Minimization of capital and operational costs for DeNOx

technologies in new and existing combustion facilities

Francisco Rodríguez1, Enrique Tova

1, Miguel Delgado

1, Enrique Bosch

2, John W Sale

2

1

INERCO. PT Isla de la Cartuja, c/ Tomás Alba Edison, 2, 41092, Sevilla, Spain

2 INERCO ETech (In Partnership with GP Strategies). 25 Northpointe Parkway, Suite 100,

Amherst, NY 14228

INTRODUCTION

The coal power sector is being challenged by the current industrial and economic climate,

characterized by the increasingly stringent environmental legislation and the reduction of

natural gas price. Therefore, electric utilities are forced to install high-efficiency abatement

technologies to comply with pollutant emission limits while paying special attention to

profitability criteria. This economic concern is not only focused on the decision-making

process of undertaking retrofit actions in their facilities, but also on their day-to-day operation

to minimize current operating costs.

The regulation of nitrogen oxide (NOx), which is one of the most damaging environmental

pollutants, is becoming particularly severe worldwide. In order to meet the imposed emission

limits, the exclusive application of primary measures (combustion control), such as

combustion tuning, low-NOx burners and over fire air (OFA) systems, have proven to be

insufficient under most circumstances. Among the commercially available post-combustion

(secondary measures) NOx abatement systems, Selective Catalytic Reduction (SCR) systems

are the most appropriate and widely used technology to reach the high reduction efficiencies

required. However, the installation or use of conventional SCR solutions in existing

combustion facilities has technical and economic drawbacks.

First, the installation of a separate SCR system reactor is technically difficult in most existing

facilities due to the lack of available space to undertake such a significant retrofit action.

Besides, this solution might not be optimized from an economic viewpoint, as it leads to

extremely high investment costs that would seriously jeopardize the profitability of the

facility, bringing serious difficulties to amortizing the investment, especially in those power

plants with a short remaining lifetime. Also, it entails high annual operating costs and a loss

of efficiency that affects plant profitability.

Second, in those facilities where SCR systems are already installed, their significant

operating costs bring about a pressing need to optimize their performance through the

reduction of reagent consumption or the improvement of catalyst management. Considering

current power plant operating trends, characterized by frequent start-ups and shut-downs and

increasingly long part-load operating periods, the lack of flexibility shown by SCR systems

makes it even more difficult to justify the investment and operating costs required to achieve

the target NOx emissions limits.

Facing this complex scenario, characterized by the lack of technological alternatives to

conventional SCR systems, INERCO has developed a methodology and technical approach

based on the customizable combination of advanced primary and secondary measures for the

reliable and cost-effective minimization of NOx emissions in any operating scenario.

The integrated approach developed by INERCO relies on proprietary advanced regulation

capabilities which provide an optimized distribution of coal supply to the boiler. This

approach is enhanced by incorporating improved combustion control based on state-of-the-art

monitoring tools that have been developed and widely demonstrated by INERCO. As a

result, it is possible to achieve minimum NOx emissions compatible with combustion control

and process safety. Starting from a safe low NOx operating condition, the INERCO approach

also entails the tailor-made integration of proprietary DeNOx solutions with advanced

capabilities to achieve optimum results in large-sized boilers. Consequently, the INERCO

approach constitutes a cost-effective alternative to new SCR systems due to the considerable

savings in investments costs combined with an effective complementary solution to existing

SCR systems, as it is able to produce remarkable reductions in operating costs.

This paper is focused on the description of the novel technological solutions conceived by

INERCO and the depiction of the successful results attained in representative case studies.

Based on these results it was also possible to carry out an economic comparative assessment

between this approach and the use of conventional SCR technologies for new and existing

combustion facilities.

ADVANCED PRIMARY MEASURES FOR NOx MINIMIZATION

Management of the fuel supply to the boiler

An efficient operation in industrial combustion units depends greatly on the correct

distribution of fuel and air supplies to the combustion chamber. Heat rate, emissions (NOx,

CO, CO2, particles) and the appearance of collateral operating problems, such as corrosion,

slagging or carbon-in-ash, are strongly dependent on this distribution. Therefore, the

effectiveness of stricter combustion controls is based on the actual balancing of the

combustion process.

