FR2464433A1 - AIR GAS BURNER WITH VERY HIGH FLOW VARIATION - Google Patents

Abstract

THE INVENTION CONCERNS A BLOW-AIR GAS BURNER WHOSE CALORIFIC FLOW MAY VARY OVER A VERY WIDE SETTING RANGE AND IN PARTICULAR LIKELY TO OPERATE FOR VERY LOW FLOWS, GAS BURNER INCLUDING A GAS DELIVERY DEVICE AND A DEVICE AIR INLET, AS WELL AS A DIVERGENT DUCT IN WHICH THE AIR-GAS MIXTURE TAKES PLACE. THIS BURNER IS CHARACTERIZED IN THAT THE DIVERGENT TERMINAL SECTION HAS AT LEAST TWO STAGES OF INTRODUCTION OF AIR OR COMBUSTIBLE GAS. APPLICATION TO ALL COMBUSTION PROCEDURES IN WHICH THE FLOW OF COMBUSTIBLE GASES IS LIKELY TO VARY IN GREAT PROPORTIONS AND, IN PARTICULAR, TO THE CLAUS PROCESS.

Description

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  The present invention relates to a gas blast furnace burner whose heat flow can vary over a very wide adjustment range and which is particularly likely to function

for very low flow rates.

  The development of air-blast burners is of considerable importance in many industries, especially in the heavy chemical industry, where they are indispensable in the processes of obtaining many large-scale products.

  and used as raw material in processing industries.

tion.

  However, most blast-gas burners have fixed sections of gas and air injection; as a result, the injection speeds in these fixed sections decrease when the required heat flow decreases. However, these speeds reach, at low speed, insufficient values to ensure a satisfactory mixture of air and gas and, consequently, a combustion

complete, fast, stable.

  This characteristic of conventional burners is not without disadvantage: in fact, many operations thus require the use of multi-burner fireplaces that can be

  switched on according to the heat flow rate requested.

  Consequently, in these installations, it is necessary to change the burner frequently during operation, which makes it necessary to carry out successive and relatively long shutdown and reignition operations of the burners and is not without increasing

  considerably the cost price of the finished product.

  Moreover, in this type of installation, the heat of the hearth causes an accelerated deterioration of the burners at rest,

  particularly in the case of briquettes maintained at high temperatures

  erosion, or foci operating in pressure.

  In some installations, to avoid inconveniences

  above mentioned, it is necessary to blow air, smoke, or steam on the burners at a standstill in order to cool them during the process, which leads to waste

important thermal energy.

  It has already been proposed devices for varying the injection section of the air and that of the gas of a

  burner to maintain fluid velocities

  despite variations in flow rates.

  But, such devices are defeated for

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  very low flow rates because the end section of the burner does not change and the mixing speed of gas and air remains

very weak.

  The object of the present invention is to remedy the inconveniences

  the above-mentioned advantages, by proposing a gas burner that can function properly at very low flow rates and therefore can be installed as a single burner on fireplaces.

  which previously required the use of several burners.

  To this end, the present invention relates to a gas blast furnace burner whose heat flow can vary over a very wide range of adjustment and in particular capable of operating at very low flow rates, gas burner comprising a gas inlet device and an air inlet device, as well as a divergent duct in which the air-gas mixture is carried out, characterized in that the diverging terminal section presents

  minus two stages of introduction of combustion air.

  The advantage of having a single burner with a very large variation in flow rate concerns all fireplaces and particularly sulfur-producing furnaces by combustion of hydrogen

sulphide (Claus process).

  On the latter type of furnace any introduction of cooling fluid from a burner to shut down compromises the efficiency of the process by causing a dilution of the reactive gases. This results in loss of production, accelerated corrosion and increased air pollution. In addition, a low gas velocity at the outlet of the duct is the cause of a bad mixture of the gases and, consequently, of a poor efficiency of the combustion reaction,

  which also causes an increase in atmospheric pollution.

  pheric. On the contrary, maintaining a high velocity of the gases over the entire path traveled and even at low flow rates, causes a better mixing with the air resulting in a short flame, a higher flame temperature and better performance.

of reaction.

  According to another characteristic of the invention, the

  Minimum inside diameter of the second floor is at least

  equal to the inner terminal diameter of the first stage.

  It is thus possible to obtain a much better continuity in the decay of the speed of the mixture downstream of the first

floor.

  According to another characteristic of the invention, the burner comprises separate adjustment means of the injection sections of the

gas and air.

  According to another characteristic of the invention, the means for adjusting the gas injection section is a sliding cover located on the orifice of the gas supply nozzle, the movement of this orifice being controlled by the gas injection nozzle. intermediate of a manual or motorized control, controlled or not with the pressure in the

leads 4 Dar example.

