Pipe system including internal heat exchangers

Abstract

A heat exchanger pipe system is provided for transporting viscous fluids, including a plurality of individual heat exchangers designed as pipe elements and having a predefined control temperature and/or pressure distribution along the pipe system and in the cross-section of the pipes. The heat exchangers, which are in the form of pipe elements, are arranged at regular distances in the pipe system. The regular distances are selected in such a manner that a predetermined temperature and/or pressure distribution is maintained along the pipe system, tempering apparatus of a viscous fluid transported in the heat exchanger pipe are arranged in the heat exchangers and optional mixing elements which are used to maintain, in accordance with the pipe cross-section, a predetermined temperature and pressure distribution in the cross section of the pipes, and at least 30% of the length of the heat exchanger pipe system is equipped with heat exchangers.

Claims

1. A heat exchanger pipeline system for transporting a viscous fluid, comprising: a heat exchanger pipeline configured for transporting the viscous fluid, the viscous fluid having a viscosity of at least 500 Pas: a plurality of heat exchangers that are serial pipeline components positioned at regular intervals in said heat exchanger pipeline and selected to maintain a predetermined temperature and pressure distribution along said heat exchanger pipeline, wherein the plurality of heat exchangers each include an internal diameter, wherein the internal diameter of a first heat exchanger of the plurality of heat exchangers is greater than the internal diameter of a second, successive heat exchanger of the plurality of heat exchangers; a temperature controller in the heat exchangers for controlling a temperature of the viscous fluid; and mixing components configured to maintain at least one of the predetermined temperature and pressure distribution in a cross section of the heat exchanger pipeline, wherein at least 30% of a length of said heat exchanger pipeline is equipped with the heat exchangers.

2. The heat exchanger pipeline system according to claim 1, wherein the temperature controller is a heat-transfer medium pipeline or a heat-transfer medium jacket.

3. The heat exchanger pipeline system according to claim 1, wherein a ratio of the internal diameter of the first heat exchanger to the internal diameter of the second, successive heat exchanger is 10:9 to 5:1.

4. The heat exchanger pipeline system according to claim 1, further comprising at least one branching component.

5. The heat exchanger pipeline system according to claim 1, wherein an internal diameter of one of the plurality of heat exchangers is at least 90 mm.

6. The heat exchanger pipeline system according to claim 1, wherein the temperature controller is external to the heat exchangers and is a temperature control jacket, wherein the internal diameter of each of the heat exchangers is less than 130 nm.

7. The heat exchanger pipeline system according to claim 1, wherein a predetermined temperature difference in at least one of a cross section and a longitudinal direction of the heat exchanger pipeline is less than or equal to 5 C.

8. The heat exchanger pipeline system C according to claim 1, wherein the mixing components and the temperature controller are in at least one of the plurality of heat exchangers in an interior of the heat exchanger pipeline.

9. The heat exchanger pipeline system according to claim 8, further comprising a jacket, wherein the at least one of the plurality of heat exchangers has guide regions and wound regions.

10. The heat exchanger pipeline system according to claim 1, wherein the heat exchanger pipeline is at least 10 m long.

11. The heat exchanger pipeline system according to claim 1, wherein the temperature controller is accommodated along at least 60% of the length of the heat exchanger pipeline.

12. The heat exchanger pipeline system according to claim 2, wherein less than or equal to 40% of a cross-sectional internal area of each of the heat exchangers is taken up by the heat transfer medium pipeline.

13. A method for transporting a viscous fluid through a heat exchanger pipeline system according to claim 1, wherein the viscous fluid is at least one of a cellulose solution and a biopolymer solution, selected from polysaccharides, proteins, nucleic acids or mixtures thereof.

14. The heat exchanger pipeline system according to claim 1, wherein the viscosity is at least 10,000 Pas.

15. A heat exchanger pipeline system for transporting a viscous fluid, comprising: a heat exchanger pipeline configured for transporting the viscous fluid, the viscous fluid having a viscosity of at least 500 Pas; a plurality of heat exchangers that are serial pipeline components positioned at regular intervals in said heat exchanger pipeline and selected to maintain a predetermined temperature and pressure distribution along said heat exchanger pipeline, wherein the plurality of heat exchangers each include an internal diameter, wherein the internal diameter of a first heat exchanger of the plurality of heat exchangers is greater than the internal diameter of a second, successive heat exchanger of the plurality of heat exchangers; a temperature controller in the heat exchangers for controlling a temperature of the viscous fluid; a plurality of pipes in each of the plurality of heat exchangers, wherein the pipes are arranged in wound regions, in which the pipes are wound about each other, and guide regions, in which the pipes are substantially straight, wherein the guide regions separate the wound regions, and wherein at least 30% of a length of said heat exchanger pipeline is equipped with the heat exchangers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is illustrated further by means of the following figures and examples, without being limited to these specific embodiments of the invention.

