FALLING FILM CONCENTRATOR

Abstract: A falling film concentrator composed of alternately stacked feedstock plates (10) and steam plates (20) for concentrating a highly heat-sensitive liquid feedstock at a high concentration ratio with heating steam without impairing its flavor and quality, in which the width of a heating flow passage (18) is gradually reduced from an inlet (12) for the feedstock toward an outlet (13) for the concentrated liquid. Thus, no scorch occurs even when the feedstock is reduced in quantity after the water contained therein has been evaporated and separated therefrom. For preventing the speed of the concentrated liquid flowing toward the outlet (13) from being increased by steam generated from the feedstock, the plate-to-plate distance between the heating flow passages (18) is gradually increased from the feedstock inlet (12) toward the concentrated liquid outlet (13).

Description: The present invention relates to a thin film flow-down type concentrating apparatus, and more particularly to an apparatus for concentrating a raw liquid which is required to be concentrated to a high degree without sacrificing the flavor or deteriorating the quality, such as heat susceptible liquid including fruits (orange, pineapple, tangerine, etc.), vegetables (onion, tomato, etc.), livestock extract (chicken, beef, pork, etc.), and marine products (shrimp, oyster, fish, crab, etc.). When concentrating a heat susceptible liquid, it is necessary to shorten the heat contact time with the steam heating element. It is accordingly desired to take out the raw liquid supplied into the concentrating equipment as a concentrate liquid by one pass. The present inventors previously developed a thin film flow-down type concentrating machine favorable for concentrating a heat susceptible liquid, and internationally applied as WO90/09220. This application had, however, a room for improvement concerning the concentration of the raw liquid that requires a higher degree of concentration. That is, when concentrating a raw liquid to a high degree, a multistep concentration method is employed, and the moisture in the raw liquid is evaporated and removed in steps by the concentration equipment, and the concentration becomes higher and the liquid volume of the raw liquid decreases in the later steps, and the liquid volume becomes extremely small in the final step, and a dry portion appears on the heating surface, which has sometimes led to scorching or deterioration of liquid quality. As this countermeasure, it may be considered to recycle a part of the concentrate to increase the liquid volume only at the final step, but in such a case the flavor is sacrificed in the case of heat susceptible liquid and the quality is lowered, and the concentration efficiency is also decreased. GB-A-1084292 and GB-A-2089666 each disclose a thin film flow-down type concentrating apparatus for concentrating a raw liquid by heated steam by alternately laminating raw liquid plates and steam plates. The width of the raw liquid heating passage from the raw liquid inlet to the concentrated outlet is gradually narrowed. The invention is intended to improve these points, and it is a primary object thereof to present a thin film flow-down type concentration apparatus capable of concentrating to a high degree by one pass. According to the present invention, there is provided a a thin film flow-down type concentrating apparatus for concentrating a raw liquid by heated steam, comprising alternately laminating raw liquid plates and steam plates, each raw liquid plate comprising a raw liquid inlet (12) formed in the upper part of the raw liquid plate a concentrate outlet formed at the lower part of the raw liquid plate and a raw liquid passage extending from the raw liquid inlet to the concentrate outlet, each steam plate comprising a heated steam inlet, drain outlets and a heated steam passage extending from steam inlet to drains, the width of both the heating passage and heated steam passage being gradually narrowed in the flow direction of the liquid, characterised in that an evaporated steam passage, which extends from an intermediate point of the raw liquid plate beneath at least one side of the raw liquid passage until the concentrate outlet is formed, for allowing the steam evaporated from the raw liquid to be separated from the concentrated liquid. An embodiment of the present invention will now be described with reference to the accompanying drawings of which:- Fig. 1 is a front view of a raw liquid steam plate in an embodiment of the invention; Fig. 2 is a front view of a steam plate in this embodiment of the invention; Fig. 3 is a magnified sectional view of line vii-vii of Fig. 2; Fig. 4 is a perspective exploded view showing schematically the constitution of a concentrating machine formed by alternately laminating raw liquid plates and steam plates; and Fig. 5 is a flow sheet showing an example of concentrating equipment using heating plates of the invention. In Fig. 1, numeral 10 denotes a raw liquid plate, which comprises a heated steam passage 11, raw liquid inlet 12, concentrate outlet 13, and drain passages 14. The heated steam passage 11 has an opening formed in the upper middle part of the raw liquid plate 10, and is surrounded with a gasket 15a. The raw liquid inlet 12 is opened slightly above the middle of the vertical direction of the raw liquid plate 10 on the central line in the widthwise direction of the raw liquid plate 10, and it is about 1/5 to 1/9 of the width of the raw liquid plate 10, and is surrounded with a gasket 15b of nearly U-form. This U-form gasket 15b composes a preheating passage 16 of the raw liquid entering from the raw liquid inlet 12, and is designed to uniformly disperse the raw liquid from its upper opening to the dispersion parts 17 at both sides. The concentrate