The new environmental norms which the power sector has to adhere to come with their own set of technological challenges.
For the first time ever, schools have been shut in the first week of November 2016 in New Delhi and citizens are rushing to buy air purifiers as sensors show alarming levels of air toxicity. Why has the situation come to such a pass?
The heavy concentration of particulate matter is greatly affected by meteorological conditions. In winters, cool air causes ‘inversions’ that make the air stagnant and trap pollution close to the ground. Air flow patterns from Afghanistan and Pakistan pick up emissions as they move over the densely urbanised regions of Punjab and Haryana where farmers burn straw in their fields and pull this pollution into Delhi.
Pre-monsoon dust storms also contribute to air pollution in the region. These are some of the opinions expressed by environmentalists. Ref. Figure 1
The role played by thermal power plants is significant in worsening air quality. The Ministry of Environment, Forest & Climate Change (MoEF & CC) announced the revised standards for controlling pollution in December 2015, considering the deterioration of ambient air quality. The proposed standards are strict, but can be achieved if the compliance plan is executed correctly. The revised standards, which are quite comparable with international standards, aim to cut emissions of particulate matter (PM), sulphur dioxide (SO2), oxides of nitrogen (NOx), and mercury. In addition, the new norms also require power plants to sharply curtail the use of water.
In December 2015, MoEF & CC announced standards for coal-based thermal power plants, which are given below. Ref. Table 1
There are commercial implications of executing the change. The most important one being of finance for the investment required and cost recovery through tariff. The time lines issued by the ministry are tight, but achievable.
In case any additional time is required for implementation of the change, this permission may be granted on a case-to-case basis. Plants under construction need to change the design and plans to meet the new norms from 1st January 2017, which would be a challenge.
Investments in plants/units that have exceeded their design life of 25 years must be made carefully, considering their efficiency and availability, post revamp. A majority of such plants will have to be shut down. Basic up-gradation targeting mainly PM control may, however, suffice in the interim. Plants with good operating performance, low cost of generation and recent repairs & maintenance that would have extended remaining life may be allowed to invest so that they can meet the new standards.
Particulate matter (PM)
Units commissioned between 1990 and 2008 may need to upgrade the electrostatic precipitator (ESP) to meet the PM norms of 100 and 50 mg/Nm3.
In some cases, it may involve adding fields in series or parallel or increasing the height of the ESP. The units installed after 2008 are required to meet PM norms of 50 mg/Nm3. Therefore, a basic performance revamp may suffice for these units. However, some units are required to meet 100-150 mg/Nm3 and others are poorly performing — these units may require huge investment.
Power plants under construction should be able to meet the 30 mg/Nm3 PM standard with a combination of ESP and FGD (flue gas desulphurisation) In fact, an integrated design would mean that the ESP size can be made smaller than a standalone one for meeting the norm.
Sulphur dioxide (SO2)
Units of size less than 500 MW installed between 1990 and 2016 need to meet the SOx norm of 600 mg/Nm3. These units may choose options such as partial FGD or sorbent injection.
Units of size 500 MW and more, installed between 1990 and 2016, have to install limestone-based wet FGD or lime-based dry FGD, depending on raw material and water availability. FGD is a mature technology for controlling SOx. It is used in many countries and has been shown to be effective for a wide range of coal qualities and operating conditions. China has installed FGD in over 91.4 per cent of its fleet in recent years. Upcoming units can meet the SOx standard by installing FGD.
Oxides of nitrogen (NOx)
Minimal measures are needed to meet emissions of less than 600 mg/Nm3. Some units are already meeting these levels. The units installed after 2003 have to reduce emissions to 300 mg/Nm3. Manufacturers, including BHEL, have already been supplying boilers that meet these emissions. Those plants whose emissions exceed the norms will need to choose from several options including burner modification, over fire air supply (OFA) etc., depending on the base level of emissions and technical constraints.
Upcoming units need to meet the NOx emissions of 100 mg/Nm3 SCR (Selective Catalyst Reduction) and SNCR (Selective Non-Catalyst Reduction) technologies, which have been used globally to cut NOx to these levels. Some industry players, however, feel that the technology’s effectiveness needs to be established for Indian coal (high ash, chemical composition and physical characteristics). NTPC will run five pilot programmes to assess the technology. Suppliers are confident that the technology will work with possibly minor tweaks.
The coal-based power sector is in the midst of a major transition across the world. China, for instance, has decided not to build new coal-fired plants after 2030. India, on its part, has put in place tighter environmental standards and hiked its coal cess by eight times within two years. Says Chandra Bhushan, Deputy Director-General of Centre For Science and Environment (CSE), New Delhi, “The world is faced by relatively newer challenges, including that of a changing climate — this means countries need to have flexible, nimble energy policies.”
In addition to the monitoring of individual parameters, the power plants will have CEMS(Continuous Emission Monitoring System). Developed countries such as the US, EU and Japan as well as a few emerging economies like Brazil and China have already adopted CEMS. The Central Pollution Control Board will be the authority that will drive the implementation.
Priyavrat Bhati of CSE adds, “Some basic requirements for successfully implementing CEMS — such as skilled laboratories and human power or comprehensive guidelines for device selection, etc., are still lacking in India.” This creates multiple implementation challenges which must be urgently resolved. While CEMS has been initiated as pilots in three states, fundamental issues are yet to be resolved. For instance, manufacturers express their concern over the unavailability of standards in India for getting themselves certified as accredited device manufacturers. It goes without saying that the changes are equally applicable to captive power plants irrespective of their capacity to generate power.
Table 1: Standards (in mg/Nm3)