U.S. patent application number 13/321151 was filed with the patent office on 2012-03-22 for heat recovery apparatus.
This patent application is currently assigned to S. TRA. G. I. E. S.R.L.. Invention is credited to Gabriele Comodi.
Application Number | 20120067549 13/321151 |
Document ID | / |
Family ID | 41560898 |
Filed Date | 2012-03-22 |
United States Patent
Application |
20120067549 |
Kind Code |
A1 |
Comodi; Gabriele |
March 22, 2012 |
HEAT RECOVERY APPARATUS
Abstract
The subject of the disclosed invention is a heat generator (3)
for thermal energy production connected through a conveyor (4; 41,
4101, 42, 43, 4201, 4202, 4203, 4204, 4205) to one or multiple heat
sources (2). The hot gases (F1, F2) generated by said one or
multiple heat sources (2) are carried through said conveyor (4) to
said heat generator (3) for recovery of their enthalpy content.
Inventors: |
Comodi; Gabriele; (Ancona,
IT) |
Assignee: |
S. TRA. G. I. E. S.R.L.
Ancona
IT
|
Family ID: |
41560898 |
Appl. No.: |
13/321151 |
Filed: |
May 18, 2010 |
PCT Filed: |
May 18, 2010 |
PCT NO: |
PCT/IB2010/001174 |
371 Date: |
December 7, 2011 |
Current U.S.
Class: |
165/104.11 |
Current CPC
Class: |
F28F 9/26 20130101; F24H
9/0031 20130101; F28D 7/163 20130101; F24H 1/285 20130101; F28D
21/0017 20130101; F28D 7/0066 20130101; F28D 21/0003 20130101 |
Class at
Publication: |
165/104.11 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2009 |
IT |
AN2009A000023 |
Claims
1. Heat generator (3) for production of thermal energy including:
at least one furnace (31), where combustion occurs, one heat
exchanger (32; 3201, 3101, 3302, 3303), where combustion products
are cooled, and a flue (36) for their discharge into the
atmosphere, characterized in that it is connected via a conveyor
(4; 41, 4101, 42, 43, 4201, 4202, 4203, 4204, 4205) to one or
multiple heat sources (2), said conveyor (4) carrying hot gases
(F1, F2) discharged by said one or multiple heat sources (2) to
said heat generator (3) to recover enthalpic content.
2. Heat generator (3) according to the previous claim characterized
in that said hot gases (F1, F2) discharged by said one or multiple
heat sources (2) are combustion gases (F1), said combustion gases
(F1) being sent via said conveyor (4; 41, 4101, 42, 43, 4201, 4202,
4203, 4204, 4205) to transfer heat to a part (3201) of said
exchanger (32; 3201, 3101, 3302, 3303) that is therefore capable to
be used only for cooling said combustion gases (F1).
3. Heat generator (3) according to any previous claim characterized
in that it is a fire-tube boiler (3) for production of steam and/or
hot water and/or diathermic oil, said heat exchanger (32; 3201,
3101, 3302, 3303) thus being a multi-pipe type (33), arranged in
one or multiple fume circuits (3101, 3302, 3303) and designed to
transfer heat to water (A) contained in the outer container (38),
with each extremity of said container (38) being fitted with a pipe
plate (3801) for insertion of said pipes (33) and said furnace
(31).
4. Heat generator (3) according to the previous claim characterized
in that said conveyor (4; 41, 4101, 42, 43, 4201, 4202, 4203, 4204,
4205), designed to carry said combustion gases (F1) from said one
or multiple heat sources (2) to said heat generator (3), comprises:
an outer part (41) connected to said one or multiple heat sources
(2) designed to collect said combustion gases (F1) an inner part
(42) devised to couple, at its opening (4201), to said pipe plate
(3801) so as to intercept one or more pipes (33) of said heat
exchanger (32; 3201, 3101, 3302, 3303), said one or more pipes (33)
identifying the part (3201) of said heat exchanger (32; 3201, 3101,
3302, 3303) dedicated to cooling said combustion gases (F1)
5. Heat generator (3) according to the previous claim characterized
in that said inner part (42) is capable of being shifted towards
said pipe plate (3801), so as to intercept said one or more pipes
(33), thus identifying the part (3201) of said heat exchanger (32;
3201, 3101, 3302, 3303) dedicated to cooling said combustion gases
(F1), or is capable of being moved away from said pipe plate
(3801), so that all fume pipes (33) of said heat exchanger (32;
3201, 3101, 3302, 3303) convey exclusively the products of the
combustion occurring in said furnace (31) of said generator
(3).
