JP5993309B2 - Apparatus and method for separating harmful substances in a pulp manufacturing process - Google Patents

Description

  The present invention relates to the problems arising from the separation and removal of hazardous substances in chemical pulp mill fiber lines during the production of chemical pulp, because if the harmful substances are not removed, it will cause problems in the process and This is because there is a possibility of damage.

  Grinded cellulosic fiber materials, such as wood chips, that are processed in conventional pulp manufacturing processes are usually sand, dust, stone, various pieces of metal (eg nails, pieces of metal wire, or bolts and nuts), etc. Non-cellulosic harmful substances, metal fragments, or other heavy cellulosic materials (eg knots) or non-cellulosic materials. The density of this harmful substance is typically at least 10% higher (eg, at least 50% higher) than the density of the cellulosic material being processed. During chip manufacture, it is possible to remove a very large portion of such material, but some of the material is inevitably passed through the digester supply system and optional impregnation vessel, as well as the digester itself. Usually, this material is separated from the chip in the delivery system using several separators. This type of separator is described in US Pat. No. 6,315,128. Hazardous substances such as sand can also be removed from liquid streams such as liquids used in pulp production, cooking liquors and cleaning liquids. In the digester system, the cooking solution is removed from the impregnation and digester vessel and returned to the cooking process (especially the digester feed system). Conventional sand separators remove sand and other particles from the cooking solution that is circulated through the chip carrier in the digester plant. U.S. Pat. No. 4,280,902 describes a cyclone-type separation device for removing undesirable materials, particularly sand and equivalents, from a liquid stream in a supply system. Sand separators usually have a tangential inlet into a cylindrical vessel. Sand and other heavy particles vortex down into the vessel and enter the separation hopper, through which the sand and particles move into the collection tank. In the upper part of the cylindrical chamber, an outlet for the cleaned solution is arranged.

  In the prior art apparatus, the digester supply system, which is usually a return circulation, has one cyclonic separator with a relatively large diameter. It must have a reasonably high capacity to continuously process the entire return circulation stream. With the appropriate size, wear and thus damage is also reduced. As a result of the large size, the separation capacity is not always efficient for harmful substances consisting of small particles.

US Pat. No. 6,315,128 U.S. Pat. No. 4,280,902 Finnish Patent Application No. 20010851 US Patent No. 5,000,083

  The object of the present invention is to further enhance and improve the functionality of the supply system for the cooking process. In particular, an object of the present invention is to improve the removal of undesirable materials, particularly sand, from the digester supply system. It is also an object of the present invention to provide an apparatus that can be used to remove undesirable substances consisting of small particles, such as from low-viscosity fiber suspensions in screening, even in the pulp production stage after the digester. That is.

  It is a particular object of the present invention to provide a method and apparatus that can more effectively separate the finest sand particles from the return circulation in the digester supply system. It is just the finest sand particles that cause the wear of the device. If the finest sand particles cannot be separated from the circulation, they can accumulate in the process, thereby hindering the process and reducing the functional capabilities of the device.

  In order to achieve these objectives, the present invention is an apparatus for separating harmful substances, in particular sand, from a liquid stream or low viscosity fiber suspension in a chemical pulp production process, A cyclone-type separator having a simple chamber, the upper part of the vertical chamber having a tangential inlet and an accept outlet for creating vortex motion for the flow to be cleaned, the cone of the separator The lower part of the shape, ie the bottom, relates to a device with a reject outlet. The present invention provides that the apparatus comprises two or more cyclone-type separators connected in parallel so that their inlets lead to at least one supply flow path having at least one inlet, The accept outlet leads to a common discharge flow path having at least one outlet, the reject outlet leads to a common discharge flow path having at least one outlet, and the common discharge flow path releases the accept and reject It is connected to at least one auxiliary separator having a plurality of pipelines for

  The device according to the invention thus comprises a first step arranged in series with two or more separators and a second step, usually of the cyclone type, usually with one separator. Prepare. Accepts are cleaned fluids or suspensions, and rejects are the parts in which harmful substances have accumulated during separation.

