SE1050032A1

SE1050032A1 - System and method for treating bulk material in a pneumatic steam dryer

Info

Publication number: SE1050032A1
Application number: SE1050032A
Authority: SE
Inventors: Per Lysedal
Original assignee: Skellefteaa Kraftaktiebolag
Priority date: 2010-01-14
Filing date: 2010-01-14
Publication date: 2011-07-15
Also published as: EP2524182B1; EP2524182A1; SE534591C2; EP2524182A4; WO2011087434A1; DK2524182T3

Abstract

28 Abstract The invention relates to a process and system for treating bulk material. ln particular theinvention relates to drying bulk material in a pneumatic steam dryer and treating the bulkmaterial before and/or after the pneumatic steam dryer in a bulk material handling system.The process for treating bulk material according to the invention comprises -feeding bulk material by an inlet feeding device (131 ,401) into a steam filled circulationconduit (105) of a pneumatic steam dryer (100) operating above atmospheric pressure-heating said steam by heating means (121), -drying said bulk material in a drying conduit (111) by heat transfer from said steam therebyforming surplus steam, -separating said bulk material from said steam by a first separating means (150),-pneumatically conveying said bulk material suspended in said steam through said dryingconduit from said inlet feeding device (131,401) to said first separating means (150),-releasing surplus steam from said circulation conduit (105), -discharging said bulk material by an outlet feeding device (141) from said pneumatic steamdryer thereby generating flash and leakage steam, and utilizing said flash and leakage steam in a bulk material handling system (200;200';200")connected to said pneumatic steam dryer(100). To be published with Fig. 1 W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_O85750_PRVFiling.doc

Description

Process and system for treating bulk material Field of the invention The present invention relates to a process for treating bulk material. The invention also relates to a system for treating bulk material.

Background of the invention Drying of bulk material in a pneumatic dryer is previously known. Wet bulk material is fed intoa drying enclosure of the pneumatic dryer and dried by heated gas. The dried bulk material isseparated from the gas by separating means and discharged from the pneumatic dryer. Thedried bulk material is typically used as fuel in different industrial, commercial or domestic applications.

To improve the drying process and the quality of the final product different operations areused for treating the bulk material in connection with the pneumatic dryer. These operations are energy consuming and costly.

Summary of the invention lt is an object of the present invention to provide an energy efficient process and system for treating bulk material.

This object and other objects are met by the invention as defined in the independent claims.

According to a first aspect of the present invention there is provided a process for treatingbulk material. Said process comprises feeding bulk material by an inlet feeding device into asteam filled circulation conduit of a pneumatic steam dryer operating above atmosphericpressure, heating said steam by heating means, drying said bulk material in a drying conduitby heat transfer from said steam thereby forming surplus steam, separating said bulkmaterial from said steam by a first separating means, pneumatically conveying said bulkmaterial suspended in said steam through said drying conduit from said inlet feeding deviceto said first separating means, releasing surplus steam from said circulation conduit anddischarging said bulk material by an outlet feeding device from said pneumatic steam dryerthereby generating flash and leakage steam. The process further comprising utilizing saidflash and leakage steam in a bulk material handling system connected to said pneumatic W:\|nprotech_Casedocuments\Patent\P40901194SEOO_20091217_O85750_PRVFiling.doc steam dryer.

According to a second aspect of the present invention there is provided a system for treatingbulk material. Said system for treating bulk material comprising a pneumatic steam dryerbeing adapted to operate above atmospheric pressure, said pneumatic steam dryercomprising a circuiation conduit which in operation is filled with steam, heating meansconnected to said circuiation conduit for heating said steam, an inlet feeding deviceconnected to said circuiation conduit for feeding bulk material into said circuiation conduit, a drying conduit connected into said circuiation conduit wherein said bulk material is dried byheat transfer from said steam thereby forming surplus steam, first separating meansconnected to said drying conduit for separating said bulk material from said steam, a fan connected into said circuiation conduit for pneumatically conveying said bulk materialsuspended in said steam through said drying conduit from said inlet feeding device to saidfirst separating means, a surplus steam outlet connected to said circuiation conduit forreleasing surplus steam from said circuiation conduit, an outlet feeding device for dischargingsaid bulk material from said pneumatic steam dryerthereby generating flash and leakagesteam. Said system further comprises a bulk material handling system connected to saidpneumatic steam dryer for utilizing said flash and leakage steam.

Flash and leakage steam is generated when bulk material is depressurized by dischargefrom the internal pressurized environment of the pneumatic steam dryer to a lower pressureoutside the pneumatic steam dryer. Residual moisture which is contained in the bulk materialat the end of the drying process vaporizes and forms flash steam. Addtionally leaks somepressurized steam from the outlet feeding device and forms leakage steam. Some minoramounts of steam may also be generated by elements of the bulk material handling system.This is added to the flash and leakage steam. The flash and leakage steam also comprises volatiles like hydrocarbons and terpens evaporated from the bulk material.

The present invention thus provides a process as well as a pneumatic steam dryer whichenables treating of bulk material energy efficiently since the flash and leakage steam is asource of energy of low cost which provides several functional benefits. One advantage isthat several final products of bulk material having uniform particle size distribution areproduced in a safe, substantially oxygen free environment.

Another advantage is that the process provides for energy efficient conditioning of wet bulk material. The moisture content of the wet bulk material is consequently decreased in advance of feeding the material into the dryer and less energy is consumed in the pneumatic W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_O85750_PRVFiling.doc steam dryer. The heat economy of the pneumatic steam dryer is thereby improved.A further advantage is that the quality of the treated final product is improved in an environmentally responsible way.

Another advantage is that by using flash and leakage steam in the bulk material handlingsystem it is avoided to use other more expensive energy sources to provide the same desirable effects.

Furthermore, the latent heat in the flash and leakage steam is efficiently utilized andrecovered in the bulk material handling system. Other devices for recovering the energy inthe flash and leakage steam are not necessary. Moreover, it is not necessary to dedust theflash and leakage steam (e.g. by filtering or similar) before recovering the latent heat which is advantageous.

