FR2991334A1 - ALGINATES AS MEANS FOR FIGHTING FIRE AND EXPLOSION HAZARDS OF EXTRACTIVE ORGANIC MATERIALS - Google Patents

Abstract

The invention relates to the use of all types of alginates diluted with water and mixed with flammable organic materials from the extractive industry, as a means of combating fire risks caused by self-heating and the risks of dust explosion caused by the particles and microparticles contained in said organic materials as well as by the explosive gases released during the self-heating process, occurring during the storage, transportation or handling of said organic materials.

Description

TECHNICAL FIELD OF THE INVENTION The invention relates to the use of all types of alginates as a means of combating the risks of dinosaurs. fire and explosion of extractive organic material occurring during storage, handling or transport.

BACKGROUND TECHNOLOGY The materials from the extractive industry (mines, quarries, processing industries, ...), such as petroleum coke, coal, coal coke, are, when they consist of flammable organic materials , causing fires caused by self-heating and dust explosions caused by the particles and microparticles contained in said organic materials as well as by explosive gases, such as carbon monoxide, released during the heating process. self-heating. Concerning the limitation of the dust emissions, various processes, physical or chemical, related to the protection of the personnel as well as the respect for the environment, were developed. Concerning the limitation of the risks of fire and explosion of materials from the extractive industry, during their storage, handling or transport, the quenching water, resulting from the starch industry, was used. Unfortunately, this material is quantitatively limited given the huge volumes of product to be processed in the world. On the other hand, as regards the prevention of these risks, various prevention and monitoring techniques have been put in place without any of them having, to date, taken into account the fineness of the particles of the materials and the fixation of Condensation Moisture, which are the main causes that can lead to fire due to self-heating or explosion, dust, gas, or hybrid (dust and gas) The data listed below, which are necessary understanding of the scientific and experimental path that led to the discovery of unknown characteristics relating to alginates diluted with water, come from the final report of the INERIS ECSC Convention n ° 7262/03/307/03 of 1996 entitled "Study fire and explosion safety of day coal and steel plants ", as well as data from the same organism concerning organic materials giving off flammable dusts.

Analysis of the ignition phenomenon by self-heating of extractive organic materials The storage of coals and cokes, and by extension: organic materials of extractive origin, induces potential sources of fire following a self-heating of products. This risk concerns the main danger of this kind of installation. The self-heating phenomena of coke and coal essentially depend on: - the critical dimension of storage, which is in most cases out of date; - oxidation reactions taking place inside the product; - the initial temperature; - moisture fixation. Although the rates of oxidation of coal or coke are more or less low depending on their reactivity, they nevertheless play an important role for large storage areas where the critical dimension is largely exceeded. Moreover, this rate of oxidation, which increases with the rise in temperature, also increases when the grain size of the materials in storage decreases, since the specific surface that can be adjusted increases strongly in this case. In addition, the fixation of humidity by condensation in the storage contributes greatly to the elevation of the storage temperature, which accelerates the oxidation phenomena and of course the self-heating. In fact, a condensation of the order of about 1% moisture, induces a significant increase in temperature of the order of 20 ° C. Generally, the firing of a fire, for most coals or cokes, requires additional energy input in the form of minimum ignition energy to overcome the barrier of activation energy of the system. To have a combustion, it is also necessary to reach the minimum temperature at which the reaction with flame development will occur. This temperature is called the ignition temperature.

With high molecular weight substances such as coal or coke, the decomposition must first occur well before reaching the ignition temperature. These phenomena take a certain time called induction period. We only talk about inflammation if a flame is visible. The induction period is reduced when the temperature increases. It also depends on the pressure, the fuel concentration, the type of material, therefore its reactivity and its contained additives. The larger the sample volume, the easier the heat buildup will be. To avoid the risks associated with self-heating, it is thus necessary either to store coal or coke in quantities less than the critical volume for a given deposition temperature, or to work under an inert atmosphere. In reality, these two possibilities are not realized, the critical dimension being generally low (a few meters) and storage under inert atmosphere not being possible for open storage. The rate of oxidation of coals or cokes at room temperature is very low and plays an effective role in the self-heating phenomenon only for large heaps and after a very long time. This is the time required to go from the storage temperature of coal or coke (ambient temperature) to a temperature of the order of 70-80 ° C beyond which self-heating takes place.

