1-s2.0-S0360544212000783-main

8102019 1-s20-S0360544212000783-main

httpslidepdfcomreaderfull1-s20-s0360544212000783-main 18

8102019 1-s20-S0360544212000783-main


investigations focused on the integration of WTA drying in a futureGreek power plant with elevated steam parameters [16] Recentwork includes the examination of possible oxy-fuel con1047297gurationsfor future Greek power plants burning Greek dried lignite in termsof boiler and steam cycle optimisation [1718] It becomes apparentfrom the above references that all the previous work which can befound in the literature in the relevant topic focuses on the designand the technical aspects of the lignite pre-drying process and onits possible integration into a state of the art lignite power plantsteam cycle No relevant work can be found on the economicaspects of the particular technology which is considered beyondthe technical issues as the decisive factor for its further develop-ment and application In this sense the present work intends tocontribute in the study of the 1047297nancial feasibility of pre-driedlignite 1047297ring as a proposed technology for the next generation of lignite 1047297red power plants

The present work focuses on a state of the art Greek lignitepowerplant and the possibilities of its upgrade by the integration of the lignite pre-drying technology The economic impact of pre-drying is in detail assessed in the framework of the upcoming 3 d

allocation period of Kyoto protocol that will come into effect in2013 From this period and onwards no Green House Gas (GHG)

Allowances will be allocated by national authorities of EU MemberStates to European power plant operators This means that thewhole amount of required allowances according to produced CO2

emissions will be purchased in the international carbon exchangesThe electricity production cost will be signi1047297cantly affectedprimarily in the case of power plants with increased speci1047297c CO2

emissions Power plants 1047297ring low rank coals such as lignite will bemostly affected since the low heating value of their basic fuel andtheir lower plant ef 1047297ciency compared to hard coal power plantslead to higher CO2 emissions in comparison with other coal powerplants

Lignite pre-drying may play a key role in improving the tech-nological dif 1047297culties of power plants 1047297ring low rank coals to be1047297nancially competitive in the new era By the application of lignite

pre-drying technology considerable savings of CO2 emissions areachieved through the improvement of the net plant ef 1047297ciency rateThis increase is achieved

a) By the increase of boiler ef 1047297ciency rate due to the reducedboiler 1047298ue gas losses when 1047297ring higher rank fuels like pre-dried lignite

b) By the implementation of the drying process through using lowtemperature heat (from steam bleed) In this way the exergylosses during the drying process decrease compared to theconventional lignite drying case where hot 1047298ue gas withtemperature of about 1000 C is used as a heating medium

c) By the further utilisation of the vapour produced in the dryingprocess as a heating medium in the 1047297rst steps of feed waterpre-heating

2 Methodology

21 Thermal cycle calculations

In order to evaluate the effect of pre-drying on plant ef 1047297ciency

a steam cycle which is typical for the current state of the art Greekpower plants is taken into consideration The nominal electricpower is 590 MWe with one reheat steam cycle and seven waterpre-heaters with steam extraction from the steam turbine (ST) Thesuperheated steam parameters are 610 C 280 bar while thereheated parameters are 620 C 60 bar A detailed 1047298owsheetdiagram of the considered steam cycle is presented in Fig 1 Thefollowing cases were investigated in this con1047297guration

A Reference case no integration of 1047298uidised bed dryer in thesteam cycle

B 25 pre-dried lignite co-1047297ring case 1047298uidised bed dryer inte-grated in the steam cycle in order to cover the 25 of therequired thermal input

Fig 1 Flowsheet of the considered steam cycle including the intersections with the WTA dryer

M Agraniotis et al Energy 45 (2012) 134e141 135

8102019 1-s20-S0360544212000783-main


C 100 pre-dried lignite 1047297ring case 1047298uidised bed dryer inte-grated in the steam cycle in order to fully cover the plantrsquosthermal input