Example embodiments of the invention are defined in the dependent claims. ln addition thepresent invention has other advantages and features apparent from the description below. ln one embodiment of the invention the process and system for treating bulk materialaccording to the present invention comprises a pneumatic steam dryer and a bulk materialhandling system connected to the bulk material outlet of said pneumatic steam dryer. ln thisembodiment of the invention the bulk material handling system comprises a controllingsection connected to the outlet feedíng device of the pneumatic steam dryer wherein theflash and leakage steam is utilized to provide a safe environment for treating dried bulkmaterial and as transport medium. Furthermore the heat in the flash and leakage steam is used to improve the operations of a milling means and/or pelleting press. ln another embodiment of the invention the process and system for treating bulk materialaccording to the present invention comprises a pneumatic steam dryer and a bulk materialhandling system connected to the bulk material inlet of said pneumatic steam dryer. ln thisembodiment of the invention the bulk material handling system comprises a bulk materialconditioning device wherein the energy in the flash and leakage steam is utilized and recovered by condensation. ln a further embodiment of the invention the process and system for treating bulk materialcomprises a pneumatic steam dryer and a bulk material handling system connected both tosaid inlet and said outlet of the pneumatic steam dryer. ln this embodiment the two previously mentioned embodiments are combined, whereby further functional benefits and W:\|nprotech_Casedocuments\Patent\P40901 194SE00_20091217_085750_PRVFi|ing.doc 4 advantageous effects are achieved which are described below. ln this specification 'bulk material' has a broad meaning which includes any moist or wet solidorganic bulk material with a size distribution and partícle density suitable for pneumatictransport. The bulk material particularly includes biomass originating from plants. Examplesinclude agricultural residues and wastes (stalks, straw etc), wood based feedstock (woodchips), forest residues; sawmill wastes, peat, energy crops. These bulk materials usuallyhave an initial moisture content of at least 40% moisture on a weight basis, typically above 50% moisture.

The present invention relates to a process and a system for treating preferably biomass based bulk materials, more preferably wood and peat based bulk materials.

Brief description of figures Embodiments will now be described, by way of example, with reference to the accompanying flow schemes in which Figure 1 shows a first embodiment of the system according to the present inventionFigure 2 shows a second embodiment of the system according to the present inventionFigure 3 shows a third embodiment of the system according to the present invention Detailed description of preferred embodiments of the invention Fig. 1 shows a first embodiment of the system according to the invention for treating bulkmaterial which comprises a pneumatic steam dryer 100 and a bulk material handling system200 connected to a bulk material inlet of said pneumatic steam dryer. ln this embodiment isflash and leakage steam utilized in the bulk material handling system 200 connected to a bulk material outlet of a pneumatic steam dryer.

The invention provides a pneumatic steam dryer 100 for drying bulk material 101 comprisinga drying section 110 and a heating section 120 connected to each other to form a circulationconduit 105. ln operation of the pneumatic steam dryer 100, the circulation conduit 105 ispressurized and filled with steam 102 such as superheated or saturated steam, therebyforming a substantially oxygen free, inert, internal environment which prevents hazardousdust explosions. The oxygen content is preferably below 10%, more preferably below 5%.

The circulation conduit further comprises ducts for conducting bulk material and steam W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_085750_PRVFiling.doc between the elements of the pneumatic steam dryer. All elements and auxiliary equipments are designed to be operated above atmospheric pressure.

The drying section comprises a bulk material inlet 130, a drying conduit 111 and separatingmeans 150. The bulk material inlet 130 comprises an inlet feeding device 131 connected intothe circulation conduit 105 downstream of the heating section 120 in relation to the directionof the flow of steam. Wet bulk material is continuously or intermittently fed into the flow of said steam by the inlet feeding device 131.

The wet bulk material comprises particles of organic matter. The pneumatic steam dryer 100typically receives particles of the size <25 mm at the bulk material inlet of the pneumaticsteam dryer. The particles have a size distribution and particle density suitable for pneumatictransport. The size distribution of the particles at the bulk material outlet of the dryer istypically the same as before drying.

The inlet feeding device 131 comprises a pressure tight cellular feeder or a similar feedingdevice which is adapted to avoid pressure loss from the circulation conduit and only providesfor a marginal steam leakage at the actual differential pressure between the outside pressure of the pneumatic steam dryer and the pressure inside the circulation conduit.

A drying conduit 111 is connected between the bulk material inlet 130 and the separatingmeans 150. The drying conduit 111 typically comprises an elongated conduit consisting of aseries of vertical pipes which are connected together in the upper and lower ends by bentpipes. The residence time of the bulk material in the drying section is very short,approximately less than 2 minutes. However also other types of chambers which can beconnected into the pneumatic steam dryer and through which pneumatic transport of the bulk material in a fluidized state are likewise possible.

The bulk material is dried by the superheated steam in the drying conduit while beingtransported to the separating means. Moisture and volatiles such as hydrocarbons andterpens in the wet bulk material vaporizes and forms surplus steam. The temperature of thesteam decreases when the moisture evaporates from the bulk material. Consequently the moisture content of the bulk material is reduced.

The dried bulk material suspended in steam is conducted to the separating means 150connected to the drying conduit 111.

W:\lnprotech_Casedocuments\Patent\P40901194SEOO_20091217_085750_PRVFiling.doc The separating means 150 comprises at least one cyclone which separates the dried bulkmaterial 101 from said steam 102. The dried bulk materia! 103 is collected at the lowerportion of the cyclone where an outlet feeding device 141 is connected and discharges thedried bulk material. The cyclone comprises a gas outlet 152 in the upper portion of thecyclone 150, said gas outlet 152 is connected to the heating section 120 of the circulationconduit 105 whereby the separated steam is returned to the heating section. The outletfeeding device 141 is pressure tight and typically of the same kind as the inlet feeding device131 described above. A bulk material outlet 140 of the pneumatic steam dryer is connectedto the outlet feeding device 141.

The heating section 120 comprises a fan 160, heating means 121 and a surplus steam outlet170. The fan 160 generates a flow of steam 102 circulating in the circulation conduit 105.The heating means 121 is connected into the circulation conduit between the fan and theinlet feeding device of the drying section. The fan conveys steam 102 through the heatingsection. The heating means 121 comprises a heat exchanger which indirectly superheatsthe steam to above 200 °C. The heat exchanger is supplied by primary heat from flue gas,pressurized steam, hot water, thermal oil or similar from a heat source. ln particular industrialprocesses using steam, for example a combined heat and power plant, a paper mill, a steam generation plant or similar are used for supplying heat to the pneumatic steam dryer 100.

Optionally, a further heat exchanger may be connected into the drying section 110 to furtherheat the steam and the bulk material suspended therein.

Furthermore, the heating section 120 also comprises a surplus steam outlet 170 whichreleases pressurized surplus steam evaporated from the bulk material into energy recoverymeans. The operating conditions such as the pressure and/or the temperature of the pneumatic steam dryer 100 are thereby controlled and maintained.

The energy recovery means comprises for example a steam regenerator. ln the energyrecovery means, the surplus steam is cooled and depleted of energy, whereby clean steamand waste condensate is generated.

