FI74596B - FOERFARANDE OCH APPARATUR FOER STYRD KRISTALLISATIONSPROCESS AV FETT. - Google Patents

Description

74596

Method and apparatus for controlling the fat crystallization process

The invention relates to a process for controlling a fat crystallization process, in which e.g. the crystallization of margarine, butter or chocolate fat generally starts suddenly after a considerable subcooling at a certain temperature, and wherein the crystallization process comprises at least one cooling step to reduce the fat temperature during the crystallization. -10 to make. The invention also relates to an apparatus for carrying out the method.

The main step in the production of margarine is the crystallization of the fat emulsion. The fat emulsion is a recipe mix of several different ingredients. The main ingredients are various 15 dietary fats.

The fat emulsion is flowable and easily pumped at a temperature of typically 50 to 60 ° C. In the manufacture of margarine, the equipment after the manufacture of the fat emulsion is typically a high-pressure pump, a multi-stage heat-20 exchanger for crystallizing and cooling the fat, and packaging machines.

The fat emulsion is crystallized in the first heat exchangers of the cooling stage, in which the ammonia is allowed to evaporate, thereby binding the heat of the flowing fat. In addition to the cooling function, the heat exchanger includes kneading and mixing a strong fat emulsion inside the flow tubes. The latter coolers set the viscosity of the finished margarine to suit. These are usually also evaporator coolers such as 30 initial stage coolers. As the fat emulsion cools and crystallizes, its viscosity rises sharply, and a high-pressure pump is used to transport it through all the coolers. The pump presses the grease emulsion at a maximum pressure of approx. 60 ... 70 bar into the radiator line.

35 The finished margarine often becomes flowable only when the temperature typically rises above 30 ° C. However, with the same 2 74596 fat blend, crystallization only begins when the temperature typically drops below 20 ° C. After this considerable subcooling, crystallization begins abruptly under the same conditions, always at exactly a certain temperature, and is initially quite strong, slowing down after a considerable part of the fat emulsion has crystallized.

It is very important for crystallization that the cooling of the fat is not too rapid at the beginning of crystallization. If a certain temperature characteristic of the fat is rapidly fallen, the high viscosity of the cooled fat prevents rapid crystallization and may take hundreds of times longer than the optimal crystallization. This uncontrolled crystallization can occur, for example, in such a way that the pre-packaged fat products melt in storage as the heat of crystallization is released. This uncontrolled crystallization is usually also associated with a poor crystal structure, and correspondingly, optimal, rapid crystallization gives a good crystal structure. In optimal crystallization with several fat blends, 50-90% of the crystallizing fat crystallizes within 1 to 5 minutes, with 20 complete crystallizations taking several hours, even days.

According to the prior art, in the production of margarine, the control of the crystallization process is performed manually by controlling the ammonia removal valve and thus the vapor pressure in the condenser. The steam pressure and in other words the evaporation temperature control the cooling capacity. Manual adjustment is based on a visual assessment of the quality of the finished margarine. Manual adjustment usually has a delay of a few minutes before an incorrect setting can be corrected. The exact crystallization process is not known, which is why no automation has been possible. In practice, the greatest difficulty relates to measuring the temperature of the fat. If crystallization can begin before the measurement point, the measurement result is also affected by the heat of crystallization released.

35 It is known per se that variations in the temperature of the raw material are particularly critical in the manufacture of margarine. To control crystallization, it is important to keep the temperature of the fat stream 3 74596 constant up to 0.1 ° C. The difficulty of controlling the process is compounded by the required cooling rate; the most important cooling step in terms of crystallization takes only about 10 seconds. In addition, the fat stream leaving the condenser may be inhomogeneous despite intense kneading. For the above reasons, it has not been possible to obtain a reproducible and reliable measurement after the condenser.

