CN113930612A

CN113930612A - Limestone alkaline pellet and preparation process thereof

Info

Publication number: CN113930612A
Application number: CN202111205230.8A
Authority: CN
Inventors: 陈文明; 魏川; 胡刚; 万成; 张鹏; 高丽姗
Original assignee: Sichuan Desheng Group Vanadium Titanium Co Ltd
Current assignee: Sichuan Desheng Group Vanadium Titanium Co Ltd
Priority date: 2021-10-15
Filing date: 2021-10-15
Publication date: 2022-01-14

Abstract

The invention discloses a limestone alkaline pellet, which comprises the following components: iron ore concentrate, dedusting ash, bentonite and flux; wherein the iron concentrate comprises python concentrate, conyon concentrate, hening concentrate, taihe concentrate; python concentrate in iron concentrate: kangmao concentrate: and (4) Anning concentrate: taihe concentrate is 1-4: 1-6:1-4: 1-7; the proportion of the dedusting ash is 1-3% of the total mass; the proportion of the bentonite is 1 to 4 percent of the total mass; the fusing agent is limestone; the alkalinity of the limestone alkaline pellets is 0.5-1.0. The alkalinity of the limestone alkaline pellets is 0.5-1.0. Meanwhile, the alkaline pellets with the alkalinity of 0.8 also optimize the blast furnace burden structure, reduce the alkalinity of sinter and have more use value and practical significance in production.

Description

Limestone alkaline pellet and preparation process thereof

Technical Field

The invention relates to the field of pellets, in particular to limestone alkaline pellets and a preparation process thereof.

Background

Compared with sintered ore, the pellet ore has the characteristics of uniform granularity, good compressive strength and wear resistance, less low-temperature reduction degradation, good reducibility and the like, so that the quantity of the pellet ore added in the domestic and foreign advanced blast furnace smelting is gradually increased, and the pellet ore plays an important role in improving the air permeability of blast furnace burden columns and improving the yield and saving coke. In the blast furnaces in western Europe and Japan, the using amount of the pellet ore is generally 25-50%, some of the pellet ore can reach 70%, the smelting of the pellet ore can reach 100% in North America, and the charging proportion of the pellet ore is improved to different degrees in large blast furnaces such as Chinese steel, Pan steel, Kun steel, horse steel and the like. .

In order to ensure normal production, the sintering needs to produce the ultra-high alkalinity sintering ore (R is 2.7 plus or minus). When the alkalinity of the sintered ore exceeds a certain value, the granularity is refined, the strength is poor, and the influence on the quality of the sintered ore is great. Therefore, the method has practical and profound significance for reducing the alkalinity of the sintered ore, producing the alkaline pellet, increasing the charging proportion of the pellet, improving the metallurgical performance of the blast furnace comprehensive burden and increasing the yield, saving the coke and reducing the cost.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a limestone alkaline pellet which has high compressive strength, low powder content, good low-temperature reduction degradation performance, good reduction performance and good reduction expansion performance and a preparation process thereof.

The invention firstly provides a limestone alkaline pellet, which comprises the following components: iron ore concentrate, dedusting ash, bentonite and flux; wherein the iron concentrate comprises python concentrate, conyon concentrate, hening concentrate, taihe concentrate; python concentrate in iron concentrate: kangmao concentrate: and (4) Anning concentrate: taihe concentrate is 1-4: 1-6:1-4: 1-7; the proportion of the dedusting ash is 1-3% of the total mass; the proportion of the bentonite is 1 to 4 percent of the total mass; the fusing agent is limestone; the alkalinity of the limestone alkaline pellets is 0.5-1.0.

The invention also provides the following optimization scheme:

preferably, the proportion of the fly ash is 1.8 percent of the total mass.

Preferably, the proportion of the bentonite is 1.5-2.0% of the total mass.