The dried bulk material 103 discharged from the pneumatic steam dryer 100 is typically usedas fuel in combustion chambers in industrial , commercial or domestic applications. Another application of the dried bulk material is in wood based polymer composites. ln particular when the bulk material 101 is originating from wood or forest products, the W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_085750_PRVFiling.doc energy content in the dried material 103 is high and can be used for production of fuel pelletsor be used as fuel in a combined heat and power plant or steam generation plant supplyingthe pneumatic with heat. The bulk material is advantageously dried to different moisturecontents depending on the final use of the dried product. ln case the dried bulk material is tobe used in the production of fuel pellets, the moisture content is advantageously below 12 % by weight. lf the dried bulk material is used in the production of wood polymer composites the moisturecontent is advantageously below 2% by weight, preferably below 1% by weight, most preferably below 0,5 % by weight.

The pneumatic steam dryer 100 is advantageously operated above atmospheric pressure.This means that the overpressure range is typically from 1 to 40 Bar, preferably from 2 to15Bar, more preferably from 2 to 10 Bar, most preferably from 2 to 5 Bar. The overpressurerange from 2.5-4.5 Bar has proven to be particularly suitable for the drying process and theevaporation capacity of the drying steam. The possibilities to utilize the vast heat source byrecovering the latent heat in the surplus steam increases with the temperature i.e. with the steam pressure inside the pneumatic steam dryer 100.

The system in Fig.1 shows furthermore a bulk material handling system 200 connected to thebulk material outlet 140 of the pneumatic steam dryer 100 described above. Flash andleakage steam 104 is generated when the bulk material is discharged from the pneumaticsteam dryer. The flash and leakage steam is utilized in the bulk material handling system 200 in accordance with the present invention. ln this embodiment of the invention the process comprises utilizing of said flash and leakagesteam 104 by a bulk material handling system 200 connected to a bulk material outlet 140 ofsaid pneumatic steam dryer 100. The process comprises receiving said flash and leakagesteam and dried bulk material by said bulk material handling system 200 from said outletfeeding device 141 and controlling of said bulk material by a controlling section 300.

The bulk material handling system 200 comprises a controlling section 300 connected to saidoutlet feeding device 141 of said pneumatic steam dryer for receiving the flash and leakagesteam and the bulk material from said outlet feeding device. The flash and leakage steam 104 is efficiently utilized to improve the operation of the controlling section 300.

The feedstock fed to the pneumatic steam dryer varies. lt is increasingly more difficult to find high quality feed stock to a reasonable cost and a lower quality and/ or different type is more W:\|nprotech_Casedocuments\Patent\P40901194SEO0_20091217_085750_PRVFiling.doc frequently used. Nevertheless the quality of the final products from the pneumatic steamdryer needs to be maintained and preferably improved. Furthermore, the drying process isvery energy consuming and it is necessary to avoid any increase of energy consumption dueto the Iowered quality and/or different feedstock. ln addition, dried bulk material has a moisture content of typically less than 12% afterdischarge from the pneumatic steam dryer. Handling of heated dried bulk material in anenvironment with an oxygen content of more than 10% has proven to be very dangerous with regards to the risk of dust explosions.

To address this problem this embodiment of the present invention provides a bulk materialhandling system 200 comprising a controlling section 300 connected the bulk material outlet140 of the pneumatic steam dryer which utilizes the low cost flash and leakage steam to provide a safe environment for treating the dried bulk material.

The controlling section 300 provides for controlling of the particle size distribution of the driedbulk material. Furthermore, indirectly also the moisture content in the final dried products iscontrolled and the mass ratio between the products is controlled. This means that inoperation of the system, one or more final products are produced. Each product comprises a predefined particle size distribution.

According to the present invention the process comprises advantageously pneumaticallyconveying said flash and leakage steam through said controlling section thereby forming asubstantially oxygen free environment inside said controlling section. This has the functionalbenefit that the risk of hazardous dust explosions is eliminated which improves the safety ofthe controlling section. The conduits, ducts and operating elements of said controlling section forms a controlling section loop wherein the flash and leakage steam is circulated.

The controlling section is adapted to operate near atmospheric pressure, at a slightoverpressure. This means that the controlling section operates in the interval 0.1-1.0 Bar, preferably 0.2-0.8 Bar, most preferably 0.3-0.7 Bar.

The controlling section 300 comprises a first classifier 310, a second classifier 320, a second separating means 330, a fan 370, milling means 340 and pellet press 350.The controlling section is connected to the bulk material outlet 140 of said pneumatic steam dryer. Said bulk material outlet 140 comprises an outlet feeding device 141 and means forcoupling said controlling section to said outlet feeding device. The bulk material is discharged W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_085750_PRVFiling.doc into the controlling section whereby flash and leakage steam is generated. Flash andleakage steam 104 and dried bulk material 103 suspended therein is pneumatically conveyed in the direction towards a first classifier 310.

The process preferably comprises classifying of said bulk material into at least a first fractionand a second fraction by a first classifier 310 inside said controlling section 300.

The first classifier 310 comprises a mechanical separation device, further described below.The first classifier 310 may alternatively comprise an aerodynamic classifier, further described below.

Said first classifier 310 comprises a first classifier housing. The first classifier housingcomprises a first classifier inlet 311, a first fraction outlet 312 and a second fraction outlet313.

The first fraction outlet 312 corresponds to the reject outlet of said first classifier 310. Hencethe first fraction comprises the rejected coarse particles of the bulk material.The second fraction outlet 313 corresponds to the accept outlet of said first classifier 310.

Hence the second fraction comprises the accepted particles of the bulk material.

Said first classifier inlet 311 of the first classifier 310 is connected to the outlet feeding device141 to receive the bulk material and whereby said first classifier 310 classifies said bulkmaterial into at least a first fraction and a second fraction. The flash and leakage steam ispneumatically conveyed to the first classifier together with the bulk material.

The first fraction is discharged from the first classifier via the first fraction outlet 312. The firstfraction is supplied to milling means 340 preferably by gravitation. Flash and leakage steamis led to the milling means 340 simultaneously with the first fraction. Said milling means arefurther described below.

The second fraction is discharged from the first classifier 310 via the second fraction outlet313.

Advantageously the process comprises classifying of said second fraction by a secondclassifier 320 into a third fraction and a fourth fraction inside said controlling section 300. Thecontrolling section preferably comprises a second classifier 320 connected to the secondfraction outlet 313 of the first classifier 310. The second fraction is pneumatically conveyed from the second fraction outlet to said second classifier 320.

