CA1285388C - Production of hardened coal agglomerates - Google Patents

Abstract

Abstract:
A system for the production of hardened coal agglomerates comprising a first pump for pumping a coal-water slurry and a predetermined quantity of oil or other suitable hydrophobic liquid into an agitated mixing tank, a second pump for pumping the coal-water slurry and partially formed agglomerates from the first mixing tank into a pipeline loop which returns the slurry/agglomerates to the tank, a third pump for removing slurry/agglomerates from the first mixing tank and transporting it to a second mixing tank, means for introducing further fresh coal-water slurry into the inlet of the third pump and/or into the second mixing tank, a fourth pump for withdrawing the slurry/agglomerates from the second mixing tank and transporting the mixture through a second pipeline loop which discharges back into the second mixing tank, and a fifth pump for withdrawing the slurry/agglomerates from the second mixing tank for a recovery of the agglomerates by means of a screen or the like.

Description

- l -PRODUCTION OF HARDENED COAL AGGLOMERATES

2 Field of the Invention 3 This invention relates to improvements in the 4 production of coal agglomerates which are suited to long-term storage and/or transportation in the agglomerate form.
6 Back~round of the Invent1on 7 The formation of coal agglomerates from aqueous 8 slurries containing particulate coal and oil has been widely 9 practiced for many years. Many agglomeration processes have been proposed requiring varying degrees of energy input and 11 oil consumption. Most processes having acceptable energy 12 input requirements and residence times produce relatively 13 oily or sticky coal agglomerates which, while being suitable 14 as as a feed stock for the immediate production of a coal-oil mixture, have been found to be unsuitable for long-term 16 storage or transportation due to their stickiness and/or 17 poor physical strength.
18 Examples of prior art agglomeration processes may be 19 found in United States Patents Nos.4355999 Maso~ogites, 4302211 Verschun and Australian Patent 534563 (AU-B
21 54496/80) Dudt. In each of the above processes, long 22 residence times and/or multiple agglomeration stages are 23 required to achieve an acceptable coal agglomerate and even 24 then such products are not necessarily suited to transportation in large bulk carriers of the type which 26 would make transportation of such agglomerates economically 27 viable. In the case of AU-B 54496/80, it will be noted that 28 a four stage process of increasing energy input is required 29 to produce an acceptable agglomerate. Although the agglomerates produced by this process would be acceptably 31 dry (that is, not sticky), the agglomerates would be 32 unlikely to be of sufficient quality to survive 33 transportation without unacceptable production of fines 34 during the transportation process.
It is also well known to reduce the oiliness or 36 stickiness of particulate coal agglomerates by the 37 evaporative de-oiling of such agglomerates. However, such 38 processes haYe the obvious disadvantage of increasing the 3~

energy requirements of the production process since super heated steam must usually be produced to provide the necessary energy to cause evaporation of the oil coating the agylomerates.
Summary of the Invention It is an object of the present invention to provide an improved coal agglomeration method which results in the production of better quality agglomerates in lower residence times.
The invention therefore provides a process for the production of coal agglomerates comprising agitating an aqueous slurry of coal particles in a first agitating zone in the presence of oil to form coal agglomerates, further agitating said agglomerates in either the first agitating zone or a second agitating zone in the presence of a fresh coal particle bearing slurry to improve the dryness and quality of the agglomerates, characterised by the step of transporting the slurry containing said agglomerates in a pipeline having a length of 500m or longer and being in communication with either the first agitating zone or the second agitating zone to further improve the strength properties of the agglomerates.
The agglomerates produced have been found to be well suited for long-term storage and/or transportation in bulk.
In a preferred form of the invention, the step of transporting the slurry containing the agglomerates in a pipeline ~`ollows each of the agitation stages and the transporting is preferably achieved in a pipeline loop.
The consolidation which occurs during formation and circulation of the agglomerate bearing slurry through the pipeline in combination with the two-step coal addition operation permits the production of strong agglomerates having a relatively dry surface. Agglomerates produced in this way show little tendency for sticking together or for attrition during handling operations. For these reasons, they are eminently suited for long-term storage and/or for transportation in bulk. The results achieved were not ,~ .

