Flue Gas Cleaning Systems Status and Trends

Transkript

1 Flue Gas Cleaning Systems Status and Trends Dipl.-Ing. Rudi Karpf ete.a GmbH, Lich WtERT Annual Meeting Europe Brno, Czech Republic October 2010

2 Contents 1. Introduction 2. Presentation of several flue gas cleaning systems 3. Optimization of flue gas cleaning systems 4. Conclusion

3 Dry Absorption Conditioned Dry Absorption SNCR Boiler NaHCO 3 + HOK R Bag Filter HEX SNCR Boiler H 2 O Q Ca(OH) 2 + HOK R Bag Filter landfill landfill recirculation SNCR Spray Absorption Boiler Lime slurry + H 2 O SA Ca(OH) 2 HOK Bag Filter SNCR Wet Scrubber HOK Boiler Bag-Filter HEX S1 Lime slurry S2 recirculation landfill recirculation landfill Waste water Q = quench R = reactor SA = spray absorber S1/S2 = scrubber HEX = heat exchanger Source: fisia-babcock

4 Characterristics of dry and wet flue gas treatment systems Wet systems Low additive amount (SR 1), respectively low residues amount Dry sytems Higher additive amount(sr 1,6 up to >2), respectively higher residues amount Expensive additives (e.g. NaOH) Cheaper additives(e.g. Ca(OH) 2 ) High removal capacity for HCl and SO 2 selective removal multistage System Waste water treatment Good removal efficiency non selective removal Single stage system Simple and no sensitive components Need a pre dust collector Need not an additional dust collector Higher dust/aerosol emission PCDD/PCDF- removal with ADIOX grids and AC-injection Low maintenance effort Very good removal efficiency for heavy metals and PCDD/PCDF on AC High space need No wet stack is necessary,

5 requirement for an optimized additive use at a dry system Characteristics of the plant / Infrastructure lime sodiumbicarbonat Low additive costs + - High residues costs - + Tail-end SCR-DeNOx-plant + 1) /- + Maximum need for heat recovery + 1) /0 + Use of dry fuel (waste) +/- + low HF- and SO 2 -emission values + - High Hg-removal + - APC-System with puffer capacity (Emission) good; 0 neutral; - not so good 1) By using PTU-process

6 Basics of (conditioned) dry absorption systems Reactivity of pollutions in respect of.. Lime SO 3 > HF > HCl >> SO 2 > CO 2. Sodiumhydrogencarbonat SO 3 > HCl > SO 2 >> HF

7 Influence of the removal efficience with lime HCl-removal relative flue gas humidity the increase of the relative flue gas humidity occur an increase of the HCl-removal efficiency flue gas temperature up to 200 C the HCl-removal efficiency decrease in respect of the lower relative flue gas humidity. >200 C HCl-removal efficiency increase in respect to the higher temperature (kinetics)

8 Influence of the removal efficience with lime SO 2 - removal relative flue gas humidity the relative flue gas humidity has much more influence of the SO 2 -removal as the HCl-removal; that means with an increase of relative flue gas humidity the SO 2 -removal will increase significant flue gas temperature in the opposite to the HCl-removal the SO 2 -removal becomes worse with an increase of temperature in respect of the decrease of flue gas humditiy

9 Reactions of the dry absorption system with lime (Ca(OH) 2 ) SO 2 + Ca(OH) 2 CaSO 3 x ½ H 2 O + ½ H 2 O SO 3 + Ca(OH) 2 CaSO 4 + H 2 O 2 HF + Ca(OH) 2 CaF 2 + 2H 2 O CO 2 + Ca(OH) 2 CaCO 3 + H 2 O 2 HCl + Ca(OH) 2 CaCl 2 x 2H 2 O Reaction of lime with Chlorhydrogen in two steps: Ca(OH) 2 + HCl Ca(OH)Cl + H 2 O (l) Ca(OH)Cl + HCl CaCl 2 + H2O (l) Reaction of lime with Calciumchlorid: Ca(OH) 2 + CaCl 2 2 Ca(OH)Cl

10 Reactions of the dry absorption system with lime (Ca(OH) 2 ) the experience shows, that the SO 2 -removal increase with the presents of Ca(OH)Cl. possible reactions can take place: Ca(OH)Cl + SO 2 CaSO 3 + HCl (but not proper!) a higher proberbility is the exchange of anions 2 Ca(OH)Cl + SO 2 CaSO 3 + CaCl 2 + H 2 O

11 The presents of liquid water increase the reactivity of lime The speed of the chemical reactions at a liquid phase are much more higher as at a solid phase in respect of ion formation

12 Basics for the dry absorption with lime Mechanism of the gas absorption HCl HF Ca(OH) 2 SO 2 CaSO 3 x ½ H 2 O + ½ H 2 O CaF 2 + 2H 2 O CaCO 3 + H 2 O Hydratphase CaCl 2 x 2H 2 O

