DE1526009A1 - Method of burning flare gases of varying pressure - Google Patents

Description

(MARRIAGE LTJMMJS COMPANY,
385 Madison Avenue, New York, New York 10017 (V.St.A.)

Method of burning flare gases of varying pressure

The invention relates to a method for economical and practically smokeless combustion of refinery waste gases or waste gases from chemical plants and in particular on practically smokeless combustion of flare gases, i.e. exhaust gases that are to be flared off, over the full range of 100 percent of the load for which the torch is designed. The method and the device according to the invention can be used with essentially all types of flare gases. It will be effective and economical handling and combustion over the full range of the structurally designed flare load without the occurrence of pollution or smoke problems or other difficulties. Another

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The advantage is that the flaring process is the The view of the surroundings, i.e. the view of passers-by on public streets, paths, etc., is hidden.

In the method according to the invention, the Flare gases are divided into a plurality of individual streams, the number of these streams being the amount of the one to be burned Gas is proportional. Each gas stream is fed to a set of venturi burners; the burner sets together have a total combustion capacity that is equal to the designed maximum flare load. That Gas is then burned in the burners with a sufficient amount of primary combustion air in such a way that all burners work in the appropriate area for a smokeless incineration.

Saffinery off-gases have heretofore been burned in many different types of flares. There were many devices designed to eliminate puff when over a certain range of design capacity the torch is flared. For example, an arrangement previously used comprises an injection device for supplying water vapor or water sprays around the torch flame to cover the abdomen. Smokeless combustion can be achieved with multi-jet flares, but these devices are on a relatively small and constant flare load

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limited. Such multi-jet flares are impractical for embodiments that are designed for high flare loads, since operation under such conditions becomes cumbersome, difficult to manage and expensive.

Incineration pits are also sometimes used for flaring. These simply consist of a rectangular one or square hole about 3 m or less deep that is in a remote area of the Refinery is located. Gases that are flared in such pits burn due to the lack of combustion air in the immediate area of combustion almost constantly with the development of a considerable amount of smoke. Flares positioned close to or on the ground with water injection are also used for flaring refinery gases and these arrangements consist essentially of three chimneys or draft tubes, generally coaxial Arrangement. The flare gas is burned in the inner and middle chimneys; the outer chimney forms a shield for the flame and is generally no more than 9 m high. Through a nozzle water is sprayed into the middle of the flame and this covers the smoke that has formed. Such facilities work essentially only over a range of about 20 percent of the designed flare capacity approximately smokeless.

There are different methods and arrangements

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specified for the automatic control of flare systems been. In one case, a flare is automatically activated according to the gas pressure in the main flare pipe or head piece ignited by a gas generator. In this device, the end of the torch header is at its upper end portion divided into several laterally and upwardly reaching branch pipes; the gas supplied to this torch is passed through diving bells (immersing bells) that sink in sealing fluids. In another arrangement the same a flare chimney igniter is generally provided. The chimneys or draft pipes themselves are from conventional cylindrical design, but with two chimneys are provided and an auxiliary chimney used to provide a substantially continuous igniter for the normal exhaust gases, and a second larger chimney for handling larger volumes serves. The ignition of the second chimney is carried out through a venturi pipe to the gas line and there are means provided to introduce the necessary air into the venturi tube.

As can be seen from the above explanations, the previously known methods and devices generally the disadvantage that they are only in a proportionate manner work smokelessly in the narrow part of the designed flare load range, and in many cases beyond

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are costly to manufacture and operate.

The invention is based on the object of a method and a device for flaring refinery or to create other exhaust gases that do not have the deficiencies and disadvantages of the known methods and devices, in particular a method and a device that is practically smokeless and invisible to the environment Flaring of refinery or other exhaust gases over the Allow the entire area for which the torch is designed. In connection with this, the invention aims to provide information a mode of operation and a device for practically smokeless combustion of refinery or other waste gases, which works flawlessly even with gas fluctuations within very broad limits and is both economical erect as well as operate.

Other features and technical advantages diteeer Invention emerge from the following description of preferred embodiments.

