JP3461311B2 - Continuous digester system with inverted top separator and method of use - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an existing gas-phase digester.
Can be modified to operate in the same mode as a full liquid digester.
Continuous digester apparatus and method of using the same .

[0002]

2. Description of the Related Art Continuous digestion of comminuted cellulose fiber material
The technology for producing cellulose pulp, which is a raw material for paper products, includes substantially two types of digesters: a full liquid digester and a two-phase or gas-phase digester. A liquid-filled digester is a pressure-resistant tank in which the crushed cellulose fiber material and the liquid are full, and when the liquid is put into or discharged from this tank, it is usually at atmospheric pressure. Higher tank pressures are affected. The vapor digester is not full of liquid and its top is filled with steam above atmospheric pressure. Since this gas zone is more compressible than the lower liquid zone, the pressure in the vapor digester is usually determined by the pressure of the gas present at the top of the digester. Prior art gas phase digesters are disclosed in U.S. Pat. Nos. 3,380,883, 3,429,
773, 3,532,594, 3,578,5
Those described in the specification of No. 54, and No. 3,802,956.

To produce a chemical pulp by reacting a pulp chemical with a ground cellulose fiber material, a temperature of 140 to 180 ° C.
A temperature in the range of is required. At atmospheric pressure, the aqueous chemical solution used to treat the cellulosic material will boil at such temperatures, so a commercial chemical pulp manufacturing process will have at least about 5 bar gauge (ie, at least about 70 psi gauge). It is usually done in a pressure vessel under the pressure of.

One of the notable differences between these two digester operating methods is that the digester contents are at the desired 140-180 ° C.
How is it heated? In a full liquid digester, the comminuted cellulosic fibrous material (usually wood chips) and the cooking liquor are usually heated by a heating liquid circulation means, i.e. one or more circulation loops. The liquor is usually extracted from the digester using, for example, an annular screen assembly and a pump, heated by steam in an indirect heat exchanger, and inside the tank using a pipe inserted in the center of the tank. Re-introduced into the cellulosic material. In gas phase digesters, the chips are typically heated by exposing the chips to steam. This steam heating is usually done when the chips are introduced into the steam-filled zone at the top of the digester.

In addition to the heating method, the operation of the liquid digester and vapor phase digester also differs in the method used to monitor and control the level of chips and liquor in the vessel. Since the liquid digester is full of liquid, only the level of chips need be monitored. The level of chips in a liquid digester is usually monitored using mechanical rotary vanes. The bending (deflection) of the rotary blade is detected by a device such as an electronic strain gauge. Usually two or more, preferably three or more electronic / mechanical devices are provided on the inside surface of the liquid digester. Whether or not there is a chip at the position of the rotary blade is determined by the extent to which each rotary blade is bent (flexed) or moved by the chip. The movement of each rotary blade is detected by the strain gauge,
The approximate level of chips in a full digester is determined by a mathematical algorithm and expressed as a percentage. The operator can change the chip level by changing the amount of pulp in and out of the full liquid digester.

In a gas-phase digester, two levels are monitored,
Have to control. The level of chips is similar to that of a full digester, with the addition of liquid levels. However, unlike full-fill digesters, in gas-phase digesters the chips are not immersed in the liquid at the top of the digester. Due to the nature of gas-phase digesters, it is necessary to directly expose the chips to heating steam,
The chip level of a vapor digester is above the liquid level. This non-immersed (exposed) chip surface is usually detected with a gamma ray emitting / detecting device mounted on the side of the digester. The liquid level of the gas phase digester is detected by a conventional liquid pressure detection device, for example a "DP cell".

Furthermore, the chips are introduced into the two types of digesters by different mechanical devices. Wood chips, or other comminuted cellulosic fibrous material, is commonly fed to the inlet of a continuous digester using a separate feeding device. Usually provided in the feeder is a device for degassing, heating, pressurizing or a device for mixing the cooking liquor with the chips before transferring the slurry of chips and liquor to the digester. In the case of a full digester, the chips / liquor slurry is introduced on a downward screw conveyor referred to in the art as the "top separator". In a gas-phase digester, the slurry is introduced into the gas phase, so the chip / liquid slurry is transported upwards on a screw conveyor, where the chips and liquid overflow at the top of the conveyor and fall freely into a steam-filled atmosphere. To do. With this upward flow,
The chips and liquor overflow are ideally suited for gas phase digesters. This is because leakage of gas at the time of introducing the slurry into the digester is prevented, and a weir type liquid storage section can be formed to remove excess liquid. This device
It is known in the art as an "inverted top separator". Both devices can separate excess liquid from the slurry and return this liquid to a supply system (eg, conventional high pressure feeder) as a source of slurrying liquid. The functions of these devices are similar, but
It is clearly applied depending on the type of digester.

Conventionally, the structure and operation of a full-fill digester and a gas-phase digester are distinctly different. To operate one type of digester in the same way as another type of digester
The person skilled in the art would have no idea. At least significant digestion must be made to each digester. For example, gas-phase digesters typically do not have the same number of circular screens or liquor circulations needed to heat a full liquid digester. In addition, the liquid-filled digester does not have a device for detecting the chip level on the liquid surface, which is required by the vapor-phase digester. Furthermore, the two top separators differ in structure and mode of operation.

Gas-phase digesters have some drawbacks compared to full-fill digesters. For example, direct exposure of wood chips to steam can be harmful to the chip fibers. The rapid changes in temperature that normally occur when exposing a chip to steam can cause the chip to undergo non-uniform processing. For example, when the cooking chemicals do not uniformly penetrate into the chips, this temperature increase may cause a heterogeneous reaction between the cooking chemicals and the cellulose component and non-cellulose component of the chips. As a result, the quality of the pulp may be deteriorated, for example, the strength of the paper may be deteriorated, or non-uniform delignification may be caused. In a liquid-filled full-filled digester, more uniform heating and treatment are performed, so there is little risk of non-uniform treatment of chips immersed in the liquid.

Vapor digesters are also sensitive to changes in the relative levels of chips and liquor. In the gas-phase digester, the main factor for heating the chips to the digestion temperature is the residence time in the steam atmosphere, and therefore, the shorter residence time means insufficient heating. Therefore, in a vapor-phase digester, the chip level must always be maintained sufficiently high above the liquid level to ensure proper heating. If the residence time in the steam atmosphere is reduced, the heating of the chips becomes insufficient,
Uncooked chip particles, or "slag," will increase in the produced pulp. Therefore, operators of gas phase digesters must continually monitor and adjust the relative levels of chips and liquor. This problem does not exist in a full-liquid digester that heats with circulating liquid.

Further, the chip pile existing on the liquid surface of the gas-phase digester tends to cause non-uniform pressure distribution, which causes non-uniformity in the vertical motion of the chips of the digester. That is, these inhomogeneities affect what is called "tip column motion". When immersed in the liquid, the weight of the chip is reduced to some extent by the buoyancy received from the liquid. However, the non-soaked chips exert a pressing force from above on the chips below depending on the distribution of chips in the digester. Since chips are usually introduced near the center of the digester, a conical chip pile is formed, and a downward load is larger on the center of the column of chips than the wall of the digester. In this way, an extra load is applied near the center, while the wall of the tank has a frictional force, which promotes a downward movement of chips in the center of the digester, a phenomenon known as "channeling". .
The resulting non-uniform movement of the tip results in non-uniform treatment of the tip. When this happens, slag increases, paper strength decreases, consumption of cooking liquor increases, and operability of the digester deteriorates. On the other hand, in a full liquid digester, the load change and uneven movement of the chip column do not occur.

