GB2090736A - A method and apparatus for reducing the risk of spontaneous combustion in a gas mixture - Google Patents
A method and apparatus for reducing the risk of spontaneous combustion in a gas mixture Download PDFInfo
- Publication number
- GB2090736A GB2090736A GB8100712A GB8100712A GB2090736A GB 2090736 A GB2090736 A GB 2090736A GB 8100712 A GB8100712 A GB 8100712A GB 8100712 A GB8100712 A GB 8100712A GB 2090736 A GB2090736 A GB 2090736A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gas
- oxygen
- gas mixture
- particulate matter
- inert gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000000034 method Methods 0.000 title claims abstract description 39
- 239000000203 mixture Substances 0.000 title claims abstract description 34
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 16
- 230000002269 spontaneous effect Effects 0.000 title claims abstract description 16
- 239000007789 gas Substances 0.000 claims abstract description 94
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 41
- 239000001301 oxygen Substances 0.000 claims abstract description 41
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 41
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 38
- 239000013618 particulate matter Substances 0.000 claims abstract description 24
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 19
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 19
- 239000000725 suspension Substances 0.000 claims abstract description 12
- 239000011261 inert gas Substances 0.000 claims description 28
- 239000003415 peat Substances 0.000 claims description 27
- 239000002245 particle Substances 0.000 claims description 25
- 238000012544 monitoring process Methods 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- -1 for example Substances 0.000 abstract description 3
- 238000001035 drying Methods 0.000 description 10
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 208000027418 Wounds and injury Diseases 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 208000014674 injury Diseases 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62C—FIRE-FIGHTING
- A62C99/00—Subject matter not provided for in other groups of this subclass
- A62C99/0009—Methods of extinguishing or preventing the spread of fire by cooling down or suffocating the flames
- A62C99/0018—Methods of extinguishing or preventing the spread of fire by cooling down or suffocating the flames using gases or vapours that do not support combustion, e.g. steam, carbon dioxide
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62C—FIRE-FIGHTING
- A62C3/00—Fire prevention, containment or extinguishing specially adapted for particular objects or places
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62C—FIRE-FIGHTING
- A62C3/00—Fire prevention, containment or extinguishing specially adapted for particular objects or places
- A62C3/04—Fire prevention, containment or extinguishing specially adapted for particular objects or places for dust or loosely-baled or loosely-piled materials, e.g. in silos, in chimneys
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Abstract
The invention relates to a method and apparatus for reducing the risk of spontaneous combustion in a gas mixture containing at least oxygen and particulate matter in suspension. The method and apparatus overcomes the problem of having to increase the temperature of the gas mixture in order to reduce the level of oxygen when the oxygen level exceeds a certain critical level at which spontaneous combustion may occur. Essentially, the method includes the step of introducing an inert type gas, for example, carbon dioxide into the gas mixture when the oxygen level exceeds the critical level. The apparatus is illustrated connected to a Pico drier (1) having six spiral tube driers (2 to 6). The apparatus comprises jets (31) which introduce the carbon dioxide into the conveying gas stream through the driers (4 to 6). <IMAGE>
Description
SPECIFICATION
A method and apparatus for reducing the risk of spontaneous combustion in a gas mixture
The present invention relates to a method and apparatus for reducing the risk of spontaneous combustion in a gas mixture containing at least oxygen and particulate matter in suspension, for example, peat particles, wood chips, grain and the like materials.
In case mixtures which contain at least oxygen and particulate matter in suspension there is always a risk of spontaneous combustion of the particulate matter when the oxygen concentration rises above a certain percentage by weight or volume of the gas mixture. This is a particular problem in the case of a conveying gas stream conveying peat particles through a drier prior to briquetting.
In this case, the peat particles having been screened, are blown, suspended in a stream of air and/or water vapour, through a series of spiral tube driers. It has been found that when the oxygen concentration of air and/or water vapour reaches 12 percent by weight, spontaneous combustion can occur. Needless to say, spontaneous combustion in such driers causes serious damage to the driers and indeed may lead to serious injury of personnel.
