SE530999C2 - Process for treating finely divided fiber material when boiling pulp - Google Patents

Abstract

A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps the pressure in the return line may be reduced utilizing a pressure reduction valve and/or a flash tank. During pressurized transferring of the slurry from the pumps to a treatment vessel (which may be as little about 10 feet or as much as about a half a mile away) treatment liquid is provided which contains at least some active pumping chemical including sodium hydroxide, sodium sulfide; polysulfide, anthraquinone or their equivalents or derivatives; surfactants, enzymes, or chelants; or combinations thereof. Pseudo-countercurrent circulation of treatment liquids may be provided between stations.

Description

53U 999 technology was used for this purpose a so-called High-Pressure Feeder. This feeder is a purpose-built device containing a rotor provided with fi ckor which serves as a means of transferring a material suspension from a low pressure to a high pressure and at the same time acts as a valve which prevents loss of pressure. This complicated and expensive device has long been considered a necessary component for feeding suspensions of distributed cellulosic material into pressurized vessels, typically at an elevated temperature, especially in continuous boilers.

A system that replaces High-Pressure Feeder - which for over forty years has been considered necessary for continuous cooking - greatly simplifies the construction of a pulp mill.

According to one aspect, such 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 a suspension of distributed cellulosic support material in its upper part and an outlet in its lower part, and a pressure generating feeder for pressurizing a suspension of material from the basing vessel and transferring it to the inlet of the treatment vessel, which pressure generating food consists of one or fl your high-pressure suspension pumps located below the upper part of the treatment vessel.

The one or more pumps preferably comprise a first and a second high-pressure suspension pump arranged in series, each having a pressure value, an inlet and an outlet, the inlet of the first pump being in operative connection with the basing vessel, the outlet of the first pump being operatively connected to the the second pump inlet and the second pump have a higher pressure value than the first pump. The suspension pumps can be spiral screw-type centrifugal pumps, double-piston-type sludge pumps or other similar conventional pumping devices capable of pressurizing a suspension with a relatively high solids content (in one or more steps) to a pressure of at least about 5 bar overpressure. The pressurization and transport can also be effected by means of one or fl your jet pumps which are driven by the supply of a pressurized fl uid, supplied e.g. by means of a conventional centrifugal powder. 10 l5 20 25 30 5313 999 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 amount of liquid and the amount of pulp 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 pumps as above, the liquid / solids ratio of the suspension being pumped is typically 2-10, preferably 3-7 and most preferably 3-6. The suspension pumps transport suspensions with a much higher solids content 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 (preferably a continuous boiler). The return line can be operatively connected to 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 the pressure of the liquid 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 relaxation vessel and / or a pressure regulating valve in the return line or other conventional construction for reducing the pressure in a line without adversely affecting the liquid. When a relaxation vessel is used, it is connected to the inlet of the first liquid outlet from the relaxation vessel the suspension pump and the steam generated in the relaxation vessel can be used in the basing vessel.

Alternatively, the pressure reduction can be achieved or even avoided by using a jet pump (ejector) which uses the pressurized return line as its source of pressurized liquid. A jet pump may be used in conjunction with one or more of the suspension pumps or other means 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 at least one suspension pump. at least 30 feet (about 10 meters) below the upper end of the cooker and typically more than about 50 feet (about 15 meters) below.

When the high pressure feeder device is left out, it is desirable to use other devices to maintain one of the functions of the high pressure feeder, namely to prevent operating conditions, the high pressure feeder device would typically prevent backflow of liquid from pressure relief in the event of an abnormality. the boiler to the feed system. The device which prevents pressure relief is preferably separated from the 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 pressure relief devices may include an automatic separation valve in the suspension lines which directs suspension from the pumps to the end and the return line from the upper treatment vessel of the treatment vessel, a conventional control means being connected to the separation valves which control them by the pressure sensed by a detector connected to the suspension line. feeding suspension to the upper end of the treatment vessel. 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.

The system may also include means for increasing the flow of liquid to the inlet of the second suspension pump or to another pump or feeder, such as a liquid line containing liquid having a lower pressure than the inlet of the second suspension pump, a line between the liquid line and the inlet and a liquid pump in the line . The liquid line may consist of the return line from the treatment vessel and the line may be directly connected to the return line. 10 IS 20 25 30 ESC! 955 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 wood ice to the upper end of a treatment vessel may comprise the following steps: (a) The wood ice is based to remove heat from it and heat the material. (b) The wood fl ice is suspended in a cooking liquor to effect a suspension of liquid and material. (c) The suspension is pressurized to a pressure of at least 5 bar overpressure at least 30 feet below the upper end of the treatment vessel, the pressurizing step mainly consisting of the upper end of the treatment vessel being transferred to the suspension being pressurized by one or more high pressure suspension pumps. And (d) the wood fl ice is treated during the execution of the transport step (c) with polysul fi d, anthraquinone or their equivalents or derivatives, surfactants, enzymes, chelating agents or combinations thereof.

When the treatment vessel is located upstream of a continuous or batch boiler, step (c) is typically performed downstream of the treatment vessel. There may be a further step (e) before the continuous or batch boiler and substantially immediately after steps (a) and (b), the suspension being pressurized at least 30 feet below the upper end of the boiler and the pressurized wood fl ice being passed to the upper end of the boiler, the pressurizing step consists of the suspension being affected by one or more of your high-pressure suspension pumps. There may also be a step where liquid removed from the digester is returned to the treatment vessel, and the temperature of the liquid is adjusted while the liquid is returned to the treatment vessel. The step of removing liquid from the treatment vessel is typically performed at the upper end of the treatment vessel.

