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De nox





SIEMENS Honeycomb Catalyst SINOx R SW 40

Rev. Date Comments


This catalyst manual is intended to aid in the preparation and execution of

- Handling and installation

- Operation

- Maintenance and product monitoring


of the SCR catalysts in .............................................

In addition, it is intended to assist in the planning and provision of the necessary personnel and for safety analysis, release and monitoring by the responsible supervisory and inspection authorities.



1  Process Chemistry

2 Technical Data

2.1 Catalyst Specification

2.2 Design Data

2.3 Catalyst Performance

2.3.1 Guaranteed Life Time of Catalyst

2.3.2 Guaranteed values at catalyst outlet

2.3.3 Pressure Drop

2.4 Guarantee Conditions

3 Handling and Installation Instructions

3.1 Handling Specification

3.1.1 Handling Procedure

3.1.2 Packing

3.1.3 Transportation

3.1.4 Storage

3.2 Installation Procedure for Siemens SCR Catalyst Modules

3.2.1 Prerequisites for Installing Catalyst Modules

3.2.2 Sequence of Operations

4 Catalyst Operation

4.1 Startup

4.1.1 Cold Startup

4.1.2 Warm and Hot Startup

4.2 Normal and Borderline Catalyst Operation

4.2.1 Normal Operation

4.2.2 Borderline Operation

4.3 Shutdown

4.3.1 Shutdown for Short-Term Periods

4.3.2 Shutdown for Long-Term Periods (Major Inspection)

4.3.3 Extended Shutdown

5 Disturbances/Malfunctions

5.1 Fly Ash Deposits/Condensation on Catalysts

5.2 Prevention of Thermal Damage to SCR Catalyst

6 Catalyst Maintenance and Monitoring

6.1 Maintenance of the SCR System

6.1.1 Reactor

6.1.2 Operation Control Unit

6.2 SCR Performance Control

6.2.1 Daily Monitoring during Operation

6.2.2 Catalyst Monitoring and Sampling Procedure

7 Catalyst Module Exchange

8 Technical Information Data Sheet


1. Process Chemistry


The abatement of NOx (NO and NO2) is achieved by the use of a "Selective Catalytic Reduction (SCR) system". This is a dry flue gas treatment process, which uses ammonia (NH3) as a reducing agent.

The main chemical reactions are as follows:

(1) 4 NO + 4 NH3 + O2 cat > 4 N2 + 6 H20

(2) NO + NO2 + 2 NH3 cat > 2 N2 + 3 H20

Ammonia (NH3) is injected into flue gas and reacted with NOx in the SCR catalyst to produce nitrogen (N2) and water (H20).

Several side reactions occur under certain conditions. One of the major concerns is oxidation of SO2 to SO3 conversion.

2 SO2 + 02 → 2 SO3

This reaction has to be minimized by optimal catalyst design to reduce the formation of ammonium bisulfate and ammonium sulfate to a minimum.

NH3 + SO3 + H20→ NH4HSO4

2 NH3 + SO3 + H20→(NH4)2SO4

The condensation of the salts depends on SO3 and NH3 content in flue gas and the operating temperature. The condensation may cause plugging in equipment downstream of catalyst.

The condensation of ammonium bisulfate can occur in the catalyst at a higher temperature level due to the capillary pressure (capillary condensation which will cause partial reversible deactivation of the catalyst. Therefore the operating temperature has to be high enough to avoid the capillary condensation in the micro pore of the catalyst.


2. Technical Data


2.1 Catalyst Specification


Type: Honeycomb SINOxR SW40

Manufacturer: Siemens

Formulation: TiO2, V2O5, WO3 ceramic material

Catalyst volume: m3

No. of layers:


Open area:

Specific surface area: m2/m3

No. of catalyst channels 40 x 40

Elements cross section: mm x mm 150 x 150

Element length: mm

Number of elements per module:

Module dimensions

(length, width, height): mm

Number of modules per layer:

Module weight: kg


2.2 Design Data


Table 1: Design data


Flue gas (wet) Nm3/h

Flue gas temperature ℃

Composition (wet)