Similarily, where peat particles are stored in a silo there is also the risk of spontaneous combustion.
In known peat drying plants, to keep the oxygen concentration below 12 percent by weight it is necessary to keep the temperature of the conveying gas stream at or above 86"C. This leads to excessive usage of energy and also considerably reduces the carrying capacity of the gas stream.
There is therefore a need for a method and apparatus for, reducing the risk of spontaneous combustion in a gas mixture containing particulate matter. There is also the need for a method and apparatus for reducing the risk of spontaneous combustion in conveying gas stream, while at the same time maintaining the carrying capacity of the gas at a reasonable level.
The present invention is directed towards providing such a method and apparatus.
According to the invention there is provided a method for reducing the risk of spontaneous combustion in a gas mixture containing at least oxygen and particulate matter in suspension the method comprising the step of introducing an inert type gas into the gas mixture.
In one embodiment of the invention the gas mixture is a conveying gas stream conveying the particulate matter in suspension.
in another embodiment of the invention the inert gas is introduced at a rate to maintain the concentration of oxygen in the gas mixture at or below 20% by weight of the gas excluding the particulate matter.
Preferably the inert gas is introduced at a rate to maintain the concentration of oxygen in the gas mixture at 10.9% by weight of the gas excluding the particulate matter.
Advantageously, the method comprises the additional step of monitoring the concentration of oxygen in the gas mixture by monitoring apparatus, and the rate at which the inert gas is introduced is controlled by control apparatus connected to the monitoring apparatus.
In one embodiment of the invention the inert gas is continuously introduced into the gas mixture.
Alternatively, the inert gas is intermittently introduced.
Preferably, the inert gas is carbon dioxide.
in one embodiment of the invention the gas mixture comprises compressed air and water vapour, and the particulate matter is peat particles, and the conveying gas stream conveys the peat particles thrugh a spiral tube drier, and inert gas is introduced into the conveying gas stream in the drier.
In another embodiment of the invention the inert gas is introduced before the conveying gas stream enters the drier.
Additionally, the invention provides apparatus for carrying out the method, the apparatus comprising at least on jet communicating with the gas mixture for introducing the inert gas, the jet being connected to an inert gas source.
The invention will be more clearly understood from the following description of a preferred embodiment thereof given by way of example only with reference to the accompanying drawings, in which:
Figure 1 is a diagrammatic representation of drying apparatus for peat particles incorporating apparatus according to the invention,
Figure 2 is a sectional view of portion of the drying apparatus on the line ll-ll of Figure 1, and
Figure 3 is a graph showing the relationship between various parameters of a drying process.
Referring to Figures 1 and 2, there is provided drying apparatus indicated generally by the reference numeral 1 for drying particulate matter, in this embodiment of the invention peat particles. The apparatus 1 is part of a Peco drying assembly used for drying peat particles prior to briquetting. The apparatus includes two first stage driers 2 and 3 and three second stage driers 4 to 6. The driers 2 to 6 are connected in series by ducts 7 which connect an inlet 8 of one drier to an outlet 9 of its preceding drier to convey the peat particles from one drier to the next.
Peat particles are delivered to the inlet 8 of the drier 2 with a moisture content of approximately 60 percent from a screen (not shown) through a duct 10.
The peat particles, dried, with a moisture content of approximately 10 percent are delivered from the outlet 9 of the drier 6 to a peat briquetting plant (not shown) through a duct 11. The driers 2 to 6 are vertical spiral tube driers, having a body shell 18 and spiral tubes 19 through which peat particles are conveyed in suspension in a conveying gas stream, which is described below. The spiral tubes 19 of the first stage driers 2 and 3 are jacketted with water at 65"C. The spiral tubes 19 of the second stage driers 4 to 6 are jacketted with desuperheated back pressure steam at 0.2 to 0.3 atmospheres and 138"C.
