oslo, february 17th, 2010 thankyou mr. ………… good afternoon … · 2014. 11. 17. · 1....

HIGH DUST SELECTIVE CATALYTIC NOx REDUCTION AT WTE PLANT IN BRESCIA

Paolo Rossignoli – Mario Nenci – Lorenzo Zaniboni A2A, Brescia, Italy

Oslo, February 17th, 2010

PresenterPresentation NotesThankyou Mr. …………good afternoon ladies and gentlemen,The topic of my presentation today is the waste to energy plant in Brescia, with special focus on the project of the high dust selective catalytic Nox reductionThe presentation is prepared with contribution of Lorenzo Zaniboni and Mario Nenci, who has followed the project from the beginning.

TERMOUTILIZZATORE(The waste to energy plant of Brescia)

••Waste preventionWaste prevention

••Separate collection (for material recycling)Separate collection (for material recycling)

••Composting of organic wasteComposting of organic waste

••Energy from remaining waste (renewable energy)Energy from remaining waste (renewable energy)

••LandfillingLandfilling minimization (only safe residues)minimization (only safe residues)

INTEGRATED WASTE MANAGEMENT SYSTEM

PresenterPresentation NotesThe plant in Brescia is part of an integrated waste management system, compliant with European waste priorities, based on 5 points:Waste preventionSeparate collection, for developing and improving material recyclingComposting of organic wasteEnergy from remaining wasteLandfilling minimizationThe plant in Brescia is based on this philosophy

1. ENVIRONMENTAL PROTECTION

2. HIGH EFFICIENCY OF ENERGY RECOVERY

3. SAFETY, RELIABILITY, AVAILABILITY

DESIGN GOALS:


PresenterPresentation NotesThe main focus of the design, and of all further implementations of the plant, is environmental protection, combined with high efficiency in energy recovery.Of course, all the activities, had to be done at the maximum level of safety, and pursuing the highest reliability possible.


584 584 km of double pipekm of double pipe

130.000 inhabitants supplied130.000 inhabitants supplied

38,538,5 MmMm33 heated volumeheated volume

17.391 17.391 connected buildingsconnected buildings

695 695 MWMWthth230 230 MWMWelel

1 km

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P.Plant south

WTE

DISTRICT HEATING SYSTEM OF BRESCIA

PresenterPresentation NotesI'd like to show three slides to describe the Brescia district heating, where the plant is connected in order to obtain the maximum recovery of energy;Three main plants supply the district heating, the two largest, in the southern part of the city, produce energy in cogeneration.You can see the main dimensions of the system, the first developed in Italy, started in 1972, …


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PresenterPresentation Notes… As you can see it’s a system still in progress; more than 70% of the inhabitants in Brescia currently live or work in buildings connected to the district heating.



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• NAT. GAS

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• SOLID WASTE and BIOMASSES

PresenterPresentation NotesImproving the attention to the environment, since 2010, all the plants supplying the district heating will use no oil, (brown areas in the graph), replaced with natural gas, in yellow: we will have more yellow and no brown in 2010. (The total value each year is mainly influenced by the winter season).The green area shows the contribution of Waste To Energy plant, raising from 1999; the steps are clear where the 2nd and 3rd line has been inserted.


PresenterPresentation NotesThe plant presents three independent combustion lines; the first two, in service since 98/99, are fed with municipal solid waste.The third one, in service since 2004, is fed with residual biowaste from paper industry, wood industry and food industry.The lines are rather identical: the slide shows a schematic section of one of them.


WASTE BUNKER

PresenterPresentation NotesThe bunker for the waste storage is managed with three cranes, for mixing the waste and for feeding the lines.The cranes can be set in full automatic mode by the operators.(On the left you can see the doors for the discharge of the waste and, on the right, the feeding pits)


Combustion grate under construction

PresenterPresentation NotesA picture showing the grid during the construction.These boilers are based on the reverse acting grate type, designed by Martin.The grate combustion area is around 100 square meters, composed of 15 steps, 8 movable and 7 fixed, and divided in 30 sectors.For each sector, the air flow can be adjusted independently, and automatically regulated by an infrared camera.Also the feeding and movement of waste inside the boiler, as well as primary and secondary air supply, are automatically regulated by an “expert system”.

MAIN TECHNICAL DATA

• Heat capacity of treated waste (3 boilers) 310 MW

• Waste throughput 3 x 33 t/h

• Electrical generation capacity (net) 80 MWel

• Heat generation capacity 170 MWth

ISO 14001 Environmental certification in april 2006


PresenterPresentation NotesThe plant uses the heat released by combustion for electricity production and district heating.After the upgrade during last year, the nominal capacity of waste throughput is around 100 tonns per hour for the whole plant, generating 310 MW of heat capacity.In full electricity mode, the net electrical power produced is about 80 MW; in cogeneration mode the net electrical power is 70 MW and the district heating capacity is 170 thermal MW.

