FR2521834A1 - PROCESS AND DEVICE FOR THE MANUFACTURE OF POWDERED MILK - Google Patents

Abstract

IN THE MANUFACTURE OF MILK POWDER, AN EVAPORATOR IS USUALLY USED TO CONCENTRATE THE MILK AND FINISH THE DRYING, FOR EXAMPLE UP TO 4 WATER, IN A SPRAY DRYER. THE EVAPORATOR IS MORE EFFICIENT IN USING STEAM TO EXTRACT WATER CONTAINED IN THE MILK, SO IT IS DESIRABLE TO FEED THE DRYER WITH MILK WHICH IS IN AS HIGH A STATE OF CONCENTRATION AS POSSIBLE. THE INCREASING VISCOSITY OF THE STRONGEST CONCENTRATE ADVERSE THE SPRAYING WHICH IS NECESSARY FOR DRYING. IT WAS NOTED THAT THE MILK HAS A DELAY OF A FEW SECONDS TO THICKEN UNTIL ITS FULL VISCOSITY, AND, TO GET THE ADVANTAGE OF THIS PROPERTY, THE EVAPORATOR HAS A FINAL STAGE 3 DESIGNED FOR A SHORT STAY TIME AND PLACE WITH ITS OUTPUT 5 IMMEDIATELY ADJACENT TO THE INLET OF THE SPRAY DRYER 4. IT IS PREFERRED THAT THE FINAL STAGE 3 IS ASCENDED TO THE TOP OF THE DRYER 4.

Description

PROCESS AND DEVICE FOR THE MANUFACTURE OF POWDERED MILK.

  The present invention relates to the manufacture of

  tion of milk powder, either from whole milk or

  from milk which is partially or totally skimmed.

  Skim milk and whole milk powders are conventionally prepared by first preconcentrating the milk in an evaporator and then passing the concentrate

  in a spray dryer The evaporator is used

  dried to preconcentrate the milk because the energy consumption per unit of water which is withdrawn there is much more

  lower than the energy consumption per unit of water reti-

  sprayed drier.

  It is therefore desirable to limit the water which must be removed in the drying part of the process by concentrating the milk in the evaporator to a percentage of total solids as high as possible. This is illustrated by the fact that in order to produce 100 kilos of

  milk powder at 4% humidity, evapo-

  ration of 92 liters of water in the dryer, if it is fed

  tee with a concentrate at 50> /; 60 liters of water must be removed from the dryer if it is supplied with a% concentrate; and only 47 liters of water should be removed from the

  dryer if fed with a 65% concentrate Cepèn-

  the problem of increasing total solids

  brought to the dryer comes from the increase in viscosity

  concentrate, while solids increase, making it difficult to get a good spray in

  dryer and therefore prevents it from working

satisfactorily.

  The object of the present invention is to allow the extension of the evaporation process to produce higher concentrations at the entrance to the dryer while

  still allowing its satisfactory operation, by obtaining

  thereby reducing energy consumption in the

process in general.

  The invention is based on the surprising discovery

  te that concentrated milk products do not present their maximum viscosity immediately at concentration, but that this develops within a short period of time after concentration. The time taken following the concentration,

  for the development of maximum viscosity in the concentration

  very variable and depends on the actual properties of the milk

  treated and the time of year, and other factors Cepen-

  However, the time taken will certainly be less than 10 seconds.

  des and will probably be between 5 and 7 seconds It is however difficult to be totally specific to this

  subject because, of course, milk is not instantaneously concentrated

  temporarily in an evaporator We discovered that on a

  period of a few seconds after leaving the evaporator

  The milk concentrate has a thickening process.

aging.

  In common practice, milk evaporators are located far enough from the entrance to the dryers they serve, that the time taken to transport the

  evaporator concentrate at the entrance of the dryer is consi-

  grossly greater than that required for the concentrate

develops its maximum viscosity.

  The present invention is therefore based

  on the location of an evaporator which performs the evapora-

  final as close as possible to the entrance to the spray dryer, to allow the concentrate to be brought to the dryer in time for spraying before the

  full viscosity has not developed.