~2~53~

2a predictable and the inventors found the improvement in agglomerate quality by the circulation o~ the slurry in a pipeline quite surprising. The inventors are not yet aware of the physical reasons for the unexpected improvements . ,~,,~, ~, ....

~53~

1 achieved by the pipeline circulation, but it is clear that 2 the further contact between the agglomerates and the coal 3 particles in the slurry which occurs in the pipeline is most 4 beneficial.
In one preferred form of the present inYent;on, the 6 coal particles contained in the initial slurry are 7 preferably coated with oil and formed into small 8 agglomerates by introducing the slurry and the coating oil 9 into the inlet of a turbulent flow slurry pump. This method of oil coating and formation of small agglomerates has been ll described in our Australian Patent No. 529242 (AU-B
12 56D53/80). Of course it will be appreciated that acceptable 13 results may be obtained by the simple addition of oil to the 14 initial agitation stage in accordance with standard practice, However, the use of a turbulent flow slurry pump 16 to achieve the initial oil coating and formation of small 17 agglomerates has the advantage of reducing the energy 18 requirements of the agglomeration process.
19 In the present specification the term "pipeline" should be construed as a pipe of substantial length, for example, 2t at least 500m. Similarly, the term "oil" should be 22 construed to include all suitable hydrophobic liquids such 23 as kerosene, diesel oil, fuel, oill petroleum residue and 24 heavy aromatic materials such as coke oven tars and bitumen and suitable mixtures thereof.
26 Br~ef Descr~ption of the Dra_ings 27 A preferred embodiment of the invention will now be 28 described with reference to the accompanying drawing in 29 which: -Fig.1 is a schematic diagram showing an arrangement for 31 performing the process according to a preferred embodiment 32 of the invention.
33 Description of Preferred Embodiment ______ ____ __ _________ __________ 34 Referring to Fig.l of the drawings, the arrangement shown for performing the preferred embodiment of the process 36 according to the invention comprises a turbulent flow slurry 37 pump Pl into the inle~ of which suitable oil and a 38 particulate coal bearing aqueous slurry is introduced in the 3~3 .