OPERATIONAL DATA 2008

• Treated waste 801,000 tons( of which biomass 270.000 tons )

• Electricity production (net) 570 GWhel

• District heating 568 GWhth

• Fossil fuels saving (Tons of Oil Equivalent) > 150,000 TOE

• CO2 avoided emissions > 400,000 tons


PresenterPresentation NotesI’ve reported in this table the operational data referred to the year 2008, (quite the same as 2007,) because last year we performed large maintenance and upgrading on the system, and consequently the figures do not reflect the normal operation.

NOx CONTROL METHODS

• PRIMARY (NOx prevention)

- staged combustion (gradual O2 supply)- combustion temperature control

• SECONDARY (NOx reduction)

- SNCR (Selective Non-Catalytic Reduction)

- SCR (Selective Catalytic Reduction):- “High dust” (on raw gas)- “Tail-end” (after gas cleaning)- “Low dust” (after gas de-dusting)

PresenterPresentation NotesLet’s start with the specific topic of NOx control.From the beginning, the three lines of the plant were already optimized to minimize the emissions of NOx and ammonia, by gradual oxygen supply and temperature control, and to reduce the ammonia consumption.They were also equipped with Selective Non Catalytic Reduction systems for NOx removal.From the beginning of operations, in 1998, all these systems permit to comply very well with European limits: 200 mg/Nm3 for Nox, no limit was set for ammonia.Same years later, ASM decided to investigate the possibility to install an additional device for further emission reduction, in order to anticipate lower regional limits, that will be set in the next years for Waste to Energy installations: 10 mg/Nm3 for ammonia and a guide value of 80 mg/Nm3 for Nox.It was decided to install a High-Dust Selective Catalytic Reduction, instead of the typical Tail-End SCR, as a demonstrative solution aimed at higher energy efficiency and lower pressure losses and, consequently, lower operational costs.The idea was to couple the existing Non Catalytic system with the additional High-Dust SCR, and in this way to obtain a so called “hybrid system”, that will enhance the total DeNOx capacity.It’s the first industrial scale installation on a waste plant“High dust” and not other ones, because it operates on raw gas: “tail end” needs higher temperature, that means use steam for pre-heating the flue gases, and “low dust” needs electrostatic precipitator; for each of them there are additional costs and volumes needed.

HIGH DUST SCR LOCATION


PresenterPresentation NotesAnother advantage we had in Brescia: the installation of the High-Dust SCR was made easy, because, from the beginning of the plant design, sufficient space in the flue gas path was left available.This predisposition has minimized installation costs, because few modifications where required to adapt the existing boiler.

HIGH DUST SCR LAYOUT


MIXER

CATALYST LAYER

(SPACE FOR UP TO 5LAYERS)

FLUEGAS

DAMPERS

NOx NOx

PresenterPresentation NotesThe design of the High-Dust installation was developed taking into account the possible problems the catalyst could have, and the uncertainties in its effectiveness and behavior.For these reasons, the installation provides space for the insertion of up to 5 catalytic layers into the gas path, as well as the possibility of bypassing the catalyst, in case of clogging, and continuing the operation of the plant as in its “old” configuration.The catalytic layers are installed on movable trolleys, which can be extracted while the SCR is bypassed. This favors quick inspections and cleaning

IMPLEMENTED NOx CONTROL IN BRESCIA WTE(starting situation - since 1998)

• PRIMARY

- low combustion excess air- 30 compartment grate- infrared camera for optimization of primary andsecondary air supply

- flue gas recirculation

• SECONDARY (NOx reduction)

- SNCR (NH3 injection with 27 nozzles, positioned atthree levels)


PresenterPresentation NotesSeveral systems for minimizing air pollution were already installed before SCR, all of which limit the generation of pollutants.Especially for NOx these systems are:combustion with a low excess of air30 independent sectors for primary air feedingoptimization of primary and secondary air supply by an infrared camerapartial recirculation of flue gases, to achieve a high turbulence and gas mixing in combustion chamber, containing at the same time the oxygen concentration, in order to limit NOx formation.preheating of combustion air (normally to 120°C)Besides, injection of ammonia from several different levels, complete the original Denox system

SNCR DENOX SYSTEM


PresenterPresentation NotesYou can see here a schematic draw of the system for reducing emissions, completed with a fabric filter, at the end of the flue gas path.