The invention also discloses a preparation process of the limestone alkaline pellets, which comprises the following steps:

s1 preparing limestone alkaline pellet ingredients;

s2, adding water, mixing, pelletizing and screening to obtain qualified green pellets;

s3, drying the green pellets;

s4, preheating and roasting the green pellets;

s5, soaking and cooling the baked green pellets to obtain finished products.

The invention also provides the following optimization scheme:

preferably, the temperature for drying in step S3 is 200-500 ℃.

Preferably, the temperature of the preheating in the step S4 is 900-1000 ℃.

Preferably, the temperature of the calcination in step S4 is 1200-1300 ℃.

Preferably, the soaking temperature in step S5 is 1100-1200 ℃.

Preferably, the cooling time in step S5 is 40-60 minutes.

Preferably, the cooling time in step S5 is a cooling time inside and outside the furnace.

Through carrying out basic pellet experiments such as batching, pelletizing and roasting on raw materials and detecting and analyzing the performances of green pellets and finished pellets, the influence of different fluxes, different alkalinity and different bentonite dosage on the performances of the green pellets and the finished pellets is discussed. The conclusion is as follows:

(1) the limestone is used as the flux to produce the alkaline pellet ore, the optimal alkalinity is 0.8, and the flux is different, and the bentonite dosage and the roasting system are different;

(2) the production process of alkaline pellet with limestone as flux includes the following steps: alkalinity of 0.8, bentonite dosage of 2 percent and the 3 rd roasting system;

(3) the comprehensive consideration of the granularity treatment of the flux, the roasting energy consumption, the service life of roasting equipment and the performance of finished pellets is that limestone is selected as the flux in the production of alkaline pellets, which is a scheme with higher cost performance.

Drawings

FIG. 1 shows the S content of alkaline pellets when the amount of bentonite and the roasting system are different;

FIG. 2 shows the FeO content of the alkaline pellets when the amount of bentonite and the roasting system are different.

Detailed Description

In order that those skilled in the art will better understand the technical solutions of the present invention, the present invention will be further described in detail with reference to the following embodiments.

The invention also provides the following optimization scheme:

preferably, the proportion of the fly ash is 1.8 percent of the total mass.

Preferably, the proportion of the bentonite is 1.5-2.0% of the total mass.

s1 preparing limestone alkaline pellet ingredients;

s3, drying the green pellets;

s4, preheating and roasting the green pellets;

s5, soaking and cooling the baked green pellets to obtain finished products.

The invention also provides the following optimization scheme:

preferably, the temperature for drying in step S3 is 200-500 ℃.

Preferably, the temperature of the preheating in the step S4 is 900-1000 ℃.

Preferably, the temperature of the calcination in step S4 is 1200-1300 ℃.

Preferably, the soaking temperature in step S5 is 1100-1200 ℃.

Preferably, the cooling time in step S5 is 40-60 minutes.

The above is a detailed description of the present invention, and the following is an experimental scheme of the present invention.

The requirements for ingredients

The requirements for the batch materials are as follows:

the python, the Congman, the Anning and the Taihe iron ore concentrates respectively account for 1/4 when being mixed;

dust removal ratio: 1.8 percent;

alkalinity: 0.6, 0.8, 1.0;

and (3) proportioning bentonite: 1.5%, 1.8%, 2.0%;

flux: limestone and limestone are respectively adopted. The method comprises the steps of firstly carrying out an alkaline pellet experiment by using limestone as a flux, finding out an optimal alkalinity value, and then carrying out the alkaline pellet experiment by using the limestone as the flux according to the optimal alkalinity value.

Roasting system

The green pellets are roasted by three different roasting systems in the roasting process. The finished pellet is roasted by adopting the roasting schedule shown in the table 1 on the basis of looking up the literature and the early exploration experiment by considering the S content (desulfurization rate in the roasting process) and the FeO content (oxidation degree of the finished pellet) of the finished pellet and belonging to the roasting of vanadium titano-magnetite containing MgO.

