(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date WO 2013/174828 Al 28 November 2013 (28.11.2013) WIP01 POT (51) International Patent Classification: CL, CN, CO, CR, CU, CZ, DE, DK, DM, DO, DZ, EC, F26B 1/0 (2006.01) EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, YN, KP, KR, KZ, (21) International Application Number: PCT/EP2013/060437 LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, (22) International Filing Date: 22 May 2013 (22.05.2013) OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SC, SD, SE, SG, SK, SL, SM, ST SV, SY, TH, TJ, TM, (25) Filing Language: German TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. (26) Publication Language: German (84) Designated states (unless otherwise indicated, for evety (30) Priority Data: kind qf regional protection available): ARIPO (BW, GH, 10 2012010 078.7 23 May 2012 (23.05.2012) DE GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, (71) Applicant: RWE POWER AKTIENGESELLSCHAFT TM), European (AL, Ax, BE, BG, CHI, CY, CZ, DE, DK, [DE/DE}; Huyssenallee 2,45128 Essen (DE). EE, ES, Fl, FR, GB, GR, HR, HU, lE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, (72) Inventor: ILUTZ, Hans-Joachim; Otterdriesch 13, 50374 SM, TR), OAPI (BF, BI, CF, CG, CI, CM, GA, ON, GQ, Erftstadt (DE), GW, ML, MR, NE, SN, TD, TG). (74) Agent: KIERDORF, Theodor; Polypatent, Sattlerweg 14, Published: 51429 Bergisch Gladbach (D), - with international search report (Article 21(3)) - before the expiration of the time limit jbr amending the (81) Designated states (unless otherwise indicated, for every kind claims and to be republished in the event of receipt of ofnationalprotection available): AE, AG, AL, AM, AO, AT, amendments (Rule 48.2(h)) AU, AZ, BA, BB, BC, BH. BN, BR., BW, BY. BZ, CA, CH, As printed (54) Title: METHOD FOR PROCESSING PIT-MOIST RAW BROWN COAL (54) Bezeiclmung : VERFAHREN ZUR AUFBEREITUNG VON G3RUIBBNFEUCIHTER ROHBRAUNKOHLE 2 .2Qk . X E3 6 (57) Abstract: The invention relates to a method for processing pit-moist raw brown coal in particular for the thermal utilization in a power plant boiler. The raw brown coal is first precrushed and then comminuted in at least one milling appliance (2) and also fed to dowstream drying. The drying proceeds in a fluidized bed using an indirectly heated fluidized-bed dryer (3). Some of the dry brown coal taken off from the fluidized-bed dryer (3) is branched off and added back to the raw brown coal before the drying, as a result of which the fluidizability of the brown coal is improved. (57) Zusammenfassung: WO 2013/174828 Al Die Erfin=g betuifl ein Verfabren zur Aufbereitung von gmbenfeuchier Rohbraunkohle, insbesondere zur thennischen Verwertung in einem Kraftverkskessel, Die Rohbraunkohle wird zuniichst vorgebrochen nid anschlieBend in wenigstcns einer Mahleinrichtung (2) zerkleinert sowie einer nachgeschaitcten Trocknung zugefihrt. Die Trocknung erfolgt in einer Wirbelsohicht hunter Verwendung eines indirekt beheizten Witbelsehichttrockners (3), Ein Teil der aus dem Wirbelschichttrockner (hbeezonenen Tmekenbrainkohle wir nhoe7wot nnd Aer -nhhrnnnlmhiavr, A-r Tr-1mn-n ,-- -nA.- ., .. 3-n.
WO 2013/174828 - 1 - PCT/EP2013/060437 Method for processing pit-moist raw brown coal The invention relates to a process for the beneficiation of pit-moist raw brown coal, in 5 particular for thermal utilization in a power station boiler, wherein the raw brown coal is firstly precrushed and subsequently comminuted in at least one milling apparatus and passed to subsequent drying and the drying is carried out in a fluidized bed using at 10 least one indirectly heated f luidized-bed dryer which is operated using steam as fluidization medium. A process for drying water-containing brown coal in a fluidized bed is known, for example, from 15 DE 29 01 723 C2. In the fluidized-bed drying process described there, the feed coal is introduced by means of a screw conveyor into the fluidized-bed dryer. 20 The process known from the abovementioned document is said to be suitable for drying lumpy materials having a size in the range from, for example, 0.3 cm to 10 cm. For this purpose, the material to be dried, for example 25 brown coal, is fluidized in a denser material such as silica sand. The process requires that the dried solid material is removed together with part of the particulate fluidizable material and that the solid material and the fluidizable material are separated 30 from one another so that the fluidizable material separated off is returned to the fluidized bed. The process is complicated and cannot be readily implemented in industry. 