A method and apparatus for suppressing explosions and fires.

Device for suppression of explosions and fires

The invention relates to a device for suppressing, extinguishing or preventing a fire or explosion in a certain area.

The term housing as used in this specification means any confined space such as a duct, recess, tank, spray dryer, cyclone, silo, fluidized bed dryers, hold, conveyor, storage tank, pumping station or similar space that can be opened and closed and that can be at any pressure (i.e., under overpressure or underpressure) or at temperature (i.e., above or below ambient temperature).

Various devices are available to prevent or suppress dust explosions in tanks such as dryers, cyclones, interconnectors, fluidized bed dryers, and powder silos in milk powder factories. All such damping devices operate on the principle that the explosion is not in the blink of an eye, but takes a measurable time of - 40 to 100 thousandths of a second to form a destructive pressure. During the first stage, the pressure rises slowly, with a maximum pressure of about 1.5 psi. After this, the pressure rises rapidly and is up to 100 psi during the second lie. The duration of the steps associated with the increase in pressure depends on the size and shape of the enclosure in which the explosion takes place. It has generally been found that in order to suppress an explosion sufficiently, the initial ignition must be suppressed and extinguished within 10 to 200 thousandths of a second. In order to meet this requirement, the response time of conventional suppression devices must be very short.

Conventional suppression devices generally have a detector that indicates an increase in pressure due to an explosion as soon as the pressure phase begins, at a pressure of 0.5 psi. When an explosion occurs in the housing, the control system generates a signal to puncture the membrane at the outlet of the suppression charge container, which feeds the charge of the explosion-suppressing material into the housing. Such suppression systems interrupt the heat transfer of the particles by breaking the combustion chain and preventing a rapid rise in pressure.

Three different suppressants are commonly used. These include chloromethane (Halon 1011), monoammonium phosphate based dry powder (MAP) and water. Moore reported in The Chemical Engineer in November 1986 and December 1984 that Halon 1011, MAP powder, and water are effective agents for suppressing explosions. However, the effectiveness of these three different suppressants varies depending on the nature of the explosion. Halon and MAP can contaminate the containers in which they are placed, which is a major drawback, especially in the food industry. Conventional water-based suppression devices are short-lived and involve a higher risk of re-ignition.

Roughly the same comments apply to extinguishing a fire in a particular area. In this context, fire means a flame front that propagates at any speed, and not just an explosion that can be considered a fast-moving fire. Thus, the distinction between the terms fire and explosion is not clearly defined, so depending on the context, these terms may alternate in this explanation.

An improved device is therefore needed to suppress, extinguish or prevent a fire or explosion.

The present invention therefore relates to such an improved device.

According to the invention, there is provided a device for suppressing, extinguishing or preventing a fire or an explosion in a certain area, characterized in that it has a content device for pressurized water and a heating device for heating water in the tank device without adding water to the tank device. and a valve device for closing the discharge device, when a valve device opens as a result of a fire or explosion in the area to supply hot pressurized water from the tank device to that area at a pressure greater than the area pressure, some water forming a vapor cloud when introduced into the area and some water flaring when entering the lower pressure area.

One advantage associated with the use of hot pressurized water is that, in addition to the already well-known water suppression properties, flash steam is also used, which increases the rate from unit pressure to atmospheric pressure, so it is very fast to suppress reaction time explosions or extinguish fires. In addition, water droplets and flash vapor help prevent a new fire or explosion. Furthermore, because the suppressant must be freely available and easy to place in the suppressor container, it is considerably less expensive than current suppression systems. In addition, such a repellent is safe to use, does not contaminate, is not corrosive, and is also non-toxic.

Preferred embodiments of the device according to the invention are set out in the appended claims 3 to 12.

According to a preferred construction of the invention, the container device comprises a pipeline with an outlet device associated with the housing. The pipeline is preferably a circulating line which is substantially around the housing and comprises a plurality of spaced-apart discharge devices associated with the housing. The heating device may comprise a device for heating the pipe, for example a steam or electric heater or a hot air dryer.