The method may also include an additional step of returning liquid from a location downstream of the treatment vessel to the treatment vessel, and adjusting the temperature of the liquid, and the step of adjusting the temperature of the liquid may be performed by causing the liquid to flow through an indirect heat exchanger. The process may also include a further step in which liquid separated from the suspension at the upper end of the digester is returned to the one or two suspension pumps, the suspension is pressurized to feed it to the digester, and the temperature of the removed liquid is adjusted during recirculation. 10 15 20 25 30 530 999 The above condition not only reduces the size of the system for transporting non-distributed cellulosic fibrous material and its costs. If the comminuted 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 are apparent from the detailed description and drawings below.

According to one aspect of the present invention, there is provided a method of pretreating finely divided cellulosic fibrous material in boiling pulp by using at least a first and a second series-connected pump and at least a first and a second series-connected station, i.e. treatment vessels, with a solid separator and liquid in each. The process comprises the following steps: (a) A suspension of distributed cellulosic fibrous material is pumped using the series-connected pumps. (b) Liquid is separated and removed from the suspension at each station to substantially separate lye circulations and flows and to recirculate removed liquid from at least one of the stations to a location upstream of one of the pumps. (c) Chemicals are added to the suspension upstream of each pump, the chemicals being at least one chemical selected from a group consisting essentially of sodium hydroxide, sodium sulfate; polysul fi d, anthraquinone or their equivalents or derivatives; surfactants, enzymes or chelating agents; or combinations thereof; so that the material is pretreated while being transported from each pump to each station. And (d) liquid removed from the second station is circulated to a location upstream of the first pump.

There may be an additional step where the suspension is degassed at at least one of the stations. There may be a first, second and third series-connected pump and station. And there may also be additional steps where: (e) Liquid removed from the third station is circulated to a location upstream of the second pump. There may also be an additional step in which the removed liquid, while performing at least one of steps (d) and (e), is passed through a heat exchanger to change its temperature by at least about 5 ° C. Step 15 (c) may be performed by adding another chemical or combination of chemicals upstream of each pump so that a substantially different treatment of the material in the suspension takes place during the transport of the suspension from each pump to its associated station. Step (a) can be performed to pressurize the suspension to a pressure of at least 5 bar.

There may also be an additional step in which liquid is removed from at least one of the stations by means of a jet pump (ejector) instead of a shut-off vessel and / or a control valve.

According to another aspect of the present invention there is provided a method of treating distributed cellulosic carrier material comprising the steps of: (a) A suspension of distributed cellulosic fibrous material being pumped using at least a first, second and third series connected pump and respective station, i.e. treatment vessel. (b) Liquid is separated from the suspension at each station to substantially separate lye circulations and flows and to recirculate removed liquid from at least one of the stations to a location upstream of one of the pumps. (c) Chemicals are added to the suspension upstream of at least one of the pumps so that the material is pretreated while being carried by this pump to its associated station. (d) Liquid removed from the third station is circulated to a location upstream of the second pump. And (e) liquid removed from the second station is circulated to a location upstream of the first pump, the third station being a boiler. The steps or additional steps can be performed as described above.

The main object of the present invention is to provide simple and efficient treatment and feeding of a suspension of cellulosic material to a treatment vessel and at the same time achieve improved maneuverability and easier maintenance.

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; 10 15 20 25 30 5310 959 FIG. 2 shows another prior art system for feeding a suspension of distributed cellulosic material to a continuous digester; FIG. 3 and 4 show typical embodiments of a system for feeding a suspension of distributed cellulosic material to a continuous boiler using Pumps; FIG. 5 shows another embodiment of a system utilizing pumps; and FIG. 6 schematically shows a preferred system which can be used to carry out the method according to 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 they can also be used to feed one or fl your batch boilers or an impregnation vessel connected to a continuous boiler. The continuous boilers shown and which can be used are preferably continuous boilers of the KAMYR® type and can be used for power (ie sulphate) cooking, salt cooking, soda cooking or similar processes. Specific cooking methods and equipment that may be utilized include the MCC®, EMCC® and Lo-Solids® processes and cookers marketed by Andritz Inc. Strength and yield enhancers such as anthraquinone, polysulde or their equivalents or derivatives may be used in the cooking procedures. .

FIG. 1 shows a typical system 10 according to the prior art for feeding a suspension of a distributed cellulosic carrier material, Lex. softwood ice to the upper end of a continuous boiler. The boiler 11 typically contains a sloping strainer 12 at the boiler inlet 13 for subtracting the overflow end from the suspension and returning it to the feed system 10.

The boiler 11 also contains at least one lye extraction screen 14 for drawing off liquor during or after the cooking process. The boiler ll typically contains one or ytterligare additional suction screens (not shown) which may be connected to boiler circulation, such as an MCC®, 10 15 20 25 30 5GB 959 EMCC® boiler boiler circulation or a Lo-Solids® boiler circulation with a liquor extraction line and a supply line for dilution end. Koklut. for example kraft white liquor, black liquor or green liquor can be added 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 carrier material 20 is fed into the ice bin 21. The material 20 typically consists of softwood or hardwood ice, but distributed cellulosic carrier material of other types, such as sawdust, grass, straw, bagasse, kenaf or other agricultural waste or a combination of other types of agricultural waste. . Although the term "ice" in the following description is used to refer to the disintegrated cellulosic carrier material, it is understood that the term is not limited to wood ice but refers to any form of disassembled cellulosic material listed above or the like.

