A composite binder for metallurgical pelletizing

Abstract

The application discloses a composite binder for metallurgical pelletizing, and the mass ratio of components of the composite binder comprises the following components: bentonite 30-40 parts, potassium / sodium water glass 4-8 parts, modified corn starch 20-30 parts, calcium lignosulfonate 6-12 parts, attapulgite clay 10-20 parts, pore-forming agent 2-6 parts, and slag blending agent 5-20 parts. The sodium content of the composite binder is extremely low, the composite binder has good binding effect, can effectively enhance the strength of wet pellets and dry pellets, effectively reduce the high-temperature burst rate and the pulverization rate of the pellets, and improve the pelletizing effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgical pellet, in particular to a composite binder for metallurgical pelletizing used in metallurgical pelletizing. BACKGROUND

[0002] At present, there are mainly two ways for recycling and utilizing the iron-containing dust and sludge in China. One is to add them into sintering materials for sintering by dry or wet method, and the other is to pelletize. The rotary hearth furnace process for producing metallized pellets is a pelletizing process which can effectively utilize iron, carbon and other elements in the iron-containing dust and sludge and has good treatment effect.

[0003] The iron-containing dust and sludge are classified into raw material dust, sintering dust, gas sludge, blast furnace dust, blast furnace ash and iron oxide scale according to different processes in the steel production process. The properties and characteristics of various dusts are different, and the physical and chemical characteristics also have great differences, which brings great difficulty to the manufacture of metallized pellets for recycling and utilization. The balling effect of the iron-containing dust and sludge directly affects the yield and quality of the metallized pellets. Therefore, improving the balling effect of the iron-containing dust and sludge is one of the difficulties in the field.

[0004] Adding a binder is the main means to improve the balling effect of the iron-containing dust and sludge at present. The binders currently used for metallized pellets mainly include inorganic binders, organic binders and composite binders. The inorganic binders mainly include bentonite and water glass, the organic binders mainly include starch and high molecular polymer, and the composite binder is obtained by compounding the inorganic binder and the organic binder. The bentonite is the most widely used binder at present, which has low cost and good binding effect, but has the problems of pellet burst and pulverization. The binding property of water glass is very excellent, but it contains sodium element which is easy to cause corrosion of the furnace body. The organic binder can significantly improve the wet ball strength, but it is easy to ablate and decompose, and has high cost. Although the composite binder can effectively integrate the advantages of the inorganic binder and the organic binder, the existing composite binder still has the problems of insufficient pellet strength, high-temperature burst and pulverization when manufacturing metallized pellets. SUMMARY

[0005] In order to solve at least one of the above technical problems, a binder with very low sodium content, which can effectively enhance the strength of wet ball and dry ball, effectively reduce the high-temperature burst rate and pulverization rate of the pellets, and improve the balling effect, is developed. The present application provides a composite binder for metallurgical pelletizing.

[0006] The present application provides a composite binder for metallurgical pelletizing, the mass fraction of each component of the composite binder is as follows: bentonite 30-40 parts, potassium / sodium water glass 4-8 parts, modified corn starch 20-30 parts, calcium lignosulfonate 6-12 parts, attapulgite clay 10-20 parts, pore-forming agent 2-6 parts, and slag modifier 5-20 parts.

[0007] Optionally, the mass ratio of each component of the composite binder comprises: bentonite 34-36 parts, potassium / sodium water glass 5-7 parts, modified corn starch 24-26 parts, calcium lignosulfonate 8-10 parts, attapulgite clay 16-18 parts, pore-forming agent 3-4 parts, and slag modifier 8-10 parts.

[0008] Optionally, the potassium / sodium molar ratio of the potassium / sodium water glass is 4.2-4.8:1.

[0009] Optionally, the modified corn starch is corn starch mixed with borax after pre-gelatinization.

[0010] Further optionally, in the modified corn starch, the mixed amount of borax accounts for 1.6-2% of the total mass of the modified corn starch.

[0011] Optionally, the calcium lignosulfonate is calcium lignosulfonate modified by acrylamide copolymerization.

