EP3971473B1

EP3971473B1 - Heat recovery boiler and plant comprising said heat recovery boiler

Info

Publication number: EP3971473B1
Application number: EP21197547.9A
Authority: EP
Inventors: Ruggiero DADDUZIO; Thomas GIANI; Vincenzo PANEBIANCO
Original assignee: AC Boilers SpA
Current assignee: AC Boilers SpA
Priority date: 2020-09-17
Filing date: 2021-09-17
Publication date: 2023-06-07
Anticipated expiration: 2041-09-17
Also published as: EP3971473C0; EP3971473A1

Description

TECHNICAL FIELD

The present invention relates to a heat recovery boiler and to a plant comprising said heat recovery boiler. In particular, the present invention relates to a heat recovery boiler configured to produce steam by utilising the heat dispersed from gas turbines and/or industrial processes.
The present invention further relates to a steam generation thermal plant comprising said heat recovery boiler.

STATE OF THE PRIOR ART

Steam generation thermal plants normally comprise a heat recovery boiler, which is connected to a hot flue-gases source. The hot flue-gases source can be a gas turbine or an industrial plant.
The efficiency of the thermal exchange in the heat recovery boiler depends on many factors, among which the distribution of the velocity of the hot flue-gases that flow in the boiler.
The heterogeneity, in terms of velocity, of the flue-gases that circulate in the boiler can lead to the creation of "hot" areas having a high concentration of hot flue-gases and "cold" areas, in which the concentration of the flue-gases is much lower.
This entails an inefficiency of the thermal exchange in the boiler and a high risk of breakage of the boiler due to the arising of cracks caused by the high temperature differences to which the structures of the boiler are subject. Furthermore, in the case the boiler is provided with one or more post-burners, the risk of flame instability and/or of increase in the pollutant emissions rises.
Document N. US5555718 illustrates an inlet diffuser of a boiler provided with a plurality of tubes dedicated to the injection of at least one reactant for the reduction of NOx emissions.
Document N. JPH066901 illustrates a perforated plate arranged inside the boiler.
Such solutions, however, are not capable of preventing the aforementioned problems while maintaining, simultaneously, high efficiency levels.

OBJECT OF THE INVENTION

Therefore, an object of the present invention is to manufacture a boiler which is devoid of the drawbacks highlighted herein of the known art; in particular, an object of the present invention is to manufacture a boiler which allows overcoming the aforementioned drawbacks in a simple and cost-effective manner, both from the functional point of view, and from the constructive point of view.
In particular, an object of the present invention is to manufacture an efficient and reliable heat recovery boiler.
In accordance with such objects, the present invention is described in claim 1.
Thanks to the presence of at least one flow rectifier assembly, the vorticity of the flow flowing into the flue-gases flowing chamber is controlled in order to obtain a velocity profile which is homogeneous and capable of optimising the thermal exchange.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will appear evident from the following description of the embodiment thereof, with reference to the figures of the accompanying drawings, wherein:

Figure 1 is a schematic view, with parts in section and parts removed for clarity, of a steam generation plant comprising the heat recovery boiler according to the present invention;
Figure 2 is a schematic perspective view, with parts in section and parts removed for clarity, of a detail of the heat recovery boiler of Figure 1;
Figure 3 is an enlarged perspective view, with parts removed for clarity, of a particular of the detail of Figure 2;
Figure 4 is a perspective view in section, with parts removed for clarity, of the detail of Figure 2.
Figure 5 is a schematic representation, with parts removed for clarity, of a further detail of the heat recovery boiler of Figure 1.

