Treatment system and method for sanitizing a granular material

Abstract

A Treatment system (1) for sanitizing a granular material, comprising a processing vessel (2) having a processing chamber (3), supply means (4) for supplying said granular material into said processing chamber (3), and an ozone supply (5) coupled to said processing chamber (3). Said processing vessel (2) comprises agitation means (7) inside said processing chamber (3) intended and configured for moving around said granular material within said processing chamber (3). Said processing vessel (2) has a maximum fill level (31) below a volume of said processing chamber (3). A central control unit (8) is provided for actuating said agitation means (7) in a presence of a supply of ozone gas within said processing chamber (3).

Description

[0001]Treatment system and method for sanitizing a granular material The present invention relates to a treatment system for sanitizing a granular material, comprising a processing vessel having a processing chamber, supply means for supplying said granular material into said processing chamber, and an ozone supply coupled to said processing chamber. The invention moreover relates to a method for sanitizing a granular material. Such treatment system and method are disclosed in International patent application WO 2023 / 017496 by applicant. The treatment system and method that are known from that publication comprise a substantially cylindrical vertical silo. The granular organic material is delivered at a top of the silo and may be collected at an outlet at the bottom. At least one rotating ozone injector is disposed along a diameter of the silo traversing the trajectory of the material on its way down in order to introduce ozone gas into the material. Biological micro-organisms, such as bacteria, viruses, fungi, particularly yeast and mould, mycotoxins as well as larvae and small insects, that may contaminate the material, may be killed upon adequate exposure to ozone gas. A disadvantage of the known method and system, however, is that the material is exposed to ozone only momentarily when it falls down in the silo. As a consequence relatively high levels are ozone are needed to sanitize the material sufficiently. It is an aim of the present invention to provide a treatment system and method for sanitizing a granular material with the aid of ozone gas that uses said ozone gas more efficiently. To that end, a treatment system for sanitizing a granular material of the type as described in the opening paragraph, according to the present invention is characterized in that said processing vessel comprises agitation means inside said processing chamber intended and configured for turning around said granular material within said processing chamber, in that said processing vessel has a maximum fill level below a volume of said processing chamber, in that a central control unit is provided for actuating said agitation means in a presence of a supply of ozone gas within said processing chamber, and in that said processing vessel comprises a heat sensor for recording an internal temperature inside said processing chamber, said heat sensor being coupled to said central control unit. It has been found that moving around the material while in an ozone atmosphere inside the processing vessel with a surplus of internal volume, creates an improved contact between the material and said ozone gas such that said material may be sanitized adequately and only little ozone gas is needed to satisfactory disinfect the material. Further It has been found that during the exposure to ozone the internal temperature of the material rises as a result of the heat that is released due to the reaction between the material and ozone. This increase in temperature may be as a guide to observe whether the reaction is happening and how aggressively it is progressing. To that end, said processing vessel comprises a heat sensor for recording an internal temperature inside said processing chamber, said heat sensor being coupled to said central control unit. The latter embodiment of the system is particularly well suited for performing a method of sanitizing a granular material, which according to the invention tis characterized in that said material is brought into contact with ozone while being agitated, in that said material is moisturized to a moisture level of at least 1 wt%, in particular at least 15 wt%, and more particularly between 18 and 22 wt%, and in that an internal temperature of said granular material is monitored, wherein said treatment is finished at a predetermined increment of said internal temperature. More particularly, it has been found that the method may be kept under control when according to the invention, the method is characterized in that said treatment is operated to allow said internal temperature of said material increasing at a rate of between 1 and 2 degrees Celsius per minute. It has been found that the material may be disinfected adequately this way if the treatment is performed for at least 3 minutes. A preferred embodiment of the treatment system, according to the invention, is characterized in that said processing chamber is provided with moisturizing means that are capable and configured to increase a moisture level of said granular material. Moisturizing the material before or concurrent to the treatment with ozone allows ozone to dissolve into the moist material. Not only will this extend a retention time of contact between ozone and the material, it may moreover increase a penetration depth of ozone into the material. Both factors appear to have a beneficial effect on the effective removal of contaminants. In line with the preceding recognition, a method for sanitizing a granular material, as mentioned in the opening paragraph, according to the invention is characterized in said material is brought into contact with ozone while being agitated and in that said material is moisturized to a moisture level of at least 1 wt%, in particular at least 15 wt%, and more particularly between 18 and 22 wt%. In a particular embodiment, said