6. Heat generator (3) according to the previous claim characterized
in that said inner part (42) translates axially with respect to
said external part (41) in which it is partially inserted, said
internal (42) and external parts (41) being joined through a
telescopic coupling (5; 4101, 4205).
7. Heat generator (3) according to the previous claim characterized
in that said telescopic coupling (5; 4101, 4205) has circular
sections (4101, 4205), said inner part (42) thus being capable of
rotation with respect to said external part (41), in which it is
partially inserted.
8. Heat generator (3) according to any previous claim characterized
in that the centre of said opening (4201) is on the same axis as
said external part (41), said opening (4201) having such a section
as to define, by effect of its rotation, said part (3201) of the
heat exchanger (32; 3201, 3101, 3302, 3303) dedicated to cooling
said combustion gases (F1).
9. Heat generator (3) according to any one of the previous claims
excepting claim 8, characterized in that the centre of said opening
(4201) of said inner part (42) is offset with respect to said
external part (41), said opening (4201) defining, by effect of its
rotation, said part (3201) of the heat exchanger (32; 3201, 3101,
3302, 3303) dedicated to cooling said combustion gases (F1).
10. Heat generator (3) according to any previous claim
characterized in that said conveyor (4; 41, 4101, 42, 43, 4201,
4202, 4203, 4204, 4205) is housed in and passes through the
inspection hatch (37) of said heat generator (3), said external
part (41) of said conveyor (4; 41, 4101, 42, 43, 4201, 4202, 4203,
4204, 4205) being hermetically coupled to said inspection hatch
(37).
11. Heat generator (3) according to any previous claim
characterized in that said conveyor (4; 41, 4101, 42, 43, 4201,
4202, 4203, 4204, 4205) also comprises an interception organ (43)
designed to exclude said one or multiple heat sources (2) from said
heat generator (3), said interception organ (43) being specifically
a butterfly valve located on said external part (41).
12. Heat generator (3) according to any previous claim
characterized in that said part (3201) of the heat exchanger (32;
3201, 3101, 3302, 3303), intercepted and defined by said conveyor
(4; 41, 4101, 42, 43, 4201, 4202, 4203, 4204, 4205), includes one
or more pipes (33) of the second (3302) and/or third (3303) fumes
circuit.
13. Heat generator (3) according to any previous claim
characterized by being installed and in operation or already on the
market, said inspection hatch (37), in which said conveyor (4; 41,
4101, 42, 43, 4201, 4202, 4203, 4204, 4205) is housed and passes
being an auxiliary hatch to replace the standard hatch on said heat
generator (3).
14. Heat generator (3) according to any previous claim
characterized in that said hot gases (F1, F2) discharged by said
one or multiple heat sources (2) also include cooling and/or
ventilation air (F2) heated by cooling of various devices of said
one or multiple heat sources (2), said cooling air (F2) being used
to support combustion in said furnace (31).
15. Heat generator (3) according to any previous claim
characterized in that said one or multiple heat sources (2) consist
in engines and/or low efficiency heat generators and/or cooling
batteries.
16. A conveyor (4; 41, 4101, 42, 43, 4201, 4202, 4203, 4204, 4205)
for transport of hot gases (F1, F2) from one or multiple heat
sources (2) to a heat generator (3) for recovery of enthalpic
content, according to one or more of the previous claims.
17. Apparatus for heat recovery (1) including a heat generator (3)
and one or multiple heat sources (2), said generator (3) and said
one or multiple heat sources (2) being interconnected by a conveyor
(4; 41, 4101, 42, 43, 4201, 4202, 4203, 4204, 4205), according to
one or more of the previous claims.