PREFERRED EMBODIMENT OF THE INVENTION

In Figure 1, reference numeral 1 indicates a combined cycle plant for the production of energy.
The plant 1 illustrated in Figure 1 is represented schematically and is not complete of all its parts.
The plant 1 is preferably configured to produce only electric energy.
A variant not illustrated provides for the plant 1 to be configured for the production of thermal energy, useful for example in the applications for the district heating.
The plant 1 comprises a gas turbine unit 2, a steam turbine unit 3, a boiler 4, and a tank 5.
The gas turbine unit 2 is the first engine of the combined cycle plant 1 and can be fed with any combustible.
The gas turbine unit 2 is connected to a generator (not illustrated) and comprises a compressor 7, a combustion chamber 8 and a gas turbine 9.
The steam turbine unit 3 is coupled to a respective generator (not illustrated in the accompanying figures) and comprises a high-pressure steam turbine, a medium-pressure steam turbine, and a low-pressure steam turbine (not illustrated in the accompanying figures).
The boiler 4 regenerates the residual heat of the combustion flue-gases generated by the gas turbine unit 2 and produces steam to be fed to the steam turbine unit 3.
In particular, the boiler 4 comprises a flue-gases flowing chamber 11, an inlet diffuser 12, a steam circuit 14 and a stack 15.
The flue-gases flowing chamber 11 extends along a longitudinal axis A and is provided with an inlet 16 and an outlet 17.
In the non-limiting example described and illustrated herein, the flue-gases flowing chamber 11 extends along an axis A arranged, in use, substantially horizontal.
According to a variant not illustrated, the flue-gases flowing chamber can extend along an axis arranged, in use, substantially vertical.
The inlet diffuser 12 is connected to the inlet 16 of the flue-gases flowing chamber 11 and is fed with the flue-gases from the gas turbine 9. The flue-gases flow into the inlet diffuser 12 and into the flue-gases flowing chamber 11 substantially following an advancing direction D.
The outlet 17 of the flue-gases flowing chamber 11 is connected to the stack 15, through which the discharge of the flue-gases into the atmosphere takes place.
The steam circuit 14 is schematically represented in Figure 1. Substantially, the steam circuit 14 is fed with water, preferably from the tank 5, and extends at least partially inside the flue-gases flowing chamber 11 in order to exploit the heat of the flue-gases to generate steam.
The water of the tank 5 is preferably demineralized and is mostly water from a condenser (not illustrated) connected to the steam turbine unit 3.
With reference to Figure 2 and to Figure 4, the inlet diffuser 12 is provided with a bottom wall 19, with a top wall 20, with two side walls 22, with a flue-gases inlet 23 and with a flue-gases outlet 24.
It is understood that the bottom wall 19 and the top wall 20 can be arranged inverted in configurations of the boiler 4 different from that of the non-limiting example described and illustrated herein (for example with vertical flue-gases flowing chamber).
The bottom wall 19 and the top wall 20 diverge away from each other along the advancing direction D. In other words, the distance between the bottom wall 19 and the top wall 20 increases along the advancing direction D and towards the inlet 16 of the flue-gases flowing chamber 11.
Also the side walls 22 can diverge away from each other along the advancing direction D. Preferably, the divergence between the bottom wall 19 and the top wall 20 is greater than the possible divergence between the side walls 22.
Preferably, the inlet diffuser 12 comprises an inlet portion 25 comprising the flue-gases inlet 23, an outlet portion 27 comprising the flue-gases outlet 24 and an intermediate portion 28 comprised between the inlet portion 25 and the outlet portion 27. The outlet portion 27 is coupled to the inlet 16 of the flue-gases flowing chamber 11.
With reference to Figure 4, the inlet portion 25 is preferably composed of at least 3 sections 29a, 29b, 29c. In the first section 29a, the top wall 20 has a first inclination with respect to a direction parallel to the axis A; in the second section 29b, the top wall 20 has a second inclination with respect to a direction parallel to the axis A greater than the first inclination; in the third section 29c, the top wall 20 has a third inclination with respect to a direction parallel to the axis A greater than the second inclination. The first section 29a, the second section 29b and the third section 29c are consecutive along the direction D.
In the first section 29a, in the second section 29b and in the third section 29c, the bottom wall 19 preferably has a constant inclination with respect to a direction parallel to the axis A.
The boiler 4 comprises at least one flow rectifier assembly 30 arranged in the inlet diffuser 12 and configured to break the vortexes present in the flow through it.
In the non-limiting example described and illustrated herein, the boiler 4 also comprises an additional flow rectifier assembly 31 arranged in the inlet diffuser 12 downstream of the rectifier assembly 30 along the advancing direction D.
