Method for comprehensive recovery of rare earth, iron and dolomite from dolomite

Abstract

The application discloses a method for comprehensively recovering rare earth, iron and dolomite from dolomite, and comprises a process of "weak magnetic separation of iron-flotation desulfurization-magnetic separation and flotation combined separation of rare earth from desulfurization tailings-flotation of dolomite from rare earth tailings". The method can obtain high-grade rare earth concentrate, iron concentrate and dolomite concentrate, realizes comprehensive utilization of dolomite type rare earth ore, and has good social and economic values.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mineral processing engineering, and in particular to a method for comprehensively recovering rare earth, iron and dolomite from dolomite. BACKGROUND

[0002] Rare earth is known as "industrial vitamin", because it has excellent photoelectric and electromagnetic physical properties, and can form new materials with different properties and various types with other materials. Its most remarkable function is to greatly improve the quality and performance of other products. China is rich in rare earth resources, with a reserve of about 55 million tons, accounting for 42% of the world's total reserves. The reserves of Baiyunebo mine account for more than 83% of the total reserves of rare earth in China, ranking first in the world, and it is the main production base of light rare earth in China. The rare earth minerals in Baiyunebo are mainly present in dolomite, and are associated with iron, niobium and other valuable metals. Therefore, improving the comprehensive utilization level of mixed rare earth ore can play a positive role in realizing the comprehensive utilization of valuable minerals present in dolomite.

[0003] Because rare earth minerals are closely associated with iron minerals, dolomite and other gangue minerals, and have similar physical and chemical properties, the separation is much more difficult than the separation of single bastnaesite at home and abroad. At present, the method of "magnetic separation-warm flotation" is mainly used to recover rare earth and iron minerals from dolomite type mixed rare earth ore, but the energy consumption is large and the recovery rate of rare earth is low. A large amount of rare earth resources are lost, and it is also difficult to form qualified dolomite products, which fails to achieve the purpose of comprehensive utilization of dolomite type rare earth ore.

[0004] In view of the problems existing in the comprehensive utilization of rare earth, iron and dolomite in dolomite type rare earth ore, how to efficiently separate and recover valuable minerals in dolomite type rare earth ore under the premise of "practicing ecological civilization and accelerating the green development of mining industry" is the field that should be focused on by present mineral processing workers. SUMMARY

[0005] The purpose of the present application is to provide a method for comprehensively recovering rare earth, iron and dolomite from dolomite, which efficiently separates and recovers rare earth, iron and dolomite, the three valuable minerals in dolomite type rare earth ore, realizes the comprehensive utilization of this type of mineral resources, and uses normal temperature flotation method, which greatly reduces the energy consumption generated in the process of mineral processing, and is more conducive to the development of green mining.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0007] The present application provides a method for comprehensively recovering rare earth, iron and dolomite from dolomite, which comprises the following steps:

[0008] (1) Desliming: dolomite type rare earth ore is ground and slurried, and is classified into sand and overflow by a hydrocyclone, the sand is used as weak magnetic separation feed, and the overflow is combined with tailings;

[0009] (2) Weak magnetic separation of iron: the sand in step (1) is subjected to weak magnetic roughing to obtain iron rough concentrate and iron tailings, the iron rough concentrate is subjected to secondary grinding, and then subjected to weak magnetic cleaning to obtain final iron concentrate;

[0010] (3) Desulfurization flotation: the iron tailings in step (2) are thickened and slurried, 150-200 g / t collector, 10-20 g / t frother are sequentially added to the slurry for once roughing, 100-150 g / t collector, 10-20 g / t frother are added for once scavenging, to obtain sulfur rough concentrate, sulfur scavenging concentrate and desulfurization tailings, and the sulfur rough concentrate and the sulfur scavenging concentrate are combined into total tailings;