In order to achieve a balanced distribution of coal supply to the combustion chamber,

INERCO has developed ABACO-Coal dampers, either an automated or manual regulation

system that provides an effective regulation of pulverized coal flow in the ducts from mills to

burners (Figure 1). The application of this technology results in an enhanced control of coal

flow rates to each burner, which leads to the reduction of typical coal supply imbalances

between ducts belonging to the same mill from 20% - 30% to 5% - 10%.

In addition, optimized operating strategies to minimize NOx emissions are also based on

achieving maximum stratification of coal and air supplies to the boiler. However, the actual

applicability of these strategies is hampered by two main factors. First, the appearance of

operating problems, such as increased carbon-in-ash or efficiency losses. Second, the

impossibility of maintaining the most favorable coal and air distribution, due to necessary

maintenance actions on the milling systems, which leads to increased NOx emissions, carbon-

in-ash or furnace temperatures.

These limitations are overcome by the novel FLEXICOM-LNB technology, which enables

the adoption and steady maintenance of optimal in-furnace firing distribution for any

operating scenario (boiler load, milling system arrangement, fuel quality). This leads to the

minimization of NOx generation for all operating scenarios while avoiding the appearance of

the aforementioned collateral negative effects. Besides, it also keeps boilers from

unfavorable situations linked to unavoidable mill maintenance activities. The achievement of

these objectives is based on the retrofit of the coal distribution system with two advanced

regulation systems:

Substitution System – steady air and fuel supply irrespective of mills in service, which

avoids unwanted scenarios promoted by mill unavailability (“burner gaps”) that produce

increased NOx emissions and carbon-in-ash. This also allows the strict fulfillment of the

mill maintenance programs scheduled by the utility (Figure 2).

Figure 2: Conceptual scheme and image of the “Substitution” module

Figure 1: Automated ABACO-Coal dampers for coal balancing supply

Addition System – minimum NOx generation by the achievement of maximum fuel

stratification and coal residence time, without increasing mill production and, therefore,

without penalizing coal fineness, which favors the minimization of CO emissions and the

control of unburned carbon-in-ash (Figure 3).

The combination of both systems avoids shifting the combustion process to the upper furnace

region, as happens for high performance over-fire air (OFA) solutions, resulting in a more

effective way to control furnace temperatures (flue gas, radiant superheater (SH) surface, live

steam, etc.) and desuperheater spray flow rates. In addition, they enable an enhanced

grinding potential for the mills and an increased pulverized coal residence time, which favor

the minimization of CO emissions and the control of unburned carbon-in-ash. Consequently,

besides the minimization of NOx emissions for all operating scenarios, the beneficial features

of FLEXICOM-LNB lead to the optimization of boiler efficiency and heat rate and the

avoidance of collateral operating problems (carbon-in-ash, corrosion, etc.).

This approach also provides increased boiler and milling system availability and optimizes

operating flexibility, since FLEXICOM-LNB fits any boiler load or milling system

arrangement. This enables the use of lower quality coals and co-firing of alternative fuels. In

addition, maintenance programs used by the utility are not affected by operating constraints.

Consequently, the optimized operating scenarios promoted by this technology can be a long-

term operating solution.

Finally, these technologies are fully-complementary with other conventional primary

measures for NOx reduction also applied by INERCO, such as over-fire air (OFA), burner or

windbox upgrades, fuel reburning or mill classifier retrofits (Figure 4). In addition, the

resulting operating scenarios promote an increased furnace region for reburning secondary

fuels and favorable conditions for the injection of ammonia or urea in the high-temperature

furnace areas.

Figure 3: Conceptual scheme and image of the “Addition” module

Advanced monitoring of the combustion process

The possibility of taking full advantage of the FLEXICOM-LNB technology, ABACO-coal

dampers and any other conventional primary measures is the tight combustion control

achieved by diverse advanced monitoring tools also developed and widely demonstrated by

INERCO. These advanced monitoring tools are mainly focused on the measurement of local

in-furnace combustions conditions and unburned carbon-in-ash.

The achievement of optimized combustion scenarios is based on the characterization of actual

in-furnace combustion conditions using the ABACO-Opticom technology. This monitoring

technology provides precise surveillance of the combustion process through the direct and

automated measurement of gas concentration profiles (O2, CO, CO2, NOx, SO2) on the

envelope of each fuel and air stream entering the combustion chamber and near the furnace

walls (Figure 5). The information provided is highly valuable for preventing detrimental

corrosion to boiler walls and for tuning key combustion parameters to optimize emissions and

efficiency.

