EP0184119A2 - Process for firing a steam or hot water boiler - Google Patents

Abstract

The steam or hot water boiler has at least two part combustion chambers (1, 2) which are separated from one another by means of a partition (5). Each of these part combustion chambers has a mechanical grate firing (3, 4) which are designed according to the different fuels which are fed by feed devices (14, 15) which are separated from one another. In the individual part combustion chambers, the operating conditions with regard to the supply of the forced draught and the secondary or tertiary air supplies are matched to the respective characteristic properties of the fuel used. By virtue of the partition (5), the operation is thus possible in one boiler of different grate firings for different solid fuels. <IMAGE>

Description

The invention relates to a method for firing a steam or hot water boiler using different fuels.

With the simultaneous combustion of garbage and coal, it is known to give up prepared garbage on a ground fire consisting of classified coal by comminution and partial sorting, either with a correspondingly small proportion of an injection into the combustion chamber and with larger proportions a direct task on the grate is possible. However, to the extent that this additional fuel for the base fuel exceeds a certain quantitative proportion, difficulties arise which are based on the different properties of the fuels used. These different properties consist in different calorific values, in the very different burning behavior over time, in the different ash formers and therefore also different ash melting points, and also in the fact that these fuels produce very different flame and gas temperatures. These fuels should only be burned together if one of the fuels represents the larger proportion.

The object of the invention is to provide a method for which it is possible to fire a steam or hot water boiler with various solid fuels in any proportions.

This object is achieved according to the invention in a method of the type specified above in that for each fuel an independently operable, specially designed for the fuel in question partial firing is provided, which is operated independently of the firing provided for the other fuel.

A steam or hot water boiler is already known (GB-PS 2 077 892), in which the firing is divided into individual partial firings, the individual firing grates being able to be operated separately from one another. However, the individual combustion chambers are fed with the same fuel, namely waste. The subdivision into grate furnaces that are independent of one another takes place for the purpose of regulating the steam generation. The refuse incineration can not be set in terms of performance, which is primarily due to the low calorific value. The grate firing must therefore be operated with a certain minimum output. This has sometimes led to over-production of steam, which then has to be condensed again in an uneconomical manner. For this reason, partial combustion systems have been set up so that it is possible, depending on the power requirement, to operate one or more of these partial combustion systems.

Since it is in the known steam boiler according to GB-PS 2 077 892 to fire the same fuel, in which a subdivision into individual firings was only made to better regulate the heating output to achieve, the solution according to the invention cannot be derived from this.

The solution according to the invention makes it possible to design and operate each partial combustion chamber in the manner required by the fuel used therein. Compromise solutions that take the different combustion behavior into account need not be taken into account, which improves the efficiency. A mutual influence in the burning behavior of the individual fuels is excluded by their independent combustion.

The independent firing of the respective fuels leads not only to an optimal grate design for the respective fuel, but also to a good controllability of the steam output, since it is easier to adjust several partial firings to a certain overall result, for example by switching off a partial firing, than with a large firing designed for several fuels the same overall performance is the case. Independent firing of the respective fuel and the control measures based on this fuel also make it possible to achieve low pollutant gas values.

The flue gases from the individual partial firing systems can be conducted in separate gas and boiler trains of a boiler divided into individual partial boilers. However, it is also possible for the flue gases from the individual part-firing systems to be routed in a common gas train and a common boiler train.

In the case of a subordinate arrangement of a common gas train and a common boiler train, it is possible to use baffles and baffles made up of boiler pipes in the common gas train provide for the exhaust gases in order to mix the gas streams, which differ in their composition, temperature and quantity, as intensely as possible when they meet, so that the common boiler trains are acted upon by a largely homogeneous gas flow. This mixing and homogenization of the gas streams can also be brought about by boiler tube or superheater bundles which are provided in the gas flues.

Further measures that can be taken according to the invention in order to take into account the particular characteristics of the fuel used are that the underwind supply is regulated separately in the individual partial firing systems.

In addition, it can be advantageous if, in a further embodiment of the invention, both the secondary air supply and any tertiary air supply are regulated separately in the individual partial firings.

