METHOD AND APPARATUS FOR THE CONTINUOUS PROCESSING OF DEAD ANIMAL MATERIAL, SUCH AS OFFAL

Abstract: Dead animal material, such a offal, is in subsequent steps and in a continuous manner comminuted in a comminuter (3), plumped to a pre-heating/sterilization installation by a pump (4), heated to the sterilization temperature in a number of successive tubular heat exchangers (5, 6, 7) and, for some time, kept at the sterilization temperature in a long tube (14), reduced in pressure in a sluice system (9) fed through a cyclone (10) and finally further processed to the desired and product. The heat exchangers (5, 6, 7) and the tube (14) are connected to one another to a long closed tube through which the material flows in a plug flow. Vapours set free in the cyclone (10) are used for the first pre-heating of the material.

Description: The invention relates to an apparatus and method for the processing of dead animal material, such as offal. Dead animal material, such as entrails and bones with residues of organic material, for example from slaughterhouses, but also complete carcasses are converted in an offal processing installation into mainly fat and meat bonemeal. The offal largely consists of water. The bulk of this has to be removed. In addition, the requirement is that the dead animal material is subjected to a heat treatment. DE-A-1 617 002 discloses an apparatus for the processing of dead animal material, such as offal, comprising means for comminuting the material, an installation for subjecting the comminuted material to a heat treatment, and means for transporting the material through the heat treatment installation. In this known apparatus the installation for subjecting the comminuted material to a heat treatment comprises a number of interconnected vessels in which the material is boiled in a number of successive steps. A stirrer consisting of a stirrer shaft and arms fixed to the shaft is disposed in each of the vessels for keeping the material in the vessel in motion. The apparatus is designed to work at atmospheric pressure. The known apparatus has the disadvantage that the vessels have blind angles so that additional stirrers are needed for keeping the material in the vessels in motion. The shafts of the stirrers extend through the wall of the vessels. This makes the apparatus relatively complicated and not suitable to work under high pressure which is necessary for a sterilization treatment of the material. The object of the invention is to provide an apparatus which does not present the abovementioned disadvantage. This object is achieved by an apparatus of the type disclosed in DE-A-1 617 002 which is characterised in that the heat treatment installation is a pre-heating and sterilization installation comprising a relatively long, substantially continuous tube having sections which are part of at least one heat exchanger, in which the material can be pre-heated to the sterilization temperature, and of a tubular sterilizer, in which the material can be kept at the sterilization temperature for a certain time period, in that the transporting means comprise a pump located between the comminuting means and the pre-heating and sterilization installation, at the beginning of the continuous tube, the pump being equipped to pump the comminuted material into the continuous tube under elevated pressure, and in that at the end of the continuous tube, downstream of the sterilizer, means are provided for lowering the pressure on the sterilized material. The apparatus according to the invention is relatively simple and suitable for sterilizing dead animal material, such as offal. The sterilization process can be very well controlled. FR-A-1.486.467 discloses an apparatus for the pre-heating, sterilization and cooling of meat in a continuous process. This apparatus also comprises a number of vessels, a stirrer being disposed in each of the vessels. The apparatus is therefore relatively complicated. Moreover, the maximum working pressure cannot be very high. The invention also relates to a method for the processing of dead animal material, such as offal, wherein in a continuous process the material is comminuted and directly thereafter subjected to a heat-treatment in a number of successive steps, which is characterised in that the dead animal material, after being comminuted is brought under elevated pressure and pumped into a relatively long substantially continuous tube in which the material is sterilized by pre-heating it to the sterilization temperature and keeping it at the sterilization temperature for a certain time period, while the material is transported through the continuous tube in a plug flow, and the pressure on the material is lowered after sterilization. Preferred embodiments of the apparatus and method according to the invention are specified in the subsidiary claims. The invention will now be illustrated in more detail by means of the description of an embodiment example with reference to the appended drawing. The single drawing shows schematically an apparatus according to the invention. The part of the apparatus according to the invention shown in the drawing comprised the following components: a storage vessel 1 for the raw material, a transport installation 2, a comminuter 3, a pump 4, a first heat exchanger 5, a second heat exchanger 6, a third heat exchanger 7, a sterilizer 8, a sluice system 9 and a cyclone 10. When offal is processed in the apparatus, the offal is fed from the storage vessel 1 and via the transport installation 2 to a known comminuter which comminutes the offal to particles with a maximum dimension of about 3 cm. The comminuted material is then fed with the aid of a pump 4 to a pre-heating/sterilization system which consists of a long, closed, stainless-steel tube through which the mixture flows in a plug flow. This tube is part of the heat exchangers 5, 6 and 7 and the sterilizer 8. It is important that a good pump is used which is capable of feeding the material through the pre-heating/sterilization system under a sufficiently high pressure and at the correct throughput. In the first heat exchanger 5, the material is heated from a temperature of about 15°C to a temperature of about 55°C. In the second heat exchanger the material is heated from about 55°C to