The second classifier 320, preferably an aerodynamic classifier, comprises a second W:\|nprotech_Casedocuments\Patent\P40901194SEO0_20091217_085750_PRVFiling.doc classifier housing, second classifier housing comprises a second classifier inlet 321, a third fraction outlet 322 and a fourth fraction outlet 323.

The third fraction outlet 322 corresponds to the reject outlet of said second classifier 320.Hence the third fraction comprises the rejected particles of said second fraction fed to thesecond classifier. The fourth fraction outlet 323 corresponds to the accept outlet of saidsecond classifier 320. Hence the fourth fraction comprises the accepted particles of saidsecond fraction fed to the second classifier.

The second classifier 320 receives said second fraction from said first classifier 310 andclassifies said second fraction into a third fraction and a fourth fraction. The second classifier 320 comprises preferably an aerodynamic classifier further described below.

The second fraction outlet 313 of the first classifier 310 may alternatively be connected to apellet press inlet 351 of a pellet press 350 further described below. ln the embodiment of the system shown in Fig. 1 is the third fraction outlet 322 of the secondclassifier 320 connected via an outlet feeding device to a pellet press inlet 351 such as aring-and-roll press or an extruding press. The third fraction is preferably discharged by gravitation into said pellet press 350.

The process advantageously comprises separating said fourth fraction from the conveyingflash and leakage steam by a second separating means 330. The system in Fig 1. comprisesa second separating means 330 connected to said second classifier 320 to receive andseparate said fourth fraction from the flash and leakage steam. The second separatingmeans such as a cyclone 330 is connected to said fourth fraction outlet 323. Said separatingmeans comprises a second separating means inlet 331, a gas outlet 333 and a materialoutlet 332. Said fourth fraction suspended in flash and leakage steam is pneumaticallyconveyed from said second classifier 320 to said second separating means 330. Said fourthfraction is separated and discharged via said material outlet 332.

A fan 370 is connected to the gas outlet 333 of the second separating means. Said fan propels the flash and leakage steam through the controlling section loop, see Fig.1.

The controlling section also comprises a flash and leakage steam outlet indicated by 360 torelease flash and leakage steam from the controlling section loop to control the pressure inthe loop. The flash and leakage steam which has been released from the controlling loop isadvantageously further recovered in an external heat recovery system like a district heating net or the like.

W:\lnprotech_Casedocuments\Patent\P40901194SEOO_20091217_085750_PRVFiling.doc 11 The process comprises advantageously classifying said bulk material by aerodynamicClassification in said first classifier 310. Such classifiers separates the bulk materialaccording to size and/or specific gravity of the particles and is known to achieve a sharpparticle size distribution, a sharp cut-point, between the separated fractions. An aerodynamiccentrifugal classifier, also known as rotary aerodynamic classifier, is particularly suitable.However also a zigzag aerodynamic classifier may be used to achieve the same effect. Thefirst classifier 310 preferably comprises a rotary aerodynamic classifier. Also the secondclassifier 320 preferably comprises a rotary aerodynamic classifier. The skilled personappreciates that the cut point of the rotary aerodynamic classifier can be adapted accordingto desirable particle size distribution of the fractions. Consequently also the mass flow ratio between the separated fractions is controlled.

Alternatively the process comprises classifying said bulk material by mechanical separationin said first classifier 310. Mechanical separation devices has a broad meaning and includessifters, sieves and screens which in operation separates the bulk material into at least twofractions by vibration, oscillation, tilting, wobbling or the like. The skilled person appreciatesthat minor adaptations of the feeding system are necessary to provide for efficient transport of the dried bulk material into the mechanical separation device.

By classifying and separating the dried bulk material received by the controlling section 300into at least a first fraction and a second fraction it is possible to control the dried bulkmaterial and to achieve final products of high quality. The first fraction contains the particlesof said bulk material which are coarse and/or insufficiently dry. These particles are rejectedby the first classifier.

The second fraction contains the particles of said bulk material which are smaller than aparticular size specification which corresponds to the cut-point of the first classifier. Theseparticles are accepted by the first classifier. However, the second fraction also contains allthe fines of the dried bulk material.

The second classifier 320 separates the second fraction into a third and a fourth fraction.The third fraction comprises the coarser particles of the second fraction rejected by thesecond classifiers. The fourth fraction comprises the finer particles of the second fractionwhich are accepted by the second classifier.

The third fraction is particularly suitable to be used in the production of bio fuel pellets forindustrial/ commercial/domestic purposes. As the fines have been separated from the third fraction, the bio fuel pellets release less dust which improves the quality of the fuel pellets.

W:\lnprotech_Casedocuments\Patent\P40901194SEOO_20091217_085750_PRVFiling.doc 12 Alternatively, the third fraction may also be used in the production of wood polymercomposites.

The fourth fraction contains the fines. The fines contains an elevated level of ash incomparison with the third fraction which makes the fourth fraction less suitable forcombusting in small typically domestic combusting chambers. On the contrary, the fourthfraction is particularly suitable as pulverized fuel in large scale pulverized fuel fired combustion chambers.

The process comprises advantageously disintegrating of said first fraction by milling means340 inside said controlling section. The controlling section comprises a milling meansconnected to the first fraction outlet 312 of said first classifier 310 to receive the coarse first fraction and to disintegrate said coarse first fraction.

The milling means 340 comprises a milling means inlet 341 suitable to receive bulk materialand flash and leakage steam, a milling chamber where said disintegrating of said first fractionis carried out and a milling means outlet 342 suitable for discharging disintegrated bulkmaterial and flash and leakage steam out of said milling means 340. The milling means 340are preferably adapted to disintegrate coarse particles. The milling means 340 comprisespreferably an aspirated type of mill for example a hammer mill or a vertical rotor mill.

The flash and leakage steam 104 conveys the dried bulk material 103 through the controllingsection. The temperature of the flash and leakage steam and the bulk material isapproximately 100 °C after discharging by the outlet feeding device of the pneumatic steamdryer. The temperature of the bulk material is therefore still elevated when the bulk materialis fed into the milling means. Depending on the selected mill this is particularly advantageousbecause the milling operation improves and the specific power consumption of the millingmeans decreases. A vertical rotor mill is particularly suitable for this. The bulk material is alsofurther dried in the milling operation.

Furthermore also flash and leakage steam is fed with the dried bulk material into the millingmeans 340. Low oxygen content inside the milling means is thus maintained which eliminates hazardous dust explosions.The mill generates disintegrated bulk material. The embodiment shown in Fig 1. indicatesseveral alternative variants to further treat the disintegrated bulk material obtained by milling.

