Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D90/00—Component parts, details or accessories for large containers
  • B65D90/48—Arrangements of indicating or measuring devices
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
  • C01B15/055—Peroxyhydrates; Peroxyacids or salts thereof
  • C01B15/10—Peroxyhydrates; Peroxyacids or salts thereof containing carbon

Definitions

• the present invention is related to a process for the monitoring of solids which release oxygen when decomposing and which are stored in a bulk container which is closed to the ambient atmosphere.
• the present invention also relates to the use of this process for the safe storage of such solids and to a bulk 5 container.
• sodium percarbonate decomposes very slowly if stabilized in an appropriate way.
• many efforts have been done by the manufacturers in order to continuously improve sodium percarbonate stability, for instance by coating it with one or more stabilizing coating layers.
• US 6,595,008 discloses a process for the safe storage of sodium percarbonate in bulk containers, in particular in large silos, in which the
• temperature is measured at at least one position inside the sodium percarbonate stored in bulk and for which, with a temperature increase of from 0.5 to 1O 0 C per day, in particular of from 1 to 5 0 C per day, dry air is passed periodically or continuously through the bulk material at least until the increase in temperature has fallen to a value of less than I 0 C per day, in particular less than 0.5 0 C per
• Such fast decompositions can be initiated, for example, by a contamination of the bulk container content by rain ingress into the bulk container, by contamination of a silo-truck during transport, or by contamination of sodium percarbonate during the loading or unloading.
• the silo-truck can for example be contaminated with humidity or with traces of an iron-catalyst in the conveying pipe of the truck.
• the purpose of the present invention is to provide a new process for the monitoring of solids which release oxygen when decomposing, in particular sodium percarbonate, stored in a bulk container, such as a silo, which enables an early detection of slow as well as fast decompositions.
• the present invention therefore relates to a process for the monitoring of solids which release oxygen when decomposing and which are stored in a bulk container closed to the ambient atmosphere, by measuring oxygen level.
• One of the essential features of the present invention resides in the monitoring of the oxygen level instead of monitoring temperature increases, which allows a faster detection of decomposition of the solid stored.
• the part of the bulk container above the stored solid contains a gaseous atmosphere, which is called the headspace.
• the oxygen concentration of the atmosphere in the headspace of the bulk container is measured. Indeed, if decomposition of the stored solid occurs, oxygen will be released and the oxygen concentration in the headspace will increase. The evolution of the oxygen concentration can therefore be linked to the stability of the solid stored. If decomposition occurs in the bulk, an increase of the oxygen concentration is detected and one can empty the bulk container or perform other corrective actions.
• oxygen concentration measurements By monitoring of the oxygen level are intended oxygen concentration measurements, their interpretation and further corrective actions if a predetermined limit is reached or exceeded.
• the oxygen concentration measurements can be done periodically, for instance with a frequency of at least one measurement every 24 hours, in particular every 12 hours, for example every 6 hours.
• the first day after unloading of the truck the oxygen concentration measurements are preferably done at least every 6 hours, more preferably at least every 4 hours.
• the oxygen concentration measurements can also be done continuously. Continuous measurements are recommended.
• Oxygen concentration measurements are generally done using an oxygen detector equipped with sensors having a measuring range of from 0 to 40 Vol% of oxygen, for example of from 0 to 25 Vol% of oxygen.
• the accuracy of such detectors is usually about 0.1%, more generally about 0.5%.
• a gas-purge is passed through the solid stored in the bulk container and is released to the atmosphere through an opening made in a part of the closed bulk container, called the outlet of the bulk container, said opening positioned away from that where the gas-purge is introduced, thereby allowing the gas-purge to escape via a passage through the mass of the solid stored in bulk into the atmosphere and wherein the oxygen concentration of the gas-purge is measured at the outlet of the bulk container. If decomposition of the solid stored in the bulk container occurs, the released oxygen is drawn along by the gas-purge to the oxygen detector where the oxygen concentration is measured. The evolution of the oxygen concentration can therefore be linked to the stability of the stored material.
• the process of the invention is suitable for the monitoring of solids which release oxygen when decomposing.
• solids are notably persalts, metal peroxides and solid percarboxylic acids, mixtures thereof, and formulations containing them.