18. Apparatus for heat recovery (1) according to the previous claim
characterized in that it is a cogeneration apparatus (1), said one
or multiple heat sources (2) being an engine (2) for electrical
and/or mechanical power production.
19. Recovery method for a heat generator (3) of the enthalpic
content of hot gases (F1, F2) discharged by one or multiple heat
sources (2), according to any of the previous claims characterized
in that said one or more pipes (33), which are designed to be
intercepted by said conveyor (4; 41, 4101, 42, 43, 4201, 4202,
4203, 4204, 4205), and which define said part (3201) of said heat
exchanger (32; 3201, 3101, 3302, 3303) dedicated to cooling said
combustion gases (F1), are selected manually, the physical
parameters characterizing said combustion gases (F1) being
essentially stable over time, said physical parameters being
specifically flow rate and/or temperature.
20. Recovery method for a heat generator (3) of the enthalpic
content of hot gases (F1, F2) discharged by one or multiple heat
sources (2), according to any one of the previous claims excluding
claim 19 characterized in that said one or more pipes (33), which
are designed to be intercepted by said conveyor (4; 41, 4101, 42,
43, 4201, 4202, 4203, 4204, 4205) and which define part (3201) of
said heat exchanger (32; 3201, 3101, 3302, 3303) dedicated to
cooling said combustion gases (F1), are automatically selected
through special sensors by an electronic control unit based on the
variation, instant for instant, of the physical parameters of
combustion gases (F1), said physical parameters being specifically
flow rate and/or temperature.
Description
[0001] The present invention refers to an apparatus for recovering
thermal energy from the exhaust fumes and gases of heat engines and
from the cooling and ventilation air and/or any of the components
or auxiliary circuits of the same plants, or of other plants.
[0002] In particular, the invention refers to heat generators
adapted to serve as heat recovery apparatuses.
[0003] More particularly, said heat generators are fire-tube
apparatuses.
[0004] The invention is especially useful to realize electrical and
thermal energy cogeneration plants, particularly in the micro
cogeneration sector.
[0005] Cogeneration (or "combined production") is essentially based
on using the heat generated by the electricity production phase of
thermoelectric generators; such "residual" energy can be used as a
heat source for heating buildings or for production and industrial
purposes.
[0006] A major advantage of micro cogeneration is that it enables
widespread, small-scale distributed production of electrical energy
for households, the tertiary sector and small-sized industries,
whose power requirements are relatively modest.
[0007] The spread of micro cogeneration has been hampered by the
difficulty of meeting minimum cost per unit of power, yield,
reliability and efficiency requirements in small-sized devices. As
a consequence, current cogeneration systems range from 100-300 kW
to several MW.
[0008] The micro cogeneration market offers substantially two
options that are based on the same energy generation concept, but
on two different types of prime mover. In particular, micro gas
turbines can be employed in the 50 to 100 kW range, whereas
alternative internal combustion engines with a Diesel or,
preferably, an Otto cycle can be used for smaller plants.
[0009] The thermal energy produced by the functioning of a prime
mover (be it an internal combustion engine or a micro gas turbine)
is partly dissipated in the external environment by radiation;
while this fraction can effectively be reduced, most of the thermal
energy is transferred to the combustion gases (whose temperature in
fact ranges from 350 to 600.degree. C.) discharged to the flue and
to the cooling air of various engine components and auxiliary
circuits.
[0010] Heat is not usually recovered from cooling air, essentially
due to its low enthalpy and convective heat transfer coefficient,
which would require exchangers endowed with large exchange
surfaces, adversely affecting the cost/benefit ratio of the
cogenerator. Only rarely is cooling air harnessed to heat water,
generally in alternative internal combustion engines.
[0011] In contrast, devices have already been developed to recover
heat from prime mover exhaust fumes, despite their not very high
enthalpy and, especially, the risk of acid condensation during
cooling.
