3.11 Flue gas desulphurisation plant materials

Whilst studies are currently being done within the CEGB on possible flue gas desulphurisation plants, it has been identified that the plant based on the lime­ stone-gypsum process will be the most onerous on lay­ out. This plant for a 2000 MW station will require the delivery of some 0.3 million tonnes of limestone per annum and the disposal of some 0.5 million tonnes of gypsum per annum. It is anticipated that the inovemept of these materials will be by rail and can be incor­ porated v ithin the rail arrangements provided for coal delivery. However, warehouse storage will be required for strategic stocks of limestone and gypsum producing a further demand on available land.

3.12 Transmission requirements

It is current CEGB policy to use metal-enclosed gasinsulated indoor substations. This type of substation is considerably smaller than the open switchgear com­ pounds and is less onerous from a layout aspect. The plan area of a typical 400 kV metal clad substation for a 2000 MW power station is of the order of 1 hectare. This includes the associated electrical and auxiliary plant buildings and perimeter roads for access. The use of an indoor substation is more acceptable visually and is not affected by potential problems such as seawater spray, cooling tower spray or coal and dust pollution.

It is preferable that the substation be located adjacent to and in front of the turbine hall as this shortens the generator transformer connections. Ideally this wilalso be on the side of the site from which the transmission lines emanate so that the outgoing feeders can be, arranged in an economical manner. It is also preferable that the outgoing circuits be overhead lines for as far as possible, as the use of 400 kV cables is very costly.

3.13 Construction requirements

The size and location of individual contractors’ areas depends on the contract strategy adopted for placing the orders for equipment, on the number of contractors involved, and would be based to some extent on information supplied by the contractors. Locations would then, as far as possible, be arranged to coincide with programme requirements. However, it is recog­ nised that certain areas may be required early and would need to be close to the excavations for the main buildings. In the case of a PWR, for instance, the contractors for the civil works, the containment liner and the structural steelwork would be in this category. Where only restricted areas would be available imme­ diately adjacent to the station, the orientation of the station may be important to provide adequate locations for all these areas (see Fig 1.32).

Chapter 1

The location of the contractors’ offices, mess huts and the car and bus parks should be within a reasonable distance of both the temporary construction areas and the working areas in the main station complex.

The contractors' areas should be on level welldrained land, but if necessary they could be on a

terraces and the station. Typical contractors' working and storage areas for modern nuclear and conventional stations would be of the order of 25-30 hectares. In addition, areas of some 3-4 hectares would be needed for construction car parks. Storage space would also be required for topsoil storage and late excavation/backfill material.

In order to reduce the length of the construction programme, consideration is given to shipping more components to site ready assembled as modules. For instance, steam turbines have previously been as­ sembled and tested at the manufacturer's works, then dismantled into sections for shipment and reassembled on site. It is possible to reduce the amount of dis­ mantling by sending the high pressure and intermediate pressure cylinders still boxed up with their rotors in place. It may also be possible to despatch condensers as assembled modules. Quality assurance is also better controlled under factory conditions and such items as PWR pressure vessels and steam generators can be shipped rcaily assembled. However, shipping these fully completed pkint modules by road causes problems becaii'-e of their size or weight, or both. This can be solved to a large extent for coastal stations by using a large sea-going barge to deliver these items to a barge berth specially installed as neat to the site as possible. Such a berth could also incorporate docking facilities for roll-on/roll-off vessels enabling many other deliv­ eries to be made by sea. This would reduce the volume of construction traffic on the roads near the site. The use of rail access would also be of benefit if it can be provided economically. Additional land would be required for sidings and offloading facilities.

3.14 Amenity considerations

Whilst recognising that production of a reliable supply of electricity at the lowest possible cost is the para­ mount consideration, it is the CEGB’s statutory duty to pay attention to the appearance of new power stations, both in detailed architecture and in its suitability for the environmental amenity.