[0011] (4) Rare earth rough scavenging: 2500-3500 g / t depressant, 500-1000 g / t activator, 1500-2500 g / t collector, 20-40 g / t frother are added to the desulfurization tailings in step (2) for once roughing to obtain rare earth rough concentrate and rare earth rough scavenging tailings, 500-1000 g / t collector, 20-40 g / t frother are added to the rare earth rough scavenging tailings for scavenging I, the scavenging I concentrate is returned to the rare earth rough scavenging process to form a closed circuit; 200-600 g / t collector, 10-30 g / t frother are added to the scavenging I tailings for scavenging II, the scavenging II concentrate is returned to the scavenging I to form a closed circuit; 200-400 g / t collector is added to the scavenging II tailings for scavenging III, the scavenging III concentrate is returned to the scavenging II to form a closed circuit, and the scavenging III tailings are obtained at the same time;

[0012] (5) Rare earth cleaning and fine scavenging: 100-300 g / t depressant, 300-500 g / t collector are added to the rare earth rough concentrate for rare earth cleaning I, the cleaning I concentrate is subjected to once blank cleaning II, the cleaning II tailings are returned to the cleaning I to form a closed circuit; the cleaning II concentrate is subjected to once blank cleaning III, the cleaning III tailings are returned to the cleaning II to form a closed circuit; the cleaning III concentrate is subjected to once strong magnetic roughing, the strong magnetic roughing concentrate is subjected to once strong magnetic cleaning to obtain final rare earth concentrate and rare earth sub-concentrate 1; the strong magnetic roughing tailings are subjected to once strong magnetic scavenging to obtain strong magnetic sub-concentrate 2, and the strong magnetic scavenging tailings are combined into total tailings; 100-300 g / t depressant, 100-400 g / t collector, 20-40 g / t frother are added to the cleaning I tailings for fine scavenging I, 100-300 g / t collector is added to the fine scavenging I tailings for fine scavenging II, and 50-200 g / t collector is added to the fine scavenging II tailings for fine scavenging III to obtain fine scavenging III tailings combined into total tailings; the fine scavenging I, II and III concentrates are combined and returned to the cleaning I to form a closed circuit;

[0013] (6) dolomite flotation: adding 800-1500 g / t depressant, 200-400 g / t collector to the tailings of step (3) for dolomite roughing, adding 100-300 g / t collector to the tailings of dolomite roughing for dolomite scavenging, the obtained scavenging concentrate returns to the dolomite roughing to form a closed loop, and the tailings of scavenging is the final tailings; adding 200-400 g / t depressant, 50-200 g / t collector to the dolomite roughing concentrate for dolomite cleaning, the obtained cleaning tailings returns to the dolomite roughing to form a closed loop, and the cleaning concentrate is the final dolomite concentrate product.

[0014] Further, the dolomite type rare earth ore is a co-associated ore with REO grade of 2%-8%, Fe grade of 15%-25%, CaO grade of 15%-20% and MgO grade of 10%-15%.

[0015] Further, the grinding fineness of step (1) is 80%-90% of -74 μm.

[0016] Further, the magnetic field strength of step (2) is 0.15 T-0.25 T for weak magnetic roughing, 0.10 T-0.2 T for weak magnetic cleaning, and the grinding fineness of the iron rough concentrate is 85%-95% of -74 μm.

[0017] Further, the pulp concentration after step (3) is 40%-50%, the roughing and scavenging collectors are one or more of ethyl xanthate, butyl xanthate and pentyl xanthate, and the frother is pine oil.

[0018] Further, the depressant in steps (4) and (5) is water glass with a modulus of 2.5-3.0, the activator is sodium fluosilicate, the collector is one or more of benzohydroxamic acid, salicylhydroxamic acid and 1-hydroxy-2-naphthohydroxamic acid, and the frother is sec-octyl alcohol.

[0019] Further, the magnetic field strength of step (5) is 1.3-1.8 T for strong magnetic roughing, 1.3-1.8 T for strong magnetic scavenging, and 1.0-1.5 T for strong magnetic cleaning.

[0020] Further, the dolomite flotation depressant in step (6) is water glass with a modulus of 2.5-3.0, and the collector is a mixture of oxidized paraffin soap and sodium oleate with a mass ratio of 1:2.