The chip bin 21 may be a conventional vibrating discharge ice bin or a DIAMONDBACKE basing vessel described in U.S. Patent 5,500,083 and marketed by Andritz Inc., which does not have a vibrating discharge but an outlet exhibiting 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 to the bin 21 via one or more of the conduits 22.

The bin 21 typically dispenses into a dispenser 23, e.g. a Chip Meter marketed by Andritz Inc, but other 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 Inc. 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, such as the Steaming Vessel marketed by Andritz Inc, contain a screw type conveyor. Fresh or relaxation steam is supplied to the vessel 25 via one or more of its 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 Inc. The base material is typically transferred to the feeder 27 by a conduit or shaft 26, such as a Chip Chute marketed by Andritz Inc. Heated 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 as described in U.S. Patent 5,000,083, which provides improved atmospheric basing under pressure, the pressure treatment vessel 25 and the pressure separation device 24 may be dispensed.

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 a shaft, which is driven by an electric motor with speed control and a gear (not shown).

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 line 30 and pump 31. As the rotor rotates, the ice retained in the rotor is subjected to high pressure termination from pump 32 via line 33. This high pressure shutter entrains the ice from the feeder and carries it to the upper end of the digester 11 via line 34. When the flow of ice and liquor reaches the inlet of the digester 11, some of the liquor used to transport the ice is removed from the suspension via the strainer 12. in the line 34. The overflow closure drawn off via the strainer 12 is 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. . The chips held by the strainer 12 move downwards in the digester 11 for further treatment. The liquor removed from the feeder 27 via the line 30 and the pump 31 is recycled to the shaft 26 above the feeder 27 through the line 36, the sand separator 37, the line 38, the filter 39 and the line 29. The sand separator 37 is a cyclone type separator for removing sand and other particles from the lye. The filter 39 is a static screen device which removes overflow end from line 38 and passes it through line 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 digester.

The system uses processes and equipment described in U.S. Patents 5,476,572, 5,622,598 and 5,635. This equipment and the processes they utilize are marketed collectively under the Lo-Levelm brand by Andritz Inc. The components of FIG. 2 which are identical to those shown in FIG. 1 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. l but provided with the preñxet H1 ".

As in the system of FIG. 1, ice is fed into the basing vessel 121 where it is exposed to steam which is fed via the line 22. The vessel 121 discharges to the dispenser 123 and then to the line 126, which preferably consists of a Chip Tube marketed by Andritz Inc.

Boiling cloth is typically fed into the pipe 126 via line 55, which is similar to line 29 in FIG. 1.

Since the vessel 121 is preferably a DlAMONDßACKüa basin vessel according to US patent 5,000,083, no pressure separating device 24 or pressurized basin 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 S0 is used to transport the ice to the feeder 27 via line 52, instead of discharging the suspension of ice and lye directly to the feeder 27. The pump 51 is preferably a Hydro-steel. pump from Wemco or a similar pump from Lawrence Company. The chips are fed via the 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. The system of FIG. 2, in addition to the pump 51, the pump 31 in FIG. 1 to bring the suspension to the feeder 27. The pump 51 provides the driving force needed to pass 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 operation of the level container 53 is described in U.S. Patent 5,622,598. The container 53 ensures a sufficient supply of liquor to the inlet of the pump 51, via line 54. The container can also supply liquor to the pipe 126 via line 55. The liquor container 53 also enables the operator to change the liquor level in the feed system so that the liquor level, if desired, can be raised to the doser 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 which further simplifies those of FIG. 1 and 2 show the feed systems according to the prior art. In the preferred embodiment shown in FIG. 3 has the high pressure feeder, component 27 of FIG. 1 and 2, eliminated. Instead of feeding fl ice to the feeder 27 by means of gravity in the shaft 26 in FIG. 1 or via the pump 52 in FIG. 2, at least one, preferably 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. 1 and 2 have been denoted by the same reference numerals as in FIG. 1 and 2 but provided with the prefix "2".

As in the process of FIG. 1 and 2, the ice 20 is fed into the basing vessel 221. The chips are preferably fed by means of a sealed horizontal conveyor as shown in U.S. Patent 5,766,418. The base vessel 221 is preferably a DIAMONDBACKQ1 base vessel according to U.S. Patent 5,000,083, which is supplied with steam via one or more lines 22.

The base vessel 221 is typically provided with conventional monitoring and control devices as well as a 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. 10 15 20 25 30 5312! 999 In one embodiment, the dispenser 223 dispenses directly to the conduit or shaft 226. In an alternative embodiment, a pressure separation device, such as a rotor type separation device, having pockets shown in dotted lines at 224, e.g. a conventional Low-Pressure Feeder, be arranged between the dispenser 223 and the shaft 226. Although the pressure in the shaft 226 even without the pressure separating device 224 is substantially atmospheric, the pressure in the shaft 226 with a pressure separating device 224 may be between 0.007 - 3.5 bar (1 and 50 psig), 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 preferably a spiral screw centrifugal type high pressure suspension pump, such as a "Hydrostal" pump from Wemco, Salt Lake City, Utah. The pump may alternatively be a suspension pump from Lawrence Company, Lawrence, Massachusetts. The pressure at the inlet of the pump 251 can vary from atmospheric pressure to 50 psig depending on whether or not a pressure separating device 224 is used. In the preferred embodiment shown in FIG. 3 discharges the pump 251 to 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 generated in the outlet of the pump 251 'is typically 150 - 400 psig (ie 345 - 920 feet of water column) but preferably about 200 - 300 psig (460 - 690 feet). If necessary, the amount of lye in the suspension can be increased with lye from the container 253 via line 56 and the liquid pump 57. Although the embodiments shown in FIG. 3 contains two pumps, alternatively a single or three or two 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 the pump 251 'to line 234. Line 234 for the suspension to the inlet of the continuous boiler 11. 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 line 235, preferably to the liquor container 253 to be used for suspension in line 250 via line 254. The liquor in line 235 can be passed through a sand separator 237 if desired. This sand separator can be designed for pressurized or pressureless operation depending on the desired mode of operation.