However, the ability to apply additional downward force as needed may be advantageous. Limiting the downward movement of the tip pile, for example, when operating conditions are disturbed or if desired, use the un-immersed tip pile to load downwards to facilitate downward movement of the tip post. It is possible to do it. Thus, having the freedom to change the chip level relative to the liquid level gives the operator additional flexibility to control the digester. This option is inherently lacking in conventional full digesters. This capability is inherently absent in conventional gas phase digesters. This is because the residence time required for the vapor zone of the vapor digester is limited. Therefore, it is technically new to provide such a capacity to digesters.

Further, the gamma radiation / detector commonly used to monitor and control chip column levels in gas phase digesters is also undesirable. Devices that emit radiation are
Any kind of thing is undesirable in a factory. Not only are there safety issues, but qualified personnel are required for operation and maintenance. Digester, which does not require such a device
For example, a liquid digester is preferable for factory managers and maintenance managers.

The full-boiling digester can heat the chips more efficiently and more uniformly. It has been shown that a full liquid digester having a countercurrent heating circulation system can more efficiently and more uniformly disperse heat and a cooking chemical to a column of chips. For example, commercially available from Ahlstrom Machinery, Inc., US Pat. No. 5,489,363.
No. 5,547,012, and 5,536,3
Low solid described in each specification of 66 issue (registered trademark "L
o-Solids ”) A full liquid digester used for cooking is provided with a stream of heated cooking liquor / diluent, which when heated countercurrently to the downwardly flowing chips, heats the column of chips. It can be performed more uniformly, and the liquid can be dispersed more evenly in the chip column. In particular, if the digester that was previously configured as a vapor-phase digester is reconfigured to have a full-filled digester with a countercurrent heating circulation system, the heating function and drug dispersion that the original vapor-phase digester had Replace function,
Further improvements can be made. Heating chips directly by exposing them to steam is not an efficient way to use steam energy and also damages the cellulosic fibers and introduces new liquids into the system. The newly introduced liquid, the steam condensate, only dilutes the desired liquid present in the chip. Bringing in this water is an essential problem when the chips are directly exposed to steam. Direct steam exposure results in a further 0.1-0.3 liquor / wood ratio increase in the steam digester compared to the full digester.
This additional liquor has the disadvantage that it has no benefit in the digestion process and only increases the evaporation requirements in the recovery system. Furthermore, the steam condensate, which is the heating medium, is lost in the subsequent pulp manufacturing process. This is in stark contrast to the case of indirect steam heating. With indirect steam heating, the heating medium is not substantially depleted and is circulated in the steam circuit and can be used elsewhere if desired, or it can be reused to generate steam. The present invention avoids this inefficient use of energy and liquid.

[0015]

SUMMARY OF THE INVENTION The present invention is based on the above-mentioned conventional technique.
An object of the present invention is to provide a continuous digester device and a method of using the same , which solves the drawbacks of the technology .

[0016]

The digester of the present invention not only has some clear advantages over gas phase digesters,
Modify existing gas-phase digester or "replace",
It can be used to operate more efficiently in the same mode as a full digester.

Existing gas-phase digesters are usually not operable as full-fill digesters. This is because there is a definite difference between hardware and operation. In particular,
Normally, the vapor-phase digester cannot be operated as a full-liquid digester because in the vapor-phase digester it is essential to directly expose the chips to heating steam before dipping the chips in the liquor.
However, in the present invention, it is possible to convert the gas phase digester to effectively function as a full liquid digester,
Moreover, it retains its operational and performance advantages, and also provides an advantageous mechanism for chip heating.

There are some advantages of gas phase operation.
For example, due to the gas-filled space above the chip and liquor levels, fluctuations in the liquor flow to the digester may be small for pressure regulation. In a full liquid digester, the pressure in the tank is
For example, by adjusting the amount of wash filtrate introduced via conventional pressure control valves. Given other changing conditions, this can cause excessive fluctuations in the pressure controlled flow. However, in the gas-phase digester, the pressure is adjusted by controlling the pressure in the gas filled space. This is usually done by admitting compressed gas through an inlet near the gas-filled space at the top of the digester. The introduction of gas to the top of the digester does not interfere with the flow of liquid or the movement of the chip column below. Therefore, if there is such a gas-filled space, it will contain steam or compressed gas to alleviate the fluctuations, so the flow of liquid to the digester is
More stable.

It is also advantageous to have the ability to switch the heating mode from one to another. For example, if the heating cycle screen is clogged during full fill heating, the operator of the digester designed in accordance with the present invention will add steam to the top of the digester to heat the chips to the cooking temperature. It has the option of introducing, and without the use of a heating screen, there is room to "wipe" with a tip post to remove obstruction or backwash with liquid.

There are some examples of treating chips with countercurrent cooking liquor even in prior art gas phase digesters. However, in these digesters, it is usual to perform a process called "pre-hydrolysis" before kraft cooking. Pre-hydrolysis is an acid treatment of cellulosic material in which the hemicellulose component of the cellulose is removed to try to obtain a relatively pure form of cellulose. Such pulp is called "viscose pulp" or "dissolving pulp" and is used as a raw material for producing a cellulose film such as rayon fiber or cellophane. For example, as shown in U.S. Pat. No. 3,380,883, the chips are hydrolyzed in the gas phase of a continuous digester and then immersed in an alkaline solution to stop the acid hydrolysis reaction and then The kraft pulp manufacturing reaction is started. This alkali treatment is carried out countercurrently.

This viscose pulp manufacturing process is distinct from the kraft process of the present invention (the present invention does not apply to the production of viscose pulp). It is not desirable to remove hemicellulose from kraft pulp (hemicellulose is important for kraft pulp strength etc.)
Not only that, for example, the process described in U.S. Pat. No. 3,380,883 apparently addresses the problem of the special requirement of a pre-hydrolysis treatment followed by a kraft treatment. The countercurrent flow of alkaline liquor is apparently done because it helps separate the acidic liquor from the alkaline liquor.

The present invention also provides, in addition to the gas filled space,
A digester with a pretreatment or permeation zone on top of the digester and a method of using the digester. In conventional gas phase digesters, the chips introduced to the top of the digester are usually directly exposed to hot steam, ie steam above 130 ° C and usually above 150 ° C. At these temperatures, the cooking process begins, so
There is no room for further pretreatment or permeation operation. The reason for this, as before, is that in conventional vapor-phase digesters, this steam heating is substantially dependent on raising the temperature of the chips to the desired cooking temperature, ie 160-170 ° C.

In the present invention, the start of cooking is not limited to the top of the digester. By heating the chips to the digestion temperature below the top of the digester, preferably by countercurrent flooded heating, the digester section above the heating zone is used at a low temperature, for example, for pretreatment. be able to. For example, the top of the digester can be used for co-current or counter-current infiltration operations of chips at temperatures below the cooking temperature. The temperature of this treatment zone is 80 to 150 ° C, usually 90 to 140 ° C, preferably 100 to 130 ° C.
The temperature of this treatment can be controlled separately from the temperature of the digestion zone by adjusting the pressure and temperature of the steam introduced into the gas-filled space. The time of this treatment is 5 minutes to 2 hours, preferably 10 minutes to 6 hours.
0 minutes.