  A low viscosity fiber suspension is a fiber suspension produced in a digester and having a viscosity of less than 1.5%, usually 1.2-1.5%. Separation of knots in the screen chamber of the fiber line in a chemical pulp mill involves knot washing, after which sand is separated from the fiber suspension stream. After the sand is removed from the screen room fine screening reject, the reject is washed. The present invention can be used in connection with such sand separation.

  According to a preferred embodiment of the present invention, the cyclone separator is arranged in a common housing so that the accept discharge channel, the supply channel and the reject discharge channel are vertically overlapped. . A space is provided between the supply channel and the reject channel, and the space communicates with the reject discharge channel, whereby the pressure in the space becomes the same as the pressure in the reject channel.

  According to a preferred embodiment of the invention, the device has two supply circuits and two accept circuits. Thereby, the supply flow path is divided into at least two compartments with separate inlets by an intermediate wall and the accept discharge flow path is divided into at least two flow paths with separate outlets by the intermediate wall. The This embodiment is preferred in the screen chamber downstream of the digester, whereby one compartment preferably processes the fiber suspension from the knot wash, and the other compartment rejects fine screening. Process. According to the present invention, it is possible to carry out such sand separation with one apparatus. The accept stream is directed to different processing stages in a manner known per se.

  In accordance with an embodiment of the present invention, a diluent line is provided in the reject discharge channel of the device to dilute the portion fed into the auxiliary separator. Preferably, the diluent is a stream to be cleaned. If the reject viscosity is excessive, the dilution ensures optimal separation in the auxiliary separator, which is sometimes referred to as the second step. Dilution adjusts the back pressure, thereby providing a balance of pressure in the first step.

  According to a preferred embodiment of the present invention, the supply flow path to be cleaned is pressure-measured to adjust the supply pressure using a valve located in the supply pipe connected to the inlet of the supply flow path. Provide a device.

  In accordance with a preferred embodiment of the present invention, the pressure differential in relation to the supply flow path and the accept discharge flow path for the stream to be cleaned is used to regulate the outgoing accept flow using the measured pressure differential. Measuring the pressure difference in relation to the reject discharge path and the accept discharge path of the auxiliary separator to regulate the outgoing accept flow using the measured pressure difference. To be.

  According to a preferred embodiment of the present invention, a supply line for the flow to be cleaned is connected to the reject discharge flow path in order to direct the flow to be cleaned as a diluting liquid that dilutes the reject guided to the auxiliary separator. , Whereby the diluent flow comprises a pressure measuring device for adjusting the supply pressure of the diluent using a valve.

  In accordance with a preferred embodiment of the present invention, the pressure differential in relation to the supply flow path and the accept discharge flow path for the stream to be cleaned is used to regulate the outgoing accept flow using the measured pressure differential. In order to introduce a diluent and dilute the reject introduced into the auxiliary separator, the supply line for the vapor to be cleaned is connected to the reject discharge flow path and thereby measured In order to regulate the outgoing accept flow using the measured pressure difference, the pressure difference is measured in relation to the diluent line and the acceptor discharge flow path of the auxiliary separator.

  According to a preferred embodiment of the invention, the device is provided in a side stream separated from the return circulation of the digester feed system in the chemical pulp mill for separating harmful substances such as sand.

  According to a preferred embodiment of the present invention, the device is provided in a chemical pulp mill screen chamber for separating harmful substances such as sand.

The present invention also relates to a method for separating harmful substances, such as sand, from a liquid stream in a system supplying fiber material containing cellulose into a high pressure treatment tank in a chemical pulp manufacturing process. In the implementation of
The low pressure fiber material stream is pressurized in the transfer device;
A high-pressure fiber material stream is directed from the moving device into the treatment tank;
-The solution is removed from the fiber material in the treatment tank. The method is
The removed solution is divided into at least first and second solution streams;
The first solution stream is fed into the low-pressure fiber material stream upstream of the transfer device;
Toxic substances are removed from the second solution stream by subjecting the second solution stream to centrifugal force in an apparatus having two or more cyclonic separators connected in parallel and arranged in a common housing; The second solution stream is removed into a cleaned solution stream and a first reject directed to an auxiliary separation to obtain a second cleaned solution stream and a second reject. Divided,
The cleaned second solution stream is fed upstream of the transfer device into the low-pressure fiber material stream;