[0012] Such devices are usually fitted downstream of the prime
mover; they may be exchangers (also known as recuperators), which
use the heat of the combustion fumes, for example to preheat the
combustion air, or recovery furnaces, where the fumes are further
burned or merely cooled via heat exchangers, preferably dedicated
to production of steam, hot water or superheated water.
[0013] As an example, according to document GB 2 271 171 exhaust
hot gases, discharged by one or multiple heat sources, are cooled
on the whole thermal exchange surface of the heat exchanger of a
heat generator (in this case, a fire-tube boiler) while in the
document U.S. Pat. No. 4,313,399 exhaust hot gases are used as
comburent in the combustion chamber of the heat generator, if
sufficiently rich in oxygen.
[0014] However, apparatuses for the recovery of the enthalpy of
prime mover combustion gases and fumes have a major drawback: their
close integration with the engine itself.
[0015] As a consequence, malfunction of the prime mover or the heat
recovery apparatus can compromise the overall efficiency of the
cogeneration system. In addition, separate maintenance of the
engine and the heat recovery apparatus is difficult, since it
generally requires also the shutdown of the component functioning
correctly.
[0016] Moreover regulation devices are needed, to provide the
thermal energy recovered at the temperature required by the
user.
[0017] Altogether, current heat recovery apparatuses are relatively
expensive in terms of the gains they provide (recovery of prime
mover thermal loss).
[0018] Finally, it is not always simple to transport the heat
energy thus recovered to possible users.
[0019] If, as noted above, the enthalpy of the cooling air of a
prime mover and its auxiliary circuits is difficult to reuse, its
recovery from the various heat sources of an industrial plant, e.g.
the cooling system of a plastic stamping plant; hot air from
industrial painting plants; or exhaust fumes from elderly, poorly
efficient industrial furnaces and boilers, is even harder.
[0020] Clearly, also in these cases the main issue is the
cost/benefit ratio, since ad hoc exchangers and heat energy
transport plants are needed for each heat source.
[0021] A first object of the disclosed invention is to devise a
simple and economical heat recovery method in relation to the
amount of thermal and electrical power involved.
[0022] A second object of the invention is to devise a heat
recovery method characterized by low pollutant emissions and
environmental impact.
[0023] An additional object of the invention is to devise a heat
recovery method characterized by high flexibility in terms of the
amount of heat to be recovered.
[0024] A further object of the disclosed invention is to devise a
heat recovery method characterized by high flexibility in terms of
the number and type of plants from which heat can be recovered.
[0025] A still further object of the present invention is to devise
a method to integrate the heat recovery and production systems with
electricity and/or mechanical power production plants.
[0026] Another object of the invention is to devise high
flexibility means to integrate a prime mover and a fire-tube boiler
in terms of the amount of electrical power to be integrated.
[0027] Additional objects and advantages of the disclosed invention
are better demonstrated by the following detailed description of a
preferred embodiment, made in line with the patent claims and with
reference to attached diagrams reported purely by way of example
and not intended to limit the invention, where:
[0028] FIG. 1 is a schematic perspective view of a heat generator
according to the prior art;
[0029] FIG. 2 is a block diagram of a heat recovery apparatus
according to the disclosed invention;
[0030] FIGS. 4a, 4b, and 4c report three side and front
cross-sections of the apparatus illustrated in FIG. 2, with
emphasis on the heat generator according to a first variant of the
invention.
[0031] FIGS. 5a and 5b are two side and front cross-sections of the
apparatus shown in FIG. 2, with special reference to the heat
generator, according to an additional variant of the invention;
[0032] FIG. 5c reports a detail of the variant shown in FIGS. 5a
and 5b.
[0033] In FIG. 2 of the attached diagrams 1 indicates overall the
heat recovery apparatus, the subject of the invention, which
includes one or multiple generic heat sources 2 and a heat
generator 3.
[0034] As noted above, said generic heat sources 2 can be
electrical and/or mechanical power generators, such as internal
combustion engines, micro gas turbines, steam turbines, fuel cells;
simpler heat sources such as low-efficiency heat generators, whose
fumes can still be used to extract thermal energy; and even simpler
devices such as heat exchanger batteries of cooling systems of
plants such as plastic stamping or extrusion machines.