On the other hand, the oxidation rate increases as the grain size decreases. Indeed, when the particle size decreases, the specific surface of the grains increases and therefore also the surface capable of reacting with the oxygen of the air. The pyrite content is also a factor influencing the rate of oxidation. The presence of pyrite in the form of small particles well dispersed (large surface area) promotes self-heating while the presence of massive pyrite does not lead to a significant increase in the rate of heating. Nevertheless, such a reaction can only be used to start the heating because the pyrite oxidizes quickly in a very humid atmosphere. From 80 ° C, it is likely that the coal dries quickly but the rate of oxidation of the coal itself has then reached a sufficient value for the heating by chemical oxidation continues. Hence the importance, beyond their own reactivity of the coal and / or the coke, of the fineness of the particles of coal or coke and the fixation of humidity by condensation in the phenomenon of inflammation by warming up.

Analysis of the phenomenon of dust explosion or hybrid (dust and gas) emitted by extractive organic materials The explosion is a rapid combustion of a mixture of gas, coal dust or both, with air, in a confined or partially confined space, in which the heat released is more important than the heat lost in the environment.

In industries related to coal and similar materials, explosions are related to the presence of large quantities of dust formed during the handling or crushing of fuels. Explosions may also be due to pyrolysis or incomplete combustion gases (carbon monoxide) formed during the self-heating of coal deposition. The energy released by a source of ignition initiates the combustion of nearby particles. Under the effect of this heat source, there is then a pyrolysis of coal dust generating combustible volatile compounds which ignite. Reaction rates are high since the specific surface area of the fuel is very important. If the cloud is dense enough, the radiation and convection heat up the neighboring particles and the explosion spreads gradually. The reactive mixture of air and "cold" carbon particles (room temperature) is transformed into "hot" combustion products (1200-2000 ° C). The mixture of air particles passing through the flame consequently undergoes a strong thermal expansion (the volume is multiplied by at least 5). The phenomenon of dilation is responsible for the pressure effects observed during an explosion in a confined or partially confined space. In free atmosphere, case of ground stocks, it is observed only a fireball with a very low overpressure, but with a significant thermal effect. This is the "flash". In the closed chamber, the pressure effects are much greater (maximum pressure of the order of 5 to 10 bars) and can lead to the destruction of the devices. This is called an explosion.