Figure 4: Images of the upgrading of windboxes and burners

Figure 5: ABACO-Opticom Technology: Analysis Unit and Sampling Probes

In addition, adequate measurement of unburned carbon-in-ash or Loss on Ignition (LOI) in

coal-fired boilers is an issue of utmost importance for optimizing boiler operation. This

parameter has direct relationship to efficiency and establishes a targeted boiler tuning limit

for NOx minimization. It is also a necessary measurement for the surveillance of ash quality

for its sale to the cement industry.

The automated monitoring of carbon-in-ash is accomplished by using the ABACO-LOI

monitoring system, which is unique industrial equipment based on the application of

laboratory reference techniques used for the characterization of fly-ash (Figure 6). This

system shows a very tight alignment to the dynamics of the plants without drifts or

recalibrations when physical-chemical properties of coals or ash vary. Standard errors are

kept below 0.2% for the highest monitoring demand (over 8,000 measurements per month).

RESULTS FROM THE ADVANCED PRIMARY MEASURES

The monitoring and regulation technologies previously described can be managed using an

integrated control system, named ABACO. ABACO has an Expert Software that is able to

perform the closed-loop operation and optimization of combustion process, while reducing

potential boiler corrosion problems by avoiding extremely low O2 concentrations at the boiler

walls.

To illustrate the potential of the ABACO approach, Figure 7 shows three different operating

scenarios in a front-wall coal-fired boiler characterized by measuring the individual coal

supplies to the burners and the gas concentration profiles obtained through ABACO-

Opticom:

Figure 6: ABACO-Loi technology for the on-line monitoring of carbon-in-ash

EFFICIENCY & NOx IMPROVEMENT

(EFFICIENCY: +0.8%

NOx REDUCTION: 15% - 20%)

LEVEL 3

COMax. = 0.7%COMax.= 5.5% COMax. = 1.8%

BASELINE OPERATIONEFFICIENCY MAXIMISATION

(IMPROVEMENT: +1.0%)

LEVEL 3

LEVEL 2

LEVEL 1

Oxygen concentration per burner

<0.5

COAL SUPPLY

DAV Deviation from Average Value

Oxygen concentration per burner (% v/v, d.b.)

<0.5 0.5-1.0 1.0-1.5 1.5-2.0 >2.0

COAL SUPPLY

DAV = Deviation from Average Value

DAV<-10% -10%<DAV<0% 0%<DAV<+10% DAV>+10%

Baseline operation: this shows significant imbalances in the coal supply and in-furnace

O2 concentrations.

Optimized efficiency scenario: where balancing the coal supply through ABACO-Coal

dampers has led to an increased efficiency of 1.0%.

Operating scenario seeking a combined optimization of efficiency and NOx reduction:

this has produced up to 20% NOx reductions and heat rate improvements around 0.8% by

the balancing and staging of the coal supply.

The availability of ABACO-Opticom and FLEXICOM-LNB technologies has enabled the

reliable and safe implementation of coal stratification strategies to achieve optimized

operating scenarios with minimum NOx emissions. Figure 8 shows the coal distribution

profiles and the NOx reduction achieved in two different operating scenarios relative to the

baseline coal vertical distribution in a tangentially-fired boiler with 6 burner levels:

Maximum coal stratification based on the differential tuning of mills (fuel biasing), the

balancing of coal supply and the enhanced control provided by ABACO approach,

resulting in a 22% reduction in NOx emissions.

Combined application of FLEXICOM-LNB (Addition Module) and ABACO-Opticom

technologies to achieve a reliable distribution of the coal flow supplied by the uppermost

mill between the remaining mills, which produces a 41% reduction in NOx emissions

without affecting coal fineness.

Figure 7: Application example of ABACO-Opticom technology

10% 15% 20% 25% 30%

1

2

3

4

5

6

Coal flow rate per boiler level (%)

Bo

ile

r le

ve

l

Baseline

Coal stratification

22% NOx

reduction

10% 15% 20% 25% 30%

1

2

3

4

5

6

Coal flow rate per boiler level (%)

Bo

ile

r le

ve

l

Baseline

FLEXICOM

41% NOx

reduction

The technological approach described has been demonstrated by INERCO in over 140 test

programs conducted in more than 70 industrial facilities worldwide, highlighting its broad

experience in pulverized coal power plants. INERCO has carried out over 100 optimization

projects, including combustion tunings and supply of equipment for combustion

characterization and optimization, in more than 50 coal-fired power units.

