EP2866903B1 - Method for diluting and/or flushing out clouds of combustible gases - Google Patents

Description

The invention relates to a method for diluting and / or discharging clouds of combustible gases, a device suitable for this purpose and the use of gas jet curtains for this purpose.

Leaks in equipment and equipment through which flammable gases can escape present a significant safety hazard, especially if there are ignition sources in the vicinity.

In the VDI reports 567, process engineering 1984, pages 391 to 412 (1985 ) H. Seifert and H. Giesbrecht report on steam curtains as a safety device against ground-level gas eruptions. It is explained that the mixing of air into low-level heavy gas clouds can be significantly increased by vertical on the ground exiting steam jets. Such steam curtains can be used as a safety device against unintentional releases of flammable or toxic gases. In a steam curtain suck the high momentum from small openings of a pipe laid in the ground exiting steam jets from one side of heavy gas and from the side facing away from leaking air and transport this mixture upwards. Above the heavy gas layer, air is mixed in from both sides. The concentration distribution can then be calculated according to the laws of a plane free jet.

In Loss Prevention in the Process Industries - Hazard Identification, Assessment and Control, FP Lees, 2nd Edition, Emeritus, Volume 1, Chapter 15.53.18 describes steam curtains that can be used to dilute leaking flammable gases that are heavier than air. The system to be protected is surrounded by a solid but slightly built wall. A horizontal steam line with a series of narrow openings is placed near the top of the wall. The wall is 1.5 m high, for example. The steam pipe is designed so that the individual beams together give a plane beam.

US 4,703,808 A describes a smoke eliminator for removing smoke, heat and combustion gases from a burning structure. In this case, the smoke eliminator comprises a heat-resistant, rigid tube with an adapter which is attached to one end of the rigid tube. This adapter is used for connection to a conventional fire hose.

DE 39 08 823 C1 describes steam curtain systems for damage reduction in the event of heavy gases released from the accident. The steam curtain system includes a nozzle tube surrounding the danger zone, a heavy gas detector system and a steam source from which steam is introduced under pressure into the nozzle tube in the event of a detected malfunction.

in the Chapter 4.6.2 "Steam Curtains" in the "Guidelines for Postrelease Mitigation Technology in the Chemical Process Industry," Center for Chemical Process Safety, AlChE, 1997, is available at pages 83 to 86 Steam and gas curtains described. Steam curtains are used to dilute gases that are heavier than air. The steam curtain should enclose the entire area where gas leakage can occur. It is again stated that a gas pipe should be mounted on a low wall at a height of about 1.5 m at its upper edge. The wall serves as a gas fence, which slows down spreading of the gas cloud and facilitates the discovery of the gas cloud. An apparatus is described in which a 6 inch (15.24 cm) diameter pipe is used, which is 5/32 inches Has holes in 4 inch (10.16 cm) intervals. Steam is applied to form the steam curtain with 250 psig of steam. To prevent the formation of static electricity, the pipelines must be well grounded. Also, hydrogen piping can be secured at junctions by an annular array of steam jets.

The object of the present invention is to provide a method for diluting and / or discharging clouds of flammable gases, the density of which does not exceed the density of air, from enclosures which, except for outlet openings, are preferably closed on all sides.

The object is achieved by the use of a generated by spraying non-combustible gases or liquids gas jet curtain for diluting and / or discharge of clouds of combustible gases whose density does not exceed the density of air from enclosures, the one or more outer openings exhibit.

The object is also achieved by a method for diluting and / or discharging clouds of flammable gases whose density does not exceed the density of air, from enclosures having one or more outer openings, in which by spraying non-combustible gases or liquids at least a gas jet curtain is generated at an outer opening, which dilutes the clouds of flammable gases located in the enclosure, or in the direction of the at least one outer opening and thus discharges, or discharges.

The object is also achieved by a corresponding enclosure with one or more outer openings with means for generating a arranged at least one outer opening gas jet curtain, wherein the gas jet curtain thinned in the enclosure clouds of combustible gases or in the direction of at least one outer opening carries and so eject, the enclosure having perpendicular outer walls and is closed at the top by a roof and at least one outer opening in the upper quarter of the outer walls is arranged. "Enclosures" according to the invention containers, buildings, etc. are understood to contain devices for the production, storage, processing or transport of chemical substances from which emerge in a flammable combustible gases whose density does not exceed the density of air at exit. The enclosures are not completely outward, ie closed to the environment or atmosphere, but have one or more outer openings. As a result, the housings z. As reactors or piping itself. The outer openings are permanently open to the environment or atmosphere and not even temporarily closed, as would be the case with doors, windows, valves, etc. The enclosure is therefore usually at the same or a very similar pressure level as the environment, or the atmosphere.

