《武汉工程大学学报》 2017年06期
529-535
出版日期：2017-12-30
ISSN:1674-2869
CN:42-1779/TQ
新磷矿选矿药剂的开发利用
Among various mineral processing methods，flotation is considered as the most widely used approach to separate phosphate from its impurities. There is no “one-for-all” process to separate phosphate from its impurities，because of the different characteristics of the ore body. So，the beneficiation process must be customized based on the different flotation response of the phosphate ores from different mines or locations. The typical flotation processes applied in phosphate industry include direct flotation，direct-reverse flotation，reverse-direct flotation，double reverse flotation，etc.. In direct flotation，phosphate is floated with fatty acid or soap collector，while the sink is discarded as waste. Direct flotation has been used in many regions of the world，such as Russia，South Africa and South America. In the phosphate industry in Florida U.S.A.，a double flotation process，known as the “Crago” process，is used. In this process，phosphate is recovered via direct rougher flotation followed by cleaner reverse flotation of silica. The direct-reverse flotation can also be applied for phosphate ores with both siliceous and carbonaceous impurities. In such a case，phosphate is floated with some carbonates using a fatty acid type collector at alkaline pH to reject siliceous waste. The carbonate impurities are separated from phosphate with or without a collector in acidic pH. For phosphate ores with siliceous and carbonaceous impurities，double reverse flotation process is also widely practiced. With double reverse flotation process，carbonaceous impurities are floated with a carbonate collector at acidic pH followed by floating silica using a cationic collector at neutral pH.As a world leader in mining chemicals，Arr-Maz has made great efforts in developing new reagents for processing different phosphate ores worldwide，including in China. In this paper，examples will be discussed to illustrate the application of Arr-Maz CustoFloat?(CF) and CustAmine? (CA) collectors for beneficiating different phosphate ores with various processes[1-5].1 Direct Flotation of Phosphate Ore1.1 A phosphate mine，Yunnan，ChinaThe phosphate ore from the mine is weathered rock with low MgO content. It contains about 22.48% P2O5 and 0.2%-1.0% MgO. In order to achieve good liberation，the ROM rock was ground to the size range of 90% passing 74 μm. Soda ash was used as pH modifier and sodium silicate was used as depressant. CustoFloat? Y623(CF-Y623) was used as a collector for phosphate flotation. The flowsheet of lab testing is shown in Fig. 1 and the flotation results are listed in Tab. 1.In 2009，a plant test was conducted at the Phosphate Mine，Yunnan，China and the plant test results are also given in Tab. 1. A phosphate concentrate with 30.03% P2O5 was achieved at 73.77% recovery from this low MgO weathered feed in plant test.1.2 Another phosphate mine，Yunnan，ChinaThe ROM rock from the phosphate mine contains about 23.36% P2O5 and 27.30% insol. A collector，CF-623A，was developed to float phosphate away from the major siliceous impurities for this feed and satisfactory flotation performance was achieved in plant test. Fig. 2 shows the open circuit of one stage rougher flotation with reagent conditions used in lab testing. Plant test was run with the flowsheet of one rougher，one scavenger and one cleaner. Lab and plant test results are summarized in Tab. 2.2 Reverse Silica Flotation Process2.1 Reducing silica content in concentrate product from ChinaThis is a concentrate product from east Yunnan，China with 32.13% P2O5 and 11.28% insol.. It is in size range of 80% passing 74 μm without desliming. In order to further lower the insol. content in the product，an amine collector，CA-2060A，was used and the material balance sheet in the flotation process is shown in Fig. 3.As can be seen from Fig. 3，CA-2060A could float some insol. out from this fine feed with the sacrifice of recovery. With two stage flotation，a final concentrate with 34.36% P2O5 and 5.73% insol. can be obtained at 81.3% recovery. This approach may be taken into consideration only if the product of high P2O5 grade and low insol. is needed. The tails from this float can be recycled back to the original concentrate product for general purpose，such as manufacturing SSP，TSP，etc. .2.2 Beneficiating high insol. phosphate feed from Africa with amine collectorThe samples received from Africa were prepared from the waste stock piles in an existing phosphate preparation plant. Based on the P2O5 content in the feed，the samples were identified as low grade，middle grade and high grade，respectively. The feed analysis is listed in Tab. 3. As can be seen from the feed analysis that all of the feed are associated with very high insol. content.Based on the characteristics of the rock，a cationic collector，CA-1611，was used to float silica out of the feed. The results with one step amine flotation are shown in Tab. 4. It can be seen from Tab. 4 that all the three feed can be easily upgraded to high P2O5 grade through single stage flotation at relatively low reagent consumption.3 Reverse Flotation of Carbonates3.1 Calcite flotation for phosphate ore from Middle EastThis phosphate ore contains about 50% phosphate，3% insol.