According to another structure of the invention, the tank device comprises a pressurized suppression tank. The heating device can then be an electric heating element. Alternatively, the heating device may be a heating coil through which steam is supplied to heat the water in the pressurized suppression tank.

According to one structure of the invention, the outlet valve device is a membrane part.

In a structure according to the invention and specifically preferred, the membrane part comprises a pressure membrane unit with two separate membranes, between which a pressure space is formed, the pressure of this space splitting as said membranes are lowered according to predetermined conditions. The pressure in said space can be released by a solenoid valve based on the explosion conditions present in the housing connected to the membrane.

One structure of the invention has a device for minimizing the air space between the membranes. Alternatively, said space may be pressurized with an incompressible liquid, for example water, or a high-boiling inert liquid such as glycol. In the second case, said space can again be partially filled by an inner part which comes out of the films as they crack. Such an inner part is an inert, preferably water-soluble substance.

According to another structure of the invention, the device comprises a separate device for detecting explosion conditions in the housing and a control device for splitting the membrane so that a charge of hot pressurized water can be released into the housing when the explosion detector is activated.

The housing explosion condition detection device may comprise a membrane-shaped pressure detector, pressure transducer, U-tube detector, heat sensor or infrared detector.

According to another preferred aspect, there is provided an apparatus for extinguishing a fire in a given area and comprising a tank device for pressurized water and a heating device for heating water, the tank device comprising an outlet device closed by a valve device opening in the event of a fire in said area. greater than the pressure in this range, a portion of the water forming small droplets upon entering said area and a portion of the water forming a vapor upon entering a region of lower pressure to extinguish or prevent a fire while the vapor cloud remains in place to prevent re-ignition.

In one construction according to the invention, the tank device comprises a pressurized suppression tank with hot pressurized water and an outlet device for supplying hot pressurized water to said area, said outlet device being closed by a valve device which opens when a flame appears in this area. The discharge device preferably comprises a pipeline surrounding the entire area or at least a certain part thereof and comprising a plurality of outlets opening into this area.

In another related construction according to the invention, the tank comprises a pipeline with a plurality of outlets extending into the area, the heating device being a steam or electric heater or a hot air dryer. The valve is preferably a solenoid valve.

In connection with the invention, there is further provided a pressure film unit having two separate films and a pressurized space therebetween, the pressure of which is lowered so as to cause the films to rupture under predetermined conditions. In the structure according to this aspect, the pressure in said state is released by the valve

9 0 09 when activated when an explosion condition occurs in the housing connected to the membrane.

According to one structure of the invention, a device is provided for minimizing the air space between the membranes.

In the second case, said space is pressurized with an incompressible liquid, for example water, or an inert liquid having a high boiling point.

Instead, in another case, said space is partially filled with a material that sprays out of the films as they crack.

The filler may be an inert, preferably water-soluble material.

For ease of understanding of the invention, reference is made to the following description, which is given by way of example only, with reference to the accompanying drawings, in which Figure 1 is a side view of a device according to one embodiment of the invention, Figure 2 is a diagram of another device of the invention 2 of one of the devices shown when used in a spray dryer, Fig. 4 is a side view of the part shown in Fig. 3, Fig. 5 is a side and partial cross-section of another part of the device of Fig. 2 used on a cooling pad, Fig. 6 is a graphical representation of pressure build-up versus time, Fig. 7 when the explosion is attenuated when the device according to the invention is used, Fig. 8 is a flow diagram of the pressure film according to the invention when used, Fig. 9 is a schematic perspective view of a device according to the invention in another embodiment, Fig. 10 is a schematic perspective view of another device according to the invention, and Fig. 11 is a side view taken along line XI-XI of Fig. 10.

The drawings, and in particular Figure 1, show a device 1 for suppressing, extinguishing or preventing a fire or explosion in a certain area. In this case, the device is specifically intended for the suppression of explosions in the housing 2. The device 1 has a container, in this case a pressurized suppression unit 5. The unit 5 is in this case essentially cylindrical and has a bleed opening 7 connected to the inlet 4 of the housing A certain amount of water 8 is fed to the suppression unit 5 and heated therein by a heating device, in this case an electric heating element 9, which heats the water to a temperature below the boiling point of the water at a certain pressure in unit 5. The suppression unit 5 is maintained by air or other suitable inert gas.