TABLE 1 calcination System

Experimental protocol

The experimental scheme is shown in Table 2 according to the material preparation requirement and the roasting system.

TABLE 2 Experimental protocols

Experimental indices and detection thereof

The finished pellet is a smooth gas pill of a blast furnace, and the quality of the pellet has important influence on the smelting process of the blast furnace. The high-quality green pellets are the prerequisite for obtaining high-yield and high-quality pellet ores. Therefore, the project detects the properties of both the green pellets and the finished pellets in the production process of the alkaline pellets. The green pellet properties mainly include falling strength, compressive strength and bursting temperature, and the finished pellet properties mainly include compressive strength, powder content, low-temperature reduction degradation property, reduction property and reduction expansion property.

Green ball performance

The green ball with good quality is required to have proper and uniform granularity, sufficient falling strength and compressive strength and good heat resistance so as to ensure that the green ball does not crack or deform in the processes of transferring, screening, distributing and drying.

Falling strength of green ball

The falling strength of green pellets is an important index for measuring the impact resistance of the green pellets in the transfer process, and is also a basis for allowing the transfer times of the green pellets during the design of a pellet mill. Randomly taking 10 green pellets, respectively and freely dropping each green pellet from the height of 0.5m to a steel plate with the thickness of 10mm, and recording the dropping times of each green pellet when each green pellet cracks or is cracked. The average value of the measurements of 10 balls was used as an index of the falling strength of the green ball.

Compressive strength of green ball

The compressive strength of the green ball reflects the capacity of bearing the dead weight and extrusion of the ball layer in the transferring and stacking processes of the green ball. Randomly taking 20 balls, placing the green balls on an electronic balance, uniformly pressurizing by using a flat disc with the diameter of 150mm until the green balls break, recording the pressure value displayed by the electronic balance at the moment, and regarding the pressure value as the compressive strength of the green balls. Taking 20 balls for determination, and taking the average value of the determination as the green ball compressive strength index.

Cracking temperature of green ball

The bursting temperature is an important index for evaluating the green pellet quality and is important for pellet production, particularly shaft furnace pellet production (at present, pellet production has three forms, namely a shaft furnace, a belt type roasting machine and a chain grate-rotary kiln). For the belt type roasting machine and the chain grate-rotary kiln process, an appropriate drying process can be selected according to the heat sensitivity of green pellets. The burst temperature of the green pellets is increased, so that the burst of the green pellets on a drying bed of the shaft furnace can be reduced, the air permeability of a pellet layer in the shaft furnace is improved, the agglomeration and caking accidents are reduced, and the drying process of a belt type roasting machine and a chain grate-rotary kiln can be enhanced. Higher burst temperatures are more advantageous to speed up the drying process.

If the burst temperature of the green ball is low, the structure of the green ball is damaged during drying, so that the air permeability of a ball layer is deteriorated, the preheating and roasting are difficult, the productivity is reduced, the quality of the finished ball is not uniform, and the ring forming (chain grate-rotary kiln process) and other problems can be caused in serious cases. The green pellet bursting temperature is related to the raw material performance, the binder performance, the pelletizing technological parameters, the drying system and the like, so that the bursting temperature of the corresponding green pellet needs to be measured when the raw material changes, the pelletizing technological parameters change, the drying temperature and the drying airflow speed change every time, so that the technological parameters are adjusted, the green pellet is ensured not to burst in the drying process, and the pellet with good quality is obtained.

Compression strength of pellet

The compressive strength is an important index representing the cold state of the pellet and refers to the corresponding pressure when the pellet is completely broken under a pressure condition.

(ii) standard

Refer to the determination of compressive strength of iron ore pellets for blast furnaces and direct reduction (GB/T14201-2018).

② experimental equipment

Iron ore pelletizing pressure measurement machine.

