A COMPLICATED PROJECT FOR POWER AND WATER CO- … · dump condensers, sea water pumping station,...

IDA Desalination Industry Action for Good / Santa Margherita, Portofino, Italy May 16-18, 2011 REF: IDA/PORT2011-046

A COMPLICATED PROJECT FOR POWER AND WATER CO-GENERATION: THE RAF SITE

Authors: M. Garzoglio, L. Riccardo Presenter: M. Garzoglio [Process Senior Eng. – Fisia Italimpianti – Italy] Abstract The Ras Abu Fontas (RAF) complex (Qatar) is constituted by four Power Plants named A, B, B1 and B2 and the associated four Water Islands called A, B, A1 and B2. The plants have been built under separate contracts along a time period of about 30 years, and with the requirement that the newest Power Plant could supply steam to the desalination units provided in all operating Water Plants. All desalination units in the complex are of Multi Stage Flash (MSF) type. This goal has been achieved connecting each new Power Plant with each other, through both steam and returning condensate headers, and designing the new heat recovery boilers and auxiliaries to produce steam at sufficient pressure in order to have the necessary driving force. Besides, an higher working pressure of a Heat Recovery Steam Generator (HRSG) allows to reduce the dimension of the boiler itself, and this was helpful installing the new plants within an already existing industrial complex, so optimizing the layout inside the available areas. Fisia Italimpianti engineered, procured and put in service the Water Islands B2 and A1. The former was under a new contract comprehensive of both power and water co-generation having a water production capacity of 30 MIGD with two MSF units in the year 2005. The latter by installing three heat recovery boilers at the outlet of the existing three gas turbine already provided in B1 and three desalination units with a full capacity of 45 MIGD in the year 2007. One of the major issues was the long distance (about 2 km) between the steam source and the identified location for the MSF units. The paper describes the resulting complexity for the whole co-generation complex, explaining the provided technical solutions to properly control the steam and condensate flows and pressures, in order to be able to feed all Water Plants with steam by the newest Power Project. The whole design has been developed considering also possible further expansions of Ras Abu Fontas complex, both for Power and Water. The paper shows how also this further constraint has been taken into account as a challenge for an overall optimization of Power and Water production. The investments and complexity at Ras Abu Fontas Power and Water co-generation site is justified by an higher plant operation flexibility, money saving and reduction of environmental impact optimizing power, steam and water production for the whole complex and consequently reducing the total amount of fuel fed to the power stations.


I. INTRODUCTION Four Power Plants named A, B, B1 and B2 and the associated four Water Islands named A, B, A1 and B2 constitutes the Qatari industrial complex of Ras Abu Fontas (RAF); it is close to the city of Doha and it has been built plant by plant starting from the end of 70s under various separated contracts. The Ras Abu Fontas site permits the life in Doha and neighboring areas, together with other similar plants, supplying both power and potable water for a total amount of about 2200 MW and 160 MIGD. Each Power Island is mainly composed by:

• gas turbines • power transformers and power substation • heat recovery steam generators with post firing • all the required auxiliary equipments: compressed air system, close cooling system, fuel

supply systems as natural gas supply line or fuel oil tanks and lines with relevant safety systems, storm water and sewage systems, and chemical treatment

On the other side, for each Water Island can be individuated the following items:

• sea water intake with offshore and onshore portions • sea water discharge headers and outfall • desalination units • steam and condensate headers • dump condensers to proper control the pressure of the steam within the headers • remineralisation and potabilization plant with relevant pumping station, surge vessels to

avoid water hammer in the export lines • connections to the drinking water distribution network • all the associated systems like: close cooling system, fire fighting, compressed air

distribution, storm water and sewage systems, and chemical treatment Fisia Italimpianti was involved into two contracts; the first was Ras Abu Fontas B2 plant in the year 2005, composed by three Gas Turbine within Power Island; while, the Company installed a Heat Recovery Steam Generator (HRSG) at the outlet of two Gas Turbine provided in the Power Plant, in order to supply steam at the Water Island composed by two desalination units. Under the second contract named A1, in the year 2007 Fisia Italimpianti supplied three HRSG, at the outlet of the three Gas Turbine already installed under Power contract B1, and three desalination units.


