METHOD FOR HEATING A CONCENTRATE FOR SPRAY DRYING AND AN ASSOCIATED INSTALLATION

Abstract

A method for heating a concentrate in an installation for spray drying comprises increasing a pressure of the concentrate from a low pressure level at a flow temperature to a high pressure level. The concentrate is heated at a high pressure level to a spraying temperature using a high-pressure heat exchanger. The concentrate is shear loaded using a shearing device and immediately transferring the concentrate to a location of pressurized spraying, wherein a transfer time for the immediate transfer is determined by a fluidic effective distance between the shearing device and the location of the pressurized spraying.

Claims

1-10. (canceled)

11. A method for heating a concentrate (K) in an installation for spray drying, the method comprising: (a) increasing a pressure (P) of the concentrate (K) from a low pressure level (p1) at a flow temperature (T1) to a high pressure level (p2), wherein the high pressure level (p2) is a maximum of 350 bar; (b) heating the concentrate (K) at a high pressure level (p2) to a spraying temperature (T3) using a high-pressure heat exchanger, wherein the spraying temperature is 75 to 80 C., and wherein the high-pressure heat exchanger is supplied on a secondary side with a heat-transfer medium (W) comprising a shell-and-tube heat exchanger, the shell-and-tube heat exchanger comprising a plurality of inner tubes configured to direct parallel flows of concentrate (K), wherein the plurality of inner tubes are arranged in a circular ring and on a single circle and together form an inner channel, configured to adjoin the inner tubes in the shape of a circumferential annular space oriented in the flow direction, (c) shear loading (S) the concentrate (K) using a shearing device comprising an outlet-side channel having the shape of an annular space that is connected on one side with the outlet of the circumferential annular space and on the other side with a second high-pressure line section, wherein the circumferential annular space defines an extension length and a length-dependent progression of its channel passage cross-sections, wherein the shear loading occurs during or immediately after treatment according to step (b); and (d) immediately transferring (U) the concentrate (K) treated according to step (c) to a location of pressurized spraying (DZ), wherein a transfer time (t) for the immediate transfer (U) is determined by a fluidic effective distance between the shearing device and the location of the pressurized spraying (DZ).

12. The method according to claim 11, wherein an elevated flow speed (v) of the concentrate (K) during the heating of the concentrate (K) at the high pressure level (p2) is increased by 20-25% in a treatment area that is positioned upstream from the heating.

13. The method according to claim 12, wherein the elevated flow speed (v) during the heating of the concentrate (K) at the high pressure level (p2) is a maximum of 3 m/s.

14. The method according to claim 11, wherein the spraying temperature (T3) is 80 C.

15. The method according to claim 11, wherein the concentrate (K) is treated with a dry material concentration (c) of up to 65% mass percent (65 m %).

16. The method according to claim 11, wherein control parameters for the heating of the concentrate (K) at the high pressure level (p2) are determined using properties of the concentrate (K) and physical edge conditions.

17. The method according to claim 16, wherein the properties of the concentrate (K) are one or more of volumetric flow of the concentrate (K), viscosity, pressure, temperature, and dry matter concentration, and wherein the physical edge conditions are the pressure and temperature at the location of the pressurized spraying (DZ).

18. The method according to claim 17, wherein the control parameters are the high pressure level (p2), the elevated spray temperature (T3), the flow speed (v) during the heating of the high-pressure concentrate (K) and the intensity of the shear loading (S).

19. The method according to claim 18, wherein the control parameters are set by a calibration function generated before or during startup of installation for spray drying.

