WELCOME TO PRESENTATION ON SUPERCRITICAL BOILER By OPERATION - PowerPoint PPT Presentation

WELCOME TO PRESENTATION ON SUPERCRITICAL BOILER By OPERATION TEAM APML,TIRODA 1

In Intr trod oduc ucti tion on to S o Sup uper ercri criti tical cal Tec echnolog nology What is Supercritical Pressure ? Critical point in water vapour cycle is a thermodynamic state where there is no clear distinction between liquid and gaseous state of water. Water reaches to this state at a critical pressure above 22.1 MPa and 374 o C . 2

Ra Rank nkin ine e Cycl cle e Subc ubcrit ritic ical al Unit Unit  1 - 2 > CEP work  2 - 3 > LP Heating  3 - 4 > BFP work  4 - 5 > HP Heating  5 – 6 > Eco, WW  6 – 7 > Superheating  7 – 8 > HPT Work  8 – 9 > Reheating  9 – 10 > IPT Work  10 – 11 > LPT Work  11 – 1 > Condensing 3

Ra Rank nkin ine e Cycl cle e Super upercriti critical cal Unit Unit  1 - 2 > CEP work  2 – 2s > Regeneration  2s - 3 > Boiler Superheating  3 – 4 > HPT expansion  4 – 5 > Reheating  5 – 6 > IPT & LPT Expansion  6 – 1 > Condenser Heat rejection 4

VAR ARIA IATION ION OF OF LA LATENT ENT H HEA EAT WIT ITH PR PRES ESSURE SURE Absolute Saturation Latent Heat Pressure Temperature (K J/Kg.) (Bar) ( o C) 50 264 1640 150 342 1004 200 366 592 221 374 0 5

De Depar artur ture e from om Nuc ucleat leate e Bo Boil ilin ing Nucleate boiling is a type of boiling that takes place when the surface temp is hotter than the saturated fluid temp by a certain amount but where heat flux is below the critical heat flux. Nucleate boiling occurs when the surface temperature is higher than the saturation temperature by between 4 0 C to 30 0 C. WATER DENSITY STEAM 175 224 PRESSURE(ksc) 6

Sup uper ercritical critical Bo Boiler ler Water er Wall l Rifle fle Tub ube e And nd Smo mooth th Tub ube 7

Natural tural Circulation culation Vs. s. On Once e Through ough Syst stem em 8

To HP 571 0 C To IP Turbine Turbine 569 0 C Mixer Header 534 0 C 423 0 C 526 0 C 462 0 C Separator FRH 473 0 C FSH Platen Heater LTSH From CRH Line 326 0 C 443 0 C LTRH 324 0 C NRV 283 0 C From FRS Line 280 0 C Economizer Economizer Phase 1 Phase 2 Boiler Bottom Ring Recirculation Pump Header

Fee eed d wat ater er co contr ntrol ol  In Drum type Boiler Feed water flow control by Three element controller  1.Drum level  2.Ms flow  3.Feed water flow.  Drum less Boiler Feed water control by  1.Load demand  2.Water/Fuel ratio(7:1)  3.OHD(Over heat degree) 10

Di Differe erenc nce e of of Sub ubcri criti tical cal(50 (500M 0MW) W) an and S d Sup uper ercri criti tical(6 cal(660 60MW) MW) 11

COMPAR ARISION SION OF OF SUP UPER CRITICAL ICAL & SUB UB CRITICAL CAL DESCRIPTION SUPERCRITICAL SUB-CRITICAL (660MW) (500MW) Once-thru=1 Circulation Ratio 1 Assisted Circulation=3-4 Natural circulation= 7-8 Three Element Control Feed Water Flow -Water to Fuel -Feed Water Flow Control Ratio -MS Flow (7:1) -Drum Level -OHDR(22-35 O C) -Load Demand Latent Heat Addition Nil Heat addition more Sp. Enthalpy Low More Sp. Coal consumption Low High Air flow, Dry flu gas loss Low High

Continue.. DESCRIPTION SUPERCRITICAL SUB-CRITICAL (660MW) (500MW) Coal & Ash handling Low High Pollution Low High Aux. Power Low More Consumption Overall Efficiency High Low (40-42%) (36-37%) Total heating Low High surface area Reqd (84439m 2 ) (71582m 2 ) Tube diameter Low High 13

Continue.. DESCRIPTION SUPERCRITICAL SUB-CRITICAL (660MW) (500MW) Material / Infrastructure Low High (Tonnage) 7502 MT 9200 MT Start up Time Less More Blow down loss Nil More Water Consumption Less More 14

