IES20070903A2

IES20070903A2 - A boiler

Info

Publication number: IES20070903A2
Application number: IE20070903A
Authority: IE
Inventors: Gerard Kinnane
Original assignee: Cumar Teicneolaiocht Teoranta
Priority date: 2007-12-11
Filing date: 2007-12-11
Publication date: 2008-10-01
Also published as: IE20080901A1; GB0820690D0; GB2455612A; GB2455612B; IE86290B1

Abstract

The present invention provides a boiler comprising a boiler chamber having a base, at least one sidewall and a top to define the boiler chamber. The boiler chamber comprises an inlet for delivering hot combustion gases to the chamber and an outlet for allowing the combustion gases to escape such that the inlet is positioned in close proximity to the top of the boiler chamber for a longer duration of time and spreads the hot gases over a larger surface area. In addition the invention provides a baffle assembly to keep hot gases in the combustion chamber for a longer period of time than is normal for conventional boilers and reduces Nox emissions. <Figure 2>

Description

Field of the Inventio*» The invention relates to an improved boiler heating system and method. In particular the invention provides a new system and method to regulate the flow of hot gases within a heater boiler. io Background to the Invention The traditional method of operation of heating boilers is the generation of hot gases in a combustion chamber that are then used to heat fluid within jacketed walls within the boiler.

Traditionally a boiler system comprises of a boiler chamber, having a pressure jet burner, typically oil powered, fitted thereto. Fuel is combusted within the jet burner, and combustion gases then pass from the burner to the boiler chamber. The combustion gases enter near the bottom of the boiler chamber. As the gases are hot they tend to rise upwardly, and the boiler chamber is provided with at least one exhaust conduit, which directs the gases to a flue from which they escape to the atmosphere. The boiler chamber is provided with waterways adapted to provide a fluid path about the boiler chamber and the exhaust conduit.

In the traditional method of operation, the hot gases generated by the combustion of fuel are used to heat the fluid contained within the waterways. There is a continual need in the boiler industry to improve the efficiency of a boiler due to increased fuel costs and environmental reasons.

The diffusion of heat to the jacketed walls to heat the waterways is dependent on the efficiency of the heat transfer within the boiler itself and is directly proportional to the ability to direct hot gases to the waterways and retain these within the combustion chamber and exhaust chamber for a maximum amount of time without compromising the operation of the burner. Thus the efficiency of the boiler is dependent and is directly ΙΕΟ 7 0 9 03 proportional to the containment duration of the hot gases within the boiler itself, and also the ability to direct gases to the jacketed walls of the boiler waterways. This containment is problematic and can sometimes compromise the efficiency, if the moisture within the exhaust gases condenses. This can affect the combustion of the fuel source, and the burner. Condensed gases also can have a very high acid content and are highly corrosive.

Traditionally the exhaust gases can be kept at a temperature greater than 170 degrees C by using a series of baffles, for example as disclosed by Irish patent Number 82,864, to maintain a steady flow of gases within the combustion cycle and minimise the risk associated with condensate. It will be appreciated that these exhaust gases typically contain Carbon Monoxide, Carbon Dioxide and Nitrogen compounds, and retention of these gases within the combustion chamber could lead to incomplete combustion of the fuel source, and result in efficiencies.

Another problem with boilers are NOx emissions. NOx is an industry abbreviation for the Nitrogen based gaseous compounds that are formed during the combustion of oil, for example NO, NO2, N2O3 etc. These compounds normally would enter the atmosphere and combine with the free moisture in the air to form acidic compounds that lead to acid rain and "smog". In Europe NOx emissions are regulated by European Union Standard EN303-2:1998 and requires that oil fired boilers have to achieve a standard of 250 mg/kWh. There is a definite need to reduce NOx emissions in the boiler industry.

There is therefore a need to provide an improved boiler system to increase efficiency and to maximise the heat transfer from the fuel to the jacketed walls for heating of the waterways, as well as providing reduced NOx emissions.

Summary of the Invention According to the present invention there is provided, as set out in the appended claims, boiler comprising a boiler chamber having a base, at least one sidewall and a top to define the boiler chamber; said boiler chamber comprising an inlet for delivering hot IE 0 7 0 9 Ο 3 combustion gases and an outlet for allowing the combustion gases to escape; wherein the inlet is positioned in close proximity to the top of the boiler chamber.

