GB2150846A - Apparatus for mixing particulate material having a preheating device for material to be mixed - Google Patents

Abstract

Granular plastics material to be mixed as fed from a storage container (1) through a supply pipe (3) to a mixing container (4) which operates at such a speed as to heat the mixture. The resulting mixture is fed to a further mixing container (5) where it is cooled by cooling water in a water jacket (6). The water is fed in a cold water circuit (7) to a heat pump (2) which produces hot water in circuit (8) to preheat the material to be mixed by means of a heat exchanger (9) in association with the supply pipe (3). <IMAGE>

Description

SPECIFICATION Apparatus for mixing particulate material having an improved preheating device for material to be mixed The invention relates to a apparatus for mixing particulate material, having an improved preheating device for material to be mixed. The invention has particular but not exclusive application to the preparation of plastics materials wherein finegrained to coarse-grained raw materials are heated in a high-speed mixer to a temperature required for the production of the mixture involved and the mixed mixture is subsequently cooled in a cooling mixer until it is storable and transportable.

It is known for heating and cooling mixer combinations to carry out a heating process during a mixing procedure by rapid movements of the materials to be mixed and/or heating of the mixer container wall, and to carry out a cooling process by water cooling (Journal "Kunststoffe" (Plastics), 1970, pp. 829-832). A considerable amount of cooling water may, in this respect, be required. In most cases, the heat from the cooling water is lost. The heating involves, in particular when it is desired to shorten the mixing times, a high power consumption for the purposes of heating the material to be mixed, if fine-grained materials, for example, are mixed, as these materials require longer mixing and heating times than coarser materials.

An object of the invention is to provide a mixing apparatus in which the heating time for the materials to be mixed is reduced and the power consumption is decreased.

According to the present invention there is provided apparatus for mixing particulate material, comprising a mixer for mixing the particulate material such that the mixing thereof is performed at an elevated temperature, and means for extracting heat energy from the mixed material and utilising said energy to preheat material to be mixed in the mixing means.

Preferably the apparatus is adapted for mixing granular plastics material, wherein the mixer is operative at such a speed as to produce heating of the plastics material.

Also, preferably said means comprises a heat pump arranged to cool the mixed material and preheat the material to be mixed.

An embodiment of the invention will now be described by way of illustrative example with reference to the accompanying drawing.

The diagram in the drawing shows a heating and cooling mixer combination, in which fine-grained to coarse-grained raw plastics materials (loose materials) are supplied from a storage container 1 through a supply pipes 3 to a heating mixer container 4. The mixture material which is mixed and heated in the heating mixer container 4 is supplied to a cooling mixer container 5 and is removed from the latter after the termination of the cooling process. The cooling of the mixture material in the cooling mixer container 5 is carried out by means of a cooling fluid e.g. water in a surrounding water jacket 6.The heat energy in the cooling fluid flowing from the cooling mixer container is fed in a circuit to a heat pump 2 and is used to preheat the raw materials in the supply pipe 3 before they are supplied to the heating mixer container 4 and is supplied for this purpose in a hot water circuit 8 to a heat exchanger system between the material storage containers 1 and the heating mixer container 4.

In the embodiment, the cooling fluid passing through the circuit 7 flows at a temperature of 25"C from the cooling mixer container 5 to the cooling portion of the heat pump 2, from which the cooling fluid is discharged at a temperature of 15"C and is supplied to the cooling mixer container for cooling of the mixture material supplied at 120"C to 40"C.

The heating fluid flows from the heating portion of the heat pump 2 at 55"C and passes through the circuit 8 to the heat exchanger 2, where it flows in the direction opposite to the material supply direction and thereby heats the raw materials supplied at the room temperature of say 20"C from the storage container 1, so that this material reaches the heating mixer container 4 at a temperature of 50"C.

The heat exchanger 9 may comprise a heating jacket around the supply pipe 3 or may comprise a plurality of pipes arranged in a meander formation in or around the supply pipe.

Thus, it will be appreciated that considerable savings in power and shorter hearing and mixing times with respect to conventional plastics preparation methods are achieved by means of the preheating of the materials to be mixed, using the heat in the cooling fluid as the energy supply for the preheating.

The invention may be successfully used with materials other than plastics.

1. Apparatus for mixing particulate material, comprising a mixer for mixing the particulate material such that the mixing thereof is performed at an elevated temperature, and means for extracting heat energy from the mixed material and utilising said energy to preheat material to be mixed in the mixing means.

2. Apparatus according to claim 1 adapted for mixing granular plastics material, wherein the mixer is operative at such a speed as to produce heating of the plastics material.

3. Apparatus according to claim 1 or 2 wherein said means comprises a heat pump arranged to cool the mixed material and preheat the material to be mixed.

4. Apparatus according to claim 3 including a container arranged to receive the mixed material, and a water jacket around the container, the heat pump utilising heat energy in the water of said jacket to preheat the material to be mixed.

