FI124562B - Steam and condensate system for the dryer section of a fiber web machine - Google Patents

Description

STEAM AND CONDENSER SYSTEM FOR DRYING A FIBER MACHINE

The present invention relates to a steam and condensation system for a dryer section of a fiber web machine comprising a plurality of drying cylinder groups 5 between a steam supply and a condenser cascaded and at least one thermocompressor group having an ejector adapted to recirculate the same dry steam

10 The steam and condensation systems of the drying section of a fiber web machine are generally either cascade systems or thermocompressor systems. There are also remanufactured dryer parts using a cascade and thermocompressor combination where, for example, the drying cylinder groups 1-2 of the initial drying section are in a cascade, i.e. the drying cylinder group 2 feeds the blow , from which the blow-through and expansion vapors are returned by a thermocompressor to the steam side of the same 20 drying cylinder group. The thermocompressor can also be used to raise the vapor pressure of a particular drying cylinder group by increasing the pressure of the low pressure steam with high pressure steam. Thermocompressor groups generally require another high-pressure steam line for motive steam.

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As the prior art steam and condensate system, the so-called cascade controlled drying section of the multi-condensate tank system, wherein all the drying cylinder groups are in the cascade, there are several condensation tanks and at least one condenser.

o 30 This type of system has problems with energy use and drying control. In the system, according to the cascade,

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0 The volume of expansion steam in the condensate tanks and condensate tanks increases

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C \ J toward the first drying cylinder groups in the driving direction of the drying section. As a result, the volume of purge and expansion vapor entering the first drying cylinder group is so large that up to 6 drying cylinders are required for the first drying cylinder group. Further, the volume of flow-through steam leaving the first drying cylinder group 2 is large, so that the condensation of all the flow-through steam requires a high power from the condenser. A high-capacity condenser, in turn, requires a large amount of cooling water, which in many cases is limited in availability. Attempts have been made to reduce the capacity of the condenser by first directing the steam from the drying cylinder groups to the hood replacement air preheater or similar energy-consuming object. However, such arrangements take up space and require a large number of pipelines, the investment of which will incur additional costs.

The surface temperatures of the drying cylinders play an important role in the threading of the drying section of the fiber web machine. Preferably, the first drying cylinders could use surface temperatures suitable for each type of fibrous web being run, so that the adhesion of the fibrous web to the first drying cylinders would not be a problem. With prior art steam and condensate systems, the pressures in the first dryer cylinder group cannot be applied at high enough pressures to prevent adhesion of the fibrous web to the first dryer cylinders. High pressures would allow the fibrous web to be driven above the bonding temperature range.

US 4,447,964 A is known in the art, having a steam and condensation system for a dryer section of a fiber web machine in which 'fr,, ...

^ includes a primary set of rotary drying cylinders, steam c .....

, inlet and outlet connections combined with drying cylinders oo? for supplying steam and for removing flow-through vapors; and oo ° recirculation means comprising an ejector for recirculating the steam through the steam outlet from the inlet to the inlet. In addition, the system includes control means for controlling recycling; and

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to secondary drying cylinders between the ejector and the condenser.

DE 102008000227 A1, c, j also discloses a steam and condensation system 35 for a drying section of a fiber web machine having at least one thermocompressor group.

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It is an object of the invention to provide a steam and condensation system for the drying section of a fiber web machine which is more energy efficient and easier to adjust. Characteristic features of the present invention will be apparent from the appended claims.

According to the invention, this object can be achieved by making a second dryer-cylinder group of a cascade-connected steam and condensate system a thermocompressor group in which a thermocompressor is used to recirculate the same steam from the same drying cylinder group to the feed steam via the The steam of the main steam pipe is used as the motive steam of the thermocompressor. Thus, in cascade coupling, the through-flow and vapor accumulating on lower pressure drying cylinder groups can already be controlled by a thermo-15 compressor group without accumulating on the first drying cylinder group. This makes the first drying cylinder group smaller in size than the other drying cylinder groups.

In the system according to the invention, the first drying cylinder group is small in size, only 2-4 drying cylinders, whereby the amount of blow-off steam coming from the drying cylinder group is considerably smaller. The capacity required of the condenser and thereby the amount of cooling water required is substantially reduced.