H20 vol %

CO2 vol %

N2 vol %

02 vol %

Reference 02 (dry) vol %

NOx (dry) as NO2 mg/Nm3 (11% 02)

PCDD/F ngTE/Nm3 (11% 02)

CO mg/Nm3 (11% 02)

TOC mg/Nm3 (11% O2)

Cd + TI mg/Nm3 (11% 02)

Hg mg/Nm3 (11% 02)

HF + HBr mg/Nm3 (11% 02)

Remaining heavy metals mg/Nm3 (11% 02)

PAH mg/Nm3 (11% 02) '

PCB + PCT + PCN mg/Nm3 (11% 02)

HCI (dry) mg/Nm3 (11% 02)

SOx (dry) mg/Nm3 (11% 02)

Dust (dry) mg/Nm3 (11% 02)


2.3 Catalyst Performance


2.3.1 Guaranteed Life Time of Catalyst


2.3.2 Guaranteed values at catalyst outlet

Ammonia slip

Penalty =   

   x Contract Price x 0.1


PCDD/F = Reactor outlet PCDD/F concentration in ngTE/Nm3, based on 11% O2


2.3.3 Pressure Drop


2.4 Guarantee Conditions


The catalyst must be handled and operated in accordance with the Design Conditions and this Catalyst Manual.


3 Handling and Installation Instructions


3.1 Handling Specification


This specification covers the handling, packing and transportation procedures for Siemens SCR catalyst modules: When performing this work, the applicable industrial safety regulations and the Technical Information Data Sheet for the catalyst sheet shall be observed.


3.1.1 Handling Procedure


Handling precautions:

The catalyst modules shall only be handled in compliance with the attached Technical Information Data Sheet.

- The catalyst elements (monoliths) are contained in carbon steel frames (hereafter modules). However, the top and bottom ends of the modules are open, thus exposing the elements to the atmosphere. Therefore the modules shall be handled with care to protect them from moisture due to rain, etc.

The protective screen on top of the modules is intended to protect the catalyst from larger fly ash particles during operation. It may also allow walking carefully on it during an inspection. Stepping or walking on the unprotected elements is prohibited.

- The catalyst modules are delivered in a horizontal position. The modules are wrapped

in plastic sheets strapped firmly to the wooden pallets. The covering protects the catalyst from excessive ingress of water in the short term, but must not be considered waterproof in the long term.

- The catalyst modules shall be handled carefully; mechanical shocks must be particularly avoided. Forklift operators must be instructed to use great care when lifting, transporting and setting down the modules. The transport pallet must be centered on the forks and only lifted high enough to clear any irregularities in the road/floor.


Typical Transport of Catalyst Modules with Fork Lift

- Modules shall be lifted only with a special lifting device (lifting beam) attached to the lifting lug on the module frame.

- The modules shall be handled carefully. Mechanical shocks must be particularly avoided.


3.1.2 Packing


- The catalyst modules are covered for transportation with a waterproof covering with no tears or holes. Covering of the new catalyst is carried out in the Siemens catalyst works under consideration of the particular transport conditions.

- Covering which has been removed shall be retained until it is certain that it is no longer needed.


3.1.3 Transportation


- See handling procedure.

- Catalyst modules shall not be stacked upon each other.


3.1.4 Storage

The following specifies the conditions under which storage is possible for suitably long periods without any change in the guaranteed properties such as NOx activity or SO2 conversion rate.

- The catalyst modules are delivered in a horizontal orientation. They shall not be turned to a vertical orientation for storage. The modules shall be stored in packed condition on the transportation pallets.

- The original covering (typically a plastic sheet) shall not be removed. The catalyst modules should be unpacked just before the catalyst is installed inside the SCR reactor, in any case. The plastic sheet protects the catalyst from becoming wet only for a short period. The catalyst modules shall be covered with suitable additional vinyl sheets when temporarily placed outside (e.g. during installation).

- The modules shall not be stacked.