method is thereby characterized in that said moisture level of said material is adjusted prior to being brought into contact with ozone, particularly by adding at least 1 wt%, in particular at least 5 wt%, and more particularly between 8 and 10 wt%, moisture. In a further particular embodiment the method according to the invention is characterized in that said moisture level of said material is adjusted while being in contact with ozone, particularly by adding at least 1 wt%, in particular at least 5 wt%, and more particularly between 8 and 10 wt%, moisture. In practice, the material may be moisturized with water, water vapour or other liquids. To that end, a particular embodiment of the treatment system according to the invention is characterized in that said moisturizing means comprise a liquid source, particularly water or water vapour, that is connected to at least one spray nozzle opening into said processing chamber. In order to allow the material to be in contact with ozone all around it is important that the processing vessel has an internal volume exceeding that of the fill level of the material. In this respect it has been found that proper results are achieved with a specific embodiment of the treatment system according to the invention that is characterized in that said maximum fill level is less than 80%, particularly less than 70% and more particularly below 50% of said volume of said processing chamber. The vessel has agitation mechanisms with enough power and room to move the mass around and create a larger contact surface. According to this embodiment, the vessel has always between 80% to 20% of space left to allow the movement of the feed and the action of the ozone gas. A particularly practical setup of the treatment system is provided by a further embodiment that is, according to the invention, characterized in that said processing chamber is substantially cylindrical along a cylinder axis, and in that said agitation means comprise at least one rudder member traversing said processing chamber, wherein said at least one rudder member is connected to a drive shaft that extends along said cylindrical axis of said processing chamber and is suspended for rotation. The vessel may be suspended horizontally, vertically or inclined to the force of gravity. Preferably the vessel is held practically horizontal in this respect for an optimal fluffy agitation of the mass inside. Ozone gas may be supplied to the material prior or after introduction into the vessel. With a view to such post ozone injection, a further embodiment of the treatment system according to the invention is characterized in that said processing vessel comprises an inlet connection coupled to at least one ozone injector opening into said processing chamber, said inlet connection connecting said at least one ozone injector to said supply of ozone. A preferred embodiment of the treatment system, in this respect, is according to the invention characterized in that said inlet connection is provide with flow control means, particularly a flow control valve, controlled by said central control unit. The flow control valve allows precisely regulating the amount of ozone gas that is being introduced into the processing chamber. In this respect, a further embodiment of the method according to the inventions is characterized in that said material is treated with at least 0,1 gram ozone per kilogram material, in particular between 2 and 5 gram ozone per kilogram material. Disinfecting granular material for consumption with ozone is particularly beneficial since it does not alter the composition of the material or pose a hazard to a consumer. To that end, a further embodiment of the method according to the invention is characterized in that said granular material is organic material, particularly animal feed. The method according to the invention may be carried out in batches or continuously. In either case, the supply means may comprise a product inlet opening into said processing chamber. Hereinafter, the invention will be described in further detail with reference to a specific embodiment and an accompanying drawing. In the drawing: Figure 1 a specific example of a treatment system according to the invention; Figure 2 shows a sectional view of a vessel as used in the treatment system of figure 1; Figure 3 shows a graph of changes in temperature during performance of a method of sanitizing a granular material according to the invention. It is noted that the figures are drawn purely schematically and not necessarily to a same scale. In particular, certain dimensions may have been exaggerated to a more or lesser extent to aid the clarity of any features. Similar parts are generally indicated by a same reference numeral throughout the figures. A treatment system and method for disinfecting a granular material from micro- organisms is described herein. In this embodiment the system is used to process animal feed. Typical ingredients are for example grains and seeds. In an initial stage these ingredients may be grinded and / or thoroughly mixed with one another. The optionally mixed organic material is conveyed to a treatment system 1, as shown in figure 1, where the organic material is to be disinfected. The treatment system 1, as shown in figure 1, comprises a processing vessel 2 having a processing chamber 3, a supply means 4 supplying granular material to the processing chamber 3 and an ozone supply 5 coupled to the processing chamber 3. The supply means 4 supply the processing chamber 3 with material. The supply means 4, in this embodiment, comprises a supply line 42 connecting a mill 41 to the vessel 2. The supply line 42 has a product outlet 43, shown in figure 2, opening into the processing chamber 3 via an inlet 21. In alternative embodiments instead of, or in addition to the mill 41, a silo or a delivery tank may be provided. As shown in figure 2, the vessel 2 is a generally cylindrical body with an upper end 24 and a lower end 25. The vessel 2 is manufactured from an ozone proof material, for example, stainless steel and has, in this example, a loading