35 Another process for drying brown coal, in particular for use in a power station boiler, is known from, for example, DE 196 20 047 Al. This process is operated WO 2013/174828 - 2 - PCT/EP2013/060437 using exclusively brown coal as solid and steam as fluidizing medium. The brown coal to be introduced into the dryer is comparatively finely milled, for example to an average particle diameter dse of about 1 mm, to 5 enable it to be fluidized in the fluidized bed. Depending on the nature of the brown coal, such a fluidized-bed drying process can proceed relatively stably and in a problem-free manner in a steady-state 10 fluidized bed. As has already been described in DE 29 01 723 C2, this depends essentially on the fluidizability of the solid in the fluidized-bed dryer. The hydromechanical 15 processes within a steady-state fluidized bed are extremely complex and can be simulated to only a limited extent. In a pilot plant operated by the applicant, disturbances in the mixing dynamics have been found from time to time, depending on the mass 20 flow to be introduced. As a result of such disturbances, deposits of raw brown coal are preferentially formed on the heat exchangers of the fluidized-bed dryer. As a result, heat transfer is impaired, the performance of the dryer decreases 25 significantly and in the worst case the fluidized bed collapses. Experiments using fluidized-bed dryers at a variety of throughputs have shown that the fluidizability of raw 30 brown coal depends not only on the loading of the fluidized-bed dryer as a proportion of the capacity but also on the type and composition of the raw brown coal. It is therefore an object of the invention to provide a 35 process for the beneficiation of pit-moist raw brown coal using at least one indirectly heated fluidized-bed dryer which ensures essentially stable and disturbance free fluidized bed operation even at a high throughput WO 2013/174828 - 3 - PCT/EP2013/060437 and for a variety of feed coals. The object of the invention is achieved by a process for the beneficiation of pit-moist raw brown coal, in 5 particular for thermal utilization in a power station boiler, wherein the raw brown coal is firstly precrushed and subsequently comminuted in at least one milling apparatus and passed to subsequent drying, where the drying is carried out in a fluidized bed 10 using at least one indirectly heated fluidized-bed dryer which is operated using steam as fluidization medium, where the raw brown coal is introduced as bulk material having an average particle diameter d 5 e of not more than 2 mm into the fluidized bed and a substream 15 is branched off from the dried brown coal downstream of the fluidized-bed dryer and mixed into the raw brown coal before drying. The particle size distribution can be ensured, for 20 example, by variation of the speed of rotation of one or more of the mills located upstream of the fluidized bed dryer. Mills employed are, for example, beater mills which achieve a different milling fineness as a function of the speed of rotation. The particle size 25 distribution is checked by sieving and sampling can for this purpose be provided daily or even per batch. The samples are monitored in the laboratory by sieve classification. As an alternative, the particle size distribution can also be measured volumetrically by 30 means of an on-line method. To achieve stability of the fluidized bed, it is, first and foremost, important that the proportion of oversize particles (> 2 mm) is not too great since this could 35 otherwise adversely affect the stability of the fluidized bed. The particle size distribution can, as an alternative, WO 2013/174828 - 4 - PCT/EP2013/060437 also be ensured by milling of the dried brown coal being followed by sieve classification, with the oversize particles being sieved out and subjected to after-milling. 5 The invention is based on the recognition that pit moist raw brown coal has different cohesive behavior depending on its origin, and this has a more or less large influence on the fluidizability of the coal. 10 It is known that raw brown coal, as natural product obtained by mining, differs in respect of water content, proportion of carbon and mineral composition depending on its origin. Particular properties of the 15 raw brown coal have to be accepted in use. The applicant was able to discover experimentally that the fluidizability of the raw brown coal is closely related to its flowability and that the flowability of 20 the raw brown coal can surprisingly be positively influenced by mixing in dry brown coal of the same