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In a system according to the invention, a first

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? ester group is not directly in cascade with the N termokompressoriryh- lauhdepuolen system, so the first kuivatussylinteriryh-x g; The pressure of 30 m is more freely adjustable. The first drying cylinder blade group may be provided with a steam supply from the main steam pipe, whereby its pressure can be freely selected, if necessary. Furthermore, in the system according to the invention, the number of drying cylinders 35 of the first drying cylinder group and the thermocompressor group is more freely selectable since it is not limited by the cascade connection 4. This provides more possibilities to adjust the drying section according to the type of fiber web being run.

In the system of the invention, the need for cooling water 5 in the condenser is significantly lower than prior art systems, thus eliminating the need to construct complex flow-through steam cooling systems.

In the system according to the invention, it is also possible to use a thermocompressor of more than 10 parts, whereby the thermocompressors can be better dimensioned for different types of fibrous web driven by a fiber web machine.

The system of the invention is suitable for use as a steam and condensation system for drying parts of pulp, paper and board machines and tissue machines. The invention can also be applied to other applications.

More specifically, the vapor and condensation system of the drying section of the fiber web machine 20 according to the invention is characterized in that the lowest pressure drying cylinder group has fewer drying cylinders and the supply pressure line of the thermocompressor group with

The invention will now be described in detail with reference to the accompanying drawings, which illustrate certain embodiments of the invention,

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? where N-

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£ 30 Figure 1 is a schematic diagram of the steam and condensation system of the conventional multiconductor tank system S of the prior art fiber web machine o, G)

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Figure 2 is a schematic view of a dry-35 tensile steam and condensation system of a fiber web machine according to the invention.

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Figure 1 is a schematic diagram of a steam and condensation system 10 of a conventional multi-condensate tank system for a dryer section of a fiber web machine. The steam and condensate system consists of a main steam pipe 100, drying cylinder groups 12, 14, 16, 18 and 20 consisting of drying cylinders 11, condensation tanks 22, 24, 26 and 28, a condenser 30, a main conduit line 32 and piping and actuators. The numbers beginning with S in the drying cylinders 11 indicate the running number of the cylinders in the group.

10 The drying cylinder groups include a plurality of drying cylinders and the drying cylinder groups have different pressures relative to each other. With respect to the direction of travel of the fibrous web 13, the pressure level rises from the first drying cylinder group 12 of the lowest pressure level to the last drying cylinder group 20 of the highest pressure level.

The steam lines of the drying cylinder groups are connected by a cascade connection, i.e. the discharge steam of the higher pressure drying cylinder group is used to heat the next drying cylinder group.

20 Primary steam is normally fed from the main steam tube 100 through the main feed 36 to the final drying cylinder group 20. Also, the other cylinder groups have inlets 38 for additional steam and group pressure control. Primary steam is fed to the drying cylinders of the drying cylinder group, where it releases its thermal energy to the surfaces of the drying cylinders and condenses into condensate. The condensate is sucked into the condensate discharge passage S5 from the drying cylinder through the inlet steam, i.e. the through-flow steam, from where it ends up in the condensate tank. In the condensate tank, the steam is separated from the 00 condensate and part of the condensate evaporates again. This expansion x £ 30 steam and flow-through steam are led to the feed steam of the next drying cylinder group.

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σ> o The through-flow steam from the first lowest pressure level dryer cylinder group 12 is conveyed, together with the expansion vapors of the first condenser tank 35, to a condenser 30 where it is condensed by the cooling water 29. The condenser 30 6 is large in size because it has a capacity that is capable of condensing all the steam from the drying cylinders, even in the event of a breakdown. During breaks, it is desired to avoid heating the drying cylinders, so that the steam in the drying cylinders is directed at the beginning of the break to directly reduce the pressure on the condenser without circulating it cascade through lower pressure level drying cylinder groups.

Figure 2 shows an embodiment of the steam and condensation system of the drying section of a fiber web machine 10 according to the invention. From the functionally similar parts, the same numbering as in Figure 1 is used. In this embodiment, the thermocompressor group 14 is built into a two condenser steam and condensate system instead of the conventional cascade controlled multilane 15 tank system. The total number of drying cylinders of the drying section remains the same as that of the multi-tube container system of Figure 1.