The ability to control the pretreatment temperature of the present invention is
It is particularly advantageous for treating chips having a yield or strength enhancer, such as anthraquinone and its derivatives or equivalents, or polysulfide and its derivatives or equivalents. For example, the treatment with anthraquinone is usually 90-
Limited to a temperature of 110 ° C., treatment with polysulfide is usually limited to a temperature of 90-140 ° C. With conventional gas-phase digesters, attempting such treatment at the top of the digester was not effective. Since the steam temperature is high,
This is because it usually interferes with the additive or sometimes simply decomposes the additive.

The present invention is also applicable to multi-radical digester systems, such as a two-vessel system having a permeation tank in front of the digester. The present invention provides a multi-tank system with the same flexibility as a single-tank system. For example, the permeation time in a two-vessel system can be increased by operating at a temperature below the cooking temperature at the top of the second vessel. In the current two tank type vapor phase system, high temperature steam is introduced at the top of the second tank,
There are restrictions.

[0026] In one embodiment of the present invention, remodeling method of to function as substantially fully liquid digester existing cellulose pulp vapor phase digester is provided. This existing gas-phase digester consists of a top and bottom, an inverted top separator at the top, a device that detects the chip level above the liquid level of the digester, and a digester first located at a first distance from the inverted top separator. It is equipped with a liquid level and a trim circulation system including a pump (but usually not including a heating device).
The method comprises (a) removing or moving the device for detecting chip level, and (b) a second liquid level, which is vertically positioned from the reversing top separator, at a second distance much shorter than the first distance. And (c) a trim circulation system is modified or replaced to incorporate a heating device for heating the liquid in the circulation system. Normally, the liquid level sensor is a "DP cell" that does not need to be moved even if the liquid level is changed. This "DP
The "cell" detects the head of the water column above the reference level.

The method may further include (d) providing a screen assembly for withdrawing liquor from the digester between the circulating system with the heating device and the inverting top separator. This method involves maintaining the liquid level of the digester above the chip level but below the inversion top separator when operating the digester modified (e) after (a) to (d) above. , (F) The gas filled zone above the liquid surface is heated to 160
Less than C, pressure 50-200 psig (0.34-1.3
8 MPa) and (g) withdrawing the cellulose pulp from near the bottom of the digester. That is,
The gas in the gas filled zone is usually above atmospheric pressure, for example:
50 to 200 psig (0.34 to 1.38 MPa)
And preferably 80 to 150 psi (0.55 to 1.0
3 MPa) gauge. The temperature of the gas filling zone is 16
Below 0 ° C, usually below 140 ° C, preferably 130
It is less than ℃. The gas in the gas-filled zone may be air, nitrogen or any other gas and may be steam, but it is preferably compressed gas.

In another aspect of the invention, there is provided a method of operating a cellulosic pulp digester with a top and bottom, an inverted top separator on the top and a discharge on the bottom. In this method, (a) a slurry of comminuted cellulosic fiber material and a cooking liquor (for example, a kraft cooking liquor) is introduced into a digester from an inversion type top separator, and (b) a liquid level of the digester can be changed to an inversion type top separator. Established below (c) cellulosic fibrous material level below said top separator (eg below liquid level), (d) gas filled zone above liquid level at temperatures below 160 ° C., pressure 50-200 psi
g (0.34 to 1.38 MPa), and (e) cellulose (for example, kraft) pulp is extracted from near the bottom of the digester. In the step (d), the temperature of the gas filling zone is less than about 130 ° C., the pressure is 80 to 150 p
Sig (0.55 to 1.03 MPa) is maintained. Further, (f) the cooker cellulosic material near the top of the digester is heated uniformly by establishing a countercurrent between the cellulosic material below the liquid level and the hot cooking liquor in contact therewith. In step (f), a liquid containing a high concentration of dissolved organic matter is extracted, a circulation loop is established, the liquid extracted in the circulation loop is heated, and a cooking liquor and a replenisher different from the cooking liquor are introduced. To be done. The replenisher has a low concentration of dissolved organic matter.

In another aspect of the invention, there is provided a continuous digester system for producing chemical cellulose pulp from cellulose chips. This system is a continuous digester having a top and bottom, a separator at the top of the digester,
A separator that introduces chips and liquid into the digester tank and separates the liquid from the chips to some extent, a means to establish the liquid level of the digester tank under the separator, a digester chip level below the separator (for example, below the liquid surface) means for establishing comprises means for extracting the full liquid type means for increasing the digester chip cooking temperature by heating, means for establishing a gas filled zone in the digester above the liquid surface, and digester vessel bottom pulp Nearby .

The separator is preferably a reversal type top separator, but any separation device capable of maintaining the liquid surface by allowing gas to rise may be used. The means for establishing the gas-filled zone preferably comprises means for introducing compressed gas into the gas-filled zone, although any conventional structure that performs this function can be used. The means for heating the chips in a digester in a liquid- filled manner is near the top of the digester,
A circulation screen, a pump, an indirect heater, and a circulation loop having a conduit are preferably used, and the liquid extracted from the screen by the pump is heated by the heater and returned to the digester by the conduit. Any conventional structure may be used. However, the means for heating the chips in a liquid- filled manner usually further comprises a withdrawal screen between the circulation screen and the separator, in order to heat the chips, a countercurrent flow between them and the heated liquid is applied. Establish.

As part of the means for establishing chip level, digesters are usually equipped with means for detecting chip level. For example, one or more electronic / mechanical devices, such as conventional mechanical rotating vanes with electronic strain gauges. However, any suitable conventional structure that fulfills this ultimate function may be used as the chip level establishing means. Similarly, the liquid level establishing means is preferably a DP cell, but any suitable conventional structure that fulfills its ultimate function may be used to establish the liquid level.

In yet another aspect of the invention, a method of operating a continuous cellulosic digester having a top and a bottom is provided. The method comprises: (a) introducing chips and liquor into a digester, separating the liquor from the chips in a separation zone, (b) establishing a digester liquor level below the separation zone, and (c) digesting. Establish the vessel chip level below the separation zone (eg below the liquid level), (d) heat the digester tank chips to full liquid, raise to digestion temperature, and (e) place the digester above the liquid level. A gas filled zone is established and (f) pulp is withdrawn from near the bottom of the digester. Step (e) can be performed by adding a compressed gas (for example, an inert gas) to the top of the digester tank above the liquid surface. The gas filled zone preferably has a temperature of less than about 140 ° C. and a pressure of 80 to 200 psig (0.55 to 1.38 MPa). Step (d) removes the liquid from the chip below the chip level, heats the extracted liquid, raises its temperature, and its temperature is at least about 130 ° C.
(For example, 160 ° C to 180 ° C or higher),
This is preferably done by returning this heated liquor back to the digester for recycling in the reintroduction zone below the chip level.

In another aspect of the invention, a top and bottom, an inverted top separator at the top, an outlet at the bottom, a first diameter portion of about 3-5 meters at the top, and at least about 7 meters below the top ( For example, a method of operating a cellulosic digester with a second diameter portion of 7-12 meters) is provided. This method comprises introducing (a) a ground cellulose fiber material and a kraft cooking liquor containing a free liquor into a digester via a first diameter reversing top separator, and (b) reversing the digester liquor level. Established under the top separator,
(C) Distiller cellulosic fibrous material level below the top separator (preferably, but not necessarily,
Second diameter portion), and (d) a gas filled zone above the liquid level at a temperature of less than about 160 ° C. and a pressure of 50 to 200 psi.
g (0.34 to 1.38 MPa), (e) kraft pulp from near the bottom of the digester, about 1,000 per day
It is extracted at a speed exceeding tons. Step (d) is preferably performed as described above. In the case of a digester in which the liquid level and the chip level are narrow in the upper part, step (c) is carried out to establish the chip level in the upper part.