  According to a first aspect of the invention, one pre-

  sees a milk powder manufacturing process in concentrated

  trating the milk in one or more stages of evaporation,

  and passing the concentrate through a spray dryer

  rization for spraying and drying, o a single stage Cu final concentration by evaporation is sufficiently close to the spray dryer and operates with a residence time so short that the concentrate is brought to the

  spray dryer and is sprayed before developing

  per its maximum viscosity, which would be sufficient to interfere with spraying. According to a second aspect of the invention, there is provided a device for the production of powdered milk which comprises an evaporator and a spray dryer, where the evaporator has a final stage designed for a short residence time and is placed with its exit located immediately

  adjacent to the entrance to the spray dryer.

  This, in practice, normally involves mounting the final evaporation stage at the top of the spray dryer chamber, and given the limited headroom available in such a position, construction of the evaporator of low height, such as that using a construction of the type

  with plates and frame, is particularly suitable.

  This evaporator is then used as the final concentration stage, and its close proximity to the dryer atomizer allows very highly concentrated milk to be admitted into the dryer and sprayed before its maximum viscosity develops and, therefore, allows to use

higher concentration.

  The evaporator concerned can be a finishing stage heated separately according to the main evaporator in the process, or, alternatively, it can be integrated into the heating system of the main evaporator as a stage of one of the effects of the latter, or alternatively, a stage in the recompression circuit, if the evaporator is of the mechanical vapor recompression type. Integration in this way with the main evaporator requires considerable lengths of steam ducts to and from the finishing stage, but provided that it is designed appropriately, this characteristic has no detrimental effect on performance

  general and does not limit the ability to obtain

  upper trations in the finishing evaporator

  gration of the finishing floor in this way allows the

  efficient operation of the main evaporator in operation

  tion of the energy use to be applied in equal measure to the finishing stage and, therefore, this makes maximum

  the profit resulting from this improvement.

  Reducing the water extraction in the dryer for a given amount of powder produced, allows an existing dryer with an established capacity for water extraction, to produce more powder, and the described method can be used to useful way therefore to increase

  the capacity of existing dryers.

  To better understand the object of the invention

  tion, we will now describe it, as a pure example

  illustrative, and not limiting, an embodiment

shown in the accompanying drawing.

On this drawing:

  Figure 1 is a diagram of installation

  trant the important points of a manufacturing device

  powdered milk according to one embodiment of the invention

tion; and

  Figure 2 shows a modification of a part

tie of the device of figure 1.

  Referring first to Figure 1, we can

  see a five-effect evaporator to concentrate a feed

  tation of condensed milk arriving through a line 1 The condensed milk is removed through a line 2 to be brought to a finishing stage which is formed by a plate evaporator 3, which is mounted at the top of a dryer chamber 4 by spraying, so that the final concentrated milk, in a conduit 5, is brought directly to the chamber of the spray dryer for its spraying The residence time of the concentrated milk in the plate evaporator 3 is of the order of one second , so that the concentrate does not

  reaches full viscosity before entering chamber 4.

  The multiple-effect evaporator is illustrated as a five-effect evaporator and its arrangement is fairly conventional. It will be understood that although an evaporator with

  five effects is illustrated, this is in no way limiting

  nor the fact that the milk outlet duct 2 comes from

of the third effect.

  The milk supply in line 1 is brought to a first evaporator effect 11, where it is

  heated by steam entering through a thermocompressor

  sor 12 which carries part of the steam from the second effect through a pipe 13 The exhaust pipes

  various effects, for the condensate, are omitted from the drawing.

  The concentrate and the vapor of effect 11 pass through a conventional separator 14 from which the concentrate passes, via a conduit 16, to the second effect 17, and the vapor passes as heating fluid to the same effect.

  the steam from the second effect flows to a separation

  18 and the concentrate passes into the fourth effect 19, while the vapor is partially re-entrained through

  the conduit 13 to the thermocompressor 12 and passes partially-

  Lely in the third effect through a conduit 21 In the fourth effect, the concentrate is further concentrated by the steam from the third effect and it passes through a separator 22, where the concentrate passes into the fifth effect 23 for heating by the steam from from the fourth effect and from the finishing stage 3, which vapor enters via a conduit 24 The concentrate and the vapor coming from the fifth effect 23 pass through the separator 25 and the concentrate returns, via a conduit 26, to the third effect 27, o it is heated by the remaining steam from the second effect The concentrate and the steam from the third effect 27 pass through a separator 28 and the concentrate passes, via line 2, to the final finishing stage 3, while the steam passes partially to the fourth effect 19 through a duct 29 and partially in the form of vapor,

  to the finishing stage by a duct 31 The steam from

  from separator 25 of the fifth effect goes into the

condenser 32.

