC was 30,000 tonnes of oil equivalent (toe). About 85 cement plants in India were notified as DCs under PAT I.

As the PAT scheme progressed, the cement sector had 111 DCs till Cycle II (which began in 2016), with 14 in Cycle III (which began in 2017), one in Cycle IV, 12 in Cycle V and 37 in Cycle VI. Overall, a total of 175 DCs were included and provided individual targets for the reduction in specific energy consumption.

In PAT I, the cement sector (85 DCs) performed well and saved 1.48 mtoe of energy, that is, 17 per cent of all the energy saved and 4.34 mt of CO2 emissions per year. During Cycle II, 1.117 mtoe (from 111 DCs) of energy savings were targeted, but based on monitoring and verification, 99 DCs exceeded the target and saved 1.571 mtoe. The duration of PAT Cycle III was from 2017-18 to 2019-20, in which cement units achieved energy savings of 0.163 mtoe, as against a target of 0.094 mtoe.

BEE has rolled out six PAT cycles till March 31, 2020, with a total of 1,073 DCs, covering 13 sectors. It is projected that the total energy savings of about 26 mtoe, translating into avoidance of about 70 mt of CO2 by March 2023.

Technology options for improving energy efficiency

As per a report titled “Transitioning India’s steel and cement industries to low carbon pathways” by the International Climate Initiative, the cement industry has adopted several technologies over the past decade, driven by regulatory mechanisms under the PAT scheme. Notably, waste heat recovery (WHR) systems have been installed by cement  plants across the country, which have played a crucial role in reducing energy consumption. These plants use the waste heat from industrial manufacturing processes for generating steam, process heating and generating electricity. The waste heat is, therefore, reused, implying a circular use of heat. The Clean Development Mechanism (CDM) under the Kyoto Protocol has enabled the installation of WHR plants across cement plants. Although the cost of installation of these plants was very high, the CDM market-based mechanism made it feasible. Further, the high price of certificates of emission reduction (CERs) under the mechanism provided additional incentive for high emitting industries to undertake capital intensive investments, which would continue to reap benefits in the long run.

Another specific feature of the cement industry, as per the report, has been clinker factor reduction. Clinker is the key ingredient in cement and the amount of clinker used is directly proportional to the CO2 emissions generated in cement manufacturing due to both combustion of fuels and decomposition of limestone in the process. The lower the clinker to the cement ratio, the lower the emissions. This ratio can, and has, been reduced by partially substituting clinker with fly ash in the production process. Increase in fly ash consumption has been a positive towards reducing emissions.

Other best practices and technologies for energy efficiency under PAT include installation of vertical grinding mill, high recuperation efficiency hydraulic cooler, highly efficient screw compressor, high efficiency third-generation air separator, enhancement of the usage of alternative fuel and raw materials in the kiln, and increase in the number of stages of preheater.

Key initiatives

Some energy efficiency initiatives by key players in the cement segment are given below.

UltraTech Cement: The company has undertaken numerous initiatives to conserve energy such as optimisation of grinding media to reduce power consumption, replacement of low efficiency process fan impellers with high efficiency ones, retrofitting of old generation coolers to improve kiln heat rate, deployment of nonconventional and clean energy sources such as installation of solar heaters and solar lighting, installation of different variable speed drives and energy-efficient motors, introduction of the latest turbo blower technology wherever applicable, and operational optimisation of the pyro process and mills for the overall energy optimisation through automation. During 2019-20, the company has made an investment worth Rs 1.59 billion on equipment or various capital schemes for conserving the energy resources.

ACC Cement: ACC Cement has undertaken energy conservation and efficiency measures in its manufacturing operations as well as captive power plants. Some of them include productivity rate index improvement through computational fluid dynamics studies, implementation of projects identified as a part of the mandatory energy audits of all integrated plants, installation of high-level controllers for kiln and cement mill, installation of medium-voltage variable frequency drives and low-voltage variable frequency drives for process fans and replacement of conventional lights with LED light across all plants. Notably, during 2020, ACC Bargarh Cement Works was adjudged as an excellent energy-efficient unit by the Confederation of Indian Industries (CII) and ACC Wadi Cement Works was also amongst the shortlisted cement plants. In addition, the company’s Jamul plant achieved 4.5 star rating in the large-scale category of ENCON (Energy Conservation) Award 2020 in the CII eastern region.

Ambuja Cement: Ambuja Cement is also making continuous efforts to improve its energy efficiency. The company has been taking steps for conservation of energy such as optimisation of compressor power, replacement of water pump motors with high efficiency motors, improvement in separator efficiency by optimising the rotor speed and fan flow, installation of active filter, among others.

Challenges and the way forward

There are several technical, financial and regulatory barriers to the adoption of advanced technologies to improve electrical and thermal energy efficiency in the cement industry. Some of the technical barriers for preheaters and kilns include layout constraints, high moisture content in limestone and burnability index of the raw mix.

The key limitations to the installation of high-efficiency clinker coolers are the uncertainty regarding their benefits for retrofit installations and the additional shutdown time required for retrofits. Incremental costs for new installations and overall costs for retrofit installations also pose a big challenge.

In terms of technology, there are still a few challenges, such as capacity limitations of roller presses, where higher efficiencies could be achieved by using voltage regulator modules. Also, retrofitting costs to upgrade grinding technology or replace uniflow burners with advanced multi-channel burners are very high and have long payback periods, of 6-10 years (if only energy savings are considered). Many plants have installed the latest energy-efficient burners, which have reported reductions in NOx generation and primary air consumption as low as 3.5 per cent.

In terms of energy-efficiency improvements in process fans, a few technical challenges are associated with the layout of facilities where the ideal duct system cannot be accommodated. Moreover, higher investment and operating costs for the latest auxiliary equipment could be a deterrent.

Sharing of best practices with global players in the industry can help mitigate some of these technical challenges. Despite these issues, the cement industry has made commendable energy-efficiency efforts in the past and it must continue on this path of reducing energy consumption and increasing the use of alternative fuels, in order to meet its target of achieving 24 per cent reduction in emissions by 2050.