In all cases the thermal input into the boiler remains the sameThe pre-dried lignite produced in the 1047298uidised bed dryer hasa moisture content of 12 and a Net Calori1047297c Value of 1238 MJkgThe higher calori1047297c value compared to the one of raw lignite leadsto a decrease of the total fuel mass 1047298ow in the cases of pre-driedlignite utilisation A co-1047297ring share of 25e30 is consideredaccording to the literature as the maximum share that may beachieved in an existing boiler only by the installation of special drylignite burners and without the implementation of extensivemodi1047297cation in the furnace geometry A further increase of the co-1047297ring share would probably lead to material damages in the nearburner region due to the increased 1047298ame temperature and thecorresponding increased heat 1047298ux Further operational issueswhich could arise is slagging and fouling in the furnace membranewalls caused by the increased 1047298ame temperatures and increasedNOx emissionwhich would exceed the current legislative limits Allthese phenomena have been analysed in former pre-dried ligniteco-1047297ring investigations performed at a semi industrial scale 1047297ring

facility [19e21]For the further increase of the pre-dried lignite share to 100

a new furnace design is required which shall take into account thelower 1047298ue gas volume 1047298ow in the case of dry lignite 1047297ring and thehigher adiabatic 1047298ame temperature Hence this new steam boilergeneration to be designed for 100 pre-dried lignite 1047297ring willhave a smaller cross-section to keep 1047298ue gas temperature at thecurrent values and a higher furnace height in order to be able toabsorb the higher radiative heat 1047298ux without any overheating andmaterial damage

The required heat for the operation of the 1047298uidised bed dryer isobtained from a steam bleed between the medium pressure andthe low pressure ST The heat demand of the WTA dryer is calcu-lated based on a methodology developed in previous work [2122]

About 80 of the produced vapour during the drying process (1 bar105 C) is utilised in the low pressure feed water pre-heaters Incase B a fraction of the required steam bleeds in the low pressurewater pre-heaters is substituted by the produced vapour from thedrying process while in the full pre-dried lignite1047297ring case (case C)pre-heating is carried out only by the utilisation of the producedvapour from the WTA dryer The condensate of the evaporated coalis subsequently driven to water treatment step while thecondensate of the extracted steam bleed used as a heating mediumin the drying process returns to the plantrsquos watersteam cycle

The commercial thermal cycle calculation tool Gatecycle is usedin the analysis Since the de1047297nition of two different solid fuel inletsis not possible in the particular calculation tool an ldquoequivalent fuelrdquo

is used as input in the dry coal co-1047297ring case B which correspondsto the mass weightedmixture of raw and pre-dried lignite (Table1)

22 Economic evaluation

The WTA drying concept is 1047297nancially evaluated by usingeconomic indices Based on speci1047297c assumptions the electricityproduction cost is calculated for the reference and the pre-driedlignite utilisation cases It is calculated as the sum of thefollowing costs a) annualised investment cost b) fuel cost c) 1047297xedoperating and maintenance cost d) variable operating and main-tenance cost and e) costs for CO2 allowances The latter is regardedas variable cost The particular methodology for accounting CO2

allowancescosts is in accordance with the Greek legislation and theEuropean legislative framework [2324] By adopting the particularcalculation methodology the cost of CO2 is included in the calcu-lation of the electricity generation cost in order to account for theenvironmental performance of each power production technologyIn this way technologies which have a higheref 1047297ciency rate such asnatural gas combined cycle power plants are bene1047297ted and theirelectricity generation cost may become comparable to the cost of lignite power plants despite the higher fuel price

In order to have a projection of the electricity production costsof lignite power plants after the end of the second allocation periodin 2012 the costs of CO2 allowances are calculated according to themethod to be implemented from 2013 ie purchase of the totalamount of the plantrsquos annual CO2 emission allowances in theinternational carbon exchange markets