It has been found according to the invention that the dilution and / or discharge of combustible gases of low density succeed with the aid of gas jet curtains. In this case, the combustible gas which typically emanates from a leak in an apparatus is density-neutral or lighter with respect to air under identical ambient conditions (pressure, temperature) or at the outlet conditions. Thus, the flammable gas is not just a heavy gas, as defined in the VDI Guideline 3786. A heavy gas is typically at least 16% heavier than air.

In open plants, it is generally assumed that flammable gases, which are lighter than air, escape upwards and spread out in an uncontrolled manner.

However, the situation is different if the system in which gas leakage can occur is located in an enclosure with few external openings. In this case, the light gas can not spread uncontrollably at a leak.

The formation of an explosive gas mixture is inventively prevented by spraying non-combustible gases or liquids at least one outer opening. Thus, a gas jet curtain is generated, which dilutes the clouds of flammable gases located in the enclosure, or in the direction of at least one outer opening carries and thus ejects, or discharges.

The term "at an outer opening" is therefore to be understood functionally such that the jet curtain is arranged spatially at or near the outer opening, that the clouds of combustible gases diluted and preferably carried in the direction of at least one outer opening and so discharged from the enclosure , or be discharged. Frequently, the jet curtain covers the at least one outer opening completely or at least partially.

The enclosure often contains devices for the production, processing or storage of combustible gases. Corresponding devices are for example reactors, tanks or compressed gas cylinders, heat exchangers, columns or entire plants or lines.

The combustible gas may be selected from any combustible gases whose density does not exceed the density of air (at identical temperature and pressure). Flammable gases used in accordance with the invention thus do not sink to the bottom of the enclosure in a corresponding enclosure.

Examples of suitable combustible gases are acetylene, hydrogen, ammonia, carbon monoxide, coking gas, landfill gas, town gas, biogas, synthesis gas, methane, or natural gas or hot, combustible gases.

A liquid or gas jet curtain may be produced by any suitable nonflammable gas or liquid, wherein the liquid jet curtain is not part of the invention. For example, it may be a liquid jet curtain of water. It is preferably a gas jet curtain, which is formed by water vapor, air, nitrogen or mixtures thereof, preferably by steam. The steam can be present at the pressure levels provided in the plant or investment environment. Typically, in chemical plants there are pressure stages for water vapor of about 1.5 bar, 4 bar or 16 bar. Preference is given to 2 to 6 bar.

The removal from the housing preferably takes place in such a way that there is no ignitable mixture of the combustible gas outside the housing. This means that the effluent liquid or gas amount of the non-combustible liquid, or the non-combustible gas is controlled so that a sufficient mixing with the leaking from a combustible flammable gas and additionally with sucked air is achieved, so that not one more combustible or ignitable gas mixture results.

The enclosures receiving the devices for producing, processing or storing the combustible gases have one or more external openings. Preferably, the surface of the outer openings is at most 40%, more preferably at most 20%, in particular at most 10%, of the entire outer surfaces of the enclosure located above the ground. The area of the outer openings may preferably amount to at least 0.5%, particularly preferably at least 1%, in particular at least 2%, of the entire outer surfaces of the enclosure located above the ground.

Often the enclosure is arranged on the ground and has vertical outer walls. In addition, it is closed at the top by a roof. At least one outer opening is arranged directly adjacent to the roof in the roof or in the outer walls. The term "immediate" denotes a position which is arranged in the upper quarter, preferably upper fifth, in particular upper tenth of the outer walls. Particularly preferably, this outer opening is located directly on the upper edge of the outer walls and thus directly adjacent to the roof. Other external openings may be provided at other locations of the enclosure, z. B. to allow the influx of outside air into the enclosure.

According to the invention, one or more outer openings can be present in the housings. Preferably, 1 to 5, particularly preferably 1 to 3, in particular 1 or 2 outer openings are present.

The formation of the gas jet curtain follows such that the clouds of combustible gases in the discharge at least 80%, preferably at least 90%, in particular at least 95%, especially pass completely through the gas jet curtain, or must pass. This ensures that the jet curtain provides sufficient dilution and adequate transport of the combustible gas cloud. Depending on the design of the housing, or the outer opening or outer openings may be provided for each outer opening a beam curtain. It is also possible that a jet curtain is not provided for each outer opening and the remaining outer openings serve only for the inflow of air which, diluted with the combustible gas, exits through the jet curtain and through another outer opening.

Typically, the enclosure will have vertical outer walls and a flat or pitched roof that rests on the outer walls. The outer openings can be one have any outline. For example, they may have an angular or approximately angular outline, with one edge of the outer opening extending horizontally. The gas jet curtain can be formed, for example, at an angle to the roof or the outer wall of, for example, 45 ° ± 10 °. This means that the gas jet curtain does not have to impinge perpendicular to the outer opening or be parallel to it, but can impinge at an oblique angle. For example, the gas jet curtain can also be arranged on an outer wall offset inwards such that it is directed at an angle of approximately 45 ° to the roof and can additionally suck in and entrain ambient air from below.

