GB1581030A

GB1581030A - Comminution process

Info

Publication number: GB1581030A
Application number: GB2330576A
Authority: GB
Original assignee: BOC Ltd
Current assignee: BOC Ltd
Priority date: 1977-06-16
Filing date: 1977-06-16
Publication date: 1980-12-10

Description

(54) COMMINUTION PROCESS (71) We BOC LIMITED, an English Company of Hammersmith House, London W6 9DX, England, do hereby declare the invention for which we pray that a patent may be granted to us, to be particularly described in and by the following statement: - This invention relates to a comminution process and in particular to a method of recovering confectionery from a composite confectionery product (by which is meant a product consisting of two or more different constituents; at least one of which is a confectionery constituent), which process includes the step of comminuting the composite confectionery product.

Examples of composite confectionery products are those having an outer covering or coating of chocolate and an inner body of a different confectionery sucll as turkish delight, toffee, caramel, fudge, peanut butter and so-called 'creams' which typically comprise sugar, water, egg yolk and colouring and flavouring ingredients, or may include biscuit or nuts, together, if desired, with confectionery.

Composite confectionery products are very popular with the general public, both in the United Kingdom and overseas.

Although the products are manufactured by efficient processes, a small proportion of the products become damaged during manufacture and are rendered unfit for sale. Since the products are manufactured in very large quantities total weight of unsaleable confectionery is considerable. It is thus economically important to recycle the waste confectionery.

The method conventionally-adopted for recycling damaged composite confection ery products involves melting the confectionery and adding suitable ingredients to the molten confectionery to obtain as a product a different confectionery having a different balance of ingredients from the confectioneries which were included in the original composite product. Often the 'reworked' confectionery is of a lower quality than the original products. In addition, the reclamation processes are relatively expensive as they are labourintensive. Moreover, some types of confectionery, notably peanut butter, are not suitable for reworking.

According to the present invention there is provided a method of separating a composite confectionery product (as hereinbefore defined) into its different constituents, in which method the temperature of the product is reduced to sufficiently below ambient by a cooling medium to render the product fit for comminution into small solid particles; the cooled product is comminuted into small solid particles of the different constituents that make up the product, and the particles are classified into portions of different density in a gas classifier.

The composite confectionery product is preferably cooled by contact with a cryogenic liquid, preferably liquid carbon dioxide or liquid nitrogen; or its vapour, or both. Alternatively, contact with a gas (typically air) which has been reduced in temperature by heat exchange with a cold fluid may effect the cooling of the confectionery product.

The cooling may be performed in a tunnel through which damaged composite confectionery products are advanced on a conveyor and into which a cryogenic liquid such as liquid nitrogen is introduced, for example by being sprayed, there being fans to cause cold vapour evaporating from the cryogenic liquid to pass over the products as they are passed through the tunnel by the conveyor. Such equipment is well known and is widely used in the food freezing industry.

By the term 'cryogenic liquid' as used herein is meant a liquid which at atmospheric pressure boils at -500F or below.

The maximum temperature to which the composite confectionery product should be cooled in order to be fit for comminution would depend on the nature of the constituents of the product. In general, this maximum will be from +5 to --500C. If the composite product contains chocolate as a constituent it is necessary to lower the temperature of the product such that the chocolate is brittle or 'frozen' and does not melt during grinding. If the composite product contains a 'cream' as a constituent it is necessary to ensure that all the cream is frozen before comminuting the product.

Constituents such as toffee, although solid at ambient temperature, tend to be viscous (i.e. sticky) and sometimes resilient rather than brittle. It is necessary for such constituents to be cooled to a temperature at which they are brittle and not appreciably viscous. Similarly, constituents such as turkish delight should be cooled to a -tem- perature at which they are brittle or 'frozen' rather than being like a jelly in nature.

The temperature to which the composite confectionery product may be lowered, in order to meet the respective criteria discussed in the preceding paragraph, may be determined by simple experiment. A uniform temperature will not generally be attained throughout the cross-section of the product after the product has been cooled. Care must therefore be taken to ensure that the innermost part of the product attains a sufficiently low temperature for that part of the product to be comminuted successfully.However, by cooling the product by advancing it on a conveyor through a tunnel in which it is contacted with cryogenic liquid, or cold vapour evaporated from the liquid, or both, it is possible to set the rate at which the product is advanced through the tunnel and the rate at which the cryogenic liquid or cold vapour is introduced into the tunnel such that by the time the product emerges from the tunnel there is no part of the product which is at a temperature too high for it to be comminuted.

It is to be appreciated that the process of comminution may generate some heat.