By 'the invention, the disadvantageous side effects of the low adaptability of Venturi brewers, which are inherent in such burners, eliminated. As is known, such a burner needs for a smokeless combustion a certain amount of intake air (inspirated air). Smoke formation is caused by incomplete Burns the gases. If a sufficient amount

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can be mixed in a suitable manner with the gases to be burned in air, no smoke is formed. A given Venturi-type burner is therefore always for a specific one Gas flow, and as a general rule that it is less than about 60 percent of this gas flow rate not working satisfactorily. The reason for this is that the kinetic energy of the gas that the jet nozzle leaves, then not enough to suck in the amount of air required for smokeless combustion. To the To overcome this difficulty, a considerable number of Venturi burners are required to make the design Flare capacity to be covered completely; in order to always stay within the operating range in which the burners are satisfactory A special method has been developed to work one or more of these burners, depending on the amount of the gas to be flared.

The total number of burner sets and the number depend on each device present in the individual case on burners per set according to the special requirements and Conditions of this device. In the embodiment of the invention described below, as an example a device with six sets of burners in which different sets contain different numbers of burners, explained.

In operation, the first burner set is very processing

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small amounts of gas such as would normally be flared. If more gas needs to be flared, more will go Burner sets in operation. The device is designed so that the second burner set comes into operation when the pressure in the torch tube is high enough to draw in the to ensure the required amount of air in the burner set required flow rate. The third burner set comes into operation when the total load on the torch is 60 percent of the cumulative design capacity of the first exceeds both burner sets. The same applies to the rest of the burner sets.

In one embodiment of the invention, there is a novel method of controlling the start-up of the burners intended. However, this is not an essential feature of the invention. Preferred in this Embodiment, a sealing or shut-off drum is used, the water or any other contains suitable liquid. This drum is provided with several compartments, one for each Burner set, the gas flow to each of the burner sets by the height of the assigned to each individual burner set shut-off liquid is regulated, i.e. opened or closed. Although normally used as a barrier fluid Water is used, other liquids can also be used, and in my cases this is even necessary,

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for example when the flare gases have a temperature below ⁰ ° C. The liquid level is in all compartments

4k.

equal and is maintained by a loop seal (loop seal), the height of which is at least Should correspond to 200 percent of the highest counterpressure acting on the shut-off drum.

The height of the water level is still maintained by a level controller, which is a constant Guaranteed water content in the drum. In the case of a very small flare load, i.e. with a gas pressure that is not sufficient for a smokeless operation of the first burner set, the gas velocity can be reduced by the introduction of Water vapor can be maintained. The following compartments of the shut-off drum filled with water are at kept the minimum pressure that is considered necessary for satisfactory operation of the corresponding burner set i.e. when two burner sets are in operation and the flaring is at least 60 percent of the cumulative Design capacity of the first three burner sets, the water stop in the third compartment is blown out, so that the third burner set comes into operation. That. The method is thus operated and the device is designed in such a way that that when an overload occurs, the already in operation If the burner sets are in place, the next burner set is • closed so that there are always enough burners in operation

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to handle the volume of gas to be flared and faultless to burn.

In another embodiment of the control device for connecting the burners, analog control devices are used (analog control modules) are used and this embodiment is useful in such systems used, which are equipped with such a control system.

The burners themselves are arranged in a novel way so that the flame area is subject to natural draft secondary combustion air is supplied to supplement the primary air drawn into the burners. With the described Embodiment are the burners in uniform cuts in a refractory wall in an open pit of arranged about 3 m deep »The minimum speed of the Brenner is about 3 m / sec in her neck area. A natural one Draw is made by using walls of refractory material with holes under the burners to allow air

lead to the bottom of the pit, brought about. In addition, there are side walls with flow channels arranged therein intended for cooling and air intake.

The invention is described below with reference to two embodiments in conjunction with the accompanying drawings further explained.

Figure 1 shows a plan view of a burner

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arrangement according to the invention.

Figure 2 is a section along line 2-2 of the Figure

FIG. 3 is a section, looking from the side, through a shut-off drum loaded with water for controlling the flow of flare gases to the device shown in Figure.

FIG. 4 shows another method for regulating the flow of Flare gases using analog control devices, applied to a system for the absorption of Natural or natural gas.