Unlike the prior art systems which use a High-Pressure Feeder (27 in FIGS. 1 and 2) which uses the pressure of the liquor returned via the line 35 as an essential part of the method of passing the ice from the High-Pressure Feeder to the digester. In the fluid-borne manner, it is not essential for the pump design that the pressurized recirculation fluid 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 pressure in line 235 is utilized to minimize the energy requirements of pumps 251 and 251 'as far as possible.

How the pressure in the return line 235, typically about 150-400 psig, is utilized depends on how the supply system 210 operates. If the vessel 226 operates without pressure - at substantially atmospheric pressure - the pressurized liquor returned in line 235 must be returned to a substantially atmospheric pressure before being fed into line 250. One way to do this is to use a pressure control valve 58 and a pressure gauge 59 in the line 235. The opening in the valve 58 is controlled so that a predetermined pressure prevails in the conduit 235 downstream of the valve 58. In addition, the liquor container 253 must be designed so as to act as a relaxation vessel so that the hot pressurized liquor in the conduit 235 is rapidly evaporated to form a steam source. in the vessel 253. The steam can e.g. be 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 in line 235 can also be used to increase the flow between the pumps 251 and 251 'in line 252 via line 63, with or without pump 64 (in some cases a non-return valve can be used instead of pumps 62). , 64 or more). 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 diluted.

The pressure generation and transport function of the pumps 251 and 251 'can instead be achieved by means of a conventional jet pump, e.g. a jet pump from Fox Valve Development Corporation. Alternatively, the pumps 251, 251 'may be used in conjunction 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 feeding liquid into the ice. A jet pump can e.g. be arranged in the outlet of or under the vessel 226 and liquid is first fed into the ice by means of this jet pump. The jet pump may include a venturi type opening in one or more of the conduits 250, 252 and 234 into which a pressurized liquid stream is fed. The pressurized liquid can be obtained from any available source, but is preferably taken from line 235 upstream of valve 58. An exemplary jet pump is shown schematically at 70 in FIG. 3.

The pumps 251 and 251 'need not be centrifugal pumps but may consist of any other type of suspension feed device which can provide direct pressurization and transfer of a suspension of ice and liquor from the outlet of the vessel 226 to the inlet of the boiler 11. A sludge pump that is typically used in the mining industry can e.g. used, for example, a double-piston type sludge pump such as the KOS pump marketed by Putzmeister or some similar conventional pumping device.

One of the High-Pressure Feeder 27 tasks in FIG. 1 and 2 is to act as a shut-off valve to prevent the pressure from disappearing in the equipment and FIG. l, the feed components would malfunction or strike. In the feed system with pumps there are the transport lines, e.g. lines 34 and 35 in if any of the alternative means of preventing loss of pressure due to faults or malfunctions occurred. FIG. 3 shows e.g. a one-way (check) valve 65 in line 234 to prevent a pressurized flow from flowing back to pump 251 or 251 '. Conventional automatic (eg, solenoid-controlled) isolating valves 66 and 67 are further provided in respective conduits 234 and 235 to separate the pressurized conduits 234, 235 from the rest of the supply system 210. In a preferred operating alternative, a conventional pressure switch is 68 is arranged downstream of the pump 251 'in the line 234. The function of the switch 68 is to monitor the pressure in the 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 flow direction in the line 234. Although the above-described devices 65 - 69 for preventing pressure relief are preferred, other arrangements of valves, detectors, indicators, alarms or the like may be used if they can sufficiently prevent significant lowering of the pressure in the boiler 1 1. Although the system 210 is preferably used together with a continuous boiler 11, it can also be used together with other vertical treatment vessels with a higher than atmospheric pressure (typically a pressure of at least about 10 bar overpressure ) with an upper inlet, such as an impregnation vessel or a batch boiler.

FIG. 4 shows a further embodiment where the ice transport concept with pumps has been extended from the feed system for a boiler to feed from a pulp mill's wood yard.

FIG. 4 shows a system 510 for feeding finely divided cellulosic material into a pulping process. The system consists of a subsystem 410 for feeding chips from the wood yard into the system 510 and a subsystem 310 for processing and feeding chips to the digester 11. 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. I - 3 has been denoted by the same reference numerals as in FIG. 1 but provided with the prefix "3". The wood yard in conventional pulp mills can be supplied with wood of various shapes as described above. Wood or other cellulosic ñber material is typically converted to fl ice and stored in open fl ice piles or fl ice storage silos. In FIG. 4 shows an ice storage consisting of an ice pile 80. In a preferred embodiment, the ice is transported from the pile 80 or some other storage by conventional means, e.g. a conveyor or a 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 separator, such as a Low-Pressure Feeder or Air-Lock Feeder marketed by Andritz Inc. or a screw-type screw-type feeder as described in U.S. Patent 5,766,418.