The boiler of the present invention presents a reversal of a typical boiler design. By having the hot combustion gases enter the combustion chamber near the top of the chamber more efficient results are achieved. The design of the boiler results in the hot gases staying within the combustion chamber for a longer duration of time and spreads the hot gases over a larger surface area, thus heating jacketed waterways that are on communication with the combustion chamber wall to heat water more efficiently.

Suitably, the inlet is positioned in the at least one sidewall and in close proximity to the top of the boiler chamber.

In one embodiment there is provided at least one primary baffle is positioned in the combustion chamber, said primary baffle comprising two inclined portions in communication with a connecting portion to define a single corrugation. A plurality of serrations may be provided on the outer edges of the baffle. Suitably, each serration comprises a substantially semi-circular shape or alternatively can be square, rectangular or triangular shaped.

In another embodiment there is provided a baffle with a plurality of vent apertures located near the outer edges of the two inclined portions.

In a further embodiment there is provided at least one secondary baffle positioned in the combustion chamber comprising a plurality of plates to define a substantially triangular strip baffle. Suitably, each plate is substantially elliptical shaped. Ideally the edge of the plate is serrated. Preferably, each serration comprises a substantially semi-circular shape or alternatively can be square, rectangular or triangular shaped.

In a preferred embodiment at least one primary baffle is placed on top of the at least one secondary baffle.

IE° 70 9 03 Ideally, the secondary baffle creates a back pressure in the boiler chamber and the primary baffle area, allowing the maximum heat transfer, by slowing down the speed of the hot gases passing the at least one primary baffle. Thus the secondary baffle provides a back pressure in the primary heat transfer area.

In a further embodiment the secondary baffle creates a positive pressure at the outlet of the outlet of the secondary heat transfer area, to speed up the gases in the secondary baffle area.

Ideally, the exhaust gases have to travel from the base of the boiler to the top of the boiler in a conduit such that some of the gases condense to liquid and fall back down the conduit by virtue of gravity for subsequent disposal.

Preferably, the liquid condensed comprises water (H2O) and combines with nitrogen gases in the conduit to form acidic compounds and forms acidic liquid, wherein said acidic liquid falls back down the conduit for subsequent disposal.

Brief Description of the Drawings The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:Figure 1 is a perspective view of the boiler according to the present invention; Figure 2 is a cross sectional view of the boiler according to the present invention; Figure 3 illustrates a first baffle arrangement for use in the boiler for primary heat transfer of Figures 1 and 2; Figure 4 illustrates an alternative cross sectional view of the baffle arrangement of Figure 3; Figure 5 illustrates a second baffle arrangement for use in the boiler for secondary heat transfer of Figures 1 and 2; Figure 6 illustrates a perspective view of a conduit for conveying exhaust gases; and KO 70 9 03 Figure 7 illustrates the conduit of Figure 6 attached to the boiler of the present invention.

Detailed Description of the Drawings Referring to Figures 1 and 2, there is illustrated, a perspective and cross sectional view of the boiler according to the present invention, generally indicated by the reference numeral 1. The boiler 1 comprises an inlet 2 for delivering hot combustion gases to the boiler chamber 3. The boiler chamber comprises a base at least one side wall and a top to define a suitable boiler chamber. The inlet 2 for delivering the combustion gases is positioned on the side wall and near the top of the boiler chamber 3. By locating the combustion chamber at the top of the boiler, heat transfer can take place to jacketed walls surrounding the boiler are in contact with the hottest part of the boiler.

The inlet 2 has been located near the top of the boiler and the hot gases generated are forced downwards to the body by the pressure generated by the boiler chamber 3. It will be appreciated this design of having the inlet near the top of the boiler chamber is a complete reversal of a traditional boiler system where the inlet for the combustion gases is positioned near the bottom of the boiler chamber.

The present invention is designed to regulate the flow of the hot gases within the boiler, and also provides a baffle system to direct the hot gases towards waterways surrounding the boiler chamber 3. The waterways are typically jacketed walls known in the art. The inventive boiler design contains the hot gases within the boiler for a longer duration of time and spreads the hot gases over a larger surface area of the waterways.

