Yet to catch up
Environmental protection norms that have been revised and updated since 2014 are considered not too stringent going by global benchmarks. But the Indian industry and authorities are still in the process of finding a common ground.
The Ministry of Environment, Forest & Climate Change (MoEF&CC) has notified the new pollution norms for the Indian cement industry, which is the second largest producer in the world, in May 2016, with the primary aim of minimising pollution, in line with the country's intent/commitments made at CoP21 at Paris last year. The deadline for which was set at March 31, 2017.
It may be recalled that India's Paris commitments include reduction of the emissions intensity of its GDP by 33 to 35 per cent by 2030, from 2005 level; achieving about 40 per cent cumulative electric power installed capacity from non-fossil fuel based energy resources by 2030, and introduction of new, more efficient and cleaner technologies in thermal power generation.
The new pollution limits, after consultations with the industry and regulators, were notified on May 9-10, 2016, with a deadline to comply by March 31, 2017. The new norms have made particulate matter (PM) emissions stringent by bringing them from 50-150 milligrams per cubic metre (mg/Nm3) to 30 mg/Nm3. This limit depends upon the age and location of the plant.
The new norms relaxed the emission limit of sulphur dioxide and nitrogen oxide, one of the two key polluting gases released from industries. The limit of sulphur dioxide emitted from a cement plant was increased from 100 mg/Nm3 to 100-1,000mg/Nm3. This limit depends on sulphur content in limestone, a raw material for making cement. The limit for nitrogen oxide was relaxed from 600 to 800 mg/Nm3 to 600-1,000 mg/Nm3.
'This should come as a surprise because China, which is the largest producer of cement, has set the limit for the former to 200 mg/Nm3 and for the latter to 400-800 mg/Nm3,' say Kanika Bahel, Sanjeev Kumar Kanchan of Centre for Science and Environment (CSE).
Sources of pollution
The cement industry is one of the major air polluting industries due to generation of dust in various processes. There are three categories of dust emission in the industry - points of emissions like raw mill, kiln, clinker cooler, cement mill and coal mill; fugitive emission sources like transfer of raw materials, intermediates and final products and during their loading/ unloading; and kiln is the primary source of dust emissions.
The dust emission can be controlled by providing adequate pollution control equipment - cyclone, ESP, bag-filters, etc., based on size of dust particles, flue gas characteristics, techno - economic feasibility and collection efficiency.
Gaseous pollutants from the kiln are oxides of N (NOx) and SO2. Ammonia is injected into the flue gas in the high temperature zone at exit of the kiln where NOx is reduced to N2 in the presence of O2. Hydrated lime Ca (OH) 2 is injected into the flue gas to arrest SO2.
Unlike in power plants, water is not a major pollutant in cement plants. Only the cooling tower blow-down associated with the gas conditioning tower (GCT) is a source of waste water generation, though not a major water pollutant.
Operation of heavy duty machines like crushers, tube mills, ball mills, fans, coolers, etc. in cement process generates noise. Noise level depends mainly upon nature, size and capacity of machines, running speed and feed material. The noise level generally varies from 70 - 118 dB.
Principally cement plants use vibration damping pads, isolating vibrating parts to reduce noise pollution, and by enclosing the source and insulating it. Personal noise protectors like, ear plugs and ear muffs are used by those working in or visiting the plants.
For the first time, environment protection rules were introduced in early 1980s, through stringent dust emission regulations, where the emission standards were 250 mg/Nm3. During this period, most of the cement plants adopted ESP for all applications.
Subsequently, when the emission standards were tightened to 150 mg/Nm3, cement plants have upgraded the ESP with modern controllers, additional fields and change of electrodes. When dust emission standards have reduced to 50 mg/Nm3, cement kilns have shifted to reverse air baghouses with fibre glass bags and other applications like coal mill, cement mill, raw mill etc., shifted to low temperature bags like polyester/acrylic bags with or without antistatic treatment. However, the clinker cooler and captive plants continued with ESP technology.
In 2014, first time in India, gaseous emission standards (SO2, NOx, VOC, Mercury, NH3, heavy metals, dioxins and furans) for cement kilns and simultaneously dust emissions standards reduced to 30mg/Nm3 instead of 50 mg/Nm3, which are on par with the global best practices. Apart from the emission standards, CPCB issued a direction on February 5, 2014 about the online reporting of emissions (both Stack and ambient air) and effluents from 17 categories of industries. Further, CPCB released guidelines for continuous emission monitoring system during July 2017.
