EP2362894A2

EP2362894A2 - Gasifier and method for ignition of said gasifier

Info

Publication number: EP2362894A2
Application number: EP09810779A
Authority: EP
Inventors: Alessandro Bianchi; Giuseppe Canepa; Vincenzo D'ambrosio; Alice Pesenti
Original assignee: Ansaldo Energia SpA
Current assignee: Ansaldo Energia SpA
Priority date: 2008-10-28
Filing date: 2009-10-27
Publication date: 2011-09-07
Also published as: IT1391443B1; WO2010049786A3; WO2010049786A2; ITMI20081904A1

Abstract

A gasifier is provided with a hollow main body (2) apt to be supplied with the fuel and with at least one infrared- radiation source (20) for ignition of the fuel.

Description

"GASIFIER AND METHOD FOR IGNITION OF SAID GASIFIER"

TECHNICAL FIELD

The present invention relates to a gasifier and to a method for ignition of said gasifier.

Gasifiers are adapted to burn solid fuel to obtain fuel gas, which is generally subjected to a treatment of purification and used, for example, in internal-combustion engines or plants for producing electrical energy.

BACKGROUND ART

Gasifiers of a known type, for example gasifiers of the countercurrent fixed-bed type, comprise a hollow main body, which extends substantially along a vertical axis and within which solid fuel is fed.

In particular, the solid fuel is supplied from above to the main body by means of an appropriate loading system, while a mixture of air and steam is sent into the bottom part of the main body, in countercurrent with respect to the solid fuel. Within the hollow main body there occur different reactions as a function of the temperature reached. In particular, starting from above, processes of heating, drying, pyrolysis, gasification, combustion follow one another.

Combustion of the fuel that occurs in the bottom part of the main body is necessary for sustaining the endothermic processes that occur in the top part of the main body (for example, gasification, pyrolysis, and drying) .

Generally, combustion is started according to a modality that envisages that an operator ignites a liquid- fuel burner, or a sort of torch, on the outside of the gasifier and inserts the ignited portion thereof within the main body through a dedicated opening. Once the fuel is ignited, the burner, or the torch, must be removed from inside the main body. Said modality, in addition to being dangerous for the operator, not always proves effective and at times it is necessary to repeat the ignition operation a number of times. Above all, to make a new attempt at ignition it is necessary to empty the main body of the fuel loaded with an evident expenditure in terms of costs and time.

DISCLOSURE OF INVENTION

An aim of the present invention is to provide a gasifier that is free from the drawbacks of the known art highlighted herein; in particular, an aim of the invention is to provide a gasifier that will enable a simple and safe ignition of the solid fuel loaded therein.

In accordance with said purpose, the present invention regards a gasifier comprising a hollow main body apt to be supplied with the fuel and fuel-ignition means; the gasifier being characterized in that the fuel-ignition means comprise at least one source of infrared radiation.

A further aim of the invention is to provide a method for ignition of a gasifier that will be simple, safe, fast, and effective.

In accordance with said purpose, the present invention regards a method for ignition of a gasifier comprising a hollow main body apt to be supplied with the fuel; the method being characterized in that the fuel of the gasifier is ignited by means of at least one source of infrared radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will emerge clearly from the ensuing description of a non-limiting example of embodiment thereof, with reference to the figures of the annexed drawings, wherein: - Figure 1 is a schematic front view, with parts in cross section and parts removed for reasons of clarity, of a gasifier according to the present invention;

- Figure 2 is a cross-sectional view, with parts removed for reasons of clarity, of a first detail of the gasifier of Figure 1; and

- Figure 3 is a perspective view, with parts removed for reasons of clarity, of a second detail of the gasifier of Figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Designated by the reference number 1 in Figure 1 is a gasifier. In the non-limiting example described and illustrated herein, the gasifier 1 is of the fixed-bed type.

In particular, the gasifier 1 comprises a thermally insulated main body 2, which extends substantially along a vertical axis A, and a bottom container 3 for collection of the ashes.

The main body 2 is defined substantially by a hollow cylindrical element 5 and by a funnel element 6, which connects a bottom open end 7 of the cylindrical element 5 to the container 3 for collection of the ashes and is provided with a main inlet 8 for supply of a mixture of air and steam and with an inlet for supply of nitrogen (not visible in the attached figures) . The main inlet 8 is set along the lateral surface of a portion 9, having the shape of a truncated cone, of the funnel element 6.