The detailed parameters used for the calculation of the elec-tricity generation cost are provided in Table 2 An overall CapitalExpenditure (CAPEX) of about 1900 VkW is taken into account inthe case of a new reference power plant Since WTA drying tech-nology is a newly developed process and only one industrialprototype is now in operation no fully reliable data considering theinvestment and the maintenance costs can be found Theannounced RWE budget of the overall WTA prototype project is

about 1047297fty million Euro Furthermore in a new power plant projectto be realised according to the 25 pre-dried lignite co-1047297ring caseconsiderable savings can be achieved through the correct dimen-sioning of the 1047298ue gas recirculation and milling and drying systemMore speci1047297c the 1047298ue gas recirculation ducts and the raw coal millsshould be designed for drying of a lignite quantity corresponding to75 of the total thermal input The rest 25 should be covered bythe WTA 1047298uidised system Based on literature data [11] and oncommunication with the developer of the particular pre-dryingtechnology the additional investment cost in the 25 co-1047297ringscenario is estimated to 35 MV This value is the end value usedand incorporates the additional costs for the new dryer minus thepotential savings by the new dimensioning of the 1047298ue gas

Table 1

Fuel analysis in the three examined cases

A B C

Raw lignite Equivalent fuel (25 co-1047297ring) Pre-dried lignite (100 co-1047297ring)

Proximate analysis Water wt (ar) 532 4794 1200Ash wt (ar) 160 1780 3009Volatiles wt (ar) 170 1891 3197Fixed C wt (ar) 138 1535 2595

Net Calori1047297c Value NCV kJkg (ar) 5443 6330 12380Ultimate analysis C wt (ar) 1782 1982 3351

H wt (ar) 144 160 271N wt (ar) 060 067 113O wt (ar) 1049 1167 1972S wt (ar) 045 050 085

M Agraniotis et al Energy 45 (2012) 134e141136

8102019 1-s20-S0360544212000783-main


recirculation and milling and drying system This corresponds toa relative increase of the CAPEX to about 5 compared to thereference case

Moreover in the 100 pre-dried lignite 1047297ring case theconventional raw coal milling and drying system through the fanbeater mills is fully omitted since four WTA dryers in paralleloperation will provide the required pulverised pre-dried ligniteinto the boiler In the pre-drying process raw coal milling takesplace in dedicated hammer mills before the drying step The lignitedust enters then the 1047298uidised bed drying facility and an optional

further milling step may be applied at the dryersoutlet according tothe speci1047297cations of the boiler in terms of the coal particle sizedistribution Stored pre-dried lignite is used during the start upprocess of the 1047298uidised bed dryer when no full capacity is reachedThe price of the described milling system is also included in thegiven CAPEX Due to the further expected savings by the economiesof scale reached in the 100 pre-drying concept the estimatedadditional investment cost is taken as double as the additionalinvestment cost of the 25 co-1047297ring case Thus a CAPEX increase of 10 compared to the reference is regarded for the 100 pre-driedlignite 1047297ring case In order to investigate the effect of the usedassumptions on the economic feasibility of the examined conceptsa dedicated sensitivity analysis is carried out in the last part of thepresent work

As far as the Operating and Maintenance (OampM) costs is con-cerned a value of 344 VkWe of installed power is taken intoaccount for the1047297xed costs and 10VMWh of produced electricity istaken into account for the variable OampM costs In the dry ligniteutilization cases the above 1047297gures are increased by 5 and 10accordingly The fuel costs are taken as 15 VGJ corresponding toabout 82 Vt A plant availability of 90 about 7800 h per year istaken into account in all examined cases A construction period of four years is taken into account for the power plant erection whilethe construction interest is 7 The total lifetime of the unit isconsidered to be 40 years Finally the price of CO2 allowances isinitially taken as 20 Vt The particular 1047297gure could be consideredas a high value compared with the CO2 allowances price level in the4th quarter of 2011 [25] Its is however supported by recent studies

in the literature [26e28] that the cost of CO2 allowances will beincreased up to the level of 20 Vt after 2013 and will stay at thislevel for a longer period In order to investigate the effect of the CO2

allowances price on the economic feasibility of the examined casesa sensitivity analysis is afterwards carried out on the variation of this price