It is therefore desirable to ensure that cold vapour or cold gas which has been used to cool the composite confectionery product before comminution is introduced into the apparatus used to comminute the product. Moreover, it is desirable to sense the temperature at the outlet of the comminution apparatus and use the sensed temperature to control the cooling of the composite product.Por example, if a freezing tunnel is used to cool the composite confectionery product a temperature sensor located at the outlet of the comminution apparatus may be used to generate a signal which aauates one or more solenoid valves in the conduits used to supply cryogenic fluid to the freezing tunnel so as to increase the rate at which the - cryogenic fluid is supplied, and if the temperature sensed by the sensor is below a chosen minimum to generate signals effective to actuate the solenoid valve or valves so as to reduce the rate at which cryogenic fluid is introduced into the tunnel. Normally, the freezing tunnel and comminution apparatus will be set up so that the sensed temperature is predominantly between the chosen minimum and maximum values.

In general, a suitable comminution apparatus is an impact mill preferably of the rotary swing hammer type. For some products such as cholocate 'bars' containing turkish delight (i.e. a longitudinal body of turkish delight in a casing of chocolate) it is preferred to use a granulator in which the confectionery product is chopped up into small pieces by means of sharp knife edges. It is also possible to use a mill, such as a ball mill, in which the confectionery product is crushed, although in general use of such a mill is not preferred.

The comminution apparatus is preferably operated so as to produce particles of the composite confectionery product having particle sizes in the range 0.5 to 2 mm when a granulator is being used and 0.1 to 1 mm when a mill is being used.

A gas classifier is a well known device in which a fan or turbine (referred to hereinafter as the selector turbine) is used to induce an upward flow of a gas stream in which are suspended small particles of the material to be separated. According to the size and density of the particles some will flow through the selector turbine whereas others will not reach the selector turbine but instead fall downwards under gravity.

Thus, if all are of the same particle size the particles of the greater density will fall downwards whereas the particles of smaller density will pass through the selector turbine. A suitable type of gas classifier for use in the method according to the present invention is the "Micron Separator" manufactured and sold by the Hosokawa Iron Works Limited, Osaka, Japan.

Transfer of the particulate material from the comminution apparatus to the gas classifier will normally be effected by connecting the outlet of the comminution apparatus to the conduit of the classifier that conveys the particulate material into the classifier in suspension in gas.

It is important to prevent the temperature of the particulate material from rising in the gas classifier to such an extent that some particles become viscous and stick together. In order to prevent this problem arising, the gas in which the particulate material from the comminution apparatus is carried into the classifier may be lowered in temperature. This is preferably achieved by introducing into the conduit a cryogenic coolant which is mixed with the gas (normally air) flowing therealong. The cryogenic coolant is preferably liquid car bon dioxide or liquid nitrogen. If desired, the introduction of the cryogenic coolant may be controlled by sensing the tempera ture downstream of the selector turbine of the classifier.Thus, if the sensed tempera ture is above a chosen maximum cryogenic coolant may be introduced into the conduit and if the sensed temperature is below a chosen minimum the supply of cryogenic coolant may be discontinued or reduced in rate. If desired this control of the rate of introduction of cryogenic coolant can be performed automatically. For example, the temperature sensor downstream of the selector turbine may generate a signal cor responding to the sensed temperature, which signal actuates a solenoid valve or valves in a pipe through which the cryo genic coolant is passed.

In some air classifiers a separate stream of balancing gas is supplied in addition to that which carries the particulate material.

Normally, the amount of balancing gas re quired is drawn by the classifier from its surroundings. If desired, cryogenic coolant may be introduced into this secondary supply of gas instead of or in addition to the cryogenic coolant that is introduced into the gas in which the particulate material from the comminution apparatus is entrained. Normally, however, this is not preferred.

Thus, the portion of higher density par ticles or the portion of lower density par ticles, or both portions, may be passed into its own gas classifier on leaving the primary gas classifier. Moreover, if necessary, either or both portions from one of these additional classifiers may be passed on to a further clasifier or back to the original classifier. The number of classifiers that are required to be used and the sequence in which they are to be used may be de termined by simple experiment. In each additional classifier it is preferable to provide means for, injection of a cryogenic coolant into the conduit along which the particulate material is conducted into that classifier.

It is generally desirable to collect the portion of lower density particles from the or each classifier in a powder collector before it is taken away as product or passed on to a further gas classifier. One well known form of powder collector has a fan or like device which draws the powder through filter material on which the powder collects. By blowing in the opposite direction the powder may be disengaged from the filter material and may thus be collected in the base of the collector.

Desirably, an rotary valve or like device -is located in the bottom of the or each powder collector so as to isolate the region downstream of the device or like device from the fan.

