Rock Gold Spiral Classifier Grinding Closed Circuit

Product Description

Rock gold deposits in Mozambique are primarily quartz vein type, with gold minerals often associated with sulfides such as pyrite. Some gold is disseminated as fine and micro-fine particles in hard quartz veins. This ore characteristic requires that the beneficiation process precisely control the grinding fineness – if the grind is too coarse, gold minerals are not fully liberated; if too fine, sliming occurs and gold is lost.

The closed circuit formed by a spiral classifier and ball mill is the key to controlling this fineness. The FG-24 high-weir single spiral classifier is suitable for coarse grinding classification, stably controlling grinding fineness between 65% and 80% passing 200 mesh, ensuring full liberation of gold minerals and creating optimal conditions for subsequent gravity separation or flotation operations.

Large capacity, matching medium to large concentrators: The FG-24 has a sand return capacity of 3,240–5,400 tons/day and an overflow capacity of 580 m³/h, sufficient for medium to large rock gold concentrators in Mozambique processing 500–1,000 tons/day, without the need for multiple units in parallel.

Closed-circuit grinding, precise control of flotation/gravity feed size: In closed circuit with a ball mill, it stably controls grinding fineness at 65%–80% passing 200 mesh, ensuring full liberation of gold minerals and significantly improving flotation or gravity recovery.

Simple structure, low maintenance cost: The submerged end of the spiral shaft and the shaft head use cast iron sleeves, which are wear-resistant and durable. The lifting device is available in electric and manual versions, adapting to local power supply conditions in Mozambique. The machine has no complex hydraulic or pneumatic systems, so local maintenance workers in Mozambique can quickly master the maintenance skills.

Integrated desliming and dewatering, multi-function: Besides particle size classification, the spiral classifier also performs slurry desliming and dewatering. When processing rock gold ore with high clay content in Mozambique, it can separate slime in advance, reducing interference in subsequent flotation or gravity separation processes.

 

Power-free classification, significant energy saving: The spiral classifier works on the principle of gravity settling of slurry, consuming no additional power beyond a 15 kW motor to rotate the spiral shaft. Compared to a hydrocyclone system (which requires a slurry pump to provide pressure energy), it saves considerable electricity costs over long-term operation.

Adapts to ore property fluctuations, stabilizes production: Mozambique rock gold ore comes from diverse sources with wide grade fluctuations. The spiral classifier's performance is insensitive to variations in feed quantity and density, providing relatively stable overflow particle size and ensuring consistent feed for downstream operations.

Low investment cost, high cost-effectiveness: Compared to a hydrocyclone system, the spiral classifier requires no supporting slurry pump, valves, or automatic control system. The unit price and maintenance costs are significantly lower, making it particularly suitable for small and medium-sized concentrators in Mozambique with limited capital.

Low energy consumption, aligns with Mozambique's green mining direction: Mozambique's mining regulatory authorities have clear requirements for energy consumption and wastewater discharge in mineral processing. The closed circuit of the spiral classifier allows tailings water to be returned to the mill for recycling, reducing wastewater discharge. The low energy consumption (only 15 kW) also aligns with Mozambique's policy direction of reducing processing costs and pursuing green development.

Packaging	Carton, wooden box, iron frame or customized
Shipping	Sea transport, land transport, air transport, etc
Port	Xiamen, Shenzhen, Qingdao, Ningbo, etc

Jiangxi Changyi Mining Machinery Co., Ltd.

 It is a professional mining machinery manufacturer with more than 10 years of experience led by a young team, providing a full range of processing equipment for gold, tin, tungsten, iron, diamond,coltan,silica sand, zircon sand, black sand, chromium, etc.

Main products: shaker, ball mill, drum sand washer, spiral sand washer,spiral chute, jig, centrifugal concentrator, vibrating
screen, drum screen, jaw crusher, hammer crusher, flotation machine, spiral classifier, magnetic separator, etc. and a full range of small laboratory mining equipment and alloy bearings.

Main markets: Africa, South America, Europe, Southeast Asia, Asia, etc. Our cooperative customers cover Congo, Ghana, Uganda,South Sudan, Israel, Pakistan, Mozambique, Suriname, Zambia, Nigeria, Cameroon, Malaysia, Indonesia, South Korea, Philippines,Mongolia,Singapore, India, Iran, Mexico, Brazil, Chile, Peru, Spain, Canada, Australia, the United States, the United Arab Emirates, etc.