(2) FIG. 1 shows a longitudinal section through a heat exchanger 1 according to the invention with an external jacket 2 and an inner region 3 and internal coolant pipelines 4, which have guide regions 5 in the direction of the jacket and wound regions 6.

(3) FIGS. 2a, 2b and 2c show three sections through a heat exchanger according to the invention, two normal longitudinal sections, FIG. 2a (Section A-A) and FIG. 2b (Section B-B) and a cross section, FIG. 2c (Section C-C) with two crossed coolant pipelines in a wound region in each case. The coolant pipelines are connected to one another by means of connecting pipelines 7, so that the coolant can be returned in each second coolant pipeline. Likewise shown are a coolant inlet 8 and outlet 9.

(4) FIG. 3 shows a cross section through a heat exchanger 1 with four crossed coolant pipelines 4 in a wound region 6 in each case.

(5) FIG. 4 shows a heat exchanger pipeline branched by fluid divider 10, wherein individual pipeline sections are connected via bent parts 11.

(6) FIG. 5 shows a comparison of the temperature gradients in a conventional fluid pipeline system, as described in WO 94/28213 A1, and the temperature check according to the invention. The one polymer (cellulose) temperature scatter in sections of a transport pipe, which is not a heat exchanger, is shown. The course of the curve (a) describes the average temperature course such that following solution production, the polymer compound is cooled via a heat exchanger, is subsequently fed into a pipe and transported for processing (extrusion). The pressure losses resulting as a consequence of mass transport and also filtration and diverse deflections lead to heat being introduced into the polymer compound by means of the friction, as a result of which, the temperature level as a whole is raised. The curves Bpipe centreand Bpipe wallrepresent an analysis of the teaching according to WO 94/28213 A1, according to which, only the wall of a pipe is cooled. It can be seen that the temperature inhomogeneity increases with distance from the solution production to processing, thus over the transport in the pipe, which can be expressed in a spread of the two curves (B) and (B). WO 94/28213 A1 teaches that a temperature spread of up to 15 C. can occur owing to the pipe system, which is autonomous with respect to temperature and heat management. It becomes clear from the teaching of WO 94/28213 that large viscosity differences are set and build up due to the permitted temperature spread in the conveyed polymer or cellulose solution. If this temperature and viscosity homogeneity is not overcome, then production faults inevitably occur at the downstream processing positions for moulded products, which faults have the effect that extrudates tear off during spinning or extrusion, adhere to other extrudates and as a result unusable end products are created.

(7) FIG. 6 shows the temperature curve of cellulose solutions in various plant configurations, wherein 3 different temperature curves (C, D, E) are illustrated.

(8) (C): After the solution production of the cellulose polymer solution, the transfer of the compound to a filter, passing through the filter and also further transfer for processing to form a moulding (extrusion) are carried out. In the case of the course of the curve C, only the dissipation heat of the heat exchanger is dissipated.

(9) (D): After the solution production of the cellulose polymer solution, the transfer of the compound to a filter, passing through the filter and also further transfer for processing to form a moulding are carried out. In the case of the course of the curve D, not only the dissipation heat of the heat exchanger is dissipated, which here contributes to temperature and viscosity homogeneity, but rather also the dissipation of that caused by pressurisation pumps and also the heating caused by the filtration is dissipated.

(10) As can be seen from curve (D), a temperature and viscosity homogeneity is achieved over the transport path, over the entire heat exchanger pipeline cross-sectional area and also over the heat exchanger pipeline volume. In addition, a homogenisation of the compound temperature is achieved over the entire heat exchanger pipeline course.

(11) (E): With the system according to the invention, the control of the fluid temperature can also be undertaken in such a manner that in the event of a desired temperature increase of the fluid, the heat exchanger pipeline is dimensioned in such a manner with respect to pressure loss, that the desired temperature increase is introduced at the heat exchanger by means of frictional heat. Due to the constructive design of the heat exchanger pipeline as an indirectly guided heat exchanger, in addition to the heat introduced at the heat exchanger by means of friction, heat for increasing the temperature of the cellulose solution can also be introduced by means of a heat exchanger fluid fed to the heat exchanger pipeline.