[0021] Compared with the prior art, the present application has the beneficial technical effects:

[0022] 1. The "weak magnetic separation of iron - flotation desulfurization - desulfurization tailings magnetic and floatation combined separation of rare earth - rare earth tailings flotation dolomite" process provided by the application can obtain high-grade rare earth concentrate, iron concentrate and dolomite concentrate, realizes comprehensive utilization of dolomite type rare earth ore, and has good social and economic value.

[0023] 2. The application adopts different separation methods and designs reasonable beneficiation process for enrichment and recovery in sections according to different characteristics of each target mineral, greatly improves the separation efficiency, and compared with the conventional "magnetic separation - warming flotation" process in Baiyunebo area, greatly improves the grade and recovery rate of rare earth minerals, and reduces the energy consumption required for production.

[0024] 3. The beneficiation method provided by the application can be divided into three parts according to the order of separation: weak magnetic separation of iron, magnetic and floatation combined separation of rare earth, and dolomite flotation, and the advantages are that each part is relatively independent, the previous stage has less interference on the separation effect of the next stage, is beneficial to accurate control of each index, and is convenient for efficient separation of iron concentrate, rare earth concentrate and dolomite concentrate. BRIEF DESCRIPTION OF DRAWINGS

[0025] The application will be further described below in combination with the description of the accompanying drawings.

[0026] Figure 1 It is a process flow diagram of the application.

[0027] Figure 2 It is a conventional process flow diagram. DETAILED DESCRIPTION

[0028] Example 1: A rare earth ore in Baiyunebo west mine is selected as the raw material in this example, the rare earth REO grade is 3.64%, the Fe grade is 14.58%, the CaO grade is 21.60%, the MgO grade is 14.28%, and the grinding fineness is 90% of -74 μm.

[0029] Comparative Example 1

[0030] The conventional process is used: for dolomite type rare earth ore, generally, the weak magnetic separation is used to recover iron minerals first, the rare earth flotation is carried out after the concentration of the iron tailings, under the conditions that the flotation concentration is 35% and the flotation temperature is 70℃, through a roughing - scavenging - three cleaning process, qualified rare earth concentrate is obtained; and the rare earth tailings are used for dolomite flotation, and through a roughing - scavenging - one cleaning process, dolomite concentrate is obtained.

[0031] After grinding, the raw ore is treated by one rough and one fine weak magnetic separation to obtain iron, with a magnetic field intensity of 0.2T for rough weak magnetic separation and a magnetic field intensity of 0.15T for fine weak magnetic separation. The tailings of weak magnetic separation are concentrated, and then, under the condition of a flotation temperature of 70℃, the rare earth flotation test is carried out by one rough, one scavenging and three fine processes of a laboratory XFD type small flotation machine, with a dosage of 3000g / t of water glass, 1000g / t of sodium fluosilicate, 1500g / t of rare earth collector H 205 , and 40g / t of pine oil for the rough selection; a dosage of 800g / t of collector H 205 , and 20g / t of pine oil for the scavenging selection; a dosage of 300g / t of water glass, and 300g / t of collector H 205 for the first fine selection; a dosage of 150g / t of water glass, and 200g / t of collector H 205 for the second fine selection; and the third fine selection is blank.

[0032] The tailings of rare earth flotation are treated by one rough, one scavenging and one fine process to carry out dolomite flotation test, with a dosage of 1000g / t of water glass, and 200g / t of sodium oleate for the rough selection; a dosage of 150g / t of sodium oleate for the scavenging selection; and a dosage of 300g / t of water glass, and 100g / t of sodium oleate for the fine selection.

[0033] Example 1

[0034] By adopting the technology, the dolomite type rare earth ore is ground and slurried, and then classified by a hydrocyclone to obtain sand and overflow; the sand is subjected to weak magnetic separation to obtain iron concentrate and iron tailings; the iron tailings are concentrated and slurried, and then subjected to flotation desulfurization; the desulfurization tailings are subjected to rare earth flotation pre-concentration to obtain rare earth rough concentrate and rare earth flotation tailings; the rare earth rough concentrate is subjected to strong magnetic separation to obtain strong magnetic concentrate as the final rare earth concentrate; and the rare earth flotation tailings are subjected to dolomite flotation to obtain the final dolomite concentrate.