manner described in greater detail in our Australian ~atent 2 No.529242. While it may be convenient to inject the oil 3 directly into the inlet of the pump, it wil 1 be appreciated 4 that the oil may he added at any suitable position upstream of the pump inlet.
6 The slurry general ly contains 30-50% by weight of 7 solids, including particulate coal which may result from a 8 grinding operationl washery or tailings pond. Any suitable 9 oil, such as a suitable grade of fuel oil, may be used to achieve agglomeration and the 4uantity of oil introduced 11 into the inlet of the pump Pl is selected according to the 12 nature of the particulate COd 1 contained in the slurry (see 13 above Patent No.529242).
14 The pump Pl discharges into a first agitation tank 1 in which the oil coated coal and partially formed agglomerates 16 produced in the pump Pl are further agglomerated~ A second 17 pump P2 is connected to the tank 1 and recirculates the 18 agglomerate bearing slurry produced in the tank 1 through a 19 pipeline loop Ll back into the agitation tank 1. During its passage through the pipeline loop Ll, the agglomerates are 21 consolidated to increase their strength and the strengthened 22 agglomerates are recycled into the mixing tank 1 so that 23 further growth can occur by contact with fresh oil coated 24 coal particles. The length of the pipe loop L1 is selected in conjunction with other operating parameters (such as oil 26 addition level, particle size distribution, residence time 27 in the tank/pipe loop) to achieve the required consolidation 28 and is preferably longer than 500 metres; for example 1600m 29 has been used in some pilot plant trials. rt has been surprisingly found that the consol idation which occurs in 31 the pipe loop Ll in combination with the agitated tank 1, is 32 not readily achieved in the agitated tank 1 alone, certainly 33 not in the same overal 1 residence time. In addition, the 34 size of the agglomerates can be controlled by adjustment of pipeline velocity and combined residence time in the tank 1 36 and pipe loop Ll~
37 If desired the pipeline may include flow disturbing 38 means which increase the mixing of the slurry in the 353~8 l pipeline as it is transported therethrough. See for example 2 our Australian Patent No. 529242 or United States Patent 3 No.3856668.
4 In an experimental pilot plant constructed to test the viability of the process according to the present invention, 6 the following parameters have been found to be successful:
7 An agitated tank having a volume of 300 m3 has been 8 used in conjunction with a lOOmm diameter pipe loop. The 9 agitator is fitted with a 21 kW motor. The total length of the pipe loop was l500m with bypasses fitted to allow use of 11 400m, 800m or 1600m lengths.
12 When using the 1600m length it was found necessary to 13 use more than one pipe loop pump to provide the necessary 14 head. Three 3/2 high head Warman slurry pumps were installed for this purpose.
16 Various combinations of pipe loop length and combined 17 pipe loop-agitated tank residence times have been used to 18 successfully produce the desired agglomerates depending on 19 the nature o~ the ~eed slurry~
A typical set of conditions inc1ude a combined mean 21 residence time of three hours using a pipe loop length of 22 800m.
23 When processing small batches of material, (say 2-3 24 tonnas) a smaller agitated tank having a volume of approximately 2m3 may be used in conjunction with the pipe 26 loop.
27 A third pump P3 continuously transfers agglomerate 28 bearing slurry from the tank 1 to a further tank 2 to which 29 fresh particulate coal bearing slurry is added. The second mixing tank 2 operates in a similar manner to the first 31 mixing tank 1 and a fourth pump P4 circulates agglomerate 32 bearing slurry from the tank through a second pipeloop L2 33 and back into the tank 2 to further improve the strength of 34 the agglomerates. The addition of fresh slurry to the tank 2 improves the surface condition o~ the agglomerates reducing 36 their oiliness while the second pipeloop L2 consolidates the 37 agglomerates produced in the tank 2 and improves their 38 strength.

i3l~3 1 A fifth pump P5 transfers the agglomerated product from 2 the tank 2 to a dewatering/classifying screen ~rom which any 3 small undersize agglomerates are returned to the tank 1 4 after separation of the waste mineral matter and water.
In a modification of the above embodiment, the second 6 mixing tank 2 is eliminated and the agglomerate bearing 7 slurry from the first mixing tank 1 is pumped directly into 8 the second pipe loop L2 for further conditioning in the 9 presence of fresh particulate coal bearing slurry, which may be introduced into the inlet of pump P4 in any suitable 11 manner.
12 A batch of approximately 2.2 tonnes of agglomerates has 13 been produced using a pilot plant according to the preferred 14 embodiment described above and the batch subjected to lS flowability tests.
16 In the pilot plant, the coal was processed through a 17 hammer mill and ball mill to generate a size distribution 18 similar to a typical pulverized fuel specification. The fuel 19 oil used to achieve agglomeration was heated to a temperature of 30-35C before addition to the slurry and the 21 slurry was circulated through the pipe loop Ll for several 22 hours prior to the oil addition to increase the temperature 23 of the slurry to approximately 25C. The remainder of the 24 process was as described above and the resultant de-watered agglomerates were found to be strong and well formed with a 26 top size of 2.3mm.
27 The following Table 1 summarises the results for this 28 run (d.b. = dry basis).

