Practical Considerations in the Implementation of Emissions

Reduction Solutions at Eskom’s Coal Fired Power Plant

Presented by:

Ebrahim M Patel Senior Consultant – Air Pollution Control

Eskom – Group Technology Division

Date: 06 November 2012

4th EU-SA Clean Coal Technologies Working Group Meeting Emperor’s Palace, Kempton Park, RSA

Hosted by: Department of Energy (RSA) in association with SANEDI and the European Commission

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Introduction

• Emission standards for coal combustion have been introduced and adopted in many countries. These are usually expressed in terms of a maximum concentration of pollutant in the flue gas or a maximum quantity of pollutant per unit energy input/output.

• Internationally emission legislation has recently moved towards more flexible mechanisms such as cap and trading systems. Legislation is also becoming more localised, to deal with environmental problems where they are most needed.

• The link between air pollution and health has been established for well over a century. Pollution legislation such as emission standards is the only way of ensuring that air pollution is brought under control and that the detrimental effects on human health are minimised.

• In South Africa, air quality is dealt with by 2 mechanism:

• Ambient Air Quality (which has led to the declaration of priority areas), and

• Minimum Source Emission Standards.

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Air Pollution Control Regulations in South Africa

Why is air quality a risk to Eskom?

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Eskom is the Largest Emitter of SO2 and NOx in South Africa

PM10: NOx:

SO2:

Highveld Priority Area:

Source Contributions

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Air Quality Legislation

National Environmental Management:

Air Quality Act (No 39 of 2004)

Emission

Licence

Minimum

Emission

Standards

Ambient

Air Quality

Standards

Priority Area

Air Quality

Management Plan

Municipal

By-laws

Dust Fallout

Management

Regulations

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Ambient Air Quality Standards

Generally, while there are elevated

ambient concentrations, the frequency

of exceedances are within the

regulatory limits and are seasonal.

The concern in these areas are that as

industrial activity increases, the base

line changes thereby increasing the

potential for the number of

exceedances to be greater than the

regulatory limit.

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National Priority Areas

Vaal Triangle

Highveld

Waterberg

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Highveld Priority Area AQMP

• Eskom’s emission reduction plan for the Highveld Priority Area Air Quality Management Plan is synchronised with initiatives to achieve compliance with Minimum Emission Standards and with emission licences

• The emission reduction plan is legally binding (gazetted)

Compliance with Ambient Air Quality Standards: NOx and Particulates

• Ambient air quality dispersion modelling and monitoring show that Eskom’s activities do not cause non-compliance with ambient air quality standards for oxides of nitrogen (NOX) and particulate matter (PM)

• PM is the main pollutant of concern in South Africa, but Eskom’s activities make only a small concentration to total ambient levels

• Eskom is a major source of NOX on the Highveld, but modelling and monitoring show that there is compliance with ambient NOX limits everywhere in Eskom’s area of influence

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Compliance with Ambient Air Quality Standards: SO2

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Areas of non-compliance,

predicted by dispersion model

Eskom has setup an ambient

monitoring station in Kriel in order

to confirm to prediction models.

Minimum Source Emission Standards – Coal Fired Power Plant

• In April 2010, Minimum Emission Standards were published in terms of the National Environmental Management: Air Quality Act. There are standards for ‘existing plant’ which come into effect in April 2015, and more stringent ‘new plant’ standards which come into effect in April 2020. Existing plants are to comply with new plant standards by 2020.

• A postponement of the compliance timeframes of not more than 5 years may be applied for according to the Minimum Emission Standards, and an exemption from the Standards may be applied for in terms of section 59 of the Air Quality Act.

• There must also be compliance with National Ambient Air Quality Standards. PM10 is the greatest air quality problem in South Africa, but, when operating at normal emission levels, power stations make only a small contribution to total ambient levels. Power stations are the major source of SO2 in the Mpumalanga Highveld, and a major source of NOX, although ambient levels are well below NOX limits.

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2015 ‘existing plant’ limit

(mg/Nm3 at 10% O2)

2020 ‘new plant’ limit

(mg/Nm3 at 10% O2)

Particulate matter PM 100 50

Sulphur dioxide SO2 3500 500

Oxides of nitrogen (NOx as NO2) 1100 750

Source Emissions Measurements

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What is the Purpose of a CEMS?

• Continuous Emissions Monitoring Systems - CEMS

• Control Equipment operation and maintenance monitoring – how is my process doing?

