Maritime University of Szczecin
Akademia Morska w Szczecinie
2010, 23(95) pp. 80–85 2010, 23(95) s. 80–85
The influence of the selected parameters on the economic
characteristics of a coal-fired power plant with CCS installation
Wpływ wybranych parametrów na charakterystykę
ekonomiczną węglowych siłowni z instalacją CCS
Janusz Kotowicz, Katarzyna Janusz-Szymańska
Silesian University of Technology, Institute of Power Engineering and Turbomachinery Politechnika Śląska, Instytut Maszyn i Urządzeń Energetycznych
44-100 Gliwice, ul. Konarskiego 18, e-mail: janusz.kotowicz@polsl.pl; katarzyna.janusz@polsl.pl Key words: CO2 capture, CO2 avoided emission
Abstract
In this paper the influence of carbon dioxide capture installation (CCS installation) on the efficiency of a coal power plant is presented. The power demand for the membrane separation and the efficiency losses of the power plant (14.04 percentage points) after implementation of the CCS installation is shown. A method for reducing these losses through integration of the CCS installation with the power plant is proposed. The main aims of the integration are heat exchange between media and decrease of the CO2 temperature before
compression. Implementing of this process can result in a significant reduction of the efficiency loss by around 7 percentage points. The influence of the integration on the unit sale price of electricity as well as on the cost of CO2 avoided emission was also determined. The influence of the fuel cost , investment cost of the
CCS installation on the limit sale price of electricity and CO2 avoided emission cost was analyzed in details.
Słowa kluczowe: wychwytywanie CO2, unikanie emisji CO2
Abstrakt
W artykule przedstawiono wpływ możliwości wychwytywania dwutlenku węgla poprzez instalację CCS na efektywność elektrowni węglowych. Pokazano zapotrzebowania mocy dla separacji membranowej i straty wydajności elektrowni (14.04 punktów procentowych) po wykonaniu instalacji CCS. Zaproponowano zinte-growanie instalacji CSS jako sposobu zminimalizowania strat elektrowni. Głównym celem integracji jest wymiana ciepła pomiędzy mediami oraz spadek temperatury CO2 przed kompresją. Realizacja tego procesu
może doprowadzić do znacznego zredukowania wydajności o około 7 punktów procentowych. Został rów-nież określony wpływ integracji na cenę sprzedaży jednostki energii elektrycznej, jak rówrów-nież na koszty po-niesione na uniknięcie emisji CO2. Zanalizowano także wpływ kosztów paliwa oraz wprowadzenia instalacji
CCS na limit ceny sprzedaży energii elektrycznej i uniknięcia emisji CO2.
The influence of CO2 separation on
the efficiency of a coal power plant
In the paper [1] supercritical coal power plant was analyzed. Characteristic parameters of this block are as following: pressure of live steam 28.5 MPa, temperature of live steam 600°C. This is the reference system for the Polish power engineer-ing after the year 2012. The electric power of this power plant is equal Nel,REF = 600 MW and the
effi-ciency of the electricity production equals 0.4878.
The emission from such a systems is equal to 121.3 kg/s [2]. Assuming that the block annual work is 7500 h, the CO2 emission would amount to
3 275 100 Mg. The reduction of CO2 emission is
necessary. In order to meet this task in [1] the membrane separation of CO2 from flue gases was
proposed. It was assumed that in the membrane separation 90% of CO2 emission was captured and
the mole fraction of carbon dioxide in the stream separating CO2 should be over 80%. The membrane
using the Aspen software. For assumption deter-mined in the paper [1] the method of selecting pa-rameters of this process was presented. The pres-sure of the flue gases was determined on both sides of the membrane in order to keep the power need for the separation process at the minimum. The flue gases have the atmospheric pressure. The driving force of the process is the subatmospheric pressure for the membrane module. For the pressure equal to 0.0028 MPa the electric power for driving a vacu-um pvacu-ump is equal Nel,VP = 45.07 MW. The power
rating of CCS installations equals to 7.51% of the total power of the plant. The purity of the separated CO2 equals to 84.8% and the carbon dioxide
reco-very ratio amount to 90% [1].
According to the literature [3, 4, 5] liquefaction of CO2 for transport needs the compression of CO2
to the pressure around 10 – 15 MPa, depending on the purity of the separated CO2. In the analysis
pre-sented in [1] carbon dioxide was compressed to both pressure – 10 MPa and 15 MPa. Diagram of the installation for CO2 capture from flue gases is
presented in figure 1.