[0035] During operation, said heat sources 2 emit heat
substantially as hot gases, i.e. combustion gases F1 and/or cooling
and ventilation air F2 heated by the cooling of various types of
equipment.
[0036] Said heat sources 2 can be for instance: [0037] internal
combustion engines and micro gas turbines, where heat is generated
both as combustion gases F1 and as auxiliary circuit cooling and
ventilation air F2, [0038] low-efficiency heat generators, where
heat is generated in the form of combustion gases F1, [0039] heat
exchanger batteries of cooling systems, where heat is generated as
cooling and ventilation air F2.
[0040] Hot gases F1 and F2, generated by said heat sources 2, are
often insufficient in amount and/or temperature for heat recovery
to be feasible and/or economical through individual recovery
apparatuses.
[0041] FIGS. 1 and 2 schematically show the combustion chamber (or
furnace) 31, the heat exchanger 32, and the flue 36 of the heat
generator 3.
[0042] According to the disclosed invention the enthalpy of the hot
gases F1 and F2 issuing from the heat source 2 is recovered by said
generator 3.
[0043] More precisely, the combustion gases F1, whose temperature
is sufficiently high, are sent to the exchanger 32 to transfer
heat, whereas the cooling air F2 is used in the same generator 3 as
combustion air for the furnace 31.
[0044] Other operating conditions are not excluded, such as those
where the cooling air F2 is sufficiently hot to be treated like the
combustion gases F1 and is accordingly sent to the exchangers 32,
or vice versa, conditions where combustion gases F1, similar to
cooling air F2 due to low temperature or high oxygen content, need
to be sent to the furnace 31 together with the combustion air,
provided they do not adversely affect oxygen combustion.
[0045] The heat generator 3 is preferably a type for production of
steam and/or hot water and/or diathermic oil; in particular, it is
a fire-tube boiler (see FIG. 1). Since the technology and operating
principles of the fire-tube boiler 3 (henceforth the boiler) are
well known, a short description will suffice here.
[0046] The features of the fire-tube boiler 3 shown in the
schematic view of FIG. 1 and in FIGS. 4a through 5c are a furnace
31, usually cylindrical, where combustion occurs, and a number of
pipes 33, constituting overall the exchanger 32, carrying the
exhaust gases. Said pipes 33 are arranged into bundles (or fume
circuits) in which the gases course, passing through the boiler 3
once or multiple times. The furnace 31 and pipes 33 are surrounded
by water A (in liquid and steam state); the water is contained in a
cylindrical vessel 38 fitted at either end with pipe plates 3801
for the insertion of the furnace 31 and pipes 33.
[0047] More in particular (see for instance FIG. 4a), the exhaust
gases issuing from the furnace 31, which coincides with the first
fume circuit 3101, pass through a first inversion chamber 34; from
said chamber they are sent, confined above by a partition 3401,
into the pipes 33 of the second fume circuit 3302, and from there
to a second inversion chamber 35, which is usually found on the
front of the boiler 3 (note the direction of the arrows F on
various pipes 33 in FIG. 1), and finally, sufficiently cooled after
coursing through the third fume circuit 3303, they are conveyed to
the flue 36.
[0048] A hatch 37 for inspection and maintenance, commonly found on
the front of the boiler 3, is schematically drawn in FIGS. 4a
through 5c.
[0049] Upstream of the furnace 31 the boiler 3 also includes at
least a burner and the respective fan (or blower), to supply
combustion air (not shown in the figures).
[0050] All known components of the boiler 3 have now been
described.
[0051] In the disclosed invention a conveyor 4 carries said
combustion gases F1 to at least one part of the exchanger 32, to
recover their thermal energy.
[0052] The inspection hatch 37 is modified compared with the prior
art, to accommodate the conveyor 4 passing through it.