• Compliance Monitoring – CEMS reports are used as legal proof of compliance to legislation

• Emissions Accounting

• Public Perception

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What is a CEMS

• CEMS can consist of the following components:

• Analytical Monitoring system for gaseous pollutants

• Opacity/Particulate Monitoring System

• Flow Monitoring system

• Data Acquisition System

• Not all components need be included

• Outside the US it is common for the CEMS to only include the analytical monitoring system

• The selection, operation, calibration and maintenance of CEMS must done in a manner as to ensure the data accuracy, reliability and availability.

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Harmful Stack Emissions

• Incomplete combustion, type and complexity of combustible and other combustion related phenomena result in emission of gases which are harmful to the environment:

• CO - result of incomplete combustion - poisonous and combustible

• NOX - NO+NO2+NO3...etc - Poisonous and corrosive

• SO2 (SOX) - only generated if Sulphur is present in fuel, acid

• HC - unburned hydrocarbons resulting from incomplete combustion

• Heavy metals, Hg etc

• Particulate matter - depends upon fuel and combustion efficiency, amount of particulate emitted and is usually measured as a function of the opacity of the gas, can be specified as opacity (0-100% opaque) or particulate (mg/m3)

• Others such as ammonia are particular to the type of process and fuel, these are not common

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Diluent Correction and Wet vs. Dry Measurements

• Many CEMS systems require measurement of CO2 or O2 although neither is a pollutant

• These are used to correct the emissions to a standard condition of either O2 or CO2 content (example 6 or 15% respectively for coal fired plant)

• The raw data for the pollutant is corrected to compensate for the deviation between the O2 or CO2 content in the gas and the standard conditions of 6 or 15%.

• Correcting to Reference O2

• Stack conditions are hot and wet. Water is in vapor form. If it is extracted it will condense. Many systems remove the water so that it doesn’t damage the analyzers and so that it scrubs particulate out with it as well. Regulated emission levels are often stated on a dry basis.

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Co = Cm x [( 20.9 - O2ref)/( 20.9 - O2meas)]

Co = corrected emission level

Cm = measured emission level

International Normalization: O2 ref = 6 % Coal

RSA Normalization: O2 ref = 10 % Coal

Summary of CEMS

• “To measure is to know” – this is the first action to be done before any reduction options are conceptualized and provides the basis of knowing how much to reduce, when and where.

• How has Eskom quantified it’s emissions:

• Particulate concentration (mg/Nm3) – real time, on-line in-situ measurements.

• SO2 (ton) – calculated based on fuel consumption and fuel sulphur content.

• NOX (ton) – calculated based on NOX emissions factors following periodic tests.

• Way Forward:

• Migrate towards real time, on-line in-situ or extractive measurements for gaseous monitoring of O2, CO2, SO2 and NOX.

• Currently have 1 monitor per station (i.e. only one stack or flue) and gaining experience on the management of these systems.

• Plan to roll out CEMS to all stations by the end of 2014.

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State of Eskom’s Current Fleet & Implications

• In terms of emissions abatement control on Eskom’s fleet, the focus to date has primarily been on particulate control.

• With the advent of the minimum emissions standards, focus is now moving toward De-SOX and De-NOX abatement.

• Kusile (new build) will be Eskom’s first coal fired power station to employ a wet flue gas desulphurisation (FGD).

Medupi (new build) will be retrofitted with a wet-FGD during the first general overhaul (GO) cycle.

• Both Medupi and Kusile (new build) will comply with the NOX limits for new plant from inception (low NOX burners plus over-fire air).

• Feasibility studies have commenced for the upgrade of existing power stations in order for them to comply with the min. emissions standards.

• Particulate upgrade strategy to be completed by end of 2012.

• NOX and SOX upgrade strategy to be completed by end of 2013 and 2014 respectively.

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Compliance Status

Station type

Station sub-

type

Station

name

Current compliance with existing plant

standards

Current compliance with new plant

standards

PM NOX SO2 PM NOX SO2

Coal-fired

power

stations

New Build

Kusile Y Y Y Y Y Y

Medupi Y Y Y Y Y

No but will

comply 6

years after

commissionin

g

Majuba Y N Y Y N N

Kendal Y Y Y N Y N

Matimba Y Y Y N Y N

Lethabo Y Y Y N N N

Tutuka N N Y N N N

Duvha U1-3 Y Y Y Y N N

Duvha U4-6 Y Y Y N N N

Matla N N Y N N N

Kriel N N Y N N N

Arnot Y Y Y Y N N

Hendrina Y Y Y Y N N

Return-to-

service

stations

Grootvlei N Y Y N N N

Camden Y Y Y N N N

Komati Y N Y N N N

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Station Remnant Life

Station name

Average

remaining life (50-

year life)

