Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 14 Aggregate Production

AGGREGATE PRODUCTION

Four basic functions:  Size reduction - crushing  Size separation- screening  Elimination of undesirable material - washing  Movement and storage

 Crushers  Crusher Production  Screening  Screen sizing AGGREGATE PRODUCTION

CRUSHERS  Jaw  Gyratory  Cone  Roll  Impact  Specialty

JAW CRUSHERS Rock flows into the space between two vertical jaws. One jaw is stationary. The other jaw moves in an elliptical-downward motion toward the stationary jaw while crushing, and upward and away from the stationary jaw allowing the crushed material to exit.

JAW CRUSHERS Stationary Moves in an elliptical- downward motion toward the stationary jaw while crushing

JAW CRUSHERS Table 14.3 gives representative capacities.

JAW CRUSHERS Jaw crushers are primary units, that receive material directly from the quarry.

GYRATORY CRUSHER Has a gyrating mantle mounted within a deep bowl.

Table 14.4 gives representative capacities. GYRATORY CRUSHER

Gyratories are used as primary or secondary units.

CONE CRUSHER Works like a gyratory with an eccentric rotating cone around a vertical shaft to cause a gyrating movement of the head. Differs from a gyratory: Ø A shorter head Ø Smaller receiving opening Ø Higher rotation speed

GYRATORY & CONE CRUSHERS Cone shorter head Gyratory

GYRATORY & CONE CRUSHERS Gyratory Cone smaller receiving opening

GYRATORY & CONE CRUSHERS Cone higher rotation speed Gyratory

ROLL CRUSHERS

Roll crushers are used for intermediate stages of reduction. Very limited reduction capability, see Table 14.2, page 411.

ROLL CRUSHERS The maximum size stone that may be fed a roll crusher is directly proportional to the diameter of the rolls. If the stones are too large, they will not grip the material and pull it through the crusher. See Figure 14.10, page 421.

IMPACT CRUSHERS Impact breakers provide a cubical product even with slabby material.

IMPACT CRUSHERS Speed of rotation is important to the effective operation of these crushers.

SPECIALTY CRUSHERS Ball Mill Ball mills use steel balls to produce fine material.

BALL MILL

PRODUCTION EXAMPLE A 42X48-in jaw crusher w/ a closed setting of 3 in. will produce what tonnage per hr in the following size ranges of a stone having a unit weight of 110 lb/cf crushed: - 2½ in. + - Between 2½ and 1½ in. - 1½ in. -

CRUSHER PRODUCTION Table 14.3 gives capacities for Blake-type jaw crushers. Table 14.4 for gyratory crushers. Table 14.5 for cone crushers.

STEP 1. CAPACITY OF CRUSHER 42- by 48-in jaw crusher Closed setting of 3 in. Capacity of crusher ?

STEP 1. CAPACITY OF CRUSHER 42- by 48-in jaw crusher Closed setting of 3 in. Capacity of crusher Table 14.3, p tph

CRUSHER PRODUCTION  Read the fine print.

STEP 2. CAPACITY ADJUSTED Capacity of crusher 190 tph Stone unit weight of 110 lb/cf Unit weight adjustment = or tph  1.1 = 209 tph

Jaw closed setting, 3 in. Refer to Figure 14.5, page 415 Horizontal scale is the crusher setting: Read down the 3 in. line and find the % passing a 2 1/2 and 1 1/2 inches. STEP 3. SIZE DISTRIBUTION

Fig. 14.5, read down the 3” line to the size. STEP 3 SIZE DISTRIBUTION Percent passing is on the left side of the figure.

Figure 14.5, page 415 Horizontal scale is the crusher setting: Read down the 3 in. line and find the % passing at 2 1/2 and 1 1/2 inches. 2½ in. 73 % passing 1½ in. 46 % passing STEP 3 SIZE DISTRIBUTION

STEP 4. QUANTITY Output of crusher, 209 tph

STEP 4. QUANTITY Output of crusher, 209 tph

STEP 5. CHECK Check your work, always total Percent must come to 100% Output must equal quantity Output of crusher, 209 tph OK

ROCK TYPE EFFECT Is there data available concerning rock type?

ROCK TYPE EFFECT Adjustment factors for rock type, limestone as a production base

ROCK TYPE EFFECT

If the rock in the previous example was limestone the 209 tph is correct. However, consider that it is a diorite. What would be the production?

EXAMPLE No. 2 Select a jaw crusher for primary crushing and a roll crusher for secondary crushing to produce 110 tons per hour of limestone rock. The maximum-size stone from the quarry will be 16 in.

EXAMPLE No. 2 The stone is to be crushed to the following specifications:

STEP 1 Select a Jaw Crusher The maximum-size stone from the quarry will be 16 in. Minimum top width (opening) of the jaw crusher: 16 in. + 2 in. = 18 inches Text page 412

Produce 110 tons per hour of limestone rock. Try a 24 X 36 in. crusher with a 3 in. closed setting, 114 tph Table STEP 1 Select a Jaw Crusher

Fig. 14.5, read down the 3” line to the size. Percent passing is on the left side of the figure. STEP 2 Size Distribution

STEP 3 Output Ranges

 100%  110 tph Always check your numbers, percentages must equal 100. Input must equal output. STEP 3 Output Ranges

STEP 4 Select a Roll Crusher The roll crusher must handle 29.7 plus its own return feed. See discussion page 430.

STEP 4 Select a Roll Crusher The roll crusher must handle 29.7 plus its own return feed. Maximum size from the jaw crusher  3 in.

STEP 5 Roll Diameter Try a 2 in roll crusher setting. Radius (R) of the rolls = ? C, roll setting = 2 in. A, maximum feed-size feed = 3 in. Equation 14.1

STEP 5 Roll Diameter The roll diameter must be at least 23.5 in. and the crusher must handle 34.9 tph. Table 14.6 Try a 24 X 16 crusher with a 2 in. closed setting tph. The first number indicates the diameter of the rolls.

STEP 6 Roll Crusher Size Distribution Fig. 14.5, read down the 2” line to the size.

STEP 7 Roll Crusher Output Ranges  100%  29.7 tph

STEP 8 Combined Output  110 tph 100%

STEP 9 Check Requirement ok