The two condenser steam and condensate system of Figure 2 consists of 20 main steam tubes 100, drying cylinder groups 12, 14, 16, 18 and 20 consisting of drying cylinders 11, condensation tanks 22, 24 and 26, condensers 30 and 31, and piping and actuators. In the exemplary embodiment, the steam and condensate system otherwise operates within the cascade except for the second dryer cylinder group 25, which is a thermocompressor group. The main steam line 100? the water vapor is fed to the last pressure drying cylinder group 20 at the highest pressure 20. The ln? the inlet and outlet flows are controlled by valves and chokes 00 68.

The second dried cylinder group 14 of the steam and condensation system according to the invention is a so-called thermocompressor group, i.e. a drying cylinder group, in which the low pressure exhaust steam c is pressurized by a thermocompressor to a high pressure feed 35. The drying cylinder from the Group 14 will condensate is passed to the second condensate tank 24, from which the second condensate July 24 paisuntahöyry and from the second drying cylinder group through the flow of steam is passed termokompressoriryhmän 14 of the ejector 54 of the supply line 52 along the ejector 54. Termokompressoriin fed motiivihöyrynä high-pressure main steam vapor, 5 which accelerates the supply line 52 along finish matalapaineisem-man vapor view, in the ejector 54 of the thermocompressor group 14. The steam in the main steam line is made possible by the pressure of the second condensate tank 24 which, depending on the driving situation, is about -20 to + 100kPa. The combination of vapors from the thermocompressor yields a higher pressure supply vapor of the thermocompressor group 14, which is fed to the drying cylinders 11.

The thermocompressor replaces the differential pressure control valve in the feed line, which in conventional cascade coupling precedes the next 15 drying cylinder groups. The thermocompressor adjusts the pressure difference of the drying cylinders 4-6. The thermocompressor group may also be a group other than another drying cylinder group.

As shown in FIG. The supply steam to the drying cylinders 4-9 of the thermocompressor group is controlled via an ejector 54 of the thermocompressor group 14, r--

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The supply pressure line 60 of the thermocompressor group 14 has a choke 68 for controlling the amount of feed vapor to the first drying cylinder group 12 partially connected to the cascade with the thermocompressor group 14, thus adjusting the amount of steam needed for the first drying cylinder group 12. and all the through-flow and vapor vapor 8 of the higher pressure cascade drying cylinder groups 16, 18, 20 need not be fed to the first drying cylinder group 12. The required additional steam for the thermocompressor group 14 and the first drying cylinder group 12 is obtained from the main steam. Thanks to the thermocompressor group 14, the first dryer cylinder-5 blade assembly 12 can be made small in size, covering 2-4 drying cylinders, preferably three drying cylinders, as in Figure 2. The first dryer cylinder assembly is smaller in number of drying cylinders and smaller than the thermocompressor group. The size 10 of the thermocompressor group 14 is 7-10 drying cylinders, respectively, and the number of drying cylinders of the drying cylinder groups 16, 18 and 20 is similar to that of the prior art multi-condensate tank system.

The first dryer cylinder group is provided in the system 15 according to the invention with its own lymph steam supply valve 35 from the main steam line, by means of which the pressure of the dryer cylinder group can be adjusted independently of the other dryer cylinder groups. This greatly facilitates the control of drying when driving various types of fiber webs, since the temperature of the first group of drying rollers-20 is almost freely selectable.

Due to the small size of the first drying cylinder group 12, the size of the condenser 30 required during use can be reduced, thereby also reducing the amount of cooling water required. 25 In the case of the steam and condensate system shown in Figure 2? the first condenser may preferably have a power of about 400, kW, which is considerably small in the prior art

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? compared to. The recycling of the vapor and expansion vapor from the drying cylinder group 12 via the air-conditioning radiators can be omitted with a precision of £ 30. Savings can be made in pipeline costs, space usage and partly in energy costs.

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O) In the system of the invention, the pressure of the second condensate container 24 is lower than that of the conventional multi-condensate container system, since the pressure of the condensate container 24 is determined by the pressure level of the drying cylinders 4-6. In the conventional system, the pressure level of the condensate tank 9 is determined by the drying cylinders 7-8, which are at a pressure of at least 50 kPa, which means condensates hotter than 10 ° C. These hotter condensates are routed directly into a lower pressure condensate reservoir in the conventional system, which raises its temperature. With the steam and condensate system of the invention, the temperature of the condensates from the drying section is about 100 ° C or even lower, whereby the need for condensate recycling is eliminated. Removing condensate recycling again saves pipeline costs and facilitates space use. The condensates of the tanks 10, 24, and 26 of Lau-10 are pumped along an outlet 64 to the main condensate channel. Each condensate container 22, 24, 26 is also at a different pressure according to the cascade, determined by the pressure of the drying cylinder group supplying the condensate container.