The conveying gas stream is provided by a mixture of air and water vapour. In the case of the first stage driers, the air stream is delivered to the inlets 8 of the first stage driers 2 and 3 by air blower fans 12 and 13 through ducts 14 and in the case of the second stage driers 4 to 6, the air stream is delivered into the inlet 8 of the drier 6 through an air blower fan 15. In all the driers 2 to 6, as the peat particles dry water vapour is evaporated into the air stream from the drying peat particles.
Cyclones 22 to 26 are mounted in the outlets 9 of each drier 2 to 6 respectively to separate out dust and water vapour and allow the peat particles to fall under gravity through the ducts 7 to the inlet 8 of the next drier. Vents 28 of the cyclones 22 and 23 are vented to atmosphere, while the vents 28 of the cyclones 25 and 26 are connected to the inlets 8 of the preceding driers 4 and 5 respectively through ducts 29 to provide the stream of air and evaporated water vapour to convey the peat particles through the driers 4 and 5. The vent 28 of the cyclone 24 is connected to a heat exchanger (not shown) through a duct 35.
Air locks 30 are provided in the ducts 7 at the inlet 8 of each of the driers 3 to 6 and in the duct 10 at the inlet 8 of the drier 2. Air locks 30 are also provided at the outlet 9 of the drier 6.
Apparatus according to the invention for introducing an inert gas into the conveying gas stream comprises jets 31. One jet 31 is mounted in the duct 16 just before the blower fan 15 and another jet 31 is mounted in the top of the drier 5 to inject the inert gas into the conveying gas stream in the spiral tube 19 of the drierS. In this embodiment of the invention the inert gas is carbon dioxide. The jets 31 are connected by pipes 32 to a carbon dioxide source (not shown).
Monitoring apparatus provided by oxygen level sensors shown diagrammatically by dots 36 in
Figure 1 are provided in the spiral tube of the driers 4 5 and 6 to monitor the level of oxygen in the conveying gas stream. The sensors 36 are connected by cables 37 to suitable control apparatus (not shown) which controls the delivery of carbon dioxide through the pipe 32 on receiving a signal from the monitoring apparatus thatthe level of oxygen in the conveying gas stream has increased above a predetermined level, in this embodiment of the invention 11% by weight of the gas stream excluding the particulate matter.On receiving the signal from the monitoring apparatus, the control apparatus continues to allow carbon dioxide to be injected through the jets 31 into the conveying gas stream until the level of oxygen in the conveying gas stream has dropped below 10.9% by weight, at which stage the control apparatus isolates the jets 31 from the carbon dioxide source (not shown).
In use, peat particles are conveyed in series through the first stage driers 2 and 3 in suspensions in the conveying gas stream generated by the fans 12 and 13. The peat particles are conveyed through the second stage driers 4to 6 also in suspension in the conveying gas stream generated by the fan 15.
The oxygen level sensors 36 continuously monitor the level of oxygen in the conveying gas stream.
Once the level of oxygen exeeds 11% by weight of the gas stream excluding the peat particles, the monitoring apparatus (not shown) activates the control apparatus (also not shown). The control apparatus connects the jets 31 to the carbon dioxide source (not shown) and the carbon dioxide is delivered into the gas stream through the jets 31.
Once the level of oxygen in the gas stream is reduced below 10.9% by weight, excluding the peat particles, the monitoring apparatus deactivates the control apparatus, which in turn isolates the jets 31 from the carbon dioxide source, until the oxygen concentration rises above 11% again.
The advantage of using this method to reduce the oxygen level in the conveying gas stream is that it does not substantially effect the carrying capacity of the gas stream. Furthermore, it enables the oxygen concentration to be reduced and maintained at a safe level without increasing the temperature of the gas stream.
To understand this, it is necessary to consider the graphs in Figure 3. Graph 1 shows the relationship between the percentage by weight of oxygen in the conveying gas stream and the temperature of the conveying gas stream. Graph 2 shows the relationship between the density of the conveying gas stream and the temperature of the gas stream.
