EQP-01 through EQP-04 — Primary and secondary crushing train
Raw material from the seven UCIC quarries (Othman, Factory Quarry, Al-Juhfa, Al-Jamoum, Al-Shumaisi, Umuq, East Tufail) is delivered by CAT 777 haul trucks to the primary dump hopper. The material then progresses through the Apron Feeder, Wobbler Feeder, and Impact Crusher for primary size reduction. A separate Clay Roller Crusher handles the sticky, high-moisture clay fraction that would clog other crusher types. All crushed product is stored in a segmented warehouse feeding the raw mill proportioning system.
The apron feeder is a heavy-duty chain-and-pan conveyor that extracts material from the dump hopper at a controlled, uniform rate. Its overlapping manganese steel pans form a continuous, interlocking bed that supports the full weight of the material column. The VFD adjusts chain speed based on crusher motor amp feedback: rising amps reduce speed to prevent crusher choke; falling amps allow speed increase to maximize throughput. The overlapping pan design prevents fine material leakage and absorbs the extreme impact loads from direct truck dumping (up to 50-tonne payloads dropped from 2-3 meters). Material discharge at the head end occurs when the pans rotate over the head sprocket and the material bed loses support, falling onto the downstream wobbler feeder.
The wobbler feeder uses an eccentric shaft to generate elliptical motion in its rotating discs. Material is tumbled forward by the oscillating motion while fines settle to the bottom through the Brazil nut effect (granular convection). The fine material passes through gaps between rotating discs, achieving a scalping rate of 25-35% of total feed, while oversize material travels forward and discharges to the impact crusher. This fines bypass reduces crusher power consumption by 15-20% and extends blow bar life proportionally. The graduated disc spacing (60 mm at the feed end, widening to 100 mm at the discharge end) optimizes fines removal while minimizing oversize bypass into the fines stream.
Operating Principle: Electrical energy from the motor is converted into rotational kinetic energy in the massive rotor assembly. The four blow bars, traveling at 30-50 m/s tip speed, strike the falling feed material from the wobbler feeder. The collision causes instantaneous tensile fracture: a stress wave propagates through the rock at 4,000-6,000 m/s along grain boundaries and pre-existing microcracks. The fragmented material is then thrown against the two adjustable breaker plates at near-blow-bar velocity for secondary and tertiary impact. The grinding path (the crescent-shaped space between rotor and breaker plates) contains material in a multi-event impact zone until particle size falls below the breaker plate gap setting. The reduction ratio reaches 15:1 to 25:1, far exceeding a jaw crusher's 4:1 to 8:1. Product exits through the unrestricted bottom opening — once material is reduced below the gap setting, it discharges immediately. Product is cubical with minimal flats, optimal for downstream processing.
Two counter-rotating rollers (R1 counterclockwise, R2 clockwise at 80-150 RPM) draw sticky, wet clay into the crushing zone through friction at the nip point (nip angle 16-24°). Roller 1 is fixed; Roller 2 is mounted on slide rails and positioned by two hydraulic cylinders with position transducers. The 50 mm gap is maintained by hydraulic pressure with accumulator float: when a hard inclusion enters, the accumulator absorbs the displacement, allowing momentary roller retraction before returning to the set gap. The 160-tonne hopper provides 30 minutes of surge capacity, decoupling quarry operations from the crushing process. The self-cleaning roller profile features axial grooves that provide additional traction for wet clay while preventing material adherence to the roller surface.
Crushed material from the impact crusher (≤10 cm) and clay roller crusher (≤80 mm) is conveyed to a segmented storage warehouse. Each compartment holds a specific material grade corresponding to the five raw mill feed bins: two marble grades (from Othman and East Tufail), one iron ore blend (from Al-Jamoum, Al-Shumaisi, Umuq), gypsum (from Al-Juhfa), and corrective material (from Factory Quarry). The warehouse is integrated with the raw mill proportioning system: belt feeders beneath each compartment extract material at controlled rates determined by the raw meal chemistry target.