Very often the architect may suggest a number of arrangements of buildings or cooling towers in order to achieve the correct massing in the landscape and to improve appearance. This work is done in close col­ laboration with the engineering design staff to ensure that the optimum construction and operational design is still achieved at minimum cost. Landscape architects are also engaged with a view to integrating the station

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Power station siting and site layout

and transmission equipment in the immediate loeale so far as is practicable with the surrounding countryside.

Figure 1.33 shows the successful blending of land­ scape and power station at the Didcot coal fired station site.

3.15 Typical site layouts

As stated earlier it is almost always impossible to satisfy , every requirement perfectly. Three different solutions

to site layout problems are illustrated in Figs 1.34, 1.35 and 1.36 and are described as follows:

Figure 1.34 shows the site layout for a 2000 MW oilfired Station using direct cooling and with a seaborne oil supply. The site area of 21 hectares which was available for the construction of this station was a comparatively small area on which to build a 2000 MW power station. The factors which influenced most of the station layout and plant orientation were:

•The limiting boundaries for river and road access.

•The suitable locations of construction storage and contractors’ areas.

• The need to commission gas turbine plant early in

. the overall construction programme.

•The effect of the extensive cooling water civil works location and access.

•The need to complete the construction by working generally from north west to the access in the south east of this restricted site.

The existence of the transmission routes, together with the knowledge that fuel would be delivered by sea, determined that the boiler house and therefore the chimney should be located near to the river. Conse­ quently, the location and orientation of the boiler drum, turbine hall and generator compounds together with their access routes were established.

The location of construction storage areas and con­

plant which were located at the north east corner of the site. The same considerations influenced the location of gas turbines and their associated fuel tanks. The three gas turbine exhaust flues were directed into a single chimney which also included the flue from the auxiliary boiler, thereby influencing the location of the auxiliary boiler house.

the sootblower air compressor house also in close proximity.

The location of the cooling water intake works in the river dictated the location of the pumphouse on the west side of the site. The outfall shaft was placed at the same end as the pumphouse so that the culvert excava­ tion did not seriously affect access to the boiler house.

Chapter 1

The chlorination plant was consequently located adjacent to the pumphouse.

The administration block, which also contained the central control room, and the workshops were required to be as close as possible to the turbine hall and therefore located in the area to the south east of the main plant buildings.

Figure 1.35 shows the site layout of a 4000 MW coalfired station comprising 6 x 660 MW units, utilising a closed cooling tower system and with railborne coal supply. Here, a balance between the engineering and architectural requirements was achieved. The 400 kV switchhouse was placed outdoors and situated parallel to the turbine hall, while the cooling towers were grouped in two sets of six at either end of the station; this is an architectural requirement, which though not detracting much from operational convenience, required an additional pumphouse. However, views of the station from the surrounding country were greatly improved.

A loop system of sidings was adopted for coal delivery. The workshop and stores were located in the turbine hall and the boiler make-up water treatment plant was located central at the front of the turbine hall. The administration block, canteen and welfare services were located adjacent to the access road.

A major factor affecting the layout ot this station was that it was built in two phases with three units being initially constructed and then the additional three units being completed later. This meant that construction of the later units had to be phased such that minimum disruption was caused to the operation of the first units.

The provision and layout of ancillary services, e.g.,. coal handling plant, ash and dust handling plant, cooling watermake-up and purge systems, etc,, hail to take into account the requirement of early operation for three units with the later addition of a further three units. The physical size of the whole station, however, led to the adoption of a split recirculating cooling water system, each half having its own self-contained system.

Figure 1.36 shows the site layout of a 1320 MW AGR station using direct cooling. The station was the second stage of a two-station development on the same site.

The site investigation revealed the existence of a geo­ logical fault running approximately north-south and bisecting the useful area of the site. Triassic sandstone exists to the west of the fault and is suitable for the support of power station loads. A complex sequence of Namurian mudstones, sandstones and siltstones, which are not suitable for heavy ground loadings, exists to the east of the fault.

The lines of the sea wall and the geological fault converge towards the south of the site and thus create, to the south of Stage 1, a roughly triangular area on which Stage 2 could be located.

At the time that planning permission was sought for Stage 1, the Stage 2 development was envisaged and shown on the planning application as a mirror image of Stage 1. Although Stage 2 could not, in the event.