Tanzania Exhibition

Customer visit

1. Why use a spiral classifier for a Mozambique rock gold concentrator? Isn't a hydrocyclone more efficient?

Answer: A hydrocyclone does have higher classification efficiency, but it requires a slurry pump to provide pressure energy and is sensitive to fluctuations in feed pressure and density. Medium to large concentrators in Mozambique have diverse ore sources and wide grade fluctuations. Using a hydrocyclone can easily lead to "coarse particles in overflow" or "over-grinding". The spiral classifier has a simple structure, is insensitive to feed fluctuations, and has low maintenance requirements, making it more suitable for the actual production conditions of Mozambique rock gold concentrators. Moreover, in rock gold projects across Africa (Ethiopia, Kenya, Ghana, etc.), spiral classifiers are a mature and mainstream configuration.

2. How exactly does the FG-24 spiral classifier work in rock gold beneficiation?

Answer: The FG-24 spiral classifier forms a closed-circuit grinding system with a ball mill. The slurry discharged from the ball mill enters the middle of the classifier trough. Under gravity, coarse particles quickly settle to the bottom and are conveyed upward by the spiral blades along the trough slope to the sand return port, returning to the ball mill for regrinding. Fine particles rise with the slurry to the overflow weir and are discharged as qualified overflow, entering subsequent gravity separation (e.g., jigs, centrifuges) or flotation systems. In a gravity separation process, the classified slurry can directly enter a jig to recover coarse gold, with jig tailings then going to a centrifuge to recover fine gold, and a shaking table for final cleaning.

3. What classification particle size can the FG-24 spiral classifier achieve? Is it suitable for the flotation/gravity requirements of Mozambique rock gold ore?

Answer: The overflow fineness of the FG-24 high-weir spiral classifier is typically controlled between 65% and 80% passing 200 mesh. The beneficiation requirement for Mozambique quartz vein rock gold ore is generally 70%–80% passing 200 mesh, which is well within the controllable range. If the Mozambique ore has a finer dissemination size requiring a finer classification size, a submerged spiral classifier can be used, or the FG-24 can be combined with a hydrocyclone to form a two-stage class

 
4. What is the processing capacity of the FG-24 spiral classifier? Is it sufficient for medium to large concentrators in Mozambique?
Answer: The FG-24 spiral classifier has a sand return capacity of 3,240–5,400 tons/day and an overflow capacity of 580 m³/h. Medium to large rock gold concentrators in Mozambique typically process 500–1,200 tons/day, so the FG-24 is fully sufficient without the need for multiple units in parallel. For example, a 1,200 t/d gold-copper concentrator in Namibia uses a closed-circuit grinding-classification process consisting of a grate ball mill and a high-weir single spiral classifier.
  
5. What daily maintenance does the FG-24 spiral classifier require? Is the maintenance cost high?
Answer: Maintenance cost is not high. Core maintenance includes:
Daily: Inspect wear on spiral blades and trough liners; check the reducer oil level; lubricate all grease points once.
Monthly: Clean trough bottom deposits; inspect wear on the lower support bearing and seals.
Every 6 months: Replace the reducer oil.
Overhaul schedule: Minor repair every 2–3 months, medium repair every 16 months, major repair every 48–60 months.
Spiral blades are generally replaced every 6–12 months, and trough liners every 12–24 months. A local maintenance worker in Mozambique can be trained to perform all maintenance tasks in a short time.

6. Is it convenient to purchase spare parts locally in Mozambique? Is there a recommended spare parts plan?
Answer: Core wear parts for the spiral classifier include spiral blades, trough liners, bearings, and seals. Some common parts are available in local mining equipment markets in Mozambique (e.g., Beira, Maputo). It is recommended to order 1–2 sets of spiral blades and liners as spares when purchasing the equipment to avoid production interruptions due to import lead times. Additionally, when selecting the equipment, you can request the manufacturer to provide upgraded polyurethane bearing seats or steel bushings, extending bearing seat life to 3–6 months and steel bushing life to 8–12 months, reducing spare parts replacement frequency.

7. How effective is the FG-24 spiral classifier in actual application in Mozambique?
Answer: Although public case studies from Mozambique are limited, the FG-24 spiral classifier has been maturely applied in rock gold projects in several African countries:
Ghana: A Φ3.2×4.5m overflow ball mill formed a closed circuit with an FG-20 high-weir spiral classifier, controlling grinding fineness at 75%–80% passing 200 mesh. The spiral classifier provided stable sand return, effectively avoiding over-grinding or under-grinding, ensuring feed quality for subsequent gravity separation, and achieving a total gold recovery consistently above 92%.
Ethiopia: A 500 t/d rock gold mine used an overflow ball mill and a spiral classifier in closed circuit, controlling grinding fineness at 78%–82% passing 200 mesh. The spiral classifier significantly reduced over-grinding.
Kenya: A closed circuit consisting of an overflow ball mill and a spiral classifier ground the ore to >85% passing 200 mesh. The classifier promptly separated qualified particles, creating an efficient grinding cycle.ification process: "classifier for coarse classification + hydrocyclone for fine classification".