The method further comprises withdrawing liquor from at least one location (eg, a plurality of different locations) of the reversible top separator to allow a substantial majority (eg, of the liquor) from the milled cellulosic fiber slurry introduced (eg, , 90%
With the exception of the above), the liquor can be introduced into the digester (eg above the level of comminuted cellulosic fibrous material) to at least partially carry out the liquid level establishment of step (b).

Steps (a) and (b) consist of removing liquid from two (or more) different positions of the reversible top separator (eg, spaced about 30-180 ° from each other on the circumference). Is preferably withdrawn and the liquor is used in two different lines for different purposes. Step (b) is usually performed to establish a liquid level at the first diameter section. Further, (f) the second diameter portion (for example,
Liquid above (chip level), (g) circulate and heat the extracted liquid part, and (h) reintroduce the extracted part below the liquid surface of the first diameter part. There are also steps. Step (h) may be performed by reintroducing the liquid at a plurality of different locations around the circumference of the first diameter portion.

In yet another aspect of the invention, a method of operating a continuous cellulosic digester having a top and a bottom is provided. The method comprises: (a) introducing chips and liquor into a digester, separating the liquor from the chips in a separation zone, (b) establishing a digester liquor level below the separation zone, and (c) digesting. When establishing the tank chip level below the separation zone, ensure that there is a free liquid between the chip level and the liquid surface, and (d) the free liquid when the chips are full-filled in the digester. Liquid is withdrawn from the section, the extracted liquid is heated, and the heated liquid is reintroduced into the digester below the liquid level, and (e) a gas-filled zone of the digester is established above the liquid level. Then, (f) pulp is extracted from near the bottom of the digester. An inverting top separator may be provided in the separation zone, and the method further comprises extracting the liquid from at least one position (preferably a plurality of distant positions) of the inverting top separator and introducing the comminuted liquid. Substantially all of the free liquor is removed from the cellulosic fibrous slurry and the liquor is introduced into the digester (eg, above the level of comminuted cellulosic fibrous material) to at least partially establish the liquid level in step (b). You can

In another aspect of the invention, there is provided a continuous digester system for producing chemical cellulose pulp from cellulose chips. This system has a top and a bottom, a continuous digester with a first diameter section of about 3-5 meters at the top and a second diameter section of at least about 7 meters below the top, of the digester top. A reversing separator of the first diameter part, in which a chip and a liquid are introduced into the digester tank, and the liquid is separated from the chips to some extent, a reversing separator, and the digestion tank liquid in the first diameter part under the reversing separator. Means for establishing a surface, below the liquid surface (eg second diameter section)
Establishing a digester chip level means, the full-pack means for increasing the digester chip cooking temperature by heating, means for establishing a gas filled zone in the digester above the liquid surface, and digester vessel bottom pulp Nearby Is provided with a means for extracting.

The top separator comprises at least first and second withdrawal conduits circumferentially spaced from which liquid is withdrawn, the withdrawal conduits being connected to different external structures of the digester. Is preferred. Also, the digester preferably has a shoulder portion between the first diameter portion and the second diameter portion, and the withdrawal screen is provided in the second diameter portion directly below the shoulder portion. Means for heating the chip to liquid-filled in the digester comprises a circulation loop connected to the screen extraction and the withdrawal screens. The circulation loop comprises a pump, an indirect heater, a conduit,
The liquor pumped out of the screen is heated in a heater and then returned to the digester by conduit. The conduit preferably reintroduces liquor into the digester at a plurality of different locations around the circumference of the first diameter section.

In yet another aspect of the present invention, a continuous digester system is provided for producing chemical cellulose pulp from cellulose chips. The system has a top and a bottom, with a first diameter portion at the top and a second diameter portion below the top, the second diameter portion being at least 20% larger than the first diameter portion (e.g., 100-300). %), A continuous digester having a shoulder portion formed between the first diameter portion and the second diameter portion, a withdrawal screen provided in the second diameter portion immediately below the shoulder portion, the first of the digester tank top. Inverting separator of the diameter part, the chip and the liquid is introduced into the digester tank, the inversion type separator separating the liquid to some extent from the chip, the digestion tank liquid level in the first diameter part under the inversion type separator. means for establishing, under the liquid surface (e.g., second diameter portion) means for establishing a digester chip level, means for increasing the digester vessel chip performs the full liquid heating to cooking temperature, digester above the liquid level Establish a gas filled zone That means, and means for extracting the pulp from nearby digester vessel bottom.

In another aspect of the invention, there is provided a method of operating a continuous cellulosic digester as just described. The method comprises: (a) introducing the chips and liquor into the first diameter portion of the digester, separating the liquor from the chips in the separation zone to some extent, and (b) placing the digester liquor level below the separation zone. Establish in the first diameter section, (c) Establish the digester chip level below the separation zone (eg, the second diameter section under the withdrawal screen), and (d) Fully heat the chips in the digester. When extracting, the liquid is extracted from above the chip level via the extraction screen, the extracted liquid is heated, and the heated liquid is re-introduced into the digester at the first diameter portion below the liquid surface, (E) A gas-filled zone of the digester is established above the liquid level, and (f) pulp is withdrawn from near the bottom of the digester.

In another aspect of the invention, there is provided a method of operating a cellulosic pulp digester with a top and bottom, an inverted top separator on the top, and a discharge on the bottom. This method comprises (a) a ground cellulose fiber material and a cellulose fiber.
A liquid containing free liquid in which fiber chips are not bound is introduced into a digester via an inversion type top separator, and (b)
The digester liquid level is established above the bottom of the reversing top separator, (c) the digester comminuted cellulose fiber material level is established under the top separator, and (d) the reversing top separator. Liquid from at least one of the
Taking out the introduced comminuted cellulosic fibrous material slurry or Ra遊 syneresis, those withdrawing kraft pulp from near the bottom (e) a digester (e.g., at speeds in excess of daily amount 1,000 tons).

In carrying out the method, step (d)
Can be performed such that a countercurrent flow of liquid occurs with respect to the comminuted cellulosic fibrous material near the top separator, and / or step (d) removes fibers from the withdrawn liquid with an in-line withdrawal device. And / or step (d) may be performed to cool the withdrawn liquid by at least 5 ° C. and / or step (d) may be arranged around can either be done from a plurality of locations so that withdrawing the liquid, the step (b) can also be carried out so as to substantially completely fill the full liquid state digester. The inverted top separator may be provided with a perforated screw blade, and step (d) may also be carried out using this perforated screw blade to assist the passage of the liquid stream. it can. The digester comprises a first diameter section at the top of about 3-5 meters and a second diameter section below the top of at least about 7 meters, in which case the reversible top separator must fit in the first diameter section. And step (c) can be performed to establish a level of comminuted cellulosic fibrous material in the second diameter. Also, the digester can be operated substantially completely in countercurrent flow.

According to another aspect of the invention, a continuous digester for producing chemical cellulose pulp from cellulose chips.
An apparatus is provided, the apparatus having a top and a bottom, a continuous digester having a first smaller diameter section at the top and a second larger diameter section below the top; said digester at the top of said digester a counter-rotating separator of the first diameter portion, introducing the chips and liquor to the digester, by performing the inverted top separator ;; fully liquid heating to some extent separate the liquid from the tip of the digester the chips Means for raising the cooking temperature; means for drawing liquid from the inverting top separator; and the cooking
A means for withdrawing pulp from near the bottom of the can is provided.
The can unit uses the inversion type top separator to change the liquid level of the digester
Above the bottom of the digester and the chip level below the digester level
To be operated with characterized Rukoto.