about 80°C and in the third heat exchanger from about 80°C to about 140°C, which is somewhat above the required sterilization temperature. The final heat exchanger 7 is heated by steam under a pressure of at most 10 bar, which is fed in at 11, by which means it is ensured that the material to be processed reaches a temperature of 140°C. In order to prevent the material baking onto the tube wall in the heat exchanger 7, it can be necessary to stir the material in the heat exchanger 7 with an agitator. In this case, the tube must have a diameter such that an agitator can rotate therein. The second heat exchanger 6 is heated by the steam condensate originating from the heat exchanger 7 (via line 12) and from the drier in the second part of the installation. The condensate if drawn off at 13, from where it is recycled to the boiler. The first heat exchanger 5 is heated by using the vapours set free (via line 16) from the cyclone 10, which will be described in more detail below, and from the drier in the second part of the apparatus, which vapours are fed in at 18. The vapour condensate is removed at 19. Depending on the quantity of available waste vapours, the heat exchangers 5 and 6 can be combined to form a single heat exchanger and heating to 80° by steam condensate is dispensed with. The pre-heated material, which leaves the third heat exchanger 7 at a temperature of 140°C, is fed to the sterilizer 8, which consists of a relatively long tube 14. This tube is provided with a good heat-insulating jacket. If desired, a section 15, 15′ of the tube can be designed as a heat exchanger heated by steam, so that local additional heating of the material flowing through is possible. By the correct choice of the length and the diameter of the tube and control of the throughput speed and the inlet and outlet temperature of the material, it can be ensured that the material is sterilized in such a way that the specified sterilization requirements, for example the requirement that the material is kept at 133°C for 20 minutes, are met. It is also possible to heat the material in the installation wholly or partly by the direct injection of steam or vapour into the material. If this is done in the sterilizer, the injected steam must, of course, be sterile. Downstream of the sterilizer 8, the material under pressure is fed via a sluice system 9 provided with a pressure regulator to a cyclone 10, in which the material is "flashed down" to a temperature of about 100°C. During this operation a quantity of vapour is released which is fed via line 16 to the first heat exchanger 5. Under the above operating conditions, approximately 10% of the water present in the material will vaporize in the cyclone. Heating of the heat exchanger 5 with the vapours originating from the cyclone contributes to an achievable energy saving of 113 kg of steam on the total 210 kg of steam necessary for heating and sterilizing one tonne of material. The total electrical energy to be supplied is about 16.5 kWh per tonne of material. It is noted that the vapours emerging from the cyclone 10 are sterilized and that the vapour condensate removed at 19 is also sterile. From the cyclone 10, the material is fed, at 17, for further processing (drying and separating into fat and meat bonemeal) to the second part of the apparatus not shown here and known per se. A modified two-cylinder section pump with hydraulic drive is very suitable as the pump 4. A pump of this type is known per se. It is important in this connection that the material to be pumped is fed to the pump cylinders by means of a screw feed. The heat exchangers 5, 6 and 7 are preferably designed as tubular heat exchangers, the tube through which the material flows being incorporated in a larger vessel. Heat exchangers of this type are also referred to a "shell and tube" heat exchangers. The sluice system 9 can be designed with ball valves which are controlled pneumatically or hydraulically, such that the correct pressure is maintained in the system located upstream. The sluice system 9 also contains a measurement and control system in order to maintain the desired system pressure, capacity and temperature. The sluice system 9 can also be designed with so-called swivel tubes. A swivel tube consists of a curved tube section, of which the two end portions are parallel to one another and which is rotatable about an axis coincident with the centre line of one of the end portions. The end portion of the rotatable tube section of which the centre line coincides with the axis of rotation is in general connected to a tube in a rotatable manner. The other end portion of the tube section, which can be swivelled about the axis of rotation, connects sealingly with a plate provided with a hole, the so-called rest plate. This end of the tube section can move over the plate during the rotation of the tube section and be positioned opposite the hole in the plate or opposite a closed section of the plate, by which means a passage is or is not produced and transport through the swivel tube thus can or cannot take place. In a specific embodiment of the installation according to the invention which is suitable for the processing of 10 tonnes of offal per hour, the tube through which the material is transported has a diameter of 150 mm in the pre-heating section and a diameter of about 300 mm in the sterilizer 8. A diameter which varies over the length of the sterilization tube can be chosen, such that the material is kept in a homogeneous condition. This is particularly important in horizontal sections. The heating surface of the first, 5, the second, 6, and third, 7, heat exchanger is 65, 65 and 75 m² respectively. The length of the tube in the sterilizer 8 is 70 m. The pressure of the material to be processed is approximately 25 to 30 bar at the inlet to the first heat exchanger at 17, and the pressure downstream of the sluice system 9 is about 3 1/2 bar, in order to prevent evaporation in the system and the maintain the temperature at a minimum of 133°C. The different temperatures of the material to be processed are indicated in the drawing. The pump 4 has a maximum capacity of 15 m³/hour under a compressive pressure of 40 bar. The transport cylinders have a diameter of 110 mm and the piston stroke length is 1000 mm.