  The cleaned solution stream is mixed and the mixed stream is fed into the low-pressure fiber material stream upstream of the transfer device. The cleaned solution stream is fed into the low-pressure fiber material stream using the pressure energy contained in the solution stream. This takes advantage of the pressure in the return line discharged from the high pressure tank, so that a separate pump for carrying the flow is not required in the secondary line. Usually, the pressure in the main line is not adequate to carry the side stream, so the separation of the side stream from the main stream requires a device such as a pump to increase the pressure in the side line.

  The fiber material introduced into the high-pressure treatment tank is usually a chip.

  According to a preferred embodiment of the invention, the second stream is smaller than the first stream because the first mentioned is a side stream in the return line of the digester feed system. Typically, the second flow comprises less than 30% of the first flow volumetric flow rate (eg, liters / second).

  According to a preferred embodiment of the invention, the supply of the second stream leading to the separation of harmful substances such as sand is controlled by adjusting its pressure.

  According to a preferred embodiment of the present invention, the cleaned flow is controlled using a pressure difference between the supply pressure of the second flow and the pressure of the cleaned flow.

  According to a preferred embodiment of the present invention, the second cleaned solution stream exiting the auxiliary separator causes the pressure difference between the first reject stream and the second cleaned solution stream. Controlled.

  According to a preferred embodiment of the invention, the first reject stream directed into the auxiliary separator is diluted.

  The present invention will be described in more detail with reference to the accompanying drawings.

It is a figure which shows the solution by a prior art. FIG. 2 illustrates the use of a preferred process according to the present invention. Figure 2 shows a preferred device according to the present invention. FIG. 2 shows details of the device along the line AA in FIG. FIG. 3 is a side view of a single separator according to the present invention. Figure 2 shows a preferred device according to the present invention. Figure 2 shows a preferred device according to the present invention. FIG. 2 schematically shows the principle for adjusting the device according to the invention. FIG. 2 schematically shows the principle for adjusting the device according to the invention. FIG. 2 schematically shows the principle for adjusting the device according to the invention. It is a figure which shows the separation capability of the sand of a separator.

  FIG. 1 shows a prior art recirculation loop connected to a digester or impregnation vessel, known for example from Finnish patent application No. 20010851. In this system, the tip is moved using at least one, preferably two high pressure suspension pumps 251, 251 ′, rather than a high pressure feeder, to carry the tip to the inlet of the digester 11. The chip is introduced into the steam treatment tank 221. The steam treatment tank 221 is preferably a DIAMONDBACK® steam treatment tank as described in US Pat. No. 5,000,083 that accepts steam through one or more conduits 22. The chips treated with steam exit the tub 221 and enter the metering device 223, which can be a pocketed rotor or screw type device.

  Release from the metering device 223 can occur directly into the conduit or chute 226. On the other hand, it is possible to place a pressure isolator, such as a pocket-type rotor-type isolator device, between the metering device 223 and the chute 226, the isolation device, for example a conventional low-pressure feeder, as 224 dotted lines It is represented. Cooking liquor is added into the chute 226 (see line 226 'in FIG. 1), resulting in an observable level of tip and solution suspension (not shown). The suspension is discharged from the chute 226 to the inlet of the pump 251 via the curved outlet 250. Typically, the suspension going to the inlet of the pump 251 is increased with the solution coming from the solution tank 253 through line 254.

  The embodiment shown in FIG. 1 has two pumps, but alternatively only one pump or two or more pumps connected in series or in parallel can be used.

  The pressurized and normally heated suspension is discharged from the pump 251 ′ to the line 234. Line 234 carries the suspension to the inlet of continuous digester 11. Excess solution is removed from the suspension through screen 12 in a conventional manner. This excess solution is returned to supply system 210 via line 235 and preferably enters solution tank 253 and is used for slurrying in line 250 through line 254. If desired, the solution in line 235 can be conveyed through sand separator 237. The sand separator 237 can be designed for use with or without pressure according to the desired mode of operation.