- The modules shall be stored indoors and protected from rain. The modules shall be kept free from any kind of oils or other chemicals. The modules shall be kept dry as reasonably possible. If dry conditions inside of the catalyst wrapping can be guaranteed (similar to a warehouse: dry ground, closed doors, etc.) the catalyst modules may be stored in a container or tent (temporary warehouse) on site.

- The modules should be stored in a stable position on a firm and level floor.

Storage conditions shall be checked regularly (monthly) and recorded to ensure conformance with the above conditions. Siemens reserves the right to inspect the storage area prior to catalyst delivery.


3.2 Installation Procedure for Siemens SCR Catalyst Modules

This document covers the loading procedure for Siemens catalyst modules. The loading procedure is described only in general terms, as SCR reactors and on-site conditions vary from site to site.


3.2.1 Prerequisites for Installing Catalyst Modules

The catalyst is the heart of a DeNOx plant and it is essential to pay careful attention when handling it.

- The modules are delivered covered. Remove the covering just before installation and attaching the lifting beam respectively just before turning the modules to vertical orientation. The modules are delivered in a horizontal orientation. The modules shall be turned to vertical orientation using a special turning device.

- Take care not to subject the modules to mechanical shocks, such as hitting against the structure during lifting.

- Avoid installing on a rainy day to prevent the catalyst from becoming wet. If unavoidable leave the cover on the modules as long as possible, i.e. until the modules are moved inside the reactor.

- Always use a special lifting device (lifting beam).

- If a module is to be set down temporarily, place it on sleepers and cover it.

- The reactor beams shall be provided with special sealing strips that are installed before placement of the modules.


3.2.2 Sequence of Operations



Verify that unnecessary items, rubbish, etc. have been cleared from inside the reactor.

Verify that welding and grinding operations on module supports have been completed.

Install and perform test operation of loading unit, hoists, etc.

- Lay out gratings for walking on the reactor level where installation of modules is to begin.

- Baffle plates, sealing strips etc. shall be in stock and prepared.

- Appropriate lighting shall be provided within the reactor.

Installing Catalyst Modules

The catalyst modules shall be installed in compliance with the following general procedure:

Modules on pallets shall be transported to the turning device by forklifts or trucks.

- The grating on top of each module has to be removed to attach the lifting gear.

- Modules shall be lifted to the installation level by hoist (using a special lifting beam).

- Sealing strips shall be installed on top of the supporting beams.

- Modules shall be placed on the supporting beams.

- The grating on top of each module - if it has been removed for lifting the modules shall be installed again shortly after positioning of the module.

- Baffle plates between modules and reactor housing shall be installed, if applicable.

- Stepping or walking on the modules without any protection plate is not recommended.

- If welding is performed inside the reactor the catalyst modules shall be covered with metal plates, plywood or other suitable material.

- The location of each module (module-no.) shall be recorded (module arrangement plan).


4 Catalyst operation


4.1 Startup


The condition of the catalyst is decisive for the startup procedure used. A distinction is made between cold, warm and hot starts. As the condition of the plant may not be identical with that of the reactor, depending on configuration and mode of operation, cold warm and hot starts shall be based on the current condition of the catalyst. The condition of the reactor described here is based primarily on the catalyst temperature and the resulting of moisture entrapment.

Possible temperature extremes and gradients across the inlet area as well as over the height of the reactor are important in determining the reactor temperature. For this reason it is important to determine the temperature of the flue gas both upstream and downstream of the reactor as exactly as possible.


4.1.1 Cold Startup


A catalyst startup is considered a cold start if the catalyst temperature is < 150 °C at all times during the startup process.

The catalyst should be heated from the cold condition with hot air.

A maximum temperature gradient of 10 K/min shall not be exceeded. The temperature measurement at the reactor outlet can be used for monitoring the heat-up rate. Above <150 °C the temperature gradient shall not exceed 20 K/min.

A temperature step change must not exceed 100 K/min.

In order to prevent long-term condensate formation on the catalyst surface during the startup sequence the catalyst heat-up should not proceed at much slower heating rates than those given above.

Ammonia injection can be started when the minimum operating temperature to avoid ammonium sulfate formation (.......................) is reached.