Set between the cylindrical element 5 and the funnel element 6 is a mobile grating 10, apt to enable passage of the ashes produced by combustion and to prevent exit of the solid fuel through the funnel element 6. In particular, in the example described and illustrated herein, the mobile grating 10 can be moved manually via a rod 11 that projects on the outside of the funnel element 6. - A -

The cylindrical element 5 is provided, at a top end 12 opposite to the bottom end 7, with a fuel inlet 13 for supply of solid fuel. In particular, the fuel inlet 13 is provided with a device 14 for dispensing the solid fuel, in the case in point a compartmented rotary dispensing device.

The cylindrical element 5 is provided with a gas outlet 16 for exit of the gas produced by gasification of the solid fuel introduced into the cylindrical element 5. In particular, the gas outlet 16 is set on the lateral surface of the cylindrical element 5 in the proximity of the top end 12 and is preferably connected to a device for treating the gas (not illustrated in the attached figures) , which substantially carries out cooling and purification of the gas.

The cylindrical element 5 is provided with an opening 17 for emptying the cylindrical element 5 of the solid fuel, set in the proximity of the bottom end 7 of the cylindrical element 5.

The cylindrical element 5 is moreover provided with at least one secondary inlet 18 in the proximity of the bottom end 7 of the cylindrical element 5. In the non-limiting example described and illustrated herein, the secondary inlets 18 are three and are set in a plane substantially orthogonal to the axis A of the main body 2 at approximately 120° from one another along the lateral surface of the cylindrical element 5 (only two are visible in Figure 1) .

In a position corresponding to each secondary inlet 18, the cylindrical element 5 is provided with a source 20 of infrared radiation or IR lamp (only one is visible in Figure 1) .

By "source 20 of infrared radiation" is meant a source that, when supplied, emits its own energy principally in the IR- wavelength band. In particular, it is to be understood that the area of the spectrum of energy emitted by the source 20 in the IR band is greater than the area of the spectrum of energy emitted by the source 20 outside the IR band. According to a preferred embodiment, the spectrum of energy emitted by the source 20 has a peak in the IR band, preferably in the band comprised between 2 μm and 10 μm, preferably between 3 μm and 6 μm.

Each secondary inlet 18 comprises a duct 21 transverse to the axis A, which gives out into an area internal to the cylindrical element 5 intended for combustion of the solid fuel and is engaged by the source 20.

With reference to Figure 2, each source 20 comprises an irradiating plate 22, a cylindrical body 23, which supports the irradiating plate 22, a cap 24, a flange 26 connected to the cylindrical body 23 and to the cap 24, and a thermocouple 27.

The source 20 is set within the duct 21 so that the irradiating plate 22 is set at a given distance from the area internal to the cylindrical element 5 intended for combustion, in the case in point of the example described and illustrated herein at a distance of approximately 10 cm, so as to determine adequate heating by convection, conduction, and irradiation of the fuel set in the area internal to the cylindrical element 5 intended for combustion.

With reference to Figure 3, the plate 22 has an irradiating face 30 provided with a relief 31 substantially set to form a spiral. Housed inside the relief 31 is a resistor (not visible in the attached figures) supplied by respective supply cables 32 (Figure 2) resistant to high temperatures.

With reference to Figures 2 and 3, the plate 22 is filled with material with high thermal insulation in such a way as to minimize the heat losses on the face 33 opposite to the irradiating face 30 and reduce the temperature in the area close to the electrical connections between the resistor and the supply cables 32. -

The plate 22 is made of ceramic material particularly resistant to high temperatures and to high variations in temperature. Preferably, the plate 22 is subjected to a treatment of surface glazing to improve further the thermal properties of the ceramic material.

The cylindrical body 23 is provided with a hollow internal cylinder 36, which supports the plate 22 and defines a channel 37 for passage of air, and a hollow external cylinder 38, which is set around the internal cylinder 36 so as to define a gap 39. In particular, the internal cylinder 36 exceeds in length the external cylinder 38 and has on the exceeding portion of lateral surface an opening 40 for outlet of the air flowing in the channel 37.

The cylindrical body 23 is moreover provided with a plurality of further channels 41 for passage of air, which are arranged in the gap 39. The gap 39 is preferably filled with the thermally insulating material.

