FR2549936A1 - Burner for the gasification of waste materials comprising a regulating device for the supply of fuel. - Google Patents

Abstract

Burner for the continuous gasification of wooden waste materials comprising a combination of: A. A gasification chamber 4; B. A combustion chamber 6 whose inlet is in direct connection with the outlet of the gasification chamber 4; C. A chamber 18 for taking in primary ventilated air; D. A substantially horizontal grate 3 supporting the bed of fuel and forming a separation between the gasification chamber 4 and the chamber 18 for taking in primary ventilated air. E. An injection of secondary ventilated air 5 situated between the outlet of the gasification chamber 4 and the inlet to the combustion chamber 6. F. Means 19 for continuously supplying fuel for distributing the fuel on the grate 3. Furthermore, the burner comprises a system for regulating the fuel supply as a function of the variation of the primary air pressure.

Description

 The present invention relates to a new burner for the gasification of wood waste and other waste.

 We already know different installations for burning wood waste such as that described in patent FB 2,379,766 which has a gasification chamber and a combustion chamber separated by a perforated wall which due to the high temperatures prevailing in the enclosure is frequently blocked. Frequent interventions are therefore necessary.

 The main purposes of the present invention are to provide a resistant installation, easy to maintain, overcoming all the drawbacks of the prior art while allowing the installation of a flexible, reliable regulation, with low response time on the fuel supply.

This goal is achieved by proposing a burner for the gasification of wood waste comprising in combination
A. A gasification chamber.

 B. A combustion chamber, the inlet of which is in direct connection with the outlet of the gasification chamber.

 C. A primary ventilated air inlet chamber.

 D. A substantially horizontal grid supporting the fuel bed and separating the gasification chamber from the primary ventilated air inlet chamber.

 E. A secondary vented air injection located between the outlet of the gasification chamber and the inlet of the combustion chamber.

 F. Continuous fuel supply means for distributing the fuel on the grid.

 This particular combustion makes it possible to regulate the fuel supply and thus to optimize the gasification reaction of the fuel. According to a preferred embodiment of the regulation, the fuel supply is regulated as a function of the variations in pressure of the primary ventilated air, said pressure variations being measured under the grid carrying the incandescent bed, that is to say - say upstream of the gasification chamber.

The invention will be better understood using the description below made with reference to the appended drawings and figures in which
FIG. I is a view in vertical section of a burner according to the present invention,
FIG. 2 is an overall view of the electrical diagram for controlling the regulation of the fuel supply to said burner.

As can be seen in Figure 1, the daughter-in-law includes them
- a gasification chamber (4),
- a combustion chamber (6), the inlet of which is in direct connection with the outlet of the gasification chamber (4),
- a primary ventilated air inlet chamber (18),
- a substantially horizontal grid (3) supporting the fuel bed and making a separation between the gasification chamber (4) and the primary ventilated air inlet chamber (18),
- a secondary ventilated air injection (5) located between the outlet of the gasification chamber (4) and the inlet of the combustion chamber (6),
- continuous fuel supply means (19) for distributing the fuel on the grid (3).

 The fuel supply (19) is carried out in a conventional manner by a submerged Archimedes screw.

 The fuel is for example deposited in the form of an aggregate bed (15) on the cast iron grid (3) (or a sieve).

 The primary air is brought under pressure, and regularly distributed through the holes or slots in the grid and crosses the aggregate, maintaining the incandescence. The gasification of the fuel is carried out in a known manner in the gasification chamber, the volume of which is voluntarily restricted so that, at full power, the total gasification is obtained, without any flame.

 The primary air supply is controlled by a vacuum switch working under pressure, which allows greater flexibility of adjustment.

 This makes it possible to set up a regulation system on the fuel supply: the fuel supply is stopped for a maximum pressure threshold (therefore a predetermined load of the incandescent bed (15) on the grid (3), the fuel supply resumes as soon as the pressure reaches a minimum threshold (therefore if the grid charge is insufficient).