~2~3538~3 1 Table 1: Summary of Results for Ag~lomerates Produced _____ _ ___ __ __ _______ ___ _ _________ ________ 2 by the Pil_t Plant 3 Feed Coal 4 Ash %d.b 20.1 Size analysis prior to agglomeration (% passing) 6 Agglomerated Product 7 Sizel mm 8 0.5 98.8 9 0.25 96.0 0.125 83.7 11 0.063 61.0 12 Fuel oil addition 13 (%by weight dry feed coal)16.7 14 Ash, %d~b 6.9 It may be concluded from the tests conducted to date 16 (as detailed further below) that the method of the invention 17 produces agglomerates which are stronger, less sticky and 18 have a lower (2%-3%) ash level than agglomerates produced by 19 the prior art methods. While detailed comparative tests have not been conducted, qualitative observations have 21 indicated that the prior art methods would not be capable of 22 producing an agglomerate product of the same quality 23 without unacceptable residence times in stirred tanks. The 24 relatively short term circulation of the partly formed agglomerates in the presence of fresh slurry causes additive 26 consolidation and further release of mineral matter, to a 27 greater extent than would be achieved by further stirred 28 tank processing for an equivalent time~ It is not clear why 29 pipeline circulation achieves these results although it is clear that the agitation which occurs in a pipeline is 31 different in character to stirred tank agitation.
32 The batch of agglomerates produced by the pilot plant 33 was subjected to testing to determine the flow properties of 34 the agglomerates and their ability to withstand transportation in bulk.
36 For the design and performance evaluation of material 37 handling facilities, it is necessary to examine samples of 38 the materials which are like1y to produce the most difficult ~L2853~

l flow conditions The conditions of moist~re content, 2 temperature and storage time relevant to the material under 3 actual operating conditions need to be duplicated in the 4 tests. However, since the main aim of the tests is to obtain the characteristics of the agglomerates for 6 preliminary assessment of handling characteristics of the 7 agglomerate, particularly under sea transportation 8 conditions, oiled agglomerates having a moisture level 9 equivalent to that expected from a stock pile of the material were tested.
11 Table 2 lists the properties o~ the oiled agglomerates 12 used in the tests (d.b. = dry basis a.d.b. = air dry basis).

35~8~3 1 Table 2 Propertles of Olled A~glomerates 2 Moisture % (a.d.b.) approximately 5 3 Oil ~ (d.b.) " 17 4 ~sh % (d.b.) " 6.9 Size Analysis:
6 Size, mm % Passing 7 2.0 68 8 1.0 4 9 0.5 0.5 Ag~lomerate Handlin~ Characteristics ________ _______ _______________ 11 The ability of a bulk material to flow is dependent on 12 the strength developed by the material due to consolidation 13 and weathering. As a result of this strength, the material 14 may be able to form a stable arch or pipe. Free flowing bulk materials have no cohesion and hence no strength.
1~ Tests have indicated that agglomerates manufactured in 17 accordance with the present invention, and at 5% moisture 18 level, behave essentially as a free flowing material.
l9 Although ~his free flow characteristic is slightly dif~erent from a perfectly free flowing material such as dry sand 21 whose unconfined yield strength is always zero, energy coal 22 showed much greater strength than that of the agglomerates.
23 This means that the flowability of the agglomerates is much 24 better than that of typical Australian export coals.
Although there is some breakage of the agglomerates 26 under high stress conditions, tests have also shown that the 27 handling characteristics of the agglomerates are 28 satisfactory for ship load~ng transportation and unloading, 29 and for hopper storageO
Ship Transportation Tests ___ _____ ________ _____ 31 Degradation of particles due to stress and to vibration 32 of the ship is not a serious problem for the ~ajority of 33 bulk solids as the particles are intrinsically strong.
34 However consolidation (or compaction) of the bulk solids can create serious material handling problems if the bulk solids 36 contain a large proportion of fines or the bulk solids have 37 a cohesive characteristic.
38 The difficulty in handling compacted bulk solids is ~53~3~