outlet 13 is opened in the lower middle part of the raw liquid plate 10, and its lower circumference is surrounded with a gasket 15c of nearly U-form. From above the raw liquid preheating passage 16 till the concentrate outlet 13 through the dispersion parts 17 at both sides, a raw liquid heating passage 18 is formed. This raw liquid passage 18 is surrounded with a gasket 15d, and the lower end of this gasket 15d does not extend as far as the U-form gasket 15c surrounding the lower circumference of the concentrate outlet 13. The raw liquid passage 18 is gradually narrowed in the width from the raw liquid inlet 12 toward the concentrate outlet 13. Accordingly, the gasket 15d surrounding the raw liquid passage 18 is narrowed in the widthwise interval downward. The drain passages 14 are opened at both sides beneath the raw liquid plate 10 at a lower position than the concentrate outlet 13, and they are surrounded with gaskets 15e. The circumference of the raw liquid plate 10 is surrounded with a frame-shaped gasket 15f, and this frame-shape gasket 15f is formed in series with other gaskets 15a, 15c, 15d, 15e. A plurality of evaporated steam outlets 40 are formed beneath the gasket 15d surrounding the raw liquid passage 18, and an evaporated steam passage 41 is formed beneath the both sides or one side of the raw liquid heating passage 18. This evaporated steam passage 41 communicates with the concentrate outlet 13. As shown in Fig. 1, the plurality of evaporated steam outlets 40 are formed beneath the gasket 15d surrounding the raw liquid passage 18, and the evaporated steam passage 41 is formed beneath the both sides or one side of the raw liquid passage 18, in which the evaporated steam generated when the raw liquid is concentrated to reduce in liquid volume may be separated from the plurality of the evaporated steam outlets 40 into the evaporated steam passage 41 beneath the both sides or one side of the raw liquid passage 18, so that the flow velocity of the concentrate is prevented from increasing. Fig. 3 is a magnified side view showing the forming state of the plurality of evaporated steam outlets 40 composed beneath the gasket 15d, in which the gasket 15d is indicated by hatching. In Fig. 2, numeral 20 denotes a steam plate, which comprises heated steam inlet 21, raw liquid passage 22, concentrate passage 23, and drain outlets 24. The heated steam inlet 21 is opened in the middle of the upper part of the steam plate 20, and its upper half is surrounded with a gasket 25a. The raw liquid passage 22 is opened slightly above the middle of the vertical direction of the steam plate 20 on the central line of the lateral direction of the steam plate 20, and is 1/5 to 1/9 of the size of the lateral direction of the steam plate 20, and it is surrounded with an annular gasket 25b. Also above the raw liquid passage 22, there is affixed a gasket 25c for preventing the plates 10, 20 from deflecting or deforming, correspondingly to the gasket 15b for composing the raw liquid preheating passage 16 of the raw liquid plate 10. The concentrate passage 23 is opened in the middle of the lower part of the steam plate 20, and is surrounded with an annular gasket 25d. The drain outlets 24 are opened at both sides of the lower part of the steam plate 20 at a lower position than the concentrate passage 23. The drain outlets 24 are surrounded with a series of frame-shaped gaskets 25e including the heated steam passage 26 in which the heated steam flowing in from the heating steam inlet 21 above the steam plate 20 flows down toward the drain outlets 24. The heated steam passage 26 is gradually narrowed in the width from the upper part to the lower part of the raw liquid plate 10. Accordingly, the gasket 25e surrounding the heated steam passage 26 is narrowed in the interval in the widthwise direction downward. The steam plate 20 is surrounded with a frame-shaped gasket 25f, but this frame-shaped gasket 25f does not reach the gasket 25e surrounding the heated steam passage 26. The position and size of the heated steam inlet 21, raw liquid passage 22, concentrate passage 23, and drain outlets 24 of the steam plate 20 are matched with the position and size of the heated steam passage 11, raw liquid inlet 12, concentrate outlet 13, and drain passages 14 of the raw liquid plate 10. The lower end of the gasket 25e surrounding the heated steam passage 26 is cut off to be formed in the same shape as the gasket 15d in Fig. 1. Gaskets of uniform thickness may be used without having to vary the thickness of gaskets. In the foregoing raw liquid plates 10 and steam plates 20, the slender ration is about 9:1. A thin film flow-down type concentrating machine is formed by alternately laminating thus composed raw liquid plate 10 and steam plate 20 as shown in Fig. 4, and disposing end plates 31, 32 at both ends. Heated steam is supplied from a heated steam feed port 33 above one end plate 31, and raw liquid is supplied from a raw liquid feed port 34 slightly above the middle in the vertical direction. In consequence, the raw liquid climbs up the preheating passage 16 from the raw liquid inlet 12 of each raw liquid plate 10, and flows down in a thin film along the raw liquid passage 18 by way of the dispersion parts 17 at both sides from above, and is discharged from the concentrate outlet 13. On the other hand, the heated steam flows down in a thin film from the heated steam inlet 21 of each steam plate 20 along the heated steam passage 26, and is discharged from the drain outlets 24. As a result, the raw liquid is preheated in the preheating passage 16 of each raw liquid plate 10 by the heated steam running at both sides, and is heated in the passage 18 to be concentrated, and is discharged from the concentrate outlet 13. In the process of concentration of the raw liquid, the moisture in the raw liquid