WO1982002757A1 - Combustion apparatus comprising arrangements in order to ignite the unburnt residues of the primary combustion - Google Patents

Abstract

Combustion apparatus comprising, in addition to a primary combustion chamber (1), expansion chambers (6, 16, 26) for the unburnt residue of the primary combustion. Beyond the first chamber (6), each expansion chamber is directly connected to the primary hearth (1) by a conduit (110) independent of the main conduit (5, 7) coming from the preceding chamber (6, 16) and a primary air inlet conduit (101, 102, 103).

Description

 COMBUSTION APPARATUS COMPRISING ARRANGEMENTS FOR IGNITING IMBULS OF PRIMARY COMBUSTION

The invention relates to a combustion appliance comprising, in addition to a primary combustion chamber, arrangements for igniting the unburned primary combustion.

It applies to appliances, such as stoves, boilers, domestic fireplaces, incinerators, fireplace hearths, burning self-combustible solid bodies, such as coal, wood and at least some household waste.

A simple combustion of these bodies gives off a smoke conventionally composed of water vapor but also of gases and more or less fine particles, and this, although, generally, these gases and / or particles are in themselves combustible.

This smoke is moreover all the more opaque since in general the combustion will have been incomplete.

Indeed, even if the air is introduced in sufficient quantity, it does not always constitute with combustible gases and particles a sufficiently intimate mixture and at suitable temperature to allow the complete combustion of the latter.

However, a larger primary air injection (US patent 3808986) would not solve this problem and above all would cause additional particles in the fumes.

When these unburnt residues are evacuated directly into the atmosphere, in addition to the pollution that may result, it is clear that a significant part of the calorific potential of the fuel is irretrievably lost.

Furthermore, even when the combustion has been complete, the flue gases are generally evacuated at still very high temperatures and, as a result, the heat developed by the combustion is itself even partially lost.

These multiple losses oblige to use self-combustible bodies in quantity and / or with calorific potential much higher than the real needs.

In the field of at least partial recovery of the heat of the fumes, it is known (French patents 1421897, and 1460191 and German patent C-13751C to extend the heat exchange by slowing the flow of these fumes using thermal by slowing the flow of these fumes using baffles and even (US Pat. No. 1,828,644) passing the burnt gases through a succession of chambers which, in addition to the baffling causes a relaxation of the gases which greatly promotes the heat exchange.

If they allow the temperature of the fumes to be lowered before they are discharged into the atmosphere, these devices obviously do not, by themselves, allow complete combustion to be achieved. To complete the combustion, it is already known to use arrangements able to bring the unburnt from the primary combustion to the primary hearth to er ignite.

In a first alternative embodiment (French patent 1224535) a fraction of the unburnt combustible gases is drawn from the smoke duct and then, in combination with air, is reinjected from below through the bed of combustible fuel into the primary combustion chamber. As only an unselected fraction of the fumes is thus recycled, only part of the unburnt from the primary combustion benefits from the post-combustion, the rest continuing its direct evacuation into the atmosphere at still high temperature. In another variant embodiment (French patents 1224838 and American patent 3308986) the device comprises several contiguous combustion zones and at increasing temperature.

Conventionally, primary combustion takes place in a fuel mass arranged on a grate. It is followed by a first post-combustion of the fumes by their second passage above or in the rear fraction of the mass of fuel in ignition or even a second post-combustion of the gasified substances by cracking during the first post-combustion and whose inflammation is linked to the presence of igniting particles in the exhaust gases, which makes it necessary to locate the combustion chambers in the immediate vicinity of the primary hearth and not at a certain distance and for example in the expansion chambers described above (patent GB-1828644).

Therefore, with this device, we deplore the rejection into the atmosphere of perhaps neutral fumes but still having a very high temperature.

A result which the invention aims to obtain is a combustion device of simple design which only releases neutral smoke at low temperature to the atmosphere.

For this purpose, it relates to a device. of the aforementioned type which, on the main conduit for evacuating the products of combustion to the chimney, comprises at least two chambers in order, in addition to the baffling promoting exchange, to cause successive expansion of the burnt gases, this apparatus being in particular characterized in that, beyond the first, each expansion chamber is connected directly to the primary hearth by a pipe independent of the main duct coming from the previous room and the primary air inlet duct.

The invention will be better understood with the aid of the description given below, by way of nonlimiting example, with regard to the appended drawing which schematically represents, such an apparatus seen in perspective and in section through the conduits.

This appliance comprises a closed primary combustion chamber 1 such as that of a stove of a boiler, a domestic hearth or an incinerator or open such as that of a chimney hearth which can obviously also comprise any means for recovering the heat of primary combustion.

This appliance burns self-combustible solid bodies such as coal, wood and certain household waste, for example, which are deposited on a hearth or a grill 2.

Ashes and non-combustible bodies fall into an ashtray 3.

With primary air, the fumes 4 from this primary combustion rise naturally and feel exhausted through at least one main duct 5.