dependent on the degree of strength developed in the 2 compacted material and this important characteristic depends 3 on the proportion of fines, moisture content, consolidation 4 pressure, storage time and in the case of oi led agglomerates the oil content.
6 Tests have been conducted to evaluate the effect of stress 7 on the compaction and degradation of our oiled agglomerates to 8 predict the degree of degradation and compaction of the 9 agglomerates which could be expected in the cargo hold of a 100,000 DWT bulk carrier. These tests have shown:
11 (1) During loading into the cargo hold of a ship, 12 aggl omerates are compacted~ by the weight of the material 13 during loading, but further compaction due to storage time 14 and ship vibration is small.
(2) At a stress above lOOkPa the agglomerates formed 16 into a consolidated cake although blocks of the cake were 17 easily broken into separate agglomerates. This means that 18 the compacted agglomerates near the bottom of the ship hold 19 would not come crumbling down easily when the agglomerates are unloaded. However this is not essential if the material 21 is unloaded using a grab.
22 t3) At a stress of 150kPa (estimated stress for a 23 material depth of 20m in the cargo hold) the degradation of 24 agglomerates would be expected to result in an increase in the 0.5mm size particles of about 5%. At the half depth of 26 the hold (lOm deep) the figure would be less than 1%. These 27 fines do not appear as discrete dry particles but are 28 a t t a c h ed t o t h e s u r ro un di n 9 1 a r ge r p a rti c 1 es o f 29 agglomerates~ Hence they do not form a dust problem in handling.
31 Fu_ther ~xample of the Invention 32 To check the viability of the process embodying the 33 invention for lower grade feed material, further tests were 34 conducted using the pilot plant described above and are detailed below.
36 Five tankers containing a waste thickener underflow 37 from a high volatile energy coal preparation plant were 38 transported to the pilot plant for testing.

~353~3 , 1 1 Following transfer of the slurry to a surge tank, the 2 solids concentration was adjusted to approximately 20% (by 3 weight) prior to desliming.
4 D~sliming was undertaken by pumping the slurry through two 100mm KRT 2118 IV cyclones. An initial test was done 6 using a 20mm apex stopper diameter. However th;s was 7 subsequently enlarged to 25 mm diameter to give a cyclone 8 underflow solids concentration of approximately ~0%. A
9 cyclone inlet pressure of 250 kPa was used and the flowrate to each cyclo,ne was approximately was 17m3/h. The u~derflow 11 was stored in temporary tanks during processing and returned 12 to the surge tank on completion of the desliming. Some 13 additional water was used to rinse the larger particles from 14 these tanks.
The deslimed slurry was circulated through a ball mill 16 closed circuit to grind the solids to a size distribution 17 close to that of typical pulverised coal (99% passing 300 18 microns). Approximately lOm3 of this slurry was reserved 19 ~or secondary addition to the agglomerates after initial agglomeration.
21 After grinding, agglomerating oil was added to the 2Z slurry at the inlet to the ball mill sump pump whilst the 23 slurry was circulated through a 1 km long 100mm diameter 24 pipeloop and surge tank circuit~ The oil was added in 2~ several steps to ensure that excessive oil was not used.
26 A low sulphur furnace oil (0.4% sulphur) was used to 27 permit the production of agglomerates having a low sulphur 28 specification.
29 Circulation of the slurry was continued until the agglomerates had reached 2-3 mm in diameter. At this stage 31 additional finely ground slurry was added to the surge tank 32 to absorb excessive oil on the agglomerate surface and 33 produce a "non sticky" transportable product. Circulation 34 was continued for a further two hours prior to dewatering the agglomerates on a 0.5mm wedge wire vibrating screen.
36 A series of water sprays were used on the screen to 37 rinse off excessive clays and other mineral matter prior to 38 discharge of the ~gglomerates into the storage hopper.