13 Influence of acid gas components removal with lime

14 Operation range of single stage dry absorption systems H 2 O Bag Filter 1 Q Urea/NH 4 OH (SNCR) (t > 180 C) NaHCO 3 + AC Residues H 2 O Bag Filter 2 Q fan Stack Ca(OH) 2 (18 m²/g) + AC Residues 3 SA lime slurry + H 2 O Bag Filter HCl 2500 mg/m³ SO mg/m³ NOx 100 mg/m³ (emission figures) Ca(OH) 2 (40 m²/g) + AC Residues

15 HCl, SO2 (mg/nm³,tr.) Rohgas HCl, SO2 (mg/nm³,tr.) Reingas WtERT Annual Meeting Europe - Brno, Czech Republic October 2010 Experience with conditioned dry absorption systems HCl (Rohgas) EBS-plant Romonta SO2 (Rohgas) HCl (Reingas) SO2 (Reingas) :00 02:24 04:48 07:12 09:36 12:00 14:24 16:48 19:12 21:36 00:00 Uhrzeit (24 h) Quelle: ALSTOM Power

16 Experience with conditioned dry absorption systems Wte-plant Ludwigshafen Quelle: Lühr-Filter

17 Operation range of multistage flue gas systems If the HCl-raw gas concentrations as a permanent load is > 2500 mg/m³, a multistage system is necessary. HCl 2500 mg/m³ SO mg/m³ NOx 50 mg/m³ (emission figures)

18 Operation range of multistage flue gas systems HCl 2500 mg/m³ SO mg/m³ NOx 100 mg/m³ (emission figure)

19 Potential of Optimizing the biggest potential of lime based systems is an increasing of the relative humidity! to increase the relative humidity there are several possibilities: recuperative gas cooling, for example with a heat exchanger about water injection at a cooling tower about steam injection Furthermore for a good removal efficiency it s important to have. A good flow and dust distribution (filtration velocity & filter cake ) attendance of enough reaction salts, especially Cl-salts

20 Potential of Optimizing the biggest potential of sodiumbicarbonate systems is. keep sure for enough high temperature warranty of a homogeneous distribution to realize high enough residence time f(t, Filtersystem) high surface or small particle sizes

21 Potential of Optimizing Substitution of spray absorption by a pure water injection few calcium carbonate formation and a bigger particle surface for the mass transfer to get a better stochiometry (it means a more economical system) better removal efficiency, because the absorbers are mostly over dimensioned for a pure water injection and in that case the operation temperature can be reduce (<140 C) a heating system at the bottom area of the absorber is necessary to avoid corrosion

22 Development / PTU-Process Principle of partiellen Taupunktsunterschreitung (PTU-Process) Conveying air flow & lime mixing zone with locally dew point decreasing flue gas flow flue gas duct

23 Enthalpie h1+x [kj / kg trockene Luft] Temperatur [ C] WtERT Annual Meeting Europe - Brno, Czech Republic October 2010 h-x diagram R M ; = 1 S Kondensation L Dampfeindüsung K Randmaßstab: h1+x / x Pol 0 relative Rauchgasfeuchte [p D / p S ] Beladung x [g Wasser / kg trockene Luft]

24 Potential of Optimizing application of PTU-process is at existing dry absorption systems with lime, when the flue gas humidity is to low or a furthermore temperature reduce is not possible. already used at EBS-plants municipal waste incineration plants Hazardeous waste incineration plants

25 lime / steam lance of PTU-process

26 13:00 13:14 13:28 13:42 13:56 14:10 14:24 14:38 14:52 15:06 15:20 15:34 15:48 16:02 16:16 16:30 16:44 16:58 17:12 17:26 17:40 17:54 18:08 18:22 18:36 18:50 19:04 19:18 19:32 19:46 20:00 20:14 20:28 20:42 Reingas [mg/nm³ tr.] / Kalkdosierung [%] Rohgas [mg/nm³ tr.] WtERT Annual Meeting Europe - Brno, Czech Republic October 2010 tests for the steam influence at wte-plant Wuppertal Dampfeinfluss ; Eindüsstelle 2, Kalkhydrat, RG-Temperatur bei 145 C T auf C angehoben Dampf aus Dampf ein Injektor, Zellenrad und Schnecke zugewachsen Zeit [min] HCl Reingas SO2 Reingas Kalkdosierung [%] HCl Rohgas SO2 Rohgas

27 Potential of Optimizing Multiple Additiv Injection Sodiumbicarbonat Combustion Cooling Tower/ Spray Absorber Reactor Bag Filter Waste Bunker Water Lime (Ca(OH)2)/ AC Residues Lime Stone Sodium Hydroxide (NaOH)

28 Conclusion conditioned dry absorption systems are high efficient and cheap systems, also for high HCl-concentrations witch process (wet / dry) or additive have to be use, depend on many factors and must be proved each new plant and location It is very important to have a optimized process temperature respectively a defined relative flue gas humidity