[0053] Said conveyor 4 is characterized by an outer part 41
connected directly, or indirectly through ducts, to said one or
multiple heat sources 2, to collect their combustion gases F1, and
by an inner part 42, which is designed to couple to one or more
pipes 33 of the heat exchanger 32 of the fire-tube boiler 3, in
particular one or more pipes 33 of at least the third fume circuit
3303, and whose opening 4201 presses against the front pipe plate
3801.
[0054] The internal part 42 is designed to rotate and translate
axially with respect to the outer part 41, where it is partially
inserted, to allow coupling of the conveyor 4 to one or multiple
pipes 33, as required by the flow rate and temperature of the
combustion gases F1, or to prevent the conveyor 4 from interfering
with said pipes 33 if no combustion gases F1 from which energy can
be recovered are present.
[0055] Therefore, as shown in FIGS. 4a to 4c, said conveyor 4 is
preferably a telescopic conduit consisting of an outer part 41
coupled hermetically to the inspection hatch 37, and of an inner
part 42 capable of rotation and axial translation with respect to
the outer part 41, where it is partially inserted, via a telescopic
coupling 5 (schematically represented in the enclosed figures). In
particular, said rotation is enabled by the circular conduit tracts
4101 and 4205 of said joint 5, to which the outer 41 and inner part
42 of the conduit 4 are coupled (see in particular FIG. 5c).
[0056] As an example, which in no way limits the scope of the
invention, the opening 4201 of the mobile internal part 42 is
preferably elliptical and/or circular.
[0057] Axial translation of the inner part 42 with respect to the
fixed external part 41 enables the opening 4201 to approach the
pipe plate 3801 within the inversion chamber 35, to intercept said
one or more pipes 33, whereas its rotation selects the pipes 33 of
said plate 3801 that will carry the combustion gases F1 of the heat
source 2, and consequently the number of passes of the combustion
gases F1 through the heat generator 3.
[0058] As depicted in FIGS. 4a to 4c, and 5a to 5c, said pipes 33,
intercepted by said opening 4201, therefore define the part 3201 of
the heat exchanger 32 of the boiler 3 dedicated to cooling the sole
combustion gases F1 of said one or multiple heat sources 2.
[0059] For instance, as shown in FIG. 4a, the conduit 4 is capable
of connecting to a suitable number of pipes 33 belonging solely to
the third fume circuit 3303, whereas, as clearly shown in FIGS. 4b
and/or 4c, the inner part 42 of the conduit 4, as a result of its
rotation, can connect simultaneously to multiple pipes 33 of the
third circuit 3303 and to at least one pipe 33 of the second
circuit 3302. In the case depicted in FIG. 4a, the combustion gases
F1 of the heat source 2 therefore course through the heat generator
3 just once, via the third fume circuit 3303, whereas in the
example illustrated in FIG. 4b and/or 4c, part of said combustion
gases F1 pass through the boiler 3 three times.
[0060] In fact, as shown in FIGS. 4b and 4c, part of said gases F1
pass through the boiler 3 in front to back direction, through one
or more pipes 33 of the second fume circuit 3302, their direction
is then reversed in the inversion chamber 34, whence they pass
through those pipes 33 of the second fume circuit 3302 that are not
intercepted by the opening 4201 of the conduit 4, and subsequently
they pass through the third and last fume circuit 3303, before
finally going to the flue 36. Clearly, the pipes 33 of any fume
circuit that are not intercepted by the opening 4201 continue to
carry the products of the internal combustion of the boiler 3, or a
mixture of said products and said combustion gases F1 (like the
pipes 33 of the second circuit 3302, not exclusively dedicated to
carrying the same combustion gases F1, shown in the example of FIG.
4b) along the direction of the arrows F and of their vector
representation (depicted in the enclosed figures, where "x"
indicates a vector pointing into the page and ".cndot." a vector
pointing out of the page).
[0061] Similar considerations also apply to the variant shown in
FIGS. 5a to 5c, which differs from the previous configuration by
the circular (rather than generically elliptical) section of the
opening 4201 of the conduit 4.
[0062] In the latter case, for the rotation of the inner part 42 of
the conduit 4 to serve the purposes described above, the centre of,
the opening 4201 must be offset with respect to the centre of the
fixed external part 41.
