WO1985000200A1

WO1985000200A1 - Energy-producing installation

Info

Publication number: WO1985000200A1
Application number: PCT/SE1984/000228
Authority: WO
Inventors: Alvar MÖLDRI
Original assignee: Interflame Ab
Priority date: 1983-06-23
Filing date: 1984-06-18
Publication date: 1985-01-17
Also published as: KR850000591A; DK57985D0; SE440937B; SE8303604D0; JPS60501670A; SE8303604L; DK57985A; EP0179765A1

Abstract

In an energy-producing installation comprising a diesel engine (12), a steam generator (13) and a combustion chamber assembly (11) which is connected between the exhaust discharge system of the diesel engine and the steam generator for heating the engine exhaust gases by means of an oil burner (15) utilizing the oxygen of the exhaust gases, the combustion chamber assembly has an exhaust gas intake (14) subdivided into a plurality of intake passageways (21, 25, 29, 32) arranged in parallel-flow relation. Of these, two intake passageways (21, 25) supply exhaust gases serving as primary and secondary combustion air and a further one (29) supplies exhaust gases to a cooling passage (27) which surrounds a first mixing chamber (24) for combustion gases and opens into a second mixing chamber (30) which also receives the combustion gases from the first mixing chamber (24) and exhaust gases supplied through a still further intake passageway (32). The volume flow rate in the cooling passage (27) is kept substantially constant, regardless of the total volume flow rate of the exhaust gases.

Description

Energy-producing installation

This invention relates to an energy-producing installa¬ tion comprising a combustion engine discharging oxygen- containing exhaust gases, a steam generator connected to the exhaust gas discharge system of the combustion engine, and a combustion chamber assembly which forms part of or is disposed in an exhaust gas conduit system extending between the combustion engine and the steam generator and which includes an oil burner, fuel oil being burned in the combustion chamber assembly by means of the oxygen containe in the exhaust gases. Although not so limited, the installa¬ tion according to the invention is particularly adapted for use on ships having a diesel engine as main engine.

Ships propelled by a diesel engine often have a steam generator utilizing the exhaust gases of the diesel engine as a heat source; the exhaust gases have a temperature of 300 to 350 C as they leave the engine.

The steam generator, the so-called exhaust gas boiler, is dimensioned to meet the ship's demand for steam for the majority of the periods in which steam is required. In order that the demand for steam may be met during peak periods of steam consumption, the ships are equipped with an additional, separate steam generator which is used only when the capacity of the exhaust gas boiler is insufficient. However, a separate steam generator means a significant additional cost for the steam-producing system and, moreover, its start-up time is inconveniently long.

It has been proposed, in order that the separate, steam generator may be omitted and a very rapid increase of the steam production in peak periods may be possible, to increase, by means of oil-fired heating apparatus, the exhaust gas temperature in the flow path between the engine and the exhaust gas boiler. Endeavours aiming at implementing this proposal have not been successful, however.

An object of the invention is to provide, in an energy-producing installation of the kind referred to above, means whereby the required increase of the tempera¬ ture may be brought about in an economical and reliable manner even when the exhaust gas output of the engine varies. This object is achieved according to the invention by embodying in the combustion chamber assembly the features recited in claim 1. The invention is described in greater detail herein¬ after with reference to the accompanying drawings which diagrammatically show an installation embodying the invention.

FIG. 1 is a diagrammatic elevational view of the combustion chamber assembly, the connection of this assembly with the exhaust gas discharge system of the combustion engine and with the exhaust gas boiler only being outlined;

FIG. 2 is a longitudinal sectional view of the co bus- tion chamber assembly.

The combustion chamber assembly illustrated in the drawings forms part of an energy-producing installation which also comprises a diesel engine constituting the main engine of a ship, and a steam generator heated by exhaust gas, i.e., a so-called exhaust gas boiler. The diesel engine and the exhaust gas boiler are conventional and are not, therefore, shown in detail but only in fragmentary outline. The combustion chamber assembly is generally designated by the numeral 11 while the diesel engine and the exhaust gas boiler are designated by the numerals 12 and 13, respectively (FIG. 1). As is evident from FIG. 1, the combustion chamber assembly 11 forms part of or is disposed in an exhaust gas conduit system extending between the diesel engine 12 and the exhaust gas boiler 13.

