THE CRUSHING OF Al\ITHRACITE WITH A JAW CRUSHER

Transcription

1 SPECIAL REPORT OF RESEARCH Conducted in Department of Mineral Preparation College of Mineral Industries The Pennsylvania State University THE CRUSHING OF Al\ITHRACITE WITH A JAW CRUSHER by P. D. RAO H. B. CHARMBURY D. R. MITCHELL An Investigation Conducted Under the Auspices of the COAL RESEARCH BOARD of the COMMONWEALTH OF PENNSYLVANIA Special Research Report Number SR-4 November l, 1958

2 TABLE OF CONTENTS Page S~Y o " o o o o o o o.,.. o o... o l INTR.ODUCTION o o o "' o 2 T~ JAW CRUSHER o o o 3 LABORATORY EXPERIMENTS. 6 PILOT PLANT TESTS o " o o o 12 INTERPRETATION OF RESULTS. 16

3 LIST OF TABLES Table 1 - Size Analysis of Products fromcrushing Nut Coal in a 4 x 6 inch Laboratory Jaw Crusher with a 1/4 inch set... 7 Table 2 - Size Analysis of Products from Crushing Nut and Stove in a 4 x 6 inch Laboratory Jaw Crusher with a 1/2 inch Set... 8 Page Table 3 - Size Analysis of Proeucts from Crushing Nut and Stove Coal in a 4 x 6 inch Jaw Crusher with a 3/4 inch set... 9 Table 4 - Size Analyses of Products from Crushing Egg, Stove, and Nut Coal in a 10 x 20 inch Pilot Plant Jaw Crusher with a Minimum 3/8 inch Set Table 5 - Standard Anthracite Sizes Produced from Crushing Egg, Stove, and Nut Coal in a 10 x 20 inch Pilot Plant Jaw Crusher with a Minimum 3/8 inch Set... "'... 14

4 LIST OF FIGURES Figure l - Blake-Type Jaw Crusher... 4 Figure 2 Dodge-Type Jaw Crusher... 4 Page Figure 3 - Average Size Analyses (Standard Anthracite Sizes) of Products from Crushing Nut Coal in a 4 x 6 inch Laboratory Jaw Crusher with Different Sets Figure 4 - Average Size Analyses (Standard Anthracite Sizes) of Products from Crushing Stove Coal in a 4 x 6 inch Laboratory Jaw Crusher wit~ Different Sets Figure 5 - Diagram of 10 x 20 inch Blake-Type Jaw Crusher used in Pilot Plant Tests Figure 6 - Standard Anthracite Size Analyses of Products from Crushing Egg, Stove, and Nut Coal in a 10 x 20 inch Pilot Plant Jaw Crusher with a 3/8 inch Set Figure 7 - Schematic Flowsheet of a Typical Anthracite Coal Preparation Plant Using a Jaw Crusher to Reduce the Domestic Sizes to Steam Sizes... 17

5 SUMMARY Pilot plant tests have conf irmea laboratory experiments ani indicated that the jaw crusher may be usea to reduce the domestic sizes of anthracite to steam sizes and produce only a small amount of extreme fines. The tests were conductea using a 10 x 20 inch Jlake-type jaw ' crusher with the minimum 3/8-inch set. Egg, stove, and nut coal were used in the tests and the distribution of sizes in the products was approx~mately constant regareless of the feed size. The amount of buckwheat producea ranged from 37 to 39'7. of the feed, the amount of rice from 16 to 19'7., and the amount of barley from 12 to 14%. The amount of No. 5 and smaller ranged from 7.1 I to 8.7'7. and the amount of oversize consisting of nut and pea rancea from 17.2 to 17.5'7.. The crusher was operated with a 25 HP motor at 270 revolutions per minute and at a feed rate of from 8.1 to 8.7 tons per hour. Operating costs for this type of duty in a plant installation should be very low, not exceeding 5 cents per ton for operating labor, maintenance and power, and probably would be of the order of 2-3 cents. Power consumption for a 10 x 20 inch crusher would be of the order of O.l-0.5 kw hr per ton crushed.