20. An installation for spray drying comprising: a drying tower with pressurized spray nozzles; a feed tank fluidly connected with an inlet of a high-pressure piston pump via a low-pressure line; a feed pump is positioned along the low-pressure line; a first high-pressure line section configured to fluidly couple an outlet of a high-pressure piston pump with an inlet of a high-pressure heat exchanger; a second high-pressure line section configured to fluidly connect an outlet of the high-pressure heat exchanger to one or more pressurized spray nozzles, wherein a fluidic effective length of the second high-pressure line section is reduced to a structurally feasible minimum size, wherein the high-pressure heat exchanger is a shell-and-tube heat exchanger comprising a plurality of inner tubes through which a concentrate flows in parallel, wherein the plurality of inner tubes are arranged in a circular ring and on a single circle and configured to form an inner channel, and wherein the inner channel is configured to adjoin to the inner tubes in the shape of a circumferential annular space in a flow direction; and a means for shear loading the concentrate (K) is located on an outlet side on the high-pressure heat exchanger and comprises an outlet-side channel comprising an annular-shaped space that is connected on one side with the outlet of a circumferential annular space and on another side with the second high-pressure line section, wherein the outlet-side channel comprises a defined extension length and a defined length-dependent progression of its channel passage cross-sections (AS).

21. The installation according to claim 20, wherein the channel passage cross-sections (AS) are constant over the entire extension length (L).

22. The installation according to claim 21, wherein the channel passage cross-section (AS) corresponds with a total passage cross-section of all inner tubes that are flowed through in parallel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] A more detailed representation of the invention results from the following description and the attached figures in the drawings as well as from the claims. While the invention is realized in the various designs of a method and in the various embodiments of an installation for performing the method, a known method and, starting from this known method, a preferred design of the inventive method are shown schematically in the drawing. A preferred exemplary embodiment of an installation for performing the method with a high-pressure heat exchanger designed as a shell-and-tube heat exchanger is shown in the drawing and described below. In the figures:

[0045] FIG. 1 illustrates a schematic representation of a prior art method for heating a concentrate in an installation for spray drying;

[0046] FIG. 1a illustrates a schematic representation of an embodiment of a method for heating a concentrate in an installation for spray drying according to the invention;

[0047] FIG. 2 illustrates a schematic representation of a prior art installation for performing the method of FIG. 1;

[0048] FIG. 3 illustrates a schematic representation of an installation for performing the method according to FIG. 1a, and

[0049] FIG. 4 illustrates a cross-section view of an embodiment of an outlet-side area of a high-pressure heat exchanger configured as a shell-and-tube heat exchanger.

DETAILED DESCRIPTION OF THE INVENTION

[0050] Prior Art (FIGS. 1 and 2)

[0051] FIG. 1 shows a method for heating a concentrate K in an installation for spray drying 1 (drying installation) according to the prior art, and FIG. 2 shows an installation 1 according to the prior art for performing the known method. Below, the method and the associated installation 1 are covered in parallel based on these two figures. The named temperatures, pressures and the dry material concentration are selected as examples and can deviate upwards or downwards in practice.

[0052] The concentrate K sprayed in a drying tower 2 of the drying installation 1 by a pressurized spraying DZ via pressurized spray nozzles 2a undergoes a stockpiling B in a feed tank 4 (FIGS. 1, 2). The feed tank 4 is connected in a fluid accessible manner via a first line section 12.1 of a low-pressure line 12, in which a feed pump 6 is arranged, with the primary-side inlet of a low-pressure heat exchanger 8, in which a low-pressure heating H1 of the concentrate K from a flow temperature T1=58 C. to an inlet temperature T2=65 to 68 C., which is also still approximately present at the pressurized spray nozzles 2a, is performed. The low-pressure heat exchanger 8 is supplied on the secondary side by means of a heat-transfer medium W, preferably hot water. A high-pressure piston pump 10 is connected on the inlet side via a second line section 12.2 of the low-pressure line 12 with the primary-side outlet of the low-pressure heat exchanger 8 and on the outlet side via a high-pressure line 14 with the pressurized spray nozzles 2a.

[0053] In the high-pressure piston pump 10, a pressure increasing P of the concentrate K from a low pressure level p1 present on the inlet side to a high pressure level p2 generated on the output side, which can reach up to p2=max. 350 bar and with which the pressurized spray nozzles 2a are operated minus the drop in pressure up to the latter, takes place. The concentrate K has a dry material concentration c, which can be for example 52 to 57 mass percent (m %) dry material TS.