The cap 24 is connected to an air-supply system (not illustrated in the attached figures) , for example, a blower or a compressor, and is fixedly connected to the flange 26.

Basically, the air coming from the air-supply system flows through the cap 24 and subsequently through the channel 37 and the further channels 41. The air that flows through the channel 37 and the further channels 41 carries out principally supply of the area internal to the cylindrical element 5 intended for combustion and also cooling of the source 20. The flange 26 is apt to be connected to a respective flange 43 set around the mouth of the duct 19 of the cylindrical element 5 by fixing means, for example, by means of a plurality of screws 44 coupled at their ends with nuts 45.

Preferably set between the flange 26 and the flange 43 is a sealing gasket 46.

With reference to Figure 1, the cylindrical element 5 is provided with a probe 47 for detection of the internal temperature of the cylindrical element 5, and a detector 48 of the level of solid fuel present in the cylindrical element 5. Preferably, the probe 47 is of the multipoint type; i.e., it is provided with different points for detection of the temperature .

According to the present invention, the method for ignition of the gasifier 1 described above substantially envisages: supplying within the cylindrical element 5 a given amount of solid fuel; rendering the solid fuel supplied inert; activating the source 20; supplying air into the cylindrical element 5 when given conditions of temperature are reached; and finally deactivating the source 20.

In particular, the step of supplying a given amount of solid fuel into the cylindrical element 5 substantially envisages: supplying a given amount of incombustible material; by the term "incombustible" is meant a material that remains inert during combustion of the fuel used in the gasifier; in the case in point of the example described and illustrated herein, the incombustible material is expanded clay in the form of granules; the expanded clay is apt to deposit on the grating 10; since it is inert during combustion, it contributes to sustaining the active fuel allowing the ashes to pass and protecting the grating 10 from high temperatures; preferably, an amount of expanded clay is loaded so as to create a layer of approximately 5 cm or 6 cm above the grating 10; supplying a given amount of high-yield solid fuel, in the case in point wood pellets, mixed with a solid ignition facilitator; the. amount of solid facilitator is preferably equal to 5% of the total volume of high-yield fuel; the high- yield solid fuel is loaded in such a way as to be located within the cylindrical element 5 substantially at the height of the plates 22 of the sources 20, in the internal area of the cylindrical element 5 intended for combustion; preferably, an amount of pellets is supplied so as to create a layer of approximately 10 cm above the clay; and supplying a given amount of solid fuel, in the case in point coke; the amount of coke supplied is preferably equal to the amount of pellets previously supplied.

The method moreover envisages moving the grating 10 via the rod 11 between one step of charging and the next so as to contribute to a uniform arrangement of the layers of clay, pellets, and coke within the cylindrical element 5.

The step of rendering the solid fuel loaded inert substantially envisages supplying within the cylindrical element 5 nitrogen through the inlet for supply of nitrogen (not illustrated in the attached figures) of the funnel element 6. The presence of nitrogen within the cylindrical element 5 blocks any possible undesired ignition until predefined physical conditions are reached. In particular, the nitrogen is supplied for a predefined period of approximately five minutes so as to guarantee an appropriate inertization of the fuel .

The step of supplying air into the cylindrical element 5 until given conditions of temperature are reached substantially envisages supplying a given flow rate of air via the secondary inlets 18, preferably approximately 3 kg/h for each secondary inlet 18, when the plates 22 of the IR lamps 20 have reached a stable temperature of approximately 800⁰C, detected through the thermocouples 27. In particular, it is necessary to wait approximately ten minutes after the plates 22 of the IR sources 20 have reached 800⁰C so as to guarantee a stability of the temperature.

The supply of the air via the secondary inlets 18 determines ignition of the high-yield fuel and, subsequently, ignition of the overlying coke .

When a given internal temperature of the cylindrical element 5 of approximately 100-120⁰C is reached, detected by means of the probe 47, the method envisages supplying a flow rate of a mixture of air and steam via the main inlet 8. Preferably, the flow rate of mixture of air and steam supplied via the main inlet 8 is of approximately 10 kg/h.

Finally, the method envisages deactivating the sources 20 when both the temperature of the sources 20 detected by the thermocouples 27 and the temperature detected by the probe 47, are equal to a threshold, preferably of approximately 800⁰C. Said condition guarantees reaching of a uniformity of temperature within the cylindrical element 5 and authorizes considering that the procedure of ignition has taken place and been completed successfully.