6 2. INTRODUCTION At the present time the anthracite coal producers and coal preparation engineers are vitally interested in economical methods of crushing the domestic sizes of anthracite to steam sizes. Coal mining an~ coal cleaning practices in the anthracite region result in the proeuction of all standard anthracite sizes. The.amounts of the individual sizes are dependent upon the particular mining and preparation prac tices at the various mines and plants. Present market requirements during most seasons of the year require a larger percentage of the coarse steam sizes than is produced by present preparation plant practices. To bring mine & preparation plant size production in line with market requirements, economical methods for reducing the domestic.sizes to steam sizes at will with minimum production of the low priced No. 5 and I smaller is needed. Experiments on the crushing of anthracite in a small laboratory size Jaw crusher were presented in a previous report number SR-1 of June l, 195,8. Results of these experiments indicated that the Jaw Crusher offered possibilities. Consequently the present tests were conducted on a pilot-plant basis in a larger 10 x 20" crusher to determine if these same possibilities exist with larger operations. The results presented herein show that the Jaw crusher could be used for this purpose.

7 3. THE JAW CRUSHER Jaw crushers have a breaking action similar to a nut cracker. The particles to be broken fall by gravity in-between two breaking plates or jaws and remain there until they are small enough to pass between the setting of the plates at the bottom of the crusher. The one plate is stationary and is mounted rigidly on the frame of the crusher. The other plate moves to and from the stationary plate. The moving plate may be hinged at the top as illustrated in Figure l or it may be hinged at the bottom as shown in Figure 2. The former is called the Blake type jaw crusher and the latter is called the Dodge type. ~ of jaw crusher called the Kue-ken, with two movable jaws. There is a third type The maximum size of the opening between the plates at the top of the crusher is called the gape. This is used to designate the maxi mum size particle that may be added to the crusher. Generally, the top size of particle in the feed to the crusher is not larger than three fourths the gape. Particles larger than this are "squeezed" out of the top rather than being "gripped" by the jaws and broken. In order to help this, however~ the plates may have a wave type surface or gripping ridges may be placee across the surface of the jaws. The maximum size of the opening between the plates at the bottom of the crusher is callea the set. This is used to designate the top size of the particle in the product from the crusher. Naturally, this size designates the second largest dimension of the particle since long flat particles may escape from the crusher. This accounts for the small amount of oversize material generally present in the product.

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9 5. Jaw crushers on the market today are intended to be used as primary crushers for hard coarse particles. The gape sizes are relatively large, usually over 10 inches, and the length across the face of the plates is generally a little larger than the gape. These two sizes are used to designate the size of the crusher. Jaw crushers are made in sizes up to 84 x 120 inches. All curshers of this type have an adjustable set so as to make a product as coarse or as fine as desired. This would be a particular advantage as far as anthracite is concerned in view of variable market size requirements. Normally, for hard rock crushing the reduction ratio, or the ratio of the maximum size particle in the feed to the crusher to the maximum size particle in the product from the crusher, is generally around 7 to l~ This can be compared to crushing ratios of the order of i 1.3 to 1.5 for toothed rolls in anthracite preparation plants. With softer material, however, such as anthracite there is no reason why larger reducs tion ratios could not be accomplished with reasonable capacities. The energy consumed by jaw crushers varies considerably an«is base& upon the hardness of the material to be crushedp the reduction ratio being attained, and the. capacity. Crushing anthracite from the domestic to steam sizes would appear to be reasonable. Labor required to operate this type of crusher would not be any more than for any other type of crusher. Breakdowns with jaw crushers generally result from large pieces of metal jamming the jaws and fracturing the toggles or from a failure in the lubrication system. clean anthra~ite. This would also be minimized by crushing large sizes of Also, the wear on the crushing plates from anthracite would be at a minimum tn comparison to the wear from hard rock. 1 all the jaw crusher offers possibilities for anthracite. All in