Valves indicated by 515 allows for the different alternative variants to be implemented. ln one variant of the process is the disintegrated bulk material obtained from said milling means 340 supplied to the inlet feeding device 131 of the pneumatic steam dryer 100 and W:\lnprotech_Casedocuments\Patent\P40901194SEOO_20091217_085750_PRVFiling.doc 13 feeding said disintegrated bulk material into said circulation conduit of the pneumatic steamdryer, thereby further drying the disintegrated bulk material. To accommodate for this is theinlet feeding device 131 connected to said milling means outlet 342 via a third separatingmeans 510 to receive disintegrated bulk material obtained by milling and to feed the disintegrated bulk material into said circulation conduit of said pneumatic steam dryer. ln an alternative variant of the process is the disintegrated bulk material from said millingmeans supplied to a pellet press 350' further described below. To accommodate for this inthe embodiment of the system shown in Fig. 1 is said milling means outlet 342 connected toa pellet press inlet 351' to supply disintegrated bulk material obtained by milling of said firstfraction to said pellet press 350' to further pelletize said disintegrated bulk material. ln a further alternative variant the process is the disintegrated bulk material from said millingmeans 340 supplied into said first classifier 310 and the disintegrated bulk material obtainedfrom said milling means 340 is classified by said first classifier. To accommodate for this issaid milling means outlet 342 connected to the first classifier inlet to supply disintegrated bulkmaterial obtained by milling of said first fraction to said first classifier to further classify said disintegrated bulk material (not shown in Fig. 1).

The process comprises advantageously pelleting of said third fraction by a pellet press 350connected into said controlling section 300. Hence, the system comprises preferably a pelletpress 350 connected to the third fraction outlet 322 of said second classifier 320 to receiveand pelletise said third fraction. The process may alternatively comprise pelleting of thesecond fraction by a pellet press 350 connected to the controlling section. To accommodatefor this alternative, the controlling section comprises said first classifier 310, said secondseparating means 330, a cyclone, connected to the first fraction outlet of the first classifier310 and a pellet press 350 connected to the material outlet of said second separating means to receive and pelletise said second fraction (not shown in figures).

The pellet press 350 comprises a roller-and-ring press or alternatively an extruder. A roller-and-ring press is typically used for pelleting the dried bulk material into fuel pellets.

An extruder is typically used for producing wood polymer composite pellets which aresuitable to be used in a variety of applications such as in the production of constructionmaterials.

To produce the wood polymer composite pellets is the third fraction mixed with granulate formed thermoplastic material and the mixture is extruded by an extruder connected into said W:\|nprotech__Cased0cumentS\Patent\P40901 194SEOO_20091217_O85750_PRVFiling.doC 14 controlling section. To accommodate for this alternative process comprises the controllingsection an extruder which is connected to said second classifier 320 to receive said thirdfraction. Granulate formed thermoplastic material is additionally fed to the extruder from an external container 380 and mixed with the third fraction.

One advantage of feeding the pellet press 350 from the first classifier 310 or the secondclassifier 320 in the controlling section is that pelleting (or extruding) is carried out while thetemperature of the dried bulk material is still elevated. The presence of flash and leakagesteam in the conduits of the controlling section improves forming of pellets. Pellets are moreeasily formed/extruded when the bulk material is Warm. No other means for heat conditioningthe dried bulk material is necessary which improves the energy efficiency. The flash and leakage steam is also beneficial for safety reasons as previously described.

The process and system for treating bulk material according to this embodiment of theinvention is suitable for producing homogenous final dried products with well defined particlesize distribution. The following are non limiting examples of final products which can beproduced by the process and system for treating bulk material according to this embodimentof the invention.

Coarse final product 4mm < dgy < 10 mm particularly for pellets and briquettes or similar.Fine final product 0.7mm < d97 < 2.5 mm, particularly for pulverized fuel ﬁring or similar.Very fine final product 200 um < dg; < 400 um, particularly for wood polymer composites or similar. ln operation of the system for treating bulk material shown in Fig. 1 two final products withrespectively different particle size distributions are produced represented by the third fraction and the fourth fraction.

Since the quality of the final products is controlled in the controlling section, a variety ofquality/type of bulk material can be treated by system for treating bulk material according tothe invention.

Second embodiment of the present invention Fig. 2 shows a second embodiment of system according to the invention which comprises a pneumatic steam dryer 100 (previously described) and a bulk material handling system 200'connected to a bulk material inlet of said pneumatic steam dryer. The bulk material handling W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_085750_PRVFiling.doc system 200' is connected to a bulk material outlet 140 of said pneumatic steam dryer 100 to receive and utilize the flash and leakage steam.

This embodiment comprises the previously described pneumatic steam dryer 100 and thedrying process carried out by said pneumatic steam dryer which is therefore not furtherdescribed here.

Furthermore, like references are used for like features. ln this embodiment of the invention the bulk material handling system comprises a bulkmaterial conditioning device wherein the energy in the flash and leakage steam is utilizedand recovered by condensation. Preferably comprises the process utilizing and recovering ofsaid flash and leakage steam by conditioning wet bulk material in a conditioning section 400of said bulk material handling system 200”. Advantageously comprises the processsupplying flash and leakage steam to said conditioning section 400 from said outlet feedingdevice 141 of said pneumatic steam dryer.

Advantageously comprises the process conditioning said bulk material in a bulk materialconditioning device 402 directly preceding an inlet feeding device 401. Preferably comprisesthe process conditioning said bulk material by condensing said flash and leakage steam in said bulk material in a steam condensing screw feeder 402.

Advantageously comprises the process supplying said flash and leakage steam countercurrently to the direction of movement of said bulk material inside said steam condensingscrew feeder 402.

Advantageously comprises the process compressing and dewatering of said bulk material bysaid inlet feeding device 401 in advance of feeding the bulk material into the pneumatic steam dryer 100.

The process comprises utilizing and recovering of flash and leakage steam 104 by a bulkmaterial handling system 200' connected to a bulk material inlet 130 of said pneumatic steam dryer.

The process according to this embodiment of the invention is carried out by a system fortreating bulk material shown in Fig. 2. The system for treating bulk material comprises a bulk material handling system 200' which comprises a conditioning section 400 connected to said W:\lnprotech_Casedocuments\Patent\P40901194SEOO_20091217_085750_PRVFiling.doc 16 bulk material inlet 130 of said pneumatic steam dryer for receiving wet bulk material 101,Conditioning said wet bulk material, dewatering the conditioned bulk material and feeding the dewatered bulk material into said pneumatic steam dryer.