[0063] In FIG. 5c, the inner part 42 has a first tract 4202, whose
axis is parallel to the fixed outer part 41, and another tract 4203
(designed to couple through its own opening 4201 to the pipe plate
3801), whose axis is parallel to the first; the two tracts 4202 and
4203 are connected through a junction 4204.
[0064] The conduit 4 is completed by an interception organ 43, e.g.
a butterfly valve 43, positioned in the fixed part 41, designed to
exclude the heat source 2 from the boiler 3 in case of malfunction
or maintenance, or in the event that the heat recovery apparatus 1
of the disclosed invention is operated as a traditional fire-tube
boiler 3.
[0065] In the latter case the valve 43 must therefore be closed,
while the mobile inner part 42 of the conduit 4 is retracted inside
the fixed part 41, so that all the pipes 33 of the boiler 3 carry
exclusively the products of its internal combustion. One or more
magnets (not shown) can also be fitted in close proximity to the
opening 4201 of the conduit 4, for an enhanced coupling of the
conduit 4 and the pipe plate 3801, and thus a perfect seal.
Alternatively, any means known in the prior art can be used to
press the opening 4201 against the pipe plate 3801. According to
possible variants of the invention, an additional fan (not shown)
can be applied to the flue 36, to enhance circulation of the
combustion gases F1 through the fire-tube boiler 3, by forcing them
through said pipes 33 of its exchanger 32.
[0066] The above description clearly demonstrates that the
appropriate number of pipes 33 intercepted by the conduit 4 and the
number of passes of the combustion gases F1 through the boiler 3
depend on multiple factors such as the temperature of the
combustion gases F1 at the exit from the one or multiple heat
sources 2, their amount and, more generally, their thermal
energy.
[0067] The configurations shown in FIGS. 4a and 5a (envisaging a
single pass of the combustion gases F1 through the boiler 3) are
preferable where the thermal power dissipation (and/or temperature)
of the combustion gases F1 is low, whereas those shown in FIGS. 4b
and 4c, 5b, or any other configuration envisaging three passes of
the gases F1 through the boiler, are preferable with higher values
of thermal power dissipation. In any case, the number of pipes 33
intercepted by the conduit 4 and, consequently, the number of
passes of the gases F1 through the boiler 3, are aimed to achieve
the lowest possible temperature of the combustion gases F1 at the
exit from the boiler 3.
[0068] If the physical parameters (i.e. temperature and flow rate)
of the combustion gases F1 are expected to be substantially stable
over time, the configuration (particularly the rotation angle of
the mobile internal part 42 of the conduit 4) can be selected
manually.
[0069] However, it is preferable to have an electronic control unit
selecting the most appropriate configuration of the conduit 4 in
response to the changes in said physical parameters, which are
detected through special sensors.
[0070] Clearly, the larger the portion 3201 of the heat exchanger
32 dedicated to the combustion gases F1, the smaller the thermal
power that can be supplied to the furnace 31, but modulation of
such power is automatically provided by control means with which
the heat generator 3 is usually endowed. In fact the power supplied
to the furnace is modulated by the user's demand for heat energy,
which is met with lower furnace 31 loads if combustion gases F1 are
present.
[0071] As noted above, the one or multiple heat sources 2 may
entail the possibility of recovering in the boiler 3, besides the
combustion gases F1, the thermal energy of the cooling and/or
ventilation air F2, for instance of engine components and auxiliary
circuits of the heat source 2 itself, which would otherwise be
dispersed in the environment.
[0072] According to a preferred and advantageous embodiment,
cooling and/or ventilation air F2, warmer than the ambient
temperature (from 60.degree. C. to 90.degree. C.), is sent by known
means directly to the furnace 31 of the boiler 3 and used as
combustion air. From this viewpoint the heat source 2 therefore
serves as a preheater unit of the combustion air for the internal
combustion of the boiler 3. Recovery of such additional heat energy
in the boiler 3, coupled to the heat recovered from the combustion
gases F1, therefore increases the overall efficiency of the heat
recovery apparatus 1, which is subject of the invention.