In FIG. 1, a burner device, generally designated 10 and designed according to the invention, of rectangular shape with two end walls 12 and two side walls 14 is shown. Numerous burners 16 are arranged in the side walls 14 in a manner explained in more detail in connection with FIG. In the embodiment shown in FIG. 1, the entire device is located below floor level and accordingly supporting walls 18 are provided parallel to and at a distance from the side walls 14. As a result, the entire flaring process cannot be seen from the outside. Of course, the device can also be arranged at floor level or any suitable intermediate height or above the floor, in which case

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Side walls 14 of suitable height are provided to achieve the same result. It can be seen from the drawing that the burners 16 are supplied with flare gas through six separate lines, each line feeding an increasingly large number of burners. As already mentioned, the size and the number of lines and the number of burners per line are of course dependent on the size of a given device or the capacity of a device to be built and the composition of the flare gas. In the embodiment shown, a line 20 of relatively small thickness supplies a head or distribution piece 22 which carries gas to three burners 16. A line 24 supplies a distributor 26, which in turn feeds 5 burners, while lines 28, 32, 36 and 40 supply associated distributors 30, 34, 38 and 42 with gas. The dimensions of the lines 20, 24, 28, etc. are approximately proportional to the number of burners 16 which are fed by the line in question. In the embodiment shown, the same number of burners are connected to the distributors 38 and 42, and each of these two distributors can achieve approximately 25% of the total capacity of the system.

While the side walls 14 are made of refractory brick or any other suitable refractory material consist, the walls * 1b, which together with the walls 14 Form channels 44, of any suitable dense material,

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γ- 12 -

such as concrete or the like. Manufactured. The end walls 12 are "suitably made of a refractory material such as vermiculite concrete, and they are provided with asbestos flow tubes 46 * which are open at their lower end to allow additional secondary combustion air to introduce.

The arrangement of the individual burners in the walls 14 is illustrated in FIG. There you can see that the support wall 18 and the fire wall 14 form a channel 44 between them, which allows air to be sucked in. Line 40 supplies manifold 42, which in turn feeds a group of burners through lines 46 '(only one line shown) feeds. The lines 46 ′ lead downward through the channel 44 and terminate in the form of a narrowed mouth 48 in the inlet section or throat of the venturi burner, indicated generally at 50. The burner consists of Usually from three parts, namely an inwardly inclined portion 51, a neck portion 52 and an outwardly widened Section 54. An auxiliary ignition tube 56 is used for ignition of the individual burner sets. Through wall or masonry openings 58 at the bottom of the wall 14, additional air is from the Channel 44 sucked into the interior of the arrangement) so that additional combustion air is available in the chamber stands. It can also be seen from FIG. 2 that the end walls 12 have openings for the tubes 46 at the bottom, the additional secondary

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Introduce combustion air and also the end walls 12 cool.

As explained in connection with FIG. 1, the gas is fed to the six burner sets through six separate pipelines, a control device serving to feed the burners with gas only when this is necessary. An embodiment which can be used for this regulation is shown in FIG. The device according to FIG. 3 comprises a sealing drum 60 charged with water, which is divided into six compartments 62, 64, 66, 68, 70 and 72. From the Figure 3 it is apparent that these compartments by gradually increasing Grosse are ₀ The same is true for the cable connections or conduits leading to the compartments. In each compartment, water is maintained at a given level by means of a conduit 71j which extends the length of the drum, leads into each compartment and terminates in an external loop or gooseneck seal, indicated generally at 81. A constant water filling is maintained in the drum by means of a measuring tube 76 and a level regulator 78 which controls a water supply line 80. The height "1" of the loop or gooseneck seal 81 should correspond to at least a value of 200 percent of the maximum counterpressure acting on the shut-off drum in order to prevent water from being blown out of the seal

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to prevent the sewer pipe if the system is flared at the full capacity for which the system is designed.

Refinery gas to be flared is directed to a header or manifold 82, with entrained liquids being removed therefrom through line 83. The gases in the manifold 82 flow in six lines 84-94 of increasing diameter which lead into the shut-off drum 60. Inside the drum 60, these lines extend to a gradually increasing depth below the surface of the water level maintained therein. A branch pipe leading back to the surface of the water forms a flow channel for the flare gases when the barrier is blown out so that the gases do not have to flow through the water. When the flare gas pressure in manifold 82 is quite low, the gas flows into line 84, which ends just a short distance below the liquid level in compartment 62. The gas blows out the water barrier and flows through the branch line into the gas space of the compartment 62 and then into the outlet line 20. If the gas pressure in the manifold 82 is insufficient to blow out the barrier in the second compartment 64-, the compartment 62 is that only compartment of the shut-off drum 60 that is in operation. If the pressure in the manifold 82 is too low even for the compartment 62, the flare will not operate. A desire 96 controls a valve 98 in a water vapor line 1OO so that a

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Minimum nozzle speed ensured for the first set of torches will. This characteristic is not essential, however, since the amount of belly that is so small Torch loading could be formed by being obscured by the perimeter walls.