(iii) Experimental Process

60 pellet samples were randomly taken, dried in an oven (105. + -. 5 ℃ C.) and cooled to room temperature before the experiment. A sample (single ball) was placed in the center of the lower platen, and the sample was loaded by moving the upper platen downward at a speed of 15mm/min throughout the experiment. The maximum load at which the sample completely ruptures under load is noted and is reported in units of (deca newtons) with the result being accurate to one decimal.

Powder content of pellet

At present, iron ore concentrate is treated by a pelletizing method and is made into pellets for blast furnace smelting. The powder content of the pellets is inevitably increased again by the friction and impact in the processes of screening, transferring and warehousing, the powder content of the pellets in the warehouse in China is generally between 20% and 35% at most and is nearly 60% at present through detection, the amount of the pellets required by a large-scale blast furnace of 4350m3 per day is 3000kg +/-and about 1000kg of pellet ore powder is eaten by the blast furnace every day, the powder content of lump ore required by the blast furnace is also high, the compactness of the ore powder is high, the air permeability is poor, the air permeability of a blast furnace charge column is influenced, and certain negative influence is caused on the production of the blast furnace. Therefore, the reduction of the powder content of the pellet is undoubtedly an important measure for ensuring the stable, smooth and high-yield production of the blast furnace.

(ii) standard

There is no uniform standard.

② experimental equipment

Rotating drum (phi 130 x 200).

(iii) Experimental Process

And weighing 500g of the roasted pellets, putting the pellets into a rotary drum, covering an end cover, and rotating at the rotating speed of 30r/min for 10 minutes. After stopping, all the samples were taken out from the drum, sieved with sieves having openings of 5mm and 0.5mm, and the oversize was weighed to calculate the powder content.

Metallurgical performance of finished alkaline pellet ore

Low-temp. reduction degradation performance of pellet

In the blast furnace ironmaking process, when iron ore enters a blast furnace and is reduced to a temperature of 400-600 ℃, the iron ore is subjected to the reduction action of coal gas from the lower part of the blast furnace, and is cracked and pulverized to different degrees, and when the iron ore is serious, the air permeability of a material column on the upper part of the blast furnace is influenced, and the smooth operation of the furnace is damaged. The characteristic of the iron ore that the iron ore is cracked and pulverized in the low-temperature (400-600 ℃) reduction process is generally expressed by a low-temperature Reduction Degradation Index (RDI).

Procedure of experiment

Bottled high-purity CO, CO2 and N2 are used for preparing reducing gas. Drying the sample at 105 +/-5 ℃ for more than 2h, and then cooling to room temperature. 500g of a sample is weighed and placed into a reduction tube, N2 with the standard state flow rate of 5L/min is introduced, and the reduction tube is placed into a reduction furnace (the temperature in the furnace is less than 200 ℃). Heating, controlling the speed within 10 ℃/min, increasing the flow of N2 to 15L/min when the temperature is 500 ℃, and keeping the temperature at 500 ℃ for 30min to keep the temperature constant between 500 +/-5 ℃. Then introducing reducing gas with standard flow of 15L/min +/-0.5L/min to replace N2, and continuously reducing for 1 h. After reducing for 1h, introducing N2 with standard flow of 5L/min, and taking the reducing pipe out of the furnace. And (3) when the sample is cooled to be below 100 ℃, taking out the sample, putting the sample into a rotary drum, rotating the rotary drum at the rotating speed of 30 +/-1 r/min for 300 revolutions, pouring out the sample, sieving the sample for 60 seconds by using sieves with 6.30mm, 3.15mm and 0.5mm meshes, and weighing the sample.

Reduction performance of pellets

The quality of the reducing performance of the iron ore directly influences the technical and economic indexes such as the yield, the coke ratio and the like of blast furnace iron making. The iron ore reduction performance represents the difficulty of the oxygen combined with iron in the iron ore being taken by the gas reducing agent, is an important metallurgical performance of the iron ore, takes the reduction degree of 180min as an assessment index and is represented by RI.

