Creating SCRSCR of Tomorrow

Smart SCR catalyst Smart SCR catalyst as as a digital disruption to a digital disruption to

Selective Selective Catalytic Reduction Catalytic Reduction ccomplement to omplement to Industry 4.0 Industry 4.0

Dr Rathindra Nath DasCorporate R&D, BHEL

RNDAS@bhel.in 9448490012

Contents

1. SCR technology today: Overview: Catlyst : Control strategies

2. What influences SCR Catalyst performance: overview of current capabilities

3.SCR Technology today: Challenges & gaps summerized

4. Digital technology to address the gap transforming to next generation catalyst

5. FBG sensor array

6.Demonstration

7. New generation of catalyst optimization system proposed

8. Conclusions : Looking forward to next generation catalyst

1. SCR technology today: background

1. SCR technology today : Catalyst

• is the best available Catalyst ruling the technology world over decades, but • unable to upgrade to the next generation despite above industry demand, in spite of• huge resources poured in research, except for the minor improvements

Ref: Review on latest developments in modified Vanadium-Titanium-based SCR catalysts, Chinese J of Catalysis 39(2018) p1347

Space velocity Vs NOx reduction efficiency

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Space velocity, 1/hour

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Space velocity = gas flow rate / Vol. of catalyst

Other supplier

Developed

As presented at the International conference on “Exploring power plant emissions reduction: technologies & strategies”, London, 23-24 May, 2005

Milestones Date

1 A proposal prepared for SCR DENOX plant for a 250 MW Indian coal-fired Power Plant

1989

2 International Patent granted to BHEL on Honeycomb Manufacturing

1996

3 BHEL Catalyst Tested at direct stream of FETF Boiler with other catalyst (Siemens/Argillon)

Sep 2004

4 Proposal prepared for 25 MW slip stream SCR testing at RaichurThermal Power Plant

Jan 2005

5 Indigenous SCR Catalyst again tested at direct stream of APFBG test facility at R&D site

20152016

6 Smart SCR Catalyst patented by BHEL Mar2016

7 Slip stream catalyst tests at KPCL Bellary & other Thermal Power Plants

2017 Mar-

1. SCR technology today : Catalyst: no major shift seen since 1990

• Flue gas Residence time inside the catalyst volume

• NH3/NOx ratio and degree of gas mixing

• Inlet NOx concentration level

Flue gas velocity: increase reduce NOx reduction efficiency by limiting diffusion, adsorption and full reactionsolution : low Vspace more catalyst & cost

decrease reduce NOx reduction efficiency by excessive contact time oxidizing ammonia into NOxsolution : control ammonia and save cost

2. What influences SCR Catalyst performance : current capabilities

4NH3 + 4NO + O2 → 4N2 + 6H2O (Standard SCR reac on) 97 Kcal/mol NO

4NH3 + 2NO + 2NO2 → 4N2 + 6H2O (Fast SCR reac on) 180 Kcal/mol NO

SCR control types are SCR control types are based on the following based on the following setset--pointspoints and and measurementmeasurements

Approach 1 % NOx Reduction NOx Inlet & Outlet

Approach 2 Outlet NOx (ppm) air flow & NOx Outlet

Approach 3 Outlet NH3 (ppm) Outlet NH3

Ref: Tuning Ammonia Flow to Optimize SCR Performance Power 01/01/2010 | Tim Leopold, ABB Inc.

Model Predictive Controls (MPC) of multi-input, multi-output processes with equality and inequalityconstraints on the process variables are also used tooptimize the dosing control of ammonia in order to copewith the abrupt change of inlet NOx concentration.

Measurement of catalyst activity in situ during operation is the industry demand. One US company FERCo developed KnoxcheckKnoxcheck by providing almost online Lab facilities in situ to measure

reactor potential(RP)=catalyst activityarea velocity

The KnoxCheckKnoxCheck reactor potential test results for the period of 2005 to 2009. Relative to RPo the reactor potential of the individual layers when freshly installed.

2. SCR control strategies : revolving around the point measurements

Variations in Catalyst Inlet & outlet flue gas condition with best available control

Best available variation in Catalyst outlet NOx concentration plot (ppm@3%O2) Ref: US8108073B2

Field data

Simulation plot

Variation of Catalyst inlet NH3/NOx ratio modelled (% variation from average removal efficiency) Ref: US8108073B2

Field data

Simulation plot

Calculated NOx reduction and ammonia slip performance as a function of NH3/NOx ratio non-uniformity Ref: US2012/0282564A1