fig. I.1: Ras Abu Fontas Industrial Complex is close to Doha


fig. I.2: Ras Abu Fontas Industrial Complex configuration


fig. I.3: Layout of Ras Abu Fontas Industrial Complex


1.1 Ras Abu Fontas site developing The RAF site has been developed along 30 years of history as following:

tab. I.1 All the above plants have been built with their own main components as power generators, power substation, heat recovery steam generators, steam and condensate dedicated systems with relevant dump condensers, sea water pumping station, remineralisation plant, potable water reservoirs and potable water export pumping station, all the relevant auxiliary systems and under the. 1.2 Pressure in the Steam Headers The condition above mentioned that the newest Heat Recovery Steam Generators (HRSG) could supply steam to the desalination units provided in all operating Water Plants has been satisfied connecting each new steam generator with each other via steam and condensate headers. Moreover, the new Heat Recovery Boilers have been designed to produce steam at sufficient pressure in order to have the necessary driving force to supply steam to the oldest steam headers and to control the flow through dedicated control valves. On the other hand, an higher design working pressure at the HRSG at the same steam production capacity allows to reduce the dimension of the boiler itself, and this was helpful installing bigger new Power Plants within an already existing industrial complex to optimize the layout inside the available areas.

PLANT YEAR POWER CAPACITY [MW]

WATER CAPACITY [MIGD]

RAF ‘A’ (three phases) 1977 - 1993 500 55

RAF ‘B’ 1995 610 33

RAF ‘B1’ 2002 380 N.A

RAF ‘B2’ 2005 570 30

RAF ‘A1’

2007

N.A 45

HRSG connected to existing GTs of the Power Plant ‘B1’

(plus Auxiliary Boiler)


In the following figures 1.1 and 1.2 the developing of power and water production at Ras Abu Fontas Industrial Complex vs. time from the first to the last plant is shown

RA

F 'A

' RA

F 'B

'

RA

F 'B

1' RA

F 'B

2'

RA

F 'A

1'

0

500

1000

1500

2000

2500

Pow

er [M

W]

1977 1995 2002 2005 2007

year

Power developing at Ras Abu Fontas complex

fig. I.4

RA

F 'A

' RA

F 'B

'

RA

F 'B

1' RA

F 'B

2' RA

F 'A

1'

0

20

40

60

80

100

120

140

160

180

Wat

er [M

IGD

]

1977 1995 2002 2005 2007

year

Water developing at Ras Abu Fontas complex

fig. I.5


II. RAS ABU FONTAS SITE COMPLEXITY It is easy to understand that the installation of four subsequent Plants, composed by both Power and Water production Islands, each one adjacent to each other and furthermore each Plant provided with all dedicated associated main equipments as before described it leads to an higher level of complexity due to some resulting crossing of pipes, power lines, etc and some required interconnection amongst the plants. In particular for instance, the connection of the steam headers of four subsequent Plants leads to a resulting high level of complexity due to the dimension and number of the steam headers, the distance amongst the different distillation plants, and the required loops to control pressure, temperature and flow from one plant to each other and vice versa. Deeping in detail, two contracts were awarded to Fisia Italimpianti: the Water Island of the Ras Abu Fontas B2 project and the Ras Abu Fontas A1 contract. The former in the year 2005 was under a new contract comprehensive of both power and water co-generation, where the power is composed by three Gas Turbines and at the outlet of two GTs Fisia Italimpianti put two heat recovery steam generators with post-firing, and having a water production capacity of 30 MIGD with two MSF units; one GT works in open cycle. The latter in 2007 in which Fisia installed three heat recovery steam generators with post-firing at the outlet of the existing three gas turbine already provided in B1 and in service since 2002, and three desalination units with a total capacity of 45 MIGD. 2.1 RAF B2 and RAF A1 major issues RAF B2 produces steam at 25 bar in B2 and it can feed the steam headers of both B2 and B plants, RAF B in its turn produces steam at 15 bar and it can supply or accept steam from A and B2 plants via already installed dedicated bi-directional flow control valves and flow control measurements. The distance between the heat recovery steam generators of B2 and B plants is about 100 m, while RAF A desalination plant is at about 500 m far from RAF B steam generators. Due to the fact that the supply steam system is realized with several control valves combined in parallel as in series mode, one of the major issues was how to control the steam flow from B2 to B station in such a way to reduce as much as possible any disturbance to the final users i.e.: two desalination units and the dump condenser installed in B2 as well as the five MSF units and the two dump condensers already existing in RAF B.