capacity of 8000 litres. The vessel 2 may be suspended horizontally, vertically or inclined to the force of gravity. In this embodiment, the vessel 2 is held operatively horizontally to allow for an optimal agitation of material inside. Granular material to be disinfected is conveyed from the mill 41 via the supply line 42 through the inlet 21 into the processing chamber 3. The processing chamber 3 is provided in an available interior space of the vessel 2 and is substantially cylindrical along a central axis of the vessel 2. The inlet 21 into said processing chamber 3 extends through the upper end 24 of the vessel 2 and an outlet 22 from said processing chamber extends through the lower end 25 of the vessel 2. The inlet 21 may be located anywhere at an upper region of the vessel 2 and the outlet may be located elsewhere towards the lower end 25. The outlet 22 has an operable closure 29, in particular a sliding gate valve, whereby flow of material from the processing chamber 3 can be controlled by a central control unit 8. To disinfect the material, ozone may be supplied to the processing chamber 3 before and / or after introducing the material in the processing chamber 3. To allow for supplying ozone to the material in the processing chamber 3 the vessel 2 comprises an inlet connection 28 which is coupled to an ozone injector 26. The ozone injector 26 opens into the processing chamber 3. Accordingly, ozone can be supplied to the processing chamber 3 through the ozone injector 26. The amount of ozone introduced is dependent on the weight of the material. In particular, between 2 and 5 grams of ozone is introduced for every kilogram of material in the processing chamber 3. To that end the inlet connection 28 has a flow control means and, in particular, a flow control valve 27. The flow control valve 27 allows for precisely regulating an amount of ozone supplied to the processing chamber 3. With the flow control valve 27 ozone supply is regulated to between 2 and 5 grams of ozone per kilogram of material in the processing chamber 3. The flow control valve 27 is remote operable by the central control unit 8. The amount of ozone introduced may also be dependant on a density and granulometry of the granular material. To supply ozone gas to the processing chamber 3 an ozone supply 5 is coupled to the ozone injector 26 via the inlet connection 28. Multiple ozone injectors 26 may be provided depending on the size of the processing chamber 3. In this embodiment the ozone supply 5 comprises an ozone generator and an oxygen source connected to the ozone generator. The oxygen source may supply the ozone generator with liquid oxygen from which ozone can be generated. Ozone entering the processing chamber 3 provides for an increase of an internal pressure of the precessing chamber which. Should this internal pressure be too high, damage may be caused to the vessel 2. To reduce an internal pressure in the processing chamber 3, the processing chamber 3 has an exhaust 100 through which excess ozone in the processing chamber 3 can escape. The exhaust 100 has a valve 102 which prevents air from entering the processing chamber 3 through the exhaust 100 whilst allowing ozone to exit. An ozone sensor 101 in the exhaust 100 measures a concentration of ozone exiting the processing chamber. A measurement of the ozone concentration is used as a guide of the reaction between ozone and the material. To convert ozone escaping the exhaust 100 back into oxygen, an ozone destructor 103 is provided in the exhaust 100. Accordingly oxygen is released back into the environment. To provide for optimal contact between the ozone and material, the processing chamber 3 comprises agitation means 7, in particular a plough mixer, that are positioned in the processing chamber 3. In this example, the agitation means 7 comprise a rudder 71 attached to a drive shaft 72 with the rudder 71 traversing the processing chamber 3. In this example the rudder 71 comprises a number of fins projecting from the shaft 72. The shaft 72 is suspended centrally in the processing chamber 3. A power source, not shown, is coupled to the shaft 72 to power the shaft 72 for rotation thereof. The power source is an electromotor that is controlled by the control unit 8. The agitation means 7 has enough power and space to move material around in the processing chamber 3 whilst creating a large contact surface between the material and the ozone atmosphere. The central control unit 8 is provided to control operation of the agitation means 7. The control unit 8 may be remote from the vessel 2, as shown in figure 1, or may be directly secured thereto. The control unit 8 comprises a housing 84 containing a power source 46, particularly an electric supply means, and a processing means 81. Shown in figure 1, accessible from an outside of the housing 84 is a control panel 85, which includes a display screen. Agitating the granular material in the ozone atmosphere of the processing chamber 3 in a surplus of internal volume creates an optimal contact between the material and the ozone gas. To allow for such surplus volume the processing chamber 3 has a maximum fill level 31, as shown in figure 2, which is at least 20% below an internal volume of the precessing chamber 3. An actual fill level is kept below said maximum fill level 31 for an optimal operation. In this case, said actual fill level is 50% of the internal volume of the processing chamber 3. This allows the processing chamber to have more than 20% free space left for movement of the material and reaction of the ozone with the material. In order to control the amount of material introduced into the processing chamber 3, and thereby ensuring that the maximum fill level 31 is not exceeded, the material is introduced by means of a weight control. To that end the vessel 2 is suspended on a load cell 10. The load cell 10 allows for weighing organic material in the processing chamber 3 and thereby monitoring the amount of organic material in the processing chamber 3. The weight of the material serves as a guide of a volume of the processing chamber 3 occupied