SE0500751A1 - Feeding of finely divided fibrous material - Google Patents

Abstract

Method and system for feeding distributed material to a treatment vessel (11). Instead of a so-called High-pressure feeder 'uses a high-pressure pump device consisting of one or two centrifugal beads (251, 251) of the helical screw type. »

Description

ÄWAPATENT AB Office / AdministratorStockholm / Gunnar Henningsson / MPT ANDRITZ INC Application No. Our reference SE-21018422 9 l (_ FEEDING OF DISTRIBUTED FIBER MATERIAL The invention relates to systems for feeding a distributed cellulosic material to a treatment vessel. needed compared to prior technology.

U.S. Patents 5,476,572, 5,635,025, 5,622,598 and 5,766,418 represent the first major breakthrough of over forty years in the art of feeding undisturbed cellulosic carrier material to a treatment vessel. These patents show fl your designs for feeding boilers by e.g. Use a suspension pump, marketed by Andritz Inc., Glens Falls, NY, under the brand name Lo-Levelm Feed System. As described in these patents, the system required becomes much simpler and smaller as such a pump is used to feed a suspension to a high pressure feeder, and operation and maintenance become easier. Previous systems that use a high-pressure feeder, such as the High-Pressure Feeder, marketed by Andritz Inc., but without such a pump, do not differ significantly from the systems that have been sold and built since the 1940s and 1950s.

The present invention relates to an improvement of the systems disclosed in the above-mentioned patent. The present invention completely eliminates the need for feeder devices, such as High-Pressure Feeder, by utilizing a high pressure pump device to transfer a suspension of distributed cellulosic feedstock directly to a treatment vessel, such as a digester.

The reaction of cooking chemicals with a distributed cellulose-containing material to produce chemical pulp requires temperatures between 140 - 180 ° C. The aqueous solutions of the chemicals used to treat the material would boil at these temperatures, chemical pulping is typically performed commercially in pressure vessels under an overpressure of at least about 10 bar (about 150 psig). In order to maintain this pressure, especially when performing a continuous boiling process, special measures must be taken so that the pressure does not disappear when the material is fed into the pressure vessel. According to the prior art, a so-called High-Pressure Feeder. This feeder is a purpose-built device containing a rotor provided with kor ccks which serve as a means for transferring material suspension from a low pressure to a high pressure and at the same time act as a valve which prevents loss of pressure. This complicated and expensive device has long been considered a necessary component for feeding suspensions of disintegrated cellulosic material into pressurized vessels, typically at an elevated temperature, especially in continuous boilers.

According to the invention, a system is provided which replaces the High-Pressure Feeder - which for over forty years has been considered necessary for continuous cooking - which greatly simplifies the construction of a pulp mill.

According to one aspect of the present invention, a system for producing chemical pulp from a distributed cellulosic support material, such as wood ice, comprises the following components: a basing vessel in which a distributed cellulosic support material is based to remove air therefrom; a pressurized vertical treatment vessel having an inlet for suspending distributed cellulosic material in its upper part and an outlet in its lower part; and a pressure generating feeder for pressurizing and suspending material from the basing vessel and transferring the inlet of this treatment vessel, said pressure generating feeder consisting of one or more high pressure suspension pumps located below the upper part of the treatment vessel.

The one or two pumps preferably comprise a first and a second high-pressure suspension pump arranged in series, each having a pressure value, one inlet and one outlet, the inlet of the first pump being in operative communication with the basing vessel, the outlet of the first pump being operatively connected to the second pump. and the second pump has a higher pressure value than the first pump. The suspension pumps may consist of spiral screw-type centrifugal pumps which are capable of pressurizing a suspension 10 3 with a relatively high content of solid material (in one or more steps) to a pressure of at least about 5 bar overpressure.

A typical unit of measurement which indicates the relative amount of solid material in a suspension-containing solid material and liquid is the so-called Liquid / solids ratio. In this application, this ratio refers to the ratio between the quantity, ie. the volume, liquid and quantity, i.e. the volume, mass or wood material being transported. Typical conventional centrifugal type liquid pumps are limited to pumping liquids with a solids content of not more than 3%. This solids content corresponds to a liquid / solids ratio of about 33. In the suspension pump according to the invention, the liquid / solids ratio of the suspension being pumped is typically 2-10, preferably 3 - 7 and most preferably 3 - 6. The suspension pumps according to the invention transport suspensions with a much higher content of solids than a conventional pump can handle.

