What is iron ore beneficiation—gravity beneficiation

Gravity beneficiation is referred to as gravity separation. Gravity separation is also one of the important beneficiation methods for selecting iron ore, especially weakly magnetic iron ore. Generally it can be divided into heavy media beneficiation, jig beneficiation, bed beneficiation and chute beneficiation. Heavy media beneficiation and jig beneficiation are mainly used in iron ore beneficiation plants in my country to separate qualified tailings under coarse-grained conditions, and the obtained coarse concentrate is then processed. Shaking table mineral processing has high separation accuracy and large enrichment ratio, but it has low processing capacity per unit area and a large floor area. It is used in some mineral processing plants to recover weakly magnetic iron minerals, and is not widely used. Spiral chute is widely used in my country’s iron ore beneficiation plants to obtain coarser-grained qualified concentrates. Centrifugal concentrators have also been used to deal with fine-grained materials. The gravity separation process has low operating costs and little pollution to water, soil and surrounding environment, and has attracted great attention.
A heavy media mineral processing
Heavy medium mineral processing equipment includes heavy medium vibrating chute, cylindrical and conical heavy medium mineral concentrator, heavy medium cyclone and heavy medium vortexer with a lower separation limit of 0.5mm. The heavy medium vibrating chute was first developed by the Swedish Stripa mineral processing plant in 1953. It is used to sort mixed ores of hematite and magnetite. The specification is 1000mm x 5500mm, and the processing capacity is 30~50t/h. With a raw ore grade of 40.40%, the technical indicators include a concentrate yield of 50.31%, a grade of 62.80%, an iron recovery rate of 78.20%, and a tailings grade of 17.73%. Sweden’s Strassa mineral processing plant (Strassa) processes mixed ore of magnetite and hematite. The +8mm ore after crushing is processed by a 1250mm x 6000mm heavy medium vibration chute. Iron ore, recycled. The Sunrise concentrator in the United States processes earthy and massive hematite ore, and the gangue is mainly silica and alumina. Two 2440mm x 2440mm cylindrical heavy media concentrators are used to process ores of 125~38mm and 38~6.4mm respectively. The heavy medium is 0. 2mm ferrosilicon, and the separated light products are discarded. The Sishen concentrator in South Africa processes high-grade hematite ore, which is mixed with soft shale and a small amount of striped low-grade iron-bearing ore and thin-layered sandstone, as well as waste rock mixed in during the mining process. After the ore enters the concentrator, it is crushed and screened into three grades: 90~32mm, 32~6mm and 6~0mm; the first two grades use a cylindrical heavy media concentrator, and the latter grade uses a heavy media cyclone. The medium for sorting is ferrosilicon, the light product is tailings, and the heavy product is concentrate with a grade of 67%.
In 1966, my country first used heavy-medium vibrating chute and heavy-medium cyclone to sort weakly magnetic iron ore at the Baimiao Ore Concentrator of Longgang Iron and Steel Co., Ltd. The heavy medium vibrating chute is 400mm The technical index of the tailings grade is 14.12%; the heavy medium is hematite concentrate with a grade of 56%. Using a φ350mm heavy medium cyclone to process 10~2mm materials, when the ore grade is 32.45%, the obtained concentrate grade is 47.95% and the tailings grade is 14.56%. Fenghuangshan mineral processing plant adopts a 400mm After the 75-12mm raw ore is first separated by a dry magnetic separator in the Meishan Iron Ore Concentrator, the tailings are separated using a 400mm x 5000mm heavy medium vibrating chute. The heavy medium is magnetite concentrate, and the ore grade is 30.71% At that time, the concentrate grade was 42.77%, the iron recovery rate was 48.28%, and the tailings grade was 24.31%. In addition, the Meishan Iron Ore Concentrator has conducted a φ300mm heavy medium cyclone test. The heavy medium is pyrite concentrate, and the ore particle size is 20~2mm. When the ore grade is 46.72%~48.39%, the concentrate The ore grade is 49.98% ~51.69%.
B Jig dressing
There are many types of jigs for iron ore separation. The ones developed in my country include trapezoidal jigs, rectangular jigs, re-vibration jigs and large-grained jigs. Meishan Iron Ore Concentrator uses the YMT-75 large-grained jig to sort ore of 50~12mm in production. When the ore grade is 27.59%, the concentrate grade is 41.41% and the recovery rate is 57.49%. The 2LTC-79-4 rectangular jig has been used to select 12 ~ 2mm particle size ore. When the ore grade is 40% ~ 45%, the concentrate grade is 51%, the tailings grade is 20% ~ 25%, and the concentrate is recycled The rate is 60% ~ 66%; when sorting 2 ~ 0mm particle size ore and the feed grade is 35%, the concentrate grade is 50%, the recovery rate is 32%, and the tailings grade is 23% ~ 25%. Jig is mainly used in iron ore concentrator to select qualified tailings and obtain coarse concentrate.