type. According to the invention, the same type of coal in 25 the form of dry brown coal is accordingly added to the raw brown coal to be dried before the drying operation. The stability of the beneficiation process of the invention, in particular the stability of the fluidized 30 bed within the fluidized-bed dryer, can surprisingly be improved by part of the dried brown coal being circulated within the process, so that even raw brown coal which is difficult to fluidize or cannot be fluidized can in this way be used and dried without 35 problems with at the same time a comparatively high throughput through the fluidized-bed dryer. The problem of fluidizability of the fluidized bed also WO 2013/174828 - 5 - PCT/EP2013/060437 depends on the loading of the fluidized-bed dryer as a proportion of capacity. Disturbances in the fluidized bed can, in particular, occur at a high loading of the fluidized-bed dryer as a proportion of capacity. 5 The mixture of raw brown coal and recirculated dry brown coal is, in the process of the invention, preferably fed via a star feeder into the fluidized-bed dryer which is under slightly superatmospheric 10 pressure, introduced above the fluidized bed and distributed over the fluidized bed. Particular preference is given to mixing a proportion of dry brown coal of from 10 to 30% by mass, preferably 15 from 10 to 20% by mass, based on the total bed, into the raw brown coal. The proportion of recirculated dry brown coal is advantageously regulated as a function of the amount of 20 raw brown coal introduced into the fluidized bed. Regulation can be effected by setting a particular ratio of dry brown coal to raw brown coal and metering in the dry brown coal accordingly. Depending on the plant loading set, the amount of recirculated dry brown 25 coal can automatically be adapted at a constant ratio. For the purposes of the present patent application, regulation is automatic regulation for which appropriate process control instrumentation is 30 provided. The raw brown coal can have a fluctuating water content/moisture content of up to 65- by mass. The water content of the dry brown coal taken off from the 35 fluidized-bed dryer is determined in the hygroscopic range at constant system pressure by means of the fluidized-bed temperature or the course of the desorption isobars. The dry brown coal taken off from WO 2013/174828 - 6 - PCT/EP2013/060437 the fluidized-bed dryer can have an average particle diameter do of from 0.4 mm to 0.8 mm, preferably from 0.1 mm to 0.4 mm, possibly also from 0.1 mm to 0.2 mm. The moisture content of the dry brown coal can be in 5 the range from 10%- by mass to 15% by mass, preferably about 15%- by mass - 18%- by mass. The gauge pressure within the fluidized-bed dryer can be up to 10 bar. The moisture content of the dry brown coal can also be in the range from 8 to 20%- by mass, preferably from 10 to 10 16% by mass. As mentioned above, the fluidized-bed dryer is preferably indirectly heated by means of steam as heating medium. Part of the vapor from the dryer or 15 alternatively external steam from a coupled power station process can be used for fluidizing the fluidized bed or the raw brown coal within the fluidized-bed dryer. 20 The dry brown coal which has been branched off can be intimately mixed with the raw brown coal using at least one mixing apparatus before introduction into the fluidized-bed dryer. Such mixing is not necessary under all circumstances, but significantly improves the 25 adhesion of fine dry coal particles to the particles of the moist raw brown coal used. For example, the dry brown coal can be cooled downstream of the fluidized-bed dryer and subjected to 30 after-milling, with a substream of dry brown coal being branched of f downstream of after-milling. It is of course also possible to branch off the dry brown coal to be recirculated directly downstream of 35 the fluidized-bed dryer, but cooling and after-milling is more advantageous, so that, for example, the dry brown coal having an average particle size dso of from 0 mm to 1 mm is added to the raw brown coal. The WO 2013/174828 - 7 - PCT/EP2013/060437 particle size distribution can likewise be determined volumetrically by sieve classification, and the after milling can be carried out accordingly in the case of a deviating particle size distribution. 5 The recirculated dry brown coal can be mixed into the raw brown coal between two milling stages or downstream of a last milling stage. Of course, it is also possible to add the recirculated dry brown coal to the raw brown 10 coal before a first milling. In this case, intimate mixing is ensured simply by joint milling of raw brown coal and dry brown coal, so that separate mixing apparatuses may be dispensable. 