The means for withdrawing liquid from the reversible top separator may include at least first and second withdrawal conduits circumferentially spaced to withdraw the liquid. The conduits are connected to different external structures of the digester. The digester may be provided with a shoulder portion between the first diameter portion and the second diameter portion and a withdrawal screen may be provided in the second diameter portion directly below the shoulder portion. .
The system further said means for heating the chip to liquid-filled in the digester is provided, This has can be provided with the withdrawal screens, the connected circulation loop to the withdrawal screen. The circulation loop includes a pump, an indirect heater, and a conduit, and the liquid extracted from the screen by the pump is heated by the heater and then returned to the digester by the conduit. The inverted top separator can be equipped with a porous screw blade. Extraction means comprise at least one conduit can further comprise an in-line extracting device connected to said conduit, the digester is substantially completely full <br/> liquid state, ie liquid surface Between the inversion top separator and the top of the digester and a small gas space between the top of the digester and the liquid level.

This and other objects of the invention will become more apparent upon a close examination of the following detailed description of the drawings and a reading of the claims.

[0046]

DETAILED DESCRIPTION OF THE INVENTION The accompanying drawings will now be described in detail. 1 and 2 show the upper parts of two conventional continuous digesters. Top of the vapor phase digester 10 is shown in Figure 1, the full liquid digester 20 is shown in FIG. These digesters may be the only digester in the pulp making system, or may be, for example, one of two vessels.
In the latter case, the system is equipped with a second tank, known in the art as a permeation tank. These digesters usually receive a slurry of comminuted cellulosic fibrous material (usually wood chips) and cooking liquor (eg, kraft white liquor). This slurry is typically supplied by a feeder, such as Glens Falls, NY (USA).
It is first processed on a low level ("Lo-Level") feeder, sold by Ahlstrom Machinery, Inc. of Lens Falls. The gas-phase digester of FIG. 1 is typically fed to conduit 11 with a slurry of chips and liquid. The slurry fed to the digester is carried out using a conventional vertically arranged screw conveyor 12 known in the art as an "inverted top separator". The slurry is sent upward to the separator 12, and the chips and liquid are
It is discharged from the top of the separator 12 as indicated by the arrow 13. As the slurry is sent upwards, excess liquid is removed from the slurry using a cylindrical screen 14 and returned to the feeder via conduit 15. The chips and the liquid 13 discharged from the separator 12 fall from the gas filled zone 16 and reach the chip mountain 17. To continue steam heating the chips, the chip pile 17 is maintained above the cooking liquor level 18, as seen in FIG. After steam heating, the chips are immersed in the cooking liquor,
Moving down from the level indicated as 18, the cooking process continues.

In order to improve the heat distribution of the entire chip column and chip pile 17, the vapor-phase digester 10 is provided with a liquid withdrawing screen 19 and a circulation system 21. The liquid is extracted outward in the radial direction and returned to the tip column through the pipe 24 arranged in the middle. The circulation system 21 is usually the pump 2
5, the liquid heater 25 ′ may be provided. The liquid withdrawal screen 19 and associated circulation system 21 (including pump 25 and pipe 24) are "trim circulation" in the art.
It is called. Under the trim circulation screen 19, both heat and chemicals are evenly distributed and the cooking process continues.

In the vapor phase digester 10, the level of the chip pile 17 is usually monitored by a gamma ray source and detector. These are shown schematically at 26 and 26 ′ in FIG. 1, respectively, and are arranged opposite each other near the tip pile 17. The radiation source and detectors 26 and 26 'detect whether or not chips are present in the pile 17, and the chip level is controlled by changing the slurry flowing into the tank 10 or changing the pulp flowing out of the tank 10. can do. The withdrawal of pulp from the bottom of the vessel 10 is done using entirely conventional withdrawal equipment.

In addition to the chip level, the liquid level in the gas phase digester 10 must also be monitored and controlled. Liquid level 18
Are usually monitored using conventional liquid level detectors. This is shown schematically at 27 in FIG. 1, for example a “DP cell” or the like, which detects the head of the liquid column above the reference level.

The pressure and temperature of the gas filling zone 16 must also be monitored in the digester 10. The pressure in zone 16 is usually maintained using an air compressor. The compressor is
In response to a decrease in reference pressure, air or digester 10
Other gases that are inert to the chemical process of E. coli, such as almost pure nitrogen gas, are pumped into the top of the digester. Excess pressure, such as that caused by gas entrained in the incoming chip slurry, is usually released using a conventional pressure relief device, shown generally at 28 in FIG. The temperature at zone 16 is monitored and controlled by applying pressure steam from steam source 23 via conduit 22.

As with the vapor digester 10 of FIG.
Conventional full liquid digester 20 of a slurry of chips and liquor is supplied from the supply device via conduit 60. The slurry supplied to the digester 20 is carried out using a conventional "top separator" 61 which is a downward screw conveyor. The liquid introduced from the separator 61 is a double arrow 6
2 and the chip is indicated by a single arrow 63. Excess liquid is removed from the slurry through the cylindrical screen 64 as it is fed down on the conveyor 61 and returned to the feeder (eg, high pressure feeder) via conduit 65.

Chip 6 dropped from separator 61
3 form a chip level 66. Since the digester 20 is in a fully liquid state, the zone 67 above the chip level 66 is filled with liquid, gas zone is normally absent. Chip level in the bath 20 in a fully liquid, usually conventional mechanical rotary blade 68 of Ichiki or more base which is installed along the inner surface of the tank (e.g., US, Ahlstrom Inc. NY Gurensu Falls (Sold under the name "K-1000") with an associated electronic strain gauge. The presence or absence of chips is detected by the rotational movement of the blades 68 and the chip level is calculated in percent based on a mathematical algorithm.
No gamma radiation equipment (eg 26 and 26 'in Figure 1) is required. As with the vapor-phase digester, the chip level of the full liquid digester 20 can either change the inflow of the slurry,
It can be controlled by changing the flow rate of cooked chips.

In contrast to the digester 10 of FIG. 1, the chips at the top of the pile 66 are usually not heated until they are completely at the cooking temperature, but rather must be heated so that cooking does not begin. This is typically done using one or more heating digester circulation loops 70. The heating can be done in cocurrent or countercurrent, but the circulation loop 7 shown in FIG.
0 is heating the chip countercurrently. The slurry first passes through a liquid removal (withdrawal) screen 71 that draws liquid from the slurry via conduit 78. The liquid extracted via the conduit 78 can be sent to the chemical recovery or the digester 2
It may be sent to the chip pretreatment before 0. Withdrawing the liquid in this manner induces a free liquid flow, as indicated by the double-lined arrow 76, to flow countercurrently to the downward tip flow indicated by the single-lined arrow 77. The heated liquid 76 is supplied to the circulation system 70.
Obtained from The liquid is first screen 72, conduit 73,
Separated from the slurry via pump 79 and in an indirect steam heater 74 (eg, to a temperature of 135 ° C to 170 ° C).
It is heated and returned near the screen 72 by a return conduit 75 located in the middle. Cooking liquor, for example kraft white liquor, is usually added to this circulatory system. Low solids (registered trademark "Lo-Sol", sold by Ahlstrom, Inc., described in US Pat. Nos. 5,489,363, 5,547,012, and 5,536,366.
ids ") if the digestion takes place in vessel 20, conduit 73
It is also possible to send a part of the liquid taken out via the chemical recovery system to replace it with a liquid having a low concentration of dissolved organic matter, for example, a combination of a cooking liquid and a diluting liquid (or diluting water). After heating to the digestion temperature in the circulation system 70, the slurry can be digested, but can be further processed under the screen 72.

