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In
this project Exergy Analysis of Al-Hussein Power Plant in Jordan is studied. All the system
components are analyzed separately to know the sites having the largest exergy
losses. In addition, the effect of changing the dead state or reference
environment temperaure is observed. The performance of the plant was shown
by a component wise modeling and a step by step break-up of exergy losses for
the considered plant.The maximum exergy relative to the total exergy was
destroyed in the Boiler (77%)
followed by the Turbine (13%), and
then the Forced Draft Fan Condenser (9%).
In addition, the calculated Thermal Efficiency based on the Lower Heating Value (LHV or NCV) of fuel was 26% while the Exergy Efficiency
of the power cycle was 25%. As the reference environment state temperature was
changed slightly, there were no noticeable changes in the performance of major
components and the main conclusion remained the same; the boiler is the major source
of irreversibilities in the power plant. It is seen that chemical reaction is
the most important source of exergy destruction in a boiler system but it can
be cured by preheating the combustion air and decreasing the air–fuel ratio.

Introduction

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Jordan’s energy market is growing at tremendous rates. Annual
demand for electricity has increased by more than 9% during recent years, and
installed capacity and annual generation figures have reached 9000 GW h in 20061. Central
Electricity Generating Company (CEGCO) is the only power generating company
in the country using heavy fuel oil, diesel, gas, and renewable resources. The
power plants are spread in many Jordanian cities, which are transmitting power through
overhead lines of 132 and 400 kV.

Analysis of power generation systems are of scientific interest and
also essential for the efficient utilization of energy resources. The analysis
of energy-conservation process is widely done using the first law of
thermodynamics. However, there is a growing interest in the combined utilization
of the first and second laws of thermodynamics, using the concepts of Exergy and Exergy Destruction in order to evaluate the efficiency with which
the available energy is consumed. Exergetic analysis enables us to
differentiate between energy losses to the environment and internal
irreversibilities in the process2.

Exergy analysis is a method for the evaluation of the performance of
different devices and processes, and it involves considering the exergy at
different states in a series of energy-conversion steps. Using this
information, we can evaluate the efficiencies of different components and the
process steps having the greatest losses can be identified3.

These are the reasons why the exergy analysis is used to analyse a
process in modern times, which provides a more realistic view of the process
and a useful tool for engineering evaluation4. Nowadays researchers5-8 also recommend the use of exergy analysis to aid decision making
regarding the distribution of resources (i.e.capital, research and development
effort, optimization, life cycle analysis, materials, etc.) instead of only
energy analysis3. Exergy analysis has become an important aspect in
providing a clear understanding of the process, to quantify sources of inefficiency,
and to identify the quality of energy used9. Some researchers focused their studies to component exergy
analysis and efficiency improvement10,11 while others invested themselves on systems design and
analysis12-16.

Plant Description

The
power plant has a total installed power capacity of 396 MW. It is located 560 m
above sea level in the city of Zarqa, North east of Jordan 30 km of Amman. It
began producing power in the middle seventies. The power house is composed of
seven steam turbines units (3 × 33 + 4 ×66) MW and two gas turbines (1 ×14 + 1 ×19)
MW at 100% load. The power plant uses heavyfuel oil, which is obtained from a
nearby oil refinery. The total fuel consumed in 2006 was 504,030 tons.
Properties for the heavy fuel oil obtained in the month of April, 2007 are
shownin Table 1.

               Table 1: Properties of Heavy Fuel Oil
used in Al-Husssein Power Plant for April 2007

Property

Value

Density at 15 oC

0.9705 g/ml.

Total Sulfur

3.67 wt%

Flash Point

117 oC

Kinematic Viscosity at 100 oC

35.52 cSt

Pour Point

+7 oC

Ash Content

0.036 wt%

Water and Sediment

0.14 V%

Gross Calorific Value (GCV or HHV)

42943.81 kJ/kg

Net Calorific Value (NCV or LHV)

40504.58 kJ/kg

 

The
schematic diagram of one 66MW unit is shown in Fig. 1.This unit employs
regenerative feed water heating system. Feedwater heating is carried out in two
stages of high pressure heaters (HPH1, HPH2) and two stages of low pressure
heaters (LPH4, LPH5) along with one deaerating heat exchanger. Steam is
superheated to793 K and 9.12 MPa in the steam generator and fed to the
turbine.The turbine exhaust stream is sent to an air-cooled condenser and the
condensate to the condensate return tank (CRT). Then,the cycle starts over
again. The operating conditions of the power plant are summarized in Table 2.

 

Table 2:
Operating Conditions of the Power Plant

Operating Condition

Value

Mass flow rate of fuel

5.0 kg/s

Inlet gas volumetric flow rate to burner

188.790 Nm3/h

Stack gas temperature

411.15 K

Feed water inlet temperature to boiler

494.15 K

Steam flow rate

275 ton/h

Steam temperature

793.15 K

Steam pressure

9.12 MPa

Power output

56 MW

Power input to FDC/fan

88 kW

Number of fans

18

Mass flow rate of cooling air

23900 ton/h

Combined pump/motor efficiency

0.95

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