Liquid, e.g. fresh water, steam, liquid containing cooking chemicals are fed into the vessel 81 via one or more lines 82 to form a suspension of liquid and ice and to provide a detectable liquid level in the vessel 81. Devices for monitoring and regulating the liquid level and the ice level in the vessel 81 may be provided. . The liquid may consist of a heated liquid, e.g. hot water or steam with a temperature of 50 - 10 ° C. If vessel 81 is a pressurized vessel, liquid temperatures above 100 ° C can be used. The liquid preferably but not necessarily contains at least some active cooking chemical, e.g. sodium hydroxide (NaOH), sodium sulfide (NazS), polysulfide, anthraquinone or their equivalents or derivatives or surfactants, enzymes or chelating agents; or combinations thereof.

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 effected by means of a discharge device ss (obviously not necessary if an oiAMoNoßAciå outlet is used).

The suspension fate in line 84 can also be made more efficient by supplying liquid via line 82 '. The line 82 'may be the only means for supplying liquid so that a liquid level is present in the line 84 and not in the vessel 81. The pump 85 may consist of a 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 a single pump 85 is shown, any 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 function so that undesired air or gas can be removed from the suspension.

The suspension discharged from the pump 85 is passed via line 86 to subsystem 810.

The subsystem 810 may be located adjacent to the subsystem 710, e.g. at a distance of about 10 meters (about 30 feet) from the subsystem 710, or at a significant distance from the subsystem 710, e.g. about 800 m (half a mile) or more, depending on the layout of the pulp mill. Line 86 is therefore drawn in part by dashed lines to indicate an unspecified distance between subsystems 710 and 810.

The pressure in line 86 depends on the number of pipes 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 5 psig to over 500 psig.

During transport, the ice can also be subjected to a treatment of some kind, e.g. 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 second pressure. As described in U.S. Patents 4,057,461 and 4,743,338, the pressure variation in a chip and lye suspension improves the impregnation of the ice with this lye. 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 boiler. Since the transport in the conduit 86 typically requires overflow liquid at least to some extent, which is not needed during the treatment or storage, a dewatering device of some kind may be arranged between the transport device and the treatment vessel. A preferred dewatering device is a Top Separator marketed by Andritz Inc. This Top Separator may be of the 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 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 e.g. the feed system 310 which feeds the digester ll. Note that subsystem 310 of FIG. 4 is a subsystem of the overall system that feeds fl ice from fl ice pile 80 to the digester 11. The system may include one or fl your subsystem 310 for feeding to the digester 11.

FIG. 5 shows a system 610, which is an extension of the system 510 shown in FIG. 4.

System 610 is a combination of three subsystems 710, 810 and 910. Subsystem 710 is similar to system 410 in FIG. 4. Components that are substantially similar to those found in FIG. 1 - 4 have been denoted by the same reference numerals.

Wood ice 20 or other non-distributed cellulosic support material from the ice pile 80 is fed with or without pressure separation into the vessel 81. The chips in the vessel 81 may be treated with a gas such as steam or hydrogen sulfide or a liquid such as water or a liquid containing cooking chemicals fed through a fl your lines 82. The vessel 81 may be of a selectable type, but is preferably a DIAMONDBACK® binge as described above. The treated ice is discharged from the vessel 81 to the conduit 82. Although a dispensing device of selectable type may be used, the discharge of ice from the vessel 81 preferably takes place without mechanical agitation or vibration as is characteristic of DlAMONDßACKdg. fl ice cubes. The conduit 84 may be a tube or shaft of selectable type, but is preferably a curved Chip Tube as described above.

Line 84 feeds the ice into the inlet of the suspension pump 85, which may be of the type supplied by Wemco or Lawrence as described above. Suspension liquid is typically first fed into the ice in line 84, e.g. by using line 82 ', to form a liquid level in the vessel 81 or line 84. The liquid fed via line 82' may consist of water or liquid containing treatment chemicals such as kraft liquor with or without strength or yield enhancing additives. Compensation end, e.g. liquor containing these chemicals is typically added via line 782.

The suspension in line 86 is fed into the subsystem 810 via the liquor separation device 887, which is similar in function to the device 87 shown in FIG. 4. The liquid separated in the separator 887 can be returned to the subsystem 710 via line 88 or removed via line 888 for use elsewhere in the pulp mill. If it is returned to the subsystem 710 via line 88, the liquor can be expanded with additive liquid or chemical via line 788, heated by means of the indirect heat exchanger 90 via line 790 and pressurized by means of the pump 89 before being re-fed into vessel 81 via line 84 or in line 84 via line 822 The subsystem 710 may also include a lye storage container similar to that of FIG. 4, using the heat exchanger 90 and the chemical supply 782 or 788, the material suspension transferred from the subsystem 710 to the subsystem 810 via the line 86 can be heated to a desired temperature while being treated with chemicals. If the suspension in line 86 e.g. is heated to about 90 ° C or above in the presence of alkali or sul fi d a pre-treatment of this takes place while it is in line 86 before the suspension is fed into subsystem 810. Lower temperatures and other chemicals can of course also be used in line 86.