  The concentrate and the steam from stage 3 of finishing

  sage from the evaporator I plates pass through a separator 33 and the vapor is brought back through the conduit 24, at the fifth effect 23, while the concentrate is extracted by an extraction pump 34 and is evacuated directly into the atomizer of the dryer by spraying through line 5, without significant length of piping The control system is arranged to ensure that the separator 33 will be kept drained by

the extraction pump 34.

  The final concentration stage in the plate evaporator 3 operates on a single pass basis, so that the residence time is very short (of the order of one

  second), in order to advantageously use the thick period-

aging.

  We can see that the finishing stage or

  plate tor 3 works, from the steam point of view, in parallel with the fourth effect 19, but we will understand

  that the invention is not so limited.

  Referring now to FIG. 2, there can be seen an arrangement of a vapor recompression evaporator for a basic concentration, and it will be understood that this arrangement replaces the five-effect evaporator Z and that it feeds a similar arrangement finishing stage

  3 on chamber 4 of the spray drier For fa-

  cility of understanding, the outlet duct of the concentrate from the vapor recompression evaporator is illustrated by the reference numeral 2, while the heating steam going to the finishing stage is illustrated as entering through a duct 31 and steam returning from the floor of

  finishing is illustrated by a conduit 24 In the evaporator

  vapor recompression valve, which is illustrated as having

  three effects, the steam from separator 41 from the third

  sixth effect, with the steam coming from the finishing stage

  ge in the duct 24, is mechanically compressed by a compressor 42 and is used to heat the supply which enters through the duct 1 towards the first effect 43 The proverart steam duct of the compressor is indicated at 44, and it can be seen that the steam duct 31 to the floor

  is connected to conduit 34.

  The concentrate and the steam come from the first effect 43 pass through a separator 45, from which the concentrate and the steam are brought separately to the second effect 46 for a greater concentration. For this effect, the concentrate and the steam are brought by a separator. 47 and again

  the concentrate and the steam so It brought separately to the third

  effect 48 From the separator 41 for this purpose, the concen-

  very is then extracted through line 2 to be directed to

  the finishing stage, while, as indicated above

  above, the steam passes into the compressor 42.

  As before, the condensate conduits

  from effects 43, 46 and 48 are not shown.

  It is understood that the embodiment described above is in no way limiting and may give rise to any desirable modifications, without going out for that.

of the scope of the invention.

Claims (9)

  1 Process for making powdered milk powder   concentrating the milk in one or more stages of evaporator   tion and passing the concentrate through a spray dryer for spraying and drying,   laughed at by the fact that a single or final stage of concentration   tion by evaporation (3) is close enough to the spray dryer (4) and operates with a residence time so short that the concentrate is brought into the spray dryer (4) and is sprayed before developing its maximum viscosity, which could be enough to harm spraying.   2 Method according to claim 1, characterized in that the final evaporation stage (3) is the stage   final concentration of a multi-effect evaporator.   3 Method according to claim 1, in that the final evaporation stage (3)   separate evaporator heated by steam.   4 Method according to claim 1, in that the final stage of evaporation (3)   by mechanical vapor recompression.   Process according to Claim 4, in that the final evaporation stage (3) of an evaporator operating by recompression steam.   characterized is a characterized works characterized is a mechanical stage of 6 Device for the production of milk powder of the type comprising an evaporator and a spray dryer, characterized in that the evaporator has a final stage (3) which is designed for a short residence time and which is placed with its outlet (5) immediately   adjacent to the entrance to the spray dryer (4).   7 Device according to claim 6, character-   laughed at by the fact that the final stage (3) is mounted at the top   spray dryer (4).   8 Device according to one of claims 6   and 7, characterized in that the final stage (3) is   formed by a set of separable plates in a frame.   9 Device according to one of claims 6 to   8, characterized in that the final evaporation stage (3) is the final concentration stage of an evaporator at several effects.   Device according to one of claims 6   to 8, characterized in that the final stage of evaporation   (3) is a separate steam heated evaporator.   11 Device according to one of claims 6 to   8, characterized in that the final stage of evaporation   (3) works by mechanical vapor recompression.   12 Device according to claim 11, charac-   terified by the fact that the final evaporation stage (3) is a stage of an evaporator operating by recompression steam mechanics.