4.1.2 Warm and Hot Startup


The difference between a warm and hot start lies in the differing catalyst temperatures when startup commences. A warm start is defined as a startup during which the temperature of the entire catalyst can be maintained > 150 °C at all times during the startup, a hot start is defined as a startup during which this temperature can be maintained above the minimum operation temperature for ammonia injection.

Warm and hot startup temperature gradients shall not exceed 20 K/min.


4.2 Normal and Borderline Catalyst Operation


4.2.1 Normal Operation


Nitrogen oxides in the flue gas react in the catalyst as a function of the amount of ammonia injected to form nitrogen and water vapor.

The catalyst is designed for normal operating temperature of ..........°C.

Abnormal furnace operation should be avoided at all times.

As the catalyst has is certain NH3 retention, NH3 injection rate changes have a delayed effect on NOx reduction. This effect must be accounted for in the SCR shutdown sequence. (Inlet NOx should equal outlet NOx before the SCR reactor is isolated.)


4.2.2 Borderline Operation


Catalyst operation at flue gas temperatures below minimum operating temperature with simultaneous NH3 injection must be avoided to prevent formation of ammonia salts (condensation in pores leading to deactivation). Ammonia salts form in the simultaneous presence of H20, SO3 and residual amounts of unconverted NH3 (slip), which combine to form ammonium hydrogen sulfate (NH4)HSO4 or ammonium sulfate (NH4)2SO4. Particularly the sticky and corrosive ammonium hydrogen sulfate which forms in this manner can precipitate out in the catalyst or on downstream components and cause catalyst deactivation as well as corrosion of plant components.

Continuous catalyst converter operation at temperatures above ............ °C must be avoided to prevent structural changes (sintering of catalyst pores) and hence deactivation.


4.3 Shutdown


The ammonia flow must be shut down at a flue gas temperature below minimum operating temperature.

Ammonia injection must always be terminated before the SCR reactor is isolated. The NH3 injection should be decreased such that the NOx level downstream of the reactor increases to that upstream of the reactor to ensure that most of the ammonia retained in the catalyst has reacted with the nitrogen oxides in the flue gas (this requires that the Nox measurement upstream and downstream of the catalyst remain in operation, even if the SCR plant is shut down).

Temperature gradients may not exceed 20 K/min at any location during shutdown.

In case of shutdown for a short-term and extended period all dampers should kept closed to bottle-up the SCR system in order to avoid quick cooling down of the SCR system.


4.3.1 Shutdown for Short -Term Periods


When the SCR system is shutdown for only a short-term period, it will cool down only slightly below normal operating temperature. It is therefore not necessary to perform the ammonia shutdown as described in section 4.3.

In addition all dampers (incl. bypass) should kept closed to bottle-up the SCR system.

Forced cooling of the SCR system should be avoided.


4.3.2 Shutdown for Long -Term Periods (Major Inspection)


In this case the ammonia shutdown sequence as described in section 4.3 is necessary.

To enable the soonest possible access to the plant, the catalyst should be cooled completely (however at a maximum of 10 K/min).

The reactor can be cooled down to a temperature of 150 ℃ with flue gas. Below this temperature, a 5 to 10 minute purge with clean air through the reactor will be initiated. The temperature difference between the cooling air and the catalyst shall not exceed 100 K. Complete cooling results in post-ventilation, i.e. removal of residual SO2, SO3 and NH3 from the reactor.


4.3.3 Extended Shutdown


Suitable measures must be taken to protect the reactor and hence the catalyst from contact with flue gas or ammonia in the cold condition. This holds especially for ammonia at temperatures below operating temperature and for flue gas below the acid dew point.

In addition, the catalyst must be protected from vapors, which could arise during washing of up and downstream equipment.


5 Disturbances/Malfunctions


- The ammonia shutoff valves shall be closed in the following cases:

· Flue gas temperature below minimum operating temperature


5.1 Fly Ash Deposits/Condensation on Catalysts


The catalyst elements are designed so as to prevent fly ash deposits as much as possible. Appropriate measures (e.g. baffle plates) shall ensure optimum flow through the catalyst. The formation of dead spaces or vortices must be prevented in the design insofar as it is possible to limit fly ash deposits or wear.