Decommissioning date: 50

year life; RTS current plan

Kusile 50+

Medupi 50+

Majuba 36 2046-2051

Kendal 29 2048-2053

Matimba 27 2047-2051

Lethabo 25 2045-2050

Tutuka 25 2045-2050

Duvha 20 2040-2044

Matla 19 2039-2043

Kriel 16 2036-2039

Arnot 11 2031-2039

Hendrina 11 2030-2036

Grootvlei 10 2021-2023

Camden 6 2025-2028

Komati 1 2024-2028

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Stations in red have passed their mid-life, while stations in yellow are currently in their mid-life.

Life extension assessments for 60 year life still to be conducted on all stations except for the Return-to-Service Stations:

Grootvlei, Camden and Komati.

Particulate Emissions

• Since particulate emissions have been regulated for some time, Eskom has been aspiring to lowering the impacts over the years.

• Historically, particulate emissions limits have been based on the abatement technology employed at the specific power plant and revised once the plant has been upgraded or retrofitted with better abatement control equipment.

• These included:

• Upgrading the electrostatic precipitators (ESPs),

• Addition of flue gas conditioning (SO3), and

• Retrofitting of the ESPs with Fabric Filter Plants (FFPs).

• With the minimum source emissions standards requiring an eventual maximum emissions of 50 mg/Nm3 for all plant, a number of stations will require another phase of upgrades.

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Eskom’s Current Fleet – Particulate Control Plant History

TOTAL INCREASE IN COAL BURN RATE 15.5%

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Eskom’s Current Fleet – Particulate Control Plant History

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Implications for Particulate Reduction

• Minimum Source Emissions Limits requires that plant be upgraded to comply with either Best Available Technology (BAT) and/or Maximum Achievable Control Technology (MACT).

• The following stations will need major particulate abatements upgrades to comply with the 50 mg/Nm3 limit: Tutuka, Grootvlei (2-4), Kriel, Matla, followed by Lethabo, Duvha (4-6), Matimba & Kendal (a total of 42 units).

• ESP upgrades are no longer an options due to the low grade coal being used. Therefore, FFP retrofits (including an ID fan and dust handling plant upgrade) become the most viable option requiring on average 120 days per unit for the retrofit.

• Challenges: Space limitation on terrace limits a “green field” type retrofit strategy, coal quality and consistency requires greater design margins, outage access prior to Medupi, Kusile and Ingula being fully commissioned, increased CAPEX and OPEX, increased CO2 due to reduce efficiency, execute-ability of these projects in such a short period and localisation imperatives, and used bag disposal.

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0

1

2

3

4

5

6

7

8

9No. of Units Out per year for FFP Retrofit Program

NOX Emissions

• NOX generated is a function of the boiler thermal process and the boiler design.

• None of Eskom’s current plant have been designed with NOX reduction in mind.

• Currently only Matimba and Kendal will be able to comply with the 750 mg/Nm3 NOX limit. These are inherently low NOX generating plant due to their corner fired design.

• NOX reduction concept studies commenced in June 2012 looking at the following options: Low NOX Burners (LNBs), LNBs + Over Fire Air (OFA), Selective Catalytic Reduction (SCR) and Selective Non Catalytic Reduction (SNCR).

• Study currently focusing on prioritizing highest emitting stations Tutuka, Majuba, Kriel and Matla followed by Duvha, Lethabo, Arnot, Hendrina, Camden, Komati and Grootvlei.

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Implications for NOX Reduction

• Requires at least 75 units to be done with outage duration ranging from 85 to 150 days depending on the abatement technology to be used (assumed LNB + OFA as default option).

• Unburnt carbon in ash increases by between 2 and 5% resulting in an estimated 950 000 ton of additional coal that will be required … plus increased CO2 as a result.

• Boiler combustion process risks (flame/temperature redistribution, change in combustion and flow profile).

• SCR/SNCR option have the to deal with catalyst and ammonia requirements .

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SO2 Emissions

• SO2 generated is a function of the sulphur content in the fuel.

• None of Eskom’s current plant have been designed with SO2 reduction in mind and none of these plants will be able to comply with the 500 mg/Nm3 limit.

