Classifications

• • 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
  • A62C3/06—Fire prevention, containment or extinguishing specially adapted for particular objects or places of highly inflammable material, e.g. light metals, petroleum products
• • 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
• • 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
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D16/00—Control of fluid pressure
  • G05D16/20—Control of fluid pressure characterised by the use of electric means
  • G05D16/2093—Control of fluid pressure characterised by the use of electric means with combination of electric and non-electric auxiliary power
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D16/00—Control of fluid pressure
  • G05D16/20—Control of fluid pressure characterised by the use of electric means
  • G05D16/2093—Control of fluid pressure characterised by the use of electric means with combination of electric and non-electric auxiliary power
  • G05D16/2095—Control of fluid pressure characterised by the use of electric means with combination of electric and non-electric auxiliary power using membranes within the main valve
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D16/00—Control of fluid pressure
  • G05D16/20—Control of fluid pressure characterised by the use of electric means
  • G05D16/2093—Control of fluid pressure characterised by the use of electric means with combination of electric and non-electric auxiliary power
  • G05D16/2097—Control of fluid pressure characterised by the use of electric means with combination of electric and non-electric auxiliary power using pistons within the main valve

Definitions

• the present invention relates to an apparatus and method for automatically controlling the flow of gas in a system.
• the invention relates to controlling the flow of inert gas to a silo in which biomass fuel is stored prior to combustion and thereby preventing fires and/or explosions in the silo, via sudden dust cloud formation and associated static risk.
• biomass comprises plant matter, which may be in the form of wood, a fluff material or pellets formed from material which has been shredded and compacted.
• the biomass material is stored in large silos to keep the material dry and reduce loss of the material prior to being conveyed for use in boilers. Such silos can range from hundreds to thousands of cubic meters in volume.
• Biomass dust may be generated from the biomass during storage and handling. The dust is drawn off in an air stream which is filtered to remove the dust.
• Fires may occur in both biomass storage silos and dust storage silos, and the factors which cause fires in both cases are broadly the same. Fires in biomass storage silos can come about as a result of bacterial and fungal activity which generate heat and produce methane, carbon monoxide and carbon dioxide. Heat accumulates to over 50°C leading to thermal oxidation of the biomass. Due to the thermal insulating properties of the biomass, the rate of heat generation may exceed the rate of heat loss, leading to a temperature rise, and may eventually lead to ignition. Fires may also be imported into silos, for example through hot product, or from hot bearings within the conveying system.
• inert gas can be injected into the headspace to minimise the risk of self heating, to inert the headspace in the event of a surface fire or to provide an inert atmosphere in the event of a high risk of imminent explosion.
• the top may be about 40 to 60 metres above ground level. Accordingly, to minimise the use of materials, the most efficient way of piping an inert gas into the headspace of a large silo is to pipe the gas in a relatively small bore pipe at a relatively high pressure (approximately 5-10 barg) and at a velocity of approximately 10-30 m/s, and then pass the gas through an orifice on a nozzle into the silo. As the gas passes through the nozzle, a critical pressure drop takes place, reducing the gas to effectively atmospheric pressure, thereby causing the velocity of the gas to increase further. A problem with high velocity gas is that it can disturb any dust present in the silo, thereby creating a dust cloud. A problem resulting from the dust cloud is that it can cause the nozzle to become blocked, and sudden dust cloud movement can lead to static electricity which can create sparks, which increase the risk of fires and/or explosions in the silo.
• the inert gas is often introduced slowly at first. This slowly increases the inert atmosphere in the headspace and the velocity of the inert gas can gradually be increased as the risk of static from dusts around the nozzle is reduced due to the reduced oxygen content.
• a control valve either on flow or pressure
• a programmable logic controller may be used to slowly increase the flow of gas in a system from zero, to the desired design flow. Both of these solutions have associated cost implications and are prone to errors occurring.
• actuators for on/off valves may be tweaked to delay the opening of the valve through spring adjustment or a throttling valve. However, the delays in opening are not sufficiently long from being in the closed position to being in the open position.
• an apparatus for controlling the flow of gas into a container comprising: a primary gas conduit configured to feed inert gas from an inert gas source at a pressure greater than atmospheric pressure to a container configured to receive flammable material;
• a first gas flow regulating means operably connected to the primary gas conduit, and configured to regulate the flow of gas flowing therethrough;
• a secondary gas conduit in fluid communication with the primary gas conduit, and disposed upstream of the first gas flow regulating means;
• a first valve operably connected to the primary or secondary gas conduit, and disposed upstream of the gas storage means
• the container is a storage silo.