2, a venting conduit 58 is provided in the system for the second condenser 31. The venting conduit 31 to the second condenser 31 is used to remove the air from the condenser 31 to the first condensate tank 22 to prevent air from being heated. The first condensate tank is provided with a vent passage 62. The cooling-water circulation of the condenser 31 is preferably coupled in series with said lower pressure condenser.

The vapors of the drying section of a fiber web machine according to the invention? The condensation system can be applied to both the conventional multi-condensate tank system shown in Figure 1 and the

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? a two-condenser system. The thermocompressor can also be installed in the prefabricated condensate tanks if necessary

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Claims (5)

10 A steam and condensation system (10) for a dryer section of a fiber web machine comprising a plurality of drying cylinder groups (12, 14, 16, 5 18, 20) between a steam supply (36) and a condenser (30) cascaded and at least one thermocompressor group (14) is an ejector (54) adapted to recirculate off-steam from the same drying cylinder group (14) with feed steam, wherein the system (10) has fewer drying cylinders (11) in the first drying cylinder group (12) than in the other drying cylinder groups (14, 16, 18, 20) 14) the supply pressure line (60) is connected via the choke (68) to the supply of the first drying cylinder group (12) and the motive steam of said ejector (54) is the main steam line (100) 15, characterized in that an inlet valve (35) from the main steam line (100). The system (10) enligt patentkrav 1, the turn-off device 20 is a första torkcylindergruppen (12) innefattar 2-4 torkcylindrar (11). System (10) according to claim 1, characterized in that said first drying cylinder group (12) comprises 2-4 drying cylinders (11). 3. The system (10) enligt face av patentkraven 1 eller 2, the teleconverting device att att genombläsningsängan som skall urine frän den 25 torkcylindergrupp (16) som har högre tryck account thermocompressor- ^ Gruppen (14) itself a salient account en del av thermokompressorgruppens CNJ, 14) torkcylindrar (11). Lii cp 1 ^ A system 25 (10) according to any one of claims 1 or 2, characterized in that the through-flow CM i fed from the higher pressure drying blade -> blade assembly (16) to the thermocompressor group (14) is fed only to a portion of the drying cylinders (11). The system o (10) according to any one of claims 1 to 3, characterized in that the thermocompressor group (14) comprises S at least one ejector (54) of the thermocompressor group (14) for vapor pressurization. CM A system (10) according to any one of claims 1 to 4, characterized in that said system (10) comprises at least two condensers (30, 31) operating at different pressures, one of which is a condensate (30) for the exhaust steam of the first drying cylinder group (12). ), and one higher capacity condenser used in the event of a breakdown (31). 5 δ {M sj- o CD {MX en CL O m (M CD O) oo (M 12 1. Äng- och kondensatsystem (10) för en f iberbanmaskin, whistling utgörs av flera torkcylindergrupper (12, 14, 16, 18 , 20) 5 cascade duplicator mellan ängmatningen (36) och condensor (30) och minst en thermocompressor group (14), som har en ejector (54) anordnad att med hjälp av pränga circulator samma torkcylin-dergrupps (14) avloppsänga som dräränga det i systemets (10) torkcylindergrupp (12) fork torkcylindrar 10 (11) sound torkcylindergrupper (14, 16, 18, 20), thermocompressor (14) matningstrycklinje (60) är ansluten via en shunt (68) till den första torkcylindergruppens (12) matning och som den nämnda ejektorns (54) motänga används huvudänglinjens (100) prima änga, 15 kännetecknat av att account den frost torkcylindergruppen (12) har anordnats en egen pränilän (35) ). The system (10) enigt faces av patent craven 1-3, fold-x £ 30 nat av att thermocompressor group (14) innefattar minst en o thermocompressor group (14) ejector (54) for att set avlopps-co räng under tryck. o o o C \ J 5. System (10) en face the patent craven 1-4, kecket-35 nat av att det this system (10) innefattar out of the under olika tryck fungerande condensorer (30, 31), the first 13 första torkcylindergruppens (12) ) avloppsängas capacitor (30), och en är en capacitor (31) med högre effekt att användas vid avbrottssituationer. 5 't δ c \ j i m o i 1 ^ C \ l X cc CL O m CM CD O) o o CM