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Circulating Fluidized Bed Boilers Experience, Capabilities & Performance.

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Presentation on theme: "Circulating Fluidized Bed Boilers Experience, Capabilities & Performance."— Presentation transcript:

1 Circulating Fluidized Bed Boilers Experience, Capabilities & Performance

2 © Metso Automation Inc Title/Author Date 2 Fluidized Bed Combustion (FBC) technology…achieved through efforts of government initiatives in US and Europe Applied to small and mid-size industrial and utility plants… Why CFB? - Wide range of coals & heating values - Opportunity fuels (biomass) - Hard-to-Burn fuels (petroleum coke, tires) - Excellent emission performance - Minimizes DeSOx / DeNOx systems CFB has reached utility scale - Sizes over 300 MW e in operation MW e under construction Control strategies perfected over 25 years of collaboration between Metso Automation and Kvaerner Power (now Metso Power)

3 © Metso Automation Inc Title/Author Date 3 Metso Automation FBC Experience – over 100 units…up to 460 MW e Unit Size MWe Lagizsa Xia Lang Tan 1 &2 Alholmens Xin Jian Si 1 & 2 Scrubgrass Yi Bin Rauhaladati Mt Poso Control systems on over 300,000 MW worldwide.

4 © Metso Automation Inc Title/Author Date 4 Circulating Fluidized Bed Combustion (CFBC) technology recognized as a competitor to pulverized coal firing… Demand is driven by: Local availability of low cost fuel e.g. gob, culm, anthracite Ability to capture harmful emissions in the furnace Ability to burn a combination of fuels with varying heating values, ash content and moisture content Low operating cost

5 © Metso Automation Inc Title/Author Date 5 A notable example of utility sized CFBC - Alholmens, Finland … worlds largest single bio-fired CFBC boiler Output: 240MWe plus + 165MW of process steam (1.5 millions #/hr) Fuel: bark, wood chips, recycled paper & plastic, peat, coal Single CFBC boiler from Metso Power

6 © Metso Automation Inc Title/Author Date 6 Alholmens Control Room

7 © Metso Automation Inc Title/Author Date 7 Metso Automation System for Alholmens System functions: Boiler Control Burner Management Information Management Energy Management Fuel Handling Information Management System Performance calcs – loss method & input output method, fuel heating value Condition monitoring – boiler, turbine and auxiliaries Emission monitoring – CEMS (European) Boiler & turbine life – stress calculations 10,000 point process historian – DNAreplay analysis 20,000 point event historian – DNAalarm analysis

8 © Metso Automation Inc Title/Author Date 8 Another notable installation - Narva, Estonia Balti Elektrijaam 2 Foster Wheeler CFB Boilers 215 MWe / lb/h,1842/348 PSI 995/995 F Fuel: Oil shale District heating 160 MWth Eesti Elektrijaam 2 Foster Wheeler CFB Boilers 215 MWe / lb/h,1842/348 PSI 995/995 F Fuel: Oil shale

9 © Metso Automation Inc Title/Author Date 9 Xiao Long Tan 2X300 MW CFB…Yunnan, PRC Largest CFB in China Owner: Guodian IPP Commercial operation: 2006 Fuel: Lignite Boiler: Shanghai Boiler Works (Licensee of CE Alstom) Controls: Metso Automation Yunnan Xiao Long Tan Power Plant

10 © Metso Automation Inc Title/Author Date 10 Lagizsa, Poland… worlds first supercritical CFB Single Foster Wheeler CFBC Unit size 460 MW Fuel: anthracite Pressure: 3988 PSIA Temperature: 1040°F Efficiency: 45.3% Startup: 2007/08

11 © Metso Automation Inc Title/Author Date 11 Lagisza – worlds first supercritical CFB Emissions per EU directive: SO lb/mbtu NO x 0.16 lb/mbtu CO 0.16 lb/mbtu Dust lb/mbtu Without DeSOx or DeNOx equipment

12 © Metso Automation Inc Title/Author Date 12

13 Circulating Fluidized Bed Boilers Unique Issues and Challenges

14 © Metso Automation Inc Title/Author Date 14 Typical CFB plant with cyclone separator…

15 © Metso Automation Inc Title/Author Date 15 FBC Issues and challenges… Disturbances are caused by… Low quality fuels with varying heating values Multiple fuel firing with varying mixture and moisture Load demand requirements from steam host and/or generation requires fast response and greater turndown The consequences… Higher emissions Lower efficiency Imbalance between demand and supply All lead to higher operating costs!

