EP2310116B1 - Device for continuously mixing fed-out natural gas with oxygen to produce a burnable gas for heating pressurized natural gas before or after the expansion thereof - Google Patents

Description

The invention relates to an apparatus for the continuous mixing of stored natural gas with oxygen to a fuel gas for heating the pressurized natural gas before or after its expansion, with a closed mixing vessel with connections for a natural gas supply, an oxygen introduction and a fuel gas discharge.

Natural gas is to be preheated prior to pressure reduction during the withdrawal, eg from underground storage tanks, in order to compensate for the Joule-Thomson effect. It is known to continuously burn a portion of the Ausspeicherstromes in a so-called "inline reactor" under controlled supply of oxygen. In this process, temperatures of up to 400 ° C are achieved by catalytic conversion of oxygen with natural gas directly in the gas stream taken from the memory. The heat is used by direct mixing of the hot combustion gases in the cold gas stream for continuous heating. This procedure is in the EP 0 920 578 B1 described.

After US 2005/1095185 A1 Also, a mixing device upstream of a catalytic combustion device is known, wherein the natural gas is arranged in the center of the mixing zone. Downstream of the natural gas supply is a Mixed insert of corrugated material used. A bed of ceramic grain material is arranged as a thermal barrier in front of the catalyst.

It has been found that auto-ignition of the gas mixture in a process of metered addition of oxygen to natural gas can never be completely ruled out. The auto-ignition of natural gas-oxygen mixtures is pressure and temperature dependent. An increased oxygen concentration already leads to a reaction and burning in the gas stream, and thus to a pressure and temperature increase, even without a catalyst. Under the real technical conditions of a natural gas Ausspeicherungsanlage, with the currently known and available measuring and control technology and in conjunction with the safety technology that can be realized with today's known means, is a metered addition of oxygen in natural gas by means of a burner, a diffusion burner or a Premixing chamber, as it is in the EP 0 920 578 described, not sure controllable.

Due to the high temperatures that occur at a direct ignition at the exit point of the oxygen, the free flow of oxygen into the natural gas flow is not recommended. In addition, the use of known ignition and monitoring devices fails after a very short time.

On the other hand, it has been found that a "cold" dosage of oxygen into the natural gas for exothermic reaction on a catalyst leads to no success. However, the preheating of the natural gas-oxygen mixture to the activation temperature of the catalyst at a constant concentration before the relaxation periodically leads to an uncontrollable auto-ignition and therefore not to the desired catalytic conversion of the mixture of natural gas and oxygen.

The invention has for its object to provide a device that ensures a safe dosage of oxygen in continuously flowing natural gas.

This object is solved by the features of patent claim 1.

Further embodiments and advantageous developments of the device according to the invention are specified in claims 2 to 11.

In accordance with the invention, the mixing section provided in the known "in-line heating", that is to say within a natural gas line, is now designed as a closed mixing container. Its function is to supply a cold natural gas stream, which is introduced into the mixing vessel, high pressure oxygen in the gaseous state at a temperature of about 5 to 30 ° C via the oxygen inlet and the natural gas within the mixing chamber of the container via the manifold at a High pressure of eg To mix 70 to 170 bar.

The mixing chamber is complete and the manifold at least partially filled with a self-ignition complicating bed of ceramic grain material. The bed of ceramic grain material ensures an increase in operational safety; because it offers an inert behavior, so it does not participate in a reaction with one of the gases to be mixed. It shows a very low and therefore advantageous thermal conductivity, so that the released in a possible ignition within the mixing container heat can not damage the container wall.

The material also has the advantageous property of a high melting point, whereby, with a possible ignition, no formation of channels by melting is possible.

Part of a safety device of the device are also equipments of the mixing chamber of the container with temperature sensors.

Furthermore, the mixing container is advantageously designed as a stationary container, which has at the bottom the connection for the natural gas supply line and at the top the connection for the fuel gas discharge.