In this case, when the unit is not pre-pressurized, the unit pressure is provided by the generated steam.

The outlet 7 of the damping unit 5 is closed by a valve device, which in this case is a high-speed pressure diaphragm 10, which, as will be described in more detail below, is broken so that water is transferred from the damping unit 5 to the housing 2 by the explosion conditions. The diffuser can be placed at the inlet of the tank 2 to direct the hot pressurized water supply to the housing 2 when the pressure film 10 is torn or cracked.

When the device is used, the water charge is fed to the damping unit 5 through the filling opening 16 and the water is pressurized to the desired pressure, for example 500 psi. The water is then heated by the heating element 9 to a desired temperature which is less than the boiling point of the water at a pressure of the damping unit. When the pressure is

500 psi water can be heated to 232 ° C. The control device can be used to keep the temperature and pressure at the right levels. The pressure may be provided by a compressed gas, for example air or nitrogen, or by the heating effect of a water charge, or a combination of both.

Under the conditions of the explosion in the housing 2, their detector, for example the membrane detector, sends a signal via the control system to break the membrane 10, so that the hot pressurized water charge is caused to leave the damping unit 5 in the housing 2. Since the water is at a considerably higher pressure than the pressure of the shutter 2, as the water enters the housing 2, part of it turns into water droplets and suppresses the flame front in the blink of an eye and part of the water turns into flare vapor and reduces oxygen concentration

When pressurized water is heated, its temperature rises, so the liquid heat of the water also rises. The liquid heat of high-temperature, high-pressure water is released at lower temperatures as latent heat and converts a certain amount of liquid into flash vapor. More than 70% of the liquid can be converted to vapor at atmospheric pressure. When disassembled, the water element behaves normally and forms water droplets to suppress blinking. In addition, the flash vapor lowers the oxygen concentration in the housing below a level that promotes combustion and prevents re-ignition.

After the initial charge of hot compressed air, continuous steam removal takes place from the steam pipe of the process used as the membrane 10 ruptures or by activating a fixed water jet system which helps maintain damping conditions and prevents re-ignition in the housing.

It should be noted that the damping container can be connected to the housing wall with a portion having a flexible coil to receive a certain weight and reaction from the housing 2. To keep the housing sterile, an outlet pressure plug can be inserted into the housing outlet.

It should be noted that the discharge time of the pressure relief tank is proportional to the pressure, the area of ​​the discharge nozzle and the length of the movement concerned. Different nozzle designs can be used for best performance and damping units can be placed in many places around the housing for best results.

The device according to the invention makes it possible to enhance the properties of water by forming a unique combination consisting of damping and inertial properties.

Another important advantage is that when the unit performs the removal, the additional space is immediately replaced by flash steam. This again creates a state where the outlet pressure of the studio is almost constant. Since the pressure is considerably higher than hot pressurized water than with an inert gas, for example nitrogen, the discharge rate V₁ is also larger.

When using only a fraction of the extra heat to transfer water away from the tank, the remaining excess heat can be used for other purposes. This excess heat enters thermal equilibrium at atmospheric pressure as it transforms into steam. When converted to steam, it expands enormously compared to its liquid volume. For example, 1 kg of water requires 0.001 m³ volume, while 1 kg of steam at atmospheric pressure requires 1.673 m³volume. Therefore, the steam now has a volume 1630 times the original volume. This large expansion gives rise to a very high secondary velocity V₂. Expansion also explodes water into very fine particles, very close to molecular particles. This forms a vapor cloud that remains in suspension and suppresses the explosion as well as effectively prevents secondary recrystallization.

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A unique combination comprising an almost constant outlet pressure V_x and the associated secondary velocity V₂ makes it possible for damping units to be designed for very low pressures - namely 2 to 10 bar - however, the speeds are even higher than in more loaded units.