Procedure of experiment

Bottled high-purity CO and N2 are used for preparing reducing gas. Drying the sample at 105 +/-5 ℃ for more than 2h, and then cooling to room temperature. 500g of a sample is weighed and placed into a reduction tube, N2 with the standard state flow rate of 5L/min is introduced, and the reduction tube is placed into a reduction furnace (the temperature in the furnace is less than 200 ℃). Heating, controlling the speed within 10 ℃/min, increasing the flow of N2 to 15L/min when the temperature is 900 ℃, and keeping the temperature at 900 ℃ for 30min to keep the temperature constant between 900 +/-5 ℃. Then introducing reducing gas with standard flow of 15L/min +/-0.5L/min to replace N2, and continuously reducing for 3 h. And after reducing for 3h, introducing N2, wherein the standard state flow is 15L/min, closing N2 after 5min, taking the reducing pipe out of the furnace, and ending the experiment.

Reduction expansion performance of pellet

The reduction swelling property refers to a property of the pellets to generate volume swelling during the reduction process. It is an important metallurgical property of pellet ore. The percentage of volume change of the pellets before and after reduction in the temperature zone of the blast furnace is generally used as an index of the reduction-expansion performance.

From expansion index VFS

18 pellets with the particle size of 10.0-12.5 mm are taken and placed in a fixed bed, 15L/min of reducing gas consisting of 30% of CO and 70% of N2 is introduced, the pellets are reduced for 1 hour at 900 ℃ to be freely expanded, and then the pellets are cooled to the room temperature. The free expansion index VFS was characterized by the rate of change of the volume of the pellets before and after reduction.

Results of the experiment

Green ball performance test results and analysis

The results of the examination of the green pellet properties are shown in Table 7.2. As can be seen from Table 7.2, the effect of the amount of bentonite on the performance of the spheroids is more pronounced. The smaller the amount of bentonite used, the poorer the drop strength and the lower the bursting temperature, especially for the S03 sample, the drop strength is already lower than 3 times/(0.5 m.P), which is much lower than that of green pellets using quicklime as flux. This indicates that the pelletizing material using limestone as flux has poor pelletizing performance. The falling strength is greatly related to the type of the flux in addition to the amount of bentonite used. The slaked quicklime has certain cohesiveness which is not possessed by limestone.

The compressive strength of the three types of green pellets reaches more than 10N/P, and the requirements of operations such as transportation, screening and the like can be met. The green pellets of type S03 had a relatively good compressive strength due to their extended compaction time as compared to the other two samples. The bursting temperature is essentially positive with respect to the bentonite content.

According to green ball performance, the production process parameters of the alkaline pellets taking limestone as a fusing agent can only select parameters corresponding to the S01 type.

TABLE 3 green ball Performance

Physical property detection result and analysis of finished alkaline pellet

The cold compression strength and powder content of the pellets are shown in Table 4.

TABLE 4 pellet physical Properties

As can be seen from tables 3 and 4, in the three roasting systems, only the compressive strength index of the pellet ore under the 3 rd system can meet the requirement, and the compressive strengths under the 1 st system and the 2 nd system are both lower than 1950N/P; the powder content of the pellet under the three systems can meet the production requirement, and is lower than 2.0 percent, but the powder content under the 2 nd system is the worst. The dosage of the bentonite has certain influence on the compressive strength of the pellet. When the consumption of the bentonite is 1.5 percent, the compression strength of the pellet ore is the maximum, and especially the S033 sample reaches more than 2500N/P.

The alkaline green ball using limestone as flux needs to meet the requirement of heat consumption of calcium carbonate decomposition during roasting. The preheating temperature and the roasting temperature of the 3 rd system are the highest, namely 970 ℃ and 1260 ℃, so that the solid-phase reaction among the vanadium-titanium magnetite particles and the oxidation and consolidation of the roasted balls can be fully realized, and the compressive strength of the roasted balls can be improved. However, it should be noted that the extent of the increase in the firing temperature is limited to the extent that pyrolysis of Fe2O3 does not occur and the cohesion between pellets does not occur.

According to the compressive strength of the finished pellets, the parameters corresponding to S013 and S011 can be selected according to the production process parameters of the alkaline pellets taking limestone as a fusing agent; the compression strength of the finished ball is required to be more than or equal to 1950N/P, and the production process parameters can only be selected from the parameters corresponding to S013.

Finished product alkaline pellet metallurgical performance detection result and analysis

The results of the measurements of the low-temperature reduction degradation property, the reduction property and the reduction expansion property of the pellets are shown in tables 5 to 7. As can be seen from Table 5, the RDI +3.15 of the pellets under the 3 rd system is preferably higher than 98%, and the RDI +3.15 is reduced with the reduction of the bentonite dosage; secondly, the 1 st system is adopted, and all the systems are higher than 88%; the index of the 2 nd system is the worst, and 2 are less than 80 percent.

The RDI +3.15 height of the finished pellet ore is determined, and the parameters corresponding to the S013 are selected again according to the production process parameters of the alkaline pellet with limestone as the flux.

TABLE 5 pellet Low temperature reduction degradation Performance test results

TABLE 6 pellet reduction Performance test results

As is clear from Table 6, RI of the pellets was 60% or more except that RI of S012 was 46.5%. After limestone is added, decomposition occurs in the roasting process to generate CaO and CO2, and CO2 escapes to form a micro-pore effect, which is beneficial to improving the reduction condition of the pellet ore; in addition, the combination of partial CaO and SiO2 or the combination of partial CaO and Fe2O3 inhibits the generation of the mineral fayalite (2 FeO. SiO2) which is difficult to reduce, thereby improving the reduction performance of the pellet.

The RI of the pellet under the 1 st roasting system is relatively good and is higher than 75%, although the roasting temperature of the 3 rd system is higher, the RI is slightly lower (lower than 70%), which is probably caused by that the roasting temperature is higher, the porosity inside the pellet is reduced, and the reduction reaction is not favorably carried out. Such burden not only increases the fuel consumption of the blast furnace smelting process, but also affects the gas permeability of the material column.

TABLE 7 pellet reduction and expansion Properties test results

As can be seen from Table 7, the free expansion index of the pellets almost increased with the decrease of the bentonite dosage (except for S033), and the free expansion index was far lower than 20% regardless of the calcination system and the bentonite dosage, which completely satisfied the production requirements.

Detection result and analysis of chemical components of finished alkaline pellet

The results of chemical component detection of the finished pellets are shown in Table 8.

The finished pellet ore basically has the alkalinity of 0.8 +/-minus or plus, the TFe content of 52.4-53.3 percent, the MgO content of 2.4-2.5 percent, the TiO2 content of 9.8-10.1 percent, the P content of less than 0.024 percent and the As content of less than 0.006 percent.

TABLE 8 pellet chemical composition (% alkalinity excluded)

As can be seen from fig. 1, the S content of the 1 st system is less than 0.010% except that S021 is 0.014% (slightly more than 0.010%) for the other two pellet samples; the desulfurization effect is the worst under the 2 nd system, the S content of the pellet is as low as 0.010 percent as high as 0.021 percent; under the 3 rd system, the S content of the pellets is totally less than 0.01 percent and maximally 0.005 percent. It is shown that the higher the preheating temperature, especially the roasting temperature, the better the desulfurization effect.

As can be seen from FIG. 2, the FeO content of the pellets under the three systems is lower than 1.5%, and the FeO content of the pellets under the 1 st system is 0.46% as the lowest; the FeO content of the pellets under the system 2 is slightly higher than that of the pellets under the system 1, and is 0.58 percent. The FeO content of the system 3 is relatively high and is between 0.58 and 0.99 percent. This may be related to insufficient magnetite oxidation inside the pellet as the outer layer of the pellet, Fe2O3, recrystallizes and becomes dense after the firing temperature is increased. However, no matter which roasting system is adopted, the FeO content in the pellets is all lower than 1.0 percent, and the production requirements are completely met.