  However, unlike other known systems that use high pressure feeders, in the operation of the apparatus of FIG. 1, it is not important to return the pressurized loop 235 to the inlets of the pumps 251, 251 '. The energy available for the flow in line 235 can be used anywhere in the chemical pulp mill as needed. The method of using the return line 235 pressure, which is typically about 10.4 to 27.6 bar, depends on the operating mode of the supply system 210. When the vessel 226 is operated without pressure (essentially at atmospheric pressure), the returned solution in line 235 is returned to essentially atmospheric pressure and then fed into line 250. One way to do this is to use a pressure regulating valve 58 and a pressure detector 59 in line 235. The opening of the valve 58 is controlled to a predetermined reduced pressure in the conduit 235 downstream of the valve 58. Furthermore, the solution tank 253 can be designed to operate as a “flushing tank” so that the hot pressurized solution in the conduit 235 can quickly evaporate and steam to the bath 253 can be vaporized. It can be used as a supply source. This steam can be used in the tank 221 via the pipe line 60, for example. However, in the preferred embodiment, pumps 251 and 251 'in line 252 are increased to increase the flow leaving pump 251' by line 61 and pump 62, or with or without pump 64. The pressurized solution in line 235 is used to increase the flow between them by line 63.

  FIG. 1 shows a one-way (check) valve 65 located in line 234 that prevents pressurized flow from returning to pump 251 or 251 '. In addition, conventional automatic (eg, solenoid operated) isolation valves 66 and 67 are disposed in lines 234 and 235, respectively, to isolate pressurized lines 234 and 235 from the rest of supply system 210. . In one preferred mode of operation, a conventional pressure switch 68 is disposed downstream of pump 251 ′ in line 234. The switch 68 is used to monitor the pressure in the line 234 and if the pressure deviates from a predetermined value, the conventional controller 69 automatically closes the valves 66 and 67 to automatically digest the digester 11. Is isolated from the supply system 210.

  Although the aforementioned processes and apparatus have proven to be efficient, the object of the present invention is to further improve the operational functionality of the cooking process, particularly the removal of harmful substances such as sand from the digester supply system. It is to improve.

  FIG. 2 shows the separation of harmful substances such as sand according to the invention applied to the digester supply system of FIG. Components of FIG. 2 that are essentially the same as those found in FIG. 1 are indicated by the same reference numerals.

  In the process according to the invention, the side stream 236 is separated from the digester return line 235 to the digester supply system. For the present invention, return line 235 is the primary return line and secondary line 236 is the secondary return line. Here, the pressure in the return line 235, which is typically about 10.4 to 27.6 bar, is utilized, so that no separate pump is required to carry the flow into the secondary line. Normally, the pressure in the main stream is not adequate to carry the side stream, so separating the side stream from the main stream requires a device such as a pump to increase the pressure in the side stream. In the device according to the invention, the pressure for feeding the side stream is usually about 4 to 6 bar.

  The secondary line 236 is equipped with a sand separation facility 260 according to the present invention to remove sand and corresponding particles from the return circulation. This is the finest part that would otherwise accumulate in the digester supply system, for example, causing significant wear of the pumps 251-251 '' used for tip movement and thus their operation. It is possible to remove even the finest parts that impair the characteristics.

  The main return line is usually supplied with white liquor via line 269. The liquid in the main return line 235 is conveyed through a heat exchanger 268 for heating the liquid in the line or cooling it before feeding it into the chute 226. This is desirable when the solution in this line is at a temperature above the flushing temperature corresponding to the pressure in line 226 so that flushing in line 226 can be minimized. Become. The liquid is directed into line 226 through the solution tank to slurry the tip suspension. Steam is introduced into the steam tank 221 via a conduit 265.