The CO2 avoidance cost determination follows the calculation of the electricity production cost The CO2 avoidance cost (C avoid in VtCO2) is given by the following expression (Eq (1))

C avoid frac14

C CO2 C ref

emref emCO2

(1)

whereas C ref The electricity production cost of the plant in thereference state(VkWh) C CO2

The electricity production cost in the

pre-dried lignite utilisation case (V

kWh) emref The speci1047297

c CO2

emissions of the plant in the reference state (t CO2kWh) emCO2

The speci1047297c CO2 emissions of the plant in the pre-dried ligniteutilisation case (t CO2kWh)

A new electricity production cost is calculated in each pre-driedlignite utilisation case This cost is affected by a) the increasedannualised investment costs due to the WTA dryer installation b)the respective raw lignite savings achieved c) the additional 1047297xedoperating and maintenance costs due to the increasedCAPEX d) theadditional variable operating and maintenance costs

3 Results e discussion

31 Effect of pre-drying on plant ef 1047297ciency

The main results of the plant heat balance for the reference andthe pre-dried lignite utilisation cases are given in Tables 3 and 4

As far as calculation errors are concerned typical settings in theparticular thermal cycle calculation tool were followed Theconvergence error set out in the calculation tool was 001 forproperties values and 01 for system values such as the net plantef 1047297ciency rate Full converged solutions were achieved in less than

100 cycle iterationsA gradual decrease of the net electric power output is observedin the con1047297gurations with the installed pre-drying system This isreasoned by the increased steam extraction utilised for the opera-tion of the WTA dryer On the other hand the raw lignite savingachieved by the steam drying process counterbalances this loss of power output Hence the net ef 1047297ciency rate increases The netef 1047297ciency increase is 15 percentage points in the 25 co-1047297ring caseand 59 percentage points in the 100 dry lignite 1047297ring case

Due to the expected power output decrease compared toreference it is concluded that in case of a new project the inte-gration of the WTA dryer should be designed in parallel with thewhole power plant design process in order to assure the properdimensioning of the boiler the steam turbine and the balance of plant


The calculated electricity generation cost in all cases is pre-sented in Fig 2 It should be at 1047297rst noticed that a considerableincrease of the electricity production cost from about 40 VMWh to60 VMWh is expected to take place in the period after 2013 due tothe implementation of allowances trading Aged coal power plants1047297ring low rank coal might be therefore forced to shut down ordecrease their total operating hours in order to decrease theirexpenses for the purchase of CO2 allowances

As expected a short increase of the annualised investment costsand the 1047297xed and variable operating and maintenance costs is

observed in the pre-dried lignite utilisation cases On the other

Table 3

Overall results of the plant heat balance

Reference 25co-1047297ring

100 pre-driedlignite 1047297ring

P e_net MWe 586 583 556hnet 3957 4111 4542_msteamtotal kgs 4927 4980 5134_msteambleed to dryer kgs 0 297 1187_mraw coal to mills kgs 2722 2041 0_mraw coal to WTA dryer kgs 0 562 2250_mdry coal to WTA dryer kgs 0 299 1196_mvapor to preheaters kgs 0 211 844

Table 2

Economic parameters

Parameter Value Unit

CAPEX 1900 VkWFixed OampM 344 VkWVariable OampM 10 VMWhFuel 15 VGJCO2 allowances price 20 Vt