Because the system uses a commonly available damping material that is easy to place in the damping tank, it is significantly less expensive than current damping systems.

In addition, because the pressure in the training system can be controlled, it can be easily shut down for inspection or cleaning of the associated housing. In addition, the pressure in the vessel can be easily changed with a thermostat by controlling the temperature. In addition, the damping agent used is safe, does not contaminate or corrode, and is also non-toxic.

In the device according to the invention, when the hot pressurized water charge is discharged and the pressure drops, the flash vapor immediately fills the volume of the damping unit and keeps the pressure approximately constant. Thus, the damping tanks can be emptied at a fairly high constant pressure, resulting in a considerably shorter reaction time. In conventional devices, the damping units are pressurized with propellant. When the damping tank is emptied, the pressure of the propellant decreases, thus increasing the time required to discharge the damping charge. Very high pressure is usually required to compensate for this. However, the device according to the invention does not present this problem due to the structural improvement of the compensating discharge pressure, which comprises flash steam and steam expansion.

In addition, the housing cannot re-ignite due to saturation, heat transfer interference and oxygen depletion.

Depending on the properties of the material to be treated, re-ignition can be prevented by wetting the particles. In this case, the operating parameters are calculated and, on the basis of the maximum possible dust or powder concentration, the amount of water required to increase the moisture content of the particles to a level at which re-ignition does not take place is then calculated. This is very important in the case of hygroscopic powders, for example milk powder made from skimmed milk.

In use, the vapor cloud and atomized water particles form a moisture barrier between the dust particles to prevent re-ignition.

In addition, the steam lowers the amount of oxygen to a level that does not promote re-ignition. In this case, the volume of steam used is such that it reduces the mixture of air and steam to about 14% by volume. The following calculation can be used to determine the amount of water that needs to be heated to obtain the required volume of steam at atmospheric pressure.

Tank capacity «V

Without volume V is, 22V 0₂ and 0.78V nitrogen.

To obtain 14% 0₂, = 0.22V

100 V + x, where x is the volume of gas / steam added.

When this equation is solved, x «= 0.57V is obtained.

The volume required for 1 lb of steam at atmospheric pressure is 26.8 cubic feet / lb.

Thus, the weight of steam required is 0.57V

26.8 = 0.02 V lb (p

Different operating pressures result in different flash vapor volumes. When the operating pressure is P_o the amount of flash vapor depends on the heat of the liquid h_L at operating pressure P_o and atmospheric conditions, which are latent heat L =

970.4 Btu / lb and liquid heat h_L = 180 Btu / lb.

Therefore, the amount of flash steam available for the unit weight of hot pressurized water is h, (operating pressure P „) - 180

970,4

When Equation (1) above is combined, the total weight (W) of water that needs to be heated P_ocan be calculated as follows:

W = 0.2V x 970.4 _______ _______ 20.7V _____________ h_L (operating pressure P_o) -180 (h_L (operating pressure P_o) To 180), where

V = volume of the tank in cubic feet, h_L = liquid heat at operating pressure P_o,

W = weight of water to be heated (in pounds) to give the desired concentration of flash vapor at atmospheric pressure to reduce the oxygen concentration in the tank to 14% by volume.

For enclosures to be protected, a certain number of damping device units according to the invention are normally attached to the housing at preselected locations, thus obtaining maximum propagation and explosion damping properties.

The units can be designed to suppress or extinguish limited blinking in virtually all types of gases, vapors and dusts and can be applied in particular to the petrochemical and chemical industries, the pharmaceutical and food industries and the agro-industry.

Example

The explosion suppression tester was designed based on the international standard ISO 6184. The container was cylindrical in shape with a volume of approx

2.5 m³ and aspect ratio 2. The dust dispersing mechanism comprised two groups of jet rings, each with 15

0 09 spray holes with a nozzle diameter of 5 mm. Both jet rings were fed by a 5 liter powder tank. Ignition took place with two pyrotechnic igniters with a total energy of 10 KJ. The igniters were operated from a low voltage source, and the control device was a PLC, which determined a certain delay after the dispersion of the dust. The powder was fed from said containers and sprayed into the container of the device. After a certain time, which is usually 600 thousandths of a second, the igniters were activated and the pressure changes were recorded by two pressure transducers.