In the state shown in FIG. 3, the gas entering in lines 84 and 86 has a sufficient amount Pressure to blow out the water barriers in compartments 62 and 64- so that flare gas only flows through lines 20 and 24- into the burner arrangement (FIG. 1). In the rest Lines 88-94- the water barriers with different water levels are still closed. Such a state can be viewed as the state of normal flare gas flow.

The first set of burners burns the smallest amount of gas and each subsequent set burns an increasingly larger one Proportion of gas; the height of the water barriers in the individual compartments is adjusted accordingly. A typical one An example of the capacity of the individual burner sets is given in Table I below:

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Table I.

sentence Proportion of designed
Full load, through the
corresponding Venturi
Torch set flared
will, % Cumulative portion
the designed
Full load, % 1. Il 5 5 2. Il 8th 13th 3. π 12th 25th 4th Il 20th 4-5 5. Il 25th 70 6th 30th 100

Before the first set of burners goes into operation, the pressure in the flare manifold 82 must be high enough to draw in the volume of air required for premixing. The amount of air sucked in is determined by a force balance and the dimensions of the Venturi throat. The area of the venturi tube in relation to the area of the jet nozzle is important because the effect of the jet speed is lost if this ratio is too large. Before the second set of burners comes into operation (ie, before the barrier in compartment 64 is blown), the pressure in the flare manifold 82 must increase to such a level that the first two sets of burners can operate at at least 60% of their cumulative capacity. As mentioned above, backs up

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this is a smokeless combustion. For the example given in Table I, the pressure in manifold 82 should be 0.6 χ 13 = 8 % of the full flare load for which the flare is designed. The operating range of the first set of burners is therefore 5-8 % of the designed full load of the torch *

The jet speed is through the usual one equation

v = c y2g! Th (1)

given, where

ν = gas velocity, in cm / sec, c = nozzle factor,
Ah = pressure drop, in cm, of the flowing medium and

S = 931 cni / sec ~

mean.

If the pressure drop between the flare manifold 82 and the burners can be neglected, the pressure drop across the nozzle is substantially equal to the static pressure in the flare manifold. If the static pressure is equal to h when the first burner set is started up (ie at 5% of the designed full load), the second set should start operating when the pressure reaches h (8/5) "; this is, as explained above, 8 % of the designed full load The pressures at which the other burner sets

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- 13 -

come into operation, and the associated heights of the locks in the various compartments there are corresponding '.' 'ice calculated.

As a result of maintaining a constant water level in the drum, the lock closes automatically in a compartment under consideration when the pressure in the Flare gas distributor 32 drops below the pressure of the water barrier height, so that then the flaring through the corresponding Burner set stops. Accordingly, the burner sets work at Smokeless in all conditions.

If in any given facility the composition of the flare gas is such that hydrocarbons Anyone can condense in the shut-off drum Compartment through separate lines (not shown) water vapor from the line 100 are supplied.

An alternative to the embodiment according to FIG. 3 is shown schematically in FIG. These shows in a simplified form the input part of a plant for the absorption of natural or natural gas. As is well known, the Wellhead pressures of natural gas wells are subject to wide changes, on the other hand, however, the treatment and processing plants are working most effective and economical at a constant load. There are analog and digital devices have been developed that are capable of processing equipment to maximum useful power at flow rates that spread widely

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bad uraoi

change over the design area of the system, to regulate. For the absorption of natural gas, for example, analog control modules (analog control modules) have been developed that regulate the flow of poor oil to the absorber in such a way that the production is brought to a maximum value, up to full design capacity of the treatment plant. If the Gas flow exceeds this value, gas must be flared. the.

According to the greatly simplified representation in Figure 4- is natural gas from a line 120 with glycol, which through a line 122 is added and removed in a drum 124 is, dried and the dried gas flows through a line 126 to an absorber 128. A flow meter and recorder 130 routes a signal to a plurality of analog control devices (analog modules), which are collectively designated by 132, and these bring on the basis this information and other signals (not shown) from other parts of the plant control the flow of poor oil by means of a Flow regulator / 134- to the corresponding maximum value.