，3% dolomite and 40% calcite. The ore was ground to pass 300 μm for good mineral liberation，and deslimed at 37 μm to remove low P2O5 grade slimes. In order to obtain a marketable phosphate concentrate from this feed，carbonate impurities，particularly calcite，must be rejected. For this purpose，a new carbonate collector，CustoFloat XT collector was developed.The feed was conditioned in acidic pH < 5.5 with phosphoric acid as pH modifier and depressant. After one step reverse flotation，the float was discarded as waste，and the sink was collected as concentrate. The collector dosages and flotation results are plotted in Fig. 4. We can see from Fig. 4 that a final concentrate with over 32% P2O5 and around 90% recovery can be obtained and the reagent dosage of the CustoFloatXT collector is only 1.2 kg/t.3.2 Dolomite flotation for phosphate ore from Yunnan，ChinaThe ore body has three recoverable phosphate beds with average P2O5 grade approximately 24%. The MgO content in the feed to the plant fluctuates widely from 6.5% to 9.0%. The majority of the impurity is carbonate，such as dolomite，calcite，etc.，and silica，which is less than 2%. In order to obtain high grade concentrate from this high MgO ore，a very strong and selective carbonate collector is required.In beneficiation plant，sulfuric acid was used as pH modifier and phosphate depressant was used. The process flowsheet involves one rougher and one scavenger as shown in Fig. 5. The plant flotation results with three different feeds are summarized in Tab. 5.As shown in Tab. 5，CF-813 is a very strong carbonate collector with good selectivity. A concentrate product with less than 1% MgO and over 33% P2O5 can be obtained after one rougher and one scavenger flotation at relatively low consumption of CF-813 collector. The final P2O5 recovery can be achieved between 88.49% and 93.92%.4 Double Reverse Flotation4.1 Double reverse flotation for phosphate ore from Middle EastThe flotation feed was prepared in the size range of -212 μm+38 μm. The chemical analysis of the feed sample is given in Tab. 6. It can be seen from the feed analysis that the feed contains low MgO，Al2O3，Fe2O3，while the majority of the impurities is carbonate，particularly calcite.The feed was first conditioned with anionic collector CCS-502A at acidic pH 5.0-5.5 using H3PO4 as depressant and pH modifier. The conditioned slurry was subjected to the first reverse flotation to reject carbonate as waste from the float. The sink was conditioned with cationic collector CustAmine? 1208 (CA-1208) at pH between 6.5 and 7 by using soda ash as pH modifier. The simplified flowsheet is shown in Fig. 6 with the flotation results in Tab. 7.It can be seen that a phosphate concentrate with 33.0% P2O5 can be obtained at 85.4% recovery from the feed of 20.2% P2O5，by applying double reverse flotation process. The silica flotation stage can be eliminated if a concentrate product with insol. content of 7%-8% can be accepted.4.2 Double reverse flotation for phosphate ores from North AfricaThere are two feed samples，CI and CIII，with the analysis shown in Tab. 8. The feed samples contain a considerably elevated amount of fine particles with the particle size below 150 μm. The impurity minerals include both carbonate and silica，and the majority of carbonate mineral is dolomite. Both dolomite and silica must be removed to achieve an acceptable phosphate concentrate.The simplified flotation flowsheet for this feed is illustrated in Fig. 7. The feed was conditioned with depressant CP550 and collector CustoFloat714(CF-714) at pH 5.3 for carbonate flotation. The rougher carbonate tail was refloated at pH 5.3. Two underflows of carbonate flotation were combined and sized at 25 μm. The plus 25 μm fraction was conditioned with an amine collector (CA-2060A) for silica flotation，while the minus 25 μm fine fraction was combined with the underflow of silica flotation as a composite concentrate. The flotation results of two samples were summarized in Tab. 9.As can be seen from Table 9，the final product grade of 30.1% P2O5 and 83.8% recovery can be obtained for sample CI and a composite phosphate concentrate with 29.0% P2O5 was achieved at 82.8% recovery from sample CIII.5 “Crago” Double Float Process in eastern USA“Crago” double float process is commonly practiced in Eastern US phosphate industry. The sized feed，such as -600 μm+105 μm，is conditioned at about 70% or higher solids with fatty acid/fuel oil at pH > 9 using pH modifier，such as soda ash or ArrMaz Custo pH product line. The phosphate is floated to produce a rougher concentrate and a sand tailing. Usually rougher concentrate can’t be directly used as a product for downstream process，because a significant amount of fine sand is also floated with phosphate in this step. Therefore，the rougher concentrate will proceed through dewatering，acid-scrubbing and washing to remove reagents from phosphate surfaces，which is known as “deoiling”. The deoiled rougher concentrate is subjected to amine flotation at neutral pH to remove silica as waste. The following is a typical example in which CustoFloat? 167(CF-167)，a fatty acid collector，was used for rougher phosphate flotation，and CustAmine 1260(CA-1260)，a cationic collector for silica flotation. The simplified flowsheet，conditions and flotation results for a typical phosphate feed are shown in Fig. 8. It can be observed that a phosphate concentrate containing over 31.95% P2O5 can be achieved at 88.79% recovery from a low grade feed of 3.74% P2O5.6 ConclusionsArrMaz has made significant efforts in developing flotation reagents for processing phosphate ores worldwide. A variety of anionic and cationic collectors have been developed and successfully applied for various flotation processes，such as direct flotation of phosphate，reverse flotation of silica，reverse flotation of carbonates，double reverse flotation of carbonates and silica，etc. The marketable phosphate concentrate product can be achieved from those phosphate ores through flotation processes with ArrMaz CustoFloat and CustAmine? collectors.References：