by the material. As material enters the processing chamber 3 the vessel 2 is weighed by the load cell 10 to determine the weight of the material and, accordingly, monitor that the maximum fill level 31 is not exceeded. For example, depending on the granular material, a weight of approximately 5000kg of material corresponds to approximately 60% of the volume of the processing chamber 3. To enhance the action of ozone, the material is moisturized before or concurrently with being treated with ozone to allow the ozone to dissolve into and penetrate the moist material. The material is moisturized to a moisture level of at least 1 wt%, in particular at least 15 wt%, and more particularly between 18 and 22 wt%. The moisture level is adjusted by adding at least 1 wt%, in particular at least 5 wt%, and more particularly between 8 and 10 wt%, moisture to the material. Particularly water or steam is used to moisture the material. The increase of moisture extends a retention time of contact between ozone and the material as well as increases a penetration depth of ozone into the material. Both these factors are effective for removal of micro-organisms from the material. To introduce said moisture in the processing chamber 3, the processing chamber 3 has a series of spray nozzles 33 in the upper end 24 of the vessel 2 with an opening of the spray nozzle 33 directed towards the lower region of the precessing chamber 3. Each of the spray nozzles 33 is accessible from outside the vessel 2 to allow for ease of removal and cleaning thereof. The spray nozzles 33 are operated by means of the control unit 8. Shown in figure 2 a moisturizing means 9 is connected to the spray nozzles 33. The moisturizing means 9 comprises a tank 91, in particular a water tank, with a hose 92 connecting the water tank 91 to the spray nozzles 33. The moisturizing means 9 is provided with a water filter and a remote controllable flow valve with which flow from the water tank 91 to the spray nozzles 33 can be controlled. The water filter allows for filtering the liquid prior to it being supplied to the processing chamber. As a result of an exothermic reaction between material and ozone in the processing chamber 3, an internal temperature of the processing chamber 3 may rise. This increase of temperature may serve as a guide to observe whether the reaction is occurring and how aggressively. To monitor the internal temperature, a heat sensor 34 is provided in the processing chamber 3. The heat sensor 34 is suspended from the upper end 24 of the vessel 2 up to substantially above the maximum fill level 31 so that material being agitated in the processing chamber 3 will not reach the heat sensor 34. A further heat sensor 34' is secure to a lower part of the processing chamber 3 where it will be in contact with agitated granular material. The further heat sensor 34' measures a temperature of the agitated material itself. It is envisaged that the temperature of the agitated material may be a few degrees, in particular approximately 2 degrees Celsius, higher than that of the temperature measured by the temperature sensor 34. The heat sensors 34, 34' are connected to the control unit 8 that monitors the internal temperatures. Figure 3 shows a graph of the internal temperature D of the processing chamber during the course of the treatment. The temperature is indicated in degrees Celsius on the y- axis, while time, indicated in minutes, is indicated on the x-axis of the graph. The reference numerals of the internal temperature D indicate the following stages during the treatment: 200 - supplying granular material to the processing chamber 3 and starting agitation; 201 - adding moisture to the processing chamber 3; 202 - ozone injection in the processing chamber 3 is started; 203 - ozone generation is increased; 204 - ozone reacts with the material; 205 - the treatment is ended; and 206 - the material is discharged from the processing chamber 3. As can be seen in figure 3, an exponential increase in the internal temperature D occurs during the ozone treatment 204 of the material. The exponential change in temperature indicates an effective reaction of ozone with the material, whereby the material is disinfected from micro-organisms. The longer the ozone treatment 204 is performed, the more the internal temperature D rises until a predetermined temperature D is reached. The predetermined temperature serves as a guide that the material has been satisfactory disinfected. In this case the maximum predetermined internal temperature D has been reached after approximately 8 minutes of ozone treatment. The ozone treatment process is stopped and the material discharged from the processing chamber 3. To further process disinfected material, a pellet making machine 11 may be connected to the outlet 22 of the vessel 2, as shown in figure 1. Disinfected material discharged from the processing chamber 3 may accordingly be supplied to the pellet making machine 11 where it can be converted into pellets. In particular, the pellet making machine 11 will, inter alia, supply steam to the material to moisturise the material. The moisturized material will thereafter be compacted into desired forms and sizes as required for the pellets. It is envisaged that the invention herein described is desirable to use as it allows for efficiently using ozone to disinfect granular material, in particular animal feed. With agitation of the material whilst injecting ozone into the processing chamber an increased contact between the material and the ozone is created. This provides for optimal use of ozone to disinfect material. Accordingly, less ozone may be required to disinfect the material than would have been required for a treatment system having no agitation means. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. For example, instead of the inlet connection 28 having a flow control means, a flow control means may be installed at any point between the ozone generator and the inlet connection. Furthermore, the oxygen generator may be connected to any suitable oxygen source, for example, an oxygen bottle.

