FI92417C - Process and device for preheating of waste - Google Patents

Description

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METHOD AND APPARATUS FOR PREHEATING WASTE MATERIAL FORFARANDE OCH ANORDNING FOR FORVÅRMNING AV AVLUT

The present invention is directed to a granular method and apparatus 5 for preheating a waste liquor from the cellulose industry, such as black liquor, by feeding pressurized steam from a steam feeder through steam holes to a waste liquor stream as the waste liquor flows through a waste liquor tube or waste liquor tube.

10 In pulp production, lignin and other organic non-pulp-based material are separated from the pulp raw material by cooking with cooking chemicals. In addition to the pulp, cooking liquor is recovered from the pulp soup. The waste liquor, which is mechanically separated from the pulp, has a high calorific value due to the carbonaceous and other organic combustible substances separated from the pulp. Jateliemi also contains inorganic chemicals that do not react in pulp cooking. Several different methods have been developed for the recovery of Jateliemi låmindn and chemicals.

20

The black liquor obtained from the production of sulphate pulp is burned in a recovery boiler. When the organic and carbonaceous substances contained in the black liquor burn, the inorganic components of the broth are converted into chemicals that can be recycled in the cooking process.

Black liquor must be concentrated before incineration. The main concentration of the black liquor takes place, for example, in evaporators connected in series. By evaporation, the black liquor can be concentrated to a dry matter content of about 50 to 55%. After this, the dry matter content of the black liquor must still be raised to approx. 60-65%, e.g. by direct evaporation.

After evaporation, it is often necessary to still preheat the waste liquor before passing it to the lye nozzles of the recovery boiler. This preheating is traditionally carried out either by indirect preheating, which is usually carried out in a preheater based on the principle of a tube heat exchanger, or by direct preheating, in which pressurized steam is introduced into the waste liquor.

Both the indirect and direct preheaters have been built into the latest built preheating systems. The preheaters are connected in parallel, so that they can be used alternately to achieve the optimal preheating result in varying conditions. Parallel connection is, of course, a technically expensive solution. In particular, the manufacturing cost of the 10 indirect preheaters is high. In addition, the indirect preheater requires relatively expensive and cumbersome cleaning procedures in use. Possible outages due to malfunctions cause significant financial losses to the plant.

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In addition, the temperature control of black liquor is difficult with the traditional direct preheaters in use, especially over a wide operating range.

20 A direct preheater for a waste liquor for incineration has traditionally consisted of a waste liquor tube or chamber and a surrounding jacket. Holes are then formed in the wall of the waste liquor chamber, through which steam is fed from the steam jacket into the waste liquor chamber.

25

A conventional black liquor straight preheater comprises an inner tube, i.e. a black liquor chamber, and an outer jacket, i.e. a steam jacket, thus perforated. The outer jacket has a water vapor intake component. In addition, the outer jacket has a condensate drain. 30 The inner tube, inside which the black liquor passes, has small holes through which the pressurized steam penetrates from the steam jacket into the black liquor, heating it.

From the point of view of functionality, the conventional solution 35 described above has essentially only one optimal operating point, where the correct amount of steam flows from the holes and the size of the steam bubble is such that no bursts occur in the lye.

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When the black liquor flow rate, black liquor pressure and / or steam pressure change, the direct preheater no longer operates in an optimal manner. Indeed, obtaining a suitable hybrid pressure 5 relative to the black liquor pressure and flow rate has proven difficult in the past. When the ratio of the steam ratio does not remain correct, the device operates unstably and, in addition, the wrong steam ratio causes a "bang" and a story that strains the structure. The entire preheater then works unstably.

10

It is an object of the present invention to provide an improved method and apparatus for direct preheating of waste liquor than described above.

In particular, it is an object to provide a method and a device which, in a variable operating range, operate more stably and safely than previously known methods and devices.

It is a further object to provide a method and an apparatus by means of which the temperature of the effluent entering the recovery boiler can be adjusted more precisely at a preheater fair.

The method according to the present invention for preheating a broth in a pressurized steam feed is characterized in that, in order to achieve the above-mentioned purposes, the amount of steam fed to the waste broth chamber is controlled through steam holes.

30

The preheater according to the invention is correspondingly characterized in that at least a part of the steam holes connecting the steam chamber to the waste liquor chamber can be closed to optimize the amount of steam flowing from the steam chamber to the waste broth chamber.

The amount of steam fed to the waste liquor chamber can be determined, for example, by adjusting the number of steam holes in the steam liquor chamber in connection with the waste liquor chamber 4,9241 7. According to the invention, at least part of the holes can be covered with a cover plate, a ring jacket or the like, whereby the flow of steam through these holes is blocked.