10 6. LABORATORY EXPERIMENTS A small 4 x 6 inch Dodge type jaw crusher was used for the laboratory experiments. Samples of stove and nut anthracite were obtainea from a local dealer and each was tested in the crusher with sets at 1/4, 1/2, ana 3/4 inches. It was impossible to crush the stove size with a 1/4-inch set and it was even difficult to crush the same size with a 1/2 inch set. The 1/4 inch set with stove coal represents a ~eduction ratio of about 10 and the particles would be squeezed out of the crusher instead of gripped ana broken. No special provisions were made on the face of the jaw to cope with this situation. Results of the tests showing the size analyses of the crushed products in each case are presented in Tables 1, 2, and 3 and average results in terms of standard anthracite sizes are presented in Figures 3 and 4. These results show that the jaw crusher has possibilities for reducing anthracite and that the products are quite sensitive to the set. In crushing nut size~ the percentage of the products in the sizes pea to barley decrease from 87.9 to 69.9% as the set increases from 1/4 to 3/4". The amounts of No. 5 and smaller decrease from 4.2m 1.6% with an increase in the set. In crushing stove size in the jaw crusher the amounts of nut plus pea sizes increases from 51.0 to 65.0% and the amounts of buck plus rice plus barley si.~es from 1/2 to 3/4 inches. constant at about 3.5%. decrease from 37.O to 22. 3% as the set increases The amounts of No. 5 and smaller remained fairly In no case did the amounts of fines appear to be excessive.

11 7. Table l Size Analysis of Products frc:mcrushing Nut Coal in a 4 x 6 inch Laboratory Jaw Crusher with a 1/4 inch Set. Oversize l 31.6.s.ili l 2 3 1/2-3/ l 3/8-1/ /4-1/ l 1/8-1/ /16-1/ /

12 8. Table 2 Size Analysis of Products from Crushing Nut and Stove Coal in a 4 x 6 inch Laboratory Jaw Crusher with a 1/2 inch Set. Nut Coal Oyenize : :2.sJa 1..L_ 3 1/2-3/ /8-1/ /4-1/ /8-1/ /16-1/ / Stove Coal Oversize ll 1/2-3/ /8-1/ /4-1/ /8-1/ /16-1/ / l

13 9. Table 3 Size Analysis of Products from Crushing Nut and Stove Coal in a 4 x 6 inch Laboratory Jaw Crusher with 3/4 inch Set. Nut Coal oversize l llia l 2 3 1/2.. 3/ /8.. 1/ /4-1/ /8-1/ /16-1/ / Stove Coal oversize 73.l llia /2-3/ /8.. 1/ /4-1/ /8-1/ /16-1/ /

14 _... Gape 4 inches Gape 4 inches Gape 4 inches Size Analysis of Products ;? 11/ 1'0 I Set 1/4 inch Set 1/2 inch Set 3/4 inches j!/ Nut Pea Euckwheat Rice Barley Buckwheat No. 4 No. 5 & smaller % % l % l.o l Figure 3 Average Size Analyses (Standard Anthracite Sizes) of Products from Crushing Nut Coal in a 4 x 6 inch Laboratory Jaw Crusher with Different Sets

15 ~- -- Gape 4 inches Set 1/2 inch Gape 4 inches u ri I I l/ /! /I 1?--.. // /IU '-' Set 3/4 inch Size of Products ~ % Stove Nut Pea Buckwheat Rice Barley Buckwheat No. 4 No. 5 & Smaller u Figure 4 Average Size Analysis (Standard Anthracite Sizes) of Products from Crushing Stove Coal in a 4 x 6 inch Laboratory Jaw Crusher with Different Sets iii&

16 , 12. PILOT PLANT TESTS The crusher used in the pilot plant tests was a 10-inch by 20-inch forced feed Blake-type jaw crusher. It was driven at a rate of 270 RPM by a 25 HP motor. At rest, the crusher can hold 103 lbs of stove coal in its throat of which 71-l/2 lbs is held in the actual crushing zone. The crusher was operated with the set or discharge opening as small as possible. This was 3/8 inch. A diagram of the crusher is presented in Figure 5. The tests were conducted by hand fee6ing the coal to the crusher at the maximum rate. Egg, stove, and nut coal were used in the tests and the feed rates were 8.1, 8.6, and 8.7 tons per hour respectively. Screen analyses were conducted on all products and t~e results were plotted on Rosin-and Ramler graph paper. Standard anthracite-size values were obtainee from the graph. Results of the size analyses are presented in Table 4 and the results expressed as standard anthracite sizes are shown in Table 5 and in Figure 6. The results &how that the size analyses of the crushed products were approximately the same regardless of the size of the feed. In all cases 98% of the feed was reduced to pea size and smaller. The combined amount of buck, rice, and barley ranged from 67.4 to 70.3% as the size of the feed decreased from egg to stove to nut. The amount of undersize, i.e. No. 5 and smaller, rangea from 8.7% with egg as the feed coal to 7.1% with nut as the feed. These latter percentages are not considered to be excessive and the percentages in the steam sizes of buck, rice, and barley are considered as satisfactory.