By locating the inlet 2 at the top of the boiler chamber 3 the heating media, for example water, in the jacketed walls of the boiler are in contact with the hottest part of the boiler, just before they leave the boiler to enter the heating cycle. After a complete heating cycle, this media returns to the coldest part of the boiler the bottom area, therefore heat losses are minimised and efficiencies are increased. This is a reversal of the traditional heating cycle, where the heated media must first pass through the coldest part of the boiler. The outlet for the hot gases is positioned near the base of the boiler and ,εο7θ9θ5 connected to a conduit 7.

The hot gases are contained within the walls of the jacked area for a longer duration of time approx twice as long as conventional boilers known in the art.

As the hot gases are contained within the boiler for a longer duration of time and the surface area, which they come in contact with, has been increased significantly, the heat transfer from the hot gases to the heating media (the liquid in the jacketed walls) is far more efficient.

The present invention provides a primary heat transfer area with at least one primary baffle 4. The primary heat transfer area is where the main heat transfer occurs between the boiler chamber and the jacketed waterways around the boiler. An example of the primary baffle 4 is illustrated in Figure 3. The primary baffle 4 comprises two inclined portions 41 with a connecting portion 42 to define a single corrugation. On the outer edges of the two inclined portions 41, there is provided a serrated edge 43. In a suitable embodiment the serrated edge is in the form of a substantially semi circular shape. The corrugated shape of the baffle 4, having the serrations on the outer edges, slow down the hot combustion gases in the combustion chamber and also serve to direct the hot gases towards the wall of the combustion chamber to increase the efficiency of the heat transfer, as shown in Figure 4.

In another embodiment the serrations are replaced by a plurality of holes or apertures located near the outer edges of the two inclined portions 41. It will be appreciated that the serrations can be of any suitable shape, for example semi-circular, square, rectangular or triangular.

The function of the primary baffles 4 is to slow down the speed of the hot gases passing each primary baffle 4. The heat streams from the hot gases transfer to the outer walls of the boiler chamber in the primary heat transfer area by passing the gases through the series of serrations on the outer edges of the baffles 4. The primary baffles 4 create a streaming effect of the hot gases towards the outer sidewall of the boiler chamber to heat the waterways. As the gases pass through a series of the primary baffles 4 they are •E0 709 03 Ί diverted directly towards the walls of the boiler. It has been found that the heat streams are in constant pressure are each primary baffle to help maximise the heat transfer to the outer wall of the boiler area. The pathway of the hot gases is illustrated in Figure 4 by the small arrows.

The invention further provides a secondary heat transfer area where at least one secondary baffle 5 is positioned in the secondary heat transfer area at the lower portion of the combustion chamber 3. The secondary baffle 5 comprises a plurality of plates to define a substantially triangular shaped strip baffle, as generally indicated by the reference numeral 5. It has been found that a particularly suitable shape for the secondary baffle is to provide each plate comprising a substantially elliptical shape. Furthermore, the edges of each elliptical plate are serrated. Each serration shown in Figure 5 is of a substantially semi circular shape. Alternatively the serrations can be square, rectangular or triangular shaped.

It will be appreciated that the baffle system 4, 5, provides a series of baffles within a boiler, which will contain the hot gases, within the boiler for a longer duration of time. In addition transfer of heat, generated by the combustion chamber, to the jacketed areas of the boiler is transferred more efficiently. The system will also provide a greater ratio of heat transfer to surface area within the same physical boiler itself.

The system also addresses the problem of moisture condensing with the boiler, due to the lower exhaust gas temperature, and without compromising the efficiency of the combustion chamber or the burner. The system will also address the transfer of the condensate from the boiler.

It will be further appreciated that due to the combustion chamber been relocated to the top of the boiler that the hot gases generated are forced downwards, to the body of the jacketed area of the boiler, by the pressure generated by the combustion burner. The exhaust gases are therefore at a much lower temperature than would have been with the exhaust system, for example the exhaust temperature for the boiler design disclosed in Irish patent Number 82,864 is 170 degrees Celsius, while the exhaust temperature for the present invention is approximately 70 degrees Celsius. ΙΕΟ 70 9 The significantly lower temperature causes moisture in the exhaust gases to condense, and the condensate in the flue gas must be removed from the boiler so as not to effect the combustion cycle. The condensate is removed by passing the exhaust gases through a series of small diameter pipes, (Secondary heat transfer area), which have elliptical strip baffle plates as disclosed in Figure 5, which create a back pressure in the combustion chamber and the primary heat transfer area, allowing the maximum heat transfer in the primary heat transfer area, by slowing down the speed of the hot gases passing the primary baffle plates. The elliptical strip baffle plates, also slow the flow of exhaust gases and the design of the elliptical strip baffle plates, and the series of pipes ensures that the gases become in contact with the maximum surface area possible within the available physical space.