A liquid return line may be connected to the upper part of the treatment vessel, which contains liquid separated from the suspension at the upper end of the treatment vessel. The return line may be in (preferably a continuous boiler). functional connection with an inlet or an outlet in one of the Suspension pumps, either directly or indirectly. The liquid return line is preferably connected to a pressure reducing device for reducing liquid pressure in the return line before the liquid is led to the inlet or outlet of the suspension pump. The pressure reducing device can be of various kinds, such as a relief vessel and / or a pressure regulating valve in the return line or other conventional construction for effective reduction of the pressure in a line without adversely affecting the liquid. When a relaxation vessel is used, the liquid outlet from the relaxation vessel is connected to the inlet of the first suspension pump and the steam generated in the relaxation vessel can be used in a basing vessel.

Alternatively, the pressure reduction can be achieved or even avoided by using a jet pump which uses the pressurized return line as a source of pressure for pressurized liquid. A jet pump can be used together with one or more of the suspension pumps to transport suspension to the digester. A conventional ice shaft as well as other alternative components are preferably arranged between the basing vessel and the at least one suspension pump, the basing vessel being located above the ice shaft and the ice shaft above the suspension pump / s. The suspension pump (s) are typically located at a distance of at least about 10 meters (30 feet) below the upper end of the digester and typically more than about 15 meters (about 50 feet) below.

When the high pressure feeder device is abandoned, it is desirable to use other devices to maintain one of the functions of the high pressure feeder, namely to prevent pressure relief should an abnormal operating condition occur. Namely, the high pressure feeder device typically prevents backflow of liquid from the digester to the feed system. The device which prevents pressure relief according to the present invention is preferably separated from said at least one suspension pump, although in some cases the inlet or outlet of the suspension pumps may be designed so as to prevent pressure relief. The means for preventing pressure relief may comprise an automatic separation valve in the suspension lines leading suspension from the pumps to the upper end of the treatment vessel and the return line from the treatment vessel, a conventional control means being connected to the separation valves which control them by means of a detector connected to a suspension. . The devices which prevent pressure relief may also comprise a non-return valve in the suspension line and / or other valves, containers, detectors, control devices or similar hydraulic, mechanical or electrical components which are capable of preventing pressure relief.

A system incorporating the invention may also include means for increasing the liquid flow to the inlet of the second suspension pump or to another pump or feeder, such as a liquid line containing a lower pressure fluid in the inlet of the second suspension pump, a line between the liquid line and the inlet of the liquid line and the inlet. . The liquid line can be constituted by the return line from the treatment vessel and the line can be directly connected to the return line. The liquid return line may be connected to a relaxation vessel as described above and the line may be connected to the liquid outlet of the relaxation vessel.

A method of feeding dispersed cellulosic material to the upper end of a treatment vessel using a system according to the invention may comprise the following steps: (a) the material is based to remove air therefrom and the storage material. (b) the material is suspended in a cooking liquor to effect a suspension of liquid and material; and (c) the suspension is pressurized to a pressure of at least 5bar overpressure below the upper end of the treatment vessel (eg at least 9 meters or 30 feet, preferably at least 15 meters or 50 feet, below it) and pressurized material is transferred to the upper end of the treatment vessel, the pressurizing step continuing that the suspension is affected by one or more of the high-pressure suspension pumps, of which at least one first is a spiral screw-type centrifugal pump.

Such a method may comprise further steps wherein: (d) liquid separated from the original suspension in the upper end of the treatment vessel is returned to the at least one pump, and (e) the pressure in the suspension is sensed while being transferred to the upper end of the treatment vessel and the suspension to the upper end of the treatment vessel. from the upper end of the treatment vessel is switched off if the sensed pressure falls below a predetermined value. There may also be a further step (f) in which the liquid is evaporated off by tension as it is returned in the execution of step (d) to produce steam, and the steam is used in the execution of step (a).

In conventional pulp mills, the cellulosic material, typically softwood or hardwood, but also other cellulosic material can be present, can be added in various forms. It can e.g. added as sawdust, as fl ice, as logs, as long pruned trees (ie longwood) or even as whole trees (ie whole trees). Depending on the source of cellulose in the wood supply, the wood is typically transformed into ice so that it can be handled and processed in a cooking process. S.k. Ice choppers convert longwood or logs into ice that is typically stored in open ice piles or in ice silos. This reception, handling and storage of the ice is carried out in a section of a pulp mill called a wood farm. From the wood farm, the ice is typically transported to the actual pulp mill to begin the pulp production process.

