This report details the two-stage processing route designed to convert run-of-mine bauxite from Guyana into ceramic proppants at a Louisiana facility.
Report context
This technical report, dated August 4, 2015, describes the recovery methods for the First Bauxite Project. Material processing to produce refractory proppants occurs in two stages at two separate locations. Preparation of mined raw bauxite ore ready for shipping is undertaken in Guyana at the Sand Hills property located approximately 23km from the Bonasika mine. Processing of the raw ore to create the final proppant products is carried out at the facility located within the Port of South Louisiana's Intermodal Facility (GlobalPlex) located near Laplace, Louisiana, USA.
Processing route
Guyana: Sand Hills preparation plant
The Sand Hills process plant is designed to prepare run-of-mine bauxite ore for shipment to the Louisiana processing facility. The unit processes are raw ore stockpiling, crushing, drying, and ore storage and ship loading.
The Sand Hills process plant was designed for a nominal plant treatment rate of 1,212 tonnes per day (on a 4 x 24 hour work week) at an average annual production rate of 232,000 dried tonnes per year.
Ore is transported from the mine in haul trucks and rear-end dumped at the ROM ore stockpile, segregated by ore type and chemistry into individual piles. An apron feeder feeds a two stage crushing circuit and crushed ore is deposited onto the crushed ore stockpiles via a radial stacker. Crushing is conducted in campaigns by ore type in order to maintain segregation and minimize cross contamination.
Reclaimed crushed ore is dried in a counter-current rotary dryer, direct heat fired with diesel oil. The dryer is designed to dry the ore to a moisture content of approximately 6%. Dried ore is stockpiled in a covered storage shed to protect it from the elements until shipment to Louisiana.
The dried ore storage shed has capacity for two separate dry ore stockpiles, each of nominal 6,000 tonnes capacity plus a spare stockpile. A Front End Loader reclaims ore from the dried ore stockpile and feeds a ship loader via a transfer feed conveyor. The ship loading transfer conveyor is equipped with a "for trade" dual beam weightometer and a cross stream linear sampler. Maximum turn-round time for each ship has been estimated at 24 hours.
Crushing circuit details
The crushing circuit consists initially of a McLanahan 36 x 36 inch heavy duty double roll primary crusher followed by a McLanahan 24 x 36 inch heavy duty double roll secondary crusher. These crushers are self-classifying so there is no need for a classification stage between them. Auxiliary equipment includes a tramp iron magnet on the feed conveyor to the secondary rolls crusher and a weightometer on the secondary rolls crusher discharge conveyor.
Drying circuit details
Reclaimed ore is fed to a 50 foot long by 6 foot diameter, counter-current direct heat, rotary dryer fired by diesel oil. The operation of the dryer is set to provide ore for storage with a moisture content of approximately 6%, deemed optimum for minimal dust production and safe shipping. Dryer discharge is deposited in a covered dried ore storage shed via a bucket elevator and tripper conveyor.
Louisiana: Proppant production plant
The Louisiana processing plant is designed to process the raw bauxite delivered from the Sand Hills preparation plant into proppants. While focus has been given to two products, 20/40 mesh ISP and HSP, the plant is designed to be flexible enough to produce various grades and product sizing to match market trends.
The plant consists of standard unit processes: ore in-loading, calcination, comminution, agglomeration, sintering, and product storage and load out.
Raw bauxite in-loading and storage
Crushed and dried raw bauxite ore is delivered by ocean going bulk carriers in 6,000 tonne shipments. Ore is removed from the ship with a clamshell type bucket excavator and loaded into road going haul trucks for transport from wharf to plant. The transport trucks empty their loads into an in-loading dump hopper accessed by driving up a ramp and over a static grizzly. Ore is sent to the feed ore stockpile building via two elevated belt conveyors and deposited into discrete piles via a tripper conveyor.
Raw bauxite in-loading is undertaken in campaigns by ore type. The storage shed has two main stockpiles with capacity of 8,700 tonnes for DFB and RGB ores respectively. An additional bay allows for either two smaller stockpiles or another full shipload.
Calcination
A Front End Loader reclaims ore from the feed ore stockpiles and feeds the calcination process. Reclaiming raw ore is undertaken according to a recipe dictated by the predetermined proportion of ore types.
Calcination is performed in a Multi-Hearth Furnace which drives off remaining moisture and other volatiles with temperatures in the various hearths ranging as high as 950 degrees C. The MHF is capable of hearth temperatures as high as 1,150 degrees C, burns natural gas, and offers the benefit of strict temperature control while using less gas than traditional rotary kilns.
The MHF discharges hot product into a water cooled Rotary Cooler. Dust generated in the MHF is captured from off-gases in a dust collector and returned to the calciner.
Comminution
The Louisiana milling circuit includes primary grinding of freshly calcined ore and regrinding of recycled materials; both grinding processes are dry.
