一、概述

砂金礦中除含金外、另含多種重礦物、與金伴生常見的有磁鐵礦、鈦鐵礦、金紅石、鋯英石、赤鐵礦、鉻鐵、鉑、銥、辰砂、鎢、錳、錫、金剛石、剛玉、方鉛礦等重礦物含量1—3kg/m3。其余為礫石、卵石和泥土。泥土在選金中不利回收細粒金。選別過程中應設法碎解、篩分、脫泥。重礦物元素只要上指標應考慮綜合回收工藝。砂金品位正常在0.3—10g/t,粒度0.2—2mm，形狀為粒狀、片狀、枝狀、針狀等。選礦原則優先采用重選法，繼而考慮綜合回收其他重礦物，可采用重、浮、混汞、磁選等聯合作業彼此分離各種礦物。

二、選金工藝設備

砂金選礦設備及工藝多種方式：離心選礦機、圓錐選礦機、跳汰機、螺旋溜槽、搖床、固定溜槽、振動溜槽等配套。

據多年設備使用反饋，選礦穩定性較好的是采用砂金雙層組合溜槽、生產能力大、成本低、占地面積小、可拆裝搬動、移動性強。粗選回收率80—85% 、精選回收率90—95%。

生產過程：用推土機、挖掘機，將砂金原礦送入篩機碎解、分級脫泥后，≤60mm礦石送入溜槽的供礦箱，以大量高壓水噴沖礦砂，充分洗選下，礦漿流入帶有篩孔的臺板上篩選，20-60mm礦石進入溜槽中間槽選礦。

篩下產品≤20mm礦砂被分配到下層兩側溜槽、槽底設有格條及氈墊，礦漿流經格條氈墊時，按密度和粒度進行分層，金粒及重礦物被富集在氈墊上，溜槽上設立防盜門鎖，換班清理氈墊時，由專人開鎖。清理出來的精礦轉入振動溜槽精選，經搖床分離金砂及其他重礦物，化學處理后送冶煉爐出品。

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.