FIG. 3 shows a digester 30 which implements one of the preferred embodiments of the present invention. The digester 30 is constructed by modifying the digester 10. At that time, the sensor element 26,
26 'will be removed or otherwise immobile, additional rotary vanes 68 will be added, additional heaters 74 will be added, and perhaps the "trim circulation" relocated. usually,
The DP cell 27 is neither changed in position nor removed. Alternatively, the digester 30 may be newly installed.

As in the system of FIG. 1, a chip and liquid slurry is fed to the top of the vapor digester 30 via conduit 31 and a conventional inversion top separator 32 sold by Ahlstrom. To be done. This slurry is usually introduced into the digester 30 at a temperature of 90-130 ° C. This temperature depends on how the chips are processed in the feeder before the digester 30. For example, a dispenser is sold by Ahlstrom Machinery, Inc. of Glens Falls, NY, and is sold in US Pat.
No. 5476,572, and 1995 April 25 of U.S. Application No. 08 / 428,302 No. of low level as described in the specification (registered trademark "Lo-Level") when a supply device, the slurry Enters the digester at about 95-100 ° C. If the chips are fed in a conventional feeder, for example in a horizontal pressure steam treatment vessel, the slurry enters the digester at 115-120 ° C. As is conventional, the top separator 32 removes excess liquid from the slurry and drains chips and liquid as indicated by arrow 33 as the slurry is fed upwards. The removed liquid is returned to an upstream process via a conduit 34, for example, to a high pressure feeder or a permeation tank sold by Ahlstrom.

The chip 33 is exposed to the gas atmosphere 35,
After that, it enters the liquid surface 36, falls, and reaches the chip pile 37. The gas atmosphere 35 above the liquid level 36 is typically composed of gas entrained in the digester 30 with air or chips and a slurry of liquid. It is also necessary and, if desired, the air can be replenished with another gas, such as steam, nitrogen, or other suitable gas that can be used to maintain processing or the desired pressure. In the sulfite pulp manufacturing apparatus, the gas space 35 is normally filled with sulfur dioxide (SO2) gas. The atmosphere 35 has a temperature of 1
Less than 60 ° C, usually less than 140 ° C, preferably 130 ° C
Less than (may be less than 120 ° C) and pressure is 50 to 20
0 psig (0.34 to 1.38 MPa), preferably 80 to 200 psig (0.55 to 1.38 MPa),
For example, 80-150psi (0.55-1.03MP
a) Maintained in gauge. To maintain the pressure in space 35, compressed gas may be introduced from source 39 via conduit 38, as is conventional in the art. Also, excess pressure can be relieved using a conventional pressure relief device 80, as is known in the art. Digester 30
At the top of the, the tip indicated by arrow 42 flows co-currently with the liquid indicated by double arrow 43.

The liquid level 36 is typically monitored by a conventional liquid level indicator, such as a "DP cell" 27. However, other devices can also be used. The liquid level is adjusted by adjusting the inflow and outflow of the liquid to and from the digester 30, for example, the conduit 51.
Alternatively, it can be varied by adjusting the outflow rate of another conduit that increases or decreases the liquid to the digester 30. Chip level 37 is also independently monitored using one or more conventional mechanical rotary vane and strain gauge device combinations 68 mounted on the wall of digester 30 near chip level 37. As before, chip level 37
Can be adjusted by increasing or decreasing the flow of chips entering the digester 30 or by increasing or decreasing the flow of pulp exiting the digester 30.

[0058] chips flowing, so it is preferable not exposed to steam in a gas atmosphere 35, the heating of the chip of the cooking temperature is fully liquid formula, for example, using one or more liquid circulation system It is preferable to carry out. One of the preferred methods of processing chips is screen assembly 40.
And 41 are used. The liquid is withdrawn via the screen assembly 41, via conduit 44, usually using a conventional pump 53. The withdrawn liquid is heated via indirect heat exchanger 45 (eg to at least 130 ° C.) and then returned via conduit 46 to near screen 41. Usually, cooking liquor, such as kraft white liquor or black liquor, is added to conduit 44 from conduit 47. Preferably, US Pat. Nos. 5,489,363 and 5,54
The low solid (registered trademark "Lo-Solids") digesters described in Nos. 7,012 and 5,536,366 and sold by Ahlstrom, Inc. are also digesters 3
It is done at zero. In this case, a diluting liquid, for example, a washing filtrate, a bleach plant filtrate, or a liquid having a low concentration of dissolved organic matter such as weak black liquor, can be added to the conduit 44 via the conduit 48.

The heated liquor, which is reinserted into the digester 30 via conduit 46, flows countercurrently as indicated by double arrow 49 to the downwardly flown tip as indicated by arrow 50. preferable. The liquid 49 is induced countercurrently as a result of the liquid being drawn via the screen 40 into the conduit 51. The flow 49 of the liquid is usually 140-
Heat to a cooking temperature of 180 ° C. The liquid flow shown in FIG. 3 is countercurrent, but the heated cocurrent liquid also
It can be used instead of or with a countercurrent liquid. The liquid in conduit 51 can be sent to a chemical recovery system or used to pretreat chips prior to or during digester 30 treatment. The options are
A return circulation system 52 can also be provided.

After passing through the screen 41, the heated chip slurry, which is normally maintained at a temperature to continue the pulp making process, undergoes some further treatment in the latter zone of the digester 30 and is then discharged. It doesn't matter.

Since the temperature of the atmosphere 35 is low (preferably 130 ° C. or lower), a yield and / or strength improving agent (for example, anthraquinone and its derivative, and / or polysulfide and its derivative or an equivalent agent) is used. The pulp can be treated without compromising the additives, after which the pulp can be introduced into tank 30. Atmosphere 35
If the treatment (or continuous treatment) with anthraquinone or a derivative thereof is performed, the temperature is 90 to 110 ° C.
If the treatment (or continuous treatment) with polysulfide or its derivative or equivalent is carried out, it should be kept at 90 to 140 ° C. The time of the treatment in the atmosphere 35 is 5 minutes to 2 hours, preferably about 10 minutes to 60 minutes, and the desired condition is as shown in FIG.
It is maintained by adjusting the temperature and pressure of the steam introduced at 38 points.

FIG. 4 shows another embodiment of the present invention, a continuous digester system 100, similar to the embodiment shown in FIG. Many of the items shown in FIG. 4 are similar to those shown in FIG. 3, if not identical, and therefore the numbers in FIG. 3 are indicated by prefixing “1”.
For example, the inverting top separator 132 of FIG.
It is similar to the reversible top separator 32 of FIG.

The system of FIG. 4 comprises a conduit 131 for supplying a slurry of chips and liquor to digester 130. The slurry is introduced into the separator 132, and the separator lifts the slurry upward with a screw conveyor, while the liquid in the slurry is a conventional cylindrical screen,
The small space is removed via conduit 134. The chips and unremoved liquid are discharged from the separator as indicated by arrow 133 and exposed to the steam (or gas) atmosphere 135. Steam (or gas) from source 139 to conduit 13
Introduced via 8. The tip and excess liquid are
Drop to the liquid marked as 6, and the chip is 1 mountain
Deposit at 37. The level of liquid and chips is usually
Adjusted as described for the embodiment shown in FIGS. 1, 2 and 3.