Graph 3 shows the relationship between the weight ratio of water vapour to air in the gas stream and the temperature of the gas stream. In a conveying gas stream, conveying peat particles, it has been found that when the oxygen level exceeds 12 percent by weight of the gas stream, spontaneous combustion is likely to occur. It can be seen from the graph to maintain the level of oxygen at 12 percent the temperature of the gas stream must not drop below 86"C. At which temperature, the density of the mixture is approximately 0.77 kilograms per cubic metre. It will be appreciated that the carrying capacity of the gas stream is directly proportional to the density of the gas stream.Therefore, if it is desired to operate the drying process with the oxygen level at 11% by weight of the gas stream, it is necessary to increase the temperature of the stream to 880C. At this temperature, the density of the gas stream is reduced to approximately 0.745 kilograms per cubic metre. It will be appreciated that this lead to a considerable reduction in the carrying capacity of the gas stream.
However, the advantage of the present invention is that by introducing carbon dioxide into the gas stream, for example, when the oxygen level is 12 percent, the oxygen level can be readily easily reduced to below 10.9% without any change in temperature of the gas stream. Accordingly, it will be appreciated that the carrying capacity of the gas steam is substantially uneffected. For example, if the carbon dioxide is introduced when the oxygen level is 12 percent, the density will remain at approximately at 0.77 kilograms per cubic metre thereby leaving the carrying capacity of the gas stream substantially unaltered.
Needless to say, it will be appreciated that although in above example the carbon dioxide has been introduced intermittently into the conveying gas stream it could if desired be introduced continuously.
It is envisaged that the method and apparatus for reducing the risk of spontaneous combustion in a gas mixture could be used where particulate matter is stored in silos and the like. For example, it is envisaged that when the peat particles have been delivered from the last of the second stage driers into a storage hopper, a further carbon dioxide jet could be provided into the silo to maintain the level of oxygen in the silo at a safe level to avoid spontaneous combustion in the silo.
Furthermore, although the method and apparatus has been described for use in a conveying gas stream conveying peat particles it could be used in connection with any type of particulate matter either being conveyed or stored where the particulate matter is in suspension..
Furthermore, it will be appreciated that although the method and apparatus has been described as injecting carbon dioxide into certain driers, the carbon dioxide could have been introduced into any of the driers or indeed to all of the driers. Additionally, it is envisaged that the inert gas could be introduced into the air stream before it enters the first driers.
Indeed it will be appreciated that other suitable inert gases could be used besides carbon dioxide, for example, nitrogen, helium or the like gases.
Although, in the embodiment of the invention described it was desired to reduce and maintain the oxygen concentration of the stream below 11 percent, it will be appreciated that the concentration of oxygen in the conveying gas stream could be maintained at any desired level. It will be appreciated that the desired level will vary depending on the particulate matter in suspension and the process conditions.
Claims (21)
1. A method for reducing the risk of spontaneous combustion in a gas mixture containing at least oxygen and particulate matter in suspension, the method comprising the step of introducing an inert type gas into the gas mixture.
2. A method as claimed in claim 1 in which the gas mixture is a conveying gas stream conveying the particulate matter in suspension.
3. A method as claimed in claims 1 or 2 in which the inert gas is introduced at a rate to maintain the concentration of oxygen in the gas mixture at or below 20% by weight of the gas excluding the particulate matter.
4. A method as claimed in claim 3 in which the inert gas is introduced at a rate to maintain the concentration of oxygen in the gas mixture at or below 15% by weight of the gas excluding the particulate matter.
5. A method as claimed in claim 4 in which the inert gas in introduced at a rate to maintain the concentration of oxygen in the gas mixture at or below 11% by weight of the gas excluding the particulate matter.
6. A method as claimed in claim 5 in which the inert gas is introduced at a rate to maintain the concentration of oxygen in the gas mixture at 10.9% by weight of the gas excluding the particulate matter.