Operational hours 7800 HoursConstruction interest 6Investment lifetime 40 Years


8102019 1-s20-S0360544212000783-main


hand the achieved raw lignite savings through the plant ef 1047297ciencyincrease lead to a decrease of the fuel costs and the respective CO 2

allowances This counteracting tendency of the speci1047297c costs leadsto almost no decrease of the total electricity generation costs in the25 co-1047297ring case (6227 VMWh compared with 6267 VMWh inthe reference case) and to a clear decrease in the 100 dry coal1047297ring case (5996 VMWh compared with 6267 VMWh in thereference case) Hence by the implementation of the 100 pre-dried lignite 1047297ring technology a decrease of the total electricitygeneration cost will be possible based on the obtained fuel and CO2

emission savingsIn the calculation of the CO2 avoidance cost (Table 5) two

different 1047297gures are presented In the 1047297rst one the expenses for thepurchase of CO2 allowances are not included in the electricity

generation cost so that the present market situation is reproduced

The particular avoidance costs in this case indicates that the 100pre-dried lignite 1047297ring concept is a clearly favourable solutiontowards the reduction of the CO2 emissions in the new generationof lignite power plants since the calculated avoidance cost is077 Vt CO2 The 25 co-1047297ring concept is also a favourable optionfor the refurbishment of existing power plants The calculatedavoidance cost (1033 Vt CO2) although comparable with theaccording values of 4th quarter of 2011 is much lower than theestimated value after 2013 (20 Vt CO2) according to literaturewhich is also taken as reference When including the CO2 allow-ances cost in the overall cost calculation pre-drying becomesa bene1047297cial practise in both examined cases The 25 pre-dryingcase leads to negative avoidance costs ie to revenues of 967 VtCO2 while the 100 pre-drying case leads to negative CO 2 avoid-

ance costs ie to revenues of 1923V

t CO2

Table 4

Detailed results of the plant heat balance

Mass (kgs) Temperature (C) Pressure (kpa) Enthalpy (kJkg)

a) Reference caseWatersteam cycle

Feed water inlet to eco S72 4927 300 32728 1329Feed water outlet from eco S4 4927 335 32128 1514Steam outlet from evaporator S6 4927 418 30728 2487

Superheated steam outlet from SH S7 4927 610 29328 3482Cold reheated steam intlet to reheater S70 3968 372 6402 3094Hot reheated steam outlet from reheater S71 3968 620 6080 3704Low pressure steam after ST S27 3082 35 6 2256Condensate S20 3082 35 6 146Extracted medium pressure steam to dryer S112 0 e e e

Vapour from dryer S105 0 e e e

Condensate from dryer S107 0 e e e

Air1047298ue gas streamPreheated combustion air after luvo S67 6780 275 96 266Flue gas after SH3 and RH2 S11 9101 500 93 600Flue gas outlet before luvo S13 9101 301 92 343Flue gas outlet after luvo S14 9298 159 91 169

b) 25 dry coal co-1047297ring caseWatersteam cycle

Feed water inlet to eco S72 4980 300 32728 1329Feed water outlet from eco S4 4980 330 32128 1487Steam outlet from evaporator S6 4980 418 30728 2487Superheated steam outlet from SH S7 4980 610 29328 3482Cold reheated steam intlet to reheater S70 4010 372 6402 3094Hot reheated steam outlet from reheater S71 4010 620 6080 3704Low pressure steam after ST S27 2950 35 6 2289Condensate S20 2950 35 6 146Extracted medium pressure steam to dryer S112 297 287 596 3035Vapour from dryer S105 211 105 100 2686Condensate from dryer S107 297 100 2000 420


c) 100 dry coal 1047297ring caseWatersteam cycle

Feed water inlet to eco S72 5134 300 32728 1329Feed water outlet from eco S4 5134 320 32128 1430

Steam outlet from evaporator S6 5134 418 30728 2487Superheated steam outlet from SH S7 5134 610 29328 3482Cold reheated steam intlet to reheater S70 4134 372 6402 3094Hot reheated steam outlet from reheater S71 4134 620 6080 3704Low pressure steam after ST S27 2305 35 6 2330Condensate S20 2305 35 6 146Extracted medium pressure steam to dryer S112 1187 287 596 3035Vapour from dryer S105 844 105 100 2686Condensate from dryer S107 1187 100 2000 420