  The solution cleaned in the sand separator can be directed to various locations in the supply system as needed and to the suction side of the pumping devices 251-251 ″ (or high pressure feeder). These are marked with x as an exemplary method. The cleaned solution is usually passed through line 264 to the steam bath 221 or chip suspension together with other parts introduced into the supply system from lines 263, 266 or lines 261, 267. To line 226 for slurrying. A flow of black liquor from the fiber filter is introduced into line 267. The cleaned solution in line 236 can also be directed to the main return channel via lines 262,270.

  The sand separation system is preferably used in conjunction with a continuous digester 11, but other vertical (usually at least about 10 bar overpressure) pressurized treatments, such as in association with an impregnation vessel. It can also be used in association with a tank.

  3, 4 and 5 show the sand separator according to the invention in more detail. The device 300 according to the invention comprises several cyclonic separators 30 connected in parallel to the substance to be cleaned. In FIG. 5, a single separator is shown as an accurate diagram. A single separator 301 includes a vertical chamber 302, whose upper end 303, or supply end, includes a tangential inlet 304 for generating vortex motion for the flow to be cleaned. Yes. The upper end 303 of the chamber also comprises a purged liquid or accepting discharge tube 305, which is positioned so as to be concentric with the central central axis of the chamber. The bottom of the conical lower end 306, i.e. the reject portion 307, is provided with a portion containing sand and corresponding particles, i.e. an outlet 308 to the reject.

  The apparatus 300 includes two or more cyclonic separators 301 connected in parallel. A tangential inlet 304 for the liquid to be cleaned arranged in the upper part 303 of the chamber leads to a common supply channel 309. Supply channel 309 includes an inlet 310 through which liquid to be cleaned in the separator is directed into the apparatus. A supply channel 309 surrounds the upper portion 303 of the vertical chamber.

  The end of the accept tube 305 disposed outside the chamber is provided with an accept outlet 311 that leads to a common accept discharge channel 312. The discharge channel 312 is arranged vertically above the chamber 302 and comprises an accept, ie at least one outlet 313 for discharging the liquid or fiber suspension cleaned in the separator from the device 300. Yes.

  The chamber reject outlet 308 leads to a common reject discharge flow path 314 located below the essentially vertical chamber. This discharge channel 314 has at least one outlet through which rejects are removed. The discharge channel is operatively connected to at least one cyclonic auxiliary separator 316 for further processing of rejects. Thus, the reject outlet is connected to the auxiliary separator inlet 315. In the separator 316, the reject is further divided into an accept portion and a reject portion. The auxiliary separator 316 has a conduit 319 for releasing the accept and a conduit 318 for discharging the reject.

  The cyclone separators 301 connected in series are arranged in a common housing 320 so that the accept discharge channel 312, the supply channel 309 and the reject discharge channel 314 overlap each other in the vertical direction. The Between the supply channel 309 and the reject channel 314, a space 321 is formed surrounding the conical lower portion 306 of the separator. The intermediate space 321 is associated with the reject discharge flow path through an opening 322 that surrounds the conical reject end 307 so that the pressure in the intermediate space 321 is within the reject discharge flow path 314. It becomes the same as pressure. Therefore, the pressure outside the conical portion 306 is also a rejection pressure. By placing the separator 301 in a common pressure vessel 320, the safety and performance of the device 300 is improved. Also, the auxiliary separator 316 is preferably disposed within the same housing 320. If the individual separator conical section 306 is completely worn and broken, other separators will operate and the liquid flow discharged from the broken separator will remain inside the pressure vessel and the intermediate space 321. And entering the reject discharge space 314, the operating capability of the device is not substantially reduced and no emergency situation occurs. In prior art devices, the return circulation of the digester supply system typically has one cyclonic separator with a relatively large diameter (eg 800 mm). It must have a sufficiently high capacity to continuously treat the entire return circulation flow. Also, with proper sizing, wear and thus damage is reduced. However, as the size is increased, the separation capacity of the device is weakened so that return circulation can cause accumulation of harmful material in the form of harmful sand and fine particles in the digester feed system.