• Fig. 1 einen Schnitt durch eine erste Ausführungsform, bei der die Teilfeuerräume hintereinander angeordnet sind;
• Fig. 2 eine der Fig. 1 entsprechende Darstellung einer abgeänderten Kesselbauart;
• Fig. 3 eine schaubildliche Darstellung einer ersten Ausführungsform mit parallel angeordneten Teilfeuerräumen mit nachgeschaltetem gemeinsamen Kessel für beide Feuerungen;
• Fig. 4 eine schaubildliche Darstellung einer gegenüber Fig. 3 abgeänderten Ausführungsform mit parallel angeordneten Teilfeuerungsräumen und Trennung des Kessels in Teilkessel bis zum Kesselende;
• Fig. 5 einen Querschnitt durch mehrere nebeneinander angeordnete Teilfeuerungsräume mit einer ersten Ausführungsform der Trennwände;
• Fig. 6 einen Querschnitt durch parallel nebeneinander liegende Teilfeuerungsräume mit einer zweiten Ausfuhrungsform der Trennwand; und
• Fig. 7 einen Querschnitt durch nebeneinander liegende Teilfeuerräume mit gegenüber Fig. 6 abgeänderter Ausgestaltung der Trennwand.

The accompanying drawing shows schematic embodiments of steam and hot water boilers with which the method according to the invention can be carried out.

• 1 shows a section through a first embodiment in which the partial combustion chambers are arranged one behind the other;
• Fig. 2 is a representation corresponding to Figure 1 of a modified type of boiler.
• Fig. 3 is a diagrammatic representation of a first embodiment with partial combustion chambers arranged in parallel with downstream common boiler for both furnaces;
• FIG. 4 shows a diagrammatic representation of an embodiment modified compared to FIG. 3 with partial combustion chambers arranged in parallel and separation of the boiler into partial boilers up to the boiler end;
• 5 shows a cross section through a plurality of partial combustion chambers arranged next to one another with a first embodiment of the partition walls;
• 6 shows a cross section through partial combustion chambers lying next to one another in parallel with a second embodiment of the partition wall; and
• FIG. 7 shows a cross section through partial combustion chambers lying next to one another with a design of the partition wall that is modified compared to FIG.

1 and 2, a superheated steam or hot water or saturated steam boiler is shown, which comprises two partial combustion chambers 1 and 2 arranged against each other, in each of which mechanical grate furnaces 3 and 4 are provided. The two partial combustion chambers 1 and 2 are separated from one another by a partition 5, which is constructed from two boiler tube walls 6 and 7, which are independent of one another and each have their own collectors 8, 8a and 9, 9a. A funnel 12 is arranged between the collectors 8 and 9, in which dust from the exhaust gases can be partially absorbed. With 13 a discharge line for the collected dust is designated.

Since the partial firing chambers 1 and 2 are arranged opposite one another, they have feed devices 14 and 15 for the firing units 3 and 4 on opposite sides. With 16 a common slag discharge device is designated. The two grate furnaces 3 and 4 are provided with independently controllable underwind feeds 10 and 11.

The boiler shown is designed as an integrated boiler, i.e. the side walls of the boiler consist of boiler tube walls 17, which are located above the grate furnace. In the throttle cable 18, for example, a superheater 24 can be arranged, and a boiler tube bundle 19 with a lower boiler drum 20 and an upper boiler drum 21 is provided. After the boiler tube bundle 19, economizers 22 in FIG. 1 and air preheaters 23 in FIG. 2 are arranged in the descending exhaust gas duct; i.e. Instead of economizers, air preheaters can also be provided in whole or in part.

For the swirling and thus homogenization of the gas flows, an overheater 24 is provided in FIG. 1 in front of the boiler tube bundle 19 and a baffle plate 25 constructed from boiler tubes in FIG. 2. The same reference numerals have been used for the same parts in FIGS. 1 and 2.

3 and 4 again show very similar embodiments, which differ only in the degree of subdivision of the boiler, which is why the same reference numerals are used for the same parts in these two embodiments.

The embodiments shown in FIGS. 3 and 4 are also integrated boilers, in which not only the lateral boundary walls 26, 27, but also a partition wall 28 in the embodiment according to FIG. 3 and a partition wall 29 in the embodiment according to FIG. 4 are constructed from boiler tubes.