The advantageous working principle of the device allows a cold mixing of oxygen and natural gas at high pressures, taking into account a certain concentration centrally in a equipped with the ceramic bed and with safety monitoring by probe standing container. The introduced in the container bed with insulating and inert effect is, especially in standing containers, safe to discharge and wear-resistant by its high density at small defined cavities. This prevents the propagation of flames within the container should auto-ignition occur. In addition, the container inner wall is temperature-monitored.

The fact that the container is, the bed remains constant during operation obtained and always has small cavities, because then, if particles of the ceramic grain material would be torn by the sharp flow, immediately slipping takes place.

This slipping is further improved by the fact that the ceramic grain material of the bed is a high-density alumina in spherical form with a homogeneous particle size distribution of 1.5 to 3 mm.

Another, the safety against ignition during the mixing of the fuel gas from natural gas and oxygen within the container serving measure provides that the mixing zone on the inflow side has a flow velocity in the mixing zone increasing, concentric cross-sectional constriction.

The flow velocity of the incoming natural gas is increased by the concentric cross-sectional constriction, which can also be referred to as built-in reduction, in the area before the actual mixing zone in the container so that the turbulence caused in the natural gas flow optimum mixing with the incoming oxygen in the mixing tube surrounding area , The range of ignitability of the natural gas-oxygen mixture, So the fuel gas, is thus very fast drive through. In addition, the inert ceramic fill prevents flame development.

The distributor tube has outlet slots in its tube wall, which runs parallel to the surrounding walls of the mixing container. Advantageously, the outlet slots are dimensioned so that particles of the bulk ceramic grain material present in the distributor tube can not be torn through the outlet slots by the oxygen flowing in the distributor tube or can be pressed from the outside into the distributor tube. The exit slits produce the effect of a screen while at the same time having an advantageous effect on the mixing effect of the oxygen flowing out of the distributor tube into the mixing zone through the exit slits.

The mixing container is advantageously designed double-walled in the region of the mixing zone of the mixing chamber, wherein an insulating material is arranged between the outer mixing container wall and the inner mixing chamber wall. The inner mixing chamber wall may e.g. consist of a stainless steel sheet, which is welded circumferentially with the outer mixing tank wall, wherein in the space a lining with ceramic wool to protect the mixing chamber wall against thermal influences is arranged.

All measures and installations have the effect that the risk of auto-ignition in the continuous mixing of oxygen in a natural gas stream within the mixing vessel of the device according to the invention are reduced.

Contributes to this in a particularly advantageous manner, that at the inner mixing chamber wall in a region which corresponds to the arrangement of the outlet slots on the manifold, several temperature sensors are arranged evenly distributed with protective tube on the circumference of the outer mixing container wall.

Preferably, in the region of the oxygen outlet slots in the inner mixing chamber wall, three circumferentially evenly distributed, fast-responding temperature sensor with protective tube are welded. This makes it possible to monitor the temperature increase during a possible ignition of the natural gas-oxygen mixture permanently and safety-oriented. For this purpose, the temperature sensors are integrated in a safety device.

The safety device has with particular advantage a connected to the oxygen inlet nitrogen purge. Upon reaching a temperature rise detected in the mixing tank by the temperature sensors, the oxygen addition by the safety device is immediately stopped and a purging process with nitrogen is introduced into the oxygen introduction port.

Furthermore contributes to the development of the solution according to the invention also in that in each case a redundant measuring and control device is integrated in the oxygen inlet and in the natural gas supply. This allows a precise addition of the oxygen to, for example, a maximum of 3 mol%. The safety device limits this oxygen concentration, wherein the monitoring is performed by the measuring and control device. In the pipes for the introduction of natural gas and oxygen, two different series-connected measuring methods of flow measurement, differential pressure measurement on a diaphragm and ultrasonic measurement, are used, the values of which are processed in the safety device. As a result, on the one hand given a redundancy and on the other hand there is a possibility of comparison.

The preselected parameters of the mixing process are, determined by experiments, under the auto-ignition of the fuel gas mixed from natural gas and oxygen, wherein the state in the process is permanently monitored by the safety-related measurement technique.