By way of example, the composite confectionery product may comprise an outer casing which contains peanut butter in which are embedded peanuts. After com minution particles of this product may be passed into a first classifier in which they are separated into less dense and more dense portions. The more dense portion may be passed into a secondary classifier in which it is separated into a heavy fraction consisting substantially of chocolate powder and a lighter fraction which is collected in a dust collector and consists substantially of peanut butter. The less dense portion from the first classifier is passed into a powder collector in which it is collected and then passed into a tertiary gas classifier in which it is separated into less dense and more dense fractions.The denser of the two fractions from the tertiary classifier consists substantially of peanut butter and is taken therefrom. The less dense fraction from the tertiary classifier is collected in a powder collector and consists substantially of peanut particles.

The three constituents, namely, peants, peanut butter and chocolate may be used to manufacture more of a composite confectionery product containing - these three constituents.

Desirably the or each gas classifier and the or each dust collector, preferably together with the comminution apparatus and cooling equipment (e.g. a cooling tunnel), are preferably positioned in an insulater chamber or room. Accordingly, cold gas exhausted from the dust collectors is maintained within the insulating chamber or rooms and will therefore again be drawn into the gas classifier or classifiers and thus relatively little of the refrigerative capacity of the cold gas is wasted.

The method according to the present invention makes possible recovery of the confectionery constituents of a composite confectionery product in a state such that they can be reused to make more of the confectionery composite product. If the confectionary composite product contains constituents such as biscuit it may be de sirable to feed the particles of biscuit that are collected as a result back to a biscuit making machine before reusing them.

The invention also provides apparatus for separating a composite confectionery product into its constituents, comprising means for cooling the composite confec tionery product to a temperature suffi ciently below ambient to render the pro duct fit for comminution into small solid particles, a comminution device for com minuting the cooled product into small -solid particles of the different constituents that make up the product and at least one gas classifier for separating the particles into portions of different density.

In one preferred embodiment of cooling device for -use in the method according to the present invention the composite con fectionery product is cooled by the cooling medium as it passes through a conveyor which, in operation, feeds the product to ,a device for comminuting the cooled pro duct, the conveyor comprising a rotary drum or tunnel which is inclined down wards from its inlet to its outlet. Such a conveyor is capable of feeding agglomer ated lumps of material such as broken chocolate to the comminution device(s).

The output of cooled composite con fectionery product from the rotary drum or tunnel may be varied by varying the amount of composite confectionery pro duct that is fed into the drum. The resid ence time of the confectionery product in the drum may be selected by choosing an appropriate speed at which to rotate the drum.

The angle of inclination of the longi tudinal axis of the drum or tunnel to the horizontal is preferably between 2 and 10 .

This makes possible a residence time suffi ciently long for the composite material to be cooled to the chosen temperature whilst still making possible adequate flow of com posite confectionery material into the mill or other comminution device.

The rotary drum or tunnel preferably has associated therewith a sprayer or similar means for introducing cryogenic liquid into its interior. It preferably also has associated therewith a fan which, in operation, causes vapour evaporated from the cryogenic liquid to pass along the in terior of the drum. Desirably the sprayer or other means for introducing the cryo genic liquid into the drum is positioned at or near to the inlet of the drum whereas the fan should preferably have an inlet conduit positioned in communication with the outlet end of the drum or tunnel. By this means a flow of evaporated cryogenic liquid may be established from one end to the other of the drum.

Preferably the rotating drum or tunnel has baffles or like means disposed inwardly thereof. The baffles or like means may per form two functions. First, they are able to facilitate mixing of material being cooled in the conveyor. Second, they promote heat exchange between the confectionery product and the cold vapour evaporated from the cryogenic liquid by slowing down the passage of - gas (normally cold air with the vapour of the cryogenic liquid entrained therein) therethrough. Conveniently, the baffle is provided by a helical land integral with or attached to the inner surface of the drum.

The rotary drum or tunnel will normally have a staionary feed chute at its inlet end through which the composite confectionery product may be fed into the drum. A suitable rotary seal should be provided between the inlet chute and the inlet end of the drum so as to prevent vapour from the cryogenic liquid escaping there between. The inlet of the drum is preferably of wider cross section than the rest of the drum. In addition, the sprayer or other means for introducing cryogenic liquid into the drum is preferably directed towards which ever part of the drum is positioned upper most (it will be appre ciated that the sprayer of cryogenic liquid will be fixed and will not rotate with the drum). By this means the inlet end of the rotary drum functions as a trough and collects cryogenic liquid from the sprayer other means of introducing the liquid into the drum.Moreover, the chute is preferably so arranged that as composite confectionery product falls there through under gravity it comes into contact with the volume of cryogenic liquid held in the trough at the inlet end of the drum.