Claims: Apparatus for the processing of dead animal material, such as offal, comprising means (3) for comminuting the material, an installation (5-8) for subjecting the comminuted material to a heat treatment, and means (4) for transporting the material through the heat treatment installation, characterised in that the heat treatment installation is a pre-heating and sterilization installation comprising a relatively long, substantially continuous tube having sections which are part of at least one heat exchanger (5, 6, 7), in which the material can be pre-heated to the sterilization temperature, and of a tubular sterilizer (8), in which the material can be kept at the sterilization temperature for a certain time period, in that the transporting means (4) comprise a pump (4) located between the comminuting means (3) and the pre-heating and sterilization installation, at the beginning of the continuous tube, the pump (4) being equipped to pump the comminuted material into the continuous tube under elevated pressure, and in that at the end of the continuous tube, downstream of the sterilizer, means (9, 10) are provided for lowering the pressure on the sterilized material. Apparatus according to claim 1, characterised in that the means (9, 10) for lowering the pressure on the sterilized material comprise a sluice system (9) and a cyclone (10) located downstream of the sluice system (9). Apparatus according to claim 1 or 2, characterised in that the pre-heating and sterilization installation comprises at least a first heat exchanger (5) and a last heat exchanger (7) in which the comminuted material is pre-heated in successive steps. Apparatus according to claim 3, characterised in that the cyclone (10) is connected to the first heat exchanger (5), such that vapours set free in the cyclone (10) can be used in the first heat exchanger (5) as heating medium. Apparatus according to claim 3 or 4, characterised in that at least the final heat exchanger (7) is connected to a steam supply (11). Apparatus according to one of claims 3 to 5, characterised in that the final heat exchanger (7) is provided with devices for agitating material flowing through this heat exchanger. Apparatus according to one of claims 1 to 6, characterised in that at least part of the section of the continuous tube of the sterilizer (8) is provided with an insulating jacket or is part of a heat exchanger to which steam can be supplied. Apparatus according to one of claims 1 to 7, characterised in that the pump (4) is a modified two-cylinder piston pump with hydraulic drive. Apparatus according to one of claims 1 to 8, characterised in that the sluice system (9) is designed with ball valves or swivel tubes and comprises a measurement and regulating system. Method for the processing of dead animal material, such as offal, wherein in a continuous process the material is comminuted and directly thereafter subjected to a heat-treatment in a number of successive steps, characterised in that the dead animal material, after being comminuted is brought under elevated pressure and pumped into a relatively long substantially continuous tube in which the material is sterilized by pre-heating it to the sterilization temperature and keeping it at the sterilization temperature for a certain time period, while the material is transported through the continuous tube in a plug flow, and the pressure on the material is lowered after sterilization. Method according to claim 10, characterised in that in a first pre-heating step the material is heated with vapour which is set free on lowering the pressure after sterilization. Method according to claim 10 or 11, characterised in that the final pre-heating step the material is heated by steam. Method according to one of claims 10 to 12, characterised in that the material is wholly or partially heated by injecting steam or vapour directly into the material.

Inventors: WALRAVEN, OSCAR EDWIN DEODATUS
Applicants: STORK PMT B.V.
Application year: 1989
Main classification: A23B4
IPC codes: A23K1, A23L3, A23B4