The efficiency of electricity production in the power plant with the electric power of the motor compressors driving and vacuum pump in consi-deration can be written as:
) 1 ( 1 REF , CCS , el el (1) where: REF , C , VP , 1 el el el N N N (2)
where: ηel – efficiency [%], δ1 – power station
in-ternal load rate for CCS installation, Nel – power
[MW], index: REF – reference system, CCS – plant with CO2 capture, C – compressor, VP – vacuum
pump.
The efficiency losses in relation to the power plant without CO2 capture and compression are
significant, equal to 14.04 percentage points for CO2 pressure of 10 MPa and 15.40 percentage
points for 15 MPa [1].
For the purpose of decreasing the efficiency losses, the cooling heat of the flue gases and sepa-rated carbon dioxide may be reintegsepa-rated into the steam-water cycle of the steam turbine in the refe-rence system (Fig. 1). Such an integration allows to eliminate the steam bleeding, causing a correspond-ing increase in steam flow to the steam turbine and increasing the power by ΔNel. In the same time an
increase of the efficiency of electricity production in the reference system. In that case for the calcula-tion of ηel,CCS in the palced of δ1, δ2 should be put:
REF , C , VP , 2 el el el el N N N N (3)
Fig. 1. Diagram of the system of membrane separation and compression of CO2 from flue gases emitted by the power plant
(B – boiler, RH – reheater, CND – condenser, DA – deaerator, HE – heat exchanger, M – membrane module, VP – vacuum pump, C – compressor)
Rys. 1. Schemat procesu wychwytu CO2 ze spalin i integracja z obiegiem cieplnym bloku węglowego (B – kocioł, RH –
podgrzewa-cze regeneracyjne, CL – schładzacz pary, DA – odgazowywacz, CND – skraplacz, HE – wymiennik ciepła, M – moduł membrano-wy, VP – pompa próżniowa, C – sprężarka)
Power station internal load rate for CCS installa-tion (δ2) takes into account the use of cooling heat
of the flue gases and separated CO2 in the steam
turbine cycle.
The influence of the compressed captured CO2
on the efficiency of the unit is shown in table 1 while the scheme of the integration of carbon cap-ture installation with supercritical coal power plant is shown in figure 1.
Table 1. Parameters of the particular equipment connected to the CCS installation
Tabela 1. Parametry poszczególnych urządzeń podłączonych do instalacji CCS
Characteristic parameters
Power plant with CCS and without using
the cooling heat
Power plant with CCS and with using the cooling heat
of the plant Value Unit 10 MPa 15 MPa 10 MPa 15 MPa
Nel VP MW 45.07 45.07 45.07 45.07 Nel C MW 74.07 81.40 74.07 81.41 δ1 – 0.1981 0.2103 0.1981 0.2103 ΔNel MW – – 27.7 27.7 δ2 – – – 0.1519 0.1641 ηel, REF – 0.4878 0.4878 0.4878 0.4878 ηel, CCS – 0.3912 0.3852 0.4137 0.4077
Analysis of the electricity production cost
In the conducted analysis of the economical ef-fectiveness the net present value (NPV) method was used. NPV is one of the fundamental and most frequently applied economic coefficients for the assessment of the economical effectiveness of the investments. NPV is a sum, discounted separately for each year of the net cash flow, observed in the life cycle of the project, assuming constant rate of discount. The NPV indicates the profit that will be gained by a potential investor. The choice of optimal scenario of the investment should be done assuming NPV max. It can be described by the equation:
N r CF 1 1 NPV (4)The value of the discount rate was assumed at 6.2%. In order to determine the cash flow CFτ the
total investment costs (J), profits from sales (Sel),
overall production costs (KPR), the income tax (Pd),
changes of the working capital (Kobr), amortization
charges (A), interest (F) and clearance value of the designed installation (L) (L, L = 0 when
0 N – 1) had to be known.
Thus, the equation describing the cash flow CFτ
can be written as:
JSel KPRPdKobr AFL
CF (5)
The investment costs in simplified analysis are given by equation: REF , CCS REF , el el N N i N i J (6)
where: iN – unit investment cost for the power
installation [€/kW], iCCS – unit investment costs for
the CCS installation [€/kW].
The essential component of the equation (6) is the profit from sales, expressed as:
el el el el N C d S el
,REF 0 1 (7)where: Cel – average price of electricity [€/MWh],
τel – the annual time of operation [h], δ = δREF +
δCCS, δREF – power station internal load rate
refe-rence systems.