First, an unattenuated explosion test was performed with a powder made from skim milk, and Figure 6 shows graphically the pressure in bars and thousandths of a second.

In Fig. 6 the x-axis - each degree is 50 thousandths of a second, the y-axis - each degree is 1 bar, the mean time - 2000 thousandths of a second, the ignition time - 1758.64 thousandths of a second valve time - 978.658 thousandths of a second, the maximum pressure - 6.3 bar.

It should be noted that in the initial stage the pressure increase is relatively small, but then comes the second stage where the pressure rises faster.

The damped explosion test was then performed using hot pressurized water in the same tank under the following conditions and also using the same material as in the non-damped explosion test.

Pressure 9.1 bar, temperature 180 'C, volume of water in the tank m³ per = 0.65 1 / m³, outlet diameter = 3, nozzle not used.

The pressure curve obtained on this basis in bars versus time (thousandths of a second) is shown in Figure 7.

In Figure 7, x-axis - Each degree 100 thousandths of a second, y-axis - Each degree 0.025 bar, mean time - 1750 thousandths of a second, ignition time - 1737.22 thousandths of a second, valve time - 949.583 thousandths of a second. It can be seen from Figures 6 and 7 that the maximum pressure decreases from about 6.3 bar to about 0.35 bar with the arrangement according to the invention and thus dampens the explosion. This can be achieved inexpensively, safely and quickly, and by using a damping device that does not contaminate the tank.

Figures 2-5 show an explosion damping device according to another structure of the invention, shown in use in a spray dryer 20, a cooling pad 21, a cyclone group 22 and connecting ducts. The device has reservoirs, in this case main pipes 25 for pressurized water, each comprising a plurality of spaced openings 26 closed - each separately - by a valve device, for example a pressure membrane 24 which ruptures when an explosion occurs in the housing to allow hot pressurized water to enter the housings. Each outlet 26 is connected to the housing 20, 21 or 22 by flexible beams 27 made of stainless steel. The water in each pipeline 25 is heated by an electrically operated surface heater 28 which is controlled by a thermostat so that the pressure water temperature in the pipeline 25 remains at the desired level. Heat release 29 (only a portion of which is shown in the drawings) is provided for each of the pipelines 25 and the outlets 26. Pressurized damping tanks can be arranged at least for larger diameter annular pipelines, so that more tank volume is obtained. The pressurized annular pipeline can also be used without a tank by only partially filling the pipe with water and leaving space for expanded water and an upper space for flash steam.

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One advantage of using a ring tube for suitably shaped housings such as a dryer 20 and cyclones 22 is that it can easily withstand the pressure water discharge during the discharge operation.

The electric heater makes it easier and more efficient to control the temperature and keeps the temperature constant, ensuring a balanced exhaust function. In addition, pipeline units - both ring-shaped and straight sections - can be easily fabricated to suit all applications.

It should be noted that in order to facilitate discharge and to maintain the headspace and pressure, each outlet of the damping unit - in the case of both the tank and the pipeline - is arranged to form a filled leg between the tank and the outlet associated with the housing.

Figure 6 shows graphically a film unit 40 according to the invention which can be used in the explosion suppression device described above. The membrane unit 40 comprises two rupturable membranes 41, 42 spaced apart, leaving a pressure space 43 between them which is pressurized from the air or gas tank 50 through the inlet 44. The outer membrane 41 is subjected to the pressure P in its pipeline₂, on which the unit is mounted, and the inner diaphragm 42 is again subjected to the pressure P in the housing_x, which is usually, but not necessarily, atmospheric pressure.

Equilibrium pressure P in state 43₃ (200 psi) makes it possible for a 300 psi membrane to withstand the higher pressure of the discharge unit, for example 400 psi. When an explosion occurs in the housing, the pressure in the space 43 is released, for example, by a solenoid 51, which allows the higher pressure in the explosion-proof container 50 to break both membranes 41, 42 and discharge into the housing. The air supply from the tank 50 to the space 43 is closed during the extraction, so that no air can escape into the housing.