The temperature sensor is preferably located in or near to (but upstream of) the inlet conduit of the fan. By this means an approximate measure of the temperature of the composite confectionery products leaving the drum may be obtained. If desired, the temperature sensor may generate signals adapted to cause an automaticallyoperated valve controlling the passage of cryogenic liquid to the sprayer (or other means of introducing cryogenic liquid into the drum) to open the sensed temperature rises above a chosen value, and to dose if the sensed temperature falls below a chosen value. By this means, the composite confectionery product may be fed to the mill or other comminution device at a known controlled temperature.

Preferably the flow-control valve is located in the inlet conduit of the fan. By appropriately setting this valve the volume of cold gas that is exhausted from the rotary drum by the fan may be kept down.

The fan has an outlet which preferably communicates with an enclosed space from which the or each classifier draws gas. By this means such refrigeration as is wasted by exhausting cold gas from the rotary drum may be exploited in the classifiers as a means for ensuring that the respective confectionry materials are maintained at a temperature at which they are relatively non-viscous (i.e. non-sticky).

The method and apparatus according to the present invention will now be described by way of example with reference to the accompanying drawings, of which: - Figure 1 is diagrammatic representation of one form of apparatus for performing the method according to the present invention; Figure 2 is schematic representation of apparatus for controlling the introduction of cryogenic liquid into the cooling tunnel shown in Figure 1; Figure 3 its a schematic representation of apparatus for controlling the introduction of the cryogenic coolant into the feed pipe 1 of the gas classifiers shown in Figure 1.

Figure 4 is a schematic representation of an alternative form of conveyor to that shown in Figure 1.

Referring to Figure 1 of the drawings, a cooling tunnel 2 has an access opening 4 through which composite confectionery products can be loaded onto the right hand end (as shown) of an endless conveyor belt 6 which is mounted on a driven wheel 8 and a idler wheel 10. The composite confectionery food products fed onto the endless belt 6 may for example have a chocolate casing in which is enclosed a mixture of peanut butter and peanuts. Associated with the cooling tunnel 2 is a storage tank containing liquid nitrogen 12. A pipe 14 conveys the liquid nitrogen to sprayers 16 (a) to 16 (f) located inside the tunnel.

Thus, liquid nitrogen may be introduced into the tunnel through these sprayers. Also located in the tunnel above the conveyor belt 6 are several fans 18 (only two shown).

The purpose of the fans is to cause the vapour formed by the evaporation of liquid nitrogen within the tunnel to flow over the composite confectionery products as these are advanced along the tunnel by the conveyor belt 6.

On its left hand side (as shown) the tunnel 2 has an outlet 20 situated below the left hand end of the. conveyor belt such that the composite confectionery food products fall off the conveyor belt and pass under gravity through the outlet 20. The outlet 20 leads into the top of an impact mill 22 having rotary swing-hammers 24.

At its bottom the mill has an outlet grid 26, the spaces between the bars of the grid being chosen such that particles of confectionery product will not fall therethrough under gravity unless their size is below a chosen maximum.

The grid 26 of the mill 22 is situated in a funnel 28 whose narrower end terminates in the feed conduit 30 of a first gas classifier 32. The feed conduit 30 has a horizontal limb 34 having an inlet 36 for air and a vertical limb 38 which terminates in a chamber 40 at a region below a rotor 42 which carries blades 44 which can be set at a rotational speed suitable for the selecting of those particles too dense to pass through blades 44 into an outlet 50. Flow of gas into the inlet 36 of the conduit 30 and of particulate material from mill 22 is caused by a suction fan 68 (described later.) The fan 68 is also effective to induce a flow of air into the chamber 40 through a secondary inlet 46 located- approximately at the level of the outlet of the vertical limb 38 of the feed conduit 30. The chamber 40 has a lower chute portion 48 below the rotor 42.

In order to maintain suitable temperature conditions within the gas classifier 32 a sprayer 52 is located in the horizontal limb of the conduit 30 and is connected by means of a pipe 54 to the source 12 of liquid nitrogen. Thus, liquid nitrogen may, when desired, be sprayed into the conduit 30.

In operation of the gas classifier 32, the particulate material from the mill 22 is separated into a relatively low density portion which tends to be carried upwardly through the classifier and leaves it by way of the oulet 50, and a relatively high density portion which falls under gravity down the chute 48. A rotary valve 56 at the outlet feeds the powder collected in the chute into the main air conduit of a secondary gas classifier.

