EP1170557A2

EP1170557A2 - Heat production arrangement

Info

Publication number: EP1170557A2
Application number: EP01660119A
Authority: EP
Inventors: Lars Ingvar Ollandt
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-07-03
Filing date: 2001-06-21
Publication date: 2002-01-09
Also published as: FI20001588A; EP1170557A3; FI20001588A0; FI109554B

Abstract

The present invention relates to a heat production arrangement for heating service water. Such an arrangement comprises a burner for producing hot gases, a boiler part (1) including a combustion chamber (3) and heat exchange means (5, 5a, 6) for receiving the gases and a condenser (2) fixedly fastened on top of the boiler part for recovering heat energy from the gases. The structure of the boiler part according to the invention is substantially cylindrical so that a main axis (7) in the boiler part is arranged in a substantially vertical direction. The heat exchange means (5, 5a, 6) in the boiler part include radiator vessels (5, 5a) and tap water vessels (6) for receiving and circulating the service water, and the vessels comprise envelope surfaces, which are at least partly in direct contact with the gases. The structure of these vessels substantially comprises cylinders and/or ring-shaped cylinders, and the radiator vessels are thus at least partly connected to one another.

Description

FIELD OF THE INVENTION

The present invention relates to a heat production arrangement according to the preamble of claim 1.

BACKGROUND OF THE INVENTION

It is previously known in the art that the efficiency of heat production arrangements or boiler arrangements can be substantially increased by attaching what are known as condensers as additional equipment. In a conventional condenser, the water vapour that the hot gases in the heat production or boiler arrangements provide, are cooled to a temperature beneath the dew temperature thereof by means of various heat exchange constructions, most frequently various forms of convection surfaces in the condenser. The heat energy bound by the flue gas is emitted during the cooling procedure and also during the transition of water vapour from the gas phase to the liquid phase.
Boilers with a subsequent condenser easily become large and heavy since they require considerable convection surfaces. Consequently the boilers become expensive. The prior art solutions offer an insignificant difference in temperature and low k values on the convection surfaces resulting in a poor heat transfer.
In a particular embodiment of the condenser, in what is known as a spray condenser, the heat bound to the hot gases is in turn transferred directly into liquid droplets produced in a nozzle in the condenser. However, the structure of prior art spray condenser constructions is complicated and frequently require a lot of space. As the prior art constructions are also frequently optimised to wash the hot gases that include above all flue gases, they are also subjected to considerable fouling. The fouling obviously has a negative effect on the efficiency of the condenser, and the reoccurring cleaning of the condenser required to ensure the function thereof is expensive.
Owing to the space requiring constructions the current condensers are commonly also intended to be used above all in an industrial environment, and they can therefore rarely be arranged into small heating-plants or boilers intended to be used in small-scale heat production.