Preferably, the flow rectifier assembly 30 and the possible further flow rectifier assembly 31 are arranged in the inlet portion 25 of the inlet diffuser 12. In particular, the flow rectifier assembly 30 is preferably arranged in the first section 29a, whereas the further flow rectifier assembly 31 is arranged in the third section 29c.
Preferably, the flow rectifier assembly 30 and the flow rectifier assembly 31 are substantially identical and therefore the essential characteristics of the flow rectifier assembly 30 described herein are to be considered in the following valid also for the flow rectifier assembly 31.
The flow rectifier assembly 30 comprises a plurality of rectifier elements 35, each of which substantially extends from a first side wall 22 of the inlet diffuser 12 to a second side wall 22 opposite the first side wall 22.
According to a variant not illustrated, the rectifier elements substantially extend from the bottom wall 19 to the top wall 20.
With reference to Figure 3, preferably each rectifier element 35 is provided with a first end 37 coupled to the first side wall 22 of the inlet diffuser 12 and with a second end 38 coupled to the second side wall 22 of the inlet diffuser 12.
With reference to Figures 2 and 3, the rectifier elements 35 are arranged transverse to the advancing direction D.
In the non-limiting example described and illustrated herein, the rectifier elements 35 are arranged transverse also to a direction parallel to the longitudinal axis A. Preferably, the rectifier elements 35 are arranged orthogonal to a direction parallel to the longitudinal axis A.
In the non-limiting example described and illustrated herein, wherein the flue-gases flowing chamber 11 is arranged horizontal, the rectifier elements 35 are arranged horizontal.
Preferably, the rectifier elements 35 are parallel to each other.
The rectifier elements 35 are substantially identical to each other, unless there are any differences in terms of length due to the geometry of the walls to which they are coupled.
In the non-limiting example described and illustrated herein, the rectifier elements 35 are cylindrical and preferably hollow.
With reference to Figure 5, the rectifier elements 35 are aligned in a plurality of rows 40.
The rectifier elements 35 of one row 40 are staggered with respect to the rectifier elements 35 of the adjacent row 40.
Preferably, the rectifier elements 35 of a same row 40 are aligned along a direction substantially orthogonal to the advancing direction D.
In the non-limiting example described and illustrated herein, the rectifier elements 35 of a same row 40 are aligned along a direction substantially orthogonal to a direction parallel to the axis A.
Preferably, the rectifier elements 35 of a same row 40 are equidistant at a distance H. In the non-limiting example described and illustrated herein, the rectifier elements 35 of a same row 40 are distributed substantially along the entire height of the side walls 22.
Preferably, the rows 40 are equidistant from each other at a distance D.
Preferably, the distance D is lesser than the distance H. More preferably, the distance H is at least the double of the distance D.
With reference to Figures 2 and 3, the rectifier assembly 30 comprises at least one deflector 42, which extends transverse to the rectifier elements 35.
In the non-limiting example described and illustrated herein, the rectifier assembly 30 comprises a plurality of deflectors 42, preferably parallel to each other.
Each deflector 42 is transverse to the rectifier elements 35, preferably orthogonal.
Preferably, each deflector 42 is provided with a plurality of through holes 43 engaged by respective rectifier elements 35.
Preferably, the number of holes 43 is equal to the number of the rectifier elements 35 of the flow rectifier assembly 30. In this manner, all the rectifier elements 35 pass through each deflector 42.
The deflectors 42 are preferably equidistant from each other.
In the non-limiting example described and illustrated herein, the deflectors 42 substantially extend from the bottom wall 19 to the top wall 20.
Preferably, the deflectors 42 are defined by perforated plates 42.
The boiler 4 further comprises a perforated plate 45, arranged in the inlet diffuser 12 substantially transverse to the advancing direction D between the rectifier assembly 30 and the further rectifier assembly 31.
Preferably, the perforated plate 45 is housed in the second section 29b of the inlet portion 25 of the inlet diffuser 12.
Advantageously, the boiler according to the present invention is capable of improving the uniformity of the velocity profiles inflowing the flue-gases flowing chamber 11.
The tests show that the rectifier assembly 30, 31 placed in the inlet portion 25 of the inlet diffuser 12 homogenizes the velocity profiles of the gases at the inlet of the flue-gases flowing chamber 11.
Furthermore, the losses of load due to the presence of the rectifier assembly 30, 31 are contained and within the limits imposed by the design of the boiler.
Finally, it is apparent that modifications and variants can be made to the boiler and to the plant described herein without departing from the scope of the appended claims.