Fig. 1:

eine Ansicht eines geschlossenen Mischbehälters einer Vorrichtung zum kontinuierlichen Mischen von ausgespeichertem Erdgas mit Sauerstoff;

Fig. 2:

eine Seitenansicht des Mischbehälters im Längsschnitt, und

Fig. 3:

eine schematische Ansicht der Vorrichtung zum kontinuierlichen Mischen mit schematisch angedeuteten, den Anschlüssen für eine Erdgaszuleitung und eine Sauerstoffeinleitung vorgeschalteten Armaturen.

An embodiment of the invention, from which further inventive features arise, is shown in the drawing. Show it:

Fig. 1:

a view of a closed mixing container of an apparatus for continuously mixing stored natural gas with oxygen;

Fig. 2:

a side view of the mixing container in longitudinal section, and

3:

a schematic view of the apparatus for continuous mixing with schematically indicated, the connections for a natural gas inlet and an oxygen inlet upstream fittings.

Fig. 1 shows a view of an apparatus for continuously mixing stored natural gas with oxygen to a fuel gas for heating the pressurized natural gas before or after its relaxation. About the equipped with a flange 3 connection 8 for a natural gas supply into the mixing vessel, and via the equipped with flange 4 connection for an oxygen inlet 9 to the mixing vessel 2, the mixing section 1 is formed, which ends in the fuel gas discharge line 10 with flange 15.

The mixing container 2 forming the mixing section 1 is a standing container with legs 5, at the lower ends of which base plates 6 are located, which serve to anchor the mixing container 2 on a standing surface.

Legs 5 and bottom plates 6 form a stand for the mixing container 2, the bottom flows over the flange 3 and the natural gas supply 8 natural gas, and is entered into the via the oxygen inlet 9 with the flange 4 oxygen, which mixes in the mixing tank with the natural gas becomes.

The gas mixture forms a fuel gas which is discharged via the fuel gas discharge line 10 with the flange 15 from the mixing container 2.

At the periphery of the mixing container 2, distributed evenly around the circumference, temperature sensor 7 is attached.

Fig. 2 shows a side view of the vertical container 2, which forms the mixing section 1, in a longitudinal section. The same components are designated by the same reference numerals as in Fig. 1 ,

Fig. 2 indicates that in the interior of the mixing container 2, a mixing chamber 11 is formed, which is filled with a bed of ceramic grain material. The bed of ceramic grain material is indicated by microcircuits drawn.

In the mixing zone forming a center of the mixing chamber 11 is a connected to the terminal 9 for an oxygen introduction manifold 12 is arranged. The free end side of the manifold 12 is closed with an end cap 13. The portion of the pipe wall of the manifold 12, which runs parallel to the surrounding walls of the mixing container 2, is provided with outlet slots 14.

The manifold is also with the bed of ceramic grain material, here a high-density alumina in spherical form with a homogeneous grain size distribution of 1.5 to 3 mm filled, as indicated here.

To prevent the discharge of the bed, the inserts serve 30 and 31 in the inlets 8, 9 and the insert 32 in the outlet 10. At the same time carried by the inserts 30, 31 and 32, a homogenization of the flow in the manner of a multi-aperture.

Fig. 2 illustrates further that the temperature sensor 7 with protective tube 15 in a region corresponding to the arrangement of the outlet slots 14 in the manifold 12, are arranged in the mixing vessel wall 16.

The mixing container 2 is double-walled in the region of the mixing zone of the mixing chamber 11, an insulating material 18 being arranged between the outer mixing container wall 16 and the inner mixing chamber wall 17.

The mixing zone formed in the interior of the mixing chamber has on the inflow side a concentric cross-sectional constriction 19 which increases the flow velocity in the mixing zone. The cross-sectional constriction 19 may be e.g. a formed from sheet metal funnel, which is placed in the lower end of the mixing vessel directly over the mouth of the natural gas feed line 8.

Fig. 3 shows a side view of the entire device with mixing tank and its connections for a natural gas inlet 8 and for an oxygen inlet 9 with the respective upstream of these connections fittings a safety device, with nitrogen flushing system and with control valves for the introduction of oxygen.

The same components are again with the same reference numbers as in Fig. 1 and Fig. 2 designated.