[0035] After the raw material is ground and slurried, the weak magnetic separator is used to carry out iron selection by adopting a process of “weak magnetic rough selection-rough concentrate regrinding-weak magnetic fine selection”, with a magnetic field intensity of 0.2T for weak magnetic rough selection, regrinding of the rough concentrate to 95% of-74μm, and a magnetic field intensity of 0.15T for weak magnetic fine selection; the weak magnetic selection concentrate is the final iron concentrate. The weak magnetic tailings are concentrated, and then, under the condition of a flotation concentration of 50% and normal temperature, the desulfurization treatment is carried out by one rough and one scavenging process of a laboratory XFD type small flotation machine, with a dosage of 150g / t of a desulfurization collector prepared by mixing ethyl sodium xanthate, butyl sodium xanthate and amyl sodium xanthate at a mass ratio of 2:6:2, and a dosage of 20g / t of pine oil as a foaming agent; a dosage of 100g / t of desulfurization collector and a dosage of 20g / t of pine oil as a foaming agent for the scavenging selection.

[0036] The desulfurization tailings are subjected to rare earth flotation test under normal temperature conditions by a "one roughing, three scavenging and three cleaning and three cleaning scavenging" process, and the rare earth collecting agent is prepared by mixing salicylhydroxamic acid and 1-hydroxy-2-naphthyl hydroxamic acid at a mass ratio of 4:1. The specific reagent system is as follows: the dosage of water glass in roughing is 2500 g / t, the dosage of sodium fluosilicate is 500 g / t, the dosage of rare earth collecting agent is 1500 g / t, and the dosage of sec-octyl alcohol is 20 g / t; the dosage of rare earth collecting agent in scavenging I is 500 g / t, the dosage of sec-octyl alcohol is 40 g / t; the dosage of rare earth collecting agent in scavenging II is 200 g / t, the dosage of sec-octyl alcohol is 20 g / t, and the dosage of rare earth collecting agent in scavenging III is 200 g / t; the dosage of water glass in cleaning I is 100 g / t, and the dosage of rare earth collecting agent is 300 g / t; the cleaning II and cleaning III are blank cleaning; the dosage of water glass in cleaning scavenging I is 100 g / t, the dosage of rare earth collecting agent is 100 g / t, and the dosage of sec-octyl alcohol is 40 g / t; the dosage of rare earth collecting agent in cleaning scavenging II is 100 g / t; and the dosage of collecting agent in cleaning scavenging III is 100 g / t.

[0037] The rare earth flotation concentrate is subjected to high-intensity magnetic separation process by a "one roughing, one scavenging and one cleaning" process, the magnetic field intensity in roughing is 1.6 T, the magnetic field intensity in scavenging is 1.6 T, and the magnetic field intensity in cleaning is 1.2 T, and the obtained high-intensity magnetic separation concentrate is the final rare earth concentrate.

[0038] The rare earth flotation tailings are subjected to dolomite flotation test by a "one roughing, one scavenging and one cleaning" process, and the dolomite collecting agent is prepared by mixing oxidized paraffin soap and sodium oleate at a mass ratio of 1:2. The specific reagent system is as follows: the dosage of water glass in roughing is 900 g / t, and the dosage of dolomite collecting agent is 160 g / t; the dosage of dolomite collecting agent in scavenging is 100 g / t; the dosage of water glass in cleaning is 300 g / t, and the dosage of dolomite collecting agent is 100 g / t; and the obtained concentrate is the final dolomite concentrate. The test data are shown in Table 1.

[0039] Example 2: In this example, a certain rare earth ore in the main east mining area of Baiyunebo is selected as raw material, the rare earth REO grade is 6.26%, the Fe grade is 20.32%, the CaO grade is 20.24%, the MgO grade is 13.56%, and the grinding fineness is 85% of -74 μm.