Calcined material discharging from the calcining rotary cooler is fed to a calcined product screen. A screw conveyor sends screened product through a hammer mill on its way to the primary grinding feed surge bin.
The primary grinding mill is an air swept ball mill that grinds material to a target product P90 size between 32 and 34 microns. A P80 product size of 20 microns was used for design. A large dust collector fan pulls material from the mill through a motorized cyclone where material is classified by size. Oversize particles flow back to the ball mill feed chute while product sized material is pulled into a dust collection baghouse.
The regrind mill is an air swept vertical impact mill. The regrind circuit acts as a collection point for several waste streams in the post calcining portion of the plant, serving to blend and homogenize the various waste streams prior to being added to the agglomeration circuit.
Agglomeration and drying
The agglomeration circuit has two main goals: to accurately measure out the specific formulation ingredients given the significant proportion of recycled material used, and to achieve the correct formation and sizing of the proppant pellets.
Correct recipe measures are accomplished using batching vessels which individually weigh the precise amount of each material before they are added to the agglomeration mixers. The agglomerated granules are dried in a fluid bed drier and screened to reject particles that are either too large or too small. Out of spec material is sent back to the regrind circuit while finished pellets report to the sintering circuit.
Sintering
The sintering circuit removes any remaining moisture and LOI from the dried green proppants and sinters the pellets to the density and hardness required by the product specifications. The sintering circuit consists of a rotary sintering kiln and a rotary cooler, along with dust collectors for each of the head and tail ends of the kiln.
The refractory lined kiln shell is 65 meters long and 3.67 meters in diameter and rotates on steel tires supported by three concrete piers. Kiln speed is around 1.0 rpm but adjustable from 0.5 to 10 rpm. It is a direct fired, counter current heating unit fuelled by natural gas. Sintered proppants pass directly from the sintering kiln into a rotary cooler, which is a recuperative, multi-tube design using indirect water contact to cool bulk materials.
Final product handling
The final product handling circuit includes sintered proppant polishing and final product screening. The circuit polishes the proppants to improve their sphericity and roundness and performs a final size classification. Out of spec granules are sent back to the regrind circuit while finished proppants are conveyed to product storage silos.
Product load-out is possible by two methods: bulk transport trucks loaded directly from storage silos, supplying barges at the wharf or rail cars; or bagged product stored in inventory for container or flat-bed truck shipment.
Key reported parameters
| Parameter | Units | Design Value |
|---|---|---|
| Guyana plant annual throughput | t/a | 232,000 |
| Guyana plant availability | % | 92 |
| Guyana operating days per week | days | 4 |
| Guyana daily throughput | t/d | 1,212 |
| Crushing circuit design capacity | tph | 150 |
| Crushing circuit availability | % | 70 |
| Crusher product size P80 | mm | 40 |
| Drying circuit design capacity | tph | 85 |
| Drying circuit availability | % | 92 |
| Dryer product moisture target | % | 6 |
| Ship loading circuit design capacity | tph | 400 |
| Shipment size to Louisiana | tonnes | 6,000 |
| Ship loading duration maximum | hours | 24 |
| Louisiana annual proppant production | t/a | 158,000 |
| Louisiana daily production | t/d | 472 |
| Louisiana hourly production | t/h | 19.7 |
| Louisiana plant availability | % | 92 |
| Louisiana operating days per week | days | 7 |
| Primary ball mill capacity | t/h | 40 |
| Primary ball mill product size target P90 | microns | 32-34 |
| Primary ball mill product size design P80 | microns | 20 |
| Regrind impact mill capacity | t/h | 40 |
| Regrind impact mill product size design P80 | microns | 20 |
| Agglomeration mixer capacity | t/h | 45 |
| Agglomeration product sizing target | mesh | 16/30 |
| Agglomeration product moisture maximum | % | 25 |
| Fluid bed dryer capacity | t/h | 40 |
| Fluid bed dryer feed moisture | % | 25 |
| Fluid bed dryer product moisture | % | 3 |
| Polishing circuit throughput | t/h | 20 |
| Polishing batch size | t/h | 5 |
| Polishing batch time | min | 15 |
Project website: https://www.911metallurgist.com/blog/bauxite/
*Note: Calcination and sintering parameters were included in technology provider input and not reproduced in this report.*
Technical qualifications
The report presents a proposed design based on process design criteria. The Sand Hills plant was designed for a nominal plant treatment rate; the Louisiana plant is designed to process raw bauxite delivered from Guyana. While direct feed bauxite ore sales from Sand Hills are mentioned, no specific additional facilities are described to support this activity.
The report notes that some areas, specifically calcination and sintering design criteria, were provided by technology providers and are referenced in a separate section (Section 13) not included in this recovery methods description. The report does not present testwork data or historical operating data for the designed facilities; it describes design parameters and a planned process flowsheet.
Source: First Bauxite Project , 2015 Recovery Methods Technical Report, Sections 1.16, 1.17, and 17, dated August 4, 2015.