~ «. In conventional woods, the ice is stored in silos from which the ice is discharged, typically by means of a rotating or vibrating silo dispenser, to a conveyor. The conveyor typically consists of a belt conveyor which receives the ice and for them the treatment vessel of the boiler. Since the wood yard is typically located at a distance from the boiler vessels, the conveyor is typically long. Such a conveyor can have a length of up to about 800 m. Treatment systems that do not use the Lo-Levelm feeding system, which is marketed by Andritz and is described in the previously mentioned US patent, require that the conveyor be located at a higher level, typically at a height of at least 30 m (100 feet), to feed the ice to the first pulp production inlet. These conveyors and their support structures are very expensive and make up a significant part of the cost of the boiler's feed system.

In one embodiment, the concept of transporting a suspension of ice to the wood yard is extended. Transport of a disintegrated cellulosic berm material to a boiling process may consist of the following steps: (a) Untreated fl ice is fed into a first vessel. (b) Suspension liquid is fed into the first vessel to form a suspension of material and liquid. (c) The suspension is discharged from the vessel to the inlet of the at least pressure generating and transporting device. (d) The suspension is pressurized in a pressure generating and transporting device and transferred to a treatment vessel.

The first vessel is typically an fl issilo or binge. This binge preferably has a one-dimensional convergence outlet without agitation or vibration, such as the DIAMONDBACK® bin described in U.S. Patent 5,000,083, although agitation or vibration may be used. The bin can also have two or fl your outlets that feed to your transport or transport your transport devices. The vessel can operate at a higher than atmospheric pressure, e.g. 0.1 - 5 bar. If the vessel is operating at a higher than atmospheric pressure, an entry pressure separating device of some kind is needed at the vessel inlet to prevent relief of the pressure. This device may be a star-type separator, such as a Low-Pressure Feeder or Air-Lock Feeder marketed by Andritz, or a screw-type screw-type feeder as described in U.S. Patent 5,766,418. 7 The suspension liquid may be any liquid available in the pulp mill. , such as fresh water, steam condensate, kraft white liquor, black liquor, green liquor or sul fi liquor or any other liquid resulting from the boiling process. The liquid may consist of a heated liquid, e.g. hot water or steam with a temperature of 50 - 100 ° C. If the vessel is a pressurized vessel, liquid temperatures above 10 ° C can be used. The liquid may, even if not necessarily, contain at least one active cooking chemical, eg sodium hydroxide (NaOH), sodium sulfide (NAZS), polysulfide, anthraquinone or their equivalents or derivatives.

The pressure generating and transporting device in steps (c) and (d) preferably consists of one or fl your suspension pumps. The transport system may also contain one or fl your storage or equalization containers as well as transport devices. The one or fl your transport devices may include at least one device with degassing capacity so that undesired air or gas can be removed from the original suspension. During transport, the ice may be subjected to a treatment of some kind, e.g. deaeration or impregnation with a liquid, preferably a liquid-containing cooking chemicals, such as those described above. The suspension can also be subjected to at least one pressure variation during transport, such as changing the pressure from a first pressure to a second, higher pressure and then to a third pressure which is lower than the second pressure. As described in U.S. Patents 4,057,461 and 4,743,338, the pressure variation in a suspension of ice and lye improves the impregnation of the ice with this lye. The pressure pulsations can be achieved by the variable outlet pressure in a series of transport devices or by controlled pressure relief in the suspension between the pumps.

The material does not have to come into contact with liquid in the vessel, but the liquid is rabbit-fed into it first in or below the outlet of the vessel by means of a jet pump arranged there. This liquid is preferably pressurized so that the material and the liquid form a pressurized suspension of material and liquid.

The treatment vessel in step (d) may typically be a basing vessel as described above, preferably a DIAMONDBACK® basing vessel. The vessel may also consist of a storage or leveling container in which the material is stored before the treatment. Since the transport process may require extra lye that is not needed for the under-treatment or storage, a dewatering device of some kind may be arranged between the transport device and the treatment vessel. A preferred dewatering device consists of a Top Separator marketed by Andritz. This TopSeparator can be of standard type or a "reverse" Top Separator. The device can be a separate unit or be mounted directly on the treatment vessel. The liquid removed from the suspension by means of the dilution device is returned to the first vessel or to the transport device to serve as a suspension liquid. The liquid can also be used elsewhere where it is needed in the pulp mill. The liquid can be heated or cooled as desired. The liquid can e.g. heated by bringing it into indirect heat exchange contact with any gained liquid stream, e.g. a wastewater stream with a temperature higher than 50 ° C. The liquid is also typically pressurized by using one or more conventional centrifugal type liquid pumps.

The treatment vessel in step (d) may be a basing vessel which feeds one or more of the transport devices of the type described above.

Feeding ice to a cooking process is not limited to a chemical pulping process, but can be used in any post-cooking process where distributed cellulosic feedstock is transferred from one place to another. The pulping processes to which the invention can be applied include all chemical pulping processes, all mechanical pulping processes and all chemical mechanical or thermomechanical pulping processes for batch or continuous treatment.