The explosion is a particular combustion using the following specific parameters: - the dust must be in suspension to form a large surface of contact with the air; - the dust concentration must be sufficient (above the minimum explosive concentration); - the atmosphere must be confined so that the pressure can increase. To eliminate any risk of explosion, simply remove one of the components involved in the phenomenon of combustion or ignition. Beyond the combustion and dust ignition characterizations necessary for an explosion of organic dust to take place, various conditions relating to dust and their fineness, as well as the concentration and combustion of these dust in an atmosphere more or less less confined and especially in a closed environment, must be met. Hence the importance of the fineness of the particles of coal or coke in the phenomenon of explosion. SUMMARY OF THE INVENTION The invention relates to the use of all types of alginates diluted with water and mixed with flammable organic materials from the extractive industry, as a means of combating the fire risks caused. by self-heating and the risks of dust explosion caused by the particles and microparticles contained in said organic materials as well as by the explosive gases released during the self-heating process, occurring during storage, transport or manipulation of said organic materials. According to nonlimiting features of the invention: the alginates are diluted with water and mixed with the material to be treated in respective proportions capable of obtaining, for an "index P" passing to 31511m, a percentage fines not more than 6%; the alginates are diluted with water with a dilution ratio of between 2 and 10%; the diluted alginates are mixed with the material to be treated with a dosage rate of between 3 and 15%; the diluted alginates are pulverized, misted or atomized by means of adapted ramps situated in the zone of the successive conveyor belts arranged so as to subject the material to be treated to successive turns, with a good homogeneity of the alginate solution in the materials treat ; - The materials to be treated are selected from petroleum coke, coal, coal coke. The applications of alginates are numerous. - In phytopharmacy, they are used for the physical protection of wounds in arboriculture, market gardening and horticulture. They participate as an ingredient in the encapsulation of chemicals and living organisms such as symbiotic bacteria. - In pharmacy, they play a role of thickener, gelling agent and dispersing agent for the tablets. - In medicine, many drugs contain alginates. They are used as an anti-inflammatory, as an appetite suppressant in the fight against overweight, to stop bleeding with the use of dressings. They also participate in the manufacture of bio materials and implants. - In industry, alginates are used as a thickener in the textile to fix the dye, as a protective film during the manufacture of paper and in the coating of solder rods to avoid oxidation. They are integrated in the manufacture of very diverse products such as plaster moldings, ceramics, glues, resins, pencil leads and paint where they increase the viscosity and the sedimentation time of the preparation to make it more homogeneous . - For the environment, alginates are used in surface water treatments to remove suspended solids. Communities use them as a binder in the hydroseeding technique to seed slopes and embankments (highways, ring roads). This technique consists of using an emulsion with water, herbaceous seeds, growth promoter, fixative and seedling cover on the soil. - In agriculture, they are also used as fertilizers, additives, wetting, or for the protection of erosion thus limiting the gully. - In cosmetics, brown algae find many outlets such as shampoos, toothpastes and skin care. - In agri-food, the antioxidants they contain prevent the oxidation of fat in food. None of its applications deals with the use of alginates as a means of combating the fire and explosion hazards of extractive organic materials occurring during storage, handling or transport. Choice of the qualitative proportions of the composition containing alginates diluted with water, had the following objectives: - to increase the size of the grains by permanently agglomerating the particles and more particularly the microparticles of the extractive organic products of the coal or coke types; - To avoid lasting moisture fixation by condensation by acting as wetting said particles and microparticles. The choice of said composition also focused on compositions that are easy to obtain and to use, at a cost price that is compatible with the application in question and whose resource is almost inexhaustible. The material that has been selected for testing, which is particularly prone to contain dust and the risk of fire by self-heating, is petroleum coke.

The use of the tested composition on products of organic origin such as coals or cokes makes it possible to very greatly reduce the risk of fire resulting from self-heating thanks to the wetting effect and the durable agglomeration. particles, increasing the size of the grains, reducing the fixing of condensation moisture and avoiding any increase in mass of the temperature which helps to avoid internal oxidation phenomena, and therefore to stop any self-heating effect and explosion. The implementation of the composition also leads to a very significant reduction of environmental hazards, a reduction that may be followed by a reduction in the means of prevention and control, a source of financial savings, and in particular with regard to: the orientation of ground stocks relative to prevailing winds; - the effects of chimneys, which will be removed; - compaction that can be avoided; - inventory management which can be very light; - the monitoring of stocks which may be reduced, in particular as regards the temporal controls of temperatures. The composition used, which is wetting, natural, nontoxic and biodegradable, can be diluted with water with ease of implementation that can be used in various application techniques such as spraying, misting, atomization at the same time. means of adapted ramps. Used as a wetting agent and fixer for inorganic and / or organic particles and microparticles, such as carbon or coke, for example, it allows the particles and microparticles to agglomerate over a period of several months and increases the size of the fine grains. The implementation of this composition, a function of a certain dilution rate with water and a dosage rate in its implementation, allows, over a period of several months: a) with regard to the dangers flammable organic dust materials such as coal or coke: - to greatly reduce the risk of fire due to self-heating due to the durable agglomeration of particles increasing the grain size, reducing the fixation of moisture condensation and avoiding an increase in mass of the temperature, which help to avoid internal oxidation phenomena, and to stop any self-heating effect and fire; -8 - reduce the risk of dust and / or gas explosion as a result of the long-term agglomeration of particles and microparticles and the increase of grain size; - to reduce the means of prevention put in place in the context of fire prevention due to self-heating (orientation of ground stocks, chimney effect, compaction, inventory management, inventory monitoring, etc.); - to reduce the fire and explosion isolation distances determined in the context of hazard studies of ICPE (Installations Classified for the Protection of the Environment); (b) with regard to dust: - to reduce or even completely and permanently suppress dust emissions by contributing to an improvement in the quality of ambient air; - to minimize the health effects induced by PM10 and especially PM2.5 present in the ambient air and especially with regard to organic dusts of coal and coke; - to comply with the regulations and to avoid, in the majority of cases, the mandatory annual declaration concerning pollutants, which must be made from a threshold of 50 t / year for PM10 and a threshold of 150 t / year for total dust; - to contribute to the protection of the environment by reducing environmental disturbances and the effects or impacts on vegetation, agriculture, landscape, housing and material goods, monuments and the architectural heritage; (c) with regard to profitability - to reduce loss of material from wind and handling, as well as waste; - to minimize the costs of surveillance, control and prevention; - to obtain a financial gain that can be substantial, financial gain for the buyer of the form (excluding taking into account the cost savings related to monitoring, control and prevention): - to reduce or even eliminate the costs of the TGAP particulates (General Tax on Polluting Activities) as a result of the extension of the T.G.A.P tax base applicable in France since 01/01/2009 and also in the European Community. The features and advantages of the invention will appear more clearly on reading the following detailed description of at least one preferred embodiment thereof given by way of non-limiting example.