BRIEF DESCRIPTION OF THE INVENTION

The present invention allows to essentially avoid the problems occurring with the previous solutions and at the same time to provide a heat production arrangement with condensers integrated thereto that is easy to use, relatively small and above all light in weight.
This object is achieved with a heat production arrangement characterized by what is disclosed in the claims of the present invention. What is particularly characterizing for the invention is the features referred to in the characterizing part of claim 1.
A substantially novel feature with this invention is that the combination of a boiler part according to the invention and a condenser arranged on top the boiler part require smaller total material heat transfer surfaces and the heat production arrangement thus becomes lighter. This is related to the fact that the heat transfer of a particular heat effect from hot gases to a heat-absorbing medium - often water - circulating in the heat production arrangement occurs very rapidly in an initial part of the heat production arrangement, i.e. in the boiler part. This is naturally caused by the significant differences in temperature that exist at the beginning between the hot gases and the heat-absorbing medium. Here, the heat transfer (generally indicated by Q) depends on the area of the heat transfer surface (indicated by A) multiplied by the heat transfer coefficient (k value) of the arrangement multiplied by the temperature difference (indicated Δt) between the hot gases and the heat-absorbing medium, that is Q = A*k*Δt. When heat transfer is carried out between a gas and a liquid medium the heat transfer coefficient is relatively low compared with a heat transfer between two liquid media, approximately one tenth of this value, but very low, approximately a hundredth according to empirical tests, compared with a heat transfer between a gas and a spray of droplets fed thereto. The heat transfer coefficients for different cases are shown in publications on heating techniques.
In accordance with the tests performed 50% to 90% of the total heat effect of the gases is transferred in a boiler part according to the present invention. This means that the gases are cooled down to a temperature ranging from 200° to 500°. The gases are then conveyed to the condenser arranged on top of the boiler part where heat exchange with a high heat transfer coefficient can be utilized both in the nozzle part of the condenser when heat exchange is carried out between gases and injected liquid drops and in heat exchange between two liquid media in the lower part of the condenser, where a heat exchanger connected to the condenser is utilized to cool the cooling liquid recovered from the spray part, or what is known as the nozzle liquid. Water is frequently used as such a liquid.
This rapid heat exchange consequently results in that a heat production arrangement of the invention requires significantly smaller area of heat transfer surfaces. As such heat transfer surfaces are frequently produced of high-alloy steel, this also signifies that the construction costs can be considerably reduced since less raw material is required and a shorter construction time is needed.
An arrangement of the invention is thus characterized by being able to handle high incoming gas temperatures, which can be conveyed to a boiler part of the invention, in order to rapidly and effectively recover the heat energy extracted from the fuel. After the heat exchange in the service water vessel of the boiler part, the still hot gas is circulated further to the condenser in order to carry out another closed heat recovery.
An arrangement of the present invention also comprises an arrangement for collecting, separating and purifying the cooling liquid utilized in the condenser.
The preferred embodiments of the invention are disclosed in the accompanying dependent claims.
In the description of the present inventions the term 'convection heat system' refers to a system with radiators, which can either be fastened to the wall or built preferably into the floor. The term 'heat exchange means' relates to various types of circulation vessels arranged into the boiler part in which different liquid media are circulated to recover heat energy. Similar liquid media are referred to as 'service water' and may include driving water, radiator water as well as some other liquid medium known per se utilized for heat distribution, such as glycol.
The condenser connected to the boiler comprises an arrangement for cooling a flue gas. The object of the part referred to as the condenser is, however, not necessarily always to convey a gas phase to a liquid phase, instead in some applications a cooling of flue gases is merely to be desired.
In the following description the terms 'up', 'down' 'above' and 'below' etc. refer to directions in relation to the heat production arrangement or the construction details thereof as shown in the attached drawings.
Several significant advantages are achieved with the arrangement described in the present invention over the prior art. The structure of the heat production arrangement therefore allows to achieve a maximum efficiency with a very compact heat production arrangement using minimized heat transfer surfaces, or what are known as convection surfaces. A burner can thus be connected in the new heat production arrangements to the combustion space in the boiler part, which includes on both sides thereof circular convection surfaces that provide good heat exchange properties.
The utilization of an additional condenser preferably provided with two nozzle systems in the heat production arrangement improves the draught both in the boiler part and in the condenser. This means that high chimneys and the sweeping thereof can in much greater extent be avoided. As an inventive use of nozzles or a nozzle system improves the draught, the condenser need not be pressurized either; thus making the structure substantially more advantageous than the competing products. The arrangement with a condenser arranged on top of it results in less heat losses from the top of the boiler part.
Leaching problems that occur for example in conventional tap water coils can be avoided when high-alloy steel is used for constructing the heat exchange means. Consequently the tap water obtained is healthier, and at the same time the reliability of the tap water vessel structure is substantially improved compared with conventional solutions.