fig. II.1: Ras Abu Fontas B and B2 steam supply headers interconnection


Regarding the Ras Abu Fontas A1 contract, the length of the steam lines connecting the heat recovery steam generators installed in RAF B1 area and the desalination units provided under RAF A1 contract is about 2 km. For the first time in the history of desalination the head loss through the line supplying steam to the desalination units was about 3.5 bar at nominal flow and moreover no space was available to install the new pipe-rack nor the pipeline, so the existing pipe-rack have been reinforced and a level was then added. The HRSGs in RAF A1 produce steam at 19 bar and they can feed both the steam header of RAF B and RAF A plants at the same time via dedicated control valves, pressure and flow control loops. The above mentioned factors were the main concerns of RAF A1 project to be address. In fact, the long distance between the location of steam source and steam header pressure control system realized with a dump condenser and relevant control valves, and the Ras Abu Fontas A1 Multi Stage Flash distillation units location, along with the steam compressibility were the major constraints for a proper steam pressure control in the header as well as at the distillation unit inlet. Another problem was the available area to install the heat recovery steam generators under RAF A1 project; that area was small and encircled by existing Plants of RAF B, B1 and B2. In addition, the Gas Turbines of RAF B and RAF B1 have approximately the same capacity, but the required steam production capacity of RAF A1 boilers was more than double and consequently also the expected dimension of the new HRSG was higher than the existing ones while the available area was the same.


fig. II.2: Ras Abu Fontas Industrial Complex steam supply headers interconnection


2.2 Solutions The issues were solved installing dedicated control loops on both steam and returning condensate systems; in detail between B2 and B on the steam side a pressure reducing control valve and related ancillaries have been installed to reduce the pressure from 25 bar to the ones in the B headers (15 bar), to monitor the amount of the steam exchange and to control the steam temperature at the reducing pressure outlet; in fact, the steam in the headers is normally slightly superheated: 5 – 10 °C above saturated point. It was also mandatory to study the proper location of the instrumentation involved in the steam pressure, flow and temperature control loops and the relevant proportional – integral – derivative coefficients as well as the selection of the set points of the loops themselves have also been optimized in order to minimize delay or mismatching in the control. To comply with the contract requirement and to reduce the dimension of the HRSG of RAF A1 a steam generating pressure of 19 bar has been selected instead of the same RAF B operating pressure of 15 bar. While, on the condensate side the working pressure in RAF B plant is enough to assure condensate flow from B to B2, a dedicated control valve and flow meter have been installed to control and monitor the flow. To control the connection amongst RAF A1, A and B on both steam and condensate systems, dedicated control loops comprehensive of all required instruments, control valves and booster pumps have been installed.


III. FUTURE EXPANSION The whole Ras Abu Fontas industrial complex is designed from the beginning considering where possible, also space and provision for future expansion and connection. Fisia Italimpianti used for example the available space in the area of the GTs of RAF B1 to supply steam to the new MSFs of RAF A1, and as required by final client, Fisia itself designed the boilers at RAF B2 plant leaving space to install a new HRSG at the outlet side of the third GT of RAF B2 when may possibly be required. To make it easier the above, spare connections for the auxiliary systems such as closed cooling water circuit or air compressed system has been also provided.


fig. III.1: Ras Abu Fontas A1 heat recovery steam generators installation at the discharge of