Claims

Heat recovery boiler comprising:
a flue-gases flowing chamber (11) extending along a longitudinal axis (A) and provided with an inlet (16) and an outlet (17);

a steam circuit (14) fed with water and extended at least partially inside the flue-gases flowing chamber (11) in order to exploit the heat of the flue-gases to generate steam;

an inlet diffuser (12) connected to the inlet (16) of the flue-gases flowing chamber (11) wherein flue-gases from a flue-gases source (9) flow in one advancing direction (D);
at least one flow rectifier assembly (30; 31) arranged in the inlet diffuser (12) and configured to break the vortexes present in the flow through it; the flow rectifier assembly (30; 31) comprising a plurality of rectifier elements (35), each of which is arranged transverse to the advancing direction (D) and substantially extends from a first wall (22) of the inlet diffuser (12) to a second wall (22) of the inlet diffuser (12) opposite the first wall (22) ; the boiler being characterised in that:
the rectifier elements (35) are aligned in at least two rows (40); the rectifier elements (35) of one row (40) being staggered with respect to the rectifier elements (35) of the adjacent row (40); and

the flow rectifier assembly (30; 31) comprises at least one deflector (42), which extends transverse to the rectifier elements (35); the deflector (42) being provided with a plurality of through holes (43), which are engaged by respective rectifier elements (35).
Boiler according to claim 1, wherein each rectifier element (35) has a first end (37) coupled to the first wall (22) of the inlet diffuser (12) and a second end (38) coupled to the second wall (22) of the inlet diffuser (12) .
Boiler according to claim 1 or 2, wherein the rectifier elements (35) are parallel to each other.
Boiler according to any one of the foregoing claims, wherein the rectifier elements (35) are essentially identical to each other.
Boiler according to any one of the foregoing claims, wherein the rectifier elements (35) are cylindrical.
Boiler according to any one of the foregoing claims, wherein the rectifier elements (35) are hollow elements.
Boiler according to any one of the foregoing claims, wherein the inlet diffuser (12) includes a bottom wall (19), a top wall (20), opposite the bottom wall (19) and two side walls (22) arranged opposite each other; each rectifier element (35) extending from one side wall (22) to the other side wall (22).
Boiler according to any one of the foregoing claims, wherein the rectifier elements (35) of a same row (40) are aligned along a direction substantially orthogonal to the advancing direction (D).
Boiler according to any one of the foregoing claims, wherein the rectifier elements (35) of a same row (40) are distributed substantially along the entire height of the side walls (22).
Boiler according to any one of the foregoing claims, wherein the deflector (42) is substantially orthogonal to the rectifier elements (35).
Boiler according to any one of the foregoing claims, comprising an additional flow rectifier assembly (31; 30) arranged downstream of the flow rectifier assembly (30; 31) along the advancing direction (D).
Boiler according to claim 11, including a perforated plate (45) arranged substantially transverse to the advancing direction (D) downstream of the flow rectifier assembly (30; 31) along the advancing direction (D) and preferably upstream of the additional flow rectifier assembly (31; 30).
Steam generation thermal plant comprising at least one heat recovery boiler (4) as claimed in any one of the previous claims.