[0012] Further optionally, the preparation of the calcium lignosulfonate modified by acrylamide copolymerization comprises the following steps:

[0013] S1, acrylamide and calcium lignosulfonate are mixed in a mass ratio of 2-3:1, and potassium persulfate initiator is added;

[0014] S2, control the reaction temperature to be 70-75℃, and react for more than 4h to obtain the calcium lignosulfonate modified by acrylamide copolymerization.

[0015] Optionally, the particle size of the bentonite is controlled to be 200-240 mesh, the particle size of the modified corn starch is controlled to be 80-120 mesh, and the particle size of the attapulgite clay is controlled to be 200-240 mesh.

[0016] Optionally, the pore-forming agent is ammonium bicarbonate.

[0017] Optionally, the slag modifier is selected from at least two of calcium silicate, magnesium silicate, calcium bicarbonate, magnesium bicarbonate, calcium stearate and magnesium stearate.

[0018] In summary, the present application includes at least one of the following beneficial technical effects:

[0019] 1. The present application uses bentonite and modified corn starch as main raw materials, and adds a small amount of potassium / sodium water glass, calcium lignosulfonate and attapulgite clay, which has excellent bonding performance, can effectively improve the wet ball and dry ball strength of the metallized pellet, and has extremely low sodium content and extremely low corrosion to the furnace body.

[0020] 2. The application adds a small amount of pore-forming agent, which can form pores inside the manufactured metallized pellets; in addition, the potassium / sodium water glass of the application can form a network structure with attapulgite clay and bentonite at high temperature, which can effectively enhance the bonding performance, and also effectively reduce the high-temperature burst rate and the pulverization rate of the metallized pellets.

[0021] 3. The main components of the application are bentonite and starch, and high-cost polymers are not used, so the overall cost is relatively low. DETAILED DESCRIPTION

[0022] The application will be further described in detail below in combination with examples.

[0023] Unless otherwise specified, the raw materials used in the application are conventional raw materials in the technical field, which can be purchased in the market. In the test method and detection method of the following examples, if not specifically stated, they are conventional methods, and the instruments used in the test can be obtained through commercial channels. The parts not described in detail in the specification belong to the prior art.

[0024] The application provides a composite binder for metallurgical balling, and the mass fraction ratio of each component of the composite binder comprises: 30-40 parts of bentonite, 4-8 parts of potassium / sodium water glass, 20-30 parts of modified corn starch, 6-12 parts of calcium lignosulfonate, 10-20 parts of attapulgite clay, 2-6 parts of pore-forming agent, and 5-20 parts of slag modifier.

[0025] At present, the binder of the metallized pellet in the prior art is mainly bentonite with low cost. When the pellet is manufactured, 5% of bentonite is added, and the binding effect is good, and the strength of the wet ball and the dry ball can meet the requirements. However, the metallized pellet manufactured by the bentonite binder has a high high-temperature burst rate, and also has a certain pulverization problem.

[0026] The water glass binder is a relatively excellent building material binder, which has excellent binding effect, and can form a network structure, has excellent curing effect, and can inhibit the burst rate and the pulverization rate. However, the main component of the water glass is sodium silicate, and the sodium element can cause corrosion to the refractory material in the furnace body, and the manufacture of the metallized pellet has the problem of corroding the furnace body.

[0027] Although the organic binder can improve the strength of the wet ball and the dry ball and reduce the pulverization rate, the metallized pellet manufactured by the organic binder will rapidly pyrolyze and ablate under high-temperature conditions, release a large amount of gas, and cause burst.

[0028] The bentonite and modified corn starch are used as main components, a certain amount of potassium / sodium water glass, calcium lignosulfonate and attapulgite clay are added as binding aids, the sodium element content is controlled, the strength of the manufactured metallized pellets is effectively improved, and the network structure is formed at high temperature, so that the high temperature burst rate and the pulverization rate are effectively reduced.

[0029] The following are the preparation examples and embodiments of the present application.

[0030] The main raw materials used in the preparation examples and embodiments of the present application are all commercially available.