(12) FIG. 7 shows a calculation of heat to be dissipated as a function of the heat exchanger diameter/surface.

(13) In addition, selected regions are specified with regards to heat flow density of individual heat exchangers, wherein optimum regions for different heat exchangers lie in region 1: pure static mixers in the interior with external temperature control by means of temperature control means on the jacket of the heat exchanger in region 2: pipe static mixers with internal temperature control in region 1, 2: region, in which static mixers or alternatively pipe static mixers lie. The line min. heat flow density shows the minimum heat to be dissipated, in order e.g. to remove frictional heat arising by means of the pipe and the mixer in the cellulose/NMMO/water fluid mixture at a set temperature of 95 C. The solid line shows the optimally dissipated heat quantity.

(14) FIG. 8 shows the cross-sectional temperature profiles for pipes without a heat exchanger, through which fluid flows. FIG. 8a: Pipe with 25 mm diameter; FIG. 8b Pipe with 100 mm diameter. The temperature curves from top to bottom show the profile 1) at the inlet, b) after 1 m, c) after 3 m, and d) at the outlet (after 10 m).

DETAILED DESCRIPTION

Examples

(15) According to these examples, a heat exchanger pipeline as illustrated in FIG. 2 is used. In this form, a heat exchanger contains four coolant pipelines, wherein in each case two are attached at the end for returning the coolant. At the other end, connectors for introducing and draining the coolant are provided. The heat exchanger interior is open at both ends and enables the connection of further heat exchangers or other components, such as connecting pieces, flow dividers, filters, pumps, pressure vessels or end devices, such as extruders or the like. Connections of this type are illustrated in FIG. 3. The coolant pipelines are accommodated in the interior of the heat exchanger, wherein in each case two have wound regions with crossed pipeline loops in the same section or as a consequence have guide regions in the direction of the jacket in a further section. These regions change alternately. Offset thereto is a further pair of coolant pipelines, which both have wound regions and non-wound regions likewise in the same sections, wherein with reference to the first cooling pipeline pair, these wound and non-wound regions are present in a mirrored manner.

Example 1

(16) A heat exchanger pipeline according to FIG. 3 with a cellulose/NMMO/water solution was tested during operation. A spinning solution made up of various sulphite celluloses (Manufacturer MoDo, Sappi Saiccor), composed of 12.9% cellulose, 76.3% amine oxide (NMMO) and 10.8% water, was produced in a dissolution apparatus at a temperature between 97 C. and 102 C.

(17) At a density of 1200 kg/m.sup.3, the solution had a zero shear viscosity (at 85 C.) of 15,000 Pas. The thus-obtained spinning solution was adjusted to a temperature of 95 C. after the production in a heat exchanger equipped with heated internal static mixer components (Model: Sulzer SMR).

(18) At the heat exchanger output, the temperature of the solution delivered was determined, wherein the following temperatures were measured:

(19) T1=95.8 C.

(20) T2=96.7 C.

(21) T3=96.1 C.

(22) T4=95.2 C.

(23) T5=97.1 C.

(24) It can be seen from the measured temperatures that a temperature difference of approx. 1.9 C. was achieved over the cross section of the heat exchanger.

Example 2Empty Pipe Experiment

(25) Continuing, the cellulose solution delivered from the heat exchanger was conveyed into an empty pipe with internal diameter of 108 mm (length approx. 3 metres).

(26) For further processing, the spinning solution flow was divided into 2 individual flows with empty-pipe internal diameter of 80 mm (length approx. 2 metres).

(27) The empty pipes were externally provided with a temperature-control jacket with a thermal insulation (50 mm insulation thickness) thereabove.

(28) The temperature-control jacket was kept at a temperature of 82 C.

(29) After the transport path in the empty pipes (length 5 metres), the temperature distribution of the spinning solution over the cross section was determined at one of the two outlets (65 mm), wherein the following temperatures were measured:

(30) T1=97.8 C. (measured in pipe centre)

(31) T2=91.7 C.

(32) T3=83.5 C.

(33) T4=89.2 C.

(34) T5=91.1 C.

(35) It can be seen from the measured temperatures that a temperature difference of approx. 14.3 C. was achieved over the cross section of the empty pipe. It is noticeable that in spite of the low jacket temperatures, a very high core temperature was measured, which can be explained by a pronounced shear heating of the fluid.