[0040] Comparative Example 2

[0041] By using the conventional process: for the dolomite type rare earth ore, generally, the weak magnetic separation is first used to recover the iron minerals, the tailings after iron recovery are concentrated, and then the rare earth flotation is carried out, under the conditions of a flotation concentration of 35% and a flotation temperature of 70℃, a qualified rare earth concentrate is obtained by a "one roughing, one scavenging and three cleaning" process; and then the rare earth tailings are used for dolomite flotation, and a dolomite concentrate is obtained by a "one roughing, one scavenging and one cleaning" process.

[0042] After grinding, the raw ore is treated by one rough and one fine weak magnetic separation to obtain iron, with a magnetic field intensity of 0.2T for rough weak magnetic separation and a magnetic field intensity of 0.15T for fine weak magnetic separation. The tailings of weak magnetic separation are concentrated, and then, under the condition of a flotation temperature of 70℃, the rare earth flotation test is carried out by one rough, one scavenging and three fine processes of a laboratory XFD type small flotation machine, with a dosage of 3000g / t of water glass, 1000g / t of sodium fluosilicate, 1500g / t of rare earth collector H 205 , and 40g / t of pine oil for the rough selection; a dosage of 800g / t of collector H 205 , and 20g / t of pine oil for the scavenging selection; a dosage of 300g / t of water glass and 300g / t of collector H 205 for the first fine selection; a dosage of 150g / t of water glass and 200g / t of collector H 205 for the second fine selection; and the third fine selection is blank.

[0043] The tailings of rare earth flotation are treated by one rough, one scavenging and one fine process to carry out dolomite flotation test, with a dosage of 1000g / t of water glass and 200g / t of collector oleic acid for the rough selection; a dosage of 150g / t of collector oleic acid for the scavenging selection; and a dosage of 300g / t of water glass and 100g / t of collector oleic acid for the fine selection.

[0044] Example 2

[0045] By adopting the technology, the dolomite type rare earth ore is ground and slurried, and then classified by a hydrocyclone to obtain sand and overflow; the sand is subjected to weak magnetic separation to obtain iron concentrate and iron tailings; the iron tailings are concentrated and slurried, and then subjected to flotation desulfurization to obtain sulfur rough concentrate and desulfurization tailings; the desulfurization tailings are subjected to rare earth flotation pre-concentration to obtain rare earth rough concentrate and rare earth flotation tailings; the rare earth rough concentrate is subjected to strong magnetic separation to obtain strong magnetic concentrate as the final rare earth concentrate; and the rare earth flotation tailings are subjected to dolomite flotation to obtain the final dolomite concentrate.

[0046] After the raw material is ground and slurried, the weak magnetic separator is used to carry out iron separation by adopting a process of “weak magnetic rough selection-rough concentrate regrinding-weak magnetic fine selection”, with a magnetic field intensity of 0.2T for weak magnetic rough selection, the rough concentrate being regrinded to 95% of-74μm, and a magnetic field intensity of 0.15T for weak magnetic fine selection; the weak magnetic selected concentrate is the final iron concentrate. The weak magnetic tailings are concentrated, and then, under the condition of a flotation concentration of 50% and normal temperature, the desulfurization treatment is carried out by one rough and one scavenging process of a laboratory XFD type small flotation machine, with a dosage of 150g / t of desulfurization collector prepared by mixing sodium ethyl xanthate, sodium butyl xanthate and sodium pentyl xanthate at a mass ratio of 2:6:2, and a dosage of 20g / t of foaming agent pine oil; a dosage of 100g / t of desulfurization collector and a dosage of 20g / t of pine oil for the scavenging selection.