Fly ash deposits on the catalyst lead to increased pressure drop. The pressure drop should therefore be measured and recorded and the degree of blockage observed between the reactor inlet and outlet over time.

The catalyst elements shall be examined when accessed during major inspections for erosion or plug age to enable possible modification of the soot blower schedule.

Condensation of water or sulfuric acid on the catalyst shall be minimized in time, amount and frequency.

Particular care must be paid to catalyst operation in this regard.

Condensate, which forms in the reactor and flue-gas duct must be prevented from running down onto the catalyst elements.


5.2 Prevention of Thermal Damage to SCR Catalyst


Characteristics of Catalysts for Removing Nitrogen Oxides from Flue Gases Catalysts have been used for the removal of nitrogen oxides from flue gases in waste incineration plants in Germany since the early 90s. Nitrogen oxides (primarily NO and NO2, usually represented together as NOx) are converted on the catalyst surface with ammonia as a

reducing agent. The reaction products are elementary nitrogen and water.

TiO2/WO3/V2O5-based SCR catalysts are considered oxidizing catalysts due to their catalytically active composition, i.e. any oxidizable substances can be decomposed on

the catalyst in the presence of oxygen to naturally occurring substances such as CO2, CO, H20 and HCI. This decomposition reaction and hence the released heat or enthalpy of reaction is a function of the type and concentration of oxidizable substances in the flue gas, the degree of decomposition and the catalyst used.

In normal boiler operation, the concentration of oxidizable compounds in the flue gas of waste incineration plants is low and is governed by the stipulations in the 17th BlmSchV (Federal German Pollution Control Code). The oxidation potential in waste incineration plants is deliberately used with specially modified SCR catalysts for catalytic destruction of trace polyhalogenated organics such as dioxins and furans.

Development and Course of Temperature Excursions

In the event of disturbances in the combustion process in the combustion chamber of a waste incineration plant, conditions can arise which do not permit complete combustion of the waste input.

Two different types of causes can lead to this type of operating conditions.

Firing Mode

- Startup/shutdown conditions

- Unfavorable waste composition

Non-uniform waste input

Temperature drops in combustion chamber.

Upset Conditions:

- Power failure (blackout)

- Failure of primary and/or secondary air supply

- Failure of induced-draft fan.

These operating conditions can lead to air deficiency and thermal decomposition of the feed material with the release of pyrolysis gases. In addition to carbon monoxide, common pyrolysis gases are cracking and partial oxidation products of larger organic molecules, which can be converted on the SCR catalyst if the reactor or catalyst temperature is sufficiently high. SCR catalysts at the usual temperatures in waste incineration plants do not convert the primary component in such pyrolysis gases, carbon monoxide.

However, pyrolysis gases also contain smaller fractions of compounds which in part are oxidized at relatively high rates at temperatures < 300°℃. These include in particular the unsaturated hydrocarbons (ethane, propane, ethyne etc.), which increase the catalyst temperature due to the released heat of reaction and can thus increase the operating temperature sufficiently to also oxidize less reactive gases. Saturated hydrocarbons are transformed mostly only to carbon monoxide. No significant conversion of methane occurs below 400°C. Once the catalyst has been heated in this way to temperatures > 450°C, conversion of the carbon monoxide to carbon dioxide also takes place with increasing conversion rates. As carbon monoxide is often present in significant quantities in pyrolysis gases, the released heat of reaction for complete oxidation to CO2 can result not only in temperature increases in the catalyst bed which cause thermal overloading and sintering with reduction or loss of its catalytic properties, but an increase in the flue-gas temperature downstream of the SCR reactor is also possible, which could damage downstream systems.

Recommendations of Catalyst Manufacturer for Preventive Measures or Protective Equipment

These measures can be implemented either on the firing side or on the SCR reactor side.

Preventive measures or protective equipment on firing side:

- Complete combustion of feed material

Both supply of a well mixed residual waste which is not too wet as well as targeted and sufficiently high air supply in the combustion chamber help to prevent the formation of pyrolysis gases which can still be further oxidized in the SCR catalysts.