  FIG. 4 shows a cross section AA of the device of FIG. 3, ie the separator 301 viewed from above the supply flow path. The separators are preferably arranged in a staggered manner, but other positioning with respect to each other is possible. The liquid to be cleaned flows in the supply flow path 309 and enters the separator tangential inlet 304 as shown by arrow 323, creating a swirling flow in the separator chamber. A cleaned liquid or accepting discharge tube 305 is placed in the center of the separator, which pipes into a cleaned liquid discharge channel 312 located above the supply flow channel. Communicates.

FIG. 6 shows the apparatus of FIG. 3, but in order to dilute the reject, a pipe 324 for the diluent and an opening 325 for the diluent are provided in the reject discharge channel 314. Accordingly, the viscosity of the portion fed into the auxiliary separator 316 can be adjusted as desired within the reject discharge channel 314. Usually, dilution D ₁ is a liquid fed into the apparatus. If the reject viscosity is excessive, dilution ensures an optimum viscosity for the auxiliary separator, ie the second step.

FIG. 7 shows an alternative embodiment for the apparatus of FIG. In this case, intermediate walls 326 are disposed in the supply and accept flow paths, so that these flow paths are in two spaces, namely the first (309 ′) and second (309 ″) supply flow paths. And the first (312 ′) and second (312 ″) accept flow channel sections. Both supply channel spaces are provided with inlets 310 ′, 310 ″ for feeding the stream to be cleaned into the device. Correspondingly, both accept channel sections have outlets 313 ′, 313 ″ for directing the accept out of the device. The first set of separators 301 ′ receive their supply through a supply channel section 309 ′, and the second set of separators 301 ″ receive their supply through a second supply channel section. receive. In the first set of separators 301 ′, the accept is directed into the first accept flow path section 312 ′, and in the second set 301 ″, the accept is in the second accept flow path section 312. Guided in ''. From both sets of separators, reject is being released into the reject channel 314 via the auxiliary separator 316 as a single stream, also accept A ₃ are formed, and reject is separated, the rejected It is removed via line 318. This embodiment is particularly suitable for sand separation in screen room knot removal and sand removal from rejects in fine screening, so that such sand removal can be carried out in the same apparatus. become. The knot separation releases stream F ₂ , rejects from the screen chamber becomes stream F ₁ , and accepts streams become A ₂ and A ₁ , respectively. The supply channel compartment and the accept channel compartment may be of the same size or of different sizes depending on the amount of material being processed. Accept streams A ₂ , A ₁ and A ₃ are directed to the next process.

  Figures 8 to 10 schematically show the principle for adjusting the device according to the invention. In FIG. 8, the device according to FIG. 3 is connected to a return circulation sidestream of the digester feed system. The supply line (in the form of a channel 236 according to FIG. 2) involves the adjustment of the supply pressure, which is performed using a pressure regulating valve 331 and a pressure detector PF in the channel 236. It is important that the cleaned liquid from the accept flow path 312 is pumped into a space without back pressure and reaches the suction side of the pumps 251-251 ″ and the desired position in the process. The opening of the valve 331 located in the supply pipe line 327 connected to the inlet of the supply channel of the device is controlled to a predetermined reduced pressure in the line 327 downstream of the valve 327. The accept flow path is accompanied by a pressure measurement PA1. Using the pressure difference PF-PA1 indicated by the pressure detector PDIC and the valve 332 disposed in the accept discharge line 328 connected to the outlet of the accept flow path, the accept flow is broadened according to the circumstances of each process. Can be adjusted within the range. The reject discharge channel 314 is accompanied by a pressure measurement value PR1. The auxiliary separator accept discharge channel 329 is accompanied by a pressure measurement PA2. The accept flow is regulated using a pressure differential PR1-PA2 and a valve 333 located in the accept discharge tube 330 connected to the accept outlet of the auxiliary separator.