BRIEF DESCRIPTION OF DRAWINGS

In the following the invention will be described in greater detail with reference to a preferred embodiment of the accompanying drawing, in which
Figure 1 schematically illustrates a heat production arrangement provided with a condenser of the invention,
Figure 2 shows a preferred embodiment of a boiler part in the heat production arrangement in cross-section,
Figure 3 shows a cross-section of the boiler part in Figure 2 taken along line A-A,
Figure 4 shows a second preferred embodiment of a boiler part in the heat production arrangement in cross-section, and
Figure 5 shows a cross-section of the boiler part in Figure 4 taken along line B-B.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A preferred embodiment of a heat production arrangement for fuel combustion is explained in the following, where the construction parts of the heat production arrangement are indicated with reference numerals that correspond with the reference numerals indicated in the Figures.
A heat production arrangement for fuel combustion comprises a lower so-called boiler part 1 and a condenser 2 preferably connected on top of it. The boiler part includes a burner (not shown), which is in contact with a combustion chamber 3 through a joint duct 4. The combustion chamber comprises heat exchange means 5 and 6, referring to vessels for receiving liquid ― service water ― to be circulated for example in a convection heat system, and vessels for example for heating warm domestic water. These vessels are hereafter referred to as radiator water vessels 5 and tap water vessels 6. The service water comprises preferably standard water but may also be composed of glycol, for example, whereby an effective heat exchange can be obtained in the radiator vessels.
In the preferred embodiment shown in the Figures, the boiler part 1 has a substantially cylindrical structure including a main axis 7 arranged in a substantially vertical direction. At this point the radiator water vessels 5 and tap water vessels 6 are preferably concentrically arranged in the boiler part around the main axis. Thus the tap water vessel preferably represents a core of the boiler part, and the tap water vessel is at least partly arranged to be surrounded by an inner radiator water vessel. According to Figures 1 and 2, the tap water vessel is preferably arranged to come in contact with the hot gases that circulate in the combustion chamber at a bottom 8 thereof. The bottom can also be at lest partly common with the inner radiator water vessel.
The combustion chamber 3 is composed of a substantially cylindrical chamber to which the burner is connected substantially in the tangential direction of the chamber. The combustion chamber is hereby bound by the radiator water vessel 5 arranged on the envelope surfaces of the boiler part, meaning on a sidewall 9, at a bottom 10 and on top 11 of the boiler part according to the Figures. The combustion chamber can also be bound by the tap water vessel described above and the inner radiator water vessel arranged thereto in accordance with the Figures. The combustion chamber can also be arranged to surround several inner radiator water vessels 5a according to Figures 4 and 5. Here the combustion chamber comprises one or more substantially cylindrical ring-shaped radiator vessels arranged outside the inner radiator water vessel. The combustion chamber thus comprises according to the Figures substantially cylindrically ring-shaped slots 12, which extend between the heat exchange means and receives hot gases moving in the tangential direction of the combustion chamber that at least partly include hot flue gases. Such a concentric shaping of the boiler part constructions allow a high efficiency when the gases are combusted and when the gases are heat transferred and the ashes are separated therefrom when conveyed from the burner to the combustion chamber.
The radiator water vessels 5, 5a are preferably connected to one another in order to enable the circulation of the heated liquid and thus to balance the temperature of the liquid. The radiator vessels may be connected to one another through specific pipes 13 arranged thereto in accordance with Figure 1 or through joint upper and/or lower circulation parts 14 and 15 according to Figures 2 and 4. The radiator water vessels and the tap water vessel 6 are further provided with pipes 16, and 17 respectively, to circulate the radiator liquid and the tap water to the respective radiators and taps (not shown). These pipes comprise valves and thermostats 18 and 19 for regulating the liquid flow.
The thermostats 18 and 19 are arranged so as to come in contact with the burner connected to the heat production arrangement and thus to regulate the operation of the burner in order to avoid overheating the service water in the heat exchange vessels 5 and 6.
The hot gases produced during the combustion are arranged to be conveyed from the combustion chamber 3 through at least one flue 20 to a condenser 2 preferably arranged on top 11 of the boiler part 1. Hence, the top of the boiler part represents at the same time the bottom of the condenser which further improves the heat exchange in the arrangement. The flue extends to the upper part 21 of the condenser in accordance with Figure 1. The structure of the condenser is substantially U-shaped, and includes in addition to the upper part also a nozzle part 22, to which the hot gases taken in through the flue are directed. A bottom part 23 included in the condenser lies below the nozzle part. The bottom part is connected to both the nozzle part and a discharge part 24 included in the condenser. The condenser may also comprise a construction according to Figure 1 with two substantially parallel cylindrical parts connected to one another at the end orientating towards the bottom part of the condenser. The structure of the condenser may also be cylindrical or geometrically differently formed and divided by means of a partition wall into two substantially vertical parts connected at the end orientating towards the bottom part of the condenser.
The gases flowing to the nozzle part 22 are arranged to pass a means included in the nozzle part, a primary nozzle or a nozzle system 25, whereby the nozzle part is provided with atomized cooling liquid 26, or what is known as nozzle liquid. At this stage the gases flowing downwards towards the bottom part 23 of the condenser come in contact with the cooling liquid droplets secreted downstream by the nozzle. An adequate atomization of the cooling liquid is accomplished using a circulation pump 27 connected to the nozzle. The circulation pump is arranged to regulate the pressure of the cooling liquid that flows through the nozzle and further to the nozzle part and to the gases flowing therein. The pressure in the pump should be as high as possible in order to provide as small droplets as possible. The smaller the droplets in the cooling liquid secreted in the gases are the more efficient the heat exchange between the gases and the cooling liquid becomes. The volume of the liquid flow through the nozzle is preferably regulated so as to take in a required amount of heat without causing the cooling liquid to vaporize.
In the nozzle part 22 some flue gas components including fixed particles such as soot particles are also converted into secreted cooling water droplets, whereafter the droplets can be recovered in one of the collecting vessels, or what is known as an insert 28, at the bottom end of the nozzle part. The collecting vessel is preferably arranged to be removed from the condenser 2 using a hatch included therein for cleaning.
The gases washed in the nozzle part are hereafter arranged to flow onwards from the nozzle part to a construction part substantially parallel with the nozzle part, the discharge part 24. Hence, the discharge part is in contact with the nozzle part through openings in the insert 28. The discharge part is preferably provided with a draught valve 29 for retarding or limiting the flow rate of the gases in the nozzle part, which affects the heat transfer from the gases to the cooling liquid droplets in a very positive way.
The heat recovery made more effective in this way signifies that the volume of the condenser (2) can be reduced in comparison with the conventional one. This, in turn, naturally means that considerable savings can be made in the construction costs.
When the temperature of the liquid collected in the bottom part 23 of the condenser exceeds the dew temperature of the water vapour in the gases then another means arranged on top of the draught valve 29 is used to bring the gases in direct contact with a cooling liquid 30, in other words a secondary nozzle or nozzle system 31. This nozzle is also preferably directed in the flowing direction of the gases. The cooling liquid flowing through the secondary nozzle brings the water vapour in the gases to partly condensate in the discharge part 24. Consequently no new cooling liquid needs to be supplied to the arrangement. The cooling liquid that flows through the nozzle, which substantially points upwards, can advantageously circulate through the insert in order to set fixed particles free from the nozzle liquid.
The cooling liquid 26 and 30 that flows into the nozzle systems 25 and 31 is advantageously arranged to be cooled using at least one heat exchanger 32 and/or 33. It is of particular importance that the cooling liquid in the secondary nozzle system 31 arranged to the discharge part is adequately cooled in order to obtain a condensation that is as effective as possible. Such a heat exchanger 32 can be arranged to be immersed in the liquid collected in the bottom part of the condenser, but the heat exchanger 33 may also be arranged outside an outer envelope 34 in the condenser. The heat exchanger comprises an air or liquid-based heat exchanger known as such.
As the fixed heat transfer surfaces in a heat production arrangement of the present invention form the sum of the heat transfer surfaces in the boiler part (1) ― indicated A_B ― and the heat transfer surfaces in the condenser (2) ― indicated A_C ― the need for the total amount of heat transfer surfaces A = A_B + A_C can therefore be illustrated by means of a calculation example as follows.
The following calculations are obtained for different heat powers (0 to 100 kW) using a heat power Q = 100 kW, an incoming (flue)gas temperature t₁ = 1000 °C, an outgoing (flue)gas temperature t_ut = 45 °C, a radiator water temperature t_Cln = 35 °C and a condenser temperature if t_C = 50 °C
the amount of absolutely dry (flue)gas m_trg = Q/i₁ - i_ut
(flue)gas enthalpy out I₂ = ((m_trg * i₁) - Q_B/m_trg
the temperature after the boiler part t₂ = f(1₂; λ = 1,5)
mean temperature diff. Δtm = ((t₁ - t_c) - (t₂ - t_C))/ln((t₁ - t_C) - (t₂ - t_C))
the heat transfer surface in the boiler part A_B = Q_B/k_s*Δtm;
when k_s = 0,05-0,08 kW/m²°C
the heat transfer surface in the bottom part of the condenser
A_C = (Q - Q_B)/k_C* Δtm_C; when k_C = 0,6 kW/m°C och Δtm_C = 10 °C
the total surface A = A_B + A_C
where i₁, i₂, λ, k_s are table values known as such.
The results of the calculations may be summarized in the following table:

