on the use of rotary heat exchangers as a novel

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ON THE USE OF ROTARY HEAT EXCHANGERS AS A NOVEL INTEGRATION OPTION FOR HEAT AND WATER MANAGEMENT IN EXHAUST GAS RECYCLING GAS TURBINE PLANTS Laura Herraiz a * , , Dougal Hogg b , Jim Cooper b , Jon Gibbins a , Mathieu Lucquiaud a a The University of Edinburgh, School of Engineering, The Kings Buildings, Edinburgh EH9 3JL, United Kingdom b Howden Global, Old Govan, Renfrew, PA4 8XJ, United Kingdom * Corresponding autor: [email protected] +44 (0) 7587161599 An hybrid cooling system reduces cooling water consumpPon by around 60% compared to a configuraFon with a single DCC. A dry cooling system using ambient air instead of water as the cooling fluid shows good performance. Stack temperature in excess of 70ºC and a temperature around 43ºC at the inlet of the absorber are reached in an airfired CCGT. As the recirculaPon raPo increases, the CO 2 depleted flow rate decrease, which results in a reducPon of the overall cooling capacity at constant heaPng surface area. The buoyancy of the flue gas entering the stack is higher. A dry cooling system using a single gas/gas/air heater resulted in a more compact design, with lower booster fan power consumpPon and smaller foot print. ACKNOWLEDGEMENTS: CONFIGURATIONS: 1. Wet cooling system: direct contact cooler The gas is brought into direct contact with process water in a counter current configuraFon in a packed bed. Cooling water in the heat exchanger is provided by the primary plant cooling system. 2. Hybrid cooling system: gas/gas heater and direct contact cooler A gas/gas heater transfers heat from the EFG leaving the HRSG into the CO 2 depleted gas, exiFng the water wash secFon at the top of the absorber. Further cooling is, however, necessary for the untreated gas stream in a direct contact cooler. 3. Dry cooling system: gas/gas heater and air/gas heater The direct contact cooler is replaced by two consecuFve regeneraFve heaters in a dry cooling system. Ambient air is used as cooling fluid in the air/gas rotary heater. 4. Dry cooling system: gas/gas/air heater in a trisector configuraPon The two consecuFve rotary heat exchangers are replaced by a single heater with a trisector arrangement. A similar thermal performance analysis is also conducted for a NGCC plant with EGR, at different recirculaFon raFos for the same design of rotary heaters as in the airfired case. Technology opFons with gas/gas rotary heat exchangers are invesFgated for the water and heat management in the integraFon of Combined Cycle Gas Turbines (CCGT) plants with postcombusPon carbon capture (PCC), with and without exhaust gas recirculaFon (EGR). The aim is to replace the Direct Contact Cooler (DCC), typically used for aminebased scrubbing technology, with the consequent reducPon in the overall process water requirements and cooling water consumpPon. A range of configuraFons are examined for wet and dry cooling of the Exhaust Flue Gas (EFG) entering the absorber and reheat the CO 2 depleted gas leaving the water wash secFon at the top of the absorber before being released into the atmosphere through the stack of the plant. With EGR, the fracPon of the flue gas rediverted is cooled down before it is mixed with ambient air, as lower inlet temperature increase the gas turbine power output. Feasible heater configuraPon, dimensional and operaPonal parameters are selected to achieve a desired outlet temperature for the EFG and CO 2 depleted gas streams at the cold and hot end respecFvely, with a minimum leakage level and pressure drop. KEY REFERENCES: [1] InternaFonal Energy Agency of Greenhouse Gases, CO 2 Capture at Gas Fired Power Plants, 2012/8, July 2012. [2] Huizeling, E. and Van der Weijde, G., ROAD CCS nonconfidenFal FEED study report: special report for the Global Carbon Capture and Storage InsFtute, 2011. [3] Kigo, J.B and Stultz, S.C., Steam, its generaFon and use, EdiFon 41st.The Babcock and Wilcox Company, 1992, ISBN 0963457012. In regeneraPve heat exchangers heat is indirectly transferred by convecFon as a heat storage medium is periodically exposed to hot and cold fluid streams, in a counter current arrangement [3]. Larger specific surface area and smaller equivalent diameter , compared to recuperaFve heat exchangers. Fig.2. Cooling water, process water and cooling air mass flow required for each configuraFon, within the boundary limits, in an airfired GTCC plant and a GTCC plant with EGR (40% recirculaFon raFo), both with postcombusFon capture technology. Fig.3. Booster fan, air fan, cooling and process water pumps power consumpFon, in an airfired CCGT plant and a CCGT plant with EGR (40% recirculaFon raFo), both with postcombusFon capture technology. The EFG leaves the HRSG and needs to be cooled down unFl it reaches the saturaFon temperature at the inlet of the absorber [1,2]. Why? A low temperature enhances the absorpFon process by increasing the solvent capacity and the driving force for mass transfer. At the top of the absorber (water wash secFon), the CO 2 depleted gas stream is reheated in a dry stack design [1]. Why? in order to increase buoyancy forces and avoid plume visibility and corrosion due to water condensaFon in the stack. 1. INTRODUCTION AND MOTIVATION Fig.1 Example of a typical regeneraFve gas/gas rotary heater used in coal power plants [Courtesy of Howden]. 0 100 200 300 400 500 600 700 800 900 1000 DCC DCC (EGR 40%) GGH and DCC GGH and DCC (EGR 40%) GGH and AGH GGH and AGH (EGR 40%) GGAH GGAH (EGR 40%) Mass flow rate (kg/s) Cooling water mass flow Process water mass flow Cooling air mass flow DCC : direct contact cooler GGH and DCC : gas/gas heaer and direct contact cooler GGH and AGH : gas/gas heater and air/gas heater GGAH : gas/gas/air tri-sector heater 0.0 2.0 4.0 6.0 8.0 10.0 12.0 DCC (air fired) DCC (EGR 40 %) GGH and DCC (air fired) GGH and DCC (EGR 40%) GGH and AGH (air fired) GGH and AGH (EGR 40%) GGAH (air fired) GGAH (EGR 40%) Power (MW) Water pumps power consumption Air fan power consumption Booster fan power consumption 4. ENGINEERING ASSESSMENT A. Air fired CCGT plant with PCC B. EGR CCGT with PCC 2. ROTARY HEAT EXCHANGER TECHNOLOGY 3. NOVEL INTEGRATION OPTIONS FOR HEAT AND WATER MANAGEMENT IN CCGT WITH PCC Cooling and process water consumpPon Booster fan power consumpPon