This classifier is identical to the first gas classifier 32 and for convenience the parts of the secondary gas classifier will be given in the same reference numerals as the corresponding parts of the first gas classifier, the suffix (a) being used to disinguish the integers of the secondary gas classifier from their counter parts in the first gas classifier.

The outlet 50 of the first gas classifier 32 is connected by means of a pipe 60 to a powder collector 62. The powder collector 62 has filter means 64 and, downstream of the filter means 64, a pipe 56 which is connected to the suction fan 68.

At the base of the powder collector 62 is an outlet 70 for powder in which outlet a rotary valve 72 is connected.

In operation the fan 68 draws into the powder collector 62 a stream of gas from the inlet 36 of the conduit 30, thereby entraining in this gas particulate material from the mill 22 and an additional gas stream from the secondary inlet 46 to the classifier 32. The gas streams combine in the classifiers and leave via the selector turbine 44 and the outlet 50 together with the entrained lighter density material from classifier 32. The gas and particulate material is sucked into the powder collector 62.- The gas then passes through the filter material 64 leaving the powder on the upstream side of this filter material. The powder collector 62 is preferably of the type in which the filter material 64 is formed into 'socks' in which the powder is collected.The powder may be disengaged from these socks by stopping operation of one sock at a time and applying a reverse flow of compressed air to that sock, each sock being automatically 'reverse-blown' - in sequence. This has the effect of blowing the particulate material out of the 'socks' This type of powder collector is well known and is commercially available.

The outlet 50(a) of the secondary gas classifier 32(a) is also connected to a powder collector and ancillary equipment identical to the powder collector 62 and the ancillary equipment associated there with. The powder collector connected to the outlet 50(A) of the secondary gas class fier 32(a) will be indicated by the same reference numeral (I.E. 62) as the powder collector connected to the first gas classifier 32. Moreover, the suffix (a) is appended this secondary powder collector 62 in order to distinguish it from the first powder collector 62. An analogous arrangement is used to distinguish the parts of the second powder collector 62 (a) from the first powder collector 62.

The outlet 70 of the powder collector 62 is in communication with the main air conduit 30 (b) of a gas classifier 32 (b) which is identical in every respect to the gas classifiers 32 and 32 (a). The outlet 50 (b) of the classifier 32 (b) is connected to a powder collector 62 (b) by means of a pipe or conduit 60 (b). The powder collector 62 (b) is identical to the powder collectors 62 and 62 (a).

In operation of the plant shown in Fig.

1, the constituent of lowest density is collected in the powder collector 62 (b), the constituent of highest density is collected in the shute 48 (a) of the gas classifier 32 (a) and the constituent or constituents of intermediate density are collected in the powder collector 62 (a) and the shute 48 (b) of the gas classifier 32 (b).

If the product is a bar comprising a chocolate case containing a mixture of peanut butter and peanuts, the chocolate will be collected as the most dense consuituent, the peanuts as the least dense constituent and the peanut butter as the constituent of intermediate density.

Control of the introduction of cryogenic liquid into the cooling tunnel 2 trough the sprayers 16 (a) to (f) may be effected by the control circuit indicated in Figure 2.

A temperature sensor 80 located just below the grid 26 of the mill 22 is adapted to generate signals in accordance with the sensed temperature which control the operation of solenoid valves 82 (a) to 82 (f) in conduits 84 (a) to (f) respectively, each of which conduits is connected to the conduit 14 which communicates with the source 12 of liquid nitrogen. In each of the conduits 84 (a) to (f) there is a flow control valve 86.

The temperature sensor 80 and the solenoid valves may be connected in electrical circuit such that when the sensed temperature is within a chosen temperature range in the valves 82 (a), 82 (c) and 82 (e) are open and the valves 82 (b), 82 (d) and 82 (f) are shut; when the sensed temperature is below the chosen minimum all the valves 82 (a) to (f) are shut, and when the sensed temperature is above the chosen maximum all the valves 82 (a) to 82 (f) are open. When setting up the plant shown in Fig. 1, it is desirable to set the flow control valves 86 (a) to 86 (f) into such a position that during normal operation of the plant only the valves 82 (a), 82 (c) and 82 (e) are open so that liquid nitrogen is sprayed into the cooling tunnel 2 only through the spray headers 16 (a), 16 (c) and 16 (e).