16 © Metso Automation Inc Title/Author Date 16 Objectives dependent upon only a few controlled variables… NO x SO 2 T T O 2 CO T, p dT F, P, TT T Objectives... lower emissions higher efficiency process parameters within permitted limits easy operation automatic control throughout entire load range can be achieved... by controlling... fuel feed combustion air air distribution limestone injection by controlling... fuel feed combustion air air distribution limestone injection The challenge… only a relatively few controlled variables to effect change

17 Circulating Fluidized Bed Boilers Control strategies to meet objectives…

18 © Metso Automation Inc Title/Author Date 18 What control strategies are required to meet overall objectives? 1. Coordinate boiler with turbine - Match generation to demand – AGC capability to trade in energy market - Advanced Model Predictive Control (MPC) – provides correct demand to turbine and boiler under all conditions - Match boiler inputs with turbine energy requirement – maximize efficiency 2. Compute and control true heat release - Detect changes in fuel heating value – maintain constant steaming rate - Totalize heat release from all sources – maintain constant overall fuel flow - Maintain proper fuel air ratio over entire load range – maximize efficiency 3. Optimize bed/furnace temperature - Maintain temperature within operating range - lower limestone usage - Maximize sulfur calcium association – lower SOx emissions - Lower overall combustion temperature – lower NOx emissions

19 © Metso Automation Inc Title/Author Date 19 Typical CFBC power boiler control system… Requires the addition of smart control strategies… Coordinate front end with highly responsive generation control - Maintain generation equal to demand under all conditions Compute and control heat release from all fuels being burned - Maintain constant boiler output under all conditions Compute and control bed temperature - Lower emissions and limestone usage

20 Circulating Fluidized Bed Boilers Advanced Control Strategy 1… Coordinated Control

21 © Metso Automation Inc Title/Author Date 21 Let us not forget the main purpose of this plant… generate electricity Must control generation to demand Must provide AGC capability Must operate at maximum rate of change Must protect the unit when equipment is not performing at optimal conditions

22 © Metso Automation Inc Title/Author Date 22 Strategy 1 - Coordinate boiler with turbine… proven coordinated front end with Model Predictive Control.

23 © Metso Automation Inc Title/Author Date 23 L H PID PI FIRST STAGE PRESSURE v AA Unit Demand Generation Control Inc.Dec. ADS A T Frequency Bias PI L MW Inc. Limit Dec. Limit Rate Limit Turbine Base Mode Position Demand to E-H-C Block Override Main Steam Pressure Set Point Boiler Demand Coordinated Mode T 11:47am Stop 11:07pm Start Down 9:55am Start MEGAWATTS Closed loop generation control provides a linear response…

24 © Metso Automation Inc Title/Author Date 24 Unit 1 without new system (blue) Unit 2 with new system (Red) Fast accurate response to AGC commands..

25 © Metso Automation Inc Title/Author Date 25 Constraint coordinator protects unit… slows rate of change in the event equipment or process is not operating at optimum

26 Circulating Fluidized Bed Boilers Advanced Control Strategy 2… Fuel Power Compensator®

27 © Metso Automation Inc Title/Author Date 27 Strategy 2 - Advanced application to compute and control true heat release from all fuel sources and detect changes in heating value Fuel Power Compensator® – Computes true heat release and corrects fuel and airflow demand.

28 © Metso Automation Inc Title/Author Date 28 Fuel Power Compensator ® Calculation derived by back-calculating energy content of fuel – on-line and in real time –Heat balance calculation based upon steam, feedwater enthalpies and flow measurements –Oxygen consumption calculation Stabilizes combustion process during: –Normal operation –Fuel feed disturbance situations –Variations in fuel quality or mixture

29 © Metso Automation Inc Title/Author Date 29 Typical CFB with Fuel Power Compensator®…

30 © Metso Automation Inc Title/Author Date 30 Fuel Power Compensator® developed in cooperation with Kvaerner… INTELLIGENT FUEL FEEDING AND CONTROL SYSTEM FOR HETEROGENEOUS FUELS Dr. Tero Joronen Research Scientist University of California Berkeley Metso Automation Lentokentänkatu 11, PO Box 237, FIN Tampere, Finland Tel: (0) Fax: (0) Jani Lehto Product Engineer Kvaerner Power Kelloportinkatu 1 D, PO Box 109, FIN Tampere, Finland Tel: (0) Fax: (0)

31 © Metso Automation Inc Title/Author Date 31 Increasing coal content in coal/bio-fuel mixture coal O2O2 steam flow Fuel Power Compensator®...performance at Alholmens 240MW CFB plant