Total costs of production were determined as a sum of the following costs:
F A K K K K K K KPR F o ps E sr r (8) where: KF – cost of fuel, Ko – cost of services, Kps –
cost of other raw materials, KE – other operating
costs, Ksr – environmental costs, Kr – costs of
main-tenance and exploitation, A – amortization costs, F – interest.
The economic analyses were made for the refe-rence system and also for similar power unit, taking into account the investments and costs connected to the CO2 capture installation. For the system with
CO2 separation calculated earlier values of purity of
separated CO2 equal to 0.848 and carbon dioxide
recovery ratio 0.9 were assumed. Also in analysis take into consideration total power station internal load rate (δ).
Exemplary literature data [5, 6, 7, 8, 9] for dif-ferent supercritical power plants taking into account the cost of CO2 separation served to determine the
investment costs.
For the economic analysis of the supercritical power plant the following assumption were taken: the investment costs were assumed at 1100
€/kW for the reference system and for the power plant with CO2 capture they were increased by
540 €/kW,
power station internal load rate reference sys-tems was 6%,
operating costs of the capture installation were assumed at 3 €/MWh,
the annual operation time was 7500 hours, amortization rate was given at 6.67 %,
the constant of repairs was determined at the level of 0.5% of the capital costs for the first ten
years of operation and 1% for the following ten years,
the investment cost are spread into three years of the construction (15/30/55%),
the conduction of the power generating plant is financed in 75% by the commercial credit at the interest of 6% and it is paid through 10 years, the income tax rate was assumed at 19%, the average cost of fuel was 55 €/Mg.
In the economic analysis the limit sale price of electricity Cgr was calculated. For the reference
systems without CO2 capture it was described by
the index REF and for the power plant with carbon capture installation it was described by the index CCS.
For both systems the limit sale price of electrici-ty is a quantielectrici-ty determined by the condition:
0 ) (
NPVCgr (9)
An important economic rate for the power sys-tem with CO2 capture is also the CO2 avoided
emis-sion (EAV) and its cost. The cost of CO2 emission
avoidance (CAV) is calculated according the
equa-tion: AV REF CCS AV E C C C gr gr (10) where: CCS REF AV E E E (11)
E – CO2 emission, index: REF – reference system,
CCS – plant with CO2 capture.
The results of the economic analysis are pre-sented in table 2 for two pressures of separated carbon dioxide.
The analysis of the influence of the price of CO2
allowances purchase (CUP) on the limit sale price of
electricity were made in the research. In this case to the right side of the equation (8) the cost of pur-chase of allowances for CO2 emission (KUP) should
be added, determined from the formula:
UP
UP E C
K (12)
The results of calculation make for two values of the price of CO2 allowances purchase (20 €
/ MgCO2 and 50 €/MgCO2) are shown in table 3.
The price of allowances influences significantly the price of electricity production, especially for the systems without CCS installation. From the con-ducted analysis it can be seen, that when the price of CO2 emission allowances will increase up to
40 €/MgCO2, the production of electricity in the
systems integrated with CCS will be profitable, because the price of emission allowances will be
Table 2. Results of the economic analysis calculation Tabela 2. Wyniki kalkulacji ekonomicznej
Characteristic parameters Unit
Power plant 600 MW
without using cooling heat with using cooling heat Power plant 600 MW 10 MPa 15 MPa 10 MPa 15 MPa
The investment costs for the reference system €/kW 1100 1100
The investment costs for power plant with CCS installation €/kW 540 540 Unit sale price of electricity Cgr
REF €/MWh 35.80 35.80
CO2 emission EREF kg/MWh 726 726
CO2 emission after separation ECCS kg/MWh 73 73
CO2 avoided emission EAV kg/MWh 653 653
Power station internal load rate CCS installation – 0.1981 0.2103 0.1519 0.1641 Unit sale price of electricity after CO2 separation CCCSgr €/MWh 61.80 62.84 58.18 59.09
Costs of CO2 avoided emission CAV €/MgCO2 39.82 41.41 34.27 35.67
Table 3. Influence of the price of allowances purchase on the price of electricity Tabela 3. Wpływ cen zakupu na cenę jednostki elektrycznej
Characteristic parameters without CCS installation Power plant 600 MW
Power plant 600 MW without using cooling heat
Power plant 600 MW with using cooling heat 10 MPa 15 MPa 10 MPa 15 MPa
CO2 emission, kg/MWh 726 73 73
Power station internal load rate 0.06 0.2581 0.2703 0.2119 0.2241
The price of emission allowances, €/MgCO2 20 20 20
Unit sale price of electricity C , €/MWh gr 51.25 64.60 65.68 60.81 61.76
The price of emission allowances, €/MgCO2 50 50 50
higher than the investment and exploitation cost of the CCS installation.