Not only does the invention reduce the size of the distributed cellulosic carrier material transport system and its cost, but if the distributed cellulosic carrier material is treated during transport, the number and size of the actual treatment vessels can be reduced. The system can e.g. eliminate the need for conventional pre-treatment or impregnation vessels before the boiler. The system also has the potential to improve the pulp mill's overall energy economy. This and other aspects of the invention will become apparent from the detailed description and drawings below.

The main object of the present invention is to provide a simple and efficient system for feeding suspension of cellulosic material to a treatment vessel such as a continuous boiler, and at the same time to provide improved operating and maintenance properties. This and other objects of the invention will become apparent upon reading the detailed description of the invention and of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a typical prior art system for feeding a suspension of distributed cellulosic material to a continuous digester; FIG. 2 shows another prior art system for feeding a suspension of atomized cellulosic material to a continuous digester; FIG. 3 shows a typical embodiment of a system for feeding a suspension of finely divided cellulosic material to a continuous boiler according to the invention; and FIG. 4 shows another embodiment of the invention. DETAILED DESCRIPTION OF THE DRAWINGS Although the systems shown and described in FIG. 1-3 are continuous boiler systems, it is understood that the method and apparatus of the present invention may also be used to feed one or two batch boilers or an impregnation vessel connected to a continuous boiler. The continuous boilers shown and which can be used in connection with the invention are preferably continuous boilers of the KAMYR® type and can be used for kraft (ie sulphate) cooking, sulphite cooking, soda cooking or similar processes. Specific cooking processes and equipment that can be used include the MCC®, EMCC® and Lo-Solids® processes and boilers marketed by Andritz Inc. Strength and yield enhancers such as anthraquinone, polysulde or their equivalents or derivatives may be used. in cooking processes utilizing the present invention.

FIG. 1 shows a typical system 10 according to the prior art for feeding single suspension of distributed cellulosic carrier material, e.g. softwood ice to the upper end of a continuous boiler. The boiler 11 typically contains a liquor extraction strainer 12 at the boiler inlet 13 for removing overflow sludge from the suspension and returning it to the feed system 10. The boiler 11 also contains at least one liquor extraction strainer 14 for draining the effluent during or after the cooking process. The cooker 11 typically contains one or more additional deduction strainers (not shown) which may be connected to a co-discharge circuit, such as a Mcc®, nMcctß-coke coke coil or a Lo-Solids® cooker circulation with a liquefied suction line and entiltrator line for dilution end. Koklut, e.g. kraft white liquor, black liquor or green liquor are added to the edge in these circulations. The boiler 11 also contains an outlet 15 for discharging the chemical mass produced which can be passed on to subsequent treatment such as washing and bleaching.

In the prior art feeder system 10 shown in FIG. 1 Distributed cellulosic fibrous material 20 is imnatant in the ice bin 21. The material 20 typically consists of softwood or hardwood ice, but non-distributed cellulosic fibrous material of other kinds, such as sawdust, grass, straw, bagasse, kenaf or other agricultural waste or a combination thereof. Although the term "ice" in the following description is used to refer to the distributed cellulosic material, it is understood that the term is not limited to wood ice but refers to any form of finely divided cellulosic material listed above or the like.

The chip bin 21 may be a conventional vibrating discharge ice bin or a DIAMONDBACK® base vessel described in U.S. Patent 5,500,083 and sold by Andritz Inc., which does not have a vibrating discharge but an outlet which exhibits one-dimensional convergence and lateral release. The bin 21 contains an air-locking device at its inlet and devices for monitoring and regulating the ice level in the bin and a, small valve with control means for regulating the pressure in the bin. Fresh steam or steam generated by evaporation of effluent (ie relaxation steam) is typically supplied in the bin 21. via one or more of your wires 22.

The bin 21 typically dispenses into a dispenser 23, e.g. a Chip Meter marketed by Andritz, but other types of devices, such as a screw-type dispenser, can also be used. The dispenser 23 dispenses into a pressure relief device 24, such as a Low-Pressure Feeder marketed by Andritz. The pressure relief device 24 separates the pressurized horizontal treatment vessel 25 from the substantially atmospheric pressure prevailing above the device 24.

The vessel 25 is used to treat the material with pressurized steam, e.g. steam with a pressure of about 0.7 - 1.4 bar (10 - 20 psig). The vessel 25 may, like Steaming Vessel, be sold by Andritz, or contain a screw type conveyor. Fresh chipping steam is supplied to the vessel 25 via one or more lines 28.