ChallengesPerformance variation of catalyst at various localized zones• spatial variations in flue gas velocity profile• Spatial variation in NOx profile • ash loading variation• localized temporary catalyst

blockage/erosion• permanent catalyst poisoning/deactivation

Gaps• Local catalyst activity during operation is so far assumed offline from

global average from few measurements or by estimation from trial & error• In situ online measurements are not affordable• Lack of dynamic information about happening in the SCR plant during

transient and load-change operations• Real optimization and informed catalyst management were lacking during

challenging operation

3. SCR technology today : challenges and gaps summarised

4.0 Digital technology to address the gap transforming to next generation catalyst

Gap or unsolved problems todayGap or unsolved problems today• Even highest efficient catalyst fails to control simultaneously NOx & NH3 emissions, because of its

inability to match the NH3 concentration profile to NOx concentration profile, resulting any one of the deficiencies

• Lower NOx reduction efficiency --if-- no NH3 slip• NH3 slip –if-- higher NOx reduction efficiency

• NOx concentration is non-uniform at catalyst entry & changes with boiler operating conditions• Non-uniform temperature and velocity distribution across the catalyst bed adds to the challenge

Traditional solutionsTraditional solutions• Calibrating each NH3 injection nozzle during start up trial run• cost and complexity prohibitive using multiple sensors for computing nozzle wise influence factor

during operation• Responding to Boiler load changes: Numerous control schemes (fuzzy logic, multivariable process

control (Model Predictive Control-MPC), feedforward strategies etc) tried, still it is a blind window

Digital solution:Digital solution:• Embedded optical sensors distributed in SCR catalyst volume, which can be mass produced along

with catalyst • The distributed temperature profile of the entire catalyst bed: online instant digitized catalyst

performance at individual local temperature level • Analysis of large online data during operation provides accurate catalyst temperature and real

time trend of catalytic activity to compute localized ammonia dose requirements• Digital optimization minimizes the sum of deviations can meet demanding requirement of NOx

emission, ultra-low NH3 slip and durability under challenging high-ash coal-fired Power plants.

5 FBG sensor array

FBG sensors for smart catalyst are designed and fabricated at CSIR-CGCRI, Kolkata.

The optical fiber with appropriate composition is drawn and desired Bragg Gratings are written using 244nm laser on preset sensor locations at CGCRI in-house facility & home expertise.

Design and fabrication of Catalyst & embedding the FBG Fiber are done at BHEL R&D with in-house facilities & expertise.

effB n 2

eesB

B pT

1

),( TfB

Array B

Array C

Array B

Array A

Array C

Schematic of FBG Array sensors A, B and C in the Catalyst Block

Arrangements of FBG Array sensors (Array-A, Array-B and Array-C) in the Catalyst Body

Schematic of sensor array placement in catalyst

Temperature plot of FBG sensor Array

6. Demonstration

Precise DeNOX Reaction lightoff and completion time when Ammonia starts and stops

6. Demonstration: optical measurements mirroring the Reaction Mechanism

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EXOTHERMIC RESPONSE AT CATALYST WALL

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DELAY IN SWITCHING OFF (RESPONDED IN THREE STEPS)

Temp (OC)

Time (s)

Actual Stoichiometric RatiosActual Stoichiometric Ratios

Why typical ASR = 1.05

currently ASR is adjusted to account for • temperature, • residence time, • degree of mixing, • catalyst activity, • small NO2 in flue gas which requires two moles

of NH3 per mole of NO2• allowable ammonia slip for a specific boiler

7 New generation of catalyst optimization system

Catalyst Activity feedback from each

zones of smart catalyst

Set zonal ASR values computing from

catalyst activity data

ASR calculation from single point NOx measurements

at inlet & outlet

Controlling NH3 control valves to

maintain localized zonal ASR set-points

Control flow diagram for improved SCR Catalyst performance by optimizing flow of ammonia (NH3) from each of NH3 injection nozzle

Boiler L1

L2

L3

T

C1

C2

C3

D

PC

M

EFs s

s ss

s ss

AIG1AIG2

AIG3

Note: Optical fibre cable : C, C1, C2, C3Catalyst (H1, H2) Layers : L1, L2, L3Ammonia Injection grid : AIG1, AIG2, AIG3Data analysis device : D, Transmitter : TManual console : M, Control strategy : E

Schematic view of smart SCR catalyst management system

8. Conclusions : Looking forward to next generation catalyst

We have described a smart catalyst system for real-time temperature sensing

of SCR catalyst and feed-back to control ammonia injection at every segments

in large volume of catalyst bed for most optimized operation.

The challenge for DeNOx SCR in Indian coal fired power plant is entered on

high ash level in the flue gas several times higher than most of the power

plants abroad where traditional SCR system is well established.

We believe the smart catalyst in combination with large data-analysis and

computations is going to be the next generation of digital control strategy

capable of handling the challenge and provide the best solution by real-time

performance optimization.

Thank you