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The device solutions according to the invention can thus directly affect the number of open steam holes, which achieves the following advantages: - optimal steam volume in black liquor, 10 - the size of the steam bubbles is the capacity-dependent wheel of the right size, - the device is simple, - the device is reliable, 15 - the device requires little maintenance, - the device has low spare parts costs, - the device requires only mild cleaning measures, - the device is easy to control and - the device is safe to use due to the stability of the device 20.

On the other hand, the amount of steam flowing from the steam chamber to the waste liquor neighborhood can also be controlled by dividing the steam chamber surrounding the waste liquor chamber into separate parts and obtaining the amount of steam fed to these parts separately. In this way, a part of the steam chamber can be partially or completely decommissioned and thus the steam holes of this part can be excluded from use and thus the amount of steam fed into the effluent stream can be reduced.

30 The amount of steam fed from the steam chamber to the effluent stream can, of course, also be reduced by closing a 'determined number of steam holes and opening a corresponding number of other steam holes with smaller openings than the closed steam holes.

The direct preheater which is the subject of the invention can be equipped with various actuators. However, the basic idea is that according to the capacity, the number of open 35 5 9241 7 steam holes or the uniform open area of the steam holes is determined. In place of the tire casing, it is thus possible to use various guide plates or iron members which are moved mechanically or in another way.

5

The solutions according to the invention, which require the least moving parts, are recommended and achieve the highest operational reliability.

The invention will now be described in more detail by way of example and with reference to the accompanying figures, in which

Fig. 1 schematically shows a pre-heater according to the invention, partly in section,

Fig. 2 schematically shows a second embodiment of a preheater according to the invention, partly in section, Fig. 3 shows an enlarged view of section 2 of Fig. 2 along the line A-A, and

Figures 4-5 schematically show other embodiments of a preheater according to the invention, partly in section.

Figure 1 shows a preheater 10 comprising an elongate tubular waste liquor blank or waste liquor tube 12 through which the waste liquor flows in the direction indicated by the arrows. The preheater further comprises a steam jacket or steam chamber 14 which is tightly fitted around the broth tube 30. The wall 16 of the waste liquor tube has steam openings 20 formed in the part 18 of its steam jacket, of which only a part is shown in the figure. In addition, the preheater comprises an annular sheath 22 which covers a portion of the vapor openings formed in the walls of the waste liquor tube and thus prevents steam from flowing from those openings into the waste liquor tube. The steam jacket comprises a condensate drain connection 23.

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Connected to the ring jacket 22 are transfer members 24 by means of which the ring jacket can be moved in the axial direction of the broth tube.

The device according to Figure 1, e.g. The size and number of heating holes are preferably determined by the maximum capacity of the heater. The holes are preferably the same size but may be different sizes.

Depending on the position of the axially movable annular sheath 22 around the inner tube, a larger or smaller part of the steam openings 20 can be closed. The number of open holes is then proportional to the flow rate of the black liquor. The vapor pressure can thus be kept approximately 20 constant. The movement of the annular sheath can be realized by the members shown in Figure 1, or in some other known manner.

Figures 2 and 3 show another embodiment of a preheater according to the invention 25. The heater shown in the figures also comprises a broth tube 12, a partially surrounding steam jacket 14 and an annular jacket 22. In this embodiment, the annular jacket according to Fig.

As shown in Fig. 3, ribs 30 or the like are arranged on the inner surface of the annular sheath 22, which also allow a partial flow of steam on the inside-35 side of the annular sheath in the space 32 between the ribs.

In the preheater shown in Figures 2 and 3, the steam hole is preferably arranged only in the area covered by the annular sheath 7 9241 7 in the wall of the broth tube. By moving the annular jacket in the circumferential direction of the pipe, the ribs 30 can be positioned so as to cover, if necessary, a larger or smaller part of the steam holes formed in the wall of the pipe. 5 The space between the fins allows steam to flow from the openings that hit these gaps.

Also in the solution according to Figures 2 and 3, the inner tube is realistic and the size and number of holes are preferably determined according to the maximum capacity of the heater. In this solution, the annular jacket is movable around the inner tube in the circumferential direction and, depending on the circumferential position of the annular jacket, some of the openings are closed. In this case, the number of open holes in the optimal position of the ring jacket 15 is also made proportional to the flow rate of the black liquor. The vapor pressure can be kept approximately constant.

Figure 4 shows a fourth embodiment of a preheater according to the invention. The preheater 20 according to this figure comprises a residual broth tube 12 and a vapor jacket 14 arranged around it.

A different number of steam holes 20 are formed in the wall of the waste liquor tube in different parts of the steam jacket. In the solution according to Figure 4, the steam section 50 has fewer holes than in sections 52 and 54. 64 and 66, which can be used to adjust the volume.