17 l 13. I.'/ (. --..,,,. I!!, , _ -- '',. -;:7/ I -- -~ - ;!' )'\ I.,,;:/..,_,.,, "~ -- Q~ "-." "-,,,~...,_.. ~.-~-0. \\ Cr 1 / /...._...-,.~~;5)_ -....r::_. J_j;.,~--:~ rc;~:- :;.~: ~: x~ , q ~ ---"["~ ~);~~ f ~--~\\'~..\ I I i w ',) - -~"- ~'.(.'/, \ ' :"l fr'.ji '~, ; g.._;.1.:. ~- :JV,, ' :~."-- I ' _,,/ '"' L '''" '\ /,:.,_. ' ' [ -.:-"'/" -.. <.-:;-'. :... / (' ' i''" t- - ' /,,, ! ~,.,, I '~-- I ' 6-,, :: il oe- \ ~"''~"' "--- / J B it -,- r I -,i. -~U" 1. 't'. I I ;' ';- /',-- ' ' I '\.I,, : ' '\Ji er:::::::> F ;\~\'-\;..~:; -~I-- '_, t ',(:J ' :'1r'~i'~~1. 1 (; 1 11.j,..,. i,, ' ' ', ' '.,., ' - ' --, ;,,,,\, I It'>'./ '/ :; I - \ ' ">'""!!..!. 1~: 1'.,,_.,J:.,',;~' ' '~~- l I 1>\ ; ' ; /"' I fj, : / / i ~ t ~"'l i ; :., I t"-:.-'i 1'.1/ l<'t\,::.j, 1 r~ ; '..J,' " /.,. -. ;, '_;...,, - ''j :. "" e '\ - 1,...\ ~ '~,, -- - '",/" >'.,, ' A;,, u ;;l.''('"'cc ---:-~' _;,').< ~-"-c----- I --:,. --.: ~;,_ 1- j/. ---C- [ --!1~. ~., y( l yy '"...)'.. Ii_/,.. /:.)::/ [;----~=-;/ -.'_.. ~J,\'(\ \".-~~. I ~~~cc,1?~f- \1-./:' '..., J k ~:~ ~~!~ '~ 1-c " -'f I Figure 5 Diagram of 10 x 20 inch Blake-Type Jaw Crusher used in Pilot Plant Test

18 14. Table 4 Size Analyses of Products from Crushing Egg, Stove and Nut Coal in a 10 x 20 inch Jaw Crusher with a 3/8 inch Set. Feed Egg Coal Stove Coal.... }~~t Coal Size Cum. Wt. Cum.wt. Cum.Wt. inches wt.!:,. pct.rte. wt.pct. pct.rtd. wt.pct. zct.rtd. +3/ /4 x 1/ /2 x 3/ /8 x 1/ /4 x 1/ /8 x 1/ /16 x 1/ _ /32 x Total Table 5 Standard Anthracite Sizes from Crushing Egg, Stove and Nut Coal in a 10 x 20 inch Jaw Crusher with a 3/8 inch Set. Feed E&& Coal Stove Coal Nut Coal ~ Nut /fxl3/16 Pea /hx9/16 Buckwheat 39, /1 x5/16 Rice l 5/Hx3/16 Barley /lfx3/ 32 No /3~x3/64 No.5 & smaller Minus 3/

