PLANT PERFORMANCE IMPROVEMENTS BY ENHANCED COMBUSTION THROUGH LASER-BASED OPTIMIZATION

Transcription

1 PLANT PERFORMANCE IMPROVEMENTS BY ENHANCED COMBUSTION THROUGH LASER-BASED OPTIMIZATION Dr. Sudha Thavamani Siemens Energy, Instrumentatin, Cntrls & Electrical, U.S.A Dr. Matthias Behmann Siemens Energy, Instrumentatin, Cntrls & Electrical, Germany Till Spaeth Siemens Energy, Instrumentatin, Cntrls & Electrical, Germany Keywrds: Cmbustin Optimizatin, Laser Measurements, Biler Efficiency, Tangential Fired bilers, Siemens Pwer Plant Autmatin SPPA-P3000 ABSTRACT The pwer generatin cmpanies have t seek mre superir and sphisticated technlgies in rder t gain an edge n their cmpetitrs wing t cntinually rising demands by envirnmental and gvernmental authrities and cnsumers. Intelligent Cmbustin Optimizatin is a prven methdlgy t accmplish plant perfrmance imprvements, biler efficiency increase and reductin in emissins. The Siemens SPPA-P3000 Cmbustin Optimizatin slutins allw plant peratrs t achieve these bjectives. The purpse f the paper is t describe in detail the perfrmance imprvements achieved by using Siemens SPPA-P3000 Cmbustin Optimizer at Unit 4 f Huaneng Rizha Pwer Plant, P. R. China. This unit is a 660 MW tangentially-fired, supercritical biler. T balance the cmbustin better, a clsed-lp ptimizatin is delivered by manipulating fuel and air levels with the help f laser measurements which prvide the key cmbustin cmpnents O 2, CO, H 2 O and temperature simultaneusly, directly in the furnace. Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

2 INTRODUCTION In the current market cnditins, steam pwer plants must always be run at the mst prfitable perating pint. This primarily demands a high degree f flexibility, high efficiency, high availability and lw emissins. The Siemens Pwer Plant Autmatin Prcess Optimizatin (SPPA-P3000) slutins allw plant peratrs t achieve these bjectives. One f the mst cst-effective means fr imprving the biler efficiency is by applying the primary measures based n ptimized cmbustin adjustments. Hwever, this ptimizatin apprach is usually restricted by the pwer plant peratr s limited knwledge f actual cmbustin cnditins. These uncertainties abut the actual cmbustin prcess leads t situatins in which peratrs keep mst f biler settings cnstant, althugh cnsiderable variatins ccur with respect t fuel prperties, fuel flw rate imbalances, lad range r air flw disturbances. The insufficient mnitring and cntrl means that, in general, the peratin f the bilers is based n the use f certain cmbinatins f glbal r indirect variables, derived either frm the recmmendatins f the biler manufacturer r frm the accumulated experience f the peratrs f the specific plant. These ften have mre t d with peratinal stability and histrical inertia, i.e. fllwing custmary practices, than with true ptimum perating cnditins. The Cmbustin Optimizer prvides clsed-lp ptimizatin f fuel and air mixing by manipulating fuel and air levels t balance cmbustin in the furnace. The imprtant benefits f the ptimizer include greater cmbustin efficiency and cnsequently lwer fuel csts, reliable cmbustin f supplementary fuel, reliable cmbustin f a wider range f cal types, etc. The Cmbustin Optimizer is sftware based slutins and needs n mdificatins t mechanical equipment. This slutin is cmprised f Cmbustin Optimizer mdules fr laser-based measuring technlgy, distributin calculatin based n Cmputer-Aided Tmgraphy (CAT) prcedure and Cmbustin Optimizatin Cntrls as shwn in Figure 1. The cmbustin cntrller is cmpletely integrated tgether with the included spectrscpy-based in-furnace measurements frm Zl Technlgies ZlBOSS system. Figure 1 Cmbustin Optimizer Mdule Interactins The laser-based measurement system maps the cncentratin f in-furnace CO, O 2, H 2 O and temperature simultaneusly in real time and directly in the furnace as shwn in Figure 2. Laser Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