According to the preferred nonlimiting embodiment of the invention, the secondary air enters the combustion chamber after having circulated in the space (9) surrounding the burner, which cools the gasification chamber and heats the secondary air. (up to approximately 50 or 600 in normal operation and approximately 80 to 100 at idle) hence reduction of the LSt
between the gases and the secondary air, which promotes the reaction in the combustion chamber (6) and increases the efficiency.

 For this purpose, the burner has two envelopes, the outer walls (11) of the chambers and an insulating jacket (10) delimiting between them the space (9) for the circulation of secondary air. Preferably, for reasons of construction and ease of installation, the secondary air inlet (II), the primary air inlet (I), the fuel inlet (III) are located on a same face of the burner.

 Furthermore, according to the preferred embodiment of the invention, the secondary air is injected into the gasified fuel, through an orifice (5) at least partially surrounding the outlet of the gasification chamber and located between said outlet of the chamber. gasification (4) and the entrance to the combustion chamber (6).

 Preferably the burner includes a main ashtray (20) for the automatic ash removal of slag and ash, which fall by gravity into the opening of said ashtray (20) located at one end of the grate (3) and under the gasification chamber (4) as shown in FIG. 1. In addition, and without limitation, a stop (14) of suitable length can be provided, having the function of limiting the advance of the glowing bed on the grid (3), this is for avoid the fall of glowing fuel pellets in the main ashtray (20). So the cleaning of said ashtray (20) will be less frequent and the loss of fuel zero.

 In addition an annex ashtray (17) placed under the primary ventilated air inlet chamber (18) itself placed under the grate (3) has the function of recovering the ash and slag which may fall on the bottom (16). of said chamber (18). Said bottom (16) is composed of a plurality of deflectors which direct the ashes towards a central opening.

 All of the outer walls (11) of the different chambers (18) (4) (6) are made of an appropriate refractory material.

 The chambers (4) and (6) can have, without limitation, a variation in height as can be seen in longitudinal section (FIG. 1) to promote the escape of gases and of the flame.

 The burner further comprises a manhole (12) which preferably comprises an appropriate extension (13) visible in FIG. 1. Said extension (13) has a length and a shape suitable for limiting the height of the incandescent bed (15) and across the full width of said bed. This is necessary, as will be explained below, in order to achieve optimal regulation of the supply of fuel as well as optimal gasification.

 The grid is preferably, but not limited to, composed of a plurality of refractory cast iron bars, arranged so as to allow their longitudinal elongation under the effect of temperature variations, so as to avoid the risks of obstruction of the interstices of primary air passage through incandescent aggregates or ashes.

Finally, the insulating jacket (10) performs several functions: reducing the loss of calories to the outside environment, preventing accidental burns by the manipulators,
Said jacket (10) at least partially surrounds the burner and possibly the combustion chamber.

 FIG. 2 represents an exemplary embodiment of the electrical circuit of the continuous fuel supply regulation system. it is understood that the electrical components have been chosen for their robustness, their ease of assembly, their reliability and can be replaced by functionally equivalent components, which can cause modifications in the connection details.

 In addition, according to this non-limiting example of implementation of the invention, the burner according to the invention is combined with a boiler with water circulation and with a chimney with forced ventilation. It is possible, without leaving the invention, to combine the burner with any type of exchanger and with any type of chimney flue.

According to the example of FIG. 1, the electrical circuit of the regulation comprises
- a circuit (C1) for controlling the forced ventilation of the chimney flue
a circuit (C2) for controlling the motor of the secondary air fan, not shown in FIG. 1,
- a circuit (C3) for controlling the motor of the primary air fan, not shown in FIG. 1.

 - a circuit (C4) for controlling the "slowed down" (R) and the "normal running" (N) of the entire installation.

 - a circuit (C5) for controlling the fuel supply.