15 However, for a relatively effective and energy efficient process, it is good practice to circulate as little as possible dry brown coal and to keep the path of the dry brown coal to be recirculated or conveyed concomitantly as short as possible. However, the point 20 of view of explosion protection should also be taken into account. For the latter reason, it is advantageous and sensible to add the recirculated dry brown coal to the raw brown coal downstream of fine milling of the raw brown coal and carry out mixing with the raw brown 25 coal, for example by means of static or dynamic mixing apparatuses, in the feed line to the fluidized-bed dryer. Mixing can, for example, also be carried out via a conventional transport apparatus. 30 It is advantageous for the proportion of dry brown coal mixed into the raw brown coal to be varied as a function of the adhesion properties of the raw brown coal and/or the loading state of the fluidized-bed dryer. As will be again stated below, it has been found 35 that the flow properties and the adhesion properties of raw brown coal depend to a significant extent on the compressibility of the raw brown coal and thus on the bulk density of the raw brown coal in the compacted WO 2013/174828 - 8 - PCT/EP2013/060437 state. The pouring of the raw brown coal into the f luidized bed is advantageously carried out by means of at least 5 one rotating distributor chute arranged above the fluidized bed, preferably according to a prescribed distribution based on the cross-sectional area of the fluidized-bed dryer. 10 The invention is illustrated below with reference to the accompanying drawings. The figures show: 15 figure 1: a schematic depiction of the process principle of the beneficiation process according to the invention, and figure 2: a graph in which the bulk material strength 20 of materials of differing flowability is shown as a function of the consolidation stress. Reference will firstly be made to the process principle 25 depicted in figure 1, which illustrates the flow diagram of a fluidized-bed drying plant which can be connected, for example, to a power station boiler for firing with brown coal. 30 From an open-cast brown coal mine, precrushed raw brown coal having an average particle size of from 0 mm to 80 mm is, for example, fed into a raw brown coal hopper 1. From the raw brown coal hopper 1, the raw brown coal is finely milled to an average particle size (dso) of 35 about 0 mm - 2 mm in two mills arranged in series. The raw brown coal is then mixed with dry brown coal, as described further below, and introduced into a fluidized-bed dryer 3. The fluidized-bed dryer 3 is, WO 2013/174828 - 9 - PCT/EP2013/060437 for example, heated indirectly by means of steam via appropriate heat-exchange internals. The steam feed to supply the heat exchanger is denoted by the reference symbol 4 in the process diagram (fig. 1). The 5 fluidized-bed dryer 3 is operated in a known way under slightly superatmospheric pressure, with the raw brown coal being introduced into the fluidized bed via a star feeder which is not shown and via a distributor chute arranged in the upper part of the fluidized-bed dryer 10 3. The vapor 5 taken off from the fluidized-bed dryer 3 is, after removal of dust in an electrostatic precipitator 6, passed to various other uses. It can, for example, be released into the atmosphere. As an alternative, it can be condensed, with the low 15 temperature heat from the condensation of the vapor being, for example, integrated into the boiler feed water preheating of a power station process. In a further alternative, the vapor can be compressed and fed back into the fluidized-bed dryer 3 for the purpose 20 of heating. The energy from the vapor can also be integrated into an ORC (organic rankine cycle) process. A substream 7 of the vapor 5 is in any case fed as fluidizing medium to the fluidized-bed dryer 3. The dry 25 brown coal 8 taken off from the fluidized-bed dryer 3 is firstly cooled in a cooler 9 and then after-milled in a mill 10 and fed into a dry brown coal silo 11. Possible places for taking dry brown coal off from the brown coal stream intended for thermal utilization are 30 denoted by El to E4, where El denotes an offtake point downstream of the fluidized-bed dryer 3 and upstream of the cooler 9, E2 denotes an offtake point downstream of the cooler 9 and upstream of the mill 10, E3 denotes an of ftake point downstream of a mill 10 and upstream of 35 the dry brown coal silo 11. Finally, E4 denotes an offtake point downstream of the dry brown coal silo 11. The substream of dry brown coal to be recirculated is WO 2013/174828 - 10 - .PCT/EP2013/060437 preferably taken off at E4, since because of the storage provided in the dry brown coal silo 11, better meterability of the substream to be recirculated is ensured. 