3 transmitters and receivers are arranged utside the biler s that a grid f laser beams criss-crsses the furnace. Each path f the X by X laser grid measures an average value fr temperature, O 2, H 2 O, and CO simultaneusly, and tgether, the paths are used t create a tmgraphic image f this plane in the biler, which is als displayed t the peratrs directly in the cntrl rm. Figure 2 Laser based Measurement System The bjective f the paper is t describe in detail the perfrmance imprvements achieved by using the Cmbustin Optimizer at Unit 4 f Huaneng Rizha Pwer Plant, P. R. China. RIZHAO POWER PLANT UNIT 4 BOILER DESCRIPTION Unit 4 at Rizha Pwer Plant is lcated in Rizha City, Shandng Prvince in P.R. f China. It is a 660 MW tangentially fired, supercritical biler. The biler is a nce thrugh biler with single furnace cavity, single reheat, balanced draft, semi-utdr, dry ash extractin. It belngs t type biler with whle steel frame verhung cnstructin. Tw ljungstrm tri-sectr regenerative air preheaters are installed in the biler back-end. Fuel used by the biler is sft cal. There are six cal feeders and mills. A cyclne classifier is used at the cal mills. There are six burner levels with 4 burners at each level. The direct flw burner at every crner frms the tangential firing. Six layers f cal nzzles surrunded by fuel air (bundary air) are installed in the windbx. SOFA (Separated OFA) nzzles installed in the upper part f the windbx include five layers f hrizntally swinging nzzles. There are 25 secndary air valves including bundary air f cal nzzles that are cntrlled individually by pneumatic drives at every biler crner and layer. Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

4 COMBUSTION OPTIMIZATION PROJECT EXECUTION The cmbustin ptimizatin prject was executed in the year 2011 with fur majr steps as shwn in the Figure The first step was the installatin f laser measurement grids inside the biler. 2. The secnd step was t carry ut the parametric testing based n the cnditins f the biler. This was fllwed by the deductins and analysis f the spatial distributins. 3. Based n bservatins and inferences f step 2 abve, decisin n the required cntrlled variables fr the clsed lp cntrls engineering was made, which was the third majr step f the prject 4. The furth step was t integrate and cmmissin the cmbustin ptimizatin cntrls in the existing I&C system. Figure 3 Cmbustin Optimizatin Prject Executin in 2011 at Rizha Pwer Plant. COMBUSTION OPTIMIZER HARDWARE AND SOFTWARE Hardware Cnfiguratin The functins f the Cmbustin Optimizer mdules ran n a small SPPA-T3000 I&C system. The system is cmprised, as shwn in Figure 4, f the standard cmpnents: Technlgy server, e.g. fr archiving and ptimizatin Thin Client with sftware fr CAT display Standard interface t existing DCS Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

5 Figure 4 Optimizer System Mdules The hardware cnfiguratin f the Cmbustin Optimizer at Rizha Pwer Plant s Unit 4 is shwn in Figure 5. The Laser Measurement System was cnnected t the Technlgy Server thrugh OPC via TCP/IP. There was als a Thin Client cnnected t the Technlgy Server. The Technlgy Server was cnnected t the Fxbr DCS via Mdbus. This permits the availability f measured data frm the existing DCS, such as cal and air flws r CO and NOx in the flue gas, t the cmbustin ptimizatin prcess. Figure 5 Optimizer Hardware Cnfiguratin Transfer f Signals between Cmbustin Optimizer and Fxbr DCS The basic blck diagram fr signal transfer between the Cmbustin Optimizer and Fxbr DCS is shwn in Figure 6. There was a watchdg signal available fr the cmmunicatin check between the ptimizer and the DCS. The prcess measurements frm the DCS were used fr cntrls calculatin in ptimizer. The ptimizer then used the prcess measurements frm the DCS alng with the laser measurements data frm the biler t calculate the ptimized values. These values were prvided as the setpint deltas which were additive bias values t the existing setpints in the DCS. This prvided the new setpints which were transferred t the basic underlying cntrls and t the field. Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

6 There were three safety checks in the DCS that every setpint delta change had t pass befre they became effective in the cntrls and biler prcess. The three safety checks were an Optimizer ON/OFF switch, rate limiter and min / max abslute limits. Figure 6 Signal Transfer between Cmbustin Optimizer and DCS PARAMETRIC TESTING OUTCOME During the parametric testing, the behavir f the biler was bserved by changing and adjusting individual secndary air, secndary auxiliary air and SOFA dampers. The utcme f the parametric testing and cmbustin analysis were Fireball was ften nt in the center f the biler which led t unbalanced heat transfer t water wall and heaters. This als increased the risk f slagging fr parts f the water wall. Nn-hmgeneus distributin f excess air in the biler which led t efficiency lss in regins with t much air and bad cmbustin in regins withut enugh air. O 2 setpint f 3.5% at full lad fr nrmal peratin with limited manual O 2 reductin pssibilites, due t the nn-hmgenius and cntinuusly changing cmbustin situatin in the biler. Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