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In the case of the membrane shown in Fig. 8, the emptying time for lowering the internal pressure of the space 43 is the time required to reduce the internal pressure from 200 psi to 100 psi. At this point, the pressure in the discharge unit corresponds to a rupture pressure of the membrane of 300 psi, and the membranes begin to flex. The emptying time measured in millisecond seconds depends on the volume to be emptied and in this case corresponds to the time required to lower the pressure in the space 63 from 200 psi to 100 psi.

The pressure diaphragm units can be sealed and the pressure can be released with an electric ball, solenoid valve or the like.

The volume of space 43 is preferably kept to a minimum so that a rapid response is more easily obtained. The space 43 is preferably at least partially filled with an inner part which considerably reduces the volume of the air space, so that the estimated time required to evacuate the air to the activation pressure is considerably reduced. For example, 340 cm³ in a volume reduced by 15 cm³using the inner part, the estimated emptying time decreases from 16 thousandths of a second to about 2 thousandths of a second. Thus, the membranes rupture almost in the blink of an eye, allowing the explosion to be suppressed very quickly. The inner part may be a conventional water-soluble material. The inner part also contributes to reducing heat loss, as it acts as an insulating barrier.

Alternatively, the space 43 between the membranes may be filled with an incompressible liquid, for example water. Water can be effectively pressurized to 200 psi with a mixture of air and gas, maintaining the control pressure. In the event of an explosion, a solenoid is activated which connects space 43 to the outside air. The water pressure stops immediately and is subjected to a much higher tank pressure of 400 psi, as well as an outlet connected to the outside air. Thus, both membranes rupture simultaneously.

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It should be noted that the membranes described above have a wide range of applications in fields other than explosion trainers or fire extinguishers, so the invention is not limited to these explosion suppression system membranes. The invention also relates to actual control pressure membranes.

In addition to the explosion-suppressing function of limited blink-of-an-eye fires, a hot water system can also be used to extinguish fires; these include fires involving flammable liquids or gases, surface fires involving flammable solids and fires penetrating deep below the surface, the surface material being then granular or fibrous material.

Figure 9 shows a typical fire extinguisher with two tanks 80 connected to a manifold 81 with transverse sections terminating in nozzles or dispensers 82. Insulated tanks 80 are filled with water heated above atmospheric temperature to the desired pressure and temperature. hot water is discharged from the tanks 80 through valves 85, 86.

Figures 10 and 11 show an alternative fire extinguishing device. In this case, the container is formed as a tube 90. Below the tube 90 are mounted transverse portions 92 having nozzles or dispensers 93 at their ends. The pipes are also insulated to eliminate heat loss. The hot pressurized water is caused to come out of the pipe 90 by means of trip valves 96, for example solenoid valves located on the lower surface of the pipe, each transverse part 92 comprising one such release valve 96, such as

009 specifically Figure 11 shows. The fire is detected by suitable detectors capable of detecting heat, flames, fumes, burning steam, etc. The rate and amount of hot pressurized water release depends on the application used. When a fire is detected, the valves open and send a hot pressurized water charge to the area where the nozzles or dispensers are located. When hot pressurized water is supplied to a certain area whose pressure is higher than the pressure of said area, part of the water generates steam and part of the water leaves as steam. Water droplets and steam prevent the heat transfer of the particles and the possible chemical reaction between the fuel and oxygen. Water droplets and steam also extinguish the fire by boiling and / or diluting or reducing oxygen.

When air is used for pre-pressurization, the pressure of the initial charge can be lowered so as to produce a temperature rise which causes a corresponding increase in pressure in the closed space. This applies to the damping units and the differential pressure diaphragm. Pre-pressurization of the damping units is optional in certain applications and the flare vapor generated by the unit can also be used.

It should be noted that various additional chemicals can be added to the hot pressurized water charge to achieve the desired results in quenching explosions and / or extinguishing fires.