5 The dry brown coal silo 11 can be provided at the discharge end with a discharge star feeder which can be operated at a variable speed of rotation. The speed of rotation control of the discharge star feeder enables 10 the amount of dry brown coal to be metered so that it is possible to set a ratio of amount of dry brown coal recirculated to the amount of raw brown coal as a function of the cohesivity of the raw brown coal and/or as a function of the load as a proportion of capacity 15 or the load state of the fluidized-bed dryer 3. The dry brown coal silo 11 can have two separate dry brown coal off takes, of which one is provided for dry brown coal recirculation or dry brown coal backmixing while the other is the off take for dry brown coal as usable 20 product of the drying process. The use of two separate offtakes has, in particular, the advantage in terms of regulation that the subsequent transport path can also be used for filling the fluidized-bed dryer 3 with dry brown coal before start-up. Before a first introduction 25 of raw brown coal on start-up of the fluidized-bed dryer 3, it is necessary firstly to build up a fluidized bed by means of dry brown coal 8 since the raw coal is not fluidizable because of its cohesive properties. 30 A further advantage of such an arrangement is that should the raw coal feed fail, dry brown coal recirculation can compensate for the discharge of dust from the fluidized bed and the fluidized bed and all 35 control circuits of the fluidized-bed dryer can continue to be operated normally. The positions Ri to R4 denote possible recirculation WO 2013/174828 - 11 - PCT/EP2013/060437 points for the dry brown coal to be recirculated, where the recirculation point R1 is provided directly downstream of the raw coal hopper 1, the recirculation point R2 is provided between a first mill and a second 5 mill, and the recirculation point R3 is provided downstream of a second mill and upstream of the fluidized-bed dryer 3. The recirculation point R4 is provided directly upstream of the fluidized-bed dryer 3. 10 The applicant has surprisingly found that the flowability of various raw coals is directly related to their fluidizability in the fluidized bed. Mixing dry brown coal into the raw brown coal which is difficult 15 to fluidize enables the flowability of the raw brown coal to be introduced into the drying process to be significantly improved. To demonstrate this relationship, the applicant has 20 examined various raw brown coals from various open-cast mines and also each dry brown coal obtained from these raw coals in respect of their flow properties. The various coal samples, designated below as samples 1 to 5 in the interests of simplicity, and the dry brown 25 coals obtained therefrom, designated below as TBK 1 to TBK 5, were each subjected to flowability tests, with a flowability being determined as ratio of a consolidation stress to a compressive stress. The flowability is given by: 30 ff at to c,-, where ffc is the flowability, o is the consolidation stress and c is the compressive strength. Such a flowability can be determined both by means of the known single-axis pressure test and by means of 35 commercially available ring shear instruments. Such a ring shear instrument is commercially available from, for example, the company Dr. Dietmar Schulze Schnttgutmesstechnik (ring shear instrument ST-XS).
WO 2013/174828 - 12 - PCT/EP2013/060437 Various other types of ring shear instruments are available. The flowability of bulk material can be classified as 5 follows: ffo < I non-flowing 1 < ffc < 2 very cohesive to non-flowing 2 < ffc < 4 cohesive 10 4 < ffa < 10 readily flowing 10 < ffc free-flowing. The bulk material strength ca as a function of the consolidation stress al for regions of different 15 flowability is shown by way of example in figure 2. The samples examined by the applicant were examined at a temperature of about 19 0 C at an atmospheric humidity of about 30% relative humidity. The result of the 20 flowability measurements is shown below in table 1, where ac denotes the bulk material strength or compressive strength of the bulk material after it has been compacted under the stress