METHOD FOR HEATING A CONCENTRATE IN AN INSTALLATION FOR SPRAY DRYING AND INSTALLATION FOR PERFORMING THE METHOD

Abstract

A device for heating a concentrate comprises a drying tower comprises a plurality of pressurized spray nozzles, a feed tank fluidly connected with an inlet of a low-pressure heat, a feed pump, and a high-pressure piston pump connected on an inlet side with the outlet of the low-pressure heat exchanger. A first high-pressure line section of the high-pressure line is configured to connect the outlet of the high-pressure piston pump with the inlet of the additional high-pressure heat exchanger. A second high-pressure line section of the high-pressure line is configured to connect the outlet of the additional high-pressure heat exchanger with the pressurized spray nozzles. A means for defined shear loading of the concentrate is located in an outlet-side channel and comprises an annular-shaped space.

Claims

1-10. (canceled)

11. A method for heating a concentrate (K) in an installation for spray drying, the method comprising: (a) low pressure heating (H1) the concentrate (K) under a low pressure (p1) from a flow temperature (T1) to a spraying temperature (T2); (b) increasing a pressure (P) of the concentrate (K) to a high pressure level (p2); (c) high-pressure heating (H2) the concentrate (K) at the high pressure level (p2) to an elevated spraying temperature (T3), which lies in the range of 75 to 80 C., wherein the high pressure heating is performed via an additional high-pressure heat exchanger supplied on a secondary side with a heat-transfer medium (W) and which is configured as a shell-and-tube heat exchanger having a plurality of inner tubes configured to conduct a parallel flow of the concentrate (K), and wherein the plurality of inner tubes are arranged in a circular ring and on a single circle and which together form an inner channel, configured to adjoin the plurality of inner tubes in a shape of a circumferential annular space in the flow direction; (d) defining a shear loading (S) of the concentrate (K) in during or immediately after the treatment according to step (c), wherein a means for shear loading comprises a channel comprising a shape of an annular space which is connected on one side with an outlet of a circumferential annular space and on another side with a second high-pressure line section, the second high-pressure line comprises a defined extension length and a defined length-dependent progression of its channel passage cross-sections; and (e) immediately transferring () the concentrate (K) treated to a location of pressurized spraying (DZ), wherein a transfer time (t) for the immediate transfer () is determined by a minimum possible fluidic effective distance between a location of the pressure (P) increase of the concentrate (K) to the high pressure level (P2) and the location of the pressurized spraying (DZ).

12. The method according to claim 11, wherein the flow speed (v) of the concentrate (K) during the additional high-pressure heating (H2) is increased by 20 to 25% in a treatment area located upstream from the additional high-pressure heating (H2).

13. The method according to claim 12, wherein the flow speed (v) during the additional high-pressure heating (H2) is a maximum of 3 m/s.

14. The method according to claim 11, wherein the high pressure level (p2) is a maximum of 350 bar.

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

16. The method according to claim 12, wherein the concentrate (K) is treated with a dry material concentration (c) of up to maximum of 65% mass percent (65 m %).

17. The method according to claim 11, further comprising determining control parameters for the additional high-pressure heating (H2) by properties of the concentrate (K) to be heated and physical edge conditions, wherein the properties of the concentrate (K) to be heated are its volumetric flow, viscosity, pressure, temperature and dry material concentration, wherein the physical edge conditions are the pressure and temperature at the location of the pressurized spraying (DZ), wherein the control parameters of the concentrate (K) are the high pressure level (p2), the spray temperature (T3), the flow speed (v) during the additional high-pressure heating (H2) and intensity of the shear loading (S), and wherein the control parameters are set by a calibration function.

18. A device for heating a concentrate, the device comprising: a drying tower comprising a plurality of pressurized spray nozzles, a feed tank fluidly connected with an inlet of a low-pressure heat exchanger via a first line section of a low-pressure line, a feed pump positioned in the along the first line section of the low pressure line, and a high-pressure piston pump connected on an inlet side with the outlet of the low-pressure heat exchanger via a second line section of the low-pressure line and connected on the outlet side with the pressurized spray nozzles via a high-pressure line, wherein the high-pressure line is guided via an additional high-pressure heat exchanger configured as a shell-and-tube heat exchanger having a plurality of inner tubes, through which the concentrate (K) flows in parallel and which are arranged in the shape of a circular ring and on a single circle which together form an inner channel that adjoins the inner tubes in the flow direction in the shape of a circumferential annular space; a first high-pressure line section of the high-pressure line is configured to connect the outlet of the high-pressure piston pump with the inlet of the additional high-pressure heat exchanger; a second high-pressure line section of the high-pressure line is configured to connect the outlet of the additional high-pressure heat exchanger with the pressurized spray nozzles; a fluidic effective length of the second high-pressure line section is reduced to a structurally feasible minimum size, and a means on the outlet side for defined shear loading of the concentrate (K) located in an outlet-side channel and comprising an annular-shaped space, which is connected on one side with the outlet of the circumferential annular space and on the other side with the second high-pressure line section, wherein the outlet-side channel has a defined extension length (L) and a defined length-dependent progression of its channel passage cross-sections (A.sub.s).