Q_B [kW] A_B [m²] A_C [m²] A[m²]

40 0,7 10,0 10,7

60 1,4 6,7 8,1

70 2,2 5,0 7,2

80 3,4 3,3 6,7

95 6,7 0,9 7,6

100 11,0 - 11,0
This may in turn be summarized in a graphic presentation where the ordinate is composed of the total heat transfer surface A in relation to the desired heat power in the boiler part Q_B indicated in the abscissa. The abscissa can also be composed of the (flue)gas temperature after the boiler part, i.e. t₂.
In the above-described embodiment the discharge part 24 comprises at least a semicircle-shaped lip 35 pointing upwards with an opening at the bottom for catching and separating liquid droplets from the gases flowing by. A tight net 36 is preferably placed on top of such lips for separating the smaller droplets still found in the gases. The separated droplets are arranged to run along the walls of the discharge part, back to the bottom part 23 of the condenser 2, from where the liquid is once again circulated through the circulation pump 27 to one of the nozzle systems. In order to perform an additional purification of the gases a cyclone 37 may be connected to the discharge part that allows to recover the liquid droplets from the passing gas.
After the cooling liquid 26 and 30 have come in contact with the gases and been heated in this way, the cooling liquid runs down to the bottom part 23 of the condenser. According to the above, at least one heat exchanger 32 is arranged in this amount of collected heated liquid to cool the cooling water. Such a heat exchanger can preferably be arranged to heat the circulation water for a convection heat arrangement but also to pre-heat the service water, which is thereafter circulated to the heat exchange means 5 and 5a in the boiler part 1. The heat exchanger may naturally also be intended to only cool the nozzle or cooling liquid.
The cooling liquid 26 and 30 collected in the bottom part 23 of the condenser can also be circulated directly in a convection heat arrangement without utilizing a particular heat exchanger 32. In such a case, it is assumed that the convection heat arrangement is made of a corrosion-resistant material.
The above specification and the figures therein are merely intended to illustrate the present invention. The invention is therefore not restricted to the embodiment described above or in the attached claims but a number of variations or alternative embodiments can be carried out within the scope of the inventive idea described in the attached claims.