[0073] In fact it is well known that the efficiency of a boiler 3
for production of hot water and/or steam is a function of the
temperature of inlet air in the burner of the furnace 31 and of the
exhaust fumes: the closer the inlet air temperature to the gas
temperature at the flue 36, the better the thermal yield of the
boiler 3 and therefore of the heat recovery apparatus 1
overall.
[0074] Clearly, numerous additional variants of the disclosed heat
recovery apparatus 1 are possible, to the person skilled in the
art, without exceeding the scope of the appended claims; moreover
the various components described above can be replaced with
technically equivalent elements upon practical realization of the
invention.
[0075] The heat source 2 is preferably a prime mover for electrical
energy production. Even more preferably such prime mover 2 is, as
noted above, an internal combustion engine or a micro gas turbine,
two well-established and reliable technologies that require no
further description. The heat recovery apparatus 1 according to
this preferred embodiment is therefore a cogeneration plant for
combined electrical and thermal power production, to which all the
above considerations apply.
[0076] Compared with the prior art, in the present case the prime
mover 2 can lack the traditional integrated recuperator, since it
is connected (through said conveyor 4) to the boiler 3, where the
heat that would otherwise be dissipated as combustion gases F1 and
cooling and/or ventilation air F2 is efficiently recovered.
[0077] According to another embodiment the prime mover 2 (or in
general the heat source 2) can be joined, through the telescopic
conduit 4, to the back of the fire-tube boiler 3, rather than at
the level of the inspection hatch (suitably modified to house said
conduit 4) as described above.
[0078] According to a highly simplified variant of the cogeneration
apparatus 1 (or in general the heat recovery apparatus 1), and
particularly of the conveyor 4, the mobile inner part 42 is capable
only of axial translation with respect to the fixed part 41, not
also of rotation. Such configuration is especially practical, as
noted above, when the physical parameters of the combustion gases
F1 are substantially constant over time and the part 3201 of the
heat exchanger 32 dedicated to said combustion gases F1 can be
selected manually.
[0079] In a further simplified variant the conveyor 4 includes only
the external part 41 (henceforth, for the sake of simplicity, the
conduit 41), hermetically coupled to the inspection hatch 37 but
capable of axial translation to connect to the pipes 33 of the
exchanger 32 of the boiler 3 dedicated to said combustion gases
F1.
[0080] It is therefore clear that the apparatus for heat recovery 1
described above in its preferred embodiment and variants can
achieve the intended goals, particularly heat recovery from diverse
types of machines in a simple and economical way. For instance, in
the case where the heat source 2 is a prime mover (even though the
reasoning also applies to the more general case of any alternative
heat source 2), the possibility to dedicate part of the heat
exchanger 32 of the boiler 3 to cooling the sole combustion gases
F1 of said prime mover 2 and to recover cooling and/or ventilation
air F2 significantly enhances the overall efficiency of the
cogeneration apparatus 1 and allows nearly total recovery of its
thermal loss. It is also clear that integration of an existing
boiler 3 with an engine 2 suitable for electricity generation can
be achieved with a modest investment by any user, who can select
the most appropriate size for their level of consumption. Said
cogeneration apparatuses 1 are therefore capable of meeting also a
user demand characterized by high thermal and low electrical power
production. This is easily achieved by replacing the standard hatch
37 of the fire-tube boiler 3 with an additional hatch capable of
housing and supporting the conveyor 4.
[0081] Integration of a micro gas turbine or an internal combustion
engine with an existing or a commercial boiler 3 also significantly
reduces their specific cost, since it obviates the need for closely
integrated internal devices to recover exhaust fumes (and/or
cooling air), as in the known art.
[0082] The disclosed cogeneration apparatus 1 is also characterized
by a longer service life than traditional systems, to the extent
that it enables separate maintenance or replacement of the prime
mover 2 and the fire-tube boiler 3, where needed; in addition,
repair or replacement of either component does not involve the
interruption, even temporary, of electrical and/or thermal power
generation.
[0083] Finally, the heat generator 3 can also be a water-tube
boiler.
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