is evaporated as steam, and the liquid volume decreases accordingly, and if the width of the raw liquid passage 18 is uniform from top to bottom, a dry area may be formed on the heating surface but since the width of the raw liquid heating passage 18 is gradually narrowed from top to bottom, the heating surface is prevented from forming a dry area. On the other hand, the heated steam runs through the heated steam passage 26 of each steam plate 20, and heats the raw liquid running at both sides to condense, and is finally discharged as drain through the drain outlets 24. Since the heated steam is condensed to decrease in volume, the heated steam passage 26 is also gradually narrowed in width downward. In Fig. 4 numeral 35 is a concentrate take-out port, and 36 is a drain take-out port. Fig. 5 is a flow sheet of a concentrating equipment using heating plates of the invention, in which the raw liquid is fed from a tank 50 into a first concentrating machine 54 by a first pump 51 through a first preheater 52 and a second preheater 53, and is concentrated, and separated into gas and liquid by a first separator 55. The concentrate separated from the gas by the first separator 55 is supplied into a second concentrating machine 57 through a second pump 56 to be further concentrated, and of the third concentrating machine 60 is separated into the uncondensed steam and condensed drain by a third drain separator 70. The condensed drain is separated into the uncondensed steam and condensed drain by a fourth drain separator 71, and is supplied as preheat source into the first preheated 52 from a third drain pump 72, and is discharged. The uncondensed steam in the third drain separator 70 is supplied into a cooler 73 together with the separated steam from the third separator 61, and cooled, and is supplied into the fourth drain separator 71. In the fourth drain separator 71, being separated into the uncondensed steam and condensed drain, the condensed drain is supplied as preheat source into the first preheater 52 by the third drain pump 72 and is discharged. The uncondensed steam is supplied into a water tank 75 through a water injector 74. Fig. 5 is an example of application of the invention in a three-step concentrating equipment, in which the heating source of the concentrating machine of the first step is an exclusive heat source, while the heat sources of the second and after concentrating machines may be the steam separated from the raw liquid of the preceding concentrating machine. In this case, the invention may be applied to all concentrating machines, or only to later concentrating machine(s).

Claims: A thin film flow-down type concentrating apparatus for concentrating a raw liquid by heated steam, comprising alternately laminating raw liquid plates (10) and steam plates (20), each raw liquid plate comprising a raw liquid inlet (12) formed in the upper part of the plate (10) a concentrate outlet (13) formed at the lower part of plate (10) and a raw liquid passage (18) extending from the raw liquid inlet to the concentrate outlet, each steam plate (20) comprising a heated steam inlet (21), drain outlets (24) and a heated steam passage (26) extending from steam inlet (21) to drains (24), the width of both the heating passage (18) and heated steam passage (26) being gradually narrowed in the flow direction of the liquid, characterised in that an evaporated steam passage (41), which extends from an intermediate point of raw liquid plate (10) beneath at least one side of the raw liquid passage (18) until the concentrate outlet (13) is formed, for allowing the steam evaporated from the raw liquid to be separated from the concentrated liquid. A thin film flow-down type concentrating apparatus according to claim 1, characterised by a gasket (15d) surrounding the raw liquid passage (18) and formed in series with a gasket (15f) disposed along the outer circumference of the plates and surrounding the evaporated steam passage (41). A thin film flow-down type concentrating apparatus according to claim 2, characterised in that a plurality of steam outlets (40) are formed in the gasket (15d) surrounding the raw liquid passage (18) to connect the passage (18) to the evaporated steam passage (41). A thin film flow-down type concentrating apparatus according to any of claims 1 to 3, characterised in that the raw liquid plate (10) comprises a preheat passage (16) for passing the raw liquid along the central line in the longitudinal direction of the plate (10), and dispersing parts (17) at both sides for dispersing the raw liquid in a uniform thin film toward the right and left sides from the top end of the preheating passage (16), and in that the raw liquid passage (18) allows the raw liquid dispersed by the dispersing parts (17) to flow uniformly in a thin film. A thin film flow-down type concentrating apparatus comprising a plurality of concentrating apparatuses according to any of claims 1 to 3 disposed in pairs with separators for separating concentrated liquid from evaporated steam in multiple stages, wherein the raw liquid is fed from the former stage to later stage sequentially in one pass, the separated steam in the former stage is used as the heating medium of the later concentrating stage in a multiple effect system, a steam injector is used in supplying of heating medium to the first concentrating apparatus, and the raw liquid supplied into the first concentrating apparatus is preheated by the condensed drain of the heating medium generated in the concentrating apparatuses at each stage.

Inventors: MASUTANI KENZO TENNOJI-SANHAIT, SAKAI YOSHIHARU - TSUJI-MACHI, MASUTANI, KENZO, TENNOJI-SANHAITSU 1103, SAKAI, YOSHIHARU, 31-49, TSUJI-MACHI
Applicants: HISAKA WORKS LTD, HISAKA WORKS LIMITED
Application year: 1991
Main classification: B01D1
IPC codes: B01D1, F28F13, F28D9, F28D3