Claims

A heat production arrangement for heating service water by combusting fuel, the heat production arrangement comprising a burner for producing hot gases, such as combustion gases and flue gases, a boiler part (1) including a combustion chamber (3) and heat exchange means (5, 5a, 6) for receiving the gases and a condenser (2) connected to the boiler part for recovering heat energy from the gases and purifying said gases, the gases being arranged to be conveyed from the boiler part to the condenser, the structure of which is substantially U-shaped and includes an upper part (21), a bottom part (23) and a discharge part (24), the upper part being arranged to receive the gases and includes means (25) for bringing the gases in direct contact with a cooling liquid (26), and the bottom part being arranged to collect the cooling liquid, characterized in that

the structure of the boiler part (1) is substantially cylindrical so that a main axis (7) in the boiler part is arranged in a substantially vertical direction,

the heat exchange means (5, 5a, 6) in the boiler part include vessels arranged in the combustion chamber (3) for receiving and circulating the service water, and the vessels comprise envelope surfaces, which are at least partly in direct contact with the gases.
A heat production arrangement as claimed in claim 1, characterized in that the heat exchange means comprise one or more radiator water vessels (5, 5a) and a tap water vessel (6).
A heat production arrangement as claimed in claim 2, charactecized in that the radiator water vessel (5) is arranged to substantially surround the tap water vessel (6).
A heat production arrangement as claimed in claim 3, characterized in that the combustion chamber (3) is arranged to substantially surround the radiator water vessel (5) arranged to surround the tap water vessel (6).
A heat production arrangement as claimed in any one of the preceding claims, characterized in that the structure of the radiator water vessel (5, 5a) substantially comprises cylinders and/or ring-shaped cylinders at least partly connected to one another whereas the tap water vessel (6) comprises a single cylinder.
A heat production arrangement as claimed in claim 5, characterized in that the combustion chamber (3), the radiator water vessel (5, 5a) and the tap water vessel (6) are concentrically arranged.
A heat production arrangement as claimed in any one of the preceding claims, characterized in that the burner includes a joint duct (4), which is connected to the combustion chamber (3) in the tangential direction thereof.
A heat production arrangement as claimed in any one of the preceding claims, characterized in that the combustion chamber (3) is connected to the condenser (2) by means of one or more flues (20) arranged to convey the hot gases to the upper part (21) of the condenser.
A heat production arrangement as claimed in claim 8, characterized in that the condenser (2) comprises means (25, 31) for bringing the gases in direct contact with the cooling liquid (26, 30) in the upper part (21) and in the discharge part (24) thereof, both means being directed substantially in the flowing direction of the gases.
A heat production arrangement as claimed in claim 9, characterized in that the discharge part (24) comprises a draught valve (29) below the means (31) for injecting cooling liquid, retarding or limiting the flowing rate of the flue gases in the condenser (2).
A heat production arrangement as claimed in claim 9 or 10, characterized in that the condenser (2) comprises a collecting vessel (28) for collecting and purifying the cooling liquid (26, 30) fed to the upper part of the condenser, the collecting vessel being arranged to be removed from the condenser through a hatch included therein.
A heat production arrangement as claimed in any one of the preceding claims, characterized in that the bottom part (23) of the condenser (2) comprises a heat exchanger (32) arranged thereto.
A heat production arrangement as claimed in any one of the preceding claims, characterized in that the discharge part (24) of the condenser (2) comprises a cyclone (37) arranged thereto for separating liquid drops from the gases.
A heat production arrangement as claimed in any one of the preceding claims, characterized in that the boiler part (1) and the condenser (2) are connected in such a manner that the top (11) of the boiler part forms the bottom of the condenser.