一、概述

砂金矿中除含金外、另含多种重矿物、与金伴生常见的有磁铁矿、钛铁矿、金红石、锆英石、赤铁矿、铬铁、铂、铱、辰砂、钨、锰、锡、金刚石、刚玉、方铅矿等重矿物含量1—3kg/m3。其余为砾石、卵石和泥土。泥土在选金中不利回收细粒金。选别过程中应设法碎解、筛分、脱泥。重矿物元素只要上指标应考虑综合回收工艺。砂金品位正常在0.3—10g/t,粒度0.2—2mm，形状为粒状、片状、枝状、针状等。选矿原则优先采用重选法，继而考虑综合回收其他重矿物，可采用重、浮、混汞、磁选等联合作业彼此分离各种矿物。

二、选金工艺设备

砂金选矿设备及工艺多种方式：离心选矿机、圆锥选矿机、跳汰机、螺旋溜槽、摇床、固定溜槽、振动溜槽等配套。

据多年设备使用反馈，选矿稳定性较好的是采用砂金双层组合溜槽、生产能力大、成本低、占地面积小、可拆装搬动、移动性强。粗选回收率80—85% 、精选回收率90—95%。

生产过程：用推土机、挖掘机，将砂金原矿送入筛机碎解、分级脱泥后，≤60mm矿石送入溜槽的供矿箱，以大量高压水喷冲矿砂，充分洗选下，矿浆流入带有筛孔的台板上筛选，20-60mm矿石进入溜槽中间槽选矿。

筛下产品≤20mm矿砂被分配到下层两侧溜槽、槽底设有格条及毡垫，矿浆流经格条毡垫时，按密度和粒度进行分层，金粒及重矿物被富集在毡垫上，溜槽上设立防盗门锁，换班清理毡垫时，由专人开锁。清理出来的精矿转入振动溜槽精选，经摇床分离金砂及其他重矿物，化学处理后送冶炼炉出品。

Placer gold processing equipment

1. General

Placer Gold contains a number of heavy minerals in addition to gold and is commonly associated with magnetite ,ilmenite, rutile, zirconium quartz, hematite, ferrochrome, iridium, cinnabar, tungsten, manganese, tin, diamond, corundum, calcite and other heavy minerals with its content being 1-3ktg/m3 as well as gravel, cobble and soil. Presence of soil is not favorable for recovering fine gold in the process of gold dressing. Efforts should be made to conduct breaking, screening and desliming operations in the period of separation. Consideration should be given to comprehensively recovering the heavy metal elements with desirable indexes available. Normally, placer gold occurs in granular, flaky, branched and needle shapes with 0.3-10g/t in grade and 0.2-2mm in size, Preference should be give to gravity concentration in ore dressing. Also, consideration should be given to comprehensively recovering other heavy minerals by combined use of gravity, flotation, amalgamation, magnetic separation processes to separate minerals.

2. Process equipment for processing placer gold

Placer gold dressing equipment and process are available in a number of types: centrifugal separator, cone separator and jig complete with spiral chute, table, stationary chute, vibrating chute and others.

Feedbacks from customers for the equipment application over years show that relatively stable in ore dressing is to introduce placer gold two-layer combined chute with large production capacity , low costs. less use of land , mountingability and dismountingability, removability. Recovery rate for roughing is 80 – 85% and recovery rate for cleaning 90 –95%.

Production Process: Run-of-mine placer gold is hauled by bulldozer and excavator into screening machine for breaking, classification and desliming prior to being delivered into ore box of chute, where placer gold is flushed with a large quantity of high pressure water and after being subject to full washing, slurry will flow into sieve-mesh plate and a fraction of 20 – 60 mm size of ore is fed into intermediate cell of the chute for processing.

Undersize product with a fraction of ≤20mm placer is distributed to the chutes at two sides of the lower layer with the chute bottom provided with lattice bar and felt mat. When slurry flows through the lattice bar and the felt mat, stratification is performed in density and grain size. Gold grain and heavy minerals are concentrated on the felt mat and the chute is provided with theftproof door lock. When a shift is changed for cleaning the felt, the lock will be opened by an assigned person. The concentrate cleaned out is transferred into the vibrating chute for cleaning and placer gold and other heavy minerals are separated out using table before being subject to chemical treatment for delivery to smelting furnace for production.