It is an object of the present invention to provide a method by which the fat crystallization process can be automatically controlled reliably and efficiently. This is achieved by the means set out in claim 1. Measuring the temperature after the radiator is a major technical problem. Claim 2 discloses an improvement of the method which enables the technical implementation of the crystallization process to be controlled by conventional components. The mere measurement of temperature from a fat stream requires its close continuous monitoring from the start of the process. Said certain temperature may occur in the event of a disturbance, in which case crystallization begins before the measuring point and the heat of crystallization raises the heat to said certain temperature. This difficult monitoring problem is avoided by the improvement of the method set out in claim 3. The density of the fat emulsion is known and possible crystallization is observed as a clear change in density. In this way, density measurement can be used to ensure that crystallization has not begun at the measuring point. The improvement of the method set out in claim 4 further ensures the control of the crystallization process. When the crystallization starts strongly between the temperature measurement points, a temperature difference is then observed due to the release of the heat of crystallization into the fat stream. This measurement of the temperature of a considerably crystallized fat stream is no longer technically as big a problem as the first measurement and can be measured directly from the main stream with conventional ones; 35 measuring devices.

Claims 6 to 8 set out device arrangements for carrying out the method according to the invention and its improvements.

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In the following, the invention is illustrated by means of application examples.

'' UVSI 1 p · i

Trialy crystallization curves ^ 2 Basic equipment arrangement of the crystallization process Figure ·} v · * - o A device arrangement enabling the control of the crystallization process

Figure 1 shows the crystallization of a fat mixture as the fat stream is cooled in stages.

Represents an ideal crystallization that cannot be found faster. The best crystal structure is ^ in achievable. By means of the present invention, the kit can be controlled to take place continuously and in a controlled manner according to curve A. Curve C shows the case where the temperature of p q ^ Van is lowered too fast below said certain temperature, whereby crystallization slows down ^ • apparently when the viscosity of the fat rises too high: Crystallization then does not take place in a controlled manner and takes up to thousands of times longer than ideal crystallization. The crystal structure then also remains poor due to the lack of kneading.

According to the invention, it is important that the initial stage of crystallization, according to the example of Figure 1, crystallization up to 30% takes place with an uncooled flow rate.

Curve B represents some intermediate form of cases A and C

Between 25.

Figure 2 shows the equipment of the crystallization process for the production of margarine. The grease emulsion enters the suction side 1 of the pump 2, typically at a temperature of about 50 ° C. The high pressure pump 2 presses the fat emulsion and the crystallized fat through the coolers 30 3 and 11 onto the packaging machine. The most important step in the whole crystallization process is the cooling step just before crystallization was typically cooling to about 20 ° C. The condenser 3 is an ammonia evaporator in which the fat emulsion cools in the flow tube 4 as the heat is transferred to the evaporating ammonia. The cooling capacity can be adjusted by adjusting the evaporation pressure by means of valve 6.

The flow tubes 4 have a strong mixing and shaping.

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The liquid level of ammonia is adjusted to a suitable point in the radiator by means of a float valve 5> 12.

Controlled crystallization is achieved by adjusting the temperature of the fat emulsion after the condenser 3 to the initial temperature of crystallization 5, whereby a strong initial stage of crystallization takes place in the uncooled tube section 10. The viscosity of the fat can then be adjusted as desired by the condenser 11.

The temperature control is in principle carried out by measuring the temperature of the fat stream leaving the condenser 3 with a suitable sensor 9 and controlling the ammonia vapor removal valve 6 on the basis thereof by means of a control device 8.

There are difficulties in the technical performance of the temperature measurement. These difficulties can be avoided in the embodiment of Figure 3, where the temperature is measured after the cooler from the recirculated side stream. The pipe 13 thinner than the main flow pipe 10 is connected immediately after the radiator 3 and at one end to the suction side of the pump 2. The side flow in the pipe 13 is aimed to be stabilized.