I

CW INTAKE

N

CW PUMPHOUSE

2CW INLET CULVERTS

3CW OUTLET CULVERTS

HYDROGEN PRODUCING PLANT s SITE CANTEEN

5MAIN CHIMNEY IO FANS

8FO FANS

9BOILER HOUSE

10TURBINE HOUSE

GENERATOR TRANSFORMERS

12400 kV SUBSTATION

13PROPANE STORE GT FUEL OIL TANKS

15 FUEL OIL HEATER HOUSE

16

S2?£=L?WER COMPRESSOR HOUSE WATER TREATMENT PLANT

18GAS TURBINE HOUSE

19AUXILIARY BOILER HOUSE

20 CONTROL ROOM

21

WORKSHOPS ANO STORES

22SITE OFFICES

23PUMPHOUSE

24RFW TANKS

25

26CAR PARKAN° ANC'LLARY STORES

27A’ STATION

28B- STATION

29C STATION

30GATEHOUSE

31SWITCH HOUSE 1

32SWITCH HOUSE 2

33132 kV SUBSTATION GREEN

34132 kV SUBSTATION REO

35

36wStorage tan^1 pumphouse

37auxiliary, jetty

CW OUTFALL

RIVER THAMES

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TURBINE MOUSE • UNiTS 1. 2 AND 3 BOILER HOUSE • UNITS 1. 2 AND 3 BUNKER SAY • UNITS 1. 2 AND 3 PRECIPITATORS - UNITS 1. 2 AND 3 LUBRICATION STORES

GAS TURBINE HOUSE GTs 7. 8 ANO 9 COAL ANO ASH BUILDING

ASH PITS

DUST CONDITIONING HOUSE CONVEYOR JUNCTION HOUSES (PEA, TRACK HOPPER HOUSE

COAL PLANT SUBSTATION COAL PLANT GARAGE

CP JUNCTION HOUSES

45A BUCKET WHEEL MACHINE SOUTH

7 458 BUCKET WHEEL MACHINE NORTH

46A BOOM STACKER A

468 BOOM STACKER 8

47AMENITY BLOCK AND POLYMER PLANT

48SEWAGE TREATMENT PLANT

49MAIN CHIMNEY

50GT CHIMNEY

51SUBSTATION BUILDINGS

5213kV REACTOR ANO SWITCH ROOM

53SUBSTATION BUILDINGS CONTRACTORS ACCOMMODATION CLARIFIERS

SLUDGE LAGOONS ASH LAGOONS

ASH I OIL INTERCEPTOR CW PURGE PUMP CHAMBER MEASURING CHAMBER GATEHOUSE

RIGGERS STORE COOLING TOWERS

CW RETURN CROSS-OVER VALVE PIT CW PUMPHOUSE NORTH

BLOWDOWN DISPOSAL TANK

67COMPRESSOR HOUSE NORTH

68FUEL OIL PUMPING ANO HEATING PLAN!

69BOILER FUEL OIL TANKS

70OIL / WATER SEPARATOR No. 2 TOILETS

72ROAD WEIGHBRIDGE NORTH

73STORES BLOCK

74TURBINE HOUSE • UNITS 4, 5 AND 6

75BOILER HOUSE - UNITS 4. 5 ANO 6

76AUX BOILER HOUSE NORTH

77BUNKER BAY * UNITS 4. 5 ANO 6

78PRECIPITATORS • UNITS 4. 5 AND 6

79ASHPITS

80ADMIN BLOCK SOUTH

81GAS TURBINE HOUSE NORTH GT s 10 11

82GT FUEL OIL TANKS (DIRTY)

83COAL ANO ASH WORKSHOP

84VACUUM CLEANING PLANT

85BUFFER STORAGE TANKS

88SEDIMENTATION TANKS

87HYDROGEN GENERATION

88HYPOCHLORITE PLANT

89HEAVY STORES

90STORES COMPOUND (YARROWS)

91TRAINING CENTRE

92FIRST AID POST

HOUSE

AND 12

stations power thermal — layout Site