[0054] The drying tower 2 has a tower height H up to into its head area, in which the pressurized spray nozzles 2a are arranged. The high-pressure line 14 mainly overcomes this tower height H in the form of a riser. In the case of a tower height for example of H=30 m, the high-pressure line 14 is also at least 30 m long due to the connection lines located upstream and downstream of the riser. In the case of a diameter DN50 of the high-pressure line 14, a volumetric flow for example of 5,000 liters/hour for a first dwell period V1 of the concentrate K with the inlet temperature T2 at the high pressure level p2 and with the dry material concentration c results in an average first dwell time t1 of 42 seconds. The problems associated with the described method according to the prior art were covered above.

[0055] Method and Drying Installation (FIGS. 1a, 3 and 4)

[0056] FIG. 1a shows a method according to the invention for heating a concentrate K in an installation for spray drying 100, and FIG. 3 shows an installation 100 according to the invention for performing this method. Below, the method and an associated installation are covered in parallel based on these two figures. The named temperatures, pressures and the dry material concentration are selected as examples and can deviate upwards or downwards in practice.

[0057] FIG. 1a obviously shows through thicker lines the differences between the method according to the prior art (FIG. 1) and the method according to the invention, and FIG. 3 shows, based on the drying installation 100, how these differences are realized in terms of the device. In instances where they match, the same references were used. Thus, in order to avoid repetitions, the above description for FIGS. 1 and 2 are referenced.

[0058] The high-pressure line 14 (FIG. 3) passes over the primary side of a high-pressure heat exchanger 18, wherein a first high-pressure line section 14.1 of the high-pressure line 14 connects the outlet of the high-pressure piston pump 10 with the inlet of the high-pressure heat exchanger 18, and a second high-pressure line section 14.2 of the high-pressure line 14 connects the outlet of the high-pressure heat exchanger 18 with the pressurized spray nozzles 2a. The high-pressure heat exchanger 18 is supplied on the secondary side with a heat-transfer medium W, preferably hot water. The values selected as examples in FIG. 3 for the low pressure level p1, the high pressure level p2, the flow temperature T1 and the dry material concentration c mainly correspond with those values named in methods according to the prior art and the installation 1 for performing the method (see FIGS. 1, 2).

[0059] In the high-pressure heat exchanger 18, a high-pressure heating H of the concentrate K at the high pressure level p2 to an elevated spraying temperature T3, which can lie in the range of 75 to 80 C., takes place (FIG. 3). Furthermore, a defined shear loading S of the concentrate K is provided in the course of or immediately after the high-pressure heating H at an elevated flow speed v (FIGS. 3, 1a). For this, the high-pressure heat exchanger 18 has means on the outlet side for the defined shear loading of the conveyed concentrate K.

[0060] Since the high-pressure heat exchanger 18 is arranged at the tower height H (FIG. 3), a second dwell period V2 of the concentrate K with the flow temperature T1 at the high pressure level p2 and with the dry material concentration c with an average second dwell time t2, which is less than the first dwell time t1 and in the case of otherwise almost identical process data is thus less critical, from now on results in the riser between the latter and the outlet of the high-pressure piston pump 10, i.e. in the first high-pressure line section 14.1.

[0061] An immediate transfer of the concentrate K treated by defined shear loading S is subsequently performed at the location of its pressurized spraying DZ (FIG. 1a), wherein a transfer time t for the immediate transfer is determined by a minimum possible fluidic effective distance between the means for performing the defined shear loading S and the location of the pressurized spraying DZ. The immediate transfer takes place in the correspondingly measured second high-pressure line section 14.2, which is reduced to a structurally feasible minimum size (FIG. 3).