These optimization programs have been carried out in combustion units with power outputs

of up to 625 MWe, for different loads ranging from MCR to MSG conditions, with different

boiler/furnaces designs (tangential, front-wall, opposed-wall, arch-fired, vertical, etc.), firing

any type of fuel (bituminous and sub-bituminous coals, lignite coals, anthracite coals,

biomass, oil, natural gas, etc.) and co-firing very diverse secondary fuels (low quality coal,

oil, pet coke, biomass, meat bone meal, etc.).

There have been multiple goals for these projects. They have focused on the diagnosis and

targeted tuning of combustion units to achieve different objectives, such as a global

combustion process optimization, the minimization of NOx emissions, the improvement of

combustion efficiency and heat rate, the minimization of carbon-in-ash, the optimization of

fuel usage (new fuel blends including poor quality or difficult coals, or else, secondary fuels),

the maximization of plant availability or the balancing of combustion performance.

Table 1 summarizes the main results achieved by applying the described approach with

varying scopes in accordance with the specific design and operating characteristics of each

plant. These results indicate that the proposed approach provides the most favorable

scenarios achievable through the use of primary measures before the implementation and

integration of DeNOx secondary measures.

Figure 8: Application example of coal stratification strategies

and FLEXICOM-LNB technology

NOx (% ) Heat rate (%)

Closed-loop ABACO+ ABACO-Loi 20 ÷ 33% 0.0 ÷ 0.5%

Closed-loop ABACO+ ABACO-Loi+FLEXICOM-LNB 40 ÷ 50% 0.2 ÷ 0.5%

Combustion tuning based on ABACO-OPTICOM 14 ÷ 38% 0.6 ÷ 1.2%

Opposite 215-340 Open-loop ABACO 17 ÷ 19% 0.0 ÷ 0.3%

Closed-loop ABACO 20 ÷ 30% 0.5%

Combustion tuning based on ABACO-OPTICOM

and FLEXICOM approach19 ÷ 43% -

Combustion tuning based on ABACO-OPTICOM 29 ÷ 53% -

Arch-fired 260 Combustion tuning based on ABACO-OPTICOM 20 ÷ 30% -

Closed-loop ABACO 30 ÷ 60% 0.5% ÷ 2.0%

Closed-loop ABACO+ABACO-Loi 40% 1.5%

Closed-loop ABACO+ABACO-Loi+

combustion and milling systems retrofitting60% 1.5%

Front 40-60 Closed-loop ABACO 13% ÷ 21% 0.6% ÷ 1.3% Combustion optimization at low loads

Vertical Closed-loop ABACO 20% 3.0%

Opposite Closed-loop ABACO 20% ÷ 50% 2.4% ÷ 5.0%

Fuel

Reductions achieved

Other collateral problems solved

Anthracite +

Secondary

fuel

(petcoke,

(bituminous

coal)

Arch-fired 330-350

Front

Bituminous

coal

Tangential

Technological scopeCapacity

(MWe)Design

Fuel-oil /

Fuel-gas

125-625

40-360

25-175 (1)

Minimization of carbon-in-ash

Reliable co-firing of secondary fuels

Combustion optimization at low loads

Improvement of coal fineness

Increased production

Combustion optimization at lower duties

Reliable co-firing of secondary fuels

Maximization of plant availability

Reduction of slagging, fouling

Improvement of coal fineness

Combustion optimization at low loads

Optimization of start-ups and shut-downs

Reliable co-firing of secondary fuels

SECONDARY MEASURES: ADVANCED SNCR TECHNOLOGY

In order to comply with NOx emissions limits imposed by environmental legislation using a

cost-effective approach, INERCO has developed a non-catalytic abatement technology which

is highly complementary with the primary measures previously described. Different images

of this novel technology can be seen in Figure 9.