After treatment in the vessel 25, the material is fed to a high pressure feeder 27, such as a High-Pressure Feeder marketed by Andritz. The base material is typically transferred to the feeder 27 by a conduit or shaft 26, such as a Chip Chute sometimes sold by Andritz. Using a cooking cloth, e.g. a mixture of kraft liquor and white liquor is typically supplied to the shaft 26 via the conduit 29 so that a suspension of material and liquor is formed in the shaft 26.

If the prior art system of FIG. 1 utilizes a DIAMONDBACK® basing vessel described in U.S. Patent 5,000,083, which provides improved basing under atmospheric pressure, the pressure treatment vessel 25 and the pressure separation device 24 may be omitted.

The conventional High-Pressure Feeder 27 has a low pressure inlet connected to the shaft 26, a low pressure outlet connected to the line 30, a high pressure inlet connected to the line 33, a high pressure outlet connected to the line 34 and a rotor provided with fi cokes, driven by an electric motor with speed control and a speed control (not shown). 10 l 2 The low pressure inlet leads the heated ice suspension from the shaft 26 into a pocket in the rotor. A strainer in the feeder 27 outlet 30 holds the ice in the rotor, but allows the liquor in the suspension to flow through the rotor to be removed via the line 30 and the pump 31. As the rotor rotates, the ice retained in the rotor is pre-pressurized from the pump 32 via the line 33. entrains fl the ice from the feeder and carries it to the upper end of the digester 11 via line 34. The near current of fl ice and liquor reaches the inlet of boiler 11 is removed from the suspension viasilen 12 part of the liquor that has been used to transport the ice in line 34. the overflow caps drawn off the strainer 12 are returned to the inlet of the pump 32 via the line 35. The liquor in the line 35, in which fresh cooking liquor can be added, is pressurized in the pump 32 and passed in the line 33 to the feeder 27 to flush the ice out thereof.

The chips held by the strainer 12 move downwards in the digester 11 for further treatment.

The liquor removed from the feeder 27 via line 30 and the pump 31 recirculated to the shaft 26 above the feeder 27 through line 36, sand trap 37, line 38, filter 39 and line 29. Sand trap 37 is a cyclone type separator for removing sand and other particles from the liquor. The filter 39 is a static sieve device which removes overflow end from the conduit 38 and passes the passage 39 'to a level container 40 for storage there. Lye stored in the container 40 is returned to the upper end of the digester via line 41, pump 42 (ie the replacement end pump) and line 43. Fresh cooking liquor can also be added in lines 41 and 43.

FIG. 2 shows another prior art system 110 for feeding ice to a boiler. The system uses processes and equipment described in U.S. Patents 5,476,572, 5,635,025 and 5,622,598. This equipment and processes which are exploited are marketed under the trademark Lo-Levelm by Andritz. The components of FIG. 2 which are identical to those shown in FIG. l has been denoted by the same reference numerals. The components that are similar or perform similar functions to those shown in FIG. 1 has been denoted by the same reference numerals as in FIG. 1 but provided with the prefix "1". 13As in the system of FIG. In, chips 20 are fed into the basing vessel 121 where it is exposed to steam which is inhaled via line 22. The vessel 121 discharges to the dispenser 123 and then to the line 126, which is preferably a Chip Tube marketed by Andritz. Boiling cloth is typically fed into the pipe 126 via line 55, which is similar to line 29i FIG. 1. Since the vessel 121 is preferably a DIAMONDBACK® basing vessel according to U.S. Patent 5,000,083, no pressure separating device 24 or pressurized basing vessel 25 as in FIG. 1 of this prior art system. As shown in U.S. Patent 5,476,572, a high pressure suspension pump 51 fed by line 50 is used to transport the ice to the feeder 27 via line 52, instead of discharging the chip and liquor suspension directly to the feeder 27. The chips are fed. the via pump 51 to the digester 11 by means of the feeder 27 in a manner similar to that described and shown in connection with FIG. 1.

The system of FIG. 2, in addition to the pump 51, the pump 31 in FIG. 1 to supply the suspension to the feeder 27. The pump 51 provides the driving force needed to supply the liquor through the feeder 27, the line 30, the sand separator 37, the filter 39 and the line 129 to the level container 53 for the liquor.

The function of the level container 53 is described in U.S. Patent 5,622,598. The container 53 ensures a sufficient supply of lye to the inlet of the pump 51, via line 54. The container can also supply lye to the pipe 126 via line 55. The lye container 53 also made it possible for the operator to change the lye level in the feed system so that the lye level, if desired, can be raised to the dose 123 of the dispenser 123 or even to the level of the bin 121.

This possibility is also described in U.S. Patent 5,635,025.

