TECHNICAL FIELD

The present invention relates to a method for erecting a boiler. The boiler can be any type of boiler, such as a two pass boiler, preferably but not necessarily a large two pass boiler. Alternatively the boiler can also be a tower boiler, a circulating fluidized bed boiler (CFB) or another type of boiler.

BACKGROUND

Boilers have a large and complex structure, whose erection is typically very time consuming. Currently boiler erection is carried out by erecting a main structure having three to five cavities (according to the type of boiler, e.g. for a two pass boiler it has four cavities); within the cavities the inner boiler structure comprising the evaporator (usually defining the peripheral walls of the boiler furnace) , the superheater, the reheater, the economizer, etc., are assembled.

Assembling is done by lifting to the top of the main structure, with a large crane, tuggers or other lifting equiment, each component element-by-element (i.e. single components are lifted to the top of the main structure) ; then the components are connected to the main structure and/or to other components previously lifted and already connected to the main structure and/or to other components.

Lifting single components to the top of the main structure and then connecting them has some drawbacks. In fact, this method is time consuming, because a large amount of single components has to be lifted; this in addition to the time for lifting a number of components, only allows working in one cavity at a time.

In addition, the connection of the components has to be made at altitude, this further slows down the erection and can be risky for the workers.

SUMMARY

An aspect of the invention includes providing a method for erecting a boiler that is faster than the known erection methods .

Another aspect of the invention includes providing a method that is less risky for the workers than known methods .

These and further aspects are attained by providing a method in accordance with the accompanying claims .

Advantageously, according to the method working in more than one cavity at a time is possible and the number of components to be lifted is reduced.

In addition, the number of operations to be done at altitude is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages will be more apparent from the description of a preferred but nonexclusive embodiment of the method, illustrated by way of non-limiting example in the accompanying drawings, in which:

Figures la-lc show different types of boilers,

Figures 2 through 16 show a first embodiment of the method, and Figures 17 through 25 show a second embodiment of the method .

DETAILED DESCRIPTION

With reference to the figures, these show a method for erecting a boiler 1. Any kind of boiler is possible.

Figure la shows a boiler 1 being a two pass boiler. Figure la shows the main structure 2 having four cavities 3, 4 (reference 3 indicates the cavities arranged to house heat exchanging surfaces and reference 4 indicates the cavities arranged to house other components. The cavities 3, 4 house a silo 6 (for the fuel, e.g. coal), a furnace 7 with a first pass 8 through which the flue gas moves upwards, a second pass 9 (backpass) through which the flue gas moves downwards, and an air heater and/or scr 10.

Figure lb shows a boiler 1 being a tower boiler. The boiler 1 has a main structure 2 with three cavities 3, 4. The cavities 3, 4 house a silo 6, a furnace 7 with a first pass 8 (including the tubed walls) and a flue gas duct (without tubed walls), an air heater and/or scr 10.

Figure lc shows a boiler 1 being a circulating fluidized bed boiler. The boiler 1 has a main structure 2 with five cavities 3, 4, which house a silo 6, a furnace 7, a cyclone 11, a second pass 9 (backpass) , and an air heater 10.

Other examples of boilers are naturally possible..

The method for erecting the boiler comprises erecting the main structure 2; the main structure 2 has a number of cavities 3, 4; the number of cavities 3, 4 depends on the kind of boiler to be erected, e.g. in case a two pass boiler is to be erected the main structure 2 can have four cavities 3, 4 while in case a tower boiler has to be erected the main structure 2 can have three cavities 3, 4. Once the main structure 2 is erected, strand jacks 12 or other lifting devices that are able to operate within a cavity, without preventing operation in other cavities, are attached to the main structure or provided at least at the cavities 3.

One or more roofs 13 (typically one for each cavity 3) for the main structure 2 is assembled on the ground; assembling of the roof 13 is preferably made before of or during the erection of the main structure 2.

In the meanwhile, modules are assembled on the ground; the modules comprise heat exchanging surfaces and possibly (but this is not mandatory) headers 15, e.g. supported by hangers .

The heat exchanging surfaces can comprise one or both: - side tubed walls with at least backstays 22 (i.e. stiffening elements for the side tubed walls) or sections of side tubed walls with at least backstays,

internal heat exchanging surfaces or sections of internal heat exchanging surfaces; in this case the internal heat exchanging surfaces can comprise a superheater and/or a reheater and/or an economizer. These internal heat exchanging surfaces can be vertical surfaces, like usual in the first pass of a two pass boiler, or horizontal surfaces, like usual in the second pass of a two pass boiler.