Figure 9: Images of the non-catalytic abatement technology developed by INERCO

Table 1: Main results achieved by the application of advanced primary measures

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

9,0

0,24

0,26

0,28

0,30

0,32

0,34

0,36

0,38

0,40

0,42

0,44

Rea

gen

t flow

(l/min

)Lo

ca

l N

Ox (lb

/MM

BT

U)

Distribution profiles along the boiler

Injection profile

Local NOx profile

Reagent supply profile

LEVEL 5 ½ T~1,600 ºF

LEVEL 5 T~1,750 ºF

In general, the maximum potential of non-catalytic secondary measures, such as selective

non-catalytic reduction (SNCR) systems, has been demonstrated in small industrial and

power boilers. However, the reduction efficiency achieved in larger coal-fired power units

has been low, mainly due to the boiler size (reagent penetration and mixing into the flue gas)

and the difficulties in identifying optimum temperature windows with variable operating

scenarios. The following are the key performance parameters in the SNCR process:

Temperature – O2 and CO concentrations define the operating temperature window

where the NOx reduction reactions occur at high efficiency rates.

NOx profiles – NOx profiles are produced in the combustion zone based on the specific

design of the boilers. However, these profiles are non-uniform and not constant over

time due to the dynamics linked to the combustion process. Precise knowledge of the

NOx content in the injection zones is needed to achieve optimized injection of the correct

reagent quantity per injection port.

The approach designed by INERCO is intended to meet these parameters by achieving highly

flexible reagent injection in the most suitable furnace areas. The availability of the INERCO

ABACO-Opticom advanced in-furnace monitoring capabilities provides the temperature

profile and composition (NOx, O2 and CO) upstream of the injection zone to assure optimized

injection profiles based on the individual control of reagent injection in each lance. The

application of optimized reagent supply strategies as those shown in Figure 10 brings two

direct benefits: higher NOx reduction rates compared with conventional applications and

effective control of ammonia slip.

Figure 10: Reagent supply profile based on in-furnace temperature and local NOx

CASE STUDY: FULL INTEGRATION OF INERCO’s PRIMARY AND

SECONDARY MEASURES

The most extensive integration of the primary and secondary measures developed by

INERCO was accomplished in a 350 MWe arch-fired boiler in which a blend of anthracite

and bituminous coal is burnt. The technological approach that was implemented and

successfully validated by INERCO at this facility was carried out in two main phases.

1) Implementation of primary measures

The primary measures installed at the reference plant consist of advanced combustion

optimization technologies and enhanced combustion regulation capabilities, with the scope

detailed below and also depicted in Figure 11:

Combustion optimization technologies:

- ABACO-Opticom system for the advanced in-furnace monitoring of gas

concentrations (O2, CO, CO2, NO) in the area of influence of each burner.

- EMIR technology, for the automated sampling and monitoring of coal flows to the

burners.

- ABACO-LOI, for the automated sampling of fly-ash from the ESP and the subsequent

characterization of carbon-in-ash by determining the Loss on Ignition (LOI).

- Automated ABACO-Coal dampers, for the balancing of coal supplies to the boiler

- Improvement and automation of air regulation capabilities.

- Integration of new and existing monitoring and regulation systems within the ABACO

Expert System for the optimized closed-loop control of combustion process.

Figure 11: General arrangement of primary measures at the target combustion unit

Retrofit of combustion regulation capabilities:

- Installation of regulating devices in all mill classifiers, so as to convert them into

adjustable classifiers, with wide capability to improve coal fineness.

- Retrofit of the windbox (modification of air registers and construction of OFA ducts

and dampers) to achieve an improved stratification of combustion air.

- Retrofit of burners for an enhanced stratification of coal supply.

- Validation of FLEXICOM-LNB approach by the specific implementation of

appropriate operating scenarios.

The implementation of this approach provided extraordinary results: 44% NOx reductions,

along with a cumulative heat rate improvement of 1.5% relative to the historic baseline.

2) Demonstration of the Advanced SNCR technology

The novel NOx abatement technology conceived by INERCO was validated at the target

facility using the following approach:

Implementation of the Advanced SNCR technology adapted to the injection of urea or

ammonia in up to 8 injection points simultaneously. These injection points were selected

in three different furnace areas based on existing temperatures.

Arrangement of a complementary monitoring approach consisting of:

- In-furnace temperature monitoring through optical pyrometers and High Velocity

Thermocouple (HVT) probes.

- In-furnace manual measurement of gas concentrations (O2, CO, CO2, NO) in

additional points to those monitored by ABACO-Opticom.

- In-situ ammonia slip monitoring through a laser-based gas analyzer.