  FIG. 9 shows flow regulation when the apparatus shown in FIG. 6 is connected to the return circulation sidestream of the digester feed system. The connection shown in FIG. 9 is different from the embodiment of FIG. 8 in that the dilution section 334 is connected to the reject discharge channel. Diluent is introduced as a side stream 334 from the supply line 327 of the apparatus. The pressure measurement PD is preferably in the reject discharge channel 314. A valve 335 is disposed in the diluent line 334. The opening of the valve 335 is controlled after the valve to a predetermined reduced pressure in the diluent line. The pressure in the return circulation is typically about 10 bar and the pressure in the supply line 327 is typically reduced to about 6 bar and in the dilution line 334 to about 3-4 bar. The flow in the accept line 330 is regulated by a pressure differential PD-PA2 between the dilution line 334 and the auxiliary separator accept line 330 using a valve 333.

FIG. 10 shows the flow regulation when the apparatus of FIG. 7 is connected to the flow F ₂ downstream of the screen chamber knot wash and the screen chamber reject flow F 1. In that case, the apparatus comprises two parallel-connected feeds F ₂ and F ₁ and two accept removals A ₂ and A ₁ for the material to be cleaned. The supply line is accompanied by adjustment of the supply pressure, and the adjustment is performed using a pressure adjustment valve and pressure detectors PF1 and PF2. The first supply line F ₁ flows into the first set of separators 301 ′ and the second supply line F ₂ flows into the second set of separators 301 ″. The openings of the valves 401, 402 in the supply line are controlled after the valves to a predetermined reduced pressure in them. The flow in the accept lines A2 and A1 is regulated using the pressure difference between the supply line and the accept line and corresponding valves, similar to those for FIGS. The first and second sets of separators have a common reject channel 314 that leads to an auxiliary separator 316. The latter flow of the accept line A _3, until the as already described which is adjusted using the pressure difference between the accept line and reject line.

  FIG. 11 shows the sand separation capacity of different size separators as a function of particle size. The particle size is determined according to the ISO classification, with 1 representing the largest particle size and 5 representing the smallest particle size. When the separator diameter is 200-300 mm, small particles are much more easily separated than when using a separator with an essentially larger diameter, usually 800 mm.

  An advantage of the present invention that is worth mentioning is that, in connection with the digester feed system, the separation of sand can be placed in the return circulation side stream, in which case the flow uses the digester pressure. To be implemented. The cleaned side stream is returned to the suction side of the pump in the chip supply line to the process position as required. The device according to the invention is small. The device also has a high wear resistance since the wear part of the separator, such as the conical part, is preferably made of a ceramic material. The sand separated in the entire apparatus is collected in a single sand collector located in the reject discharge line of the auxiliary separator and removed periodically. The apparatus is equipped with a separator having a small diameter, usually 100-300 mm, preferably 150-300 mm, thus providing a high separation level for small particle sand. The apparatus typically comprises 10-15 separators. The connection part and the adjustment device connected thereto can be arranged closely. Since the device is easily understood, maintenance and repair of the device is simple. By changing the number of separators used in the device housing, the capacity can be easily changed and optimized.

  The description so far relates more particularly to the use of the sand separator according to the invention in connection with a digester feed system. Equipment shall be used for separation of sand in the screen chamber after the digester chamber, separation of sand for knot separation, and separation of mixed knots / rejection of the screen chamber and other corresponding applications. Is also possible.

Claims (15)