The difference between the digester system 100 and the system of FIG. 3 is that the system of FIG. 4 has a first diameter portion (inlet portion) 9
5, a digester 130 having a diameter of 5, which is smaller than the second diameter portion (main body) 98. The second diameter portion 98 is at least 20% larger than the first diameter portion 95 (eg, about 100% to 300% larger). This portion 95 is preferred when treating the cellulosic material in a large scale digester, for example, a digester 130 that produces more than 1,000 tons per day. This portion 95 typically has a diameter of only about 3-5 meters, while
The main tank (second diameter portion 98) of the digester 130 is about 7 to 12
It may have a diameter of more than a meter. This aspect is
The invention is not limited to digesters having an inlet diameter different from the diameter of the main tank, and the present invention is still effective even if the diameters of the portion 95 and the portion 98 are substantially the same. Difference in diameter between the portion 95 and the portion 98, or may be how introducing present invention to an existing system, in particular particularly suggestive whether can be introduced into an existing double-chamber type full liquid digester system.
In the case of such equipment, the main modification item is to replace the existing inlet or top separator with the inverting top separator 132 and the inlet 131 shown in FIG.

The embodiment of FIG. 4 is provided with a liquid outlet 86 from the top separator 132, and liquid is taken out from the top separator in addition to the liquid taken out via the conduit 134. Outlet 134,86 are preferably arranged in (as well as other outlet provided) to each other about 30 to 120 ⁰ intervals on the circumference. This newly provided liquid outlet 86 draws more liquid from the separator 132 than is normally withdrawn via conduit 134 and is sold by a supply device, such as Ahlstrom Machinery, Inc., Glens Falls, NY, USA. High-pressure feeder or low level (registered trademark "Lo-Leve
l ") Slurry liquid to the supply device or slurry liquid to the bottom of the pretreatment tank, eg sluice liquid to the permeation tank can be supplied. The outflow rate of conduit 86 is 0.5 to 5 cubic meters (ie m ³
/ Tp), but usually about 1 to ³ m ³ / tp.

Other methods can also be used to remove substantially all of the free liquor from the introduced chip slurry. For example, changing the structure of the separator 132 itself,
For example, the screw and the extraction screen portion of the separator 132 may be made longer than before, or may have a tapered screw-type press structure that substantially functions as a plug feeder, so that almost no free liquid is contained (for example, normally, free liquid is not released). It is also possible to drain a slurry which contains less than 10% of the initial amount of liquor, preferably less than about 5%) or no liquor at all. Alternatively, simply add more fluid to the BC by providing the additional conduit 86 'seen in FIG.
It can be withdrawn from the return conduit 134 itself.

The above method of removing liquid from the inverted top separator 132 is used to separate the processing liquid introduced into the conduit 131 and used in the previous processing from the liquid under the separator 132, shown as liquid level 136. Especially applicable. For example, the treatment prior to the tank 130 is a treatment with a cooling liquid (No. 08/911, 36 filed on Aug. 7, 1996).
For such) as described in 6 Pat, even if the in conduit 134 excess coolant is not exception, since away of from the conduit 86, the hot liquid represented by liquid level 136, the cold liquid is just Very little or no introduction required.
This system is also advantageous in that it contains strength or yield-enhancing additives such as those present in tank 130 to other pretreatment liquids, such as anthraquinone or polysulfide or hydrogen sulfide and their equivalents and derivatives. It is time to isolate the liquid. The liquor removed from conduit 86 can be sent to a drug recovery system or, if desired, used anywhere in the pulp mill, including the bleach plant.

A heating circuit 85 is shown in FIG. 4 and, in connection with this, a withdrawal screen 87, a conduit 88, a pump 89, a conduit 9 located just below the shoulder 99.
0, indirect steam heater 91, return conduit 92, liquid dispersion header 93, and multiple inlet nozzles 94. This circulation is used to drain the liquid underneath the top separator 132, heat it, and add new liquid as desired. For example, a cooking liquor such as kraft white liquor or black liquor, or another liquor containing cooking additives, or a diluting liquid having a lower dissolved solids concentration than the liquor at screen 87 is circulated through conduit 96 to circulation 85. Can be introduced.
Liquid may be withdrawn from conduit 97 at the same time as or instead of being introduced via conduit 96. For example, when countercurrent flow of liquor at the top of digester 130 is desired, rather than introducing liquor through conduit 96, conduit 9
It is also possible to drain the liquid from 7. The system shown in FIG. 4 is particularly applicable for retrofitting an existing double-chamber type full liquid digester system. In this case, the existing top circulation screen is used as the liquid extraction screen 87. Single tank digesters and vapor phase digesters can also be modified to practice the present invention.

Similar to the operation of the digester of FIG. 3, operation of the digester 130 can be performed from the feeder or from previous treatments.
For example, a slurry of comminuted cellulosic fibrous material, e.g., softwood chips, delivered from a permeation tank is introduced via conduit 131 to an inverted top separator 132, liquid is removed from the separator and piped to the previous system or tank. Returned via 134. These are the same as conventional ones. Further, as in the conventional case, since the screw conveyor of the separator 132 lifts the slurry upward and the liquid is removed, as a result, the chips and the remaining liquid are discharged from the top of the weir of the separator 132 as shown by an arrow 133. It falls like a waterfall. The chips discharged from the separator 132 fall down from the gas / steam atmosphere 135,
Upon entering the liquid in the bath 130, a liquid level 136 is formed.
The chips are then deposited on chip stack 137 and then processed as desired. For example, methods that can be processed include the following US Pat. Nos. 5,489,363 and 5,536,3.
No. 66, No. 5,547,012, No. 5,575,89
0, 5,620,562, and 5,662.
Low solid such as described in 775 No. specification (registered trademark "Lo-Solids") cooking process or U.S. Pat EAPC described in the specification of No. 5,635,026,
(Registered trademark) cooking process. However, in the present invention, additional liquid can be withdrawn from the separator 132 via conduit 86. This additional liquid withdrawal restricts or substantially eliminates the free liquid introduced from conduit 131 (ie, not bound to the tip) from flowing to the internal liquid indicated by liquid level 136. That is, it is preferable to keep (less than about 10% of the free liquid remains). Further heating and addition of liquid can also be performed by the circulation 85 as described above, for example, using a valve in the line 96 controlled by the liquid level sensor of the liquid level 136. The compressed gas / steam introduced at 139 is preferably introduced in the same manner as the embodiment of Figure 3 and establishes the same conditions.

The invention described with reference to FIGS. 3 and 4
The present invention provides a method for producing a wood pulp by treating a comminuted cellulosic fiber material, or a method for producing a kraft pulp by modifying an existing gas-phase digester. And processing becomes more uniform, changes are less sensitive to chip level fluctuations, channeling is less likely to occur, there is no need to treat the radiation source to detect chip level, and as a result digestion is easier to operate. Cans are provided.

In the embodiment of FIG. 5, there is provided a continuous digester system 100A similar to that of FIG. 4 in accordance with the present invention. The difference is, since the digester vessel 130A is substantially is fully liquid state, is that the compressed gas zone does not exist on the liquid and chips. In this aspect, structures corresponding to those of FIG. 4 are designated with the same reference numerals.