Example 3Heat Exchanger with Heated Internal Static Mixer Components

(36) The invention is set the goal of having to keep the temperature and viscosity constance of the spinning solution at a uniform level over the course of the pipe, in spite of the thermostatting from outside and the entry of shear heat. In order to achieve this, the above-listed empty-pipe system is replaced by means of a heat exchanger system.

(37) The heat exchanger system consists of at least mutually connected heat exchangers.

(38) The first heat exchanger (housing internal diameter 108 mm, length 3 m) consisted of a housing with heated internal static mixer components (Model: Sulzer SMR). The temperature control jacket of the housing was connected to the internal static mixer components, wherein the temperature of the temperature control medium has been set to 92 C.

(39) The internal static mixer components had a length of 2 m (approx. 65% of the housing length).

(40) Downstream of the first heat exchanger component, the spinning solution was subjected to a temperature measurement, wherein the following temperatures are set after passage through the heat exchanger:

(41) T1=94.8 C.

(42) T2=94.4 C.

(43) T3=95.1 C.

(44) T4=95.6 C.

(45) T5=95.9 C.

(46) It can be seen from the measured temperatures that a temperature difference of approx. 1.1 C. was achieved. It is noteworthy that by means of the design according to the invention, a very uniform spinning solution can be set with respect to temperature and viscosity distribution and at the same time, the shear heating of the fluid induced in the heat exchanger system can be dissipated.

Example 4Heat Exchanger with Internal Static Mixer Components

(47) After the distribution of the spinning solution flow, the cellulose solution was transported via 2 structurally identical heat exchangers connected in parallel.

(48) Both heat exchangers (housing internal diameter 85 mm-length 2 m) consisted of a housing with internal static mixer components (Model: Sulzer SMXL). The temperature-control jacket of the housing was set to a temperature of 90 C.

(49) The internal static mixer components had a length of 1.2 m (approx. 60% of the housing length). Downstream of one of the two heat exchanger components, the spinning solution was subjected to a temperature measurement, wherein the following temperatures are set after passage through the heat exchanger:

(50) T1=95.3 C.

(51) T2=96.7 C.

(52) T3=95.4 C.

(53) T4=96.1 C.

(54) T5=95.5 C.

(55) It can be seen from the measured temperatures that a temperature difference of approx. 1.4 C. was achieved. It is noteworthy that by means of the design according to the invention, a very uniform spinning solution can be set with respect to temperature and viscosity distribution and at the same time, the shear heating of the fluid in the heat exchanger system can be dissipated.

(56) Based on the data for the temperature spread, the minimum and optimum heat exchanger lengths in a fluid conveying system were calculated. For a maximum spread of 1.5 C. of a cellulose/NMMO/water fluid at 95 C. in a system made up of 20 individual heat exchangers of 1 m length in each case with staggered internal diameters of 175 mm, 136 mm, 108 mm, 85 mm, and 65 mm, at least 34% of the entire length of the transport system from the first pump to an extruder, is conveyed via a filter and a further pump, a heat exchanger. Within the individual heat exchanger components, it is not the entire length that is provided with a heat-transfer medium pipeline, rather, considering connecting pieces and if appropriate incomplete equipment, with heat exchangers with 175 mm internal diameter, 56.9% of the length, optimally 73.1% of the length is provided with heat-transfer medium. In heat exchangers with 136 mm internal diameter, 69.2% of the length, optimally 85.8% of the length is provided with heat-transfer medium. In heat exchangers with 108 mm internal diameter, 61.7% of the length, optimally 86.7% of the length is provided with heat-transfer medium. In heat exchangers with 85 mm internal diameter, 63.6% of the length, optimally 84.1% of the length is provided with heat-transfer medium. In heat exchangers with 65 mm internal diameter, 50.0% of the length, optimally 75.0% of the length is provided with heat-transfer medium.

(57) Heat exchangers with 175 to 108 mm internal diameter are internally temperature controlled, heat exchangers with internal diameters of 85 to 65 mm are externally temperature controlled with internal static mixers.

(58) For the entire length of the heat exchanger system, based on the sum of the length portions of the heat exchangers, 61.5% of the length, optimally 81.0% of the length is provided with heat-transfer medium. In the case of required distribution components, filters and pumps, 97.1% of the length can be provided with heat-transfer medium.

Example 5

(59) A polymer solutionto be used as a spinning solution and with the following compositionwas transferred from spinning solution production through to processing of the same at a spinning machine through a heat-exchanger pipeline system consisting of heat exchangers and connecting pieces with rupture components (as distribution pieces).