8102019 1-s20-S0360544212000783-main


In order to evaluate the effect of speci1047297c parameters on theeconomic feasibility of the examined concepts four parametricstudies are performed The in1047298uence of CO2 allowances price on thetotal electricity generation cost in the three examined cases ispresented in Fig 3 As presented in the previous 1047297gure the elec-tricity generation cost in the 25 dry lignite co-1047297ring case is almostcomparable with the one of the reference case The particulardifference is minimised by increasing CO2 allowances price On theother hand the electricity generation cost in the 100 dry lignite1047297ring case is about 27 VMWh lower than the cost of the referencecase In addition a potential increase of the CO2 allowancespriceupto the level of 30 Vt CO2 will result to the further decrease of theelectricity generation cost up to 41 VMWh compared with theaccording value in the reference scenario

Moreover the in1047298uence of the variation of the raw lignite price

on the electricity generation cost is presented in Fig 4 The fuel costrepresents a considerable fraction of the electricity generation costhence the decrease of raw lignite consumption achieved by the pre-drying technology leads also to a lower dependency of the elec-tricity generation cost by the fuel price In other words a potentialincrease of the fuel price up to 20 compared to the reference casewill lead to the increase of the difference between the raw coal1047297ring and the 100 dry lignite 1047297ring scenario from 27 VMWh to34 VMWh

As a next step a parameter investigation of the CO2 avoidancecost is carried out The 1047297rst de1047297nition of avoidance cost is used inboth examined cases (25 dry lignite co-1047297ring and 100 dry lignite1047297ring) for reasons of comparison ie the cost of CO2 allowances isnot included in the calculation of the electricity generation cost

The effect of the WTA pre-drying systemrsquos CAPEX on the expectedplantrsquos CO2 avoidance cost is examined for both dry lignite

utilisation cases (Fig 5) The avoidance cost of the 25 dry ligniteco-1047297ring case is more affected by a variation of CAPEX due to thelower plant ef 1047297ciency increase compared to the 100 dry coal co-1047297ring case As mentioned above for the current CO2 allowancesprices (4th quarter 2011) the refurbishing of an existing plantaccording to the 25 dry coal 1047297ring scenario is a marginally feasiblepractise from the 1047297nancial point of view Moreover such a refur-bishment project may turn out to economically not feasible in caseof an increase of CAPEX which can be expected in this new tech-nology On the other hand the avoidance cost of the 100 pre-driedlignite 1047297ring case stays below 10 Vt CO2 in all examined casesindicating the considerable potential of lignite pre-drying tech-nology towards improving the 1047297nancials of future dry lignite powerplants

Furthermore in Fig 6 the effect of the fuel price on the CO2

avoidance cost is presented Again the 1047297rst method of calculationof the avoidance cost is followed in both cases for reasons of comparison The CO2 allowances cost is therefore not included inthe avoidance cost calculation and the particular value is affectedby possible raw fuel savings through the increase of the ef 1047297ciencyrate in the pre-drying cases A potential increase of the fuel priceleads to higher bene1047297t of the pre-drying concept over the referencecase and therefore to lower CO2 avoidance cost In the 100 co-1047297ring case the avoidance cost becomes negative for raw ligniteprices higher than the reference price This means that the savings

Fig 2 Breakdown of electricity generation cost in the examined cases

Table 5

Speci1047297c CO2 emissions and CO2 avoidance costs in the examined cases



Speci1047297c CO2 emissions kg CO2kWh 1092 1051 0951CO2 avoidance cost

(CO2 allowancesnot considered)

Vt CO2 e 1033 077

CO2 avoidance cost(CO2 allowancesconsidered)

Vt CO2 e 967 1923

50

55

60

65

70

75

5 10 15 20 25 30 35

e l e c t r i c i t y g e n e r a t i o n c o s t ( euro M

W h )

variation of CO2 allowances price (euro t CO2)

raw coal firing (reference)