[0047] The desulfurization tailings are subjected to rare earth flotation test under normal temperature conditions through a "one roughing, three scavenging and three cleaning" process, and the rare earth collecting agent is prepared by mixing salicylhydroxamic acid and 1-hydroxy-2-naphthoic hydroxamic acid at a mass ratio of 4:1. The specific reagent system is as follows: the dosage of water glass in roughing is 2500 g / t, the dosage of sodium fluosilicate is 500 g / t, the dosage of rare earth collecting agent is 1500 g / t, and the dosage of sec-octyl alcohol is 20 g / t; the dosage of rare earth collecting agent in scavenging I is 500 g / t, the dosage of sec-octyl alcohol is 40 g / t; the dosage of rare earth collecting agent in scavenging II is 200 g / t, the dosage of sec-octyl alcohol is 20 g / t, and the dosage of rare earth collecting agent in scavenging III is 200 g / t; the dosage of water glass in cleaning I is 100 g / t, and the dosage of rare earth collecting agent is 300 g / t; the cleaning II and cleaning III are blank cleaning; the dosage of water glass in scavenging I is 100 g / t, the dosage of rare earth collecting agent is 100 g / t, the dosage of sec-octyl alcohol is 40 g / t; the dosage of rare earth collecting agent in scavenging II is 100 g / t; and the dosage of collecting agent in scavenging III is 100 g / t.

[0048] The rare earth flotation concentrate is subjected to strong magnetic separation process through a "one roughing, one scavenging and one cleaning" process, the magnetic field strength in roughing is 1.6T, the magnetic field strength in scavenging is 1.6T, and the magnetic field strength in cleaning is 1.2T, and the obtained strong magnetic separation concentrate is the final rare earth concentrate.

[0049] The rare earth flotation tailings are subjected to dolomite flotation test through a "one roughing, one scavenging and one cleaning" process, and the dolomite collecting agent is prepared by mixing oxidized paraffin soap and sodium oleate at a mass ratio of 1:2. The specific reagent system is as follows: the dosage of water glass in roughing is 900 g / t, and the dosage of dolomite collecting agent is 160 g / t; the dosage of dolomite collecting agent in scavenging is 100 g / t; the dosage of water glass in cleaning is 300 g / t, and the dosage of dolomite collecting agent is 100 g / t; and the obtained concentrate is the final dolomite concentrate. The test data are shown in Table 1.

[0050] Table 1: Test data of each example and comparative example

[0051]

[0052]

[0053] As can be seen from the test data in the above table, through the mineral processing technology provided by the present application, the white dolomite type rare earth ore is used as the raw ore, different selection methods are adopted for different characteristics of each target mineral to enrich and recover the target mineral in sections, and the separation efficiency is greatly improved. Compared with the conventional "magnetic separation-warm flotation" process in Baiyunebo area at present, the grade and recovery rate of iron, rare earth and dolomite concentrate are greatly improved, the energy consumption required for production is reduced, and the efficient separation and comprehensive utilization of iron, rare earth and dolomite in white dolomite are realized.