- Increased operating reliability



Monitoring relevant exhaust-gas parameters can also increase operating reliability. In particular, these include measurement of CO, 02und organic carbon (Corg) at the boiler outlet, as well as AT upstream and downstream of the SCR catalyst.

It is recommended that individual limits be specified for all these parameters if possible to distinguish normal operation including startup and shutdown processes from upset operating conditions, and also to specify what specific measures should be taken if these limits are violated.

The following limits are recommended:

△T: - Triggering of a pretrip alarm at a temperature difference of ≧ 15°C upstream and downstream of SCR catalyst, targeted monitioring of developments in all parameters.

- Manual or automatic changeover to flue-gas bypass at △T ≧30°C.

Corg: - Triggering of a pretrip alarm at a pyrolysis gas concentration of≧ 2500 vpm, targeted monitioring of developments in all relevant parameters.

CO: - Triggering of a pretrip alarm at ≧ 5000 vpm, targeted monitoring of developments in all relevant parameters.

- Manual or automatic changeover to flue gas bypass at ≧ 1 vol.% CO.

02: - Triggering of a pretrip alarm at ≦ 4 vol.% 02 at boiler outlet, targeted monitoring of developments in all relevant parameters.

In addition to the bypass changeover, combined with plant shutdown with direct flue-gas discharge to the atmosphere if necessary, the measures to be implemented include the following:

- Removal of flue-gas heating equipment upstream of SCR reactor (in-duct burner) etc.

- Following early detection of a temperature increase, dilution of the flue gases and cooling of the SCR reactor with the largest possible volumes of fresh air.

Preventive measures or protective equipment on SCR reactor side:

- SCR reactor bypass

A flue-gas bypass around the SCR reactor and the heat exchanger as well if possible should be planned to prevent thermal overloading damage, which could affect the catalyst, SCR reactor or equipment downstream of the reactor due to exothermic oxidation of pyrolysis gases.

Activation of the bypass in the form of an automatic interlock shall be planned with suit able temperature or Corg limits. The interlock shall be suitably designed for blackouts.



Temperature recording, especially temperature difference monitoring, should be performed in the entire reactor across the flue-gas duct or reactor cross-section as well as on the individual catalyst levels.

- Reactor temperature

As the conversion and conversion rate of pyrolysis gases on SCR catalysts decrease sharply with decreasing temperature, the lowest possible SCR reactor temperature shall be targeted. This also results in a temperature buffer to critical CO oxidation levels. As mentioned before, CO is the main component of pyrolysis gases, which can still be oxidized, but is not converted significantly below 450°C. This temperature buffer enables early detection of a temperature increase in the reactor as well as implementation of corresponding measures.


6 Catalyst Maintenance and Monitoring


6.1 Maintenance of the SCR System


Regular inspections are necessary to maintain proper operation of the SCR system. Siemens recommends maintenance and monitoring according to the following descriptions.

The SCR system can be maintained by the furnace plant maintenance staff. The installation of a SCR system does not require the number of personnel to be increased as daily maintenance work is very limited.


6.1.1 Reactor


As the reactor involves no moving equipment, daily maintenance is almost unnecessary.

The reactor condition is monitored by instruments.


6.1.2 Operation Control Unit


For stable operation, the SCR operation control units should be comparable to and have the same reliability as the furnace control unit. The control units and analyzers should be inspected at the intervals recommended by the manufacturer.

6.2 SCR Performance Control

In order to estimate the service life of the catalyst during operation and to evaluate the need for catalyst replacement in advance, it is important to record the performance of the DeNOx plant over time.

Our operating experience to date indicates that the performance of the DeNOx plant deteriorates gradually, without any sudden changes. The long-term deterioration in DeNOx performance is due to the decrease in catalytic activity; in some cases, however, it is equipment related, e.g. non-uniform NH3 injection, fly ash accumulation on the catalyst equipment related, e.g. non-uniform NH3 injection, fly ash accumulation on the catalyst layer, etc.