Said conditioning section 400 is connected to the bulk material outlet 140 via a flash andleakage steam conduit 403 to receive flash and leakage steam which is to be utilized. Theconditioning section 400 comprises a wet bulk material inlet 420, a bulk material conditioning device 402 and an inlet feeding device 401.

A container 421 is provided for holding wet bulk material 101 and a screw feeder 422 forfeeding said material via the wet bulk material inlet 420 into the bulk material conditioningdevice 402.

The inlet feeding device 401 is connected between the bulk material conditioning device 402and the bulk material inlet 130 of the pneumatic steam dryer.

Said bulk material conditioning device 402 is connected directly preceding said inlet feedingdevice 401. The bulk material conditioning device 402 comprises preferably a steamcondensing screw feeder or a rotating tumbler wherein the flash and leakage steam is utilized and recovered by condensation.

The steam condensing screw feeder 402 comprises an elongated body which comprises afirst end indicated by 405 connected to said screw feeder 422. The steam condensing screwfeeder 402 further comprises a steam inlet 406 in a second end indicated by 407, a feedingscrew 408 for feeding said bulk material from said first end 405 to said second end 407, aninner housing 409 enclosing said feeding screw 408, said inner housing is preferablycylindrically formed and having in inner wall. Said inner housing provides a significant gapbetween the feeding screw 408 and the inside of said inner wall to allow for the wet bulkmaterial to be conditioned. Flash and leakage steam 104 is supplied counter currently to thedirection of movement of the bulk material 101. Flash and leakage steam is supplied to thesteam inlet 406 via the flash and leakage steam conduit 403 from the outlet feeding device 141 of the pneumatic steam dryer.By feeding the flash and leakage steam counter currently to the direction of the movement ofthe bulk material the advantageous effect of deaeration of the bulk material is achieved. The efficiency in following step of dewatering in the plug screw feeder is thereby improved.

The inlet feeding device 401 comprises a plug screw feeder. The object of the plug screw W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_085750_PRVFiling.doc 17 feeder is to feed the bulk material from an atmospheric environment outside the pneumaticsteam dryer via the bulk material inlet 130 into the pressurized environment of said dryer withmarginal leakage of pressurized steam. The plug screw feeder 401 receives conditioned bulkmaterial from the steam condensing screw feeder 402. Said plug screw feeder 401comprises preferably dewatering means for dewatering the bulk material. Plug screwfeeders with dewatering means are previously known and typically comprises a conicallyshaped rotating plug feeding screw 412 for feeding said bulk material from a first endindicated by 410 to a second end indicated by 411 and an inner housing enclosing said plugfeeding screw 412. The inner housing comprises a conically tapered inner wall comprisingpassages such as channels and/or orifices in said inner wall for draining of fluids. The plugfeeding screw 412 cooperates with said inner wall to mechanically compress said bulkmaterial located between the feeding screw and the inside of the conically tapered wall to form a plug of bulk material 101 and to extract fluids from the material.

The wet bulk material 101 is fed from the container 421 into said first end 405 of the bulkmaterial conditioning device 402. Flash and leakage steam 104 is fed into the said secondend 407 of the steam condensing screw feeder 402. Flash and leakage steam is suppliedcounter currently to the direction of movement of said bulk material. Flash and leakagesteam is condensed into the bulk material whereby the bulk material is conditioned. The bulkmaterial is there after fed into the plug screw feeder 401. The bulk material is slightlydewatered in the plug screw feeder and thereafter fed into the pneumatic steam dryer. ln this embodíment of the invention said flash and leakage steam is utilized for conditioningthe wet bulk material and recovered by condensing the flash and leakage steam into the bulkmaterial. The bulk material conditioning device is followed by an inlet feeding device wherein the bulk material is further compressed and dewatered.

The flash and leakage steam conditions the wet bulk material in the steam condensing screwfeeder which improves the efficiency of the dewatering operation in the following plug screwfeeder. This has the functional benefit that an amount of liquid is pressed out of the bulkmaterial already before the drying process in the pneumatic steam dryer.

This provides the effect that a significant amount of waste substances such as chlorine andalcalic substances originating from the wet bulk material is removed already before the bulkmaterial is fed into the pneumatic steam dryer. Costly devices and processes for taking careof these substances at a later process step are thereby avoided and furthermore the bulkmaterial is significantly drier already before the pneumatic steam dryer. This also provides fordrying of low quality feedstock which typically contains a larger proportion of waste W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_O85750_PRVFiling.doc 18 substances by the pneumatic steam dryer.

Since flash and leakage steam is a low cost steam source it is particularly suitable to use forConditioning purposes. Moreover, the dewatering operation is proven to be very effectivewhen the temperature of the conditioned bulk material is approximately 80 °C. The flash andleakage steam is therefore particularly suitable to be used in the conditioning operation. Theconditioning operation is of great importance especially when the wet bulk material is of a low temperature or even frozen.

Another advantage with utilizing flash and leakage steam as conditioning medium is that theflash and leakage steam already contains some waste substances from the drying process,which makes the flash and leakage steam particularly suitable instead of using other cleaner resources which are more expensive.

Third embodiment Fig. 3 shows a third embodiment of the system according to the invention which comprises apneumatic steam dryer 100 (previously described) and a bulk material handling system 200”connected to a bulk material inlet of said pneumatic steam dryer 100 and to the bulk materialoutlet 140 of said pneumatic steam dryer.

This embodiment comprises the previously described pneumatic steam dryer 100 and thedrying process carried out by said pneumatic steam dryer which is therefore not further described here. Furthermore, in the following like references are used for like features.

The process according to this embodiment of the invention comprises utilizing of said flashand leakage steam in a bulk material handling system 200” connected to a bulk materialoutlet 140 and connected to a bulk material inlet 130 of said pneumatic steam dryer 100. ln this embodiment of the invention flash and leakage steam is utilized in a bulk materialhandling system 200" comprising a controlling section 300 connected to said bulk materialoutlet 140 of said pneumatic steam dryer and a conditioning section 400 connected to saidbulk material inlet 130 of said pneumatic steam dryer.

All features and alternative Variations previously described in the separate first and second embodiments of the invention are combinable with corresponding effects. This means that the controlling section 300 and the conditioning section 400 are separately and W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_085750_PRVFiling.doc 19 independently implemented to the same pneumatic steam dryer 100, providing the same effects and beneficial functions as previously described.

More preferably the process according to this embodiment of the invention comprisesutilizing said flash and leakage steam sequentially by first the controlling section 300 andthereafter by the conditioning section 400. Advantageously the process comprises supplyingflash and leakage steam from said controlling section to said conditioning section.