A system for controlling the introduction of liquid nitrogen into the conduit 30 of the gas classifier 32 is illustrated in Figure 3 of the accompanying drawings. An identical system may be used for each of the gas classifiers 32 (a) and 32 (b). The sprayer 52 and the pipe 54 to which it is connected communicate with conduits 90 and 92 both of which are in turn connected to a pipe 94 which is in communication with the source 12 of liquid nitrogen. A solenoid valve 96 is located in the conduit 90 and another solenoid valve 98 is located in the conduit 92. The solenoid valves 96 and 98 are to be actuated by electrical signals generated by a temperature sensor 100 located in a region of the pipe 60 just downstream of the outlet 50 of the classifier 32. A flow control valve 102 is located in the conduit 90 in a position upstream of the solenoid valve 96. Another flow control valve 104 is located in the conduit 92 in a position upstream of the solenoid valve 92.

In operation, the control circuits of the solenoids of the valves 96 and 98 may be set such that when the temperature sensed by the sensor 100 is within a chosen range the solenoid valve 96 is open and the solenoid valve 98 is shut; when the sensed temperature is below the chosen minimum both solenoid valves are closed, and when the sensed temperature is above the chosen maximum both solenoid valves are open.

A consequence of this arrangement is that when the sensed temperature is above the chosen maximum the rate of introduction of liquid nitrogen is greater than when it is in the chosen range, and when the sensed temperature is below the chosen minimum no liquid nitrogen is introduced into the conduit 30 from the sprayer 52. When setting up the plant shown in Figure 1 the valves 102 and 104 may be adjusted so as to ensure that during normal operation of the plant the solenoid valve 96 is open and the solenoid valve 98 is closed.

The conveyor shown in figure 4 of the drawings is intended to be used in place of the conveyor 2 shown in Figure 1 of the drawings. The conveyor has a stationary inlet chute 105 into which composite confectionery material may be fed from a hopper 107. The inlet end 106 of a rotary drum 108 makes a sealing engagement with the chute 105. The inlet end 106 of the rotary drum 108 is formed in 2 integral portions. The outer portion 110 is of wider circular cross-section than the main portion 114 of the drum 108 that is coaxial therewith. The inner portion 112 of the outlet end 106 is frusto-conical in cross-section and is that portion of the drum 106 which is intermediate the main portion 114 and the end portion 110.The lower most parts of the portions 110 and 112 cooperate to form a trough in which a volume 118 of liquid nitrogen may be held if liquid nitrogen is sprayed therein from a sprayer 120 which is connected by a conduit 122 to a source 124 of liquid nitrogen.

The outlet end 106 of the rotary drum makes a sealing engagement with a stationary outlet chute 128 which leads to a mill (not shown) for comminuting composite confectionery product issuing from the drum 108. In communication with the top of the chute 128 is a conduit 130 which forms the inlet to a fan 132. The conduit 130 has disposed therein a flow control valve 134. The fan has an outlet 136 which communicates with an enclosure (not shown) from which classifiers to be used in conjunction with the rotary drum conveyor may draw their gas supply.

The main portion 116 of the rotary drum is inclined at an angle of 5 to the horizontal. This enables the composite confectionary product fed thereto to fall under gravity into the outlet chute 128. The inner surface of the main portion 116 of the rotary drum 108 has fallen integrally therewith a helical land 138.

Positioned in the chute 128 near to the conduit 130 is a temperature sensor 140.

The temperature sensor 140 generates electrically signals adapted to actuate electric- ally relays 142 which controls the operation of a solenoid-valve 144 positioned in the conduit 122. By this means, whether or not the solenoid valve 144 is open and hence whether or not liquid nitrogen is introduced into the rotary drum 108, may be determined by the temperature of the cold gas leaving the rotary drum 108.

In operation, agglomerated composite confectionery product is fed into the inlet end 106 of the rotary drum 108 from the hopper 104. Liquid nitrogen is sprayed into the inlet end 106 thereby causing the volume of liquid 118 to be collected. The drum 108 is rotated at a suitable speed by means of a belt drive (not shown). Confectionery material falls into the volume of liquid nitrogen 118 and then leaks its way under gravity down the main portion 116 of the drum 108. The land 138 causes at least a portion of the composite confectionery product to pursue a helical path as it flows downwards through the rotary drum 108. In addition, the land 138 acts as a baffle to cause cold nitrogen evaporating from the volume 118 of liquid nitrogen to pursue a tortous path as it is drawn along the main portion 116 of the drum 108 by the fan 132.This facilitates heat exchange between the cold nitrogen vapour and the composite confectionery product flowing through the rotary drum 108. The valve 134 may be set so as to limit the amount of cold gas that is exhausted from the rotary drum 108.

When it has reached the end 126 of the rotary drum the confectionery product falls under gravity into a chute 128 and from there, into the mill or other comminution device (not shown).

The temperature sensor 140 and the relay 142 may be programmed such that liquid nitrogen is sprayed into the rotary drum 108 at a rate sufficient to maintain the outlet temperature at or near to a chosen temperature, say, --10"C.