The tubes baffles are inserted in a jacketed vessel (Secondary heat transfer area), which in turn is part of the overall heating media, (jacketed waterway of the boiler). The heat transfer at this point is supplementary to the main heat transfer in the combustion chamber and the primary heat transfer area.

In the development of this boiler design, a problem with the exhaust gases is their tendency to become static or "lazy", on cooling, within the internal flue gas passage areas, or flue transfer area. As discussed above the baffle system is primarily to contain the hot gases in the primary heat transfer area for a longer duration of time, maximise the efficiency of the boiler by passing the flue gases through the secondary heat transfer area, and ensuring that the gases are vented effectively from the boiler. The design of the elliptical baffles allows the flue gas transfer from the secondary heat transfer and ensures that the gases don’t become "lazy". The gases are at this point (at the outlet of the secondary heat transfer area) are at approx 70 degrees Celsius and can have a high, and variable, moisture content. The condensing moisture can suppress the flow characteristics of the gases. The secondary heat transfer area creates a backpressure of the hot gases at the entry point and a positive pressure at the outlet, where it meets the flue transfer. The temperature of the gases within the flue transfer is maintained at a consistent not greater than 70 degrees C. ΙΕ0 7q 03 Another important aspect of the present invention is the provision of a conduit, indicated by the reference numeral 7, that provides for very low level of NOx emissions in the exhaust or flue gases. Figure 6 illustrates an example of the conduit, indicated generally by the reference numeral 70. The height H of the conduit is shown along length 71. The gases travel from the bottom to the top along the height H to escape through opening 72. Figure 7 shows the conduit attached to the boiler ready for operation The reason the present invention achieves such a low level of NOx emissions is that, as previously explained, the gases when leaving the secondary heat transfer, are typically at 70 degrees C, and the moisture in the gases starts to condense. This condensate which is laden with water (H2O), will combine relatively easily in the conduit 7 with the nitrogen gases in a chemical reaction to form acidic compounds/liquid. The acidic liquid formed in the conduit 7 can fall back down the conduit 7 and can then be safely disposed of through the waste water system, avoiding harm to the environment. Thus the conduit 7 can be effectively regarded as a condensing tower. Examples of NOx compounds/emissions, but not limited thereto, are Nitric oxide (NO), nitrogen(ll) oxide, Nitrogen dioxide (NO2), nitrogen(IV) oxide, Nitrous oxide (N2O), Dinitrogen trioxide (N2O3), nitrogen(II, IV) oxide, Dinitrogen tetroxide (N2O4), nitrogen(IV) oxide, Dinitrogen pentoxide (N2O5), nitrogen(V) oxide.

It will be appreciated that by passing the gases through the flue transfer at a constant pressure (controlled by the secondary flue transfer), the invention allows the gases the maximum amount of time possible, over the largest area, with the ideal climatic conditions of constant temperature, and linear flow, to combine with the moisture and reduce the emission levels to atmosphere. Essentially due to the fact that the exhaust gases have to travel from the base to the top of the boiler in the conduit 7 provides a natural ‘gravitational well’, shown by the height H, for the gases to condense to liquid and fall back down the conduit 7 by virtue of gravity.