The lower connection for the natural gas supply line 8, a check valve 20 is connected upstream and a shut-off valve 21, in front of, seen in the direction of the natural gas supply line, again a valve for measuring quantity 22 is arranged.

The supply of natural gas takes place in the direction of arrow 23.

In the oxygen inlet 9 with the input flange 4, a non-return valve 20 'is again arranged on the inflow side, in front of which, seen in the inflow of the oxygen, a shut-off valve 21' and a device for measuring oxygen quantity 22 'sits.

The latter fittings are components of the safety device of the device, which also includes the here only indicated nitrogen extinguishing system 24 with the outlet side existing fittings 25 and 26.

Another device for oxygen quantity measurement is designated 22 ".

A control valve for the introduction of oxygen, which controls the inflowing in the direction of arrow 27 oxygen in the amount is denoted by 28.

These valves are part of the safety device, which can control and control technology to work according to a program with which the measured values of the temperature, the pressure and the amount of oxygen and the natural gas introduced into the mixing chamber processed and the corresponding shut-off and control fittings 21st and 28 and 21 ', respectively.

Claims (12)

1. A device for continuously mixing fed-out natural gas with oxygen to produce a burnable gas for heating the pressurised natural gas before or after the relaxation thereof, comprising a mixing section with connections for a natural gas supply line, an oxygen in-feed line and a burnable gas discharge line,
   characterised in
   that the mixing section (1) is constituted as a closed mixing container (2), which comprises a mixing chamber (11), at the centre whereof, which centre constitutes a mixing zone, a distributing pipe (12) for oxygen is disposed which is connected to the connection (9) for an oxygen in-feed line,
   that the mixing chamber (11) is filled completely and the distributing pipe (12) is filled at least partially with a packing of ceramic granular material,
   that the mixing chamber (11) of the mixing container (2) is equipped with temperature measuring sensors (7) for a temperature measurement, and
   that the mixing container (2) is constituted as a standing container which at the bottom comprises the connection for the natural gas supply line (8) and at the top the connection for the burnable gas discharge (10).
2. The device according to claim 1, characterised in that on the inflow side the mixing zone comprises a concentric cross-sectional narrowing (19) which increases the flow rate in the mixing zone.
3. The device according to any one of claims 1 and 2, characterised in that the distributing pipe (12) comprises outlet slits (14) disposed in its pipe wall which runs parallel to the surrounding walls of the mixing container (2).
4. The device according to any one of claims 1 to 3, characterised in that the ceramic granular material of the packing is a highly compressed aluminium oxide in spherical form with a homogeneous particle size distribution of 1.5 to 3 mm.
5. The device according to claim 4, characterised in that the connection (9) of the distributing pipe (12), the connection of the natural gas supply line (8) and the connection for the burnable gas discharge line (10) are fitted with sieve-like inserts (30, 31; 32).
6. The device according to any one of claims 1 to 5, characterised in that the mixing container (2) is constituted double-walled in the region of the mixing zone of the mixing chamber (11), wherein an insulating material (18) is disposed between the outer mixing container wall (16) and the inner mixing chamber wall (17).
7. The device according to claim 6, characterised in that, on the inner mixing chamber wall (17) in a region corresponding to the arrangement of the outlet slits (14) on the distributing pipe (12), a plurality of temperature measuring sensors (7) with a protective tube (15) are disposed uniformly distributed around the circumference of the mixing container wall (16).
8. The device according to any one of claims 1 to 7, characterised in that the temperature measuring sensors (7), with regard to their measuring functions, are integrated into a safety system.
9. The device according to claim 8, characterised in that the safety system comprises a nitrogen flushing system (24) which is connected to the oxygen in-feed line (9).
10. The device according to claim 9, characterised in that a measuring and control device is integrated in each case into the oxygen in-feed line (9) and into the natural gas supply line (8).
11. The device according to claim 10, characterised in that each measuring and control device comprises at least one through-flow quantity measuring device (22, 22', 22").
12. The device according to any one of claim 8 to 11, characterised in that the safety system is equipped with at least one control valve (28) for the oxygen in-feed line.

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