C Shaking table mineral processing
The general particle size range of shaker mineral processing is 0.037 ~3mm. When the Aoshan mineral processing plant was put into operation in 1965, it used a combined magnetic-gravity process to process surface oxidized ores, and the gravity separation equipment was a double-connected three-layer sieve bed. Practice showed that the separation effect was poor, and it was later replaced by strong magnetic separation. In recent years, the bed has been used as an auxiliary equipment to recover weakly magnetic iron minerals when processing mixed iron ore in individual iron ore concentrators. Kunming Iron and Steel Dahongshan Iron Ore Concentrator processes magnetite-hematite mixed ore and adopts a weak magnetic field-strong magnetic field-flotation combined process. The flotation feed is secondary strong magnetic concentrate. Due to various reasons, the separation effect is poor. Now it is changed to a combination of chute and grinding bed. 102 cloud-tin type grinding beds are used. When the ore grade is 46.93%, A concentrate with a yield of 29.67%, a grade of 58.25%, and a recovery rate of 70.27% was obtained. When processing hematite ore, the ore dressing plant of Zhongshan Mining Company of Hesteel Group uses 16 cloud-tin-type fine sand grinding beds – groups – to separate the middle ore in spiral chute to obtain concentrate with an iron grade of about 60%.
D Laocao mineral processing
The equipment that belongs to chute mineral processing includes spiral concentrator, spiral chute, vibrating spiral chute, belt chute, turning bed, centrifugal concentrator, etc. Spiral concentrators, spiral chutes and centrifugal concentrators are used in iron ore beneficiation.
a Spiral concentrator and spiral chute
Spiral concentrators are used to process medium and coarse-grained materials abroad, and are most commonly used in Canadian iron ore concentrators. The Wabush mineral concentrator processes quartz-type weakly magnetic iron ore containing specular iron ore. The ore particle size is 0.84 ~ 0mm. It uses five rubber-lined Humphrey type spiral concentrators, one coarse and one fine. When the ore grade is 35%, the concentrate grade is 64%. Our country began to develop spiral concentrators in 1955, with a diameter of 600mn and two heads, three heads and four heads respectively. When the ore was separated and washed overflow at Magang Gushan Mining Company and Lushan Concentrator, the ore grade was 41.70%, and it was obtained The concentrate grade is 56.78% and the iron recovery rate is 75.36%.
Since most of my country’s weakly magnetic iron ores are fine-grained or micro-grained, the selected ore has a fine particle size and a spiral concentrator with a composite elliptical spiral cross section. The water layer is deep and the separation effect is poor. In the mid-1970s, a spiral chute was developed. Its cross-sectional shape is a cubic parabola. The bottom of the spiral chute is almost flat. The water layer is shallow. The ore particle size suitable for processing is 0. 2 ~ 0.030 mm. There are many specifications and models. , the largest spiral diameter is φ2m, and the diameters φ1. 2m and φ1. 5m are commonly used in iron ore dressing plants. There are more than a thousand units used in the production of weak magnetic ore dressing plants in Anshan area alone. In the combined process of stage grinding-coarse and fine separation-gravity separation-magnetic separation-anion reverse flotation, under the condition of relatively coarse grinding particle size (-0.074mm accounting for 55% ~70%), after classification, the spiral The chute separates, grades and settles sand to obtain coarse-grained qualified concentrate. For example, the overflow particle size of the grinding classification in the first section of the Dashan Iron Ore Concentration Plant in Qi is -0.074mm, accounting for 60% to 65%.
After cyclone classification, the sand settling grade is about 30%. A spiral chute is used to separate coarse, fine and sweep to obtain the technical indicators of a concentrate grade of 67%, a yield of 20%, and a total concentrate yield of more than 50%. , reducing the amount of ore in the next stage of grinding and separation operations, achieving the purpose of energy saving and consumption reduction, and the granulated concentrate is conducive to filtration. The spiral chute is the most widely used gravity separation equipment in iron ore concentrators.
b Centrifugal concentrator The centrifugal concentrator is developed by Yunnan Tin Company in my country and is used to select fine-grained tin ore. The generally suitable size range for separation is 0. 037 ~ 0. 010mm. In 1977, Anshan Iron and Steel Gongchangling Ore Concentrator adopted a combined magnetic separation and gravity separation process when selecting fine-grained magnet-hematite mixed ores. The gravity separation used 720 φ800mm x600mm centrifugal concentrators to process the concentrated weak magnetic tailings. After one coarse and one fine separation, 156 φ1600mm x900mm double-taper centrifugal concentrators were used to separate the fine part of the weakly magnetic tailings, obtaining a yield of 8%, a grade of 63.39%, and a recovery rate of 11.19%. The concentrates are now out of use due to the imperfections of the centrifugal concentrator itself at that time. In recent years, the centrifugal concentrator equipment itself has been greatly improved. In production, the centrifugal concentrator has been used to select fine-grained weakly magnetic iron ore. Dahongshan Iron Ore Concentrator of Kunming Iron and Steel Co., Ltd. has changed the secondary strong magnetic concentrate separation process based on the combination of chute and grinding bed to the combined separation process of centrifugal concentrator and grinding bed. When the ore grade is about 50%, the The centrifugal concentrator concentrate has a yield of 50% and an iron grade of 58% to 60%. Hainan Mining United Co., Ltd. uses a combined process of strong magnetic separation and centrifugal concentrator when processing Beisan weakly magnetic iron ore. In the continuous beneficiation test, when the ore iron grade was 52.88%, a centrifugal concentrator was used for rough separation, and the concentrate yield was 20.46%, the crystal position was 65.59%, and the operating recovery rate was 25.37%; when the ore grade was 52.11%, a rough separation was used The centrifugal concentrator performs one-time separation, with a concentrate yield of 36.59%, a grade of 61.78%, and an operation recovery rate of 43.38%.