• the flammable material preferably comprises a biomass substance, for example plant material.
• the flammable material may be in the form of pellets and/ or dust.
• the flammable material may be a fuel source.
• the inert gas source may comprise a liquid gas store, a Pressure Swing Adsorption (PSA) unit, a membrane gas generation plant, or any other appropriate inert gas source.
• the inert gas source comprises a liquid gas store.
• the inert gas comprises carbon dioxide, nitrogen gas and/or argon.
• the apparatus may comprise a restriction orifice operably connected to the primary gas conduit, and disposed downstream of the first flow regulating means, wherein the orifice is configured to reduce the pressure of gas flowing therethrough.
• the restriction orifice may have a diameter which is at least 30% less than the diameter of the primary gas conduit upstream thereof.
• the restriction orifice has a diameter which is at least 40% less, 50% less, 60% less, 70% less, 80% less or 90% less than the diameter of the conduit upstream thereof.
• the apparatus comprises control means configured to switch the apparatus between the standby mode and the activated mode.
• the control means is configured to send a signal (which is preferably a digital signal) to the first valve to switch the apparatus between standby and activated modes.
• the first valve may be operably connected to the secondary gas conduit, and is preferably disposed upstream of the gas storage means.
• the first valve can be any type of valve known in the art.
• the first valve comprises a solenoid valve, and is arranged to receive the signal from the control means.
• the first gas flow regulating means may comprise a gas regulator, and preferably a forward pressure regulator comprising a loading mechanism, a sensing element and a control element.
• the forward pressure regulator comprises a dome-loaded regulator.
• the loading mechanism is configured to determine the gas regulator's outlet pressure, i.e. the pressure downstream of the dome loaded regulator.
• the sensing element is adapted to sense changes in the outlet pressure and allows the regulator to react to these changes.
• the control element is configured to reduce the inlet pressure to the desired outlet pressure and maintains it by increasing or decreasing an orifice area as the control element moves away or towards a regulator seat.
• the first gas flow regulating means comprises a dome loaded regulator, wherein the loading mechanism comprises a dome in fluid
• the sensing element may comprise a diagram sensing element, a piston sensing element or a bellows sensing element.
• the control element may comprise an unbalanced control element or a balanced control element.
• the second flow regulating means has a flow coefficient (Cv) of about 0.001.
• the second flow regulating means may comprise a restriction orifice.
• the second flow regulating means comprises a metering needle valve.
• a metering needle valve allows the flow coefficient (Cv) to be varied.
• the apparatus may comprise a second vent line operably connected to the secondary gas conduit and/or storage means, and disposed downstream of the first valve.
• the second vent line is preferably disposed downstream of the second flow regulating means.
• the apparatus preferably comprises a vent valve operably connected to the second vent line.
• the vent valve may comprise a pressure safety valve configured to prevent the pressure in the gas storage means from exceeding a predetermined pressure.
• the vent valve may comprise a solenoid valve wherein when the apparatus is activated, the storage means is not in fluid communication with the second vent line, and when the apparatus is in standby mode, the storage means is in fluid communication with the second vent line.
• the first valve is operably connected to the secondary gas conduit, and disposed upstream of the gas storage means, and the apparatus comprises a second valve operably connected to the primary gas conduit, and disposed upstream of the first flow regulating means.
• the first gas flow regulating means is not in fluid communication with the inert gas source, and when the apparatus is in activated mode, the first gas flow regulating means is in fluid communication with the inert gas source.
• the second valve may be disposed upstream of where the secondary gas conduit is in fluid communication with the main gas conduit.
• the second valve may be disposed downstream of where the secondary gas conduit is in fluid communication with the main gas conduit.
• the second valve comprises an actuated isolation valve system.
• the further valve may comprise a further solenoid valve.
• the control means is configured to send a digital signal to the further solenoid valve to switch the apparatus from standby mode to activated mode and from activated mode to standby mode.
• the apparatus comprises a further flow regulating means operably connected to the secondary gas conduit, and configured to limit the pressure of the inert gas downstream thereof.