7 COMBUSTION OPTIMIZATION CONTROLS CONCEPT Fireball Centering The bjective behind the fireball centering cntrl was t center the fireball fr unifrm cmbustin. The fireball was centered by using the secndary auxiliary air dampers. The reprted temperature values frm the laser measurements were used t calculate the current psitin f the fireball. A mdel was develped using the angle f secndary auxiliary air damper t determine the reactin f the fireball psitin and t determine the distance f the fireball frm the rigin. Using this infrmatin the cntrller then cmputes the secndary auxiliary air damper psitin delta fr each f the fur crners f the biler. O 2 Distributin Balancing The bjective behind the O 2 distributin balancing was t unifrmly spread the O 2 using the SOFA. The O 2 balancing was perfrmed by cntrlling the SOFA dampers. The O 2 distributins in the biler, determined frm the laser measurements, were used as cntrl inputs. A mdel was built based n weighted average fr O 2 measurements fr the individual fur crners f the biler. This mdel fr each crner determined the SOFA deltas prprtinal t the distributin f DCS damper demands fr level I thrugh level V. Cmbustin Balancing The bjective behind the cmbustin balancing was unifrm cmbustin based n a gd air t fuel rati. The cmbustin balancing was implemented using the secndary bundary air dampers. The temperature, O 2 and CO measurements frm the laser measurements were used as inputs fr cmbustin balancing cntrls. A biler mdel was develped using these inputs which was then used t reveal reactin required fr the secndary bundary air damper deltas. Excess O 2 Reductin The fireball centering, O 2 distributin and cmbustin balancing cntrls helped t allw the reductin f the excess O 2 fr increasing the biler efficiency. This additinal lgic using CO cncentratin was implemented t determine the O 2 setpint crrectin dependant n the actual cmbustin situatin in the biler. The CO values in the biler frm the laser measurements and the CO after biler frm the DCS were used t determine the rated CO cncentratin. The CO setpint t the integral cntrl was determined as a functin f the unit lad frm the DCS. The ptimizatin cntrller als has the lwer limit fr O 2 reductin which was based n the functin f unit lad and had an abslute lwer limit frm the O 2 setpint characteristics frm the DCS. Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

8 USER INTERFACE Operatr Interface in DCS The peratr interface in the DCS with the Cmbustin Optimizer is shwn in Figure 7. The ON/OFF switch fr the ptimizer was prvided in the DCS and the peratr has full cntrl f switching ON and OFF ptimizer. Figure 7 als shws the setpint deltas fr the SOFA fr all crners and fr all the levels between A and F layers, I and V layers respectively in the DCS HMI. The setpint deltas frm the ptimizer fr the secndary auxiliary air dampers and fr secndary bundary air dampers fr all furs crners and fr the layers between A and F, I and V was displayed in the DCS HMI as shwn in Figure 7. Figure 7 ON/OFF Switch and Cmbustin Optimizer Setpint deltas n DCS BOILER OPERATION IMPROVEMENTS WITH COMBUSTION OPTIMIZER Fireball centering fr better heat transfer With the Cmbustin Optimizatin cntrls in peratin, the fireball was centered t achieve imprved heat transfer, reduced slagging and imprved biler efficiency. Figure 8 shws the snapsht f temperature distributin withut and with the ptimizer cntrls. It can be seen that the fireball was nt centralized withut the ptimizer cntrls and was at the center with clsed lp ptimizatin. Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

