Rankine cycle da closed feed water heaters suna da muhimmiyar abubuwa kuma ana amfani da su a duk yanar gizgiza na zaman kansu. Closed feed water heater ya amfani da hanyar zama-zama na wuri, yana nufin cewa steam ko bleed steam da aka fito daga turbine ya ba da hanyar zama-zama na wuri zuwa mai ruwa a shell and tube heat exchanger. Saboda haka, ba za a iya halartar steam da ruwa kafin kafin, saboda haka an yi wa steam da ruwa a matsayin fassara na musamman. Close feed water heater a cycle ya zama a T-s diagram kamar yadda aka bayyana a nan a Fig:1.
Idan ta fi sani, ya kamata zama-zama na wuri a closed feed water heater ya ba da hanyar zama-zama na wuri kafin kafin, yana nufin cewa irin hanyar zama-zama na wuri ya zama tushen ruwa (mai yin hanyar zama-zama).
Amma a yanayi, irin hanyar zama-zama na wuri da ruwa ya samu tushen da ya fi shafi shi ita ce yana da takaitaccen darajar saturation-temperature na steam. Dalilin haka ita ce akwai bukatar darajoyi masu temperature gradient don hanyar zama-zama na wuri daidai da tarihi.
Wannan condensate ko condense steam daga heater shell ya zama zai fito zuwa heater da ke biyu (low-pressure) a cycle ko kuma kafin kafin zuwa condenser.
Open da closed feed water heaters suna da abubuwan da suke tsabta:
Open feed water heater |
Closed feed water heater |
Open da sauki |
Na faruwa a cikin design |
Yanayin zama-zama na wuri mai kyau |
Zama-zama na wuri mai ci |
Mixing extraction steam da feed water temperature a pressure vessel |
Mixing feed water da steam a shell and tube type heat exchanger. |
Ana bukatar pump don in fito ruwa zuwa stage da ke biyu a cycle. |
Closed feed water pumps ba su bukata pump kuma zai iya taimakawa ta hanyar farkon fassara daga cikin heaters a cycle. |
Yana bukatar maida |
Babu bukatar maida |
Kadan |
Girma |
Duk yanar gizgiza na zamani suna amfani da combination of open da closed feed water heaters don in kara thermal efficiency na cycle.
Engineering thermodynamics yana nuna hanyar zama-zama na wuri (heat) zuwa work. A yanar gizgiza, wannan ya zama tare da hanyar zama-zama na wuri zuwa working fluid da ake kira mai ruwa. Saboda haka, dalilin ya fi sani ita ce in bude wastage na wuri na steam a steam turbine condensers. Wannan zai zama mumkin idan muka sami hanyar zama-zama na wuri da ke zama low-pressure steam zuwa condenser.
Cogeneration shine concept of utilizing the heat of the steam for a useful purpose, rather than wasting it (currently wasted in the condensers).
Cogeneration na nufin Combined Heat and Power (CHP) wanda ake kiyaye zama-zama na wuri da power daidai don industry requiring process heating steam. A cogeneration plant, both heat-and-power suna amfani da su daidai saboda haka efficiency of it can be as high as 90% or more. Co-generation offers energy savings.
Cogeneration ya ba da sakamako da wastage na large amount of steam kuma zai iya amfani da su a many devices in the form of heat. Most of the industries like paper and pulp, chemical, textile and fiber and cement are depending upon co-generation plant for process heating steam. Process heat steam requirement in above industries are in the order of 4 to 5 kg/cm2 at temperature around 150 to 180oC.
Paper, chemical and textile industries require both electric power and process steam to accomplish their objective. So this requirement can be easily meet through by installing cogeneration power plant.
Temperature in inside the boiler is of the order of 800oC to 900oC and the energy is transferred to the water to produce steam of pressure 105 bar and temperature around 535oC for co-generation power plants. Steam at these parameters are considered as of very good quality source of energy and is thus first utilized in steam turbine for producing power and the turbine exhaust (low quality energy) is used to meet the requirement of process steam.
Cogeneration plant is known for meeting the requirement of power while meeting the process steam requirement of Industrial processes.
Ideal steam-turbine co-generation is shown in the figure 2 above. Let us say that the process heat requirement Qp is at 5.0 Kg/cm2 at around 100 KW. In order to meet the process steam requirement at 5.0 Kg/cm2 steam is expanded in the turbine till the pressure of the steam drop to 5.0 Kg/cm2 and thus produces the power around 20 KW.
The condensate from process heater is recycled backed to boiler for cyclic operation. Pump work required to raise the pressure of the feed the water in the cycle is considered as small so not considered.
All energy transferred to the working fluid in the boiler is used either in steam turbine or in process plant, thus utilization factor of the cogeneration plant is:
Where,
Qout Heat rejected in the.
Thus in the absence of the condenser the heat utilization factor of the cogeneration plant is 100%.
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