[0031] Among them, the bentonite is 200-240 mesh, purchased from Jianping Cuiyan Bentonite Co., Ltd.; the modified corn starch is pre-gelatinized modified corn starch, 80-120 mesh, purchased from Hubei Zhongyu Chemical Co., Ltd.; the potassium / sodium water glass is purchased from Zibo Hongye Fine Chemical Co., Ltd., with potassium / sodium molar ratio of 4:1, 4.2:1, 4.5:1, 4.8:1 and 5:1; the calcium lignosulfonate is purchased from Hubei Nuona Technology Co., Ltd.; the attapulgite clay is purchased from Hubei Wande Chemical Co., Ltd.; the pore-forming agent is ammonium bicarbonate, purchased from Jinan Shidada Chemical Co., Ltd.

[0032] Preparation Example 1

[0033] The modified corn starch of the present preparation example is prepared by mixing pre-gelatinized modified corn starch and borax, and the mixing amount of borax accounts for 1.4% of the total mass of the modified corn starch.

[0034] Preparation Example 2

[0035] The modified corn starch of the present preparation example is prepared by mixing pre-gelatinized modified corn starch and borax, and the mixing amount of borax accounts for 1.6% of the total mass of the modified corn starch.

[0036] Preparation Example 3

[0037] The modified corn starch of the present preparation example is prepared by mixing pre-gelatinized modified corn starch and borax, and the mixing amount of borax accounts for 2.0% of the total mass of the modified corn starch.

[0038] Preparation Example 4

[0039] The modified corn starch of the present preparation example is prepared by mixing pre-gelatinized modified corn starch and borax, and the mixing amount of borax accounts for 2.2% of the total mass of the modified corn starch.

[0040] Preparation Example 5

[0041] The preparation of the modified calcium lignosulfonate of the present preparation example includes the following steps:

[0042] S1, acrylamide and calcium lignosulfonate are mixed in a mass ratio of 1.8:1, and 1% of potassium persulfate initiator is added;

[0043] S2, control the reaction temperature 70~75℃, reaction 4h, prepared by acrylamide copolymerization modified calcium lignosulfonate.

[0044] Preparation Example 6

[0045] The preparation of modified calcium lignosulfonate of the present preparation example includes the following steps:

[0046] S1, acrylamide and calcium lignosulfonate are mixed in a mass ratio of 2:1, and 1% potassium persulfate initiator is added;

[0047] S2, control the reaction temperature 70~75℃, reaction 4h, prepared by acrylamide copolymerization modified calcium lignosulfonate.

[0048] Preparation Example 7

[0049] The preparation of modified calcium lignosulfonate of the present preparation example includes the following steps:

[0050] S1, acrylamide and calcium lignosulfonate are mixed in a mass ratio of 3:1, and 1% potassium persulfate initiator is added;

[0051] S2, control the reaction temperature 70~75℃, reaction 4h, prepared by acrylamide copolymerization modified calcium lignosulfonate.

[0052] Preparation Example 8

[0053] The preparation of modified calcium lignosulfonate of the present preparation example includes the following steps:

[0054] S1, acrylamide and calcium lignosulfonate are mixed in a mass ratio of 3.2:1, and 1% potassium persulfate initiator is added;

[0055] S2, control the reaction temperature 70~75℃, reaction 4h, prepared by acrylamide copolymerization modified calcium lignosulfonate.

[0056] Example 1

[0057] The composite binder for metallurgical pelletizing of the present example, the mass fraction of each component of the composite binder includes: bentonite 30 parts, potassium / sodium water glass 4 parts (potassium / sodium molar ratio 4.2:1), pregelatinized modified corn starch 20 parts, calcium lignosulfonate 6 parts, attapulgite clay 10 parts, pore-forming agent 2 parts, and slag modifier 5 parts (calcium bicarbonate and magnesium stearate are mixed in a mass ratio of 1:1 to prepare).

[0058] Example 2

[0059] The composite binder for metallurgical pelletizing of the present embodiment has a mass ratio of the components as follows: bentonite 40 parts, potassium / sodium water glass 8 parts (potassium / sodium molar ratio 4.2:1), pregelatinized modified corn starch 30 parts, calcium lignosulfonate 12 parts, attapulgite clay 20 parts, pore-forming agent 6 parts, and slag modifier 20 parts (obtained by mixing calcium bicarbonate and magnesium stearate in a mass ratio of 1:1).

[0060] Example 3

[0061] The composite binder for metallurgical pelletizing of the present embodiment has a mass ratio of the components as follows: bentonite 40 parts, potassium / sodium water glass 4 parts (potassium / sodium molar ratio 4.2:1), pregelatinized modified corn starch 30 parts, calcium lignosulfonate 6 parts, attapulgite clay 10 parts, pore-forming agent 4 parts, and slag modifier 15 parts (obtained by mixing calcium bicarbonate and magnesium stearate in a mass ratio of 1:1).

[0062] Example 4

[0063] The composite binder for metallurgical pelletizing of the present embodiment has a mass ratio of the components as follows: bentonite 34 parts, potassium / sodium water glass 5 parts (potassium / sodium molar ratio 4.2:1), pregelatinized modified corn starch 24 parts, calcium lignosulfonate 8 parts, attapulgite clay 16 parts, pore-forming agent 3 parts, and slag modifier 8 parts (obtained by mixing calcium bicarbonate and magnesium stearate in a mass ratio of 1:1).

[0064] Example 5

[0065] The composite binder for metallurgical pelletizing of the present embodiment has a mass ratio of the components as follows: bentonite 36 parts, potassium / sodium water glass 7 parts (potassium / sodium molar ratio 4.2:1), pregelatinized modified corn starch 26 parts, calcium lignosulfonate 10 parts, attapulgite clay 18 parts, pore-forming agent 4 parts, and slag modifier 10 parts (obtained by mixing calcium bicarbonate and magnesium stearate in a mass ratio of 1:1).

[0066] Example 6

[0067] The composite binder for metallurgical pelletizing of the present embodiment has a mass ratio of the components as follows: bentonite 35 parts, potassium / sodium water glass 6 parts (potassium / sodium molar ratio 4.2:1), pregelatinized modified corn starch 25 parts, calcium lignosulfonate 9 parts, attapulgite clay 17 parts, pore-forming agent 3.5 parts, and slag modifier 9 parts (obtained by mixing calcium bicarbonate and magnesium stearate in a mass ratio of 1:1).

[0068] Example 7

[0069] The present embodiment differs from Example 6 in that the modified corn starch of Preparation Example 3 is used.

[0070] Example 8

[0071] The difference between this example and Example 7 is that the modified calcium lignosulfonate of Preparation 7 is used.

[0072] Comparative Example 1

[0073] The binder of this comparative example uses bentonite with a particle size of 200-240 mesh.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 8 is that an equal amount of bentonite is used to replace the potassium / sodium water glass.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 8 is that an equal amount of magnesium lignosulfonate is used to replace the attapulgite clay.

[0078] Comparative Example 4

[0079] The difference between this comparative example and Example 8 is that no pore-forming agent is added.

[0080] Performance detection

[0081] The iron-containing dust and sludge used in the examples of the present application is a metallurgical iron-containing mixed dust and sludge from a certain steel plant. The main chemical elements detected are: Fe 44.8%, Ca 14.2%, Mg 8.7%, Si 6.4%, Zn 4.9%, S≤0.5%, P≤0.5%.

[0082] The binders prepared in Examples 1-8 and Comparative Examples 1-4 of the present application are used to produce metallized pellets, with the binder addition amount being 5%. The wet ball strength, dry ball strength, dry ball pulverization rate, high temperature bursting rate and pulverization rate of the prepared metallized pellets are detected.

[0083] The method for producing metallized pellets uses the following steps:

[0084] Sa, the binder is mixed with the iron-containing dust and sludge, and mechanically ground and mixed for 30 min to obtain a mixture;

[0085] Sb, the mixture is sprayed with atomized water to wet it, with the water amount being 10% of the mixture to obtain a wetted mixture;

[0086] Sc, the wetted mixture is added to a disc pelletizer to pelletize, with the pellet size being controlled at 8-16 mm to obtain wet pellets;

[0087] Sd, the wet pellets are placed in a hot air dryer, heated to 200°C at a heating rate of 8°C, and dried for 30 min to obtain dry pellets.

[0088] Detection method:

[0089] According to each example and comparative example, 100 wet balls and dry balls with a particle size of 10-11 mm were taken respectively, and the average compressive strength and 500 mm drop times were detected, and the average pulverization rate of the dry balls was detected.

[0090] According to each example and comparative example, 100 dry balls were taken, and the dry balls were high-temperature calcined at a temperature of 1250°C for 30 min, and the burst rate was detected.

[0091] The obtained detection results are shown in Table 1 below.

[0092] Table 1 Detection results of examples 1-8 and comparative examples 1-4

[0093]

[0094] As can be seen from the data in Table 1, compared with the binders of comparative examples 1-4, the strength of the metallized pellets of wet balls and dry balls manufactured by using the binders of examples 1-8 is obviously improved, and the high-temperature burst rate and the pulverization rate are also extremely obviously reduced. It can be seen that the binder of the present application has very excellent binding effect, and the manufactured metallized pellets have extremely excellent balling performance.

[0095] As can be seen from the comparison of the data of examples 1-8 in Table 1, after further optimizing the ratio of the binder, the binding effect of examples 4-6 is obviously better than that of examples 1-3; after mixing borax into the modified corn starch, the binding effect of example 7 is obviously better than that of examples 4-6; after using modified calcium lignosulfonate, the binding effect of example 8 is obviously better than that of example 7.

[0096] As can be seen from the comparison of the data of example 8 and comparative examples 2-4 in Table 1, the burst rate of comparative examples 2-4 is obviously higher than that of example 8.

[0097] It can be seen that the adhesive effect of the adhesive is further obviously improved after the modified corn starch mixed with borax is used and the modified calcium lignosulfonate is used. The applicant analyzes and speculates that the decomposition temperature of the corn starch and the decomposition temperature of the calcium lignosulfonate in the adhesive of the present application can form a gradient with the high-temperature degassing temperature of the attapulgite clay. The attapulgite clay releases part of the gas at a high temperature of 250 DEG C or above; the corn starch releases gas at a temperature of 250-650 DEG C, and pyrolysis releases gas at a temperature of 450 DEG C or above; and the calcium lignosulfonate pyrolysis releases gas at a temperature of 650 DEG C or above. Such a gradient can make the pellets have a continuous and gradual gas overflow process at a high temperature, and the gas produced under high-temperature conditions can be gradually released in the pores formed by the pore-forming agent, thereby effectively reducing the occurrence rate of burst. In addition to the obvious improvement in the adhesive property, the borax mixed with the modified corn starch can form a network structure with the potassium / sodium water glass under high-temperature conditions, effectively maintaining the strength of the pellets under high temperature, and further reducing the occurrence rate of burst. The adhesive property of the modified calcium lignosulfonate is obviously improved compared with the calcium lignosulfonate, and it can form cross-linking with the corn starch, thereby reducing the pulverization rate and further effectively improving the strength of the wet and dry pellets.

[0098] Based on Example 8, the present application further studies the potassium / sodium ratio of the potassium / sodium water glass, the borax mixed with the modified corn starch, and the modification method of the modified calcium lignosulfonate.

[0099] The following are Examples 9-18 of the present application.

[0100] Example 9

[0101] The difference between this example and Example 8 is that the potassium / sodium water glass with a potassium / sodium molar ratio of 4:1 is used.

[0102] Example 10

[0103] The difference between this example and Example 8 is that the potassium / sodium water glass with a potassium / sodium molar ratio of 4.5:1 is used.

[0104] Example 11

[0105] The difference between this example and Example 8 is that the potassium / sodium water glass with a potassium / sodium molar ratio of 4.8:1 is used.

[0106] Example 12

[0107] The difference between this example and Example 8 is that the potassium / sodium water glass with a potassium / sodium molar ratio of 5:1 is used.

[0108] Example 13

[0109] The difference between this example and Example 8 is that the modified corn starch of Preparation Example 1 is used.

[0110] Example 14

[0111] The difference between this example and Example 8 is that the modified corn starch of Preparation Example 2 is used.

[0112] Example 15

[0113] The difference between this example and Example 8 is that the modified corn starch of Preparation Example 4 is used.

[0114] Example 16

[0115] The difference between this example and Example 8 is that the modified calcium lignosulfonate of Preparation Example 5 is used.

[0116] Example 17

[0117] The difference between this example and Example 8 is that the modified calcium lignosulfonate of Preparation Example 6 is used.

[0118] Example 18

[0119] The difference between this example and Example 8 is that the modified calcium lignosulfonate of Preparation Example 8 is used.

[0120] The same tests are performed on Examples 9-18 of the present application, and the test results are shown in Table 2 below.

[0121] Table 2 Test results of Examples 9-18

[0122]

[0123] By comparing the data in Table 2 with the data in Table 1, it can be seen that in the study of potassium / sodium water glass, the effect of Example 12 is significantly lower than that of Example 8, the effect of Example 9 is higher, but the sodium content is further improved, and the effect is limited; in the study of modified corn starch, the effect of Example 13 is significantly lower than that of Example 8, the effect of Example 15 is basically the same as that of Example 8; in the study of modified calcium lignosulfonate, the effect of Example 16 is significantly lower than that of Example 8, the effect of Example 17 is not much different from that of Example 8, and the effect of Example 18 is basically the same as that of Example 8.

[0124] It can be seen that under the premise of controlling the content of sodium element, when the potassium / sodium ratio of potassium / sodium water glass is 4.2-4.8:1, the bonding performance is relatively optimal; in the modified corn starch, the optimal mixing amount of borax is 1.6-2%; and in the modified calcium lignosulfonate, acrylamide and calcium lignosulfonate are reacted at a mass ratio of 2-3:1, and the modified calcium lignosulfonate obtained has the optimal bonding performance.

[0125] The above are all preferred embodiments of the present application, and do not limit the protection scope of the present application, so that: all equivalent changes made according to the structure, shape, principle of the present application should be covered in the protection scope of the present application.

Claims

1. A composite binder for metallurgical pelletizing, characterized in that, The composite binder comprises the following components in the following mass ratios: 30-40 parts bentonite, 4-8 parts potassium / sodium silicate, 20-30 parts modified corn starch, 6-12 parts calcium lignosulfonate, 10-20 parts attapulgite clay, 2-6 parts pore-forming agent, and 5-20 parts slag material modifier; the potassium / sodium molar ratio of the potassium / sodium silicate is 4.2-4.8:1, and the modified corn starch is pregelatinized corn starch mixed with borax.

2. The composite binder for metallurgical pelletizing according to claim 1, characterized in that, The composite binder comprises the following components in the following proportions by mass: 34-36 parts bentonite, 5-7 parts potassium / sodium water glass, 24-26 parts modified corn starch, 8-10 parts calcium lignosulfonate, 16-18 parts attapulgite clay, 3-4 parts pore-forming agent, and 8-10 parts slag material modifier.

3. The composite binder for metallurgical pelletizing according to claim 1, characterized in that, In the modified corn starch, the amount of borax mixed in accounts for 1.6-2% of the total mass of the modified corn starch.

4. The composite binder for metallurgical pelletizing according to claim 1, characterized in that, The calcium lignosulfonate is acrylamide copolymerized calcium lignosulfonate.

5. The composite binder for metallurgical pelletizing according to claim 4, characterized in that, The preparation of the acrylamide copolymerized calcium lignosulfonate includes the following steps: S1. Mix acrylamide and calcium lignosulfonate in a mass ratio of 2 to 3:1, and add potassium persulfate initiator; S2. Control the reaction temperature to 70~75℃ and react for more than 4 hours to obtain acrylamide copolymerized calcium lignosulfonate.

6. The composite binder for metallurgical pelletizing according to claim 1, characterized in that, The particle size of the bentonite is controlled at 200-240 mesh, the particle size of the modified corn starch is controlled at 80-120 mesh, and the particle size of the attapulgite clay is controlled at 200-240 mesh.

7. The composite binder for metallurgical pelletizing according to claim 1, characterized in that, The pore-forming agent is ammonium bicarbonate.

8. The composite binder for metallurgical pelletizing according to claim 1, characterized in that, The slag blending agent is selected from at least two of calcium silicate, magnesium silicate, calcium bicarbonate, magnesium bicarbonate, calcium stearate, and magnesium stearate.

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