In the attached figures reference 20 indicates modules having headers 15 connected to heat exchanging surfaces being side tubed walls with backstays 22 or sections thereof, and reference 21 indicates modules having headers connected to heat exchanging surfaces being internal heat exchanging surfaces or sections thereof (e.g. reheater, superheater, economizer; with vertical and/or horizontal surfaces) . Each roof 13 is thus connected to the strand jacks 12 and is lifted through the cavity 3; lifting is made up to an intermediate altitude within the cavity 3, such that the modules 20, 21 can be connected to the roof 13 at ground level, while the roof 13 is hanging from the strand jacks 12. The intermediate altitude is an altitude between a ground level G and a top level T of the main structure in correspondence of the cavity 3.

Once the modules 20 and/or 21 are connected to the roof 13, the roof 13 is further lifted; e.g. the roof 13 can be stopped again to an intermediate altitude within the cavity 3, such that further modules 20, 21 comprising at least heat exchanging surfaces and possibly headers 15 are connected at ground level to the modules 20, 21 previously lifted.

Once all modules 20, 21 have been connected to the roof

13 (directly or indirectly via other modules 20, 21), the roof 13 is lifted up to the top of the main structure 2 and is connected to the top of the main structure 2.

Advantageously, since lifting through the cavities 3 occurs by strand jacks 12 or other equipment that when operating in a cavity 3 does not require spaces outside of the cavity 3, it is possible operation in different cavities 3 in parallel. For example, it is possible the installation of modules 20, 21 in different cavities 3 at the same time. In addition, additional components, e.g. components defining the flue gas pass can be assembled at the ground level and then installed in a cavity 3 by lifting them by strand j acks .

In addition, it is possible working in the cavities 4 while working in the cavities 3, e.g. utilizing cranes or other lifting equipment or strand jacks. Therefore, since it is possible working in parallel in different cavities 3, 4 during erection, the erection time of the boiler can be shortened. In addition since assembling and connections of the modules 20, 21 and possibly of other components is mainly done at ground level, the risks for operators are reduced.

In the following two examples of erection of different types of boiler are described. EXAMPLE 1 - erection of a tower boiler - figures 2 through 16

The main structure 2 is built first; the main structure 2 has three cavities, namely one cavity 3 and two cavities 4 (figure 2 shows a side view and figure 3 shows a top view of the main structure 2) .

In the meanwhile, the roof 13 is assembled on the ground (figure 4). Strand jacks 12 or any other lifting equipment is connected to the main structure 2 and the roof 13 is lifted up to an intermediate altitude in the cavity 3 (figure 8) .

In the meanwhile the modules 20, 21 having the headers 15 and the heat exchanging surfaces are assembled on the ground (figures 5, 6, 7) and are connected to the roof 13 that is supported by the strand jacks 12 at an intermediate altitude within the cavity 3 (figures 9, 10).

Then, the roof 13 is further lifted (figure 11) and other modules 20, 21 are connected to the modules 20, 21 previously connected to the roof 13 (figure 12) . These steps can be repeated (figures 13, 14) . Thus the strand jacks 12 can be removed (figure 16) .

Thus the roof 13 is further lifted and connected to the main structure 2, at the top thereof (figure 15) . In addition, during one or more of the previous steps, the air heater and/or scr 10 and the silo 6 or components thereof are assembled.

Additional components defining the flue gas path can also be simultaneously installed.

EXAMPLE 2 - erection of a two pass boiler - figures 17 through 25

Also in this example the main structure 2 is assembled first (figure 17 shows a side view and figure 18 shows a top view of the main structure 2) ; in this case the main structure 2 has four cavities (namely two cavities 3 and two cavities 4 ) .

In the meanwhile, the roofs 13 (one for each cavity 3) are assembled on the ground and are then lifted by strand jacks 12 or any other lifting equipment up to an intermediate altitude in the cavities 3 (figure 19) .

In the meanwhile, modules 20, 21 comprising the headers 15 and heat exchanging surfaces are assembled on the ground.

The modules 20, 21 are thus connected to the roofs 13

(figure 20, 21) , the roofs 13 are thus lifted, as indicated by arrows F, by the strand jacks 12 or any other lifting equipment. If needed one or both roofs 13 can be further stopped one or more times within the cavities 3 in order to connect other modules 20, 21 to the modules 20, 21 already connected to the roof 13 (figures 23, 24).

Finally the roof 13 is further lifted and connected to the main structure 2, at the top thereof and the strand jacks are removed (figure 25) . At the same time, erection of the silo 6 and air heater/scr 10 can take place in the other cavities 4.

Additional components defining the flue gas path can be simultaneously installed.

Naturally the features described may be independently provided from one another.