FIG. 3 shows a preferred embodiment of a feed system 210 according to the present invention which further simplifies those in FIG. 1 and 2, the feed systems showed prior art. In the preferred embodiment shown in FIG. 3 shows the high pressure feeder, component 27 of FIG. 1 and 2, eliminated. Instead of being fed to the feeder 27 by gravity in the shaft 26 of FIG. 1 or via the pump 52 in FIG. 2, at least two high pressure suspension pumps 251, 251 'are used to transport suspension to the inlet of the boiler 11. The components of FIG. 3 which are substantially identical to those shown in FIG. 1 and 2 have been denoted by the same reference numerals. The components that are similar or perform similar functions to those shown in FIG. loch 2 has been denoted by the same reference numerals as in FIG. 1 and 2 but bearing the prefix "2".

As in the process of FIG. 1 and 2, the ice 20 of the present invention is fed into the basing vessel 221. The chips are preferably fed by a sealed horizontal conveyor as shown in U.S. Patent 5,766,418. The basing vessel 221 is preferably a DIAMONDBACK® basing vessel according to U.S. Patent 5,000,083, or supplied to joints. 22. The base vessel 221 is typically provided with conventional monitoring and control devices as well as an entry pressure relief valve (not shown). The vessel 221 dispenses base ice to the dispenser 223 which, as described above, may be a rotor-type device with pockets, such as a chip meter, or a screw-type device.

In an embodiment of the invention, the dispenser 223 discharges directly to the line or shaft 226. In an alternative embodiment, a pressure separating device, such as a rotor-type separating device with corners, shown by dotted lines at 224, e.g. a conventional Low-Pressure Feeder, be arranged between the dispenser 223226. the shaft 226 the pressure separating device 224 is substantially atmospheric, the pressure in the shaft and the shaft Although the pressure in even without 226 with a pressure separating device 224 can be between 0.07 - 3.5 bar (1 and 50psig), but is preferably 0.3 - 1.7 bar (5 - 25 psig) and most preferably 0.7 - 1.4 bar (10 - 20 psig). Boiling cloth is added as described above in the shaft 226 (see line 226 'in FIG. 3) so that a suspension of ice and lye is formed in the shaft 226 with a detectable level (not shown). The suspension in the shaft 226 is discharged via a curved outlet 250 to the inlet of the pump 251. The feed of suspension into the inlet of pump 251 is typically increased by a lye flow from the container 253 via line 254 as described in U.S. Patent 5,622,598.

The pump 251 is a centrifugal type high pressure suspension pump with a coil screw, such as a "Hydrostal" pump from Wemco, Salt Lake City, Utah. The pump may alternatively be a suspension pump from Lawrence Company. The pressure at the inlet of the pump 251 can vary from atmospheric pressure to 3.5 bar (50 psig) depending on whether or not a pressure separating device 224 is used.

In the preferred embodiment shown in FIG. 3, the pump 251 discharges the inlet of the pump 251 '. The pump 251 'is preferably of the same type as the pump 251 with the same or a higher pressure value. If two pumps are used, the pressure as the outlet of the pump 251 'is typically 10 - 27.5 bar (150 - 400 psig) (ie 105 - 280 meters or 345 - 920 feet of water column) but preferably about 14 - 21 bar (200 - 300 psig ) (140 - 210 meters or 460 - 690 feet). If necessary, the amount of lye in the suspension can be increased with lye from the container 253 via the line 56 and the liquid pump57. Although the embodiments shown in FIG. 3 contains two pumps, alternatively single or three or three pumps in series or in parallel can be used. In that case, the outlet pressure from this one pump or from the last pump is preferably the same as the outlet pressure from the pump 251 'above.

The pressurized, typically heated, suspension is discharged from pump 251 'to line 234. Line 234 for suspension to the continuous boiler 11 inlet. Overflow end in the suspension is drained via the screen 12 in a conventional manner. The overflow liquid is returned to the feed system 210 via the conduit 235, preferably the closure container 253 to be used for suspension in the conduit 250 via the conduit 254. The liquor in the line 235 can be passed through a sand separator 237 if desired. This sand separator can be designed for pressurized or depressurized operation depending on the desired mode of operation.

Unlike the prior art systems, which utilize a High-Pressure Feeder (27 in FIGS. 1 and 2) that uses the pressure of the liquor returned to the vial line 35 as an essential part of the method of passing the ice from the High-PressureFeeder to the digester 11. liquid-borne, it is not essential to the present invention that the pressurized recirculation liquid 235 be returned to the inlet of the pumps 251, 251 '. The pressure energy in the i in line 235 can be used anywhere in the factory where it is needed. In a preferred embodiment, however, the present invention utilizes the pressure in line 235 to minimize the energy requirements of pumps 251 and 251 'as far as possible.