(60) The spinning compound consisting of a mixture of cellulose of the type MoDo Crown Dissolving DP 510-550 and Sappi Saiccor DP 560-580 were produced continuously with the following composition, cellulose 12.9%; amine oxide (NMMO) 76.3%; water 10.8%.

(61) The solution production took place after aqueous enzymatic pretreatment and suspension production by evaporating excess water under vacuum in a continuously perfused reaction vessel at a temperature of 97 to 103 C. had taken place. Known stabilisers were added to stabilise the solvent NMMO/water. The stabilisation of the cellulose solution takes place, as is known, using propyl gallate. For safety-conscious solution production, the heavy metal ion content is checked and a value of 10 ppm as sum parameter (made up of metal ions and noble metal ions) is not exceeded.

(62) The density of the solution produced is 1,200 kg/m.sup.3 at room temperature. The zero shear viscosity of the spinning compound set by means of the cellulose mixing components can be up to 15,000 Pas, measured at 75 C. Depending on the processing temperature chosen in the spinning process, the zero shear viscosity can shift in the range from 500 to 15,000 Pas. Due to the structurally viscous behaviour of the spinning solution, the viscosity falls for spin shear rates, depending on the chosen processing temperature, to a range of below 100 Pas and is likewise heavily dependent on the cellulose concentration in the spinning solution.

(63) At the connecting piece, polymer compound was removed for temperature measurement and viscosity measurement at sampling openings during the passage, wherein the rupture discs attached in the connecting piece were dimensioned for a specific throughflow per mm.sup.2.

(64) TABLE-US-00001 Spec. Rupture disc Viscosity Sampling dimensioning kg deviation opening polymer Temperature .sub.0 in via compound/mm.sup.2 deviation Viscosity .sub.0 Pas at distribution rupture Temperature +/ in in Pas 90 C. piece disc area C. C.* at 90 C. +/ Reactor 0.11 101.5 2.4 1270 98 Downstream 0.08 96.5 0.8 2080 85 of heat exchanger Downstream 0.05 97.3 1.3 1550 73 of filter Downstream 0.15 95.8 0.9 2200 67 of pump- distribution Distribution- 0.04 91.5 1.1 3650 54 spinning machine

(65) Deviations with respect to temperature and viscosity were determined via 10 individual measurements and by forming the average.

Comparative Example: Simulated Heat Transfer of Viscous Fluids in Pipes without Internal Heat Exchanger

(66) Pipes with temperature checking, as in WO 94/28213 without internal heat exchanger for assessing the heat transfer simulated from the pipe centre to pipe wall for the throughflow of highly viscous fluids (such as cellulose solutions).

(67) The temperature cross section profile was measured at the inlet (length 0 m), after 1 m, 3 m and at the outlet (length 10 m). Pipes with diameters of 25 mm and 100 mm formed the basis of the investigation. Flow speeds in accordance with typical values for highly viscous media were chosen (1.13 m/min for diameter 25 mm and 3.54 m/min for diameter 100 mm). At the inlet of the measuring region, the speed distribution is imposed constantly over the cross section as a plug. The simulations are all carried out in a laminar manner. The wall temperature was 152.7 C. for the pipe with 25 mm, and 129.9 C. for the pipe with 100 mm diameter (according to WO 94/28213). The density of the fluid was 1200 kg/.sup.3, the heat capacity was 2700 J/kgK and the thermal conductivity was modelled as linear function of the temperature (0.23 to 0.24 W/mK).

(68) In a first calculation pass, the possibility of influencing the fluid temperatures by means of the diameter of the pipe without heat input (not decomposition reaction in the fluid) was simulated.

(69) The cross-sectional temperature profile of the pipe with 25 mm is depicted in FIG. 8a. The temperature curves from top to bottom show the profile 1) at the inlet, b) after 1 m, c) after 3 m, and d) at the outlet (after 10 m). It is evident that, by means of the jacket, the pipe can also be cooled in the pipe centre.

(70) The cross-sectional temperature profile of the pipe with 100 mm is depicted in FIG. 8b. The temperature curves are shown analogously to FIG. 8b, wherein the differences can only also be seen at the edge region of the pipe. It is evident that, by means of the jacket, the pipe cannot be cooled in the pipe centre. The core temperature of the fluid can be influenced by the wall temperature which is lower by approx. 15 C.

(71) Consequently, for fluids of this type, an alternative cooling and thorough mixing is required, as was provided according to the present invention.