DETAILED DESCRIPTION OF THE INVENTION The invention relates to the use of all types of alginates diluted with water and mixed with flammable organic materials from the extractive industry, as a means of combating the risk of fire caused by self-heating and the risk of dust explosion caused by the particles and microparticles contained in said organic materials as well as by the explosive gases released during the self-heating process, occurring during storage, transport or handling of said organic materials. According to nonlimiting features of the invention: the alginates are diluted with water and mixed with the material to be treated in respective proportions capable of obtaining, for a "P index" passing to 315 microns, a percentage of fines not more than 6%; the alginates are diluted with water with a dilution ratio of between 2 and 10%; the diluted alginates are mixed with the material to be treated with a dosage rate of between 3 and 15%; the diluted alginates are pulverized, misted or atomized by means of adapted ramps situated in the zone of the successive conveyor belts arranged so as to subject the material to be treated to successive turns, with a good homogeneity of the alginate solution in the materials treat ; - The materials to be treated are selected from petroleum coke, coal, coal coke. The tests were carried out using compositions containing alginates extracted mainly from the Pheophycea class of brown algae, which are formed from two monomers bonded together: mannuronate or mannuronic acid, some of which are acetylated and gluconate or gluconic acid. The proportion and distribution of these two monomers is critical for a broad expansion of the physical and chemical properties of alginate. Its chemical composition varies among different species of algae, different parts of the same plant and is subject to seasonal changes. Nevertheless, by selecting raw materials with different properties, it is possible to manufacture a variety of alginate with constant characteristics. Alginic acid is derived from algae and allows the production of sodium alginate and calcium fibers. Alkaline alginates form viscous colloidal solutions in water. If alginic acid is insoluble in water, sodium alginate is very soluble in water, and calcium alginate is only soluble in the basic medium, especially in soap solutions which are almost always quite alkaline. Its fibers are also used as passenger supports, which will be eliminated after manufacture, washing or by fulling. Of course, the invention also relates to all types of alginates whether natural or synthetic. The manufacturing process is essentially that described below, other variations are obviously possible .. The algae is cut and cleaned after harvesting. It is then macerated in a diluted mineral acid to be demineralized.

The alginate contained in the algae is thus transformed into alginic acid and, at the same time, some undesirable constituents are eliminated. The demineralized algae are milled in the presence of an alkali or an alkaline salt to neutralize the alginic acid and solubilize it in the corresponding salt form.