The chips retained by the separator 887 are passed to the vessel 821. The vessel 821 may be similar to the vessel 81, but is preferably a highly cylindrical vessel, e.g. 10 - 50 feet high, in which a liquid level 823 is maintained. A gas space 824 may be maintained above the liquid level 823. The vessel 821 may be maintained at an atmospheric pressure or a higher than atmospheric pressure, e.g. 0.2 - 10 bar overpressure (eg about 5 bar) depending on the treatment carried out in vessel 821. The temperature in vessel 821 can vary from 50 ° C to 300 ° C, but is typically about 50 - 150 ° C. Liquid may be introduced into the vessel 821 via one or more lines 822 or 860. The liquid may contain cooking chemicals or additives as described above.

These cooking chemicals or additives may be the same as those contained in subsystem 710 or may be different. Kraft cooking cloth with a high sulion ion content or sul fi ditet can e.g. is fed into the subsystem 710 and a kraft cooking chemical with a lower sulion ion content or the sulite can be fed into the ice of the subsystem 810. In another example, a polysulde type additive may be fed into the ice of the subsystem 710 and an anthraquinone type additive 8 is fed into the subsystem 810.

The pressure in the vessel 821 can be monitored and regulated via the pressure gauge and regulator 825. An excessively high pressure can be relieved via the line 826, e.g. to a conventional treatment system for non-condensable gases or to the vessel 81 for pretreatment.

The pressure regulator 825 may further be used to regulate the pressure in the vessel 821 to vary the pressure to effect pressure pulsation impregnation as described in U.S. Patents 4,057,461 and 4,743,338.

The suspension is discharged from vessel 821 to line 850. This discharge can be effected without agitation or vibration in a DlAMONDBACK® tlisbinge or in a conventional manner with agitation or vibration. Line 850 feeds the suspension into the inlet of pump 851, which may be similar to pump 85, but typically has a higher pressure value. Additive liquid can be fed into line 850 via line 854 to promote the supply of suspension to pump 851. The suspension flowing out of pump 851 is fed to subsystem 910 via line 886.

The suspension in line 886 is fed into subsystem 910 using the liquor separation device 987. Separators 987 are similar to devices 887 and 87 (in FIG. 4). The liquid removed from the separator 987 can be returned to the subsystem 810 via line 911 or removed via line 988 for use elsewhere in the pulp mill. If returned to subsystem 810 via line 911, the liquor can be expanded with additive liquid or chemical via line 912, heated by the indirect friend exchanger 890 via line 891 and pressurized by pump 889 before being re-fed into vessel 821 via line 822 or 860 or in line 850 via line 854. The liquor in line 911 can also be fed into the subsystem 710, e.g. via a common connection to line 88 or 82. The subsystem 810 may also include a lye storage container similar to that of FIG. 4, using the heat exchanger 890 and the chemical supply 912, the material suspension transferred from the subsystem 810 to the subsystem 910 via the line 886 can be heated to a desired temperature while being treated with chemicals. If the suspension in line 886 e.g. heated to about 90 ° C or above in the presence of alkali or sul fi d, a pre-treatment of this takes place while it is in line 886 before the suspension is fed into subsystem 910. Lower temperatures and other chemicals can of course also be used in line 886.

The chip retained by the separator 987 is passed to the vessel 921, which may be similar to the vessel 81 or a tall vessel similar to the vessel 821 or a vessel similar to the vessel 321 in FIG. 4.

The vessel 921 can be maintained at an atmospheric pressure or a higher than atmospheric pressure (eg 0.2 - 10 bar overpressure, preferably 0.5 - 5 bar overpressure) depending on the treatment carried out in the vessel 921. The temperature in the vessel 921 can vary from 50 ° C to 300 ° C, but is typically about 50 - 150 ° C, preferably about 80 - 120 ° C. Liquid may be introduced into the vessel 921 via one or more conduits 922 or 960. The supplied liquid may contain cooking chemicals or additives as described above. These cooking chemicals or additives may be the same as those fed into subsystems 710 or 810 or may be different.

Kraft cook cloth with a high sulion content or the suldi can e.g. is fed into the subsystem 810 and a kraft cooking chemical with a lower sulion content or the sulite can be fed into the ice of the subsystem 910. In another example a polysulde type additive may be fed into the ice of the subsystem 710 and an anthraquinone type additive may be fed into the subsystem fl the ice in the subsystem 910. Each of these liquors can be separated from each other by means of liquor separators 887 and 987. The suspension is discharged from the vessel 921 to the line 950. This discharge can be effected without stirring or vibration by using a discharge as in a DlAMONDßACKlæ- fl ice binge or with stirring or vibration as is conventional.

Line 950 receives the suspension in the inlet of pump 951, which may be similar to pumps 85 and 851, but typically has a higher pressure value. Additive liquid can be fed into line 950 via line 960 to promote the supply of suspension to pump 951.

The suspension flowing out of the pump 951 is dried for further treatment via the line 886, e.g. to a digester (i.e., a continuous or batch digester) or for further processing in a subsystem similar to subsystems 810 or 910 or subsystem 310 of FIG. However, the treatment performed in subsystems 710, 810 and 910 may be sufficient to provide a substantially fully cooked pulp suspension in line 950 so that no further boiling is required. The fair in line 950 can be taken directly to washing and / or bleaching.

As in subsystems 310, 810 and 910, overflow closures can be returned to subsystem 910 via line 913. The liquor can be expanded with additive liquid or chemical via line 914, heated by the indirect heat exchanger 990 via line 991 and pressurized by pump 989 before being re-fed into the vessel. via line 922 or in line 950 via line 960. The liquor in line 913 can also be fed into subsystems 710 or 810, e.g. via a common connection with line 88 or 82 (not shown) or a common connection with lines 911 or 822 or similar lines.