  According to another characteristic of the invention, in each combustion air introduction stage, the air passes through a register provided with tilting vanes making it possible to modify the

  injection section by means of a control lever.

  According to another characteristic of the invention, for each stage, the divergent in which the mixture flows has a very narrow neck, calculated for the lowest requested flow rate.

at the burner.

  According to another characteristic of the invention, the commissioning of the stages can be either discontinuous or made continuous by a servo-control device for the butterflies.

air flow adjustment.

  The characteristics of the gas burner which is the subject of the present invention are described in more detail with the aid of the attached drawing showing a schematic section of such

burner.

  According to this figure, the burner consists of a device 1 for the arrival of the gas according to the arrow A, and a device 2 for the arrival of the combustion air according to the arrows B. The gas that arrives through the device 1, as well as the air arriving through the device 2 are mixed in a divergent duct 3 from which the mixture AB flows and which will be described more

  in detail later in this presentation.

  The device for supplying the pressurized gas 1 is a nozzle 4 whose end 5 opening into the diverging duct 3 is capped with a sliding lid 6 capable of moving longitudinally along the axis II of the nozzle 4. longitudinal displacement of the cap 6 on which the pressurized gas injection section depends is controlled by means of a control system

  7 connected to the cover 6 by an axis 8.

  The combustion air supply device consists of a box, from which the air arrives in the divergent duct 3 by passing through a register 10 provided with tilting vanes, making it possible to modify the injection section of the air in the divergent at

using a control lever 12.

  According to the invention, and to allow the burner to be used over a very wide adjustment range and in particular for very low heat flow rates, the diverging duct 3 can

  decompose into two stages of introduction of the combustion air.

  According to the figure, the diverging pipe 3 comprises two stages 30 and 31, all the gas being injected into the first stage 30, while the air can be injected successively into

the floors 30 and 31.

  It is quite obvious that the diverging conduct could have more than two floors, or that the introduction of the gas could be staggered on the two floors without going out

of the scope of the invention.

  To allow a staged introduction of air

  B bustion, the box 9 is subdivided into two compartments 90 and 91, each of these compartments being connected to one of the floors

  30 or 31 of the diverging pipe 3.

  Each of the compartments 90 or 91 is connected to a register provided with tilting vanes 11 which make it possible to modify the section

injection by means of levers 12.

  Of course, the invention is not limited to the embodiment described above and shown, from which we can provide other variants, without departing from the scope

of the invention.

  The invention will be better understood with the aid of the following nonlimiting example

EXAMPLE

  A burner according to the invention comprises a nozzle 5 with an inside diameter of 75 mm and a cap 6 for adjusting the

flow of the nozzle.

  The temperature of an acid gas containing about 60% of hydrogen sulphide and 40% of carbon dioxide being of 400C and its pressure of 60 millibars above the pressure reigning in the

  the maximum permissible flow rate is 1641 Nm3 / h.

  For a flow of acid gas of about 160 to 540 Nm3 / hour, the first stage 30 is admitted through the compartment 90 a flow

  air proportional to the gas flow rate of 240 to 810 Nm3 / hour.

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  The second stage then receives only a small flow of cooling air and a perfectly stable flame front is established

in the first floor.

  For an acid gas flow rate greater than 540 Nm3 / h, the maximum air flow rate of the first stage 30 is maintained and the excess air necessary for combustion in the second stage 31 is admitted by the compartment 91. The flame front is moving

  then and stabilize in the second floor.

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Claims (6)

  1 - Forced-air gas burner whose heat flow can   vary over a very wide range of adjustment and in particular   operable for very low flow rates, a gas burner comprising a gas supply device and an air inlet device, and a divergent duct in which the air-gas mixture is carried out, characterized in that the diverging terminal section has at least two   stages of introduction of air and / or fuel gas.   2 - burner according to claim 1, characterized in that the   minimum inside diameter of the second floor is at least   equal to the inner terminal diameter of the first stage.   3 - burner according to any one of claims 1 and 2, carac-   characterized in that it comprises separate adjustment means   gas and air injection sections.   4 - burner according to any one of claims 1 to 3, charac-   characterized in that the means for adjusting the gas injection section is a sliding cap situated on the orifice of the gas supply nozzle, the movement of this orifice being controlled by means of a manual control or motorized,   enslaved or not to the pressure in the conduit 4 for example.   Burner according to one of Claims 1 to 4,   characterized in that, in each stage for introducing the combustion air, the air passes through a register provided with tilting vanes making it possible to modify the injection section by means of a control lever.   6 - burner according to any one of claims 1 to 5, charac-   characterized in that, in each stage, the diverging pipe has a very narrow neck calculated for the lowest flow rate asked the burner.   7 - burner according to any one of claims 1 to 6, charac-   characterized in that it comprises a servo-control device   butterflies for regulating air and gas flow.