-

By conducting more than 130 injection tests, INERCO was able to demonstrate the feasibility

of its global DeNOx approach, with the following results:

Additional NOx reductions ranging from 40% to 50% when adding the Advanced SNCR

technology to the optimized scenarios previously identified.

The application of this approach together with the implementation of operating scenarios

based on FLEXICOM-LNB approach led to an 83% reduction in NOx emissions relative

to the baseline. The NOx emissions achieved was close to the 2018 emission limit

imposed by the applicable environmental legislation for this power unit.

The resulting NOx reductions were achieved while holding sustainable ammonia slip

values around 5 ppmv. Although these results are satisfactory, the installation of a slip

catalyst would lead to lower ammonia slip, while achieving further NOx reductions.

The results achieved show that there are alternative technological solutions to SCR in order to

comply with the emission limits imposed on coal-fired power plants. The technological

approach developed by INERCO is characterized by its high flexibility, which can be

customized based on the specific design and operating conditions of each power unit.

ECONOMIC ASSESSMENT

In order to perform an economic assessment of the technological approach developed by

INERCO in comparison with the application of SCR technology it was necessary to establish

several hypotheses to make an accurate and comparable estimate of investment and operating

costs (Table 2).

Target NOx abatement efficiency 60 – 85%

NOx abatement efficiency of INERCO’s approach

(primary measures, FLEXICOM-LNB and Advanced SNCR) 60 – 70%

Price of catalyst volume (labor cost included) $9,000

Price of reagent (ammonia, 25%) $200/t

Full-load equivalent hours 4,000 hours

Reference year to incur investment and operating costs 2012

INERCO approach: a cost-effective alternative to new SCR systems

When an SCR system is not available in the target power facility the comparative assessment

should focus on the investment costs to reach the required NOx emissions. The approach to

be implemented would vary based on the specific characteristics of each combustion facility.

In certain cases, the exclusive application of optimized primary measures and SNCR may not

be enough to achieve the highest NOx reduction rates. Therefore, the scope of the approach

should be widened by applying additional NOx reduction techniques, such as reburning, high-

temperature reagent injection or non-conventional catalytic technologies.

Assuming a target NOx reduction ranging from 60% to 85%, the comparative assessment

between SCR and other alternative approaches leads to significant capital costs reductions, as

shown in Figure 12. Considering a required 60% NOx reduction, the approach proposed by

INERCO would fulfill these requirements with associated capital costs reductions of over

50% compared with conventional SCR approaches. In this case, the investment cost of the

SCR system is 85 $/kW, and for the optimized approach 30-40 $/kW.

If an 85% NOx reduction is required, additional technologies to FLEXICOM-LNB and

Advanced SNCR have to be considered. Capital costs associated with the SCR system are

around $95/kW and the investment costs for the implementation of the additional

technologies are in the range of $15-$30/kW. Then, the total costs of INERCO approach are

$45-$70/kW depending on the required retrofit. When extrapolating this assessment to other

representative operating scenarios, it can be concluded that the savings in investment costs

would typically vary from 30% to 50%. However, in some particular scenarios this saving

can be increased up to values around 70%.

Table 2: Economic assessment hypotheses

0

20

40

60

80

100

120

SP

EC

IFIC

INV

ES

TM

EN

T C

OS

TS

($

/kW

)

MAXIMUM EFFICIENCYSCR (3 catalyst layers)

PRIMARY MEASURES+ ADVANCED SNCR

TYPICAL OVERALL SAVING: 30%-50%

PRIMARY MEASURES +ADVANCED SNCR +OTHER TECHNOLOGIES

TARGET 60%NOx REDUCTION

TARGET 85%NOx REDUCTION

MAXIMUM SAVING: ~ 70%

COST RANGE DEPENDING ON TECHNOLOGY SCOPE

INERCO approach: a valuable complement to existing SCR systems

The economic assessment developed has been extended to the case in which an SCR system

is already available and therefore, the economic analysis should target a comparison of

operating costs to reach a precise NOx reduction. Two different cases are considered:

Conventional case: conventional primary measures and exclusive performance of the

SCR system with maximum abatement potential.

Optimized case: joint application of advanced primary measures including FLEXICOM-

LNB and the SCR system with reduced scope (e.g. reduction of one catalyst layer).