~L285388 1 Details of the various slurry and solids balances are 2 summarised below. These figures are approximate and are 3 based on best estimates from tank volumes and flows. Note 4 that there are some variations in volumes due to additional water used for rinsing and pump gland seals.
6 Th~ck~ner Underflow total volume = 104m3 7 solids = 35t 8 after unloading to total volume = 154m3 9 surge tank slurry density = 1.108t/m3 solids concentration = 20,6%
11 solids = 35t 12 Size analysis and Ash distribution 13 Size fraction Weight Ash 14 mm Fraction % %d,b, ~0.5 3.9 22~6 16 -0.5 ~0.25 15.8 31,6 17 -0.25~0.125 16,0 47,7 18 -0.125~0.063 12.0 37,5 19 ~0.063 52,3 58.9 total 48.8 21 Cyclone Underflow _ ____ _____ _ __ 22 total volume = 47m3 23 slurry density = l.l99t/m3 24 solids concentration = 40.5%
solids = 23t 26 solids recovery yield 27 from cyclone fee, d.b. = 65.7 28 ~coal matter recovery 29 from cyclone feed, d.b. = 72.8%
~coal matter = solids - mineral matter; assuming mineral 31 matter = 1.1 x ash.
32 Size analysis and Ash distribution 33 Size fraction Weight Ash 34 mm Fraction % %d.b.
~0.5 7.0 21.7 36 -0.5 +0.25 22.3 29.5 37 -0.25~0.125 22.3 40.3 38 -0.125+0.063 16.2 33.4 ~8~i3~3 1 -0.063 32.2 67.8 2 Total ~4~3 3 Cyclone 0verflow 4 total volume = 122m3 S slurry density = 1.048t/m3 6 solids COnCntration = 9.55%
7 solids = 12t 8 Size analysis and Ash distribution 9Size fraction Weight Ash mm Fraction % %d.b.
11 ~0.063 2.2 11.1 12 -0.063 +0.045 1.6 6.1 13 -0.045 +0.038 1.6 8.2 14 -0.038 94.6 58.7 Total 56.0 16 Crushed Slurry Prior to Agglomeratlon 17 tvtal vo1ume = 71m3 18 slurry density = 1.136t/m3 19 solids concentration = 28.8%
solids = 23t 21 Size Analysis 22 Size, mm %passing 23 0.5 99.9 24 0.25 99.3 0.125 94.3 26 0.063 75.1 27 Ash, % d.b. = 44.3 28 Agglomeration __________ .
29 volume of initial slurry used for agglomeration = 61m3 31 solids = 20t 32 total oil added = 3666kg 33 (assuming oil 34 density =
0.94t/m3) 36 oil added on initial 37 solids (d.b.) = 18.3% (by 38 weight) ~ ~ 53 ~ ~

l Additional solids added = 3.3t 2 during secondary 3 agglomeration 4 oil added on total = 15.7%
solids ~d.b.) 6 Product A~lomerates _______ _ _________ 7 Estimated agglomerated = 12.2t 8 product, dry, oil free 9 Estimated agglomerated = 17t product including oil and 11 10% moisture 12 Product ash, %dry oil free = 5.9 13 Estimated product yield = 52.2 14 from ground deslimed slurry, %d.b. (for tailings ash = 86.5%
16 d.b.) 17 Estimated product yield = 34.9 18 from original thickener l9 underf1Ow, %d.b.
Estimated coal matter yield = 97 21 from ground slurry, %d.b.
22 Estimated coal matter yield = 70.6 23 from original thickener 24 underflow, %d.b.
Estimated oil based on = 21.6%
26 dewatered product basis 27 (including oil and 10% moisture) 28 Chemical Anal~sis: ~expressed on moisture free basis, __ _ __ _ _ _ _ _ __ _ 29 including oil) Ash 5.0%
31 Vo 1 atile Matter 46.8%
32 Fixed Carbon 48.2%
33 Total Sulphur 0.42%
34 Specific Energy 33.9MJ/kg 1 The moisture of the agglomerates from the product hopper 2 after overnight drainage was approximately 12.5%.
3 Agglomeration and mineral matter separation of the 4 deslimed product was readily achieved in the above example.
The product ash was significantly lower than that 6 achieved in bench scale tests using conventional stirred 7 agglomeration techniques; this results from the higher 8 levels of consolidation and exclusion of mineral matter 9 achieved in the pipeline and agitated tank circulation system. Petrographic examination of bench scale products 11 showed that the mineral matter in those agglomerates 12 contained approximately 25% pyrite. It is presumed that use 13 of the present invention results in elimination of the 14 majority of this pyrite, as long as it is ground to a size 1~ which a71Ows separation over the dewatering screen.