An apparatus for separating harmful substances from a liquid stream or a low-viscosity fiber suspension having a viscosity of less than 1.5% in a pulp manufacturing process, each apparatus having a vertical chamber Having two or more cyclone-type separators, wherein the upper portion of the vertical chamber comprises a tangential inlet for creating a vortex motion for the flow to be cleaned, and an accepting outlet, The bottom of the conical lower part of the separator is provided with a reject outlet, the inlets of the two or more cyclonic separators open into at least one supply channel having at least one inlet; Accept outlets open to a common accept discharge channel having at least one outlet, and the reject outlets have a common reject discharge channel having at least one outlet. Open, said common reject release passage, the device connected to at least one auxiliary separator having a plurality of conduits for discharging the accept and reject,
The plurality of cyclone separators are disposed in a common housing, and the common accept discharge channel, the common supply channel, and the common reject discharge channel are vertically arranged in the common housing. overlapping located, also the intermediate space between the common said common reject discharge channel and the supply channel of is formed, and
The apparatus wherein the intermediate space communicates with the common reject discharge flow path so that the pressure in the intermediate space is the same as the pressure in the common reject flow path . The supply flow path is divided into at least two compartments with separate inlets by an intermediate wall, and the accept discharge channel is divided into at least two compartments with separate outlets by an intermediate wall. The apparatus of claim 1 . The apparatus according to claim 1 or 2 , wherein the common reject discharge flow path is provided with a pipe line for a diluting liquid in order to dilute a portion fed to the auxiliary separator. In order for the common supply flow path for the flow to be cleaned to adjust the supply pressure by a valve located in a supply line connected to the inlet of the common supply flow path, a pressure measuring device is provided. apparatus according to any one of claims 1 to 3, characterized in that it comprises. To regulate the flow of the accept leaving using the measured pressure difference, the pressure difference in relation to the common supply channel and said common accept orifices of for the liquid to be the cleaning The common reject discharge channel and the acceptor discharge channel of the auxiliary separator for adjusting and adjusting the outgoing acceptor flow exiting the auxiliary separator using the measured pressure difference. 5. A device according to claim 4 , characterized in that the pressure difference is measured in relation to To regulate the flow of the accept leaving using the measured pressure difference, the pressure difference in relation to the common supply channel and said common accept orifices of for the flow of said cleaning A supply line for the stream to be cleaned is connected to the common reject discharge channel for introducing a diluent and diluting the reject introduced into the auxiliary separator. Pressure associated with the diluent line and the accept discharge flow path of the auxiliary separator to regulate the accept flow exiting the auxiliary separator using the measured pressure difference. The apparatus according to claim 4 , wherein the apparatus is adapted to measure a difference. Apparatus according to any one of claims 1, characterized in that is positioned in the separated sub-stream from the return circulation of chemical pulp mill digester feed systems up to 6. Apparatus according to any one of claims 1 to 7, characterized in that disposed in the screen chamber chemical pulp mill. In a pulp manufacturing process, a method for separating harmful substances from a liquid stream in a system that supplies fiber material containing cellulose into a high-pressure treatment tank, comprising:
A flow of low-pressure fiber material is pressurized in the transfer device;
A flow of high-pressure fiber material is directed from the transfer device into the treatment tank;
In the method in which the solution is removed from the fiber material in the treatment tank,
The removed solution is divided into at least first and second solution streams;
The first solution stream is fed into the low-pressure fiber material stream upstream of the transfer device;
Hazardous substances are removed from the second solution stream by subjecting it to centrifugal force in an apparatus comprising two or more cyclonic separators connected in parallel and disposed in a common housing. In the separator, the second solution stream is divided into a cleaned solution stream and a first reject, the first reject being a second cleaned solution stream; hazardous materials in order to obtain a second reject containing guided to the auxiliary separation, common accept discharge passage, a common supply channel and a common reject orifices are positioned to overlap in the vertical direction, the common An intermediate space is formed between the supply flow path and the common reject discharge flow path, and the intermediate space communicates with the common reject discharge flow path, whereby the pressure in the intermediate space is The common It is the same as the pressure of the injected flow path,
The method wherein the cleaned second solution stream is fed into the low-pressure fiber material stream upstream of the transfer device. The method according to claim 9 , wherein the harmful substance is sand. 11. A method according to claim 9 or 10 , wherein the second flow is smaller than the first flow. 12. Method according to claim 9 , 10 or 11 , characterized in that the supply of the second stream leading to the separation of harmful substances is controlled by adjusting its pressure. 13. The cleaned flow according to any one of claims 9 to 12 , wherein the cleaned flow is adjusted using a pressure difference between the supply pressure of the second flow and the pressure of the cleaned flow. The method according to one item. The second cleaned solution flow exiting the auxiliary separator is adjusted using a pressure difference between the first reject flow and the second cleaned solution flow. 14. A method according to any one of claims 9 to 13 , characterized in that 15. The method according to any one of claims 9 to 14 , characterized in that the first reject stream directed into the auxiliary separator is diluted.

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