[0072] tank 130A is, because it is substantially fully liquid state,
Liquid level 136, conduit 138, or gas source 1 of the embodiment of FIG.
39, or structures related thereto, are not provided. The embodiment of FIG. 5 is particularly advantageous for retrofitting existing single- or dual-vessel digesters, eg, vapor phase digesters, as these components and structures are not required. Conduit 1 in this manner
Since the liquid withdrawn via 34,86,86 'may contain fibers or may be above the desired temperature, the fibers may be placed in one or more of the conduits 134,86,86'. It is permissible to provide a device for filtering or cooling the liquor, which can then be used elsewhere on the pulp mill (eg, as a slurrying liquid at the bottom of the permeation tank of a two tank system). For this purpose, for example,
In-line withdrawal device 101 is shown in conduit 134 in FIG. Such an in-line extraction device 10
1 may be as shown in FIG. 2 of US Pat. No. 5,401,361 (the disclosure of which is incorporated herein by reference), or instead of extraction device 101. A conventional indirect heat exchanger is installed in the
The liquid in 34 may be cooled, for example, by at least 5 ° C (eg, cooled in the range of about 10-30 ° C).

In the preferred mode of operation of the digester 130A of FIG. 5, the liquor is withdrawn via one or more of the conduits 134, 86, 86 'so that it is digested, as indicated generally by the arrow 102. A countercurrent liquid flow occurs at the top of the can tank 130A. This countercurrent liquid flow is, for example, 85 in FIG.
It can be heated by the circulation shown in the section. This circulation is only attached to one of the conduits 86, 86 ', 134, shown schematically as circulation 103 in FIG. The heated liquor can be reintroduced into tank 130A or used to treat the cellulosic material with a strength or yield enhancing additive such as anthraquinone. Under such circumstances, circulation 85 is not necessary, rather the circulation below tank 130A can be used to heat the liquid.

Aspect 100B of the digester system of FIG.
Substantially the same as the system of FIG. 5, except that the tank 130B
There, instead of being kept essentially fully liquid state, since only the liquid is filled up to the top of separator 132 as shown schematically in locations 104 in FIG. 6, the compressed gas source 139 It is possible to add gas to the small gas phase volume between the top of bath 130B and liquid level 104, as shown in FIG.

In both the embodiment of FIGS. 5 and 6, the inner top separator 132 is operable to allow liquid to flow freely in either the forward or reverse direction. Digester 130A, 13
At the top of 0B, the liquid and cellulosic material (eg, chips) can be countercurrent or cocurrent, and if desired, the entire digester 130A, 130B can be countercurrent. Further, in either mode, as schematically shown in FIG. 7, the porous screw blade 106 can be used as the screw blade of the top separator 132. The screw vanes 106 are rotatable about the shaft 105 and are suitable for assisting in passing a stream of liquid, in any form, in any size, in any number of holes 1
The one using 07 may be used.

Since the present invention has been shown and described herein in what is presently considered to be the most practical and preferred embodiments, many partial modifications are within the scope of the invention. It will be apparent to those skilled in the art that what can be done. Therefore, the scope of the appended claims should be construed broadly to include all equivalent structures and methods.

[Brief description of drawings]

FIG. 1 is a schematic side view of a typical inlet part and an upper part of a conventional gas-phase digester, showing a partial cross section and a partial elevation.

[2] In a typical inlet and schematic side view of the upper portion of the conventional full-fluid digester is a similar view as Figure 1.

FIG. 3 is a schematic side view of the digester of the present invention, a typical inlet and top of the digester used to carry out the method of the present invention, similar to FIGS. 1 and 2. Is.

FIG. 4 is a view showing another embodiment of the digester of the present invention, and FIG.
It is a figure similar to.

FIG. 5 shows another embodiment of the digester of the present invention for carrying out the method of the present invention, similar to FIG.

FIG. 6 shows yet another embodiment of a continuous digester with many similarities to the embodiment of FIG.

FIG. 7 is a top view of an exemplary variation of the screw of the reversible top separator of the digester of FIGS. 5 and 6, showing a cross-section of the shaft together.

[Explanation of symbols]

10, 20, 30, 130, 130A, 130B ... Digester, 11, 15, 22, 31, 34, 38, 44, 4
6,47,51,60,65,73,75,78,8
6,86 ', 88,90,92,96,97,131,
134, 138 ... Conduit, 12, 32, 61, 132 ... Inverting top palator, 13, 33, 42, 43, 4
9, 62, 63, 76, 77, 102, 133 ... Arrows,
14, 64 ... Cylindrical screen, 16, 35, 135 ... Gas filled zone, 17, 37, 66, 137 ... Chip pile,
18, 36, 104, 136 ... Liquid level, 19, 71, 7
2, 87 ... Liquid withdrawing screen 21, 52, 70,
85, 103 ... Circulatory system, 23, 139 ... Steam source, 2
4 ... Pipe, 25, 53, 79, 89 ... Pump, 25 '
... Liquid heater, 26, 26 '... Gamma ray source / sensor, 27
... DP cell, 28,80 ... Pressure relief, 39,139 ...
Gas source, 37, 55 ... Chip level, 40, 41 ... Screen assembly, 45, 91 ... Indirect heater, 67 ... Liquid full zone, 68 ... Rotating blade, 74 ... Heater, 93 ... Header, 94 ... Inlet nozzle, 95 ... First diameter portion, 98
… Second diameter part, 100,100A… Digester system,
101 ... In-line extracting device, 106 ... Screw blade, 105 ... Shaft, 107 ... Hole.

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kyo. Henrickson Finland SF-00441, Helsinki, St. Nelikya 2, P.H. Oh. Box 5 (56) Reference JP-A-10-331085 (JP, A) JP-A-54-138602 (JP, A) US Patent 3429773 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21C 1/00-11/14

Claims (9)

(57) [Claims] 1. A method of operating a cellulosic pulp digester having a top and a bottom, a reversible top separator on the top, and a discharge port on the bottom, comprising the steps of: (a) comminuted cellulosic fibrous material; Introducing the slurry with the liquid containing the free liquor into the digester via the inversion top separator, (b) establishing the digester liquid level above the bottom of the inversion top separator, and (c) digesting Establishing a can cellulosic fiber material level below the reversible top separator, (d) withdrawing liquid from at least one location of the reversible top separator to remove free liquid from the introduced comminuted cellulosic fiber material slurry, and ( e) A method characterized by extracting kraft pulp from near the bottom of the digester at a rate of 1000 tons per day or more. 2. The method of claim 1, wherein step (d) is performed such that a countercurrent flow of liquid occurs with respect to the cellulosic fibrous material near the top separator. 3. The method of claim 1 wherein step (d) is further performed to remove fibers from the withdrawn liquid with an in-line withdrawal device. 4. The method of claim 1, wherein step (d) is further performed to cool the withdrawn liquid by at least 5 ° C. 5. The method according to claim 1, wherein the step (d) is performed so as to extract the liquid from a plurality of locations arranged around the periphery. 6. The method of claim 1, wherein step (b) is performed to fill the digester with liquid. 7. The inversion type top separator is provided with a perforated screw blade, and step (d) is performed so as to assist the passage of a liquid flow using the perforated screw blade. The method of claim 1. 8. The digester comprises a first diameter portion 3-5 meters at the top and a second diameter portion at least 7 meters below the top, wherein the reversible top separator has a first diameter. 2. The method of claim 1 wherein the step (c) is performed to establish a level of cellulosic fibrous material in the second diameter section. 9. Process according to claim 1, characterized in that the digester is operated in countercurrent flow.