29 Conclusion spray absorption after waste combustion systems is not so effectivly and not economically the rebuilt/shift to a conditioned dry absorption requires not huge retrofit actions the development of the flue gas conditioning by steam with the PTU- process has a lot of advantages, especially for retrofit of existing plants for high HCl-concentrations >2500 mg/m³ (average load) or for lower emission figures like HCl < 5 mg/m³ are multiple stage systems are necessary

30 If there would be only one truths, it wouldn't be possible to paint hundred pictures about the same theme. Pablo Picasso

31 5. Tagung Biomasse & Abfall Emissionen Mindern und Rückstände nutzen Besonderheiten der Sprühabsorption Der Kalk wird in seiner reaktivsten Form, nämlich als Kalkmilch in den Rauchgasstrom eingebracht! weckt hohe Erwartungen an eine gute und effiziente Abscheideleistung

32 5. Tagung Biomasse & Abfall Emissionen Mindern und Rückstände nutzen Besonderheiten der Sprühabsorption Betriebserfahrungen von ausgeführten Anlagen zeigen jedoch bei Müllverbrennungsanlagen - ausreichend gute Abscheideleistungen jedoch bei Stöchiometrien von 2,2 bis >2,5 (oftmals unter Zuhilfenahme von einer zusätzlichen Zugabe von hochreaktivem Kalkhydrat) bei fossil befeuerten Kraftwerken - ausreichend gute Abscheideleistungen bei Stöchiometrien von 1,4 Woher kommt dieser Unterschied?

33 5. Tagung Biomasse & Abfall Emissionen Mindern und Rückstände nutzen Besonderheiten der Sprühabsorption 1. Oberflächenstruktur des in Form von Kalkmilch eingebrachten Kalkhydrats Die erforderliche Stoffaustauschfläche verringert sich infolge der tropfenförmigen Agglomerationen, die bei der Verdampfung der Kalkmilch entstehen REM-Aufnahmen von frisch gelöschtem Kalkhydrat von Ca(OH) 2 /CaCO 3 aus einer MVA-Sprühsorption mit Kalkmilch

34 5. Tagung Biomasse & Abfall Emissionen Mindern und Rückstände nutzen Besonderheiten der Sprühabsorption 2. Hoher Carbonatanteil / geringere Verweilzeit in der wässrigen Phase der Kalkmilchtropfen (Suspension) stellt ein sehr basisches Milieu dar Bildung eines hohen Carbonatanteils!

35 5. Tagung Biomasse & Abfall Emissionen Mindern und Rückstände nutzen Besonderheiten der Sprühabsorption 2. Hoher Carbonatanteil / geringere Verweilzeit in der wässrigen Phase In trockenem Zustand ist das Calciumcarbonat aufgrund seiner hohen Gitterenergie und seiner kompakten Oberflächenstruktur relativ inert (Kalkstein). Von Säuren wird es jedoch unter Abspaltung von CO 2 zersetzt. Daher kommt es in der flüssigen Phase zu einer Reaktion mit den sauren Schadgasen HCl, HF und SO 2 Je länger das Calciumcarbonat in der wässrigen Lösung (Suspension) vorliegt, desto effizienter ist die Abscheidung (wenig Calciumcarbonat)

36 5. Tagung Biomasse & Abfall Emissionen Mindern und Rückstände nutzen Besonderheiten der Sprühabsorption 2. Hoher Carbonatanteil / geringere Verweilzeit in der wässrigen Phase Sprühsorption hinter fossil befeuerten Kraftwerken - Prozesstemperatur von ca. 80 C - relative Rauchgasfeuchte von ca. 70% lange Verweilzeit Sprühsorption hinter Müllverbrennungsanlagen - Prozesstemperatur von C - relative Rauchgasfeuchte von 4-7%

37 5. Tagung Biomasse & Abfall Emissionen Mindern und Rückstände nutzen Einsatzbereich mehrstufiger Verfahren Wirtschaftlichkeit im Vergleich einer 2-stufigen Trockensorption(NaHCO3 u. Ca(OH)2) und einem Hybridsystem Grundlagen Verbrennungskapazität: 25 t/h Abfall oder EBS Spezifische Kosten: Betriebsmittel / spezifische Kosten Einheit Preis elektrische Energie [ /kwh] 0,06 Branntkalk (93,5 Ma.-% CaO) [ /t] 90 Kalkhydrat (95 Ma.-% Ca(OH) 2 ) [ /t] 95 Natriumhydrogencarbonat (NaHCO 3 ) [ /t] 195 Herdofenkoks (HOK) [ /t] 480 Ammoniakwasser (25%ig) [ /t] 94 Natronlauge (50%ig) [ /t] 260 Wasser [ /t] 3 Druckluft (tr.) [ /m³ N ] 0,03 ND-Dampf (4 bar(a) / 143,6 C) [ /t] 15 Reststoffentsorgung [ /t] 110 Wirtschaftlichkeitsbetrachtung: