The article highlights the new emission standards and online reporting protocol for cement plants and captive power plants. It also covers the advancements in filtration technology to reduce dust, SOx, NOx, Mercury, Dioxins and Furans, heavy metals from the Kiln gases and also dust and SO2 from CPP.
Stringent dust emission regulations are introduced in early 1980s where the emission standards were 250mg/Nm3. During this period, most of the cement plants adopted electrostatic precipitators (ESP) for all applications. Subsequently, when the emission standards were reduced to 150mg/Nm3, Cement plants have upgraded the ESP with modern controllers, additional fields, 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 50mg/Nm3, which are on par with the global best practices. Apart from the emission standards, CPCB issued a direction on 5th February 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 24 X 7 basis and stringent reporting and compliance standard. In 2015, CPPs emission reduction standard (Dust, Sox, NOx & 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.
The monitoring reporting protocol also is 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 has been 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 1 day average or 3 day emissions average or 30 days rolling average to issue compliance alert and also to action of noncompliance. Indian standard on monitoring reporting protocol is the toughest standard at this moment.
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, Mercury removal.
Latest environmental regulations
Cement Plant: 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 extension is further extended August 31, 2018.
Filtration technologies adopted by cement
Indian cement industry is very progressive and is continuously adapting to the latest technologies to make the Cement Industry more efficient and green with less environment footprint. In the same spirit, Cement Industry is first one to adopt filtration technologies like Pulse Jet Bag House (PJBH), reverse air bag house and hybrid filters for controlling of dust emissions from stack.
Advent of new fabrics which can withstand higher temperatures and tough working conditions, controls and advance electrical systems provided the opportunity to reduce the dust emissions to very low levels. Cement Industry embraced these technologies that helped industry today in achieving consistent and lower stack emissions of 30 mg/Nm3.
To meet the online reporting requirements, cement plants have installed Continuous Emission Monitoring Systems (CEMS) and continuous ambient air quality monitoring stations (CAAQMS). Among various Industrial sectors, Cement Industry is the first one to move ahead with on line reporting of their dust emissions performance. This has demonstrated the willingness of Cement Industry to be more transparent in disclosure of their dust emissions performance.
Advancement in filtration technologies in fabric filters
There are several conditions like change in process/raw material, wrong selection of fabric, and other design issues, abrupt changes in process operational parameters, poor diagnosis including lack of automation, improper maintenance, operational incompetency etc. resulting in poor performance of bag filters.
To address these issues, various advancements took placed in fabric filter technology and details of these developments are as given below: