Method for preparing pellets from composite ground phosphate rock

Abstract

The invention relates to a method for preparing pellets from composite ground phosphate rock. The method comprises the following steps: 1) classifying the ground phosphate rock according to different balling moisture contents and different silicon-calcium contents in the ground phosphate rock; 2) according to a set mixing balling index and a set mixing balling acidity index, performing batching treatment on the various types of fine ground phosphate rock powder obtained in the step 1) to obtain a mixture; and 3) carrying out fine grinding treatment on the mixture obtained in the step 2) to obtain composite fine ground phosphate rock powder, and sequentially pelletizing, roasting, cooling and screening the composite fine ground phosphate rock powder to obtain the phosphate rock powder pellets. By detecting the balling moisture and pH value indexes of the ground phosphate rock and combining the mixture balling index and the mixture acidity of the composite ground phosphate rock, the optimal proportion range of various ground phosphate rock is calculated, and the ore blending proportions of different ground phosphate rock are regulated and controlled. The drop strength, compressive strength and other properties of green pellets can meet the production requirements without using a binder, the acidity value of the pellets is close to the smelting requirement of a yellow phosphorus electric furnace, and the direct addition amount of a fluxing agent is reduced.

Description

Technical Field

[0001] The invention relates to a method for preparing pellets from phosphate rock powder, in particular to a method for preparing pellets from composite phosphate rock powder, and belongs to the field of yellow phosphorus production. Background Art

[0002] Phosphate ore is the main raw material for electric furnace smelting of yellow phosphorus. In production, the electric furnace is required to be phosphate ore lump, that is, the particle size of phosphate ore is above 5mm. In recent years, the resources of high-quality phosphate ore lump have become less and less, and the price has continued to run at a high level. Yellow phosphorus production faces high raw material cost pressure. On the other hand, 30%-50% of phosphate ore powder with a particle size of less than 5mm will be produced during the pretreatment process of phosphate ore mining, transportation and smelter crushing, drying, screening, etc. This part of phosphate ore powder cannot be directly put into the furnace for yellow phosphorus smelting and can only be stored or sold at a low price, resulting in a great waste of phosphate ore resources. With the rapid development of my country's phosphorus chemical industry, high-quality phosphate ore lump resources have been unable to meet the needs of yellow phosphorus production. Pre-treating phosphate ore powder into artificial "phosphate ore lump" with a particle size that meets the requirements of yellow phosphorus electric furnace has become an important way for phosphorus chemical companies to improve the utilization efficiency of phosphate ore resources and reduce the cost of raw materials for yellow phosphorus production.

[0003] At present, there are many methods for preparing pellets using phosphate rock powder. For example, patent CN104261363B discloses a method for granulating, molding and roasting phosphate rock powder, which requires that the phosphate rock powder that has been pre-treated by crushing, screening, drying and homogenization be sent to a ball mill for grinding, then enter a disc granulator, and add a binder made of acid slag, an intermediate product of dihydrate wet phosphoric acid production, so that the phosphate rock powders are bonded to each other to form phosphate rock pellets with a particle size of 20 to 30 mm, and the tail gas of the phosphorus furnace is passed into a chain grate roaster, roasted at a temperature of 850 to 950°C, and cooled by air to form phosphate rock pellets for yellow phosphorus production. Patent CN105603179A discloses a phosphate rock powder granulation, molding and sintering process, which comprises the following steps: pre-treating the phosphate rock by crushing, screening, drying and homogenizing, and then feeding the phosphate rock powder into a ball mill to grind the phosphate rock powder to a particle size of ≤1mm, and then bonding the phosphate rock powders to each other through adhesives and additives such as water-based polymers, gallic acid, and fly ash, and then coating the surface of the obtained phosphate rock powder with a layer of fuel, loading the phosphate rock powder into a chain roasting machine for roasting, and then feeding the chain cooler for cooling, crushing and screening to form phosphate rock pellets with a particle size of 10-20mm. Patent CN 102701164 B discloses a method for processing phosphate rock powder into pelletized yellow phosphorus furnace charge, wherein phosphate rock powder (100 mesh) is added with a binder made of humic acid and sodium hydroxide and stirred evenly, pressed into pellets by a pelletizing machine, rolled on a pelletizing plate, initially dried in a hot air furnace and further dried thoroughly in a vertical kiln, and then calcined in a rotary kiln at a high temperature of 1100°C to 1200°C to obtain the finished yellow phosphorus furnace charge.

[0004] In the prior art, when phosphate rock powder is prepared into artificial agglomerates, in order to improve the drop strength, compressive strength and other properties of the raw agglomerates or finished agglomerates to meet the production and transportation requirements, it is often necessary to add various binders and additives. On the one hand, this increases the processing cost, and on the other hand, various binders are specific and have poor market liquidity, which increases the difficulty of technology promotion due to differences in resource conditions among factories. Summary of the invention

[0005] In view of the problems in the prior art that binders and additives need to be added when preparing artificial agglomerates from phosphate rock powder, which leads to high difficulty in technology promotion and high processing costs, the present invention proposes a method for preparing pellets from composite phosphate rock powder. Without using binders or additives, phosphate rock powder is used as raw material to produce phosphate pellets that meet the requirements of electric furnace production process. At the same time, this method is non-specific and easy to promote.

[0006] According to an embodiment of the present invention, a method for preparing pellets from composite phosphate rock powder is provided.

[0007] A method for preparing pellets from composite phosphate rock powder, the method comprising the following steps:

[0008] 1) Detect the ball-forming moisture content and silicon-calcium content in several types of phosphate rock powders, and classify the phosphate rock powders according to the different ball-forming moisture content and silicon-calcium content in the phosphate rock powders;

[0009] 2) batching the various phosphate rock powders obtained in step 1) according to a set mixture balling index and a set mixture balling acidity index to obtain a mixture;

[0010] 3) The mixed material obtained in step 2) is finely ground to obtain composite finely ground phosphate rock powder, and the composite finely ground phosphate rock powder is successively subjected to balling, roasting, cooling, and screening to obtain phosphate rock powder pellets.

[0011] Preferably, the detection in step 1) is as follows: sampling each type of phosphate rock powder separately, grinding and detecting the spherical moisture content and silicon-calcium content therein.

[0012] Preferably, the spherical moisture content in step 1) refers to the maximum capillary water content W of the phosphate rock powder. 毛 , wt% and the maximum molecular water content of phosphate rock powder W 分 , wt%; the silicon-calcium content refers to the SiO 2 Content W sd , wt% and CaO content of phosphate rock powder W co , wt%.

[0013] Preferably, the mixing ball index K in step 2) is 混 The calculation method is as follows:

[0014]

[0015] Substitute the phosphate rock powder ball index obtained in step 1) into the test to obtain:

[0016]

[0017] In the formula, K 混 W is the balling index of the mixture; 分n is the largest molecular water of the nth type of phosphate rock powder, %; W 毛n is the maximum capillary water content of the nth type of phosphate rock powder, %; X n is the ratio of the nth type of phosphate rock powder, %; and / or

[0018] Step 2) The mixed ball acidity index Ac 混 The calculation method is as follows:

[0019]

[0020] Bring in the phosphate rock powder balling index obtained in step 1):

[0021]

[0022] In the formula, Ac 混 W is the balling acidity index of the mixture; sdn is the SiO of the nth phosphate rock powder 2 Content, %; W con is the CaO content of the nth type of phosphate rock powder, %; X n is the ratio of the nth type of phosphate rock powder, %;

[0023] In formula (2) and formula (4),

[0024] X 1 +X 2 +…+X n =100%……(Formula 5).

[0025] Preferably, the mixing ball index K 混 The limited range is K 混 ≥0.35, preferably K 混 ≥0.40.

[0026] Preferably, the mixed ball acidity index Ac 混 The limited range is 0.70≤Ac 混 ≤0.85, preferably 0.75≤Ac 混 ≤0.80.

[0027] Preferably, the ingredients described in step 2) are prepared by blending the ore according to the optimal phosphate rock powder ratio calculated in step 2).

[0028] Preferably, the fine grinding in step 3) is: fine grinding the composite phosphate rock powder to 0.15 mm with a passing rate of 80% to 95%, preferably 85% to 90%.

[0029] Preferably, the pelletizing in step 3) is to form the composite phosphate rock powder into pellets of 12 to 30 mm, preferably 15 to 25 mm.

[0030] Preferably, the calcination temperature in step 3) is 950-1050° C., preferably 970-1030° C.; the calcination time is 6-15 min, preferably 7-13 min.

[0031] Preferably, the screening in step 3) is as follows: using a vibrating screen with an aperture of 20-30 mm and 12-20 mm to screen the cooled pellets, wherein the pellets on the 20-30 mm aperture screen are finished phosphate ore pellets, and the pellets on the 12-20 mm aperture screen are used as finished phosphate ore pellets (and / or) roasting base materials.

[0032] Preferably, the step 1) specifically comprises: sampling several kinds of phosphate rock powder, grinding the samples to 0.15 mm with a passing rate of 80% to 95% (preferably 85% to 90%), obtaining finely ground phosphate rock powder, and detecting the maximum capillary water content W of each finely ground phosphate rock powder. 毛 ,%、Maximum molecular water W 分 ,%、SiO 2 Content W sd ,%CaO content W co , %, and classify them.

[0033] Preferably, the step 2) is specifically as follows: the maximum capillary water content W of each finely ground phosphate rock powder detected in step 1) is 毛 ,%、Maximum molecular water W 分 ,%、SiO 2 Content W sd ,%CaO content W co , %, as well as the calculation method and limited range of the mixing ball index K and the mixing ball acidity index Ac, to obtain the optimal phosphate rock powder ratio, and mix the ingredients according to the optimal phosphate rock powder ratio to obtain a mixture.

[0034] Preferably, the step 3) is specifically as follows: the mixed material obtained in step 2) is fed into a fine grinding device, finely ground to 0.15 mm with a pass rate of 80% to 95% (preferably 85% to 90%) to obtain composite finely ground phosphate rock powder, the composite finely ground phosphate rock powder is formed into pellets of 12 to 30 mm (preferably 15 to 25 mm) using a disc pelletizer or a cylinder pelletizer, and then fed into a roasting device, and after a drying stage, roasted at 950 to 1050° C. (preferably 970 to 1030° C.) for 6 to 15 min (preferably 7 to 13 min), and after cooling and screening, phosphate rock powder pellets are obtained.

[0035] In the present invention, based on a large number of experiments, it is known that due to the different varieties of various phosphate rock powders, their balling index and silicon-rich / calcium-rich characteristics will be different, and the balling index and silicon-rich / calcium-rich characteristics are key parameters in the phosphate rock powder pelletizing process, which can affect the drop strength, compressive strength, and consolidation speed of the phosphate rock powder pellets during high-temperature roasting. The present invention first detects the balling indexes of each phosphate rock powder, including the maximum capillary water W 毛 、The largest molecular water W 分 、SiO 2 Content W sd And CaO content W co . According to the ball-forming index and proportion of each phosphate rock powder, the mixed ball-forming index and the mixed ball-forming acidity index of the composite phosphate rock powder can be obtained. At the same time, the experimental data show that there is an optimal range for the mixed ball-forming index and the mixed ball-forming acidity index of the mixture. Therefore, according to the optimal range of the mixed ball-forming index and the mixed ball-forming acidity of the mixture, as well as the ball-forming index of each phosphate rock powder, the optimal proportion range of each phosphate rock powder can be inferred, which can be used as the basis for the ingredients of different types of phosphate rock powder, so as to achieve the purpose of making the drop strength and compressive strength of the phosphate rock powder pellets meet the production requirements without using a binder.

[0036] In the present invention, the mixed ball index and K are parameters that comprehensively reflect the particle size, particle size composition, specific surface area and hydrophilicity of the reaction material. According to the size of the ball index K, the ball properties of the material are divided as follows: K < 0.2, no ball properties; K = 0.2-0.35, weak ball properties; K = 0.35-0.6, medium ball properties; K = 0.6-0.8, good ball properties; K > 0.8, excellent ball properties. Experimental data show that the ball properties of different types of phosphate rock powder after fine grinding vary greatly. The difference in the ball properties K of finely ground phosphate rock powder of different origins, chemical composition types, and geological mineralization characteristics is between 0.05 and 0.6, indicating that the ball properties of different types of phosphate rock powder have significant differences. The scheme adopted by the present invention utilizes the difference in ball-forming properties to set a target for the ball-forming index K of the mixture (≥0.35, preferably ≥0.40), which is used as one of the bases for regulating the proportion of different types of phosphate rock powder and providing a reference for the purchase of phosphate rock by yellow phosphorus production units, so as to achieve the purpose of ensuring that the drop strength and compressive strength of the raw balls meet the production requirements without using a binder.

[0037] In the present invention, the acidity index Ac of the mixed material ball formation refers to the SiO2 content in the phosphate rock powder used in the yellow phosphorus electric furnace production. 2 The ratio of acidity to CaO content, suitable acidity can reduce the use of raw flux in subsequent circuits and reduce energy consumption. The present invention classifies phosphate rock powder by its natural silicon-rich / calcium-rich characteristics, and sets the acidity Ac as an index parameter of the mixture during ore blending, as the second basis for regulating the blending ratio of different types of phosphate rock powder. Since the phosphorus-containing compounds in the phosphate ore will be reduced by C in the coke in the remelting state in the yellow phosphorus electric furnace, in order to reduce the melting point of the phosphate ore and thus reduce the smelting energy consumption, the acidity of the yellow phosphate ore is generally around 0.80-0.85. To achieve this purpose, it is usually necessary to add flux separately to the electric furnace charge. Depending on the origin and geological mineralization characteristics, the SiO2 content of phosphate ore may be higher than that of calcium-rich phosphate ore. 2 The content of SiO is generally 3.1% to 45.7%, and the content of CaO is generally 15.5% to 49.3%. 2 The amount of CaO in the coke ash is divided into silicon-rich type and calcium-rich type. 2 The acidity of the mixture is set to 0.75 ≤ Ac 混 ≤0.80, which is used as the second basis for adjusting the proportion of different types of phosphate rock powder and providing a reference for the purchase of phosphate ore by yellow phosphorus production units. It not only makes the acidity value of phosphate rock pellets closer to the requirements of electric furnace smelting, but also accelerates the consolidation rate of phosphate rock pellets during high-temperature roasting and improves the compressive strength of phosphate rock pellets.

[0038] In the present invention, the optimal ratio range of each phosphate rock powder is calculated according to the optimal range of the mixed ball index and the mixed ball acidity of the mixture, and the ball index of each phosphate rock powder. If there are 2 or 3 types of phosphate rock powder, the accurate ratio range of each phosphate rock powder can be calculated by formula 2, formula 4, and formula 5; if there are 4 or more types of phosphate rock powder, firstly, the phosphate rock powder with the closest ball moisture content and silicon-calcium content is divided into one category (a total of 2 or 3 categories), and then the average ball moisture content and silicon-calcium content of each type of phosphate rock powder are calculated, and finally the optimal ratio is calculated by formula 2, formula 4, and formula 5, and batching is performed; if there are 4 or more types of phosphate rock powder, every 3 types of phosphate rock powder can also be divided into a group (if the last group is less than 3 types, the last 2 types are divided into a group, or every 2 types of the 4 types are divided into 1 group), and the optimal ratio of each group is calculated by formula 2, formula 4, and formula 5, and batching is performed, and after the batching is completed, each group of phosphate rock powder is mixed.

[0039] In the present invention, the classification standard described in step 1) is to classify different types of phosphate rock powders with similar spherical water content and silicon-calcium content into one category. For example, when the maximum molecular water content of different types of phosphate rock powders differs by less than 0.5% and the silicon-calcium ratio differs by less than 0.2, they are classified into one category and treated as one type of phosphate rock powder. The specific values ​​in the classification standard are determined in combination with actual conditions.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention provides a method for preparing pellets from composite phosphate rock powder, which detects the ball-forming moisture content and silicon-calcium content of the phosphate rock powder, and calculates the optimal ratio range of multiple phosphate rock powders in combination with the spherical index of the composite phosphate rock powder mixture and the acidity of the mixture, thereby adjusting the proportion of different types of phosphate rock powders to achieve the purpose of ensuring that the drop strength, compressive strength and other properties of the raw balls meet production requirements without using a binder.

[0042] 2. The present invention provides a method for preparing pellets from composite phosphate rock powder. The acidity value of the prepared phosphate rock powder pellets is close to the requirements of electric furnace smelting. In the subsequent smelting process, the use of electric furnace flux can be reduced, saving the flux and the heat consumed by decomposing the flux.

[0043] 3. The method for preparing pellets with composite phosphate rock powder provided by the present invention has a technical route that is not specific due to differences in resource conditions among production enterprises. Enterprises can purchase different types of phosphate rock powder according to actual needs. The technology is highly practical and easy to promote. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0045] According to an embodiment of the present invention, a method for preparing pellets from composite phosphate rock powder is provided.

[0046] A method for preparing pellets from composite phosphate rock powder, the method comprising the following steps:

[0047] 1) Detect the ball-forming moisture content and silicon-calcium content in several types of phosphate rock powders, and classify the phosphate rock powders according to the different ball-forming moisture content and silicon-calcium content in the phosphate rock powders;

[0048] 2) batching the various phosphate rock powders obtained in step 1) according to a set mixture balling index and a set mixture balling acidity index to obtain a mixture;

[0049] 3) The mixed material obtained in step 2) is finely ground to obtain composite finely ground phosphate rock powder, and the composite finely ground phosphate rock powder is successively subjected to balling, roasting, cooling, and screening to obtain phosphate rock powder pellets.

[0050] Preferably, the detection in step 1) is as follows: sampling each type of phosphate rock powder separately, grinding and detecting the spherical moisture content and silicon-calcium content therein.

[0051] Preferably, the spherical moisture content in step 1) refers to the maximum capillary water content W of the phosphate rock powder. 毛 , wt% and the maximum molecular water content of phosphate rock powder W 分 , wt%; the silicon-calcium content refers to the SiO 2 Content W sd , wt% and CaO content of phosphate rock powder W co , wt%.

[0052] Preferably, the mixing ball index K in step 2) is 混 The calculation method is as follows:

[0053]

[0054] Substitute the phosphate rock powder ball index obtained in step 1) into the test to obtain:

[0055]

[0056] In the formula, K 混 W is the balling index of the mixture; 分n is the largest molecular water of the nth type of phosphate rock powder, %; W 毛n is the maximum capillary water content of the nth type of phosphate rock powder, %; X n is the ratio of the nth type of phosphate rock powder, %; and / or

[0057] Step 2) The mixed ball acidity index Ac 混 The calculation method is as follows:

[0058]

[0059] Bring in the phosphate rock powder balling index obtained in step 1):

[0060]

[0061] In the formula, Ac 混 W is the balling acidity index of the mixture; sdn is the SiO of the nth phosphate rock powder 2 Content, %; W con is the CaO content of the nth type of phosphate rock powder, %; X n is the ratio of the nth type of phosphate rock powder, %;

[0062] In formula (2) and formula (4),

[0063] X 1 +X 2 +…+X n =100%……(Formula 5).