After deactivation of the sources 20, the method envisages reducing the flow rate of air supplied via the secondary inlets 18. In particular, the flow rate is reduced from the initial value of 3 kg/h to a value of 1 kg/h.

Advantageously, the method of ignition according to the present invention does not envisage operations that are dangerous for the operators and is moreover particularly simple and effective. Finally, it is evident that modifications and variations may be made to the gasifier and to the method for ignition of the gasifier described herein, without departing from the scope of the annexed claims .

Claims

1. A gasifier comprising a hollow main body (2), apt to be supplied with fuel, and fuel-ignition means; the gasifier (1) being characterized in that the fuel-ignition means comprise at least one infrared-radiation source (20) .

2. The gasifier according to Claim 1, characterized in that the source (20) is shaped and set in such a way as to heat the fuel up to a pre-set temperature of ignition, at which the fuel, in the presence of air, ignites.

3. The gasifier according to Claim 1 or Claim 2, characterized in that the source (20) is set in the proximity of a bottom end (7) of the main body (2) and faces an internal area of the main body (2) intended for combustion.

4. The gasifier according to Claim 2 or Claim 3, characterized in that the main body (2) comprises at least one duct (21) , which gives out into the internal area of the main body (2) intended for combustion; the source (20) being housed in said duct (21) .

5. The gasifier according to any one of the preceding claims, characterized in that the source (20) comprises an irradiating plate (22), set within which is a resistor.

6. The gasifier according to Claim 5, characterized in that the irradiating plate (22) has an irradiating face (30) provided with a substantially spiral-shaped relief (31); the resistor being housed within the relief (31) .

7. The gasifier according to Claim 5 or Claim 6, characterized in that the irradiating plate (22) is filled with thermally insulating material.

8. The gasifier according to any one of Claims 5 to 7 , characterized in that the irradiating plate (22) is made of ceramic material resistant to high temperatures.

9. The gasifier according to any one of the preceding claims, characterized in that the source (20) is connected to an air-feed system.

10. A method for ignition of a gasifier (1) comprising a hollow main body (2) apt to be supplied with fuel; the method being characterized in that the fuel is ignited by means of at least one infrared-radiation source (20) .

11. The method according to Claim 10, characterized in that the source (20) is shaped and set in such a way as to heat the fuel up to a pre-set temperature, at which the fuel, in the presence of air, ignites.

12. The method according to Claim 10 or Claim 11, characterized in that the source (20) is set in the proximity of a bottom end (7) of the main body (2) and faces an internal area of the main body (2) intended for combustion.

13. The method according to any one of Claims 10 to 12, characterized in that the step of ignition of the fuel of the gasifier (1) comprises the steps of:

- supplying a given amount of fuel in the main body (2) ;

- activating the source (20); and

- supplying air into the main body (2) .

14. The method according to Claim 13, characterized in that the step of supplying a given amount of fuel within the main body (2) comprises the following steps in succession: supplying a first amount of incombustible material; supplying a second amount of high-yield solid fuel; and supplying a third amount of solid fuel.

15. The method according to Claim 14, characterized in that the step of supplying a second amount of high-yield solid fuel comprises the step of supplying a second amount of high- yield solid fuel mixed with a solid ignition facilitator.

16. The method according to any one of Claims 13 to 15, characterized in that it comprises the step of rendering the fuel supplied into the main body (2) inert before activating the source (20) .

17. The method according to Claim 16, characterized in that the step of rendering the fuel inert comprises supplying nitrogen into the main body (2) .

18. The method according to any one of Claims 13 to 17, characterized in that the step of supplying air into the main body (2) comprises:

- supplying a first flow rate of air via at least one secondary inlet (18) when the source (20) reaches a first temperature threshold; and

- supplying a second flow rate of air mixed with steam via a main inlet (8) when the temperature internal to the main body

(2) reaches a second temperature threshold.

19. The method according to any one of Claims 13 to 18, characterized in that it comprises the step of deactivating the source (20) after supplying air into the main body (2) .

20. The method according to Claim 19, characterized in that the source (20) is deactivated when the temperature of the source (20) and the internal temperature of the main body (2) are equal to a third temperature threshold.