Alginate is extracted and processed. It is precipitated, pressed, washed and drained, then neutralized, dried and ground to the desired particle size. Various salts with very specific properties are obtained: alkali metal alginates (sodium, potassium, magnesium, etc.) are soluble in water while alginic acid and its calcium derivative (calcium, aluminum, iron, etc.) are soluble in water. ) are practically insoluble. Soluble salts dissolve at low temperatures and form thick, viscous solutions, heat-resistant gels. The invention consists in using all types of alginates, diluted with water and mixed with flammable organic materials from the extractive industry, as a means of combating the fire risks caused by self-heating and risks of dust explosion caused by the particles and microparticles contained in said organic materials as well as by the explosive gases released during the self-heating process, occurring during the storage, transportation or handling of said organic materials. The tests included: - a follow-up of the particle size, the water content and the apparent density of a control stock of treated materials, during a given period, with regard to the temperature monitoring, in order to to guarantee representative external conditions (the control stock representing a mass of about 50 t); an optimization study making it possible to specify the evolution of the percentage of fines and of the bulk density by varying the percentage of the composition tested in a mixture diluted with water, and then by varying the percentage of this mixture, called dosage, in relation to the quantity of materials treated. The monitoring of evolution focused more particularly on: - the water content; - the density ; - the granulometry. With regard to this monitoring, it was found that: - the water content has changed little; the density remains substantially unchanged.

With regard to particle size monitoring, it was found that the fine and very fine particles, below 315 microns, were agglomerated as soon as the tested composition was used, which played the role of wetting agent and fixer. This agglomeration, whose interest primarily concerns fine and very fine particles, has focused: - essentially: on fine and very fine particles with diameters of less than 315 μm, of which the pass of the order of 6% has remained almost unchanged for at least 3 months; - incidentally: on much larger grains, up to the size of 25 mm. Subsequently, it may be indicated that the implementation of the tested composition makes it possible to fix for a long time and over several months the fine particles and very fine sources of dust removal. The optimization study makes it possible to specify the evolution of the percentage of fines as a function of the water dilution rate of the tested composition and the determination of this diluted composition in the material to be treated.

This study, which focused on three water dilution rates of the tested composition, with 3%, 5% and 7%, was carried out, after 3 months, on the 0/5 mm fraction of the treated material. (petroleum coke), the results of which have been corrected to take into account the entirety of the treated material in all its granulometries. The tests have shown that: - the loops at 315 μm and the mixing dosages are proportional and that whatever the dilution rate of the composition. The use of the tested composition has the advantages of: - durably agglomerating the particles and microparticles, which makes it possible to increase the size of the grains as has been demonstrated above; - 12 - - to avoid moisture fixation by condensation, the test composition acting as a wetting agent and fixer by agglomerating the particles and microparticles, thereby avoiding this moisture fixation. According to an alternative embodiment of the invention, diluted alginate will be mixed with black soap (oil + alkaline solution) to increase the wetting properties of the composition. Of course, those skilled in the art will be able to carry out the invention as described and represented by applying and adapting known means. It may also provide other variants without departing from the scope of the invention which is determined by the content of the claims.

Claims (6)

CLAIMS1- Use of all types of alginates diluted with water and mixed with flammable organic materials from the extractive industry, as a means of combating fire risks caused by self-heating and risk of dust explosion caused by the particles and microparticles contained in said organic materials as well as by the explosive gases released during the self-heating process, occurring during the storage, transport or handling of said organic materials. 2- Use of alginates, according to claim 1, diluted with water and mixed with the material to be treated in respective proportions capable of obtaining, for a "index P" passing to 315 microns, a percentage of fines at most equal to 6%. 3- Use of diluted alginates, according to claim 2, with a water dilution ratio of between 2 and 10%. 4- Use of diluted alginates, according to claim 3, with a dosage rate, relative to the material to be treated, of between 3 and 15%. 5- Use of diluted alginates, according to claim 2, 3 or 4, sprayed, misted or atomized by means of adapted ramps located in the area of the successive conveyor belts arranged so as to subject the material to be treated successive turns, with a good homogeneity of the solution of alginates in the materials to be treated. 6. Use of dilute alginates according to claim 2, 3 or 4 for treating materials from the extractive industry selected from petroleum coke, coal, coal coke.