A temperature density sensor 14 is also installed in connection with the temperature sensor 9. · This is connected to a display and alarm device 15 · The alarm limit is set to a small deviation from a value corresponding to the density of the fat emulsion at said certain temperature. If, for some reason, crystallization can already start in the radiator 3> the alarm device 15 gives a notification. The density of the crystallized fat is substantially lower than that of the fat emulsion.

The second system for monitoring the crystallization process consists of a temperature measuring sensor 16 with its transmitter and a display and alarm device 17. If crystallization occurs normally and thus a strong onset of crystallization occurs in a part of the pipe 10, a clear rise in fat flow temperature is observed along the pipe 10. The alarm limit can be set to 35 process and raw material dependent temperatures.

The accuracy requirement for temperature control is very high. In practice it has been found ammonia feed side of disorders mediated by the whole process. With these pressure control devices 19, 74596 which control the valve 18, these losses can be eliminated; by stabilizing the inlet pressure for the level control valve 5 · The device arrangements in Fig. 3 can also be used to retrieve the control values for the crystallization of an unknown fat mixture. This 5 can take place, for example, as follows. The setpoint of the temperature control device 8 is lowered, for example, by 2 ° C at a time until the density measuring devices 14 and 15 indicate that a crystallization point has been found. Using smaller changes in the setpoint, the exact final temperature setpoint 10 is then retrieved by searching for the maximum temperature difference along the path of the tube 10 by monitoring the display devices of the temperature sensors 14 and 16.

If a certain temperature is known, it can be injected directly into the setpoint of the temperature controller 8. However, fine tuning may need to be done as described above.

Claims (9)

A method for controlling a fat crystallization process, wherein e.g. the crystallization of margarine, butter or chocolate fat generally starts suddenly after a considerable subcooling at a certain temperature, and wherein the crystallization process comprises at least one condenser (3) for lowering the fat temperature to initiate crystallization, characterized in that the initial phase is mainly timed to take place after the cooling step (4) by an uncooled flow rate 11a (10) by adjusting the temperature immediately after the cooler (3) to said certain temperature so as to measure this temperature or a corresponding quantity to control (6) the cooler (3) cooling capacity. Method according to claim 1, characterized in that the temperature (9) is measured from a recirculating side stream (13) after said cooler (3). Method according to Claim 2, characterized in that, in addition to the measurement of the temperature of the fat (9), the density of the fat is measured (14) at substantially the same point. Method according to Claim 2 or 3, characterized in that the temperature of the fat (16) is measured in time from the main stream after the first measurement (9), e.g. in the case of margarine fat 0.1 to 60 seconds after the side flow measurement (9). to detect. 35 Method according to one of the preceding claims 1 to 4, in which the cooling takes place in the condenser (3) by evaporating ammonia or the like, characterized in that the vapor pressure of ammonia or the like is used as the indirect control variable. Apparatus for carrying out the method according to claim 2, comprising a high-pressure pump (2) for conveying the fat emulsion and crystallized fat through the piping and having one or more stages of ammonia or a corresponding evaporator cooler (3, 11), characterized in that the apparatus comprises a main flow pipe. a branch (1) branching side pipe (13), one end of which is connected immediately after the crystallization initiator (3) and the other end of the pump (2) on the suction side (1), and a temperature or similar measuring device connected to the side flow pipe (13) (9), and a control device (8) which, on the basis of the temperature of the side stream (13) or a corresponding measurement result, controls the ammonia flow outlet valve (6) of the radiator (3) to keep the temperature at said certain value. 20 Apparatus according to claim 6, characterized in that the apparatus comprises a density measuring sensor (IA) mounted in the side flow tube (13) at substantially the same position as the temperature measuring sensor. 25 Apparatus according to claim 6 or 7, characterized in that a second temperature measuring sensor (16) is arranged in the main flow pipe (10) substantially after the connection of the side flow pipe (13) before the next cooler (11), which is adapted to measure the normally significantly crystallized fat temperature. 35 9 Patentkrav 74 5 96