the already existing RAF B1 gas turbines


fig. III.2: Ras Abu Fontas B2, possible future expansion


IV. RESULTS The investments and the complexity at Ras Abu Fontas Power and Water Co-generation site are justified by an higher plant operation flexibility; in fact, at any time and for any reason for each one of the Desalination Plant within Ras Abu Fontas the steam is not available by the associated Power Island, the relevant steam header can be feed by an other Power Plant using the RAF common steam header pressure master control, which is able to control properly the steam pressure in the headers and to give the correct set point to the post-firing of each available HRSG in order to minimize the fuel consumption of the entire complex. Following the above we can think to produce steam with GT and associated HRSG under a certain plant and to use the produced steam in an other plant. As we can understand the resultant operating flexibility of the facility does not regard only water production, but it is also relevant to the reduction of environmental impact and consequently money saving. In fact, knowing that the fuel price is different for each Power Station, we can optimize power production using the maximum number of GTs at a load as much as possible close to their own best efficiency point within the Power Plant with more profitable contracts, and exporting the resulting excess of steam to the Water Island associated to a Power Station having an higher fuel price. With the above explained plant flexibility it is therefore possible to reduce the total amount of fuel fed to the Power Islands within RAF complex with a consequent reduction of running costs and environmental impact.


V. CONCLUSIONS In the modern as well as in the existing Power and Desalination Co-generation Plants investing in the proper way to use suitable technology as material, technical solution and electronic tools, in one word the human ingenuity, everything can be done to improve plant performances, optimize fuel consumption and consequently reduce running cost. The above is every day more significant due to the dimension of the plants and mainly to the cost and the availability of the fuel. The solution to the problems caused by human is the man itself.

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A complicated project for Power and Water co-generation:the RAF site

Marco Garzoglio

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The RAF site has been developed along 30 years of history




Each Powe Island is mainly composed by:

• gas turbines• power transformers and power substation• heat recovery steam generators with post firing• all the required auxiliary equipments: compressed air

system, close cooling system, fuel supply systems as natural gas supply line or fuel oil tanks and lines with relevant safety systems, storm water and sewage systems, and chemical treatment




Each Water Island is mainly composed by:

• sea water intake with offshore and onshore portions• sea water discharge headers and outfall• desalination units• steam and condensate headers• dump condensers to proper control the pressure of the

steam within the headers• remineralisation and potabilization plant with relevant

pumping station, surge vessels to avoid water hammer in the export lines

• connections to the drinking water distribution network• all the associated systems like: close cooling system,

fire fighting, compressed air distribution, storm water and sewage systems, and chemical treatment




Power developing at Ras Abu Fontas complex




Water developing at Ras Abu Fontas complex




Ras Abu Fontas site complexity

The installation of four subsequent Plants composed by both Power and Water Islands leads to an high level of complexity:

– Power lines

– Crossing of pipes

– Interconnection through the plants




Ras Abu Fontas and Fisia Italimpianti

• 2005 – RAF B2Power: 3 Gas Turbines – 570 MWWater: 2 Heat Recovery Steam Generators

1 Dump Condenser2 Desalination Units (MSF type) – 30 MIGD

• 2007 – RAF A1Power: 3 Gas Turbines – 380 MW - already existing

(open cycle within RAF B1 Power plant )Water: 3 Heat Recovery Steam Generators

1 Dump Condenser3 Desalination Units (MSF type) – 45 MIGD




RAF B2 major issues

• RAF B2 and RAF B steam headers interconnection and pressure control considering that:

– RAF B2 produces steam at 25 bar– RAF B steam header pressure 15 bar

• Required space for future expansion




Ras Abu Fontas complexity: RAF B2

Ras Abu Fontas B and B2 steam supply headers interconnection




RAF A1 major issues

• Distance between the steam source and distillation units2 km

• RAF A1, RAF B and RAF A steam headers interconnection and pressure control considering that:

– RAF A1 produces steam at 19 bar– RAF B steam header pressure 15 bar– RAF A steam header pressure 10 bar

• Required space for future expansion




Ras Abu Fontas complexity: RAF A1

Ras Abu Fontas Industrial Complex steam supply headers interconnection




Solutions

The solution to the above was the

TECHNOLOGY

software and hardware




Results

The investment and the complexity at Ras Abu Fonta site is justified by:

– plant operation flexibility– reduction of fuel consumption

and consequently:

– money saving– reduction of environmental impact




Conclusions

In the new as well as in the existing plants, investing in the proper way:

• material• technical solution• electronic tools

everything can be done to improve plant performances, optimize fuel consumption and consequently reduce running cost

HUMAN INGENUITY




The solution to the problems caused by human

is the man itself

A COMPLICATED PROJECT FOR POWER AND WATER CO- … · dump condensers, sea water pumping station,...

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