[0054] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A method for comprehensive recovery of rare earth, iron and dolomite from dolomite, characterized in that: The method comprises the following steps: (1) desliming: dolomite type rare earth ore is ground and slurried, and is classified into sand and overflow by a hydrocyclone, the sand is used as weak magnetic separation feed, and the overflow is combined with tailings; (2) weak magnetic separation of iron: the sand in step (1) is subjected to weak magnetic rough separation to obtain iron rough concentrate and iron tailings, the iron rough concentrate is subjected to secondary grinding, and then subjected to weak magnetic separation to obtain final iron concentrate; (3) desulfurization flotation: the iron tailings in step (2) are concentrated and slurried, 150-200 g / t collector, 10-20 g / t foaming agent are sequentially added to the slurry to perform once rough separation, 100-150 g / t collector, 10-20 g / t foaming agent are added to perform once scavenging, to obtain sulfur rough concentrate, sulfur scavenging concentrate and desulfurization tailings, and the sulfur rough concentrate and the sulfur scavenging concentrate are combined with the total tailings; (4) rare earth rough scavenging: 2500-3500 g / t depressant, 500-1000 g / t activator, 1500-2500 g / t collector and 20-40 g / t foaming agent are added to the desulfurization tailings in step (3) to perform once rough separation, to obtain rare earth rough concentrate and rare earth rough scavenging tailings, 500-1000 g / t collector and 20-40 g / t foaming agent are added to the rare earth rough scavenging tailings to perform scavenging I, and the scavenging I concentrate is returned to the rare earth rough scavenging process to form a closed loop; 200-600 g / t collector and 10-30 g / t foaming agent are added to the scavenging I tailings to perform scavenging II, the scavenging II concentrate is returned to the scavenging I to form a closed loop; 200-400 g / t collector is added to the scavenging II tailings to perform scavenging III, the scavenging III concentrate is returned to the scavenging II to form a closed loop, and the scavenging III tailings are obtained at the same time; (5) rare earth separation and fine scavenging: 100-300 g / t depressant and 300-500 g / t collector are added to the rare earth rough concentrate to perform rare earth separation I, the separation I concentrate is subjected to once blank separation II, the separation II tailings are returned to the separation I to form a closed loop; the separation II concentrate is subjected to once blank separation III, the separation III tailings are returned to the separation II to form a closed loop; the separation III concentrate is subjected to once strong magnetic rough separation, the strong magnetic rough separation concentrate is subjected to once strong magnetic separation, to obtain final rare earth concentrate and rare earth sub-concentrate one; the strong magnetic rough separation tailings are subjected to once strong magnetic scavenging, to obtain strong magnetic sub-concentrate two, and the strong magnetic scavenging tailings are combined with the total tailings; 100-300 g / t depressant, 100-400 g / t collector and 20-40 g / t foaming agent are added to the separation I tailings to perform fine scavenging I, 100-300 g / t collector is added to the fine scavenging I tailings to perform fine scavenging II, and 50-200 g / t collector is added to the fine scavenging II tailings to perform fine scavenging III, to obtain fine scavenging III tailings combined with the total tailings; the fine scavenging I, II and III concentrates are combined and returned to the separation I to form a closed loop; (6) dolomite flotation: adding 800~1500g / t depressant and 200~400g / t collector to the tailings of step (4) to conduct dolomite roughing, adding 100~300g / t collector to the tailings of dolomite roughing to conduct dolomite scavenging, returning the scavenging concentrate to the dolomite roughing to form a closed loop, and the tailings of scavenging being the final tailings; adding 200~400g / t depressant and 50~200g / t collector to the dolomite roughing concentrate to conduct dolomite cleaning, returning the cleaning tailings to the dolomite roughing to form a closed loop, and the cleaning concentrate being the final dolomite concentrate product.

2. The method according to claim 1, characterized in that: The dolomite type rare earth ore is a co-associated ore with REO grade of 2%~8%, Fe grade of 15%~25%, CaO grade of 15%~20% and MgO grade of 10%~15%.

3. The method for comprehensive recovery of rare earth, iron and dolomite from dolomite according to claim 1, characterized in that: The grinding fineness of step (1) is 80%~90% of -74μm.

4. The method for comprehensive recovery of rare earth, iron and dolomite from dolomite according to claim 1, characterized in that: The magnetic field strength of step (2) is 0.15T~0.25T for the roughing, 0.10T~0.2T for the cleaning, and the grinding fineness of the iron roughing concentrate is 85%~95% of -74μm.

5. The method for comprehensive recovery of rare earth, iron and dolomite from dolomite according to claim 1, characterized in that: The pulp concentration after step (3) is 40%~50%, the roughing and scavenging collectors are one or more of ethyl xanthate, butyl xanthate and amyl xanthate, and the frother is pine oil.

6. The method for comprehensive recovery of rare earth, iron and dolomite from dolomite according to claim 1, characterized in that: The depressant in steps (4) and (5) is water glass with modulus of 2.5~3.0, the activator is sodium fluorosilicate, the collector is one or more of benzohydroxamic acid, salicylhydroxamic acid and 1-hydroxy-2-naphthohydroxamic acid, and the frother is sec-octyl alcohol.

7. The method according to claim 1, characterized in that: The magnetic field strength of step (5) is 1.3~1.8T for the roughing, 1.3~1.8T for the scavenging, and 1.0~1.5T for the cleaning.

8. The method for comprehensive recovery of rare earth, iron and dolomite from dolomite according to claim 1, characterized in that: The dolomite flotation depressant in step (6) is water glass with modulus of 2.5~3.0, and the collector is a mixture of oxidized paraffin soap and sodium oleate with mass ratio of 1:2.

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