An exhaust gas intake 14 of the combustion chamber assembly 11 receives substantially all of the oxygen-contai ing exhaust gases discharged from the diesel engine which are at a temperature of, for example, slightly above 300°C. Within the combustion chamber assembly the exhaust gases are heated by the combustion of fuel oil by means of a burner 15 which in the present case is a burner of the type using low-pressure air for atomizing fuel oil. Fuel oil is fed to the burner through a conduit 16, and atomizin air (primary air) is supplied by a fan 17. The exhaust gases from the diesel engine 12 are deflected 90 beforeϋ- they are fed to the exhaust gas boiler 13 at a temperature which may vary according to circumstances but which normally does not exceed 470-480 C. Apart from the relati¬ vely small amount of atomizing air, the oxygen needed for the combustion is supplied with the exhaust gases.

FIG. 2 shows the construction of the combustion chamber assembly 11 in greater detail. Generally, the part of the combustion chamber assembly where the heating of the exhaust gases takes place is shaped as a circular cylindrical body at one end of which the burner 15 is coaxially mounted and the other end of which forms an outlet for the heated exhaust gases. The exhaust gases coming from the engine 12 are fed substantially radially into the cylindrical body at the first-mentioned end.

The burner 15 essentially is a conventional air- atomizing burner including a circular cylindrical ceramic combustion cup 19 at the nozzle end. This cup is open towards the outlet of the combustion chamber assembly and at its open end is surrounded in spaced relation by an annular ceramic secondary air cup 20 which is likewise open towards the outlet and communicates with the exhaust gas intake 14 through an intake passageway 21. An annular ceramic wall 22 surrounds in spaced relation the portion of the secondary air cup 20 facing the outlet of the combustion chamber assembly and forwardly connects to an annular wall 23 of sheet steel to define therewith a first mixing chamber 24. At its end closest to the burner 15 the first mixing chamber 24 communicates with an intake passageway 25 of the exhaust gas intake 14.

The annular wall 23 is surrounded in spaced relation by a jacket 26 of sheet steel and forms with this jacket an annular passage 27 the end of which closest to the burner communicates with a further intake passageway 29 of the exhaust intake 14. The passage 27 is of constant width throughout its axial length and opens unobstructedly into a second mixing chamber, which is directly connected with the end of the first mixing chamber remote from the first mixing chamber 24. The second mixing chamber 30 is defined by an annular wall 31 one end of which surrounds in spaced relation the end portion of the annular wall 26 remote from the burner and the other end of which forms the outlet of the combustion chamber assembly.

The annular passage between the annular walls 26 and 31 communicates with a still further intake passageway 32 of the exhaust intake 14. Within this intake passageway 32 a damper device comprising a number of dampers 33 is provided. By means of these dampers the volume flow rate of the exhaust gas passing through the intake passageway 29 may be varied as described below.

The secondary air cup 20, the ceramic annular wall 22 and the annular sheet metal walls 23, 26 and 31 are all circular cylindrical and concentric with one another and with the combustion cup 19. Moreover, the two annular walls 23 and 26 are essentially smooth, i.e., they have no blades or vanes or similar elements for imparting a particular flow pattern to the gases flowing in the first mixing chamber 24 and the annular passage 27. Within the second mixing chamber 30 and between the ends thereof, a centrally disposed circular baffle 34 is provided, the area of which is slightly smaller than the cross-sectional area of the first mixing chamber. This baffle 34, which is slightly domed with its convex side facing the burner, serves the purpose of accomplishing an intimate inter¬ mixing of the gases flowing through the second mixing chamber and also provides protection against the radiation from the burner end of the combustion chamber assembly 11. The combustion chamber assembly 11 is dimensioned such that it is capable of receiving, regardless of the load of the diesel engine, substantially all of the exhaust gases discharged from the diesel engine. In an exemplary case, the exhaust gas intake 14 is dimensioned to receive an exhaust gas flow of a maximum volume flow rate of about 3 80000 Nm /h which is the volume flow rate of the exhaust gases discharged at full load of the diesel engine. In operation, the actual volume flow rate may vary, depending on the load, between, for example, 40 and 100 percent of the maximum volume flow rate.

