Gas Cleaning by SCR and ESP

Transcription

1 Gas Cleaning by SCR and ESP State of the Art Technology for NO x Reduction and Dust Separation Steinmüller-Engineering GmbH A Siemens Company Prepared by: Presented by: Dr. Manfred Schmoch Peter J. Grobmüller Germany Bogdan Neagoe Siemens SRL / Romania Page 1

2 SCR Technology SCR (selective catalytic reduction) Page 2

3 The oxides of Nitrogen, mainly NO and NO 2 (i.e. NO x ) are toxic gases: Reactions with water cause acid rain: damage of plants Close to the ground NO x forms ozon: a poisonous gas for breathing In the higher atmosphere NO x destrois ozon: increasing levels of UV radiation Page 3

4 NO x molecules are reduced by ammonia: NH 3 NH 3 is also a toxic gas: Danger for drinking water Inhaling low concentrations only is lethal already Emissions to the athmosphere must be minimized Basic reactions with NO x : 4 NH NO + O 2 4 N H 2 O 4 NH NO 2 + O 2 4 N H 2 O Instead of toxic NO x and NH 3 the final products are: Nitrogen N 2 and Water H 2 O Page 4

5 The first step to low NOx emissions are low NOx burners! Natural reaction (SNCR): Catalytic reaction (SCR): Small temperature range: C additional equipment for part load conditions Lower temperature level in a practical range of C Minimum clean gas NO x content: ~ 150 mg/nm³ dry NH 3 slip > 10 ppmv Possible clean gas NO x content: < 50 mg/nm³ dry NH 3 slip < 2 ppmv possible Page 5

6 Examples of catalyst elements Page 6

7 Example: Coal Fired Boiler (high dust arrangement) NH 3 -Injection Static Mixer SCR Catalyst layers: reduction at C ECO reactor Soot blowers or acoustic horns Air-pre-heater boiler SNCR: Natural reduction at C Page 7

8 Competence and experience is required for: Preparing a homogeneous flue gas regarding temperature, NO x content and dust concentration Injection and intensive mixing of NH 3 into the flue gas Providing an even flow distribution over the catalyst cross section Implementation of Catalyst plant in the existing structure Analysing the operational conditions regarding the development of the catalyst activity over time Page 8

9 Page 11

10 ESP Technology ESP (electrostatic precipitator ) Page 15

11 The basic technology of ESP is more than 100 years old. Up to today thousands of ESPs separate the dust from the gas flow of big plants especially: power stations cement plants steel plants and other industrial applications Page 16

12 Special features compared to other filter technologies like cyclons or bagfilters: Possible clean gas dust contents < 10 mg/nm³ dry Low pressure losses: < 2,5 mbar High availability with operational times Insensitive against operational disturbances: high temperature, temporary humidity Little maintenance necessities Very low demand of operational energy Page 18

13 Example 1: ESP of Power Plant Govora 7, Romania Revamping of ESP Item 1: Flow optimization by means of numerical flow calculation (CFD) Item 2: Old analog controllers replaced by modern digital controllers. Additional PLC as coordinator for rapping, heaters and energy minimization Item 3: Replacement of internals Items 4: Dismantling and montage of mechanical and electrical equipments Page 26

14 Insulation work at the ESP Page 32

15 Installation of new roof girders Page 33

16 Lifting of prepared collecting electrode by means of a support frame Page 34

17 Implementation of collecting electrodes Page 36

18 Implementation of discharge electrodes, type rigid and unbreakable Page 37

19 New 3-phaseTR sets on ESP roof Page 39

20 ESP casing 1 finished Page 40

21 Clean gas dust concentration: originally after revamping > 250 mg/nm³ dry > 30 mg/nm³ dry Page 41

22 ESP behind FCC plant Original clean gas dust concentration > 40 mg/nm³ (dark brown dots), above legal level New controller: in the beginning better clean gas values, but steadily increasing clean gas values (orange) New controller + NH 3 flue gas conditioning (yellow): again lower values, but still increasing gradually Additionally coordination of high voltage level and rapping (red): gradually decreasing clean gas values, steadily low Page 44

23 ESP behind FCC plant After 5 years of continuous operation the clean gas dust level is still below 20 mg/nm³ The originally intended replacement of the ESP could be avoided. Page 45

24 Questions?! Contacts Peter J. Grobmueller Director Division Oil & Gas and Energy Service Bogdan Neagoe Head of Business Unit E S SF & E S SR bogdan.neagoe@siemens.com Page 46

25 Thank you! Discharge electrode with corona Page 47