How the pressure in the return line 235, typically about 10 - 27.5 bar (150 - 400 psig), is used depends on how the supply system 210 works. If the vessel 226 operates pressurelessly - at substantially atmospheric pressure - the pressurized liquor returned to line 235 must be returned to a substantially atmospheric pressure before being fed line 250. One way to do this is to use a pressure control valve 58 and entry pressure gauge 59 in line 235. The opening in the valve 58 is regulated so that a predetermined pressure prevails in the line 235 downstream of the valve 58. The lye container 253 must also be designed so that it functions as a relaxation vessel so that the hot pressurized lye in the line 235 is quickly evaporated to form a single source in the vessel 253. The steam can .a. used in the vessel 221 via line 60. In a preferred embodiment, however, the pressurized liquor in line 235 is used to increase the flow from the pump 251 ', e.g. via line 61 and pump 62. The pressure line 235 can also be used to increase the flow between pumps 251 and 251 'line 252 via line 63, with or without pump 64 (a non-return valve can in some cases be used instead of pumps 62, 64 or in addition ). By reusing some of the pressure in the line 235, the energy requirements of the pumps 251 and 251 'can be reduced.

The heat of the liquor in the line 235 can also be brought into heat exchange contact with one or more other liquids in the pulp mill which need to be aggravated.

The pumps 251, 251 'can be used together with a jet pump to increase the pressure in the inlet or outlet of the pumps. A jet pump can also be used as a means of pre-feeding liquid into the ice. A jet pump can e.g. be arranged in the outlet of or below the vessel 226 and liquid is first fed into the ice by means of this jet pump. The jet pump may comprise an opening of venturity type in one or two of the lines 250, 252 and 234 in which a pressurized liquid stream is fed. The pressurized liquid cone is obtained from any available source, but is preferably taken from the discharge 235 upstream of the valve 58. An exemplary jet pump is shown schematically at 70 in FIG. 3. 10 17One of the High-Pressure Feeder 27 tasks in FIG. 1 and 2 is to function as a shut-off valve to prevent the pressure from disappearing into the equipment and the transport lines, e.g. wires 34 and 35 in FIG. l, if any of the drain components should malfunction or strike. In the feed system according to the present invention, there is the alternative means of preventing loss of pressure due to errors or malfunctions. FIG. 3 shows e.g. a one-way (check) valve 65 line 234 to prevent a pressurized flow from flowing back to the pump 251 or 251 '. Conventional automatic (eg, solenoid-controlled) shut-off valves 66 and 67 are further provided in respective lines 234 and 235 to separate pressurized lines 234, 235 from the rest of the supply system 210. In a preferred function alternative, a conventional pressure switch 68 is provided downstream of the re-pump 251 '. The function of the switch 68 is to monitor the pressure line 234 so that the conventional control means 69 automatically isolates the digester 11 from the supply system 210 by closing the valves 66 and 67 if the pressure deviates from a predetermined value. The valves may also be arranged to close automatically when a direction detector detects a reversal of the direction of direction in line 234. Although the pressure relief prevention devices described above are preferred, other arrangements of valves, detectors, indicators, alarms or the like may be used to prevent significant lowering. the pressure in the digester 11. Although the system 210 is preferably used in conjunction with a continuous digester 11, it may also be used in conjunction with other vertical treatment vessels of greater than atmospheric pressure (typically a pressure of at least about 10 bar overpressure) with an upper inlet, such as an impregnation vessel or a rate cooker.

FIG. 4 shows a further embodiment of the invention where the ice transport concept has been extended from the feed system for a boiler to feed from a pulp mill. FIG. 4 shows a system 510 for feeding distributed cellulosic material to a pulp manufacturing process. The system consists of a subsystem 410 for feeding fl ice from the wood yard into the system 510 and a subsystem 310 for processing 18 and feeding fl ice to the digester ll. The subsystem 310 is substantially identical to the system 210 shown in FIG. 3.

The components of FIG. 4 which are substantially identical to those shown in FIG. 1 - 3 have been denoted by the same reference numerals. The components that are similar or perform similar functions to those shown in FIG. 1-3 have been denoted by the same reference numerals as in FIG. 1 but provided with pre fi xct "3".