25 dry lignite co-firing

100 dry lignite firing

Fig 3 Parametric investigation of the electricity generation cost in relation with the

CO2 allowances price


8102019 1-s20-S0360544212000783-main


8102019 1-s20-S0360544212000783-main


[18] Kakaras E Doukelis A Giannakopoulos D Koumanakos A Economic impli-cations of oxyfuel application in a lignite 1047297red power plant Fuel 200786(14)2151e8

[19] Agraniotis Michalis Grammelis Panagiotis Papapavlou CharalambosKakaras Emmanuel Experimental investigation on the combustion behaviourof pre-dried Greek lignite Fuel Processing Technologies 2009901071e9

[20] Junchao W Weidong F Yu L Meng X Kang W Peng R ldquoThe effect of air stagedcombustion on NOx emissions in dried lignite combustionrdquo Energy(37)725e736

[21] Michalis Agraniotis ldquoSubstitution of coal by alternative and supporting fuels in

pulverised fuel boilers towards reduction of CO2 emissionsrdquo PhD thesis January 2011 [available online]

[22] Michalis Agraniotis Sotirios Karellas Ioannis Violidakis Aggelos DoukelisPanagiotis Grammelis Emmanuel Kakaras ldquoInvestigation of the Pre-drying of lignite in an existing Greek power plantrdquo Thermal Science 102298TSCI110509120A

[23] Greek Ministry of Energy Environment and climate change ministerialdecision Online available wwwetgr 28-09-2010

[24] Directive 200929 EC[25] wwwecxeu[26] IEA ldquoWorld Energy Outlook 2009rdquo[27] US Energy Information Administration Annual energy outlook 2011 April

2011[28] European Commission Energy roadmap 2050 June 2011


8102019 1-s20-S0360544212000783-main


investigations focused on the integration of WTA drying in a futureGreek power plant with elevated steam parameters [16] Recentwork includes the examination of possible oxy-fuel con1047297gurationsfor future Greek power plants burning Greek dried lignite in termsof boiler and steam cycle optimisation [1718] It becomes apparentfrom the above references that all the previous work which can befound in the literature in the relevant topic focuses on the designand the technical aspects of the lignite pre-drying process and onits possible integration into a state of the art lignite power plantsteam cycle No relevant work can be found on the economicaspects of the particular technology which is considered beyondthe technical issues as the decisive factor for its further develop-ment and application In this sense the present work intends tocontribute in the study of the 1047297nancial feasibility of pre-driedlignite 1047297ring as a proposed technology for the next generation of lignite 1047297red power plants

The present work focuses on a state of the art Greek lignitepowerplant and the possibilities of its upgrade by the integration of the lignite pre-drying technology The economic impact of pre-drying is in detail assessed in the framework of the upcoming 3 d

allocation period of Kyoto protocol that will come into effect in2013 From this period and onwards no Green House Gas (GHG)

Allowances will be allocated by national authorities of EU MemberStates to European power plant operators This means that thewhole amount of required allowances according to produced CO2

emissions will be purchased in the international carbon exchangesThe electricity production cost will be signi1047297cantly affectedprimarily in the case of power plants with increased speci1047297c CO2

emissions Power plants 1047297ring low rank coals such as lignite will bemostly affected since the low heating value of their basic fuel andtheir lower plant ef 1047297ciency compared to hard coal power plantslead to higher CO2 emissions in comparison with other coal powerplants

Lignite pre-drying may play a key role in improving the tech-nological dif 1047297culties of power plants 1047297ring low rank coals to be1047297nancially competitive in the new era By the application of lignite

pre-drying technology considerable savings of CO2 emissions areachieved through the improvement of the net plant ef 1047297ciency rateThis increase is achieved

a) By the increase of boiler ef 1047297ciency rate due to the reducedboiler 1047298ue gas losses when 1047297ring higher rank fuels like pre-dried lignite

b) By the implementation of the drying process through using lowtemperature heat (from steam bleed) In this way the exergylosses during the drying process decrease compared to theconventional lignite drying case where hot 1047298ue gas withtemperature of about 1000 C is used as a heating medium

c) By the further utilisation of the vapour produced in the dryingprocess as a heating medium in the 1047297rst steps of feed waterpre-heating