From tests carried out the boiler of the present invention achieves emission levels of less than 48mg/kw/Hr. *0709 02 The result of locating the combustion chamber in the upper area of the boiler, and the exhaust conduit in the lower area, is the hot gases produced in the combustion chamber are not subject to the natural, upward convection flow. These hot gases are forced downwards by the pressure created in the combustion chamber by it’s operation, i.e. air is pumped into this area to assist in the combustion of the fuel, and the pressure generated will pressurise this area and force the gases downwards towards the primary heat transfer area. These gases are held in the primary heat transfer area by a series of baffles as described above. The design, the layout, and the shape of the baffles assist in the generation of heat streams of constant temperature, and direct velocity within the baffles areas. The heat streams transfer to the outer walls of the primary heat transfer area by passing the gasses through a series of vent holes, on the outer edges of the baffles, as shown in Figure 4. The primary baffles create a streaming effect of the hot gases towards the outer jacketed walls. As the gases pass through a series of these baffles they are diverted, directly towards the jacketed walls of the boiler. The heat streams are constant pressure at each inverted baffle, and this helps to maximise the heat transfer to the jacketed area.

Improved Boiler Efficiencies with the present baffle system, for example using a 26 KW Boiler: Existing Boiler New Boiler Full Load 90.4% 98% Part Load 91.5% 103.7% Heat transfer takes place at the following approximate percentages; % in the combustion chamber. 60% in the primary heat transfer area. % in the Secondary heat transfer area.

The 60 % of the heat transfer that takes place in the primary heat transfer area, is directly as a result of the pressure created by the location of the combustion chamber, primary and secondary baffle plates, and the rear flue transfer chamber. The combined location and design of these components ensure that the hot gases are kept within the main body of the boiler for a maximum duration of time and come in contact with the greatest surface area, without compromising the efficiency and operation of the boiler, and its combustion chamber. To maximise the heat recovery in the Secondary Heat transfer area, only materials with high thermal transfer (Conductivity), properties are used in the manufacture of the components, that make up this area, i.e. the secondary housing and the jacketed walls of same, the tubes, the elliptical strip baffles, flue box and rear flue transfer.

The words "comprises/comprising" and the words "having/including" when used herein 10 with reference to the present invention are used to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in 15 the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Claims

1.A boiler comprising: a boiler chamber having a base, at least one sidewall and a top to define the boiler chamber; said boiler chamber comprising an inlet for delivering hot combustion gases to the chamber and an outlet for allowing the combustion gases to escape; and wherein the inlet is positioned in close proximity to the top of the boiler chamber. io

2. The boiler of claim 1 wherein the inlet is positioned in the at least one sidewall and in close proximity to the top of the boiler chamber.

3. The boiler of claims 1 or 2 wherein at least one primary baffle is positioned in the 15 boiler chamber, said primary baffle comprising two inclined portions in communication with a connecting portion to define a single corrugation.

4. The boiler of claim 3 wherein a plurality of serrations are provided on the outer edges of the primary baffle.

5. The boiler of claim 4 wherein each serration comprises a substantially semi-circular shape.

6. The boiler of claim 3 wherein the primary baffle is provided with a plurality of vent 25 apertures located near the outer edges of the two inclined portions.

7. The boiler of any preceding claim wherein at least one secondary baffle is positioned in the boiler chamber comprising a plurality of plates to define a substantially triangular strip baffle.

8. The boiler of claim 7 wherein each plate is substantially elliptical shaped.

9. The boiler as claimed in claims 7 or 8 wherein the edge of the plate is serrated. ΙΕθ7 ο 9θ3

10. The boiler of claim 9 wherein each serration comprises a substantially semi-circular shape. 5

11. The boiler as claimed in any of claims 7 to 10 wherein the at least one primary baffle is placed on top of the at least one secondary baffle.

12. The boiler as claimed in any of claims 7 to 11 wherein the secondary baffle creates a back pressure in the boiler chamber and the primary baffle area by slowing down the 10 speed of the hot gases passing the at least one primary baffle allowing for maximum heat transfer.

13. The boiler as claimed in any of claims 12 wherein the secondary baffle creates a positive pressure at the outlet, to speed up the hot gases in the secondary baffle area.

14. The boiler of any preceding claim wherein the exhaust gases have to travel from the base of the boiler to the top of the boiler in a conduit such that some of the gases condense to liquid and fall back down the conduit by virtue of gravity for subsequent disposal.

15. The boiler of claim 14 wherein the liquid condensed comprises water (H2O) and combines with nitrogen gases in the conduit to form acidic compounds and forms acidic liquid, wherein said acidic liquid falls back down the conduit for subsequent disposal.

16. A boiler as substantially hereinbefore described with reference to the accompanying description and/or drawings.