[0062] The method according to the invention is distinguished from the method in the prior art, as shown in a comparison of FIG. 1 with FIG. 1a, and FIG. 2 with FIG. 3, in terms of the method by forgoing the low-pressure heating H1 (FIG. 1a) and therefore in terms of the device by forgoing the low-pressure heat exchanger 8 (FIG. 3). The high-pressure heat exchanger 18 has to handle alone a high-pressure heating H of the flow temperature T1 (for example 58 C.) to the elevated spraying temperature T3 (for example max. 80 C.), whereby an increase in the output of the drying tower 2 is achieved without quality losses.

[0063] It is critical compared to the method according to the prior art that in the case of the method according to the invention the first high-pressure line section 14.1 mainly formed by the riser is flowed through over its entire length with the flow temperature T1 (for example 58 C.), which is not critical with respect to the inlet temperature T2 (for example 65 to 68 C. in the case of the method according to the prior art). The second retention period V2 of the concentrate K with the flow temperature T1 at the high pressure level p2 and with the dry material concentration c with the average second dwell time t2 is thus completely non-critical from a technical perspective.

[0064] The high-pressure heat exchanger 18 is configured as a shell-and-tube heat exchanger with a plurality of inner tubes 20 (FIG. 4), through which the concentrate K flows in parallel. Referring to FIG. 4, the inner tubes 20 are arranged in the shape of a circular ring and on a single circle 26 and together form an inner channel 20*, which adjoins to the inner tubes (20) in the shape of a circumferential annular space (22) in the flow direction. The means for the defined shear loading of the conveyed concentrate K is arranged on the outlet side on the shell-and-tube heat exchanger 18 and comprises an outlet-side channel 24 having an annular shape that is connected on one side with the outlet of the circumferential annular space 22 and on the other side with the second high-pressure line section 14.2 (FIG. 3). The annular-space-shaped, outlet-side channel 24 has a defined extension length L and a defined length-dependent progression of its channel passage cross-sections AS and, just like the inner tubes 20, is also flowed through by the concentrate K with an elevated flow speed v.

REFERENCE LIST OF USED ABBREVIATIONS

FIGS. 1, 2 (Prior Art)

[0065] 1 Drying installation (installation for spray drying) [0066] 2 Drying tower [0067] 2a Pressurized spray nozzle [0068] 4 Feed tank [0069] 6 Feed pump [0070] 8 Low-pressure heat exchanger [0071] 10 High-pressure piston pump (homogenizer) [0072] 12 Low-pressure line [0073] 12.1 First line section [0074] 12.2 Second line section [0075] 14 High-pressure line [0076] H Tower height [0077] c Dry material concentration (in mass percent (m %) dry material (TS)) [0078] t1 First dwell time [0079] Temperatures [0080] T1 Flow temperature (approx. 58 C.) [0081] T2 Inlet temperature (approx. 65-68 C.) [0082] Pressures [0083] p1 Low pressure level [0084] p2 High pressure level (<350 bar) [0085] Substances [0086] K Concentrate (product) [0087] TS Dry material [0088] W Heat-transfer medium [0089] Method Steps [0090] B Stockpiling [0091] DZ Pressurized spraying [0092] H1 Low-pressure heating [0093] P Pressure increasing [0094] V1 First dwell period

FIGS. 1a, 3, 4 (Invention)

[0095] 100 Drying installation (installation for spray drying) [0096] 14.1 First high-pressure line section [0097] 14.2 Second high-pressure line section [0098] 18 High-pressure heat exchanger (shell-and-tube heat exchanger) [0099] 20 Timer tube [0100] 20* Inner channel [0101] 22 Circumferential annular space [0102] 24 Outlet-side channel having an annular-shaped space [0103] 26 Circle [0104] AS Channel passage cross-section [0105] L Extension length [0106] t2 Second dwell time [0107] t Transfer time [0108] v Elevated flow speed (at H) [0109] Temperature [0110] T3 Elevated spraying temperature (75-80 C.) [0111] Method Steps [0112] H High-pressure heating [0113] S Shear loading [0114] U Immediate transfer [0115] V2 Second dwell period