5. Apparatus according to claim 4 including a supply pipe for supplying material to be mixed to the mixer, and a heat exchanger arranged to receive heated fluid from the heat pump so as to heat material in the supply pipe.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for mixing particulate material having an improved preheating device for material to be mixed The invention relates to a apparatus for mixing particulate material, having an improved preheating device for material to be mixed. The invention has particular but not exclusive application to the preparation of plastics materials wherein finegrained to coarse-grained raw materials are heated in a high-speed mixer to a temperature required for the production of the mixture involved and the mixed mixture is subsequently cooled in a cooling mixer until it is storable and transportable. It is known for heating and cooling mixer combinations to carry out a heating process during a mixing procedure by rapid movements of the materials to be mixed and/or heating of the mixer container wall, and to carry out a cooling process by water cooling (Journal "Kunststoffe" (Plastics), 1970, pp. 829-832). A considerable amount of cooling water may, in this respect, be required. In most cases, the heat from the cooling water is lost. The heating involves, in particular when it is desired to shorten the mixing times, a high power consumption for the purposes of heating the material to be mixed, if fine-grained materials, for example, are mixed, as these materials require longer mixing and heating times than coarser materials. An object of the invention is to provide a mixing apparatus in which the heating time for the materials to be mixed is reduced and the power consumption is decreased. According to the present invention there is provided apparatus for mixing particulate material, comprising a mixer for mixing the particulate material such that the mixing thereof is performed at an elevated temperature, and means for extracting heat energy from the mixed material and utilising said energy to preheat material to be mixed in the mixing means. Preferably the apparatus is adapted for mixing granular plastics material, wherein the mixer is operative at such a speed as to produce heating of the plastics material. Also, preferably said means comprises a heat pump arranged to cool the mixed material and preheat the material to be mixed. An embodiment of the invention will now be described by way of illustrative example with reference to the accompanying drawing. The diagram in the drawing shows a heating and cooling mixer combination, in which fine-grained to coarse-grained raw plastics materials (loose materials) are supplied from a storage container 1 through a supply pipes 3 to a heating mixer container 4. The mixture material which is mixed and heated in the heating mixer container 4 is supplied to a cooling mixer container 5 and is removed from the latter after the termination of the cooling process. The cooling of the mixture material in the cooling mixer container 5 is carried out by means of a cooling fluid e.g. water in a surrounding water jacket 6.The heat energy in the cooling fluid flowing from the cooling mixer container is fed in a circuit to a heat pump 2 and is used to preheat the raw materials in the supply pipe 3 before they are supplied to the heating mixer container 4 and is supplied for this purpose in a hot water circuit 8 to a heat exchanger system between the material storage containers 1 and the heating mixer container 4. In the embodiment, the cooling fluid passing through the circuit 7 flows at a temperature of 25"C from the cooling mixer container 5 to the cooling portion of the heat pump 2, from which the cooling fluid is discharged at a temperature of 15"C and is supplied to the cooling mixer container for cooling of the mixture material supplied at 120"C to 40"C. The heating fluid flows from the heating portion of the heat pump 2 at 55"C and passes through the circuit 8 to the heat exchanger 2, where it flows in the direction opposite to the material supply direction and thereby heats the raw materials supplied at the room temperature of say 20"C from the storage container 1, so that this material reaches the heating mixer container 4 at a temperature of 50"C. The heat exchanger 9 may comprise a heating jacket around the supply pipe 3 or may comprise a plurality of pipes arranged in a meander formation in or around the supply pipe. Thus, it will be appreciated that considerable savings in power and shorter hearing and mixing times with respect to conventional plastics preparation methods are achieved by means of the preheating of the materials to be mixed, using the heat in the cooling fluid as the energy supply for the preheating. The invention may be successfully used with materials other than plastics. CLAIMS

1. Apparatus for mixing particulate material, comprising a mixer for mixing the particulate material such that the mixing thereof is performed at an elevated temperature, and means for extracting heat energy from the mixed material and utilising said energy to preheat material to be mixed in the mixing means.

2. Apparatus according to claim 1 adapted for mixing granular plastics material, wherein the mixer is operative at such a speed as to produce heating of the plastics material.

3. Apparatus according to claim 1 or 2 wherein said means comprises a heat pump arranged to cool the mixed material and preheat the material to be mixed.

4. Apparatus according to claim 3 including a container arranged to receive the mixed material, and a water jacket around the container, the heat pump utilising heat energy in the water of said jacket to preheat the material to be mixed.

5. Apparatus according to claim 4 including a supply pipe for supplying material to be mixed to the mixer, and a heat exchanger arranged to receive heated fluid from the heat pump so as to heat material in the supply pipe.

6. Apparatus according to claim 5 wherein the heat exchanger comprises a heating jacket around the supply pipe.

7. Apparatus according to claim 5 wherein the heat exchanger comprises a plurality of pipes arranged in a meander formation.

8. Apparatus for mixing materials, substantially as hereinbefore described with reference to the accompanying drawings.

9. A preheating device for heating and cooling mixer combinations, in which, for the preparation of plastics materials in particular, fine-grained to coarse-grained raw materials are heated in a highspeed mixer to a temperature required for the production of the mixture involved and the mixture material is subsequently cooled in a cooling mixer until it is storable and transportable, characterised in that the cooling mixer container is connected, via a pipeline forming a circuit for the cooling agent, with a heat pump and in that the latter is connected, via a pipeline forming a circuit for the heat carrier, with a heat exchanger which comprises a plurality of heat exchanger ducts and is associated with the supply pipe between the material storage container and the heating mixer container.