Assuming a target NOx reduction efficiency of 80%, the results achieved when comparing

these cases show a 62% reduction in ammonia consumption and a 20% reduction in catalyst

volume. Therefore, the operating costs linked to reagent and catalyst savings are reduced

from $620 to $330 per ton of abated NOx. These results are clearly shown in Figure 13.

This analysis has been extrapolated to other representative scenarios, which establishes

typical operating cost savings ranging from 40% to 60% when installing advanced primary

measures based on the FLEXICOM-LNB technology. The savings achieved result in Return-

on-Investment (ROI) periods as low as 1-2 years, based on the specific conditions of each

facility. The catalyst replacement cost was not considered in this analysis because is highly

dependent on the outage flexibility of the plant. Still additional savings should be considered

for this reason.

Figure 12: Comparative assessment of investment costs

0

50

100

150

200

250

300

350

400

450

500

OP

ER

AT

ION

AL

CO

ST

S ($

/to

n a

ba

ted

NO

x)

CATALYSTMANAGEMENT

CONVENTIONAL PRIMARY MEASURES + MAXIMUM EFFICIENCY SCR (3 catalyst layers)

ADVANCED PRIMARY MEASURES + REDUCED SCR (2 catalyst layers)

REAGENT CONSUMPTION

OVERALL47% SAVING

20% SAVING

63% SAVING

SUMMARY

The challenge of achieving NOx emission limits imposed by environmental legislation, while

preserving the profitability of industrial combustion facilities, requires a careful analysis to

implement an optimized approach. Some generating companies may decide to only install

conventional catalytic solutions (SCR), which is the most reliable technology to reach the

most stringent NOx emissions levels. Although this may be the most straight-forward

technological alternative, it is definitely not the most cost-effective solution.

INERCO has developed a state-of-the-art approach based on the joint integration of advanced

customizable primary and secondary measures. This approach relies on novel tools, such as

FLEXICOM-LNB technology, conceived to take full advantage of coal supply profiles under

the enhanced control provided by cutting-edge monitoring technologies already demonstrated

by INERCO (e.g. ABACO-Opticom, ABACO-LOI). In addition, this approach incorporates

an Advanced SNCR technology specifically designed to achieve maximum NOx abatement

efficiencies in large-sized boilers. Both solutions are highly complementary, as they can be

easily integrated by applying INERCO advanced in-furnace monitoring technologies.

This integral approach has been validated at different coal-fired power plants. The broad

experience gathered in these facilities and the development of comprehensive testing

campaigns integrating all the technologies developed by INERCO has resulted in the

achievement of highly remarkable results: over 80% NOx abatement efficiencies while

avoiding collateral problems, such as excessive ammonia slip or penalties in carbon-in-ash,

boiler efficiency or steam temperatures.

Figure 13: Comparative assessment of operating costs

The economic assessment developed shows how this innovative approach can be considered

as an alternative solution to conventional catalytic solutions based on the reduced investment

costs achieved, typically ranging from 30% to 50%, with maximum savings around 70% for

particular operating scenarios. In addition, it may also be a valuable complement to SCR

technology due to the reduction in operating costs, generally varying from 40% to 60%.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the collaboration of other personnel involved in the

activities described. Special thanks are given to the technical staff of IBERDROLA and

INERCO.

REFERENCES

[1] Rodríguez, F.; Tova, E.; Delgado, M.; Bittner, J. “Reliable LOI Monitor Based On

Calcination and Weighing Techniques”. Power Engineering, Vol. 116, June 2012.

[2] Rodríguez, F.; Tova, E.; Morales, M.; Delgado, M.; Portilla, M. “Parallel Heat Rate

and NOx Optimization by Innovative Control of Pulverized Coal and Combustion Air

Supplies”. 2010 MEGA Symposium, Baltimore.

[3] Rodríguez, F.; Salvador-Camacho, L.; Morales, M.; Cañadas, L.; Otero, P.; Gómez,

P.; Ramos, M. “NOx Control and Heat Rate Improvement through Primary Measures

based on Advanced Furnace Control”. 2003 Mega Symposium, Washington D.C.

KEYWORDS

NOx, combustion, optimization, FLEXICOM-LNB, SNCR, SCR, ABACO, ABACO-LOI,

ABACO-Opticom, primary measures, secondary measures, monitoring, corrosion, operating

cost, investment cost, carbon-in-ash.