For this reason, real DeNOx performance over time is recorded by collecting the following three data:

- Operating data from actual unit (daily operating records)

- Performance test data from actual unit

- Activity evaluation data from sampled catalyst


6.2.1 Daily Monitoring during Operation


The following data shall be monitored by the permanent instruments in the central control room:

- Flow rate

Change in NOx concentration and gas temperature at reactor inlet and outlet

- Relationship between NH3/NOx mole ratio and DeNOx rate

- Increase in leaked NH3 concentration

- Increase in pressure drop across reactor

If disturbances are noted in daily monitoring, the performance test should be carried out immediately to determine the cause and to take appropriate measures.


6.2.2 Catalyst Monitoring and Sampling Procedure


Product monitoring is a source of useful information on catalyst behavior during operation in an SCR plant. Changes in catalyst properties are detected by conducting tests on catalyst samples after defined periods of service.

To assess the condition of the catalyst at any time, it is important that in addition to recording measured plant data (e.g. NOx, temperature), catalyst material be removed from the reactor at regular intervals and tested.

The suggested frequency of catalyst sampling is approx, once per year.

During inside inspection of the reactor, the catalyst is sampled by replacing special test elements.

Testing is performed to facilitate:

- Planning rearrangement and replacement strategies

- Catalyst service life assessment

The following properties are regarded as decisive for the operation behavior of the catalyst:

- Change in catalytic properties

- Change in external structure

- Change in inner surface and pore structure

- Change in mechanical properties

- Composition of accumulated deposits

Analyses may be performed with scanning and transmission electron microscopes, the later being equipped with a microanalysis probe. The technique permits identification of poison elements and detection of changes in the catalyst surface and grain structure.

The pore volume as well as the inner surface (determined by Hg porosimetry and N2 adsorption) may be determined only when the activity measurements show unexpected deactivation rates. In this case EDX measurements, wet chemical investigations and other tests are performed (see attached table).

The catalytic properties may be checked in a test setup with a precisely defined test flue gas.

A report about the results from the above mentioned measurements/investigations compares the actual data with the reference measurements and gives an outlook of the expected catalyst behaviour for the future. In case of severe catalyst deactivation the possible reason for will be described. Proposals to improve the catalyst behaviour in the future will be made in such a case.

Each module is prepared for easy removal of two honeycomb sample elements.

Eight (8) replacement elements are furnished with the main catalyst lots at installation time. They are typically stored in the unit warehouse.

Along with the replacement elements some extraction handles for the sample holders have been delivered. If they are not longer available, a pair of screwdrivers or similar objects will do also.

Sampling procedure:

If possible, sampling should be avoided at locations, which are heavily fouled by fly ash.

The pertinent safety regulations must be adhered to in entering the reactor.-

· extract sample from module

· markup top and bottom side (permanent marker)

· remove holder

· note: unit, date, reactor level, module location on sample (permanent marker)

· fill in sample data in a module arrangement plan

· wrap sample without cleaning in plastic for shipment, add copy of module plan(s)

· insert fresh replacement element into holder and than into the module

The catalyst samples shall be packed so as to prevent breakage during shipping,

The samples shall be delivered to the following address:

· will be specified later


7 Catalyst Module Exchange


The catalyst design is based on the steady-state operating point specified for the end of the guarantee period.

The catalyst demonstrates constant behavior over its service life.

This results in ammonia slip being lower for the fresh catalyst than at the end of the service life. Fresh catalysts are used so as to maintain a constant NOx emission level and hence a low ammonia slip.

If the predetermined ammonia slip or the NOx emission limit are exceeded, it is not necessary to exchange the entire catalyst as it still has a relatively high residual activity.

Catalyst addition in the spare layer is sufficient for this.


8 Technical Information Data Sheet


The Technical Information Data Sheet refers to the active ceramic material itself.

During the installation procedure of the new catalyst modules catalytic dust formation or skin contact to catalytic material is not expected if the catalyst modules are handled in compliance with this manual.

In case of handling spent catalyst protective precautions are necessary, because spent catalyst may contain fly ash deposits and trace elements from flue gas.









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Update: 18th Aug. 2006

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