Claims (20)

1. A process for production of coal agglomerates comprising agitating an aqueous slurry of coal particles in a first agitating zone in the presence of oil to form coal agglomerates, further agitating said agglomerates in either the first agitating zone or a second agitating zone in the presence of a fresh coal particle bearing slurry to improve the dryness and quality of the agglomerates, characterised by the step of transporting the slurry containing said agglomerates in a pipeline having a length of 500m or longer and being in communication with either the first agitating zone or the second agitating zone to further improve the strength properties of the agglomerates.

2. The process of claim 1, wherein the step of transporting the slurry in a pipeline follows the first mentioned agitation stage.

3. The process of claim 1, further comprising the step of introducing further coal bearing aqueous slurry to the slurry being transported in said pipeline.

4. The process of claim 2, further comprising the step of introducing further coal bearing aqueous slurry to the slurry being transported in said pipeline.

5. The process of claim 3, wherein said step of transporting the slurry comprises recirculation in a pipeline loop back to the first agitating zone.

6. The process of claim 4, wherein said steps of transporting the slurry comprises recirculation in a pipeline loop back to the first agitating zone.

7. The process of claim 2, further comprising delivering said slurry containing said agglomerates from said pipeline to a second agitating zone and agitating said agglomerates in the presence of fresh coal bearing slurry.

8. The process of claim 7, further comprising transporting the agglomerates and slurry from said second agitating zone through a further pipeline to further improve the quality of said agglomerates.

9. The process of claim 8, wherein said transportation of agglomerates and slurry from the second agitating zone comprises recirculation in a pipeline loop back to the second agitating zone.

10. The process of claim 9, further comprising the step of transferring the agglomerated product of the second agitating zone to a dewatering/classifying screen, and wherein said transportation of the slurry from the first agitation zone comprises recirculation of the slurry in a pipeline loop back to the first agitation zone.

11. An apparatus for producing coal agglomerates comprising a first agitating means, means for introducing an aqueous slurry of coal particles into said first agitating means in the presence of oil, means for withdrawing the slurry and agglomerates produced by said first agitating means, a first pipeline having a length of 500m or longer and being connected to said withdrawing means, and means for collecting said agglomerates from said pipeline for further processing.

12. The apparatus of claim 11, further comprising a second agitating means, means for introducing said agglomerates from said pipeline into said second agitating means, means for introducing fresh coal bearing aqueous slurry into said second agitating means, a second pipeline having a length of 500m or longer and being attached to said second agitating means and means for circulating said agglomerate bearing slurry through said second pipeline.

13. The apparatus of claim 11, further comprising means for introducing fresh coal bearing aqueous slurry into said pipeline.

14. The apparatus of claim 12, further comprising a means for transferring the agglomerated product of the second agitating zone to a dewatering/classifying screen, wherein the first pipeline comprises a pipeline loop which returns to the first agitation means, and wherein the second pipeline comprises a pipeline loop which returns to the second agitation means.

15. The apparatus of claim 11, wherein the first pipeline comprises a pipeline loop which returns to the first agitation means.

16. The apparatus of claim 12, wherein the second pipeline comprises a pipeline loop which returns to the second agitation means.

17. In a process for production of coal agglomerates comprising agitating an aqueous slurry of coal particles in at least one agitating zone in the presence of oil to form coal agglomerates, further agitating said agglomerates in at least one agitating zone in the presence of a fresh coal particle bearing slurry to improve the dryness and quality of the agglomerates, the improvement comprising improving the strength properties of the agglomerates by transporting the slurry containing said agglomerates in a pipeline having a length of 500m or longer and said pipeline being in communication with at least one agitating zone.

18. The process of claim 17, wherein said agitating of the aqueous slurry and said further agitating the agglomerates occur in the same agitating zone.

19. The process of claim 17, wherein said agitating of the aqueous slurry and said further agitating the agglomerates occur in a different agitating zone.

20. Coal agglomerates when produced by the process of claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.