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Page 1: ON THE USE OF ROTARY HEAT EXCHANGERS AS A NOVEL

ON  THE  USE  OF  ROTARY  HEAT  EXCHANGERS  AS  A  NOVEL    INTEGRATION  OPTION  FOR  HEAT  AND  WATER  MANAGEMENT    

IN  EXHAUST  GAS  RECYCLING  GAS  TURBINE  PLANTS  Laura  Herraiz  a  *,,  Dougal  Hogg  b,  Jim  Cooper  b,  Jon  Gibbins  a,  Mathieu  Lucquiaud  a    a  The  University  of  Edinburgh,  School  of  Engineering,  The  Kings  Buildings,  Edinburgh  EH9  3JL,  United  Kingdom  

b  Howden  Global,  Old  Govan,  Renfrew,  PA4  8XJ,  United  Kingdom  *  Corresponding  autor:  [email protected]    +44  (0)  7587161599  

•  An   hybrid   cooling   system   reduces   cooling   water  consumpPon  by  around  60%  compared  to  a  configuraFon  with  a  single  DCC.  

•  A  dry  cooling  system  using  ambient  air   instead  of  water  as  the  cooling  fluid  shows  good  performance.    

•  Stack   temperature   in   excess   of   70ºC   and   a   temperature  around  43ºC  at  the  inlet  of  the  absorber  are  reached  in  an  air-­‐fired  CCGT.    

•  As   the   recirculaPon   raPo   increases,   the   CO2-­‐depleted    flow   rate   decrease,   which   results   in   a   reducPon   of   the  overall  cooling  capacity  at  constant  heaPng  surface  area.  The  buoyancy  of  the  flue  gas  entering  the  stack  is  higher.    

•  A   dry   cooling   system   using   a   single   gas/gas/air   heater  resulted   in   a  more   compact   design,  with   lower   booster  fan  power  consumpPon  and  smaller  foot  print.  

ACKNOWLEDGEMENTS:    

CONFIGURATIONS:  1.    Wet  cooling  system:  direct  contact  cooler  The   gas   is   brought   into   direct   contact   with   process   water   in   a  counter  current  configuraFon  in  a  packed  bed.  Cooling  water  in  the  heat  exchanger  is  provided  by  the  primary  plant  cooling  system.  

2.    Hybrid  cooling  system:  gas/gas  heater  and  direct  contact  cooler  A  gas/gas  heater  transfers  heat  from  the  EFG  leaving  the  HRSG  into  the  CO2-­‐depleted  gas,   exiFng   the  water  wash   secFon  at   the   top  of  the   absorber.   Further   cooling   is,   however,   necessary   for   the  untreated  gas  stream  in  a  direct  contact  cooler.    

3.    Dry  cooling  system:  gas/gas  heater  and  air/gas  heater    The   direct   contact   cooler   is   replaced   by   two   consecuFve  regeneraFve  heaters  in  a  dry  cooling  system.  Ambient  air  is  used  as  cooling  fluid  in  the  air/gas  rotary  heater.    

4.    Dry  cooling  system:  gas/gas/air  heater  in  a  tri-­‐sector  configuraPon  The  two  consecuFve  rotary  heat  exchangers  are  replaced  by  a  single  heater  with  a  tri-­‐sector  arrangement.      

A   similar   thermal   performance   analysis   is   also   conducted   for   a  NGCC  plant  with  EGR,  at  different  recirculaFon  raFos  for  the  same  design  of  rotary  heaters  as  in  the  air-­‐fired  case.    