Preferably from 41 to 4 of the available space in the drum is occupied by composite confectionery product when the conveyor is operated. This helps to give adequate heat exchange between cold gas passing along the drum and the confectionery product.

WHAT WE CLAIM IS: - 1. A method of separating a composite confectionery product (as hereinbefore defined) into its different constituents, in which method the temperature of the product is reduced to sufficiently below ambient by a cooling medium to render the product fit for - comminution into small solid particles; the cooled product is comminuted into small solid particles of the different constituents .that make up the product, and the particles are classified into portionstof different density in a gas classifier.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. when the sensed temperature is above the chosen maximum the rate of introduction of liquid nitrogen is greater than when it is in the chosen range, and when the sensed temperature is below the chosen minimum no liquid nitrogen is introduced into the conduit 30 from the sprayer 52. When setting up the plant shown in Figure 1 the valves 102 and 104 may be adjusted so as to ensure that during normal operation of the plant the solenoid valve 96 is open and the solenoid valve 98 is closed. The conveyor shown in figure 4 of the drawings is intended to be used in place of the conveyor 2 shown in Figure 1 of the drawings. The conveyor has a stationary inlet chute 105 into which composite confectionery material may be fed from a hopper 107. The inlet end 106 of a rotary drum 108 makes a sealing engagement with the chute 105. The inlet end 106 of the rotary drum 108 is formed in 2 integral portions. The outer portion 110 is of wider circular cross-section than the main portion 114 of the drum 108 that is coaxial therewith. The inner portion 112 of the outlet end 106 is frusto-conical in cross-section and is that portion of the drum 106 which is intermediate the main portion 114 and the end portion 110.The lower most parts of the portions 110 and 112 cooperate to form a trough in which a volume 118 of liquid nitrogen may be held if liquid nitrogen is sprayed therein from a sprayer 120 which is connected by a conduit 122 to a source 124 of liquid nitrogen. The outlet end 106 of the rotary drum makes a sealing engagement with a stationary outlet chute 128 which leads to a mill (not shown) for comminuting composite confectionery product issuing from the drum 108. In communication with the top of the chute 128 is a conduit 130 which forms the inlet to a fan 132. The conduit 130 has disposed therein a flow control valve 134. The fan has an outlet 136 which communicates with an enclosure (not shown) from which classifiers to be used in conjunction with the rotary drum conveyor may draw their gas supply. The main portion 116 of the rotary drum is inclined at an angle of 5 to the horizontal. This enables the composite confectionary product fed thereto to fall under gravity into the outlet chute 128. The inner surface of the main portion 116 of the rotary drum 108 has fallen integrally therewith a helical land 138. Positioned in the chute 128 near to the conduit 130 is a temperature sensor 140. The temperature sensor 140 generates electrically signals adapted to actuate electric- ally relays 142 which controls the operation of a solenoid-valve 144 positioned in the conduit 122. By this means, whether or not the solenoid valve 144 is open and hence whether or not liquid nitrogen is introduced into the rotary drum 108, may be determined by the temperature of the cold gas leaving the rotary drum 108. In operation, agglomerated composite confectionery product is fed into the inlet end 106 of the rotary drum 108 from the hopper 104. Liquid nitrogen is sprayed into the inlet end 106 thereby causing the volume of liquid 118 to be collected. The drum 108 is rotated at a suitable speed by means of a belt drive (not shown). Confectionery material falls into the volume of liquid nitrogen 118 and then leaks its way under gravity down the main portion 116 of the drum 108. The land 138 causes at least a portion of the composite confectionery product to pursue a helical path as it flows downwards through the rotary drum 108. In addition, the land 138 acts as a baffle to cause cold nitrogen evaporating from the volume 118 of liquid nitrogen to pursue a tortous path as it is drawn along the main portion 116 of the drum 108 by the fan 132.This facilitates heat exchange between the cold nitrogen vapour and the composite confectionery product flowing through the rotary drum 108. The valve 134 may be set so as to limit the amount of cold gas that is exhausted from the rotary drum 108. When it has reached the end 126 of the rotary drum the confectionery product falls under gravity into a chute 128 and from there, into the mill or other comminution device (not shown). The temperature sensor 140 and the relay 142 may be programmed such that liquid nitrogen is sprayed into the rotary drum 108 at a rate sufficient to maintain the outlet temperature at or near to a chosen temperature, say, --10"C. Preferably from 41 to 4 of the available space in the drum is occupied by composite confectionery product when the conveyor is operated. This helps to give adequate heat exchange between cold gas passing along the drum and the confectionery product. WHAT WE CLAIM IS: -

1. A method of separating a composite confectionery product (as hereinbefore defined) into its different constituents, in which method the temperature of the product is reduced to sufficiently below ambient by a cooling medium to render the product fit for - comminution into small solid particles; the cooled product is comminuted into small solid particles of the different constituents .that make up the product, and the particles are classified into portionstof different density in a gas classifier.