2 Methodology

21 Thermal cycle calculations

In order to evaluate the effect of pre-drying on plant ef 1047297ciency

a steam cycle which is typical for the current state of the art Greekpower plants is taken into consideration The nominal electricpower is 590 MWe with one reheat steam cycle and seven waterpre-heaters with steam extraction from the steam turbine (ST) Thesuperheated steam parameters are 610 C 280 bar while thereheated parameters are 620 C 60 bar A detailed 1047298owsheetdiagram of the considered steam cycle is presented in Fig 1 Thefollowing cases were investigated in this con1047297guration

A Reference case no integration of 1047298uidised bed dryer in thesteam cycle

B 25 pre-dried lignite co-1047297ring case 1047298uidised bed dryer inte-grated in the steam cycle in order to cover the 25 of therequired thermal input

Fig 1 Flowsheet of the considered steam cycle including the intersections with the WTA dryer


8102019 1-s20-S0360544212000783-main
















Table 1


A B C






8102019 1-s20-S0360544212000783-main









C avoid frac14

C CO2 C ref

emref emCO2

(1)





c CO2














Table 3





Table 2

Economic parameters





8102019 1-s20-S0360544212000783-main









t CO2

Table 4

















8102019 1-s20-S0360544212000783-main











Table 5






Vt CO2 e 1033 077


Vt CO2 e 967 1923

50

55

60

65

70

75

5 10 15 20 25 30 35


W h )








8102019 1-s20-S0360544212000783-main


8102019 1-s20-S0360544212000783-main












8102019 1-s20-S0360544212000783-main
















Table 1


A B C






8102019 1-s20-S0360544212000783-main









C avoid frac14

C CO2 C ref

emref emCO2

(1)





c CO2














Table 3





Table 2

Economic parameters





8102019 1-s20-S0360544212000783-main









t CO2

Table 4

















8102019 1-s20-S0360544212000783-main











Table 5






Vt CO2 e 1033 077


Vt CO2 e 967 1923

50

55

60

65

70

75

5 10 15 20 25 30 35


W h )








8102019 1-s20-S0360544212000783-main


8102019 1-s20-S0360544212000783-main












8102019 1-s20-S0360544212000783-main









C avoid frac14

C CO2 C ref

emref emCO2

(1)





c CO2














Table 3





Table 2

Economic parameters





8102019 1-s20-S0360544212000783-main









t CO2

Table 4

















8102019 1-s20-S0360544212000783-main











Table 5






Vt CO2 e 1033 077


Vt CO2 e 967 1923

50

55

60

65

70

75

5 10 15 20 25 30 35


W h )








8102019 1-s20-S0360544212000783-main


8102019 1-s20-S0360544212000783-main












8102019 1-s20-S0360544212000783-main









t CO2

Table 4

















8102019 1-s20-S0360544212000783-main











Table 5






Vt CO2 e 1033 077


Vt CO2 e 967 1923

50

55

60

65

70

75

5 10 15 20 25 30 35


W h )








8102019 1-s20-S0360544212000783-main


8102019 1-s20-S0360544212000783-main












8102019 1-s20-S0360544212000783-main











Table 5






Vt CO2 e 1033 077


Vt CO2 e 967 1923

50

55

60

65

70

75

5 10 15 20 25 30 35


W h )








8102019 1-s20-S0360544212000783-main


8102019 1-s20-S0360544212000783-main












8102019 1-s20-S0360544212000783-main


8102019 1-s20-S0360544212000783-main












8102019 1-s20-S0360544212000783-main












Documents

1-s2.0-S0360544212000783-main