This main duct 5 brings this air and these fumes 4 in an expansion chamber 6 from which these fumes have their outlet braked by a baffling advantageously formed by at least one outlet duct 7 which, on the one hand, passes through the upper wall 8 of the expansion chamber and enters it over about a third of the height of said chamber and, on the other hand, is offset from the inlet duct 5.

This expansion chamber 6 is also connected to a pipe 101 for the entry of primary air, preferably taken from the outside.

Relaxation combined with baffling greatly promotes the mixing, intimate and at a suitable temperature, of this primary air and combustible particles which, on contact with the particles in ignition carried by the fumes, ignite.

The fumes 14 from the second combustion are in turn, via a main duct 7, sent to another expansion chamber 16 from which also they can only exit by a baffling formed from at least one main duct 17 which, on the one hand, passes through the upper wall 18 of the second expansion chamber 16 and penetrates over about a third of the height of this chamber and, on the other hand, is offset with respect to the main inlet duct 7.

To this second expansion chamber 16 is likewise connected a pipe 102 of primary air inlet.

By these baffles and successive detents, the primary air and the fumes 14 combine to produce the same result, namely re-igniting the unburnt substances and thereby improving the combustion. We can thus multiply the expansion chambers and for example provide at least a third 25 receiving primary air through a pipe 103 and the burnt gases 24 from combustion in the second chamber.

If by its direct connection to the primary focus, the first chamber 6 is, via the main conduit 5, ensured to receive particles in ignition, it is not the same for the following 16, 26. According to an essential characteristic of the invention, each of these chambers 16, 26 is connected directly to the primary hearth by a pipe 110 independent of the main duct 7, 17, coming from the previous room and from the primary air inlet duct .

This independent pipe then brings it products 4 of the primary combustion with its particles in ignition.

The upper wall 28 of the last expansion chamber

26 is traversed by the main conduit 27 which, on the one hand, also enters the last chamber 26 over about a third of its height, and, on the other hand, is off-center with respect to the main conduit 17 of entry of this room 26.

Thanks to these successive combustions and to the prolonged heat exchange between the fumes and, on the one hand, the walls of the expansion chambers then, on the other hand, the air surrounding these chambers, the fumes 34 are neutral and moreover are at very low temperatures.

This surrounding air can then obviously be captured by a sheath 35 connected to a hood or a covering 36 at least partially enveloping the device.

To offer larger areas of exchange with the surrounding air, the relaxation rooms can be spaced apart from the other lines and the volumes 9, 19, 29 thus reserved between the rooms can be used as a cooking oven and / or heater - dishes.

Certain rooms 6, 16, 26 and / or certain volumes 9, 19, 29 can also be used to heat water.

Preferably, each room also has a inspection hatch 121, 122, 123 allowing easy cleaning. In each of the pipes 101, 102, 103 of primary air inlet to the expansion chambers is interposed a register 131, 132, 133 for adjusting the primary air flow to a value at most equal to the flow required for combustion unburned which reach it taking into account the decreasing richness of the burnt gases reaching the successive chambers.

As for those in primary household 1, the inputs of iai primary 101, 102 of the different boxes except that 103 of the last, are adjusted so as to provide only insufficient fresh air to be assured that in the subsequent chambers the unburnt will still be rich enough to cause inflammation.

In fact, without this ignition, the expansion chambers would only prolong the exchange between the ambient air and the unburnt from the primary combustion whereas, thanks to the re-ignitions in each expansion chamber, the unburnt is each time even strongly reheated.

In the last chamber 26, the primary air inlet 103 is on the other hand adjusted to, without being excessive, be sufficient for complete combustion so that after its last baffling, the rejection to the conduit to, smoke 34, takes place in the form of a neutral gas and at low temperature.

The base of the outlet ducts 7, 17, 27 of the chambers 6, 16, 26 preferably has serrations favoring the retention of unburnt particles and therefore preventing their evacuation.

Claims

1. Combustion apparatus which, in addition to a primary combustion chamber (1), comprises on the main duct for evacuating the products of combustion to the chimney, at least two chambers (6, 16, 26) so as, in addition to their baffling slowing the flow of burnt gases to promote heat exchange and cause their relaxation this device being CHARACTERIZED in that beyond the first, each expansion chamber is connected directly to the primary hearth by an independent pipe (110) from the main duct coming from the previous chamber (6, 16) and from a primary air inlet pipe (101, 102, 103).

2. Combustion apparatus according to claim 1 in which each expansion chamber (6, 16, 26) has its outlet formed by at least one conduit (7, 17, 27) characterized in that, to cause baffling, this conduit crosses the upper wall (3, 18 28) of this expansion chamber and enters it over about a third of the height of said chamber.

3. Combustion apparatus according to claim 1 or 2 characterized in that each primary air inlet (101, 102, 103) operates by a pipe connected to the outside.

4. Combustion appliance according to any one of claims 1 to 3 characterized in that, on each air inlet pipe (101, 102, 103), an adjustment register is inserted (131, 132, 133 ).

5. Combustion appliance according to any one of claims 1 to 4, characterized in that the air inlet of each of the expansion chambers (101, 102) or the last (103) has a flow rate less than that necessary for total combustion of the unburnt that reaches it.