INSTALLATION AND TESTING OF A SCR “HIGH DUST” SYSTEM(non industrially available yet)

GOALS:

- further NOx reduction (120 80 mg/Nm3)

- ammonia slip improvement

- lowering ammonia consumption

- keep high energy plant efficiency

PresenterPresentation NotesThe main goals of the project.NOx European and Italian limits actually are set at 200 mg/Nm3; a regional law in Lombardia fixes today 120 mg, with a further goal of 80 mg/Nm3.Non Catalytic system doesn’t guarantee this value, and besides ammonia slip escapes to 20-30 mgAmmonia slip limit will be fixed from the first of January of next year at 10 mg/Nm3, again by regional law.Of course, a2a want to obtain the compliant with the limit, lowering ammonia consumption, and keeping the highest plant efficiency as possible.-----------------------------

-> HD SCR (already adapted for this in the nineties but then abandoned due to a lack of suppliers)

PROBLEMS:

- catalyst clogging- catalyst poisoning

ADVANTAGES:

- much higher energy efficiency (no need of gasreheating and lower gas pressure losses)

- simpler installation- lower investment and operating cost

SCR “HIGH DUST” SYSTEM(non industrially available yet)

PresenterPresentation NotesThe particularity of High-Dust SCR is to treat the gas in a location inside the boiler, where the gas temperature is suitable for the catalytic reaction, (about 250-300 celsius), but where the fly ash content is rather high, with a possible high incidence of clogging.Special arrangements are designed to handle the high amount of ash in the flue gas: (the channels of the catalysts have to be large enough to allow the dust to pass through, without plugging the channels).The High-Dust system has an important advantage. The flue gases are sufficiently hot and do not require re-heating, with benefit for the energy balance of the plant

• installation: 2005 Sep. – 2006 Feb.

• operation: started 2006 Mar. (1st phase – one cat. layer)

• inspection: Sep. 2006 (cleaning and catalyst analysisshowing some pore plugging and catalystpoisoning with sulphates)

• 2nd phase: started 2006 Oct. after inspection (2 cat. layer)

• inspections: 2007 Apr. and Sep. (only cleaning)2008 Apr. (erosion starts to become evident)

November: removal of one layer and installation of a new 2008 layer

SCR “HIGH DUST”History highlights


PresenterPresentation NotesThe installation of the High-Dust Sselective Catalyst Reduction in Brescia, started in September 2005 (- taking advantage of the shut down of the unit nr.2, due to annual maintenance.)(The work began with the insertion of the dampers in the flue gas path. This arrangement made it possible to continue the installation work, while the unit was in operation.)Installation of the systems was completed in February 2006. In March the 1st phase of catalyst tests started using only one layer of catalyst.Six months later, in September 2006, the catalyst was extracted for the first cleaning and analysis. The analysis showed some pore plugging and poisoning caused by sulphates. The second testing phase started in October 2006 with the addition of a second catalyst layer.In 2007 catalysts were cleaned, in April and September, without performing any analysis on their deactivation.A successive inspection in April 2008 revealed some erosion of the catalyst, and in November the first layer was substituted by a new one.

SPACE FOR SCR HIGH DUST INSTALLATION


PresenterPresentation NotesQuickly some pictures about the installation: here we can see the space free before the installation …

TERMOUTILIZZATORE (The waste to energy plant of Brescia

HIGH DUST SCR

SPACE FOR

SCR HIGH DUST

INSTALLATION

PresenterPresentation Notesthe space for installation from another point of view …

CATALYST UNDER CONSTRUCTION


PresenterPresentation Notesand here finally the blocks of plates ready for insertion on site.

NOx- NH3 emissions

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HIGH DUST SCR RESULTS


PresenterPresentation NotesNow let's move on to the results.From the left of the graph, we see: the red and green lines represent respectively the ammonia slip and the ammonia consumption.Ammonia slip, red pen, is improved very much already with the first catalyst layer, lower than 10 mg/Nm3 of ammonia, guarantying at the same time the limit of 80 mg/Nm3 for NOx that we wanted.(The rising trend seen after a few weeks is due to tests for stressing the system, made with set for NOx output under 70 mg - see blue line down to 40 mg, before the stop for second layer installation.)The second layer does better, especially for ammonia slip, showing an improvement in the reaction.

HIGH DUST SCR RESULTST , Δp SCR

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PresenterPresentation NotesThe slide shows the operational temperature, in red, (between 250 and 300 Celsius,)and, especially, it shows, the trend of pressure losses, very small, always under 1,5 mbar, around 1 mbar immediately after the cleaning operations - where the lines are interrupted.Downward peaks are due to short boiler stops.