The notification calls for online reporting of emissions from all process stacks and ambient air quality stations to SPCB and CPCB on 24x7 basis and stringent reporting and compliance standard. In 2015, captive power plant (CPPs) emission reduction standard (Dust, SOx, NOx and Mercury) were introduced with varied emissions based on the vintage of the plant and also size of the plant.
Compliance timelines in both the cases, i.e., cement plants, March 31, 2017 and for CPPs up to December 7, 2017. 'In both the cases, industry faced many technical as well as financial challenges to complete these projects. Based on the industry request, the Cement plants have been given time line extension up to August 31, 2018 and for the power plants, time line extension is not yet finalised,' says KN Rao, Director û Energy, Environment & Sustainability, ACC Limited.
Various types of pollution control equipment are intensively used in the cement industry to minimise dust, nuisance in the plant area so as to maintain dust free atmosphere and to maintain the dust emission level within acceptable limits. Cement plant machinery work under negative pressure to prevent dust from escaping into the atmosphere. The common pollution control equipment used in cement plants include: electrostatic precipitator (ESP), dust-bag filters, gravel-bed filters and glass bag-house.
Monitoring and reporting
The monitoring and reporting protocol is also a major challenge in terms of technology option. As per the standard, the emissions are measured on a 15 minute average and non-compliance alerts are given to the companies. By design, emission from ESP varies with the process conditions and also emissions goes up while cleaning system of the electrodes takes place, especially in the outlet field. 'This becomes a big challenge when complying with the 15 minute duration constant emission from any ESP. Global compliance standards takes one day average or 3-day emissions average or 30 days rolling average to issue compliance alert and also to action of non-compliance. Indian standard on monitoring and reporting protocol is the toughest standard at this moment,' says Rao.
The reporting issues posed biggest challenge for the technology selection for the control equipment. From early 1980s, there is a rapid advancement in terms of fabric filtration technology and currently newer fabrics and membranes have been developed to reduce the emissions to below 5 mg/Nm3 with a lower pressure drop and guaranteed longer life of up to 6 to 8 years. Apart from dust, the current advanced filter media is capable of reducing heavy metals, dioxins, furans and mercury.
MoEF&CC has issued notification on revised emission norms to cement plants on August 25, 2014 against various parameters such as PM, SO2 & NOx emissions with varied compliance timelines for various parameters from January 1, 2016 to June 1, 2016.
Final compliance timelines were further extended August 31, 2018. (Please see the emission limits for various parameters in the accompanying article by KN Rao).
Environmental NGO, CSE, is decrying dilution of the latest norms drawing parallels with that in China. Last year, the Department of Industrial Policy and Promotion (DIPP) of the Centre has recommended to MoEF&CC to relax the deadline for compliance of environment emission standards by cement units by two years.
China, which is the largest producer of cement, has set the limit for sulphur dioxide to 200 milligrams per cubic metre (mg/Nm3). India's new norms, on the other hand, stipulate the emission limit for sulphur dioxide from 100-1,000 mg/Nm3.
Countries like South Africa, Australia, Germany and many other European countries have stipulated the emission limits for sulphur dioxide as low as 50 mg/Nm3. Similarly, countries like Colombia, Germany and other European countries have nitrogen oxides emission limit as low as are 200 mg/Nm3. Besides, many countries have stipulated limits for mercury, which India is yet to do, CSE says.
Calling these latest norms as far more relaxed compared to those stipulated in other countries, CSE said the industry 'should prepare a pragmatic action plan and implement it in a time-bound manner with proper consultation and approval from the ministry.'
In January 2018, Cement manufacturers breathed a sigh of relief after the Supreme Court of India lifted its ban on the use of petroleum coke in the cement and limestone industries. The order stated that 'pet coke should be utilised only in industries where sulphur is absorbed in the manufacturing process, for example, [in the] cement industry, [and] gasification plants.' The ban on pet coke first came into place in October 2017 in an attempt to address Delhi's severe air pollution.
SO2: Sulphur dioxide
NOX: Oxides of Nitrogen
HCl: Hydrogen Chloride
HF: Hydrogen Flouride
TOC: Total Organic Carbon
- B.S. SRINIVASALU REDDY