• Persalts are, for example, sodium percarbonate and sodium perborate monohydrate and tetrahydrate or mixtures thereof.
• Metal peroxides can be alkakine or alkaline earth metal peroxides, such as, calcium, magnesium and zinc peroxides or mixtures thereof.
• An example of solid percarboxylic acids is the N,N'-phthaloylaminoperoxycaproic acid. Formulations containing such solids are for example detergent or bleach booster formulations.
• the inventive process is especially suitable for uncoated sodium percarbonate particles as well as for sodium percarbonate particles coated with one or more coating layers.
• the coating agent can be organic or inorganic.
• Inorganic coating agents can be one or more materials selected from alkaline and/or alkaline earth metal (particularly sodium or magnesium) salts of mineral or other inorganic acids. Typical examples include sulfate, carbonate, bicarbonate, phosphate and/or polymeric phosphates, silicates, borates and the corresponding boric acids.
• Particular combinations of coating agents include - A -
• the inorganic coating agent contains sodium silicate, sodium borate, boric acid, sodium carbonate, sodium sulfate, magnesium sulfate or one of their mixtures.
• the solids which release oxygen when decomposing are generally stored at surrounding temperature, which will usually vary from 10 to 65 0 C.
• the solids are stored at a storage temperature of below 4O 0 C, more preferably below 3O 0 C.
• the solids which release oxygen when decomposing can be stored at surrounding temperature from 10 to 3O 0 C.
• the oxygen concentration measurements are done continuously, for example with a purge of dry air having a velocity of 0,5 m/s across any openings to atmosphere.
• the bulk containers may be stationary or transportable, vertically or horizontally arranged, such as silos and bunkers for bulk material.
• the volume of the bulk containers is usually from 1 to 800 m3, in many cases from 10 to 250 m3.
• the storage containers are vertically standing silos having in most cases a bulk material capacity of from 10 to 250 m3.
• the silo has a maximal diameter of 4 meters, preferably of 3 meters.
• a gas-purge is passed through the bulk container in the process of the invention, it is generally introduced at one side by means of one or more feed devices and, after passage through the stored material, is led away at the opposite side.
• the gas-purge is introduced in the lower region of the bulk container and is led away at the top of the container.
• the bulk container is a vertically standing silo and the gas-purge to be passed through the bulk container is introduced in the lower region of the vertical bulk container and is led away at the top of the container.
• the gas-purge flow is in general at least 10 1/t.h, in particular at least 30 1/t.h, values of at least 50 1/t.h giving good results.
• the gas purge flow is usually at most 2000 1/t.h, in many cases at most 1000 1/t.h, values of at most 500 1/t.h being common. Suitable ranges for the gas-purge flow are from 50 to 2000 1/t.h, preferably from 50 to 500 1/t.h, for example 250 1/t.h.
• the term "1" is an abbreviation for "liter” and means 1 liter of dry air at standard conditions of
• the gas-purge can be passed continuously or periodically through the solid stored in bulk. Continuous gas-purge is recommended.
• the inlet temperature will be of at least 5 0 C, preferably at least 1O 0 C, more preferably at least 15 0 C.
• the inlet temperature of gas-purge will in general be at most 4O 0 C, in particular at most 3O 0 C, more particularly at most 2O 0 C. It is especially advantageous that the temperature of the gas introduced as the gas- purge is in the range from 5 to 30C°.
• the gas constituting the gas-purge can contain an inert gas, such as nitrogen.
• the gas preferably contains dry air. Dry air is intended to mean air whose dew point is below -2O 0 C, preferably below -3O 0 C. Dry air having a dew point temperature in the range from -30 to +1O 0 C, for example from -20 to O 0 C, may also be used, provided that the dew point temperature is below the surrounding temperature to avoid condensation.
• the level of the oxygen concentration is in most cases measured in or near the gas-purge outlet. Assuming a gas-purge of 20 m3/h through a silo filled with 100 tons of percarbonate, an increase of oxygen concentration by 1% would mean an oxygen production of 200 1/h. 200 1 of oxygen are produced from about 2 kg sodium percarbonate. This rough calculation shows that, according to this invention, a 2 kg per hour decomposing sodium percarbonate can be detected.