The wood yard in conventional pulp mills can be supplied with wood of different shapes as described above. Wood or other cellulosic material is typically converted to ice and stored in open ice piles or ice storage silos. In FIG. 4 shows an fl ice storage consisting of an fl ice pile 80. In a preferred embodiment, the hög ice is transported from the pile80 or some other storage by conventional means, e.g. a conveyor or single-front loader (not shown) and fed into the vessel 81. This vessel may be a DIAMONDBACK® vessel or a conventional storage vessel. The vessel 81 can operate at a higher than atmospheric pressure, e.g. 0.1 - 5 bar. If the vessel operates at a higher than atmospheric pressure, a pressure separating device (not shown) of some kind may be provided at the inlet of the vessel to prevent relief of the pressure. The device may be a star-type separating device, such as a Low-Pressure Feeder or Air-Lock Feeder marketed by Andritz or a screw-type screw-type feeder as described in U.S. Patent 5,766,418.

Liquid, e.g. sheep water, steam, liquid containing cooking chemicals, is fed into the vessel 81 via one or fl your lines 82 to form a suspension of liquid and fl ice and provide a detectable liquid level in the vessel 81. Devices for monitoring and regulating the liquid level and fl ice level in the vessel 81 may be provided. The liquid can be constituted by a heated liquid, e.g. hot water or steam with a temperature of 50 -100 ° C. If vessel 81 is a pressurized vessel, liquid temperatures of over 100 ° can be used. The liquid preferably but not necessarily contains at least some active cooking chemical, e.g. sodium hydroxide (NaOH), sodium sulfate (NagS), polysulfide, anthraquinone or its equivalents or derivatives. 19 From the vessel 81, the suspension flows out to the inlet of the suspension pump 85 via the line 84. The outflow from the vessel 81 can be made more efficient by means of a dispensing device 83. The suspension flow in the line 84 can also be made more efficient by supplying liquid via the line 82 '. The pump 85 can be a single-suspension pump of the type described above. for example a Wemco or Lawrence pump or the like or a suspension conveyor of another type. Although only one pump 85 is shown, more than one pump or similar device may be used to transport the suspension via line 86 to vessel 321. The suspension transport via line 86 may contain one or more storage or equalization containers (not shown). The one or more pumps 85 contain at least one device with degassing capacity so that undesired air or gas can be removed from the suspension. The pressure in line 86 depends on the number of pumps and other transport devices used and how high and how far the suspension is to be transported. The pressure in line 86 can range from about 0.3 to over 35 bar (about 5 to over 500 psig).

During transport, the ice can also be subjected to a treatment of some kind, eg deaeration or impregnation with a bag, preferably a liquid containing chemicals such as those described above. The suspension can also be subjected to at least one pressure variation during transport, such as the pressure changing from a first pressure to a second, higher pressure and then to a third pressure which is lower than the first pressure. As described in U.S. Patents 4,057,461 and 4,743,338, the pressure variation variation in a suspension of och ice and the impregnation of the fl ice with this liquor improves. The pressure pulsations can be achieved by varying the outlet pressure in a series of transport devices or by controlled pressure relief in the suspension between the pumps.

The suspension in line 86 is fed into the inlet of vessel 321. Even if the vessel shown is a treatment vessel, ie. a basing vessel, it can also be a storage vessel, an impregnation vessel or even a digester. Since the transport in the line 86 typically requires overflow liquid at least to some extent, which does not require the undertreatment or storage, a dilution device of some kind must be arranged between the transport device and the treatment vessel. A preferred dewatering device is a Top Separator marketed by Andritz. This TopSeparator can be of standard type or a "reverse" Top Separator. The device may be an external separate unit or one mounted directly on the treatment vessel as shown. The liquid removed from the suspension by means of the dewatering device 87 is returned to the vessel 81 or to the inlet of the pump or pumps 85 via the line 88 to serve as a suspension liquid for the ice. The liquid removed via the device 87 can also be used elsewhere where it is needed in the pulp mill. The liquid in line 88 can be heated or cooled as desired in a heat exchanger 90 and can be pressurized by using one or more conventional centrifugal type liquid pumps 89. The liquid in line 88 can be fed into the vessel 81 via line 82 and into line 84 via line 82 '.

The treatment vessel 321 shown is a basing vessel similar to the vessel 221 shown in FIG. 3, e.g. a DIAMONDBACK® base vessel. The feed system 310 is otherwise similar to the system 210 in FIG. 3. The chip feeding system 410 feeds, for example, the feeding system 310 which feeds the digester ll. Note that subsystem 310 of FIG. 4 is a subsystem of the total system which feeds fl ice from fl ice pile 80 to the digester 11.

The system may include one or more subsystems 310 for feeding to the digester 11.

The invention relates to its widest extent to transport and treatment in your stages of distributed cellulosic carrier material with economic recovery and reuse of energy, e.g. friend energy. Although the invention has been described above in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the embodiments described above and shown in the drawing, but may be modified within the scope of the appended claims.