19 :, ~';1..,-.. _',' ',}~i ~ '].. l : } -.~ :; 1.. J<:,:r>;; k :~:,,/I ~K~:~;~i~.~. L:ti!J~l N P l a. Nut Coal N Nut P Pea l Buckwheat 2 Rice L~$end 3 Barley 4 Buckwheat No. 4 5 Buckwheat No. 5 and Smaller Np 1 2 ~ ' b. Stove Coal '!:~.~ ~ '.,. >:: ' _ ' 10 u l r -,}!.1. :[]...r.:::::: L',... --" - N P l c. Egg Coal Figure 6 Standard Anthracite Size Analyses of Products from Crushing Egg, Stove, and Nut Coal in a 10 x 20 inch Pilot Plant Jaw Crusher with a 3/8 inch Set.

20 16. INTERPRETATION OF RESULTS In order to interpretate the results of the crushing tests, a schematic flowsheet of a typical anthracite coal preparation plant using the jaw crusher is presented in Figure 7. The plant illustrated in the figure is based on a flow rate of 100 TPH and it is assumed that the recovery of clean coal from the cleaning operations is 90%. It is also assumed that the run-of-mine coal is scalped of broken and larger and that these sizes are hand-picked or cleaned before crushing in double rolls to egg and smaller. The egg and smaller sizes are separated at 9/16 inch and the egg to pea sizes inclusive are cleaned in a heavy-media unit. Buck sizes and smaller are cleaned in separate units. The final assump tion is that the clean coal from the heavy media unit is crushed in a jaw crusher with a 3/8-inch set the same as in the previous pilot plant tests. If the coal were simply cleaned prior to preparing the commercial sizes the company could expect 7.0 tons of huck, 5.26 tons of rice, and 3.92 tons of barley from 100 tons of run-of mine material. The company would also have tons of egg, tons of stove, tons of nut, and 5.90 tons of pea. On the other hand if the clean coarse coal from the heavy media unit were crushed in a jaw crusher and combined with the cleaned fine coal before preparing the commercial sizes the company could expect tons of buck, tons of rice, and tons of barley. In the latter case the company would have to dispose of 5.27 tons of buck no. 4 and 7.70 tons of buck no. 5 and smaller instead of 2.20 tons of buck 4 and 3.07 tons of buck no. 5 and smaller. The reduced income from all of the smaller sizes must be balanced economically against the market demands for all of the sizes to determine the extent to which crushing is conducted.

21 40 ROH Coal 100 TPH!!_~~Y pi R~.SuT~ns t J ~-+-,,, <f Refuse ----:_:l ~ Jlf:'M :SJ. ~l.42 Tons --LJ9-!.L % fl) fl) fl) fl) fl) fl) fl) fl) fl) fl) fl) fl) c.: r:: -~ r:: r:: i:: r:: i:: r:: r:: i:: r:: E-t o E-4 o iio E-t - E-t o E-t o E-t o E-t o E-t o E-t o E-t o E-t o 0 ~~:i~~ &l"\"1 &l"\00,.:..nm"' 000 L S B E S N P l 5 Run of Mine Coal % QI % I 2 1 J I p-=r::1 I l l r % Clean Fine Coal 20 r I rrl Al it""4' I (/) Jaw ~J;I 10 l I ~~l~i ~ Crusher - 0 Clean Coarse Coal, ~ 1:0 l 10 ~ OL. I I r 30 Lee;end I p L Lump I H E-t r fl) fl) s:: r::!i) fl) fl) 0 0 ~ I Sb Steamboat 1 Pea Buckwheat 20 B Broken 2 Rice r~.0. i:: r:: i:: r:: r:: 0 es eses es 3 Barley 10 " '""M H E-t E-t E Egg r-f N 0\~~1..-f \0 *.. M r-.. 4 Buckwheat No4 r-fn 5 Buckwheat No5 0 " If) 0 N N 0 " 0 s Stove U"'I N 0\ U"'I 0\ If)... N Nut I r-fn tr) p 1 & 2 Smaller p Finished Coal Crushed Clean Coal Figure 7 Schematic Flowsheet of a Typical Anthracite Coal Preparation Plant Using a Jaw Crusher to Reduce the Domestic Sizes tofil:eam Sizes.