The subsystem 910 may also include a lye storage container similar to that of FIG. 4 showed the container 353.

Because the chemical supply 914 can use the friend changer 990 the material suspension which is transferred from the subsystem 910 to the subsequent subsystem or the boiler via the line 986 is heated to a desired temperature while being treated with chemicals. If the suspension in line 986 e.g. if heated to about 90 ° C or above in the presence of alkali or sul fi d, a pre-treatment of this takes place while it is in line 986 before the suspension is fed into the subsequent treatment device, e.g. the boiler 11 in FIG. 1 and 2. Lower temperatures and other chemicals can of course also be used in the line 986. 10 15 20 25 30 5310 999 24 Although the indirect friend switches 90, 890 and 990 can each be fed from their respective heat source, e.g. separate steam or hot water sources or a hot discharge that would normally be discharged as sewage, the heat exchangers 90, 890 and 990 can also be fed from a common heat source 915. The heat source 915 can e.g. consist of a hot emission or steam (low, medium or high pressure steam) which can be fed into the friend exchanger 990 and the residual heat can be transferred to the friend exchanger 890 via line 992. The residual heat from heat exchanger 890 can be transferred to heat exchanger 90 via line 892. Any remaining residue line 92 can be used where needed in systems 710, 810 or 910 or elsewhere in the factory or routed away. The liquid in line 92 and any residual friend therein may be fed into vessels 81 or 821 via lines 82 or 822 to recover and reuse as much of the available energy as possible.

Using a system 610 shown in FIG. 5, a countercurrent fate of treatment fluids can be formed between each subsystem. The liquid from an upstream treatment can e.g. returned to subsystem 910 via line 913; the fluid from subsystem 910 can be returned to subsystem 810 via line 911; and the fluid from the subsystem 810 may be returned to the subsystem 710 via line 88. In addition, some or all of these fluids may be removed via lines 888 and 988 and used elsewhere.

The chemical additives at 788, 912 and 914 preferably consist of sodium hydroxide, sodium sulfide; polysulfide, anthraquinone or their equivalents or derivatives; surfactants, enzymes or chelating agents; or combinations thereof. Different treatment chemicals can be added at 788, 912 and 914 so that different treatments take place in parts 710, 810 and 910. Polysul fi d can e.g. added at 788, anthraquinone at 912 and chelating agents and enzymes at 914. Lines 788, 912 and 914 need not be located at the locations shown in FIG. 5, but may be arranged in some other suitable place which facilitates impregnation or other lining treatment at the same time as the transport. Lines 788, 912 and 914 can e.g. be connected to the lines 790, 891 and 991 in front of the heat exchangers 90, 890 and 990, respectively. FIG. 6 schematically shows a device for carrying out a method according to the invention.

When using the system according to FIG. 6, a suspension of distributed cellulosic berm material (typically at a consistency of about 5 - 20%) is transported in a pulp mill at some point along a fi berlin line, such as from the wood yard to a boiler with intermediate auxiliary pumps arranged in series. Each pump is connected to a station (treatment vessel) and a solid and liquid separator is connected to each station (typically a conventional separator arranged at the upper end of the station) for separating liquor streams or circulations. Impregnation or other pre-treatment is carried out simultaneously with the transport of the material in the circulation pipes (ie from a pump to its associated station) and the pipes can be very long (eg more than 90 m or 100 yards, up to about 800 m or a half mile) to facilitate pre-treatment and impregnation. Heat exchangers are preferably used in the return lines and degassing can be arranged at one, fl era than one or all feed stations. A jet pump (ejector) can be used instead of a shut-off vessel and / or control valves through which the liquor is removed and in which the pressure is reduced. Pressurized pulsation can take place in the system of pumps and stations, whereby the pumps pressurize the suspension to a pressure of at least 5 bar (typically at least about 10 bar). Several different treatment chemicals can be used which are preferably added upstream of the pumps, e.g. sodium hydroxide, sodium sulfide; polysul fi d, anthraquinone or their equivalents or derivatives; surfactants, enzymes or chelating agents; or combinations thereof.

The chip suspension 1000 is formed in a conventional manner (which includes, among other things, suspension in hot steam) and a first, second and third auxiliary pump 1001, 1002 and 1003 are connected in series. The pumps 1001 - 1003 are connected to the respective stations (vessels) 1004, 1005 and 1006. A separator for liquid and solid material is preferably connected to each station 1004 - 1006. In the embodiment shown in FIG. 6, the separators are arranged at the upper end of each station (treatment vessel) 1004 - 1006, but the separators may be located in another place e.g. at the lower end.

Chemicals are added to the suspension at different locations in the system, such as upstream of each pump 1001 - 1003. This is shown schematically as a chemical supply at 1010, 1011 and 1012 in FIG. 6. The same or other chemicals may be added at 1010 - 1012. At least some of the chemicals are preferably sodium hydroxide, sodium sulfide; polysul fi d, anthraquinone or their equivalents or derivatives; surfactants, enzymes or chelating agents; or combinations thereof. In the embodiment shown in FIG. 6, the chemical additive 1012 contains white liquor with AQ (the vessel 1006 is, for example, a continuous digester).