2. A method as claimed in claim 1, in

which the cooling medium is a cryogenic liquid (as hereinbefore defined) or its vapour, or both.

3. A method as claimed in claim 2, in which the cryogenic liquid is liquid nitrogen.

4. A method as claimed in any one of the preceding claims, in which the cooling is performed on a tunnel through which damaged composite confectionery products are advanced and into which a cryogenic liquid (as hereinbefore defined) is introduced.

5. A method as claimed in claim 4, in which the cryogenic liquid is sprayed into the tunnel.

6. A method as claimed in claim 4 or claim 5, in which cold vapour evaporating from the cryogenic liquid is caused to pass over the products as they are advanced through the tunnel by the conveyor.

7. A method as claimed in any one of the preceding claims, in which the products are cooled to a temperature in the range +5 to -500C.

8. A method as claimed in any one of the preceding claims, in which the confectionery product is comminuted in a rotary swing-hammer mill.

9. A method as claimed in any one of claims 1 to 7, in which the confectionery product is comminute in a granulator by means of sharp knife edges.

10. A method as claimed in claim 8, in which the composite confectionery product is comminuted to produce particles having sizes in the range 0.1 to 1 mm.

11. A method as claimed in claim 9, in which the composite confectionery product is comminuted to produce particles having sizes in the range 0.5 to 2 mm.

12. A method as claimed in any one of the preceding claims, in which the gas passing into the classifiers has coolant intro.

duced therein.

13. A method as claimed in claim 12, in which the coolant is a cryogenic liquid (as hereinbefore defined).

14. A method as claimed in claim 12 or claim 13, in which the coolant is introduced into the conduit of the classifier that conveys the comminuted product into the classifier in a gaseous suspension.

15. A method as claimed in any one of claims 12 to claim 14, in which coolant is introduced into a stream of balancing gas that is supplied in addition to the gas that carries the comminuted product into the classifier.

16. A method as claimed in any one of the preceding claims, in which there is more than one gas classification of the comminuted product.

17. A method as claimed in any one of the preceding claims, - in which the portion of lower density particles is collected from the or each gas classification stage is col lected in a powder collector before being taken away as product or being passed onto a further gas classification stage.

18. A method as claimed in any one of the preceding claims, in which all the gas classification, comminution and cooling equipment is located in an insulated chamber or room.

19. A method as claimed in claim 1, in which the composite confectionery pro duct is cooled by the cooling medium as it passes through a conveyor which, in operation, feeds the product to a device for comminuting the cooled product, the conveyor comprising a rotary tunnel or drum which is inclined downwards from its inlet to its outlet.

20. A method as claimed in claim 19, in which the drum or tunnel is inclined at an angle of 2 to 10 to the horizontal.

21. A method as claimed in claim 19 or claim 20, in which the drum or tunnel has associated therewith means for intro ducing cryogenic liquid into its interior.

22. A method as claimed in claim 21, in which a fan has its inlet in communication with the outlet end of the drum or tunnel.

23. A method as claimed in claim 22, in which means for introducing cryogenic liquid into the drum or tunnel are situated at or near the inlet end of the drum or tunnel.

24. A method as claimed in any one of claims 19 to 23, in which the drum or tunnel has inwardly extending baffles.

25. A method as claimed in any one of claims 19 to 23, in which the drum or tunnel has on its inner wall a helical land.

26. A method of separating a composite confectionery product (as hereinbefore defined) into its different constituents substantially as hereinbefore described with reference to Figures 1 to 3 of the accom panying drawings.

27. A method as claimed in claim 1, in which there is employed at least one con -vey or substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.

28. Apparatus for separating a composite confectionery product (as hereinbefore defined) into its constituents, comprising means for cooling the composite confectionery product to a temperature sufficiently below ambient to render the product fit for comminution into small solid particles, a comminution device for comminuting the cooled product into small -solid particles of the different constituents that make up the product and at least one gas classifier for separating the particles into portions of different density.

29. Apparatus for separating a composite confectionery product (as hereinbefore defined) into its separate constituents substantially as herein described with reference to and as shown in Figures 1 to 3 of the accompanying drawings.

30. Apparatus as claimed in claim 28, including at least one conveyor substantially as herein described with reference to, and as shown in Figure 4 of the accompanying drawings.