32 Circulating Fluidized Bed Boilers Advanced Control Strategy 3… Combustion Optimizer

33 © Metso Automation Inc Title/Author Date 33 Bed/furnace temperature and fuel/air ratio directly effect emissions, performance, operating cost… and are a function of many different variables… SO 2 Hg NO X CO 2 Opacity CO Carbon in flyash Slagging Air heater fouling Process is difficult to model Process defined by multiple differential equations Process changes over time Feedforward / feedback control cannot deal with all scenarios Requires input based upon operating experience CaCo 3

34 © Metso Automation Inc Title/Author Date 34

35 © Metso Automation Inc Title/Author Date 35 Good bed management: Lower emissions Lower agglomeration Greater turndown Stable combustion Poor bed management: Higher emissions Forced outages Less stable combustion Higher agglomeration due to hot spots Bed material and temperature management:

36 © Metso Automation Inc Title/Author Date 36 An important reason to optimize bed temperature…it can cost you! Operating outside of the optimum temperature range can cost big bucks for extra limestone!

37 © Metso Automation Inc Title/Author Date 37 NO X formation vs temperature and nitrogen content of the fuel…

38 © Metso Automation Inc Title/Author Date 38 SNCR…Selective Non-catalytic Reduction is temperature sensitive Ammonia (NH 3 ) or urea (NH 2 2CO) sprayed into the flue gas in the presence of oxygen to produce N 2 Reaction produces water and urea in addition to CO 2 If temperature is too low the ammonia does not completely react with the NO 2 and causes ammonia to be released into the atmosphere … …called ammonia slip Requires precise furnace temperature control!

39 © Metso Automation Inc Title/Author Date 39 The best solution is to… Utilize all available process data Make calculations that describe and predict performance Incorporate operator know-how, expertise and intuition

40 © Metso Automation Inc Title/Author Date o C Bed temperature- fuzzyfication low normal high Fuzzy control is... used to control processes for which it is difficult to create mathematical models an advanced control method in which operator experience is utilized to develop (automatic) control algorithms, which are created linguistically (verbally) easy for operators to understand how the higher level, fuzzy controls work In power, cogeneration and energy-from-waste plants fuzzy control... is suitable for instance to optimize the operation of fluidized bed (and grate) boilers fuzzy logic control can be installed after the start-up of the plant to improve operation and solve problems Fuzzy logic for Fluidized Bed Boilers What, why...?

41 © Metso Automation Inc Title/Author Date 41 Rule base Control increase decrease cyclone temperatures bed temperatures NOxMeasurements Fuzzyfication C Presentation of linguistic variables bed-temperatures (membership functions) low normal high Defuzzyfication Fuzzy- Inferenz Advanced Controls Fuzzy logic for Fluidized Bed Boilers Control of primary/secondary air

42 © Metso Automation Inc Title/Author Date 42 Air flow / fuel power Setpoint for controller total air primary air secondary air Setpoint for controller total air primary air secondary air Correction coefficients fuel/air primary /secondary air secondary /tertiär air setpoint for O 2 -controller Correction coefficients fuel/air primary /secondary air secondary /tertiär air setpoint for O 2 -controller Corrections NO x SO 2 T T O 2 CO T, p dT F, P, TT T Calculation of fuel- power Fuzzy-logic Advanced Controls bed-temperature cyclone temperature total air O2/CO-Optimization Fuzzy-logic Fuzzy logic for Fluidized Bed Boilers Implementation

43 © Metso Automation Inc Title/Author Date 43 Tuning parameters fuel/air prim./sec. air lower/upper sec. air O 2 -controller setpoint fuel distribution Tuning parameters fuel/air prim./sec. air lower/upper sec. air O 2 -controller setpoint fuel distribution 1. Calculated variables fuel heating value oxygen consumption flue gas flow emissions mg/MJ 1. Calculated variables fuel heating value oxygen consumption flue gas flow emissions mg/MJ NO x SO 2 T T O 2 CO T, p dT F, P, TT T 3. Operator know-how 2. Measurements (control/ Compensation/ Filtering / Recipe) Fuzzy-logic Advanced Controls Fuzzy logic for Fluidized Bed Boilers Principal structure...

44 © Metso Automation Inc Title/Author Date 44 Bed Temperature before (upper chart) and after optimization (lower Chart)…

45 © Metso Automation Inc Title/Author Date 45 Typical CFB with Combustion Optimizer

46 © Metso Automation Inc Title/Author Date 46 A performance story… Alholmens availability On-line (%)Forced Outages (hrs)Avail (%) none None100

47 © Metso Automation Inc Title/Author Date 47 Metsos goal... To be the outstanding supplier for environmentally driven energy solutions. Over 100 FBC boilers under control Over 400,000 MW under control Fast responsive generation control Advanced control applications for FBC boilers Fuel Power Compensator® computes true Heat Release Fuzzy logic controller for bed temperature optimization


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