• the process of the invention can include measuring a temperature at a position inside the solid stored in bulk, passing a periodic or continuous flow of air through the container when a rate of increase of the temperature inside the solid is within a range of 0.5 to 1O 0 C per day, and then discontinuing the flow of air through the container when the rate of increase decreases to less than -0.5 0 C per day.
• This temperature measurement is described in US 6,595,008.
• the process of the invention enables the monitoring of solids which release oxygen when decomposing and which are stored in bulk, detecting very quickly fast decompositions of such solids, even in local spots, which would not have been detected with simple temperature measurements. Indeed, as solids such as sodium percarbonate are good insulators, temperature measurements are not able to detect local fast decompositions.
• the present invention is therefore also related to the use of the process of the invention for the safe storage of solids which release oxygen when decomposing and which are stored in a bulk container closed to the ambient atmosphere.
• the present invention also relates to a bulk container closed to the ambient atmosphere equipped with an oxygen-detector.
• the use of such containers is especially suitable for the storage of solids which release oxygen when decomposing.
• a gas-purge is to be passed through the bulk material, such container is equipped with an inlet and an outlet for the gas-purge.
• the oxygen- detector can then be located in or near the gas-purge outlet.
• FIGS. 1 and 3 describe the test silos used to conduct the experiments described in the examples below.
• Each test silo is composed of a cylindrical length of stainless steel pipe (1) and, below it, a conical air inlet region (2) for gas-purge flow.
• the volume of gas-purge flow through the bulk is controlled by a pressure and flow meter unit (4).
• the stainless steel vessel is insulated by a layer of glass wool with a thickness of 5 cm (3).
• the height of each silo is 120 cm.
• the inside diameter of each silo is 30 cm.
• Each test silo is filled with sodium percarbonate (5), the height of the bulk being 75 cm.
• the part of the test silo above the stored solid contains a gaseous atmosphere and is called the headspace (6).
• each test silo is flanged by a lid (7) fitted with an air outlet (8).
• Each test silo is fixed in a mobile carrier (9) for transport reasons.
• Plastic cross stripes with drilled holes are fixed at defined positions (10) in each test silo.
• the star marks (11) in the bulk represent any local contamination exemplarily.
• Figure 1 shows that the oxygen concentration is monitored by means of an oxygen detector X-am 7000 from DRAEGER.
• the detector is fitted with XS R 02 LS sensor with a measuring range from 0 to 25 Vol% O 2 (12) located in the headspace (6).
• Figure 2 shows the curve illustrating the oxygen concentration (Vol%) of the air-purge at the outlet of the silo.
• Figure 3 shows that the temperatures at different levels of the silo are monitored by means of four centered temperature probes of Type K (NiCrNi): a first one (13) in the air inlet region (2), a second one (14) reaching the first third of the bulk silo at a height of 40 cm, a third one (15) reaching the center of the bulk silo at a height of 60 cm, and a fourth one (16) in the headspace (6) of the test silo at a height of 105 cm.
• the temperature probes in the bulk are fixed in the plastic cross stripes with drilled holes at defined positions (10).
• the temperature data are collected by data logger device (17).
• Figure 4 shows the local temperatures ( 0 C) measured at four different points of the silo.
• Curve 2 shows temperature measurement done by the temperature probe (14), located at a height of 40 cm in the test silo.
• Curve 3 shows temperature measurement done by the temperature probe (15), located at a height of 60 cm in the test silo.
• Curve 4 shows temperature measurement done by the temperature probe (16) located in the headspace (6) of the test silo.
• Curve 5 shows temperature measurement done by the temperature probe (13), located in the air inlet region (2) of the test silo.
• a comparative example was conducted in the experimental silo described in Figure 3, in which 54 kg of sodium percarbonate were loaded.
• the temperature inlet of the gas was 12°C.

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• 2006
  • 2006-07-26 EP EP06117847A patent/EP1884494A1/de not_active Ceased
• 2007
  • 2007-07-24 EP EP07787857A patent/EP2059478A1/de not_active Withdrawn
  • 2007-07-24 WO PCT/EP2007/057624 patent/WO2008012311A1/en active Application Filing
• 2009
  • 2009-01-22 EG EG2009010102A patent/EG25144A/xx active

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