A corresponding embodiment is in the attached FIG. 1 shown schematically. The FIG. 1 shows a cross-sectional view of outer wall (Wa) and roof (Da) in the region of the jet curtain (St), which is produced by a steam line (Dam), which is provided with holes. The outer wall (Wa), at the upper edge of the jet curtain (St) is formed, is offset from the roof edge inwards, resulting in an outer opening. By forming the jet curtain (St) at an angle of about 40 ° with respect to the horizontal obliquely above from the interior of the housing combustible gas (light gas (Le)) is entrained, escaping from apparatuses with leakage (Ap), and from the outside environment the enclosure air (Lu) entrained, which leads to the dilution of the combustible gas.

According to the invention, all outer openings can be covered by gas jet curtains, so that the combustible gas must in each case pass through a gas jet curtain. Preferably, at least near the roof outer openings are covered by appropriate beam curtains.

The gas jet curtain is preferably produced by the exit of a gas or a liquid from a tube which has holes along its longitudinal axis perpendicular to the longitudinal axis, which may lie on the pipe surface on a common connecting line. For example, a tube with an inner diameter of about 8 cm (DN 80) can be used, which has approximately 5 mm diameter holes, which are provided at a distance of about 7 cm. An approximately 4 m long DN 80 pipe section can thus have approximately 57 holes with a diameter of 5 mm. It can be operated with a pressure of 4 bar steam.

The steam curtain may have a length in the range of preferably 0.5 to 6 m, depending on the size of the outer opening to be covered.

The gas jet curtain is preferably triggered sensor-controlled when a leakage of the combustible gas is detected. A corresponding detection and control device is known from fans that were previously provided for the discharge of appropriate combustible gases in an emergency.

The method of the invention can replace a conventional emergency chamber vent by fans.

Preferably, in the method according to the invention, the enclosures are not completely open at the top, since otherwise the gas can escape freely upwards. Preferably, the enclosure has only the smaller openings described above and thus prevents the free propagation of the flammable gas so that it is diluted by the gas or liquid jet curtain.

A corresponding steam jet curtain was provided in an enclosure surrounding a shell and tube reactor with acetylene dissolved in liquid acetone. Thus, leakage of a combustible acetylene gas cloud can be reliably prevented.

Claims (14)

1. The use of a gas-jet curtain generated by spraying non-flammable gases or liquids for diluting and/or ejecting clouds of flammable gases, the density of which does not exceed the density of air, from containments that have one or more outer openings.
2. A method for diluting and/or ejecting clouds of flammable gases, the density of which does not exceed the density of air, from containments that have one or more outer openings, wherein, by spraying non-flammable gases or liquids at at least one outer opening, a gas-jet curtain is generated that dilutes the clouds of flammable gases situated in the containment or bears them in the direction of the at least one outer opening and thus ejects them.
3. The method according to claim 2, wherein the containment comprises devices for production, processing or storage of the flammable gases.
4. The method according to claim 2 or 3, wherein the flammable gas is selected from acetylene, hydrogen, ammonia, carbon monoxide, coke oven gas, landfill gas, town gas, biogas, synthesis gas, methane, natural gas or hot flammable gases.
5. The method according to any one of claims 2 to 4, wherein the gas-jet curtain is formed by steam, air, nitrogen or mixtures thereof.
6. The method according to any one of claims 2 to 5, wherein the ejection from the containment proceeds in such a manner that no ignitable mixture of the flammable gas is present outside the containment.
7. The method according to any one of claims 2 to 6, wherein at least 80% of the clouds of flammable gases, during the ejection, pass through the gas-jet curtain.
8. The method according to any one of claims 2 to 7, wherein the containment is arranged on the ground, has substantially upright outer walls and is closed at the top by a roof, wherein the at least one outer opening is arranged in the roof or in the upper quarter of the outer walls.
9. The method according to claim 8, wherein the gas-jet curtain is at an angle of 45° ± 10° to the roof or outer wall.
10. The method according to any one of claims 1 to 9, wherein the area of the outer opening makes up a maximum of 40% of the total outer areas of the containment.
11. The method according to any one of claims 1 to 10, wherein the gas-jet curtain is generated by exit of a gas or a liquid from a tube which, along its longitudinal axis, has, perpendicularly to the longitudinal axis, boreholes that can lie on a common connection line on the tube surface.
12. The method according to claim 11, wherein the steam curtain has a length in the range from 0.5 to 6 m.
13. The method according to claim 11 or 12, wherein the at least one outer opening has a horizontal lower edge and the tube extends in parallel to this lower edge.
14. A containment having one or more outer openings having appliances for generating a gas-jet curtain arranged at at least one outer opening, wherein the gas-jet curtain dilutes the clouds of flammable gases situated in the containment or bears them in the direction of the at least one outer opening and thus ejects them, wherein the containment has upright outer walls and is closed at the top by a roof and at least one outer opening is arranged in the upper quarter of the outer walls.

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