9 Figure 8 Laser measurements prtraying Fireball psitin with and withut Optimizer Balanced O 2 distributin fr better cmbustin With the cmbustin ptimizatin cntrls in peratin, the O 2 distributin was balanced t achieve imprved cmbustin, reduced O 2 in the biler and imprved biler efficiency. Figure 9 shws the snapsht f O 2 distributin withut and with the ptimizer cntrls. The O 2 distributin was nt balanced withut the ptimizer cntrl and O 2 distributin is well balanced with the clsed lp cntrls. Figure 9 Laser measurements prtraying O 2 distributin with and withut Optimizer Reduced O 2 fr higher biler efficiency With the ptimizatin cntrls in peratin, reductin f cmbustin air was achieved after balancing the biler. An autmatic reductin f excess O 2 accrding t the actual cmbustin situatin was accmplished. With the ptimizer, reduced flue gas flw and less related heat lsses in the biler was attained. The cmbinatin f all the ther ptimizer cntrls alng with the O 2 reductin cntrls resulted in imprved biler efficiency. Figure 10 illustrates the O 2 reductin trend ver a perid f 3h50min at cnstant unit lad. The green clr trend shws the delta O 2 reductin calculated by the Cmbustin Optimizer. The vilet clr trend shws the O 2 reductin lwer limit. The O 2 setpint frm the peratr in the DCS is shwn as Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

10 light blue clr trend. The actual O 2 curve is shwn in red clr. The blue clr trend shws the reduced O 2 setpint. The CO setpint is shwn as light green clr. The rated actual CO frm DCS is shwn as flded grey clr. The rated actual CO frm the laser measurements is shwn as flded yellw clr. The black clr trend displays the rated actual CO used fr ptimizing the excess O 2 in the biler. It can be seen frm Figure 10 that the reductin in O 2 was achieved when the ptimizer was switched ON. Hwever, the attempt t reduce O 2 setpint within the first hur f the test withut the additinal measures f the ptimizer slutin t balance cmbustin failed. Figure 10 O 2 reductin trend Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

11 LASER MEASUREMENTS DISPLAY WITH AND WITHOUT OPTIMIZER Figure 11 demnstrates the snapsht f laser measurements withut the ptimizer switched ON. In this scenari, the fireball was nt centered in the temperature prfile and the O 2 distributin was nt balanced in the O 2 laser measurement prfile. Figure 11 Snapsht f Laser Measurements withut Cmbustin Optimizer Cntrls Figure 12 demnstrates the snapsht f laser measurements with the Cmbustin Optimizer switched ON. At this state, the fireball was well centered in the temperature prfile and the O 2 distributin is balanced in the O 2 laser measurement prfile. Figure 12 Snapsht f Laser Measurements with Cmbustin Optimizer Cntrls Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;

12 CONCLUSION The Cmbustin Optimizer was tested fr different plant cnditins like that f different unit lads, different cal etc. The principle benefits f using Cmbustin Optimizer at Rizha Pwer Plant were: Better centralizatin f the fireball Better O 2 distributin in biler Mre O 2 reductin based n the balanced cmbustin, nrmally the O 2 reductin is 0.7~1.1 Reduced auxiliary pwer, reduced cal cnsumptin and increased biler efficiency With the request f the management at the Rizha Pwer Plant, a third party evaluatin f biler efficiency imprvement achieved by Cmbustin Optimizer was administered by Xi an Thermal Pwer Research Institute C., Ltd. (TPRI). TPRI cnducted a biler efficiency test using GB standard methdlgy at full lad and at partial lad t cmpare the biler efficiency with Cmbustin Optimizer OFF and ON. Perfrmance imprvements attributed t cmbustin balancing but nt included in the TPRI biler efficiency calculatin such as lwer auxiliary pwer requirements (frm induced, frced and primary air fan lads) and increased steam enthalpy were als calculated using TPRI test data and ASME 4.1 standards. The Cmbustin Optimizer imprved the perfrmance by a ttal f 0.57% at full lad. A better balanced cmbustin was achieved permitting the excess O 2 t be reduced by 0.93% based n the DCS setpints. This resulted in the decrease f fan lads (induced/frced draft and primary air) which further diminished the auxiliary pwer requirements by 293 KW/hr r 0.05% f the lad. This reductin in auxiliary pwer led t the increase in the amunt f electricity available fr sale by the plant. Als, at full lad the steam enthalpy increased as Superheater and Reheater steam temperatures enhanced as a result f better cmbustin which increased 0.07% mre verall imprvement in steam turbine utput. In additin, NOx level was reduced by 14.4% as a result f lwer excess O 2 while the CO and LOI did nt materially change. REFERENCES 1. Biler Efficiency Calculatin via ASME PTC 4.1 Methd 2. GB Perfrmance Test Cde fr Utility Biler Distributed with permissin f Sudha Thavamani, Matthias Behmann and Till Spaeth by ISA 2012 Presented at ISA POWID 2012;