Also, the susceptibility analysis of influence of the investment costs and the fuel cost were made. The results of this analysis are presented in figures (Figs 2 and 3).
It can be stated from figures 2 and 3 that the internal load rate plays the essential role in forming the price of electricity. By using cooling heat of the flue gases and compressed CO2 in the steam turbine
cycle, the price of electricity will decrease by around 3.6 €. The cost of avoided emission will change by around 5.5 €. It can be seen in figure 2 when the CCS installation investment costs in-crease to 700 €/kW, the price of electricity increas-es about 3 €. However, the costs of CO2 avoided
emissions increase about 4.5 €. The cost of fuel has an important influence on the price of electricity.
In the susceptibility analysis costs of fuel were tested and the results of this analysis is presented in figure 3. The price of fuel was changed by 20% gr
CCCS [€/MWh] a)
gr
CCCS [€/MWh] b)
Fig. 2. The influence of the investment costs of the CCS installation on the limit sale price of the electricity, and on the cost of CO2 avoided emission, for the system with (δ2) and
without (δ1) the use of cooling heat of CO2: a) for CO2 pressure
10 MPa; b) for CO2 pressure 15 MPa
Rys. 2. Wpływ kosztów inwestycyjnych instalacji do wychwy-tu CO2 na graniczną cenę sprzedaży energii elektrycznej i na
koszt emisji uniknionej CO2 dla układu bez (δ1) i z
wykorzy-staniem (δ2) ciepła schładzanego CO2: a) dla ciśnienia
końco-wego CO2 10 MPa; b) dla ciśnienia końcowego CO2 15 MPa
CAV [€/MWh] CAV [€/MWh] iCCS [€/kW] iCCS [€/kW] iCCS [€/kW] iCCS [€/kW] gr CCCS [€/MWh] a) gr CCCS [€/MWh] b)
Fig. 3. The influence of the fuel costs on the limit sale price of electricity and on the cost of CO2 avoided emission, for the
system with (δ2) and without (δ1) utilizing the cooling heat of
CO2: a) for CO2 pressure 10 MPa; b) for CO2 pressure 15 MPa
Rys. 3. Wpływ ceny paliwa na graniczną cenę sprzedaży ener-gii elektrycznej i koszt emisji uniknionej CO2 dla układu bez
(δ1) i z wykorzystaniem (δ2) ciepła schładzanego CO2 dla
nakładów inwestycyjnych 1640 €/kW: a) dla ciśnienia końco-wego CO2 10 MPa; b) dla ciśnienia końcowego CO2 15 MPa
Fuel price [€/Mg]
Fuel price [€/Mg]
CAV [€/MWh]
CAV [€/MWh] Fuel price [€/Mg]
from considered value. A change of fuel price has the influence on the change of the limit sale price of electricity by around 4.5 € but if using the cooling heat of separated carbon dioxide, the price of elec-tricity decreases by about 3.4 €.
Conclusions
In this paper the energy consumption of CO2
capture from flue gases was shown. The power losses and the efficiency losses of the power plant with CO2 capture installation for two pressures was
presented. The integration of CO2 separation cycle
with the supercritical power plant unit has the aim to decrease power losses and efficiency losses, what have a significant influence on electricity price. Presented indicators of the power station internal load rate for CCS installation before and after integration of both systems have the aim to show by how much can the cost of electricity pro-duction be decreased.
The economic analysis was done for the refe-rence system and also for power unit, taking into account the investments and the costs connected to the CO2 capture installation. In this analysis the
limit sale price of electricity and costs of CO2
avoided emissions were calculated. The price of electricity for the unit without the use of heat of the flue gases and compressed CO2 is determined at the
level of 61.80 €/MWh and can over decrease to 58.18 €/MWh when the CO2 capture installation
was integrated with the unit cycle.
In the susceptibility analysis of the investment costs, price of fuel and annual operating time was tested. The cost of electricity generation decreases with longer annual operating time. When the CCS installation investment costs increase to 700 €/kW the price of electricity increase by about 3 €. How-ever, the costs of CO2 avoided emissions increase
by about 4.5 €. The fuel price has an influence of about 4.5 € on the price of electricity and of above 6.8 € on costs of CO2 avoided emissions. If using
the cooling heat of separated carbon dioxide the
price of electricity would decrease by about 3.4 €, while the costs of CO2 avoided emissions change by
about 5.5 €.
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Recenzent: dr hab. inż. Andrzej Adamkiewicz, prof. AM Akademia Morska w Szczecinie