The components: pyrostat (21), auto-transformers (22) and (24) for controlling the motors (23) (25), aquastat or airstat (26) as well as the vacuum switch (27) for normal operation and the timer (28 ) of slow motion (R), accompanied by their various contacts, are connected in the conventional way for the electrician, in accordance with the electrical diagram of FIG. 2 and in an appropriate manner for
- detect the primary air pressure variations in the primary air inlet chamber (18), therefore upstream of the gasification reaction and preferably at a point located just under the grid (3), then order shutdown or arrival of solid fuel based on the information received. This is achieved by means of the vacuum switch (27).

 - command at least two operating stages called normal operation (N) and slowed operation (R), for at least one of the circuits (C2), (C3), (C4), (C5).

 - allow at least one operating speed in normal operation on the motor (25) of the primary air fan.

This is achieved by means of a plurality of winding positions (that is 4 in FIG. 2) of an auto-transformer (24) additionally comprising a winding position for slow motion (R).

 - allow at least one normal mark operating speed on the motor (23) of the secondary air fan. The auto-transformer (22) is not shown in detail in Figure 2, it can be connected analogously to the auto-transformer (24).

 The component settings are specific to each assembly (burner, exchanger, chimney flue).

 The slowed down setting (R) corresponds to the minimum primary and secondary air flow necessary so that there is no fouling in the exchanger.

For the example chosen the different settings are as follows
- maximum secondary air supply. 280m3 / h
maximum: 280m 1h
idle about 60m3 / h
- supply primary air
maximum 480 m3 / h
idle 96m3 / h.

 In addition, the fuel supply is controlled by default, that is to say each time the pressure switch detects a pressure drop under the grid (3), of approximately 1 to 3 mm of water column. (THIS).

 Indeed, a pressure drop indicates a preferential passage of the primary air through the aggregate bed, therefore a lack of fuel.

 Under optimal operating conditions, the stop (13) and the fuel thrust are such that the bed (15) (or the wafer) has a substantially regular thickness of approximately 5 cm (or even up to 8 cm).

 Under these conditions, the pressure drops through the bed (15) are low, well distributed, resulting in good regulation, short time, better flexibility.

 Finally, this device is suitable for low power burners, up to 500 therms, but it is possible, for example, to adapt 2 or more supply screws for more powerful installations.

Claims (8)

CLAIMS. 1. Burner for the continuous gasification of wood waste comprising in combination  A. A gasification chamber (4).  B. A combustion chamber (6), the inlet of which is in direct connection with the outlet of the gasification chamber (4).  C. A primary ventilated air inlet chamber (18).  D. A substantially horizontal grid (3) supporting the fuel bed and separating between the gasification chamber (4) and the primary ventilated air inlet chamber (18).  E. A secondary ventilated air injection (5) located between the outlet of the gasification chamber (4) and the inlet of the combustion chamber (6).  F. Continuous fuel supply means (19) for distributing the fuel on the grid (3). 2. Burner according to claim 1, characterized in that it further comprises a system for regulating the fuel supply as a function of the pressure variation of the primary air. 3. Burner according to any one of the preceding claims, characterized in that the regulation system comprises means for detecting the variation in pressure of the primary air placed upstream of the gasification chamber (4). 4. Burner according to any one of the preceding claims, characterized in that the detection means (27) is adjusted to detect a pressure drop. 5. Burner according to any one of the preceding claims, characterized in that the detection means (27) is adjusted to detect a pressure drop of 1 to 3 mm approximately. 6. Burner according to any one of the preceding claims, characterized in that the regulation system further comprises means for obtaining at least 2 operating stages, slowed down (R) and normal running (N) on one at minus circuits (C2) (C3) (C4) (C5). 7. Burner according to any one of the preceding claims, characterized in that it comprises a stop (14) for limiting the length of the glowing bed (15). 8. Burner according to any one of the preceding claims, characterized in that it comprises a stop (13) for limiting the thickness of the incandescent bed (15).