As shown in FIG. 2, the total exhaust gas flow is -^*•^"- distributed among four intake passageways 21, 25, 29 and 32 of the exhaust gas intake 14. Of the total flow, a relatively small portion, e.g. 3 to 6 percent of the total flow, passes through two of the intake passageways, 21 and 25. This portion supplies at least the major portion of the oxygen required, in addition to the oxygen contained in the atomizing air (fresh air) , for the combustion of the fuel oil fed to the burner 15. The portion passing through the intake passageway 21 serves as secondary air and is mixed, in front of the combustion cup 19 where the temperature is kept at about 1500 C, with the combustion gases flowing from the combustion cup. The portion flowing through the intake passageway 25 serves as tertiary air and is mixed in the first mixing chamber 24 with the gases flowing through the opening 20A of the secondary air cup 20, the temperature in the first mixing chamber being thereby lowered to, and maintained at, about 900 C. The two intake passageways 21 and 25 are provided with dampers 35 and 36, respectively, by which the volume flow rate of the exhaust gases flowing through these passage¬ ways may, if required, be controlled to be matched in well-known manner with the volume flow rate of the fuel oil and to keep the temperatures at the burner and in the first mixing chamber at appropriate levels.

In operation, an exhaust gas flow, the volume flow rate of which is independent of the instantaneous total volume flow rate and amounts to 35 to 40 percent of the maximum total volume flow rate, passes through the intake passageway 29. The remaining portion of the instantaneous total exhaust gas flow passes through the intake passage¬ ways 21, 25 and 32. Because only a relatively small amount of exhaust gas passes through the passageways 21 and 25, substantially all of the variation of the total volume flow rate of the exhaust gas flow which is caused by variation of the diesel engine load is accommodated by the intake passageway 32. Accordingly, at low load, almost no exhaust gases at all pass through the intake passageway 32 RE- while at full load, the volume flow rate of the flow in the intake passageway 32 may amount to 55 to 65 percent trf the total volume flow rate.

The volume flow rate of the flow in the intake passage- way 29 and, accordingly, in the annular passage 27, is kept constant by means of the dampers 33 which are control¬ led in a manner not shown in detail by means of a differen¬ tial pressure sensor 37 which senses the pressure differen¬ tial between the exhaust gas intake 14 and the exhaust gas outlet of the combustion chamber assembly and controls a damper actuator 38 connected to the dampers 33.

The portion of the exhaust gas flow passing through the annular passage 27 serves the purpose of effecting, under all load conditions, an efficient cooling of the annular wall 23 which defines the major portion of the first mixing chamber, and an intimate intermixing within the second mixing chamber 30 of the hot combustion gases flowing from the first mixing chamber 24 with the cooler exhaust gases.

Claims

1. Energy-producing installation, comprising a ^'~- combustion engine (12) discharging oxygen-containing ^~ exhaust gases, a steam generator (13) connected to the exhaust gas discharge system of the combustion engine, and a combustion chamber assembly (11) for burning fuel oil by means of the oxygen contained in the exhaust gases, the combustion chamber assembly including an oil burner and forming part of or being disposed in an exhaust gas conduit system which extends between the combustion engine and the steam generator, characterised in that: the combustion chamber assembly (11) is dimensioned to receive substantially the maximum exhaust gas flow from the combustion engine (12) and deliver it to the steam generator (13) ; the combustion chamber assembly (11) has an exhaust gas intake (14) subdivided into a plurality of intake passageways (21,25,29,32) arranged in parallel-flow relation; the combustion chamber assembly (11) comprises a first mixing chamber (24) disposed adjacent the nozzle end of the burner (15) and a second mixing chamber (30) disposed adjacent the first mixing chamber (24) to receive exhaust gases discharged therefrom, the second mixing chamber forming an outlet of the combustion chamber assembly (11) ; a first one of the intake passageways (21) opens into a combustion chamber (19) which is disposed adjacent the nozzle end of the burner (11) and opens towards the first mixing chamber (24) ; a second one (29) of the intake passageways opens into a passage (27) which surrounds, and is arranged in heat- exchange relation to, the wall (23) of the first mixing chamber and which opens into the second mixing chamber (30) ; and control means (33,37,38) are provided which are operative to maintain the volume flow rate of the exhaust gas flow in the second intake passageway (29) and said passage (27) substantially constant, regardless of the total volume flow rate of the exhaust gas flow.

2. Installation according to claim 1, characterised in that the control means (33,37,38) include a damper--^, equipped control device (33) positioned in a third one^"

(32) of the intake passageways and in that said third intake passageway (32) opens substantially directly into the second mixing chamber (30) .

3. Installation according to claim 1 or claim 2, characterised in that a fourth one (25) of the intake passageways opens into a passage which surrounds the combustion chamber (19) and opens into the first mixing chamber (24) .

4. Installation according to any one of claims 1 to 3, characterised in that the first mixing chamber (24) , the passage surrounding the wall (23) of the first mixing chamber, and the second mixing chamber (30) are defined by substantially circular cylindrical, concentric walls (23,26,31).

5υϋB

OMPI