19. The device according to claim 18, wherein the channel passage cross-sections (A.sub.s) are constant over the defined extension length (L).

20. The device according to claim 19, wherein the channel passage cross-sections (A.sub.s) correspond with a total passage cross-section of all inner tubes that are flowed through in parallel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] 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 configured as a shell-and-tube heat exchanger is shown in the drawing and described below. In the figures:

[0062] FIG. 1 illustrates a schematic diagram of a method for heating a concentrate in an installation for spray drying according to the prior art;

[0063] FIG. 1a illustrates a schematic diagram of an embodiment of a method for heating a concentrate in an installation for spray drying according to the invention;

[0064] FIG. 2 illustrates a schematic representation of an installation according to the prior art for performing the method according to the prior art according to FIG. 1;

[0065] FIG. 3 illustrates a schematic representation of an installation for performing the embodiment of the method according to FIG. 1a; and

[0066] FIG. 4 illustrates a meridian section 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

Prior Art (FIGS. 1 and 2)

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

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

[0071] 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 the 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.

[0072] As shown by a comparison of FIG. 1 with FIG. 1a and FIG. 2 with FIG. 3, the method according to the invention further develops the method according to the prior art described above and the known installation 1 for performing the method. 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.

[0073] 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.

[0074] The high-pressure line 14 (FIG. 3) passes over the primary side of an additional high-pressure heat exchanger 16, 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 additional high-pressure heat exchanger 16, and a second high-pressure line section 14.2 of the high-pressure line 14 connects the outlet of the additional high-pressure heat exchanger 16 with the pressurized spray nozzles 2a. The additional high-pressure heat exchanger 16 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, the inlet temperature T2 up to the additional high-pressure heater 16 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).

[0075] In the additional high-pressure heat exchanger 16, an additional high-pressure heating H2 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 additional high-pressure heating H2 at an elevated flow speed v (FIGS. 3, 1a). For this, the additional high-pressure heat exchanger 16 has means on the outlet side for the defined shear loading of the conveyed concentrate K.

[0076] Since the additional high-pressure heat exchanger 16 is arranged at the tower height H (FIG. 3), a second dwell period V2 of the concentrate K with the inlet temperature T2 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.

[0077] 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).

[0078] A critical advantage results compared to the method according to the prior art among other things in that, in the case of the method according to the invention, the concentrate K is supplied to the pressurized spray nozzles 2a with a higher spray temperature, namely the elevated spray temperature T3=75-80 C., by the additional high-pressure heating H2, whereby an increase in the output of the drying tower 2 is achieved without quality losses.

[0079] The additional high-pressure heat exchanger 16 is configured as a shell-and-tube heat exchanger with a plurality of inner tubes 20, through which the concentrate K flows in parallel (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 16 and consist of an outlet-side channel 24 having an annular shape, which 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. 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 A.sub.s 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)

[0080] 1 Drying installation (installation for spray drying) [0081] 2 Drying tower [0082] 2a Pressurized spray nozzle [0083] 4 Feed tank [0084] 6 Feed pump [0085] 8 Low-pressure heat exchanger [0086] 10 High-pressure piston pump (homogenizer) [0087] 12 Low-pressure line [0088] 12.1 First line section [0089] 12.2 Second line section [0090] 14 High-pressure line [0091] H Tower height [0092] c Dry material concentration (in mass percent (m %) dry material (TS)) [0093] t1 First dwell time

Temperatures

[0094] T1 Flow temperature (approx. 58 C.) [0095] T2 Inlet temperature (approx. 65-68 C.)

Pressures

[0096] p1 Low pressure level [0097] p2 High pressure level (<350 bar)

Substances

[0098] K Concentrate (product) [0099] TS Dry material [0100] W Heat-transfer medium

Method Steps

[0101] B Stockpiling [0102] DZ Pressurized spraying [0103] H1 Low-pressure heating [0104] P Pressure increasing [0105] V1 First dwell period

FIGS. 1a, 3, 4 (Invention)

[0106] 100 Drying installation (installation for spray drying) [0107] 14.1 First high-pressure line section [0108] 14.2 Second high-pressure line section [0109] 16 Additional high-pressure heat exchanger (shell-and-tube heat exchanger) [0110] 20 Inner tube [0111] 20* Inner channel [0112] 22 Circumferential annular space [0113] 24 Outlet-side channel having an annular-shaped space [0114] 26 Circle [0115] A.sub.s Channel passage cross-section [0116] L Extension length [0117] t2 Second dwell time [0118] t Transfer time [0119] v Elevated flow speed (at H2)

Temperature

[0120] T3 Elevated spraying temperature (75-80 C.)

Method Steps

[0121] H2 Additional high-pressure heating [0122] S Shear loading [0123] Immediate transfer [0124] V2 Second dwell period