The partition wall 28 divides the combustion chamber into two partial combustion chambers 30 and 31 with two grate furnaces 32 and 33, which are parallel to one another and have a common slag discharge 34. For the feed of the fuels, a feed hopper, generally designated 35, is divided into two feed devices 37 and 38 by a partition 36. The exhaust gases rising from the partial combustion chambers 30 and 31 are combined in the common gas train 39, in which an overheater 40 is provided. A boiler tube bundle 41 with a lower drum 42 and an upper drum 43 is provided after the superheater. For example, economizers 44 are provided in the downward exhaust gas flue, which adjoins the boiler bundle 41.

Each grate burner 32, 33 is assigned independent underwind supply devices, of which only the underwind supply device for the grate combustion 32 can be seen in the drawing, which in turn is subdivided into independent underwind supply devices 32a and 32b.

In the embodiment according to FIG. 4, the entire boiler is divided by the partition 29, ie not only are two partial combustion chambers 30 and 31 located next to one another in parallel, but the entire boiler is divided into two partial boilers 45 and 46. This subdivision also affects the superheater, the boiler bundle and the downstream and air preheater economizers. The each partial boiler 45 and 46 assigned superheaters are designated by 47 and 48 and the two boiler tube bundles by 49 and 50. Economizers 51, 51a and air preheaters 52, 52a are arranged in the exhaust gas flue. It is also possible, for example, to provide an economizer in one exhaust duct and an air preheater in the other exhaust duct.

In the embodiment shown in Fig. 5, the first train of the boiler is divided into three partial firing chambers 53, 54 and 55, which are parallel next to each other, the two partitions 56 and 57 as well as the outer walls 58 and 59 being constructed as simple boiler tube walls. A combustion grate 60, 61 or 62 is assigned to each partial combustion chamber, which, depending on the fuels used, can be designed as moving grate, feed grate, roller grate or return grate. The grids can be identical or different to one another. Underneath the respective grates there are independent underwind feed devices 63, 64 and 65, each of which has a discharge line 66 for grate diarrhea at its lower end.

In this embodiment, the exhaust gas flows from the individual partial combustion chambers are combined in a common exhaust gas duct 89.

In the embodiment according to FIG. 6, two partial combustion chambers 67 and 68, which are arranged parallel to one another, are shown, which have grate combustion systems 69 and 70 with corresponding underwind feed devices 71 and 72. The essential difference compared to the embodiment according to FIG. 5 is that the partition wall, designated overall by 73, is constructed from refractory material, ie masonry. The outside walls are formed as boiler tube walls and provided with the reference numerals 74 and 75. As in the embodiment according to FIG. 5, the underwind feed devices are provided with a discharge line 76 in order to be able to discharge the grate diarrhea. The partition 73 is formed at its upper end in the manner of a gable, so that the dust which has settled can slide downward. The common exhaust duct is designated 89. In the embodiment according to FIG. 7, two partial combustion chambers 77 and 78 with mechanical grate furnaces 79 and 80 are also provided, which are separated from one another by a partition wall, designated overall by 81. This partition is made up of two independent boiler tube walls 83 and 84. Separate collectors 85 and 86 are provided on the upper part for each partition, which are connected by a funnel 87, which has a discharge opening 88 for the accumulated dust. A gas discharge common to both partial combustion chambers is designated with 89. The individual grate furnaces 79 and 80 are assigned independent underwind feed devices 90 and 91, which are funnel-shaped and have lines 92 provided at their lower ends for the discharge of the grate diarrhea. With 82 a retaining wall for the partition 81 is designated. The outer walls of the integrated boiler, which are designated 93 and 94, have the same structure as the boiler tube walls 83 and 84 of the partition 81.

Secondary air supply devices 95 and tertiary air supply devices 96 serve to influence the flame formation and the flame temperature.

Claims (5)

1. A method for firing a steam or hot water boiler using different solid fuels, characterized in that for each fuel an independently operable, specially designed for the fuel part grate combustion is provided, which is operated independently of the partial grate combustion provided for the other fuel. 2. The method according to claim 1, characterized in that the flue gases of the individual partial grate furnaces are conducted in separate gas and boiler trains of a boiler divided into individual partial boilers. 3. The method according to claim 1, characterized in that the flue gases of the individual grate furnaces are performed in a common gas train and a common boiler train. 4. The method according to any one of claims 1 to 3, characterized in that the underwind feed is controlled separately in the individual partial grate furnaces. 5. The method according to any one of claims 1 to 4, characterized in that both the secondary air supply and the tertiary air supply are controlled separately in the individual partial grate furnaces.

Images