NOx and NH3 emissions monthly media 2006 - 2007 - 2008 - 2009

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PresenterPresentation NotesFrom another point of view and for a more complete assessment, it is interesting to observe the performance of the plant, in terms of NOx and ammonia-emissions, with and without the High-Dust SCR. This comparison can be approached by comparing the measure of line 1 and line 2 during a certain time span.Line 1 and 2 are in fact identical, with the only difference being that line 2 has the additional High Dust SCR.The two lines have the same process components, and they are arranged in the same way. Moreover, the same waste is used, since it is picked from a single waste bunker, where it is mixed.(It is also assumed that the measurements of the two lines are comparable.)The light blue series shows very clearly that, for each month, the average of the ammonia slip released by the SCR of line 2, with 2 layers, is much lower than line 1 without SCR, and reaches the goal of always remaining under 10 mg/Nm3.Without the High Dust SCR, violet data, line 1 doesn’t reach the goal.

L1: SNCR only L2: SNCR + HD SCR (2 layers)

• NOx: 80 - 90 60 - 70 mg/Nm3

• NH3 slip: 10 - 30 2 - 6 mg/Nm3

• NH3 consumption: 0.22 0.18 m3/h (25% concentrated)

• Pressure losses: negligible

SCR “HIGH DUST”TEST RESULTS


PresenterPresentation NotesI'd now like to sum up the main points of the comparison:guarantee of NOx emission under 80 mg/Nm3ammonia slip under 10 mg/Nm3, with a very important reductionrelevant reduction also in ammonia consumption, 1/3 on averageand finally negligible pressure losses-----------------------------------

nh3 high fluctuation erosion: new material in test on line 3. 1 layer every 2 years is equivalent to the ammonia, therefore if we improve the duration there will be a saving

• new geometry in order to increase plates stiffness

• increasing plates thickness

• new composition of the catalyst material in order to

increase plates hardness

“HIGH DUST” SCR

Modifications of the catalyst to reduce erosion


PresenterPresentation NotesAfter 4 years of operation, we can understand that the main problem with this kind of device is the erosion.On the other hand, the fast deactivation of the catalyst is also an issue.We are analyzing and working with the supplier of the catalyst layers (Argillon), on both aspects, with major attention on the first one, because it has the most influence on the life-span of the device; (after less than 3 years we needed to substitute the first layer installed on line nr. 2.)-------------stiffness = rigiditàthickness= spessore

CATALYST AFTER 2 YEARS OF OPERATION


Before Cleaning

After Cleaning

PresenterPresentation NotesQuickly some pictures taken during the maintenance.You can see here the surfaces before and after cleaning …

TERMOUTILIZZATORE (The waste to energy plant of Brescia)

HIGH DUST SCR

INSPECTION OCTOBER

2009

PresenterPresentation Notes… a detail of clogged layer …


HIGH DUST SCR

CATALYST REMOVED AFTER 32 MONTHS OF OPERATION

PresenterPresentation Notes… here the component removed …


HIGH DUST SCR

CATALYST REMOVED AFTER 32 MONTHS OF OPERATION

PresenterPresentation Notes… and finally in this one you can observe the results of the erosion, that uncover the grid which supports the catalytic material … (ceramic + vanadium oxides)

HIGH DUST SCR

FUTURE TEST STEPS :

monitoring of fouling and activity of catalyst with new geometry

optimization of catalyst layout (single / multiple layers)

optimization of duct cleaning with modified geometry

lifetime assessment of the catalyst with new materials

industrial cost evaluation


PresenterPresentation NotesBriefly, the next steps, that we think need to be taken, in order to continuously improve the system:monitoring of fouling and activity of catalyst with new geometryoptimization of catalyst layout in terms of number of layersoptimization of duct cleaning with modified geometrylifetime assessment of the catalyst with new materialsindustrial cost evaluation during a longer period of operation

HIGH DUST SCR

CONCLUSIONS:

improving the reaction between ammonia and NOx


low impact on the plant efficiency: small pressure losses and low impact on fan consumption

life-time rather short, but costs relatively small in comparison with other SCR systems:

• costs for reheating the flue gas and energy for IDfan (vs Tail-end)

• costs for ammonia consumption (vs pure SNCR)

PresenterPresentation NotesI'm going to conclude by summarizing 3 positive points:the system improves the reaction between ammonia and NOxit has a very low impact on the plant efficiency: it generates small pressure losses introducing negligible extra consumption in IDfanit remains to improve the life-time, which is rather short, but costs are relatively low in comparison with other SCR solutions:it saves costs for reheating the flue gas and energy for IDfanit reduces costs for ammonia consumptionSupported by these conclusions, a2a is currently working for the optimization of the SCR on line nr.3 and it’s preparing the installation on line 1.

[email protected]@[email protected]

PresenterPresentation NotesFor more details you can find mail of the people involved within the projectThankyou very much for your attention

mailto:[email protected]:[email protected]:[email protected]

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oslo, february 17th, 2010 thankyou mr. ………… good afternoon … · 2014. 11. 17. · 1....

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