Thus, in the solution according to Figure 4, the preheater jacket is divided into three different sub-spaces 50, 52 and 54. At each of the 35 sub-spaces, the inner tube has 12 different numbers of holes. The steam can be controlled separately for each sub-space. By varying the closed positions of valves 62, 64 and 66, different capacity options are obtained. In addition, the steam supply line 8 9241 7 68 still has a main supply valve 70, which can be used to control the steam supply pressure of all sub-spaces.

In addition, sanitary-5 lines 72, 74 and 76 are arranged in the sub-spaces 50, 52 and 54, by means of which small amounts of steam can be directed to the steam holes and the minimum pressure is maintained in the sub-spaces. This prevents the black liquor from entering the sub-compartment with the actual steam valve closed.

Figure 5 shows a fifth embodiment of a pre-cutter according to the invention. The preheater according to the figure comprises, as in the previous solution, a waste liquid pipe 12, a steam jacket 14 arranged around it, which is divided into sub-spaces 50, 52, 54 and 55. A different number of steam holes 20 are formed in the wall of the waste water pipe for different compartments.

In the solution according to Figure 5, the space between the waste liquor tube and the steam jacket is thus divided into four parts. The ratio of the number of holes between the sub-spaces is constant. The steam can be controlled separately for each sub-space 20. In this case, the yield is ON / OFF. By varying the closing and opening of the valves to get different capacity options. For example, four different sub-modes provide 24 = 16 different capacity options.

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In this application, the cleaning compartments 72, 74 and 76 are also connected to the compartments, by means of which a small amount of steam can be directed to the compartments and the passage of black liquor to the compartment with the actual brake-30 brick closed.

The solutions according to the invention presented above substantially improve the functionality of the straight pre-meter. The temperature of the waste liquor fed to the recovery boiler can be precisely adjusted. There is not too much or too little water vapor in the broth and the dry matter content of the broth remains as high as possible.

II

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The direct preheaters according to the invention operate stably and without story. The capacity of the preheaters can also be obtained in an optimal way.

The invention is not intended to be limited to the application examples presented above, but is intended to be applicable within the scope defined by the claims.

Claims (13)

1. Process for black liquor from the cellulose industry, such as black liquor 5, esilåmmittåmiseksi death pressurized steam is hoyrynsyottoelimesta hoyryreikien jåteliemi through-flow of the waste liquor flowing jateliemiputken or chamber låpi, further characterized in the inputted through and working esilåmmitystå såådetåån sååtåmållå hoyryreikien jateliemikammioon Vapor 10 hoyryreikiin deal of control. A method according to claim 1, characterized in that the amount of vapor fed is obtained by obtaining a number of vapor holes connected to the dispenser stream 15. A method according to claim 1, characterized in that the amount of steam introduced is adjusted by adjusting the size of the openings of the steam holes in connection with the effluent stream 20, i.e. the total open area of the openings. A method according to claim 1, characterized in that the effluent 25 is preheated as it flows through an elongate effluent chamber having a vapor hole formed in it. . A method according to claim 4, characterized in that the amount of steam introduced is controlled by adjusting the number of vapor holes connected to the effluent stream 35. A method according to claim 5, characterized in that in the amount of steam fed 24241 7, a part of the jacket of the elongate waste liquor union is provided on the cover with a separate annular jacket so that the desired part of the steam holes is covered. A method according to claim 1, characterized in that. that the ice broth is preheated in an elongated ice broth chamber surrounded by a chute jacket divided into at least two different parts, which is connected to the ice chamomile chamber through the steam holes, and that A preheater for preheating a waste liquor from the cellulose industry, such as 15 black liquors, which preheater comprises a waste liquor chamber (12) and an associated steam extraction means (14) and a plurality of steam holes (20) in the flow outlet. , 20 that at least a part of the steam holes (20) can be closed from the steam intake member to control the amount of steam flowing into the waste liquor chamber. A preheater according to claim 8, characterized in that - the tubular waste broth chamber (12) is surrounded by a steam jacket (14), - 30 steam holes (20) are formed in the tubular wall of the waste broth chamber further provided with an annular jacket (22) at least partially surrounding the tubular chamber, which is movable axially 35 and / or radially so that it can cover the desired part of the steam holes. A preheater according to claim 9, 9241 7, characterized in that the annular jacket (22) forms a tight ring around the waste liquor stack. A preheater according to claim 9, characterized in that the annular sheath (22) is provided on the inside with rib-like members (30) which close part of the steam holes. A preheater according to claim 9, characterized in that the tubular waste liquor chamber is surrounded by a tubular steam jacket (14) divided by one or more radial partitions (48,49) into two or more 15 consecutive steam intakes. the conductive vapor inlet connections (56,58,60) are provided with vapor valves (62,64,66) through the vapor intake space to obtain the amount of vapor fed to the waste liquid chamber. A preheater according to claim 12, characterized in that a different number of steam holes are provided in the wall of the broth chamber in at least two steam intake spaces. 25 9241 7