7. A method as claimed in any of the preceding claims in which the method comprises the additional step of monitoring the concentration of oxygen in the gas mixture by monitoring apparatus, and the rate at which the inert gas is introduced is controlled by control apparatus connected to the monitoring apparatus.
8. A method as claimed in any preceding claim in which the inert gas is continuously introduced into the gas mixture.
9. A method as claimed in any of claims 1 to 7 in which the inert gas is intermittently introduced.
10. A method as claimed in any of the preceding claims in which the inert gas is carbon dioxide.
11. A method as claimed in any of the preceding claims in which the gas mixture comprises compressed air.
12. A method as claimed in any of the preceding claims in which the gas mixture comprises water vapour.
13. A method as claimed in any of the preceding claims in which the particulate matter is peat particles.
14. A method as claimed in claim 2 of any of claims 3 to 13 in which the conveying gas stream conveys the particulate matter through a drier.
15. A method as claimed in claim 14 in which the conveying gas stream passes through the spiral tube of a vertical spiral tube drier.
16. A method as claimed in claim 14 or 15 in which the inert gas is introduced into the conveying gas stream in the drier.
17. A method as claimed in any of claims 14 to 16 in which the inert gas in introduced before the conveying gas stream enters the drier.
18. A method substantially as described herein with reference to the accompanying drawings.
19. Apparatus for carrying outthe method as claimed in any of the preceding claims, the apparatus comprising at least one jet communicating with the gas mixture for introducing the inert gas, the jet being connected to an inert gas source.
20. An apparatus as claimed in claim 19 in which a sensor projects into the gas mixture to sense the concentration of oxygen in the stream, the sensor being connected to control apparatus to control the rate of introduction of the inert gas through the jet.
21. Apparatus substantially as described herein with reference to and as illustrated in the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8100712A GB2090736A (en) | 1981-01-10 | 1981-01-10 | A method and apparatus for reducing the risk of spontaneous combustion in a gas mixture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8100712A GB2090736A (en) | 1981-01-10 | 1981-01-10 | A method and apparatus for reducing the risk of spontaneous combustion in a gas mixture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2090736A true GB2090736A (en) | 1982-07-21 |
Family
ID=10518907
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8100712A Withdrawn GB2090736A (en) | 1981-01-10 | 1981-01-10 | A method and apparatus for reducing the risk of spontaneous combustion in a gas mixture |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2090736A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996001477A1 (en) * | 1994-07-04 | 1996-01-18 | Siemens Aktiengesellschaft | Inert gas generation process and device |
| WO1999047210A1 (en) * | 1998-03-18 | 1999-09-23 | Wagner Alarm- Und Sicherungssysteme Gmbh | Inerting method for preventing and extinguishing fires in enclosed spaces |
| EP1199087A3 (en) * | 2000-10-18 | 2002-06-05 | Airbus Deutschland GmbH | Method for extinguishing a fire inside an enclosed space |
-
1981
- 1981-01-10 GB GB8100712A patent/GB2090736A/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996001477A1 (en) * | 1994-07-04 | 1996-01-18 | Siemens Aktiengesellschaft | Inert gas generation process and device |
| US5764716A (en) * | 1994-07-04 | 1998-06-09 | Siemens Aktiengesellschaft | Process and apparatus for generating an inerting gas |
| WO1999047210A1 (en) * | 1998-03-18 | 1999-09-23 | Wagner Alarm- Und Sicherungssysteme Gmbh | Inerting method for preventing and extinguishing fires in enclosed spaces |
| CZ297177B6 (en) * | 1998-03-18 | 2006-09-13 | Wagner Alarm- Und Sicherungssysteme Gmbh | Inerting method for preventing risk and extinguishing fires in enclosed spaces |
| EP1199087A3 (en) * | 2000-10-18 | 2002-06-05 | Airbus Deutschland GmbH | Method for extinguishing a fire inside an enclosed space |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |