Industrial Plant, Paper Mill, Control Device, Apparatus and Method for Drying Drying-Stock

Abstract

A method for drying drying-stock includes separating solvent-containing drying stock within a drying unit into a base material and a solvent with the aid of a first heat transfer medium that flows through a first circuit, where after the solvent has been taken up by the first heat transfer medium, the solvent is extracted from the heat transfer medium via heat energy (condensation), where the heat energy is transferred by a heat exchanger with the aid of an evaporation unit to a second circuit and made available to a second heat transfer medium, and where the heat energy is fed in a condensation unit of the heat pump back to the first circuit with the aid of a heat pump.

Claims

1.-17. (canceled)

18. An apparatus for drying drying-stock during production of a fiber mat, the apparatus comprising: a drying unit in a first circuit, a first heat transfer medium being provided for drying the drying stock; a second circuit for a second heat transfer medium, the second circuit comprising a heat pump for feeding heat energy into the first circuit.

19. The apparatus as claimed in claim 18, wherein the second circuit draws heat energy from the first circuit.

20. The apparatus as claimed in claim 18, further comprising; at least one further heat pump for feeding heat energy into at least one of (i) the first circuit and (ii) into the second circuit.

21. The apparatus as claimed in claim 19, further comprising: at least one further heat pump for feeding heat energy into at least one of (i) the first circuit and (ii) into the second circuit.

22. The apparatus as claimed in claim 18, wherein the first circuit and the second circuit are only connected by heat exchangers.

23. The apparatus as claimed in claim 18, further comprising: an evaporation unit for feeding the heat energy from the first circuit into the second circuit.

24. The apparatus as claimed in claim 18, wherein the first circuit comprises a blower.

25. The apparatus as claimed in claim 18, wherein the heat pump is a high-temperature heat pump.

26. The apparatus as claimed in claim 18, further comprising: a condensation unit for feeding the heat energy into the first circuit.

27. The apparatus as claimed in claim 18, wherein the first heat transfer medium for the first circuit comprises one of (i) water vapor and (ii) a mixture of water vapor and air.

28. The apparatus as claimed in claim 18, wherein the heat transfer medium for the second circuit comprises a halogenated hydrocarbon, in particular R1233zd(E) or R1336mzz(Z).

29. The apparatus as claimed in claim 18, wherein the halogenated hydrocarbon is one of R1233zd(E) and R1336mzz(Z).

30. A method for drying drying-stock during production of a cellulose-containing fiber mat, the method comprising: circulating a first heat transfer medium circulates in a first circuit, the first heat transfer medium heating the drying stock and taking up solvent released from the stock; feeding heat energy by a second circuit into the first circuit; and introducing, by a heat pump, the heat energy from the second circuit into the first circuit.

31. The method as claimed in claim 30, wherein the second circuit draws at least a part of the heat energy from the first circuit.

32. The method as claimed in claim 30, wherein at least one further heat pump feeds heat energy into at least one of (i) the first circuit and (ii) into the second circuit.

33. The method as claimed in claim 31, wherein at least one further heat pump feeds heat energy into the first circuit and/or into the second circuit.

34. The method as claimed in claim 30, wherein the first circuit and the second circuit are only connected by heat exchangers.

35. The method as claimed in claim 31, wherein the first circuit and the second circuit are only connected by heat exchangers.

36. The method as claimed in claim 32, wherein the first circuit and the second circuit are only connected by heat exchangers.

37. A control device for at least one of (i) controlling and (ii) regulating the method claimed in claim 30.

38. An industrial plant for production of a base material comprising an apparatus as claimed in claim 18.

39. The industrial plant as claimed in claim 38, wherein the industrial plant comprises one of (i) a paper mill and (ii) a cellulose mill.

40. A paper mill comprising the apparatus as claimed in claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The following describes and explains the invention with reference to figures. The features in the individual figures can also be used by the person skilled in the art to arrive at new embodiments of the invention without departing from the essence of the invention, in which:

[0043] FIG. 1 an apparatus for drying drying stock in accordance with the invention;

[0044] FIG. 2 a simplified apparatus for drying drying-stock in accordance with the invention;

[0045] FIG. 3 a further apparatus for drying drying-stock in accordance with the invention;

[0046] FIG. 4 a pressure-enthalpy diagram of a preferred second heat transfer medium in accordance with the invention;

[0047] FIG. 5 a heat-transfer-temperature diagram of a preferred second heat transfer medium in accordance with the invention; and

[0048] FIG. 6 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0049] FIG. 1 shows an apparatus for drying drying stock GW. The apparatus shows a first circuit 1 for a first heat transfer medium WTl, in particular water vapor. In the first circuit 1, the first heat transfer medium WTl is transported through a drying unit D with the aid of a blower V. Here, the heat transfer medium WTl used is water vapor, preferably with a temperature of between 100° C. and 200° C. The first heat transfer medium has a first temperature Tl before the drying unit D. The first heat transfer medium WTl also has a lower second temperature T2 after the drying unit. The drying unit D is used for drying the solvent-containing drying-stock GW.

[0050] Here, the solvent-containing drying-stock GW comprises, in particular fiber-containing, a solid material G and a solvent W, in particular water. The solvent W is evaporated during drying in the drying unit D and is taken up by the first heat transfer medium WTl. The taking-up of the solvent W by the first heat transfer medium WTl causes the temperature of the first heat transfer medium WTl to be reduced from the first temperature Tl to the second temperature T2. After the drying unit D, the first heat transfer medium WTl is transferred to the evaporation unit HPE. The solvent W is condensed in the evaporation unit HPE and separated from the heat transfer medium WTl. The heat energy Q released on the condensation of the solvent is transferred to the second heat transfer medium WT2 with the aid of the evaporation unit HPE. The evaporation unit HPE is substantially formed as a heat exchanger WT. The first heat transfer medium WTl without the solvent W is further transferred to a condensation unit HPC. The condensation unit HPC transfers the heat energy Q removed from the first heat transfer medium WTl with the aid of the evaporation unit HPE to the first heat transfer medium WTl.

[0051] The (re-)feeding of the heat energy Q into the first circuit 1 occurs with the aid of the second circuit 2. The second circuit 2 is formed as a heat pump WP. The heat pump WP comprises the evaporation unit HPE, a compressor K and the condensation unit HPC. The second heat transfer medium WT2 is used to remove heat energy with the aid of the evaporation unit HPE from the first circuit 1 and, in this way, the solvent W from the first heat transfer medium WTl is condensed. After condensation, the solvent W is removed from the first circuit 1.

[0052] The second circuit 2 is formed as a heat pump WP, in particular as a high-temperature heat pump WP. The heat pump WP is used to transport the heat energy Q from the evaporation unit HPE to the condensation unit HPC. The heat pump WP comprises the evaporation unit HPE, the condensation unit HPC and a compressor K. The compressor K is used to transport the second heat transfer medium WT2 from the evaporation unit HPE to the condensation unit HPC (in gaseous state) and back (in condensed state).

[0053] Both the condensation unit HPC and the evaporation unit HPE comprise a heat exchanger WT. The heat exchanger in the evaporation unit HPE is used to transfer the heat energy Q from the first circuit 1 to the second circuit 2. The heat exchanger WT is used to transfer the heat energy Q from the second circuit 2 back to the first circuit 1.

[0054] The heat exchangers WT are in particular used to transfer heat energy Q from the first heat transfer medium WTl to the second heat transfer medium WT2 and back. The heat exchangers WT are preferably formed as tube-bundle heat exchangers.

[0055] The second heat transfer medium WT2 used is preferably a halogenated hydrocarbon. The heat transfer medium WT2 with the designation R1233zd(E) (CAS number 102687-65-0, chemical designation: l-chloro-3,3,3-trifluoropropene) has been found to be particularly advantageous.

[0056] The first heat transfer medium WTl particularly advantageously has a first temperature T1 of 140° C. to 160° C. before entering the drying unit D.

[0057] After the drying unit D, the first heat transfer medium WTl has a second temperature T2 of 80° C. to 120° C. auf. After the drying unit D, the first heat transfer medium WTl can be a supersaturated water vapor. Before the drying unit D, the first heat transfer medium WTl can be superheated water vapor. The heat pump WP typically comprises a turbine, a compressor or a pump to transport the second heat transfer medium WT2. The heat pump WP further comprises at least one expansion valve (not shown).

[0058] The compressor K in the heat pump WP is advantageously controlled or regulated by a control device SE. The control device SE also comprises inputs for sensors S1, S2, S3. The sensors S1, S2, S3 are used to determine the first temperature T1, the second temperature T2 and optionally to determine the water content of the first heat transfer medium WTl. The sensors can be located at different points in the first circuit 1, in the second circuit 2, in particular in the region of the drying unit D, in the region of the evaporation unit HPE and/or in the region of the condensation unit HPC. The speed of the compressor of the heat pump WP is controlled or regulated depending upon the temperature difference between the first temperature Tl and the second temperature T2. The control device SE can comprise a personal computer with a corresponding interface, a microcontroller or a part of a higher-ranking control device. Advantageously, the control device is formed as a computer program which is installed and executed on a computing unit, in particular a personal computer.

[0059] The dashed lines with the evaporation unit HPE and the condensation unit HPC symbolize that here only heat energy Q from the first circuit 1 is transported into the second circuit 2 (and vice versa) and the heat exchangers WT are typically formed as impermeable to heat transfer media WTl, WT2.

[0060] FIG. 2 shows a simplified embodiment of the apparatus for drying a solvent-containing drying stock GW. As in FIG. 1, the drying unit D is used to dry the solvent-containing drying-stock GW. The drying unit D is used to separate the solvent-containing drying-stock GW in the base material G, in particular a cellulose-containing base material, and the solvent W, in particular water.

[0061] Similarly to the preceding embodiments, this simplified embodiment comprises, a first circuit 1 for the first heat transfer medium WTl and a second circuit 2 for a second heat transfer medium WT2. The second circuit 2 comprises a heat pump WP. The heat pump WP is used to transport heat energy Q from a heat flow WS, in particular from a heat reservoir. The heat pump WP transfers heat energy Q from the heat reservoir WS into the first circuit 1. Preferably, a heat exchanger WT is used to provide the heat energy Q to increase the temperature of the first heat transfer medium WTl. The heat exchanger is also made available to the first heat transfer medium WTl with the aid of a condensation unit HPE (or also an evaporation unit HPC).

[0062] Before the drying unit D, the first heat transfer medium WTl has a temperature Tl. After the drying unit D, the heat transfer medium has a lower temperature T2. Hence, the heat energy Q that is lost due to the drying unit D is fed to the heat transfer medium with the aid of the heat pump WP. Here, the solvent W can escape at one point of the circuit 1.

[0063] Therefore, the heat pump WP is used in this simplified embodiment to compensate the heat energy Q which is drawn off in the drying unit D and by the outgoing solvent W.

[0064] With the aid of a heat exchanger, which is preferably formed as a regenerator, a heat exchanger WT enables the evaporation unit HPE and the condensation unit HPC to be formed by a single regenerative heat exchanger WT. Here, heat energy Q is fed to the first circuit 1 in a first time range and removed in a further time range. The time ranges can be repeated periodically.

[0065] This embodiment is particularly advantageous because the heat pump WP is used to transfer heat energy Q from a heat flow WS into the first circuit 1 even though the temperature of the heat flow WS is lower than the second temperature T2.

[0066] FIG. 3 shows a further embodiment of the apparatus for drying drying stock GW. This embodiment represents a combination of the embodiments shown and described in FIG. 1 and FIG. 2. The embodiment shown here comprises two heat pumps WP. The first heat pump WP is used to take up the condensation heat of the solvent W. The first heat pump transfers the heat energy Q with the aid of the compressor to the condensation unit. In this case, the condensation unit is used to transfer heat energy Q into the first circuit 1. The further heat exchanger WP is used to provide additional heat energy Q for the first circuit 1. The second heat pump WP is used to compensate heat energy losses from the first circuit 1. Depending upon the temperature of the first heat transfer medium WTl and the requirement for heat energy Q, the second heat pump WP is used to transfer heat energy Q from a heat flow WS or reservoir into the first circuit 1. Control and/or regulation of the first heat pump WP and the second heat pump WP is performed by a control device SE in conjunction with sensors S1, S2, S3 (not shown here). Reference is made to FIG. 1 with respect to the control device SE.

[0067] In particular, at the start of the operation of the industrial plant, additional heat energy can be fed to the first circuit 1. In particular, it is also possible for heat energy Q obtained in a conventional way, for example, by the combustion of a fuel or with the aid of electric energy, to be fed to the first circuit 1 and/or the second circuit 2.

[0068] FIG. 4 is a pressure-enthalpy diagram of a preferred second heat transfer medium WT2. The enthalpy h is plotted in [kJ/Mol] on the horizontal axis. The pressure p in [bar] is plotted logarithmically on the perpendicular axis. The diagram shows a set of curves of isotherms, where the temperature (of the second heat transfer medium) is shown above the respective isotherms in degrees Celsius. The isotherms depicted indicate the behavior of a preferred second heat transfer medium R1233zd(E) of the pressure p as function of the enthalpy h. The envelope of the points at which the isotherms have a kink corresponds to the phase boundaries of the second heat transfer medium WT2. The upper region of the envelope depicts a thermodynamic cycle comprising the following points 1a, 2a, 3a, 4a, 5a, 6a. The thermodynamic cycle corresponds to the cycle for the (high-temperature) heat pump. Here, the transitions are:

TABLE-US-00001 1a -> 2a polytropic compression, 2a -> 3 isobaric cooling, 3a -> 4a isobaric liquefaction, 4a -> 5a isobaric cooling (supercooling), 5a -> 6a isobaric evaporation and heating to superheating of the second heat transfer medium WT2.

[0069] The second heat transfer medium WT2 is present in the left region as a supercooled liquid. Hence, the rise in the isotherms is very steep. In the right-hand region of the diagram, the isotherms fall more slowly after evaporation with increasing enthalpy. In the right-hand region, the second heat transfer medium WT2 is present as superheated gas.

[0070] During the (polytropic) compression 1a->2a of the second heat transfer medium WT2, it is compressed to a temperature slightly above the first temperature Tl, in this case about 145° C. In addition, the expansion of the second heat transfer medium advantageously occurs from the temperature above the second temperature T2 to a temperature (about 90° C.) slightly below the second temperature T2 of the first heat transfer medium WT1 in the evaporation unit HPE.

[0071] Also shown are isentropes IS as steeply rising curves. Those assigned to the isentropes IS correspond to states of equal entropy. The numbers express this entropy in [kJ/(kg*K)].

[0072] The extreme supercooling of the second heat transfer medium WT2 to about 5 to 10 kelvin above the inlet temperature (first temperature Tl) of the first heat transfer medium WT1 in the condensation unit HPC can cause the ratio of useful power to working power (rating number COP) to increase by up to 40% compared to the current state of the art.

[0073] FIG. 5 is a heat-transfer-temperature diagram of a preferred second heat transfer medium WT2. The upper segment describes the transfer of heat energy Q from the first heat transfer medium WT2 to the second heat transfer medium WT1. The transfer of heat energy Q is symbolized in the upper curve 21a, 23a, 27a. During heat withdrawal 23a, the second heat transfer medium is cooled from a temperature above the second temperature T2 by about 5 kelvin. In this case, a small portion of heat energy Q is transferred from the second heat transfer medium WT2 to the first heat transfer medium WTl. On condensation of the second heat transfer medium, a further part of the heat energy Q is transferred from the second heat transfer medium WT2 to the first heat transfer medium WTl. On condensation of the second heat transfer medium WT2, the temperature of the second heat transfer medium WT2 remains approximately constant. On the further supercooling 27a of the second heat transfer medium WT2, the temperature of the second heat transfer medium WT2 drops from about 105° C. Up to here, the heat energy Q to be transferred by the second heat transfer medium WT2 is given off. This process in particular occurs in the condensation unit.

[0074] The heat energy Q given off by the second heat transfer medium WT2 is taken up by the first heat transfer medium WTl. Here, the temperature of the first heat transfer medium WTl rises from the second temperature T2 (in this example 100° C.) to the first temperature Tl (here 140° C.). The temperature increase occurs during the superheating 25a of the first heat transfer medium.

[0075] For the thermodynamic considerations dealt with in the figures described here (here FIG. 1 to FIG. 5), a particularly preferred first heat transfer medium WTl is water vapor and a particularly preferred second heat transfer media WT2 are the halogenated hydrocarbons R1233zd(E) and/or R1336mzz(Z).

[0076] The first heat transfer medium WTl is particularly advantageously introduced into the drying unit D with a (first) temperature T1 of about 140° C. When the solvent W is taken up, the temperature of the first heat transfer medium WTl falls to a second temperature of from 90° C. to 100° C., as shown in FIG. 4. The solvent W, in particular water, is once again condensed in the region of the evaporation unit HPE. The heat energy Q that forms thereby is taken up during the evaporation of the second heat transfer medium WT2. With the aid of the compressor of the heat pump WP, the second heat transfer medium WT2 is transferred into the condensation unit HPC. In the condensation unit HPE, the second heat transfer medium is cooled 23a, condensed 21a and supercooled still further 27a. The majority of heat energy Q given off thereby by the second heat transfer medium WT2 is transferred to the first heat transfer medium WTl. Here, the temperature of the first heat transfer medium WTl rises from the second temperature T2 to the first temperature Tl. The first heat transfer medium WTl is then fed back to the drying unit D.

[0077] FIG. 6 is a flowchart of a method for drying drying-stock (GW) during production of a cellulose-containing fiber mat. With reference to FIG. 6, the method comprises circulating a first heat transfer medium (WT1) in a first circuit (1), as indicated in step 610. In accordance with the invention, the first heat transfer medium (WTl) heats the drying-stock (GW) and takes up solvent (W) released from the stock (GW). Next, heat energy (Q) is fed into the first circuit (1) by a second circuit (2), as indicated in step 620. The heat energy (Q) from the second circuit (2) is now introduced into the first circuit (1) by a heat pump (WP), as indicated in step 630.

[0078] In summary the disclosed embodiments of the invention relate to an apparatus and a method for drying-drying stock GW. In this context, the solvent-containing drying-stock GW is separated in a drying unit D into a base material G and a solvent W with the aid of a first heat transfer medium WTl. The first heat transfer medium WTl passes through a first circuit 1. After the solvent W has been taken up by the first heat transfer medium WTl, the solvent W is separated from the heat transfer medium WTl by condensation. The (condensation) heat energy Q is transferred by a heat exchanger WT with the aid of an evaporation unit HPE to a second circuit 2 and provided for a second heat transfer medium WT2. With the aid of a heat pump WP, the heat energy Q in a condensation unit HPC of the heat pump WP is fed back to the first circuit 1.

[0079] While there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.