•  Technology  opFons  with  gas/gas  rotary  heat  exchangers  are  invesFgated  for  the  water  and   heat   management   in   the   integraFon   of   Combined   Cycle   Gas   Turbines   (CCGT)  plants   with   post-­‐combusPon   carbon   capture   (PCC),   with   and   without   exhaust   gas  recirculaFon  (EGR).    

•  The  aim  is  to  replace  the  Direct  Contact  Cooler  (DCC),  typically  used  for  amine-­‐based  scrubbing   technology,   with   the   consequent   reducPon   in   the   overall   process   water  requirements  and  cooling  water  consumpPon.  

•  A   range  of   configuraFons  are  examined   for  wet  and  dry   cooling  of   the  Exhaust   Flue  Gas   (EFG)  entering   the   absorber  and   reheat   the  CO2-­‐depleted   gas   leaving   the  water  wash   secFon   at   the   top   of   the   absorber   before   being   released   into   the   atmosphere  through  the  stack  of  the  plant.  

•  With  EGR,   the   fracPon  of   the  flue  gas   re-­‐diverted   is   cooled  down  before   it   is  mixed  with  ambient  air,  as  lower  inlet  temperature  increase  the  gas  turbine  power  output.  

•  Feasible   heater   configuraPon,   dimensional  and   operaPonal   parameters   are   selected   to  achieve  a  desired  outlet   temperature   for   the  EFG  and  CO2-­‐depleted  gas  streams  at  the  cold  and   hot   end   respecFvely,   with   a   minimum  leakage  level  and  pressure  drop.    

KEY    REFERENCES:  [1]  InternaFonal  Energy  Agency  of  Greenhouse  Gases,  CO2  Capture  at  Gas  Fired  Power  Plants,  2012/8,  July  2012.    [2]  Huizeling,  E.  and  Van  der  Weijde,  G.,  ROAD  CCS  non-­‐confidenFal  FEED  study  report:  special  report  for  the  Global  Carbon  Capture  and  Storage  InsFtute,  2011.    [3]  Kigo,  J.B  and  Stultz,  S.C.,  Steam,  its  generaFon  and  use,  EdiFon  41st.The  Babcock  and  Wilcox  Company,  1992,  ISBN  0-­‐9634570-­‐1-­‐2.  

•  In   regeneraPve   heat   exchangers   heat   is  indirectly  transferred  by  convecFon  as  a  heat  storage   medium   is   periodically   exposed   to  hot   and   cold   fluid   streams,   in   a   counter  current  arrangement  [3].    

•  Larger   specific   surface   area   and   smaller  equivalent   diameter ,   compared   to  recuperaFve  heat  exchangers.    

Fig.2.  Cooling  water,  process  water  and  cooling  air  mass  flow  required  for  each  configuraFon,  within  the  boundary   limits,   in  an  air-­‐fired  GTCC  plant   and     a  GTCC  plant  with   EGR   (40%   recirculaFon   raFo),   both  with  post-­‐combusFon  capture  technology.  

Fig.3.  Booster  fan,  air  fan,  cooling  and  process  water  pumps  power  consumpFon,  in  an  air-­‐fired  CCGT  plant  and    a  CCGT  plant  with  EGR  (40%  recirculaFon  raFo),  both  with  post-­‐combusFon  capture  technology.  

 The  EFG  leaves  the  HRSG  and  needs  to  be  cooled  down  unFl  it  reaches  the  saturaFon  temperature  at  the  inlet  of  the  absorber  [1,2].    Why?   A   low   temperature   enhances   the   absorpFon   process   by  increasing   the   solvent   capacity   and   the   driving   force   for   mass  transfer.  

                At   the   top   of   the   absorber   (water  wash   secFon),   the  CO2-­‐depleted  gas  stream  is  reheated  in  a  dry  stack  design  [1].  Why?  in  order  to  increase  buoyancy  forces  and  avoid  plume  visibility  and  corrosion  due  to  water  condensaFon  in  the  stack.    

1.  INTRODUCTION  AND  MOTIVATION  

Fig.1  Example  of  a  typical  regeneraFve  gas/gas  rotary  heater  used  in  coal  power  plants  [Courtesy  of  Howden].  

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DCC DCC (EGR 40%)

GGH and DCC

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DCC : direct contact cooler GGH and DCC : gas/gas heaer and direct contact cooler GGH and AGH : gas/gas heater and air/gas heater GGAH : gas/gas/air tri-sector heater

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Water pumps power consumption Air fan power consumption Booster fan power consumption

4.  ENGINEERING  ASSESSMENT  

A.  Air  -­‐  fired  CCGT  plant  with  PCC  

B.  EGR  -­‐  CCGT  with  PCC      

2.  ROTARY  HEAT  EXCHANGER  TECHNOLOGY    

3.  NOVEL  INTEGRATION  OPTIONS  FOR  HEAT  AND  WATER  MANAGEMENT  IN  CCGT  WITH  PCC  

Cooling  and  process  water  consumpPon   Booster  fan  power  consumpPon