If the full design capacity is exceeded, a signal is also sent from the flow meter 130 to an analog control device 13S, which prevents a sudden increase in the amount of gas flowing to the absorber per unit of time. So if the supply of feed gas, V ^, suddenly occurs increases, device 133 permits flaring

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a portion of the gas, V ₂ J over a period of time t ^; During this period, the outflow of liquid from the absorber trays adjusts to a changed poor oil supply at the top of the absorber. After the period ty. the gas flow to the flare is reduced exponentially to zero with a time constant t ~. This controller therefore causes a time delay of t. and exponential damping (time constant tp), which is regulated by the analog control unit.

Although the controller 133 in this way the flaring leads back to a minimal amount, the flaring of large volumes of gas may sometimes be necessary, see above that the present invention, which ensures smokeless combustion over the entire design area, also includes this is of great importance.

The controller 138 sends a signal to a flow regulator 140, which is a valve 142 in the flare gas line 82 opens. In this embodiment of the invention, the line 82 leads directly to the flare pit (Figures 1 and 2) and is directly connected to each of lines 20, 24, 28, 32, 36 and 40, each of these latter lines is provided with a valve (not shown). A second control unit 144 also receives the signal from the control unit 138 and the unit 144 is set so that it follows the valves in each of the aforementioned lines

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Determination of the amount of material to be flared flowing per unit of time Grass opens or closes. Of course, the control device 144 can also have its own flow measuring and recording device in the line 82 and be independent of the control unit 138.

In the figure 4 only a specific embodiment is shown, and it can for example also Digital control apply.

It can be seen that with regard to the work stages, materials and arrangement of apparatus parts or other details, as they were explained above to illustrate the invention, depending on the individual case appropriate changes or modifications can be made without departing from the scope of the invention.

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Claims (8)

Claims 1. Method of burning torchlight fluctuating pressure, characterized in that the gases in several separate individual streams, the number of which ! »! The tightness of the gas to be burned is proportional, divides each of these individual flows to a set of Venturi burners, in which the burner sets together have a total combustion output equal to the designed maximum load. for each of the burners an amount of primary combustion air sufficient for smokeless combustion of the gas that has passed through and the gas burns with the air in the burners. 2. The method according to claim 1, characterized in that the gas is up to a first predetermined upper pressure limit only the first set of torches, up to a second predetermined upper pressure limit only the first and the second set of torches, and upon further exceeding predetermined, step-wise increasing upper pressure limits in addition to the next one of the remaining burner sets and all burner sets only in the vicinity of the designed ones Operates at maximum load. 909886/0505 3. The method according to claim 1 or 2, characterized in that that one determines the pressure of the gas for the division of the gas into individual streams and after giving the Regulates pressure valves or locks in the feed lines of the individual burner sets. 4. The method according to any one of claims 1-3 »thereby characterized in that a control device is used for dividing the gas into individual streams, which has a The analogue control device that responds to the pressure of the gas and a valve in each of the channels leading to the individual burner sets Includes lines, and with the analog control unit, the valves when predetermined gas pressures of the series are exceeded after opens. 5. Method according to one of claims 1-4, characterized in that a further set of burners is only switched on when this set of burners and the burners already in operation can burn at at least 60% of their maximum output. 6. The method according to any one of claims 1-3 or 5, characterized in that the division of the gas in individual streams by means of a control device that has a liquid-filled shut-off drum with several compartments, the number of which corresponds to the number of burner sets, a connecting line between one of the compartments and one of the burner sets, a device for maintaining it 909886/0505 a constant liquid filling in the drum and a constant liquid level in each of the compartments including a water supply and a drainage barrier, in the form of a loop or gooseneck fastener, and a flare gas supply in each of the compartments which, together with the filling liquid, blocks gas flow of increasing Form a barrier in the successive compartments, includes, and thereby the gas to be flared depending on its pressure on one or more of the to the individual Burner sets leading lines distributed. 7. The method according to any one of claims 1-6, characterized in that the individual burner sets supplies the primary combustion air independently. 8. The method according to claim 7> characterized in that a »burner set is additionally supplied with a gaseous or vaporous medium and thereby the gas velocity is kept at at least 60 % of the value for which the burners are designed. 90-9886 / 05 05