• the further flow regulating means comprises a pilot regulator.
• the further flow regulating means is disposed upstream of the gas storage means. It will be appreciated that the apparatus of the invention has several important uses.
• the gas is preferably inert, and the container is preferably a storage silo.
• the apparatus is used to control the flow of inert gas into the container in order to:- (i) inert the atmosphere in a container's headspace to minimise the risk of its contents from self-heating,
• a method of controlling the flow of gas into a container from an inert gas source comprising:
• the flow rate of the inert gas 2 along the main gas conduit 6, passed the dome loaded regulator 8 and into the silo headspace 3 will remain at 4449.71 sm3/hr until the apparatus 4 is switched to standby mode.
• the rate at which the pressure in the receiver 20 (and therefore the flow into the silo) increases can be varied by modifying the flow which the metering needle valve 19 allows along the secondary line 10 and/or by modifying the size of the receiver 20.
• the inert gas 2 stored in the receiver 20 will start to flow out of the first vent line 18 decreasing the pressure of the inert gas 2 in the receiver 20. Due to the presence of the metering needle valve 19, the rate at which the receiver 20 is able to vent is restricted. Accordingly, the pressure of the inert gas 2 in the receiver 20 and the flow rate of the inert gas 2 into the silo headspace 3 will both decrease gradually over time, as shown in Table 3.
• the second solenoid valve 30' is set to allow a flow of gas through the second port 36' and the third port 38', and along the third vent line 40'. Accordingly, gas is unable to flow along the further gas line 32'.
• the actuated valve 42' does not allow gas flow along the main gas conduit 6'.
• a digital signal (e.g. a 24V direct current signal) is sent from the control system 26' to the first solenoid valve 14', which switches the ports of the first solenoid valve 14', as discussed in Example 1.
• the control system 26' sends a digital signal to the third solenoid valve 30', which causes the ports of the third solenoid valve 30' to switch, so that gas flows between the first port 34' and second port 36' and along the further gas line 32'.
• the pressure caused by this gas flow causes the actuated valve 42' to allow flow along the main gas conduit 6'. This will not have any noticeable effect when the apparatus 4' is activated.
• the apparatus 4' is switched from on to standby mode. Again, this can be carried out by sending a digital signal from the control system 26' to both the first solenoid valve 14' and the third solenoid valve 30'. This switches the ports of the first solenoid valve 14' as discussed in Example 1, and causes the ports 34', 36' and 38' of the third solenoid valve 30' to switch to once again allow flow between the second port 36' and the third port 38'. This immediately stops the flow of the inert gas 4 through the actuated valve 42'. Accordingly, unlike the apparatus 4 discussed in Example 1, when apparatus 4' is switched to standby mode, the flow of the inert gas 4 into the silo headspace 3 stops almost immediately.
• FIG 4 A fourth embodiment of the apparatus is shown in Figure 4, which includes all of the elements which were present in the apparatus 4 shown in Figure 1. Unlike the apparatus 4' shown in Figure 3, the apparatus 4" shown in Figure 4 does not include an actuated isolation valve system 28'. However, it will be understood that a further embodiment could include this feature.
• pilot regulator 44" would not limit the rate at which the receiver 20" fills with gas. Accordingly, the preferred embodiment is when the pilot regulator 44" is positioned upstream of the receiver 20" as shown in Figure 4.
• Each embodiment of the apparatus 4, 4', 4" shown in the Figures may be retrofitted to existing silos, or included in new silos and enable inert gas to be automatically introduced to the headspace 3 of the silo in a controlled way where the flow rate of the gas increases gradually.
• the apparatus 4, 4', 4" is not prone to the errors of prior art systems and does not involve the same cost implications.
• the apparatus 4, 4', 4" reduces the risk of a dust cloud forming in the silo and will therefore reduce the risk of fires or explosions occurring therein.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Public Health (AREA)
• Health & Medical Sciences (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Fluid Mechanics (AREA)
• General Physics & Mathematics (AREA)
• Automation & Control Theory (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2015
  • 2015-01-22 GB GBGB1501077.0A patent/GB201501077D0/en not_active Ceased
• 2016
  • 2016-01-22 WO PCT/EP2016/051380 patent/WO2016116624A1/en active Application Filing
  • 2016-01-22 EP EP16701350.7A patent/EP3247468A1/de not_active Withdrawn

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