Wat ater er Wall all De Desi sign gn 15

WATER ER WAL ALL ARR L ARRAN ANGEMENT GEMENT  Bottom spiral & top vertical tube furnace arrangement  Once through design feature is used for boiler water wall design  The supercritical water wall is exposed to the higher heat flux  Spiral tube wall design (wrapped around the unit) with high mass flow & velocity of steam/water mixture through each spiral  Higher mass flow improves heat transfer between the WW tube and the fluid at high heat flux. 16

SPIRAL RAL VS VS VERT ERTICAL ICAL WALL VERTICAL WALL SPIRAL WALL  Less ash deposition on wall  More ash deposition  Less mass flow  More fluid mass flow  More number of tubes  Less number of tubes  More boiler height for same  Less boiler height capacity  Uniform heat transfer and  No uniform heating of tubes and uniform heating of WW tubes heat transfer in all tubes of WW 17

Fur urnace nace Arrang rrangemen ement SPIRAL TYPE VERTICAL TYPE 18

Sup uper ercritical critical Sliding iding Press essure ure Bo Boiler ler Water er Wall l De Desi sign gn Compa parison rison of Ver ertic tical al Wall l and nd Spi piral ral Wall 19

20

As Ash ac accu cumulat mulation ion on on wal alls Vertical water walls Spiral water walls 21

Super Critical Boiler Materials 22

Advanced Supercritical Tube Materials (300 bar/600 0 c/620 0 c) 23

Mat ater eria ial l Com omparis arison on Description 660 MW 500 MW Structural Steel Alloy Steel Carbon Steel Water wall T22 Carbon Steel SH Coil T23, T91 T11, T22 T91,Super 304 RH Coil H T22, T91,T11 LTSH T12 T11 Economizer SA106-C Carbon Steel Welding Joints (Pressure Parts) 42,000 Nos 24,000 Nos 24

Steam Water Cycle Chemistry Controls 25

S. Parameter Sub Critical Super Critical No. Type of Boiler LP and HP dosing. Or No HP dosing   water All Volatile Treatment Combined water treatment (CWT).   1 treatment (Hydrazine + Ammonia) Silica < 20 ppb in feed water and steam, Standard value <15 ppb in the cycle 2 < 250 ppb in boiler drum Expected value <10 ppb in the cycle 9.0 – 9.6 for AVT(All volatile treatment) pH 9.0 - 9.5 for feed, steam & 8.0 – 9.0 for CWT(Combine water condensate, 3 9.0 – 10.0 for Boiler drum treatment) Dissolved < 7 ppb for feed. < 7 ppb for feed in case of AVT 4 30 – 150 ppb for feed in case of CWT Oxygen (DO) Cation (H + ) <0.20 µ S/cm in the feed & steam Standard value <0.15 µ S /cm in the cycle Conductivity cycle Expected value- <0.10 µ S /cm in the cycle 5 (CPU) CPU is optional CPU is essential for 100% flow. 6 Silica and TDS By maintaining feed water quality Blow down possible till separators are control and functioning (upto 30% load). 7 By operating CBD 26

Advantages of SC Technology I ) Higher cycle efficiency means Primarily – less fuel consumption – less per MW infrastructure investments – less emission – less auxiliary power consumption – less water consumption II ) Operational flexibility – Better temp. control and load change flexibility – Shorter start-up time – More suitable for widely variable pressure operation 27

EC ECONOMY NOMY Higher Efficiency ( η %) • Less fuel input. • Low capacity fuel handling system. • Low capacity ash handling system. • Less Emissions.  Approximate improvement in Cycle Efficiency Pressure increase : 0.005 % per bar Temp increase : 0.011 % per deg K 28

Increase crease of Cycl cle e Efficiency ciency due e to Steam Par Paramet ameter ers Increase of efficiency [%] 10 6,77 9 5,79 5,74 8 4,81 7 3,74 4,26 6 3,44 2,76 5 3,37 4 2,64 1,47 3 2,42 600 / 620 2 1,78 0,75 580 / 600 1 566 / 566 0 0 538 / 566 300 241 HP / RH outlet temperature [deg. C] Pressure [bar] 175 538 / 538 29

Sub ub. vs. Sup uper ercriti critical cal Cycle cle Impact act on Em Emissions sions Subcritical Supercritical 34 - 37 Plant Efficiency, %* 37 - 41 Plant Efficiency, Btu / kw-hr 10,000 - 9,200 9,200 - 8,300 34% 37% 41% Plant Efficiency, % Base Base-8% Base-17% Fuel Consumption/Total Emissions including CO 2 * HHV Basis 30

Chall lleng enges es of sup uper ercrit critical ical tec echnolo nology  Water chemistry is more stringent in super critical once through boiler.  Metallurgical Challenges  More complex in erection due to spiral water wall.  More feed pump power is required due to more friction losses in spiral water wall.  Maintenance of tube leakage is difficult due to complex design of water wall.  Ash sticking tendency is more in spiral water wall in comparison of vertical wall . 31

TH THANK ANK YOU OU