• The low grade coal that Eskom generally utilizes has inherently low sulphur (typically between 0.8 to 1.2 %) … this is already a form of SO2 mitigation. Low sulphur content yields higher ash resistivity which makes it more difficult to collet the ash particles in the ESPs.

• Kusile will be Eskom’s first FGD with Medupi being retrofitted during it’s first GO cycle.

Medupi has been built as “FGD ready”. Rotated the chimney 180o, lined the chimney flues for operating in both a un-saturated and saturated environment, left space on the terrace for the FGD island and made provision in the balance of plant for the supporting systems such as water, sorbent, waste etc.

• SO2 reduction concept studies to commence in 2013 and to consider a range of options from coal beneficiation to post-combustion control technologies (wet, semi-dry and dry) including some emerging mutli-pollutant control technologies such as SNOX, Re-ACT etc.

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Implications for SO2 Reduction

• Requires 64 units across all stations except for Camden, Grootvlei and Komati.

• Assumed In-duct (dry) at Arnot, Hendrina & Kriel, Semi-dry at Duvha, Lethabo & Matla and Wet at Kendal, Majuba, Matimba & Tutuka.

• Anticipated increase in annual operating costs R 4 400 M due to increased water, sorbent, energy consumption and waste disposal activities. Typical Consumptions (for a 600 MW unit per annum): Sorbent (lime/limestone): 70 000 to 95 000 tons (plus increased CO2 generated), Water: 840 000 to 1 300 000 m3 Power: 25 000 to 50 000 MWh (plus increased CO2 generated) O&M: 6 to 8 R/kW Gypsum from wet-FGD: 180 000 to 200 000 tons

• Water and Sorbent availability remain a huge risk and waste management increases the environmental footprint of the station.

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Challenges Facing Eskom in Complying with Emissions Legislative Requirements

• Coal quality consistency and variation in quality is currently playing a significant role in the overall reliability and availability of the power plant. This is also influencing the performance of the particulate abatement control plant.

• The current capacity constraints has led to a maintenance back-log and one can only expect improvements once the new build is completed. This could continue if the necessary decisions under IRP2010 are not taken timeously.

• The requirement for existing plant to comply with new plant stations implies that almost every power plant will need to be upgraded for either or all of the listed pollutants (PM, SO2 & NOX). The execution plan should as far as reasonably possible consider undertaking these project concurrently to minimise the outage impact (particularly relevant for PM and NOX)

• A number of stations have already passed their half-life and the socio-techno-economic justification at these stations need serious review in light of what country can afford. Both the CAPEX and OPEX requirements as a result of these retrofits will result in significant tariff increases for the medium term.

• Clarity is required on whether emissions limits could be made even more stringent during the next review in 2015?

• Water and Sorbent availability is off particular concern for post combustion abatement technologies. Additional water allocations to the Highveld are only expected post 2020 and current indication for suitable local sorbent quality suggests enough quantity for between 4 to 6 stations (including the new builds).

• The 2020 compliance time-frames put further pressure on the existing capacity constraints and also does not allow RSA to leverage fully the skills development and localisations initiatives.

• Compliance with these requirements will increase Eskom’s already significant CO2 footprint (Climate Change Impact).

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Conclusion

• Compliance with the requirements is not impossible. However, the socio-economic implications are significant for a developing country.

• The basis for motivating any emissions reduction should be based on human health impact of ambient air quality as enshrined in the constitution.

• Should existing plant be required to comply with new plant standards?

• Based on the above, we should be prioritising our highest impact stations first (compliance with existing plant standards):

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PM NOX SO2

Tutuka Yes Yes

Majuba Yes

Kriel Yes Yes

Matla Yes Yes

Grootvlei Yes

Medupi Yes, new plant

Future Work

• Improvements in air quality control could be supported by upstream developments in the areas of coal mining (and mine planning) and coal beneficiation (and coal quality monitoring).

• The pathway and final impact on water infrastructure / consumption; sorbent mining / transport infrastructure and waste management must be interrogated.

• Mutli-pollutant control technologies.

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Acknowledgements

The information contained in this presentation is obtained from a number of sources and acknowledgements is hereby given. The most significant of these sources are:

• Trends in Emissions Standards by Dr. Lesley L Sloss, IEA Clean Coal Centre

• Supporting South African Environmental Information supplied by Dr. Kristy Langerman, Eskom Environmental Management

• IFC’s EH&S Guideline for Thermal Power Plants

• European Large Combustion Plant Directive (LCPD, 2001/80/EC)

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Thank you