[0064] Preferably, the mixing ball index K 混 The limited range is K 混 ≥0.35, preferably K 混 ≥0.40.

[0065] Preferably, the mixed ball acidity index Ac 混 The limited range is 0.70≤Ac 混 ≤0.85, preferably 0.75≤Ac 混 ≤0.80.

[0066] Preferably, the ingredients described in step 2) are prepared by blending the ore according to the optimal phosphate rock powder ratio calculated in step 2).

[0067] Preferably, the fine grinding in step 3) is: fine grinding the composite phosphate rock powder to 0.15 mm with a passing rate of 80% to 95%, preferably 85% to 90%.

[0068] Preferably, the pelletizing in step 3) is to form the composite phosphate rock powder into pellets of 12 to 30 mm, preferably 15 to 25 mm.

[0069] Preferably, the calcination temperature in step 3) is 950-1050° C., preferably 970-1030° C.; the calcination time is 6-15 min, preferably 7-13 min.

[0070] Preferably, the screening in step 3) is as follows: using a vibrating screen with an aperture of 20-30 mm and 12-20 mm to screen the cooled pellets, wherein the pellets on the 20-30 mm aperture screen are finished phosphate ore pellets, and the pellets on the 12-20 mm aperture screen are used as finished phosphate ore pellets (and / or) roasting base materials.

[0071] Preferably, the step 1) specifically comprises: sampling several kinds of phosphate rock powder, grinding the samples to 0.15 mm with a passing rate of 80% to 95% (preferably 85% to 90%), obtaining finely ground phosphate rock powder, and detecting the maximum capillary water content W of each finely ground phosphate rock powder. 毛 ,%、Maximum molecular water W 分 ,%、SiO 2 Content W sd ,%CaO content W co , %, and classify them.

[0072] Preferably, the step 2) is specifically as follows: the maximum capillary water content W of each finely ground phosphate rock powder detected in step 1) is 毛 ,%、Maximum molecular water W 分 ,%、SiO 2 Content W sd ,%CaO content W co , %, as well as the calculation method and limited range of the mixing ball index K and the mixing ball acidity index Ac, to obtain the optimal phosphate rock powder ratio, and mix the ingredients according to the optimal phosphate rock powder ratio to obtain a mixture.

[0073] Preferably, the step 3) is specifically as follows: the mixed material obtained in step 2) is fed into a fine grinding device, finely ground to 0.15 mm with a pass rate of 80% to 95% (preferably 85% to 90%) to obtain composite finely ground phosphate rock powder, the composite finely ground phosphate rock powder is formed into pellets of 12 to 30 mm (preferably 15 to 25 mm) using a disc pelletizer or a cylinder pelletizer, and then fed into a roasting device, and after a drying stage, roasted at 950 to 1050° C. (preferably 970 to 1030° C.) for 6 to 15 min (preferably 7 to 13 min), and after cooling and screening, phosphate rock powder pellets are obtained.

[0074] Example 1

[0075] A method for preparing pellets from composite phosphate rock powder, the method comprising the following steps:

[0076] 1) Sampling two kinds of phosphate rock powder, grinding the samples to 0.15 and passing rate 90% respectively, to obtain finely ground phosphate rock powder, and the maximum capillary water and maximum molecular water of the finely ground sample of the first kind of phosphate rock powder are detected, respectively. 毛1 =23.23%, W 分1=7.2%, the maximum capillary water and maximum molecular water of the second phosphate rock powder finely ground sample were detected, respectively. 毛2 =19.67%, W 分2 =3.5%; Detection of SiO2 in the first type of phosphate rock powder finely ground sample 2 and CaO contents are w sd1 =39.43%, w co1 =30.12%, the SiO content of the second phosphate rock powder finely ground sample was detected 2 and CaO contents are w sd2 =12.04%, w co2 =42.98%.

[0077] 2) According to the relationship between the ball-forming index and proportion of phosphate rock powder and the ball-forming index K and acidity Ac, it can be obtained:

[0078]

[0079]

[0080] X 1 +X 2 =100%……(Formula 5)

[0081] Due to K 混 The optimal range is K 混 ≥0.35, Ac 混 The optimal range is 0.75≤Ac 混 ≤0.80, substituting into equation 2, equation 4 and equation 5, we can get:

[0082] Substituting into equation 2 and equation 5, we can get: X 1 ≥0.576; Substituting into equation 4 and equation 5, we get: 0.546≤X 1 ≤0.594;

[0083] That is X 1 =57.6%~59.4%,X 2 =40.6%~42.4%.

[0084] 3) According to the optimal phosphate rock powder ratio obtained in step 2), take X 1 =56%,X 2 =44% for batching, the two phosphate rock powders are mixed evenly and then sent to fine grinding equipment, finely ground to 0.15mm with a passing rate of 90%, to obtain composite finely ground phosphate rock powder.

[0085] 4) The composite finely ground phosphate rock powder obtained in step 3) is formed into pellets of 15 to 25 mm using a disc pelletizer or a cylinder pelletizer, and then sent to a roasting device, roasted at 1000° C. for 10 minutes after a drying stage, and then cooled and sieved to obtain phosphate rock powder pellets.

[0086] Example 2

[0087] A method for preparing pellets from composite phosphate rock powder, the method comprising the following steps:

[0088] 1) Three kinds of phosphate rock powder were sampled and finely ground to 0.15 with a passing rate of 90% to obtain finely ground phosphate rock powder. The maximum capillary water and maximum molecular water of the finely ground sample of the first kind of phosphate rock powder were detected, respectively. 毛1 =22.68%, W 分1 =8.5%, the maximum capillary water and maximum molecular water of the second type of phosphate rock powder finely ground sample were detected, respectively. 毛2 =23.59%, W 分2 =5.2%, the maximum capillary water and maximum molecular water of the third type of phosphate rock powder finely ground sample were detected, respectively. 毛3 =19.32%, W 分3 =4.8%; Detection of SiO2 in the first type of phosphate rock powder finely ground sample 2 and CaO contents are w sd1 =42.36%, w co1 =28.94%, the SiO content of the second phosphate rock powder finely ground sample was detected 2 and CaO contents are w sd2 =15.22%, w co2 =46.85%, testing the SiO 2 and CaO contents are w sd3 =30.66%, w co3 =37.92%.

[0089] 2) According to the relationship between the ball-forming index and proportion of phosphate rock powder and the ball-forming index K and acidity Ac, it can be obtained:

[0090]

[0091]

[0092] X 1 +X 2 +X 3 =100%……(Formula 5)

[0093] Due to K 混 The optimal range is K 混 ≥0.35, Ac 混 The optimal range is 0.75≤Ac 混 ≤0.80, substituting into equation 2, equation 4 and equation 5, we can get:

[0094] X 1 =9.8%~12.5%,X2 =9.6%~20.4%,X 3 =67.1~80.6%.

[0095] 3) According to the optimal phosphate rock powder ratio obtained in step 2), take X 1 =11.0%,X 2 =15.0%,X 3 =74.0% for batching, the two phosphate rock powders are mixed evenly and then sent to fine grinding equipment, finely ground to 0.15mm with a passing rate of 90%, to obtain composite finely ground phosphate rock powder.

[0096] 4) The composite finely ground phosphate rock powder obtained in step 3) is formed into pellets of 15 to 25 mm using a disc pelletizer or a cylinder pelletizer, and then sent to a roasting device, roasted at 1000° C. for 10 minutes after a drying stage, and then cooled and sieved to obtain phosphate rock powder pellets.

[0097] Example 3

[0098] A method for preparing pellets from composite phosphate rock powder, the method comprising the following steps:

[0099] 1) Sampling two kinds of phosphate rock powder, grinding the samples to 0.15 and passing rate 90% respectively, to obtain finely ground phosphate rock powder, and the maximum capillary water and maximum molecular water of the finely ground sample of the first kind of phosphate rock powder are detected, respectively. 毛1 =32.19%, W 分1 =11.4%, the maximum capillary water and maximum molecular water of the second phosphate rock powder finely ground sample were W 毛2 =18.67%, W 分2 =4.1%; Detection of SiO2 in the first type of phosphate rock powder finely ground sample 2 and CaO contents are w sd1 =42.27%, w co1 =28.10%, the SiO content of the second phosphate rock powder finely ground sample was detected 2 and CaO contents are w sd2 =17.66%, w co2 =33.95%.

[0100] 2) According to the relationship between the ball-forming index and proportion of phosphate rock powder and the ball-forming index K and acidity Ac, it can be obtained:

[0101]

[0102]

[0103] X 1 +X 2 =100%……(Formula 5)

[0104] Due to K 混 The optimal range is K 混 ≥0.35, Ac 混 The optimal range is 0.75≤Ac 混 ≤0.80, substituting into equation 2, equation 4 and equation 5, we can get:

[0105] Substituting into equation 2 and equation 5, we can get: X 1 ≥0.288; Substituting into equation 4 and equation 5, we get: 0.546≤X 1 ≤0.594;

[0106] That is X 1 =27%~32%,X 2 =68%~73%.

[0107] 3) According to the optimal phosphate rock powder ratio obtained in step 2), take X 1 =30%, X 2 =70% for batching, the two phosphate rock powders are evenly mixed and sent to the fine grinding equipment, finely ground to 0.15mm with a passing rate of 90%, to obtain composite finely ground phosphate rock powder.

[0108] 4) The composite finely ground phosphate rock powder obtained in step 3) is formed into pellets of 15 to 25 mm using a disc pelletizer or a cylinder pelletizer, and then sent to a roasting device, roasted at 1000° C. for 10 minutes after a drying stage, and then cooled and sieved to obtain phosphate rock powder pellets.