Claims

Claims:

1. Treatment system (1) for sanitizing a granular material, comprising: - a processing vessel (2) having a processing chamber (3); - supply means (4) for supplying said granular material into said processing chamber (3); and - an ozone supply (5) coupled to said processing chamber (3); characterized in that said processing vessel (2) comprises agitation means (7) inside said processing chamber (3) intended and configured for moving around said granular material within said processing chamber (3); in that said processing vessel (2) has a maximum fill level (31) below a volume of said processing chamber (3); in that a central control unit (8) is provided for actuating said agitation means (7) in a presence of a supply of ozone gas within said processing chamber (3); and in that said processing vessel (2) comprises a heat sensor (34) for recording an internal temperature inside said processing chamber (3), said heat sensor (34) being coupled to said central control unit (8).

2. Treatment system according to claim 1, characterized in that said processing chamber (3) is provided with moisturizing means that are capable and configured to increase a moisture level of said granular material.

3. Treatment system according to claim 2, characterized in that said moisturizing means (9) comprise a liquid source (91), particularly water or water vapour, that is connected to at least one spray nozzle (33) opening into said processing chamber (3).

4. Treatment system according to anyone of the preceding claims, characterized in that said maximum fill level (31) is less than 80%, particularly less that 70% and more particularly below 50% of said volume of said processing chamber (3).

5. Treatment system according to anyone of the preceding claims, characterized in that said processing chamber (3) is substantially cylindrical along a cylinder axis, and in that said agitation means (7) comprise at least one rudder member (71) traversing said processing chamber (3), wherein said at least one rudder member (71) is connected to a drive shaft (72) that extends along said cylinder axis of said processing chamber and is suspended for rotation.

6. Treatment system according to anyone of the preceding claims, characterized in that said processing vessel (2) comprises an inlet connection (28) coupled to at least one ozone injector (26) opening into said processing chamber (3), and said inlet connection (28) connecting said at least one ozone injector (26) to said supply of ozone (5).

7. Treatment system according to claim 6, characterized in that said inlet connection (28) is provided with flow control means (27), particularly a flow control valve, controlled by said central control unit (8).

8. Treatment system according to anyone of the preceding claims, characterized in that said supply means (4) comprise a product inlet (43) opening into said processing chamber (3).

9. Treatment system according to anyone of the preceding claims, characterized in that said granular material is organic material, particularly animal feed.

10. Method of sanitizing a granular material, characterized in said material is brought into contact with ozone while being agitated and in that said material is moisturized to a moisture level of at least 1 wt%, in particular at least 15 wt%, and more particularly between 18 and 22 wt%, and in that an internal temperature of said granular material is monitored, wherein said treatment is finished at a predetermined increment of said internal temperature.

11. Method according to claim 10, wherein said treatment is operated to allow said internal temperature of said material increasing at a rate of between 1 and 2 degrees Celsius per minute.

12. Method according to claim 11, wherein said treatment is performed for at least 3 minutes.

13. Method according to anyone of claims 10 to 12, wherein said moisture level of said material is adjusted prior to being brought into contact with ozone, particularly by adding at least 1 wt%, in particular at least 5 wt%, and more particularly between 8 and 10 wt%, moisture.

14. Method according to anyone of claims 10 to 13, wherein said moisture level of said material is adjusted while being in contact with ozone, particularly by adding at least 1 wt%, in particular at least 5 wt%, and more particularly between 8 and 10 wt%, moisture.

15. Method according to anyone of claims 10 to 14, wherein said material is treated with at least 0,1 gram ozone per kilogram material, in particular between 2 and 5 gram ozone per kilogram material.

16. Method according to anyone of claims 10 to 15, characterized in that said granular material is organic material, particularly animal feed.

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