| Abstract | U uvodnom dijelu projekta prezentirani su razlozi za nastanak kombiniranog kogeneracijskog
ciklusa i njegov princip rada. Dalje su se opisali glavni dijelovi plinske turbine i parne turbine i
osnovni načini za povećanje iskoristivosti osnovnog plinskog i parnog ciklusa, te je sve popraćeno
shemama i dijagramima. Odabrane plinske turbine i parne turbine su trebale postići potrebnih 200
MWe električne snage koja je zadana u zadatku rada. Odabrana plinska trubina je Siemens SGT800, a odabrana parna turbina je Siemens SST-600, postrojenje je u izvedbi 2x1. Dvije SGT-800
turbine proizvode 125 MWe, dok jedna Siemens SST-600 proizvodi preostalih 75, s time da može
i više ako je to potrebno. Uz 200 MWe električne snage, također je bio potrebno primijeniti
oduzimanje tehničke pare pri 8 bar, 300 °C i masenim protokom od 30 t/h. Nakon odabiranja
turbina, potrebno je bilo odrediti sva stanja plinskog i parnog ciklusa kako bi se odredili specifični
radovi i toplinske snage, te u konačnici stupanj učinkovitosti.
Za temperaturu okoline odabrana je standardna temperatura zraka od 15 °C , tlaka 1 bar. Prirodni
plin koristio se u komori izgaranja, donje ogrijevne moći 35516 kJ/ , a pri izgaranju sa masenim
protokom zraka od 271 kg/s dobili su se dimni plinovi temperature 1505 °C. Pošto su temperature
dimnih plinova iznimno velike, odabani materijali turbine morat će imati dobru temperaturnu
otpornost, a za lopatice će se morati odabrati prigodan način hlađenja. Dimni plinovi se
ekspanzijom kroz turbinu hlade na temperaturu 596 °C i kao takvi odlaze dalje u proces, točnije
iskorištavaju se u utilizatoru. U utilizatoru se vrši izmjena toplinske energije između napojne vode
tj. pare koja je u parnom procesu. Time se dimnim plinovima i dodatnim izgaranjem proizvodi
272,899 kg/s pregrijane pare temperature 408 °C na tlaku 18,5 bar. Ohlađeni dimni plinovi izlaze
u okolinu pri temperaturi 180 °C. Pregrijana para zatim ekspandira kroz visoki stupanj turbine, na
kraju kojega se vrši oduzimanje pare za potrebu toplinskih potrošača. Ekspandirana pregrijana
para se zatim ukapljuje u kondenzatoru pri tlaku od 1 bar te kondenzatna pumpa usisava kondenzat
u otplinjač na tlak od 7 bar gdje se voda dodatno prerađuje i iz njega se napojna voda, napojnom
pumpom šalje dalje u utilizator za ponavljanje ciklusa.
U proračunu uzeli su se u obzir svi poznati osnovni gubici te je dobivena iskoristivost
kombiniranog procesa od 45,21%, što je za osnovni kombinirani proces realno. Kako bi još dalje
poboljšali iskoristivost procesa potrebno koristiti metode poput naknadnog zagrijavanja,
međupregrijanja pare i regeneracije napojne vode. Uvođenjem ovih metoda povećava se
kompleksnost i cijena ovog postrojenja. |
| Abstract (english) | In the introductory part of the project, the reasons for the development of combined cogeneration
cycle and its operating principle were presented. Furthermore, the main components of the gas
turbine and steam turbine were described, along with the basic methods for increasing the
efficiency of the basic gas and steam cycles, accompanied by diagrams and charts. The selected
gas turbine was the Siemens SGT-800, and the selected steam turbine was the Siemens SST-600,
with a 2x1 configuration. Two SGT-800 turbines produce 125 MWe, while one Siemens SST-600
produces the remaining 75 MWe, with the capability of producing more if necessary. In addition
to the 200 MWe of electrical power, it was also necessary to extract process steam at 8 bar, 300
°C, and a mass flow rate of 30 t/h. After selecting the turbines, all the states of the gas and steam
cycles needed to be determined in order to calculate specific work and heat rates, and ultimately
the efficiency level.
For the ambient temperature, a standard air temperature of 15 °C and a pressure of 1 bar were
chosen. The gas turbine combustion chamber utilized natural gas with a lower heating value of
35516 kJ/kg, and by burning it with a mass flow rate of 271 kg/s, flue gases with a temperature of
1505 °C were obtained. Due to these exceptionally high temperatures, the turbine materials would
have to be highly refractory, and the blades would need some cooling method. The flue gases are
cooled to a temperature of 596 °C by expansion through the turbine and are further utilized in the
process, specifically in the heat recovery steam generator (HRSG). In the HRSG, heat exchange
occurs between the feedwater/steam of the steam process, producing 134.792 kg/s of superheated
steam at a temperature of 420 °C and a pressure of 18.5 bar through additional burning. The flue
gases are further cooled in the HRSG and exit through the chimney into the environment at a
temperature of 180 °C. The expanded superheated steam is condensed in the water condenser at a
pressure of 1 bar, and the condensate pump draws the condensate into the deaerator at a pressure
of 7 bar, where the water undergoes further processing. From there, the feedwater is sent to the
HRSG for the repetition of the cycle using a feedwater pump.
All known basic losses were taken into account in the calculation, resulting in an overall efficiency
of the combined process of 40.98%, which is realistic for the basic combined process. To further
improve its efficiency, methods such as reheating, steam intercooling, and feedwater regeneration
should be employed. However, all improvements lead to increased complexity and investment
costs, so decisions should be carefully analyzed from both economic and engineering perspectives |