[0109] Comparative Example 1

[0110] The second phosphate rock powder in Example 1 is directly finely ground to 0.15 mm with a pass rate of 90%, and then a disc pelletizer or a cylinder pelletizer is used to form 15-25 mm pellets, which are then sent to a roasting device. After the drying stage, they are roasted at 1000°C for 10 minutes, and after cooling and screening, phosphate rock powder pellets are obtained.

[0111] Comparative Example 2

[0112] Repeat Example 1, except that X 1 =40%,X 2 =60% to obtain phosphate rock powder pellets, in which K = 0.31 and Ac = 0.61.

[0113] Comparative Example 3

[0114] Repeat Example 1, except that X 1 =70%,X 2 =30% was used for batching to obtain phosphate rock powder pellets, in which K = 0.38 and Ac = 0.92.

[0115] Comparative Example 4

[0116] Repeat Example 1, except that X 1 =60%,X 2 =40% was used for batching to obtain phosphate rock powder pellets, in which K = 0.36 and Ac = 0.81.

[0117] Comparative Example 5

[0118] The first type of phosphate rock in Example 1 was crushed, screened, dried and homogenized to prepare phosphate rock powder with a weight percentage moisture content of 5% and a particle size of ≤10 mm. The phosphate rock powder was sent to a ball mill to be ground to a particle size of ≤0.1 mm. The phosphate rock powder was then added to a disc granulator and the solid content of 15% by weight was prepared by evenly adding the acid slag obtained from the intermediate product of the dihydrate wet-process phosphoric acid production. 2 O 5 The weight percentage of the binder is 46%, and the weight ratio of the binder to the phosphate rock powder is 3:7, so that the phosphate rock powders are bonded to each other to form phosphate ore pellets with a particle size of 20 mm. The phosphate ore pellets enter a chain grate roasting machine, are introduced into the tail gas of the phosphorus furnace, and are roasted at 850°C for 20 minutes. The pellets then enter a chain grate cooler and are cooled to below 70°C by air to form phosphate ore pellets.

[0119] Example 6

[0120] The first type of phosphate rock in Example 1 was taken, and the phosphate rock was crushed, screened, dried and homogenized to prepare phosphate rock powder with a moisture content of 9% and a particle size of ≤10 mm. The phosphate rock powder was sent to a ball mill to grind the phosphate rock powder to a particle size of ≤1 mm. The phosphate rock powder was taken, and 5% of the solid weight of the aqueous polymer, 15% of the furfural residue, 0.5% of the gallic acid, and 15% of the fly ash were added, mixed evenly, and then finely ground to 0.05 mm and a specific surface area of ​​1300 cm 2 / g to obtain a finely ground mixture; then add 1.5% by weight of bentonite binder and 5% by weight of fuel to the finely ground mixture, mix evenly, add water to moisten it so that the phosphate rock powders adhere to each other, control the moisture content of the pellets to 8%, and then control the particle size of the pellets to be 10-20 mm through pelletizing and pelletizing; coat the surface of the pellets with a layer of fuel, load them into a chain grate roasting machine, roast them at 900°C for 30 minutes, cool, crush and sieve, and finally cool them to below 100°C to obtain phosphate rock pellets with a particle size of 10-20 mm.

[0121] The drop strength and compressive strength of the phosphate rock powder pellets prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were tested. The results are shown in Table 1.

[0122] Table 1

[0123] <![CDATA[Drop strength (times / 0.5m -1 )]]> Compressive strength(N) Example 1 5.5 28 Example 2 5.3 25 Example 3 6.1 27 Comparative Example 1 2.8 8 Comparative Example 2 3.8 17 Comparative Example 3 4.0 14 Comparative Example 4 4.1 16 Comparative Example 5 6.0 30 Comparative Example 6 6.5 32

[0124] In combination with the above embodiments and comparative examples, it can be seen that the method for preparing pellets with composite phosphate rock powder provided by the present invention calculates the optimal ratio range of various phosphate rock powders by controlling the spheroidization index of the mixture of the composite phosphate rock powder and the acidity of the mixture. The drop strength and compressive strength performance are similar to those of the phosphate rock pellets using a binder in the prior art, achieving the goal of making the drop strength, compressive strength and other properties of the raw balls meet the production requirements without using a binder. At the same time, the acidity value of the pellets is close to the requirements of yellow phosphorus electric furnace smelting, and the amount of raw flux directly added is reduced.

Claims

1. A method for preparing pellets from composite phosphate rock powder, characterized in that: The method comprises the following steps: 1) Detect the ball-forming moisture content and silicon-calcium content in several types of phosphate rock powders, and classify the phosphate rock powders according to the different ball-forming moisture content and silicon-calcium content in the phosphate rock powders; 2) batching the various phosphate rock powders obtained in step 1) according to a set mixture balling index and a set mixture balling acidity index to obtain a mixture; 3) The mixed material obtained in step 2) is finely ground to obtain composite finely ground phosphate rock powder, and the composite finely ground phosphate rock powder is successively subjected to balling, roasting, cooling, and screening to obtain phosphate rock powder pellets.