Most preferably comprises the process supplying of the flash and leakage steam from saidmilling means 340 in said controlling section to said steam condensing screw feeder 402 in said conditioning section via a milling loop 500. ln Fig. 3 the third embodiment of the system according to the present invention is shownwhich comprises a bulk material handling system 200" for utilizing flash and leakage steamwhich comprises a controlling section 300 connected to said bulk material outlet 140 and aconditioning section 400 connected to said bulk material inlet 130 of said pneumatic steamdryer 100.

The conditioning section 400 is connected to said controlling section 300 to receive said flashand leakage steam 104 from said controlling section. Said controlling section 300 ispreviously described in the first embodiment of the present invention and said conditioning section 400 is previously described in the second embodiment of the present invention.

Said controlling section comprises a first classifier 310 for classifying said bulk material intoat least a first fraction and a second fraction and milling means 340 for disintegrating saidfirst fraction. A second classifier 320 classifies said second fraction into a third and a fourthfraction as previously described. Said controlling section forms a loop wherein flash andleakage steam is circulated by a fan 370. A pellet press 350 is connected to said second classifier to pelletize said third fraction.

Said conditioning section 400 comprises a bulk material conditioning device 402 and an inletfeeding device 401. As previously described comprises the bulk material conditioning device preferably a steam condensing screw or a rotating tumbler.

Fig. 3 shows further the bulk material conditioning device, the steam condensing screwfeeder 402 in the conditioning section 400 connected to the controlling section 300. Flashand leakage steam 104 is supplied via milling means 340 and a third separating means 510to the steam condensing screw feeder. Furthermore, the disintegrated bulk material W:\lnproteCh_Cased0cuments\Patent\P40901194SE00_20091217_085750_PRVFi|lng.d0C obtained by milling is also supplied to the Conditioning section 400.

Fig. 3 shows further the steam condensing screw feeder 402 connected to the controllingsection 300, preferably via the milling means 340 to receive said flash and leakage steam104. ln addition to the controlling section and the conditioning section provides this embodiment a milling loop 500, which connects the controlling section and the conditioning section together.

Said milling loop comprises said milling means 340, a third separating means 510 and a fan.The disintegrated bulk material obtained by milling is pneumatically conveyed with flash andleakage steam to said third separating means 510 and thereafter fed to the conditioningsection 400. Thus said bulk material conditioning device, the steam condensing screw feeder402 is connected to said milling means 340 to receive disintegrated bulk material obtained bymilling.

A first partial flow of the flash and leakage steam separated in the separating means 510 isfed to the bulk material conditioning device 402, and a second partial flow of flash andleakage steam is returned to the milling means 340.

This has the further advantage that the pressure in the controlling section can be maintainedby releasing said flash and leakage steam into the milling loop and thereafter into theconditioning section.

Said third separating means 510 is preferably a cyclone which separates the disintegratedbulk material from the flash and leakage steam and supplies the material into the bulkmaterial conditioning device 402. The flash and leakage steam is supplied to the bulkmaterial conditioning device via flash and leakage steam conduit 404 for conditioning of the bulk material in the same manner as previously described.

The utilizing of flash and leakage steam in said bulk material handling system 200” hasseveral functional benefits. The flash and leakage steam is sequentially used in thecontrolling section and the conditioning section. A safe environment inside the controllingsection is achieved. Energy efficiency is achieved by using the heat of the ﬂash and leakagesteam to keep the bulk material warm thereby improving the milling operation and thepelleting operation and to heat the wet bulk material in the bulk material conditioning device.

Furthermore, environmental benefits are achieved by the dewatering operation.

The connection between the milling means and the bulk material conditioning device has the W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_085750_PRVFiling.doc 21 further effect that bulk material suspended in flash and leakage steam can be conveyed from the milling means to the bulk material Conditioning device by pneumatic transport.

The invention has mainly been described above with reference to a few embodiments.However, as readily appreciated by a person skilled in the art, other embodiments than theones disclosed above are equally possible within the scope of the invention, as defined buthe appended patent claims.

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Claims

22 Claims

1. Process for treating bulk material comprising -feeding bulk material by an inlet feeding device (131 ,401) into a steam filled circulationconduit (105) of a pneumatic steam dryer (100) operating above atmospheric pressure -heating said steam by heating means(121), -drying said bulk material in a drying conduit (111) by heat transfer from said steam therebyforming surplus steam, -separating said bulk material from said steam by a first separating means (150),-pneumatically conveying said bulk material suspended in said steam through said dryingconduit from said inlet feeding device (131,401) to said first separating means (150),-releasing surplus steam from said circulation conduit (105), -discharging said bulk material by an outlet feeding device (141) from said pneumatic steamdryer thereby generating flash and leakage steam, wherein said process is characterized in utilizing said flash and leakage steam in a bulk material handling system(200;200';200")connected to said pneumatic steam dryer(100).

2. A process according to claim 1 comprising utilizing said flash and leakage steam in a bulkmaterial handling system (200;200';200")connected to a bulk material outlet (140) of said pneumatic steam dryer (100).

3. A process according to claim 1 or 2 comprising receiving said flash and leakage steamand bulk material by said bulk material handling system (200;200") from said outlet feedingdevice (141) and controlling of said bulk material by a controlling section(300).

4. A process according to claim 3 comprising pneumatically conveying said flash andleakage steam through said controlling section (300) thereby forming an substantially oxygen free environment inside said controlling section.

5. A process according to claim 3 or 4 comprising classifying of said bulk material into atleast a first fraction and a second fraction by a first classifier (310) in said controlling section (300).

6. A process according to claim 5 comprising disintegrating of said first fraction by millingmeans (340) in said controlling section. WI\|npr0tech_Cased0cuments\Patent\P40901194SEO0_20091217_085750_PRVFiling.d0c 23

7. A process according to claim 5 or 6 comprising classifying of said second fraction by asecond classifier (320) into a third fraction and a fourth fraction in said controlling section.

8. A process according to one or more of claims 5-7 comprising classifying said bulk materialby mechanical separation in said first classifier (310).

9. A process according to one or more of claims 5-8 comprising classifying said bulk material by aerodynamic Classification in said first classifier (31 O).

10. A process according to one or more of claims 5-9 comprising classifying said bulk material by aerodynamic Classification in said second classifier (320).

11. A process according to one or more of claims 5-10 comprising pelleting said secondfraction or said third fraction into fuel pellets by a pelleting press (350) connected into said controlling section (300).

12. A process according to one or more of claims 5-10 comprising mixing of said secondfraction or said third fraction with granulate formed thermoplastic material and extruding said mixture by a pelleting press (350).