Instead of forming circulation lines as shown in FIG. 5, circulation is effected in the inventive embodiment according to FIG. 6 so as to cause a pseudo-current fl fate of the non-distributed cellulosic bone material and the liquid. Although FIG. 6 shows three stations, the number of stations is freely selectable. In the embodiment of FIG. 6, the liquid removed from the separator 1007 in line 1013 elsewhere in the plant or treated for reuse is used. The liquid removed from the separator 1008 is dried in line 1014 to a location upstream of the pump 1001 (it is diverted, for example, by means of the valve 1015 to the suspension station 1000 or to the inlet of pump 1001) while the liquid separated by the third separator 1009 is circulated in line 1016 to a place upstream of the pump 1002, e.g. diverted by valve 1017 to the first station 1004 and / or to a location just upstream of pump 1002. Fresh liquor from source 1012 is added to the lower end of vessel 1005 or to the inlet of pump 1003. arranged in Conventional indirect 1018, 1019 may be the return lines 1014, 1016 for changing the temperature of the liquid therein with at least 5 ° C heat exchanger. In the embodiment shown, the liquor is heated, but in some cases the liquid can be cooled instead of heated. An indirect heat exchanger 1020 may also be connected to the nuclear supply 1012.

Lye can be passed from the third station 1006 (which may be a digester - eg black liquor) through a conventional jet pump (not ector) 1022 instead of a shut-off vessel and / or a control valve. Each pump 1001 - 1003 preferably pressurizes the suspension to a pressure of at least 5 bar (typically at least about 10 bar). 10 5313 599 27 Degassing can also be arranged to take place in one, in more than one or in all the stations 1004.

This is shown schematically by the gas removal lines 1023 - 1025 in FIG. 6.

The degassing is achieved by using conventional degassing equipment connected to the separator 1007 - 1009, the inlet line or the like.

The invention relates to the widest extent to procedures for transport and treatment in your stages of distributed cellulosic carrier material with economical recovery and reuse of energy, e.g. thermal energy.

Claims (11)

10 15 20 25 30 530 999 28 PATENT REQUIREMENTS 1. ~ 1._ Process for the treatment of unevenly distributed cellulosic base material in the cooking of pulp by using a first and a second series-connected pump and at least one associated first and second series-connected treatment vessel, respectively, each vessel being provided with a solid separator. and liquid, comprising the steps of: (a) pumping a suspension of distributed cellulosic carrier material using the series-connected pumps; (b) liquid is separated and the suspension is removed at each vessel to substantially separate liquor circulations and fl and to recirculate removed liquid from at least one of the vessels to a location upstream of one of the pumps; (c) treatment chemicals are added to the suspension upstream of at least one of the pumps so that the material is dry treated while being transported from this pump to its associated vessel; and (d) liquid removed from the second vessel is circulated to a location upstream of the first pump. A method according to claim 1, comprising using at least a first, second and third pump and vessel, and comprising a further step (e) wherein liquid removed from the third vessel is circulated to a location upstream of the second pump, wherein it the third vessel is a boiler. A method according to claim 2, comprising a further step wherein the removed liquid while performing at least one of steps (d) and (e) is dried through a heat exchanger to change its temperature by at least about 5 ° C. A method according to any one of claims 1-3, comprising the step (c) performed by adding another chemical or combination of chemicals upstream of each pump so that a substantially different treatment of the material in the suspension takes place during the transport of the suspension from was pumped to its associated vessels; and that step (a) is performed to pressurize the suspension to a pressure of at least 5 bar. 10 15 20 25 30 EQÜ 995 29 A method according to any one of the preceding claims, wherein the treatment chemicals consist of at least one chemical selected from a group consisting essentially of sodium hydroxide, sodium sulfide; polysul fi d, anthraquinone or their equivalents or derivatives; surfactants, enzymes or chelating agents; or combinations thereof. A process for treating a distributed cellulosic bone material in the production of pulp by using at least a first, second and third series-connected pump and at least one associated first, second and third series-connected treatment vessel, the vessels each being provided with a solid separator material and liquid, comprising the following steps: (a) a suspension of distributed cellulosic carrier material is pumped using the series-connected pumps; (b) liquid is separated and removed from the suspension at each vessel to substantially separate lye circulations and fl and to recirculate removed liquid from at least one of the vessels to a location upstream of one of the pumps; (c) chemicals are added to the suspension upstream of each pump, the chemicals being at least one chemical selected from a group consisting essentially of sodium hydroxide, sodium urn sulfide; polysul fi d, anthraquinone or their equivalents or derivatives; surfactants, enzymes or chelating agents; or combinations thereof; so that the material is pretreated while being transported from the respective pump to the associated vessel; (d) liquid removed from the third vessel is circulated to a location upstream of the second pump; and (e) liquid removed from the second vessel is circulated to a location upstream of the first pump, the third treatment vessel being a digester. A method according to claim 6, comprising the further step of degassing the suspension at at least one of the vessels. A method according to any one of claims 6 to 7, comprising a further step wherein the removed liquid, while performing at least one of steps (d) and (e), is passed through a heat exchanger to change its temperature by at least about 5 ° C. 10 530 999 30 A method according to any one of claims 6-8, comprising the step (c) being performed by adding another chemical or combination of chemicals upstream of each pump so that a substantially different treatment of the material in the suspension takes place during the transport of the suspension from the respective pump to its associated vessels. A method according to any one of claims 6-9, comprising the step (a) of performing pressurizing the suspension to a pressure of at least 5 bar. 11. ll. A method according to any one of claims 6-10, comprising a further step where liquid is dried from at least one of the vessels by means of an ejector instead of a shut-off vessel or a control valve.