2. The method according to claim 1, characterized in that: The detection in step 1) is as follows: sampling each type of phosphate rock powder, grinding it and detecting the spherical moisture content and silicon-calcium content therein; Preferably, the spherical moisture content in step 1) refers to the maximum capillary water content W of the phosphate rock powder. 毛 , wt% and the maximum molecular water content of phosphate rock powder W 分 , wt%; the silicon-calcium content refers to the SiO2 content of the phosphate rock powder W sd , wt% and CaO content of phosphate rock powder W co , wt%.

3. The method according to claim 1 or 2, characterized in that: Step 2) Mixing ball index K 混 The calculation method is as follows: Substitute the phosphate rock powder ball index obtained in step 1) into the test to obtain: In the formula, K 混 W is the balling index of the mixture; 分n is the largest molecular water of the nth type of phosphate rock powder, %; W 毛n is the maximum capillary water content of the nth type of phosphate rock powder, %; X n is the ratio of the nth type of phosphate rock powder, %.

4. The method according to claim 3, characterized in that: Step 2) The mixed ball acidity index Ac 混 The calculation method is as follows: Bring in the phosphate rock powder balling index obtained in step 1): In the formula, Ac 混 W is the balling acidity index of the mixture; sdn is the SiO2 content of the nth type of phosphate rock powder, %; W con is the CaO content of the nth type of phosphate rock powder, %; X n is the ratio of the nth type of phosphate rock powder, %; In formula (2) and formula (4), X1+X2+…+X n =100%……(Formula 5).

5. The method according to any one of claims 1 to 4, characterized in that: The mixing ball index K 混 The limited range is K 混 ≥0.35, preferably K 混 ≥0.40; and / or The mixed ball acidity index Ac 混 The limited range is 0.70≤Ac 混 ≤0.85, preferably 0.75≤Ac 混 ≤0.

80.

6. The method according to any one of claims 1 to 5, characterized in that: The batching described in step 2) is: batching the ore according to the optimal phosphate rock powder ratio calculated in step 2).

7. The method according to any one of claims 1 to 6, characterized in that: The fine grinding in step 3) is as follows: the composite phosphate rock powder is finely ground to a 0.15 mm passing rate of 80% to 95%, preferably 85% to 90%; and / or The pelletizing step 3) is as follows: the composite phosphate rock powder is made into pellets of 12 to 30 mm, preferably 15 to 25 mm; and / or Step 3) the calcination temperature is 950-1050°C, preferably 970-1030°C; the calcination time is 6-15 min, preferably 7-13 min; and / or The screening in step 3) is as follows: the cooled pellets are screened using a vibrating screen with an aperture of 20-30 mm and 12-20 mm, wherein the pellets on the 20-30 mm aperture screen are finished phosphate ore pellets, and the pellets on the 12-20 mm aperture screen are used as finished phosphate ore pellets and / or roasting base materials.

8. The method according to any one of claims 1 to 7, characterized in that: The step 1) specifically comprises: sampling several kinds of phosphate rock powder, grinding the samples to 0.15 mm with a passing rate of 80% to 95% (preferably 85% to 90%), obtaining finely ground phosphate rock powder, and detecting the maximum capillary water content W of each finely ground phosphate rock powder. 毛 ,%、Maximum molecular water W 分 ,%、SiO2contentW sd ,%CaO content W co , %, and classify them.

9. The method according to any one of claims 1 to 8, characterized in that: The step 2) specifically comprises: detecting the maximum capillary water content W of each finely ground phosphate rock powder obtained in step 1) 毛 ,%、Maximum molecular water W 分 ,%、SiO2contentW sd ,%CaO content W co , %, as well as the calculation method and limited range of the mixing ball index K and the mixing ball acidity index Ac, to obtain the optimal phosphate rock powder ratio, and mix the ingredients according to the optimal phosphate rock powder ratio to obtain a mixture.

10. The method according to any one of claims 1 to 9, characterized in that: The step 3) is specifically as follows: the mixed material obtained in step 2) is fed into a fine grinding device, and finely ground to a 0.15 mm pass rate of 80% to 95% (preferably 85% to 90%) to obtain composite finely ground phosphate rock powder, and the composite finely ground phosphate rock powder is formed into pellets of 12 to 30 mm (preferably 15 to 25 mm) using a disc pelletizer or a cylinder pelletizer, and then fed into a roasting device, and after a drying stage, roasted at 950 to 1050° C. (preferably 970 to 1030° C.) for 6 to 15 minutes (preferably 7 to 13 minutes), and after cooling and screening, phosphate rock powder pellets are obtained.

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