13. A process according to one or more of claims 6-12 comprising supplying disintegratedbulk material obtained from said milling means (340) to said inlet feeding device (131;401)and feeding said disintegrated bulk material into said circulation conduit (105) of said pneumatic steam dryer.

14. A process according to one or more of the preceding claims comprising utilizing saidflash and leakage steam by a bulk material handling system (200';200") connected to a bulkmaterial inlet (130) of said pneumatic steam dryer (100).

15. A process according to one or more of the preceding claims comprising utilizing saidflash and leakage steam to condition bulk material in a Conditioning section (400) of said bulkmaterial handling system (200';200").

16. A process according to one or more of the preceding claims comprising supplying said flash and leakage steam to said Conditioning section (400) from said outlet feeding device (141) of said pneumatic steam dryer. W:\lnprotech_Casedocuments\Patent\P40901194SE00_20091217_O85750_PRVFiling.doc 24

17. A process according to one or more of the preceding claims wherein said conditioningcomprises condensing said flash and leakage steam in said bulk material in a bulk material Conditioning device (402).

18. A process according to one or more of the preceding claims comprising dewatering ofsaid bulk material by said inlet device (401) in advance of feeding the bulk material into the pneumatic steam dryer (100).

19. A process according to one or more of the preceding claims comprising utilizing saidflash and leakage steam in a bulk material handling system (200") connected to a bulkmaterial outlet (140) and connected to a bulk material inlet (130) of said pneumatic steam dryer.

20. A process according to one or more of the preceding claims comprising utilizing saidflash and leakage steam by first said controlling section (300) and thereafter by said conditioning section (400).

21. A system for treating bulk material, said system comprising a pneumatic steam dryer(100) being adapted to operate above atmospheric pressure, said pneumatic steam dryer (100) comprising -a circulation conduit (105) which in operation of the pneumatic steam dryer is filled withsteam, -heating means (121) connected into said circulation conduit (105) for heating said steam,-an inlet feeding device (131 ;401) connected to said circulation conduit for feeding bulkmaterial into said circulation conduit (105), -a drying conduit (111) connected into said circulation conduit (105) wherein said bulkmaterial is dried by heat transfer from said steam thereby forming surplus steam, -first separating means (150) connected to said drying conduit (111) for separating said bulkmaterial from said steam, -a fan (160) connected into said circulation conduit (150) for pneumatically conveying saidbulk material suspended in said steam through said drying conduit (111) from said inletfeeding device (131;401) to said first separating means (150), - a surplus steam outlet (170) connected to said circulation conduit (105) for releasingsurplus steam from said circulation conduit, - an outlet feeding device (141) for discharging said bulk material from said pneumatic steam dryer (100) thereby generating flash and leakage steam, W:\lnprotech_Casedocuments\Patent\P40901194SEO0_20091217_085750_PRVFiling.doc characterized in that-a bulk material handling system (200;200';200“) is connected to said pneumatic steam dryer (100) for utilizing said flash and leakage steam.

22. A system according to claim 21 wherein said bulk material handling system(200;200';200") is connected to a bulk material outlet (140) of said pneumatic steamdryer(100).

23. A system according to claim 21 or 22 wherein said bulk material handling system(200;200") comprises a controlling section (400) connected to said outlet feeding device (141) for receiving said bulk material and said flash and leakage steam.

24. A system according to claim 23 wherein said controlling section comprises a firstclassifier (310) connected to said outlet feeding device (141 ) to receive and classify said bulk material into at least a first fraction and a second fraction.

25. A system according to claim 24 wherein said controlling section (400) comprises a millingmeans (350) connected to said first classifier (310) to receive and disintegrate said first fraction.

26. A system according to any of claims 24 or 25 wherein said controlling section (400)comprises a second classifier (320) connected to said first classifier (310) to receive saidsecond fraction and to further classify said second fraction into a third fraction and a fourth fraction.

27. A system according to one or more of the claims 24-26 wherein said first classifier (310) comprises a mechanical separation device.

28. A system according to one or more of the claims 24-26 wherein said first classifier( 310) comprises an aerodynamic classifier.

29. A system according to one or more of the claims 26-28 wherein said second classifier (320) comprises an aerodynamic classifier.

30. A system according to one or more of the claims 28-29 wherein said aerodynamic classifier (310; 320) comprises a rotary aerodynamic classifier. W:\| nprotech_Casedocuments\Pate nt\P40901 194SEOO_20091217_085750_PRVFiling.doc 26

31. A system according to one or more of the claims 26-30 comprising a pellet press (350) connected to said second classifier (320) to receive and pelletize said third fraction.

32. A system according to one or more of the claims 31-32 wherein said pellet press(350;350') comprises a roller-and-ring press or an extruder.

33. A system according to one or more of the claims 23-32 wherein said controlling section (300) is adapted to operate near atmospheric pressure.

34. A system according to one or more of the claims 21-33 wherein said bulk materialhandling system (200';200") is connected to a bulk material inlet (130) of said pneumatic steam dryer.

35. A system according to one or more of the claims 21-34 wherein said bulk materialhandling system (200';200") comprises a conditioning section (400) connected to said bulk material inlet (130) of said pneumatic steam dryer (100).

36. A system according to one or more of the claims 21-35 wherein said conditioning section(400) is connected to said bulk material outlet (140) of said pneumatic steam dryer (100) to receive flash and leakage steam.

37. A system according to one or more of the claims 21-36 wherein said conditioning section comprises a bulk material conditioning device (402) and an inlet feeding device (401).

38. A system according to one or more of the claims 21-37 wherein said inlet feeding device (131; 401) comprises a plug screw feeder.

39. A system according to one or more of the claims 21-38 wherein said bulk material conditioning device (402) comprises a steam condensing screw feeder.

40. A system according to one or more of the claims 21-39 wherein said bulk materialhandling system (200") comprises a controlling section (300) connected to said bulk materialoutlet (140) and a conditioning section (400) connected to said bulk material inlet (130) of said pneumatic steam dryer (100).

41. A system according to one or more of the claims 21-40 wherein said conditioning section (400) is connected to said controlling section (300) to receive said flash and leakage steam W:\lnprotech_Casedocuments\Patent\P40901 194SE00_20091217_085750_PRVFiling.doc 27from said controlling section.

42. The system of one or more of the claims 21-41 wherein said bulk material Conditioning device (402) is connected to said milling means (340) to receive disintegrated bulk material obtained by milling. W:\|nprotech_Casedocuments\Patent\P40901194SEO0_20091217_085750_PRVFiling.doc