Summary of alkaline pellet experiments using limestone as flux

The basic pellet experiment with limestone as flux has been carried out to prepare material, pelletizing, green pellet performance detection, green pellet roasting and other operations, and the compression strength, powder content, low temperature reduction degradation performance, reduction performance and reduction expansion performance of the finished pellet are detected and analyzed, and the following conclusion is obtained:

(1) under the conditions of alkalinity of 0.8 and the dosage of three types of bentonite, the falling strength of green pellets is lower, the highest falling strength is 4.9 times/(0.5 m.P), the compressive strength can reach more than 10N/P, and the bursting temperature is more than 500 ℃;

(2) in the same roasting system, when the consumption of the bentonite is 1.5 percent, the compressive strength of the finished pellet ore is the maximum; the compression strength of the pellet under the 3 rd system is the highest and is higher than 1950N/P; the powder content of the pellet ore under the three roasting systems is relatively low and is lower than 2.0 percent;

(3) the order of the pellet RDI +3.15 is as follows: system 3 > > system 1 > system 2; under the 3 rd roasting system, RDI +3.15 is reduced along with the reduction of the dosage of the bentonite;

(4) the RI of the pellet ore under the 1 st system is slightly higher than that of the pellet ore under the 3 rd system; the relationship between the amount of RI and the amount of bentonite is not large, but the influence of a roasting system on the RI and the amount of bentonite is large;

(5) the free expansion indexes of the pellet ore under different bentonite dosage and three roasting systems are all lower than 15 percent, and the production requirements are completely met;

(6) the alkalinity is 0.8, the consumption of bentonite is 2 percent, and the 3 rd roasting system is the production process parameter of the alkaline pellets (namely corresponding to S013) taking limestone as the flux.

The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.

Claims

1. A limestone alkaline pellet, comprising: iron ore concentrate, dedusting ash, bentonite and flux; wherein the iron concentrate comprises python concentrate, conyon concentrate, hening concentrate, taihe concentrate; python concentrate in iron concentrate: kangmao concentrate: and (4) Anning concentrate: taihe concentrate is 1-4: 1-6:1-4: 1-7; the proportion of the dedusting ash is 1-3% of the total mass; the proportion of the bentonite is 1 to 4 percent of the total mass; the fusing agent is limestone; the alkalinity of the limestone alkaline pellets is 0.5-1.0.

2. The limestone alkaline pellet as claimed in claim 1, wherein the fly ash is formulated to be 1.8% of the total mass.

3. The limestone alkaline pellet as claimed in claim 1, wherein the proportion of bentonite is 1.5-2.0% of the total mass.

4. A process for preparing the limestone alkaline pellets as claimed in claim 1, which comprises the following steps:

s1 preparing limestone alkaline pellet ingredients;

s3, drying the green pellets;

s4, preheating and roasting the green pellets;

s5, soaking and cooling the baked green pellets to obtain finished products.

5. The process for preparing limestone alkaline pellets as claimed in claim 4, wherein the drying temperature in the step S3 is 200-500 ℃.

6. The process for preparing limestone alkaline pellets as claimed in claim 4, wherein the temperature of preheating in the step S4 is 900-1000 ℃.

7. The process for preparing limestone alkaline pellets as claimed in claim 4, wherein the roasting temperature in the step S4 is 1200-1300 ℃.

8. The process for preparing the alkaline pellets of limestone as claimed in claim 4, wherein the soaking temperature in the step S5 is 1100-1200 ℃.

9. The process for preparing limestone alkaline pellets as claimed in claim 4, wherein the cooling time in the step S5 is 40-60 minutes.

10. The process for preparing limestone alkaline pellets as claimed in claim 4, wherein the cooling time in the step S5 is the cooling time between the furnace and the outside of the furnace.