ol, ffe is the ratio of ai to O, pA in kg/m 3 is the bulk material density, 9, is 25 the measure of the internal friction angle of the bulk material in the case of steady-state flow, Kin is the gradient angle of the linearized flow location approximated as a straight line and 9,f is the internal friction angle in steady-state flow. 30 Table 1: sample Pa-- -- a o [ Paj _f H- pb [kg/M$' % COI Pl~in 10 ____ 1 4020 1703 2.4 530 48 37 40 2 4067 2320 1.s 501 53 36 42 3 3890 1946 2.0 504 49 35 40 4 4443 2007 2.2 554 49 37 42 5 4104 2096 2.0 529 50 35 41 WO 2013/174828 - 13 - PCT/EP2013/060437 TBK from 1 4219 514 8,2 543 41 38 38 TBK from 2 4109 514 8.0 604 44 41 39 TBK from 3 4192 403 104 574 40 38 38 TBK from 4 4022 524 7,7 650 40 37 37 TBK from 5 4243 534 7.9 607 42 39 39 In the case of the raw brown coal samples 1 to 5, the flowability ffe in table 1 is from 1. 8 to 2.4 for the consolidation stress studied. The samples without 5 influence of consolidation over time can thus be classified as cohesive to very cohesive. The most unfavorable flowability is in the case of sample 2, while the most favorable flowability is obtained for sample 1: based on the bulk material strength oc of 10 sample 1, sample 2 has a strength which is greater by 1/3. As regards the dry brown coal, samples 6 to 10, the flowability of the dry brown coal is significantly 15 better than that of the raw brown coal. The raw brown coal sample 2 displays the most unfavorable flow properties. Various proportions of the dry brown coal TBK 2 (dry brown coal from sample 2) 20 were then mixed in proportions by weight of 5%, 10%, 15% and 20% into the raw brown coal sample 2. The mixture was then examined to determine its flowability, and the measurement result is shown in table 2. 25 Table 2:_ _ Proportion u., [Pa"' C;.'aj [Pa1 C . _L_____ 10 or'-' of TBK 0 4067 2320 1.8 5 01 53 36 42 5% 3780 2148 1.8 502 5_ _ 33 39 10% 3935 923 2.0 511 48 33 39 15% 3780 1650 2.3 519 47 35 38 WO 2013/174828 - 14 - PCT/EP2013/060437 20% 3758 1356 2,8 523 43 33 37 100% 4109 514 8.0 604 44 4 39 The bulk density was determined both in the uncompacted loose state and after consolidation under a stress of about 4 kPa (values from table 1) . The bulk density 5 both in the uncompacted state and in the consolidated state of the sample is shown in table 3 below both for the samDles I to 5 and for the samples TBK 1 to TEK 5 and also for various mixtures. 10 WO 2013/174828 - 15 - PCT/EP2013/060437 Table 3: Sample Bulk density Pb Ekg/m 3 1 at a consolidation stress of -> 0 kPa approx. 4 kPa 1 _433 530 2 380 501 3 410 504 4 1467 554 5 1447 529 TBK from 1 1453 453 TBK from 2 1603 604 TBK from 3 574 574 TBK from 4 640 _ _ 650 ........ TBK from 5 604 607 2 + 0% of TBK 380 501 2 + 59 of TBK 380 502 2 + 10% of TBK 400 1511 2 + 15% of TBK 410 1519 2 + 20% of TBK 429 523 100% of TBK 603 604 Sample 2 has a particularly low bulk density. This corresponds with the unfavorable flowability for this 5 sample, as is indicated in table 1- If a bulk material has an unfavorable flowability, the individual particles are not mobile in the bed, so that voids remain and the bulk density is low. As a consequence, the samples are compressible and the bulk density 10 therefore depends on the stress applied. The greatest compressibility is likewise found in the case of sample 2. The dry brown coals also differ appreciably in terms of 15 the bulk density. However, no relationship is found between the raw brown coals and the dry brown coals: a WO 2013/174828 - 16 - PCT/EP2013/060437 low bulk density of the raw brown coal does not necessarily mean a low bulk density of the dry brown coal. The dry brown coals are only very slightly to measurably compressible in the consolidation stress 5 range studied. Both the uncompacted bulk density and the bulk density under a consolidation stress of about 4 kPa increase with increasing proportion of dry brown coal. This can 10 be explained by the better flowability after addition of the dry brown coal in that a more f avorable flowability allows closer packing with a smaller proportion of voids and thus a higher bulk density. 15 In conclusion, it can be said that mixing in of dry brown coal, for example into sample 2, has a favorable effect on the flowability of the mixture.
WO 2013/174828 - 17 - PCT/EP2013/060437 Reference symbols 1 Raw brown coal hopper 2 Mills 3 Fluidized-bed dryer 4 Steam feed 5 Vapor 6 Electrostatic filter 7 Substream of the vapor 8 Dry brown coal 9 Cooler 10 Mill 11 Dry brown coal silo El - E4 Offtake points for dry brown coal R1 - R4 Recycle points for dry brown coal