CN115259699B

CN115259699B - Production process for preventing lime nodulation and increasing lime activity

Info

Publication number: CN115259699B
Application number: CN202210734748.9A
Authority: CN
Inventors: 胡原德; 黄巧辉; 赖绍振; 邓丽榕; 何日凤
Original assignee: Shaoguan Minghao New Building Materials Co ltd
Current assignee: Shaoguan Minghao New Building Materials Co ltd
Priority date: 2022-06-27
Filing date: 2022-06-27
Publication date: 2023-05-16
Anticipated expiration: 2042-06-27
Also published as: CN115259699A

Abstract

The invention discloses a production process for preventing lime nodulation and increasing lime activity, which comprises the following steps: step 1), crushing: crushing the massive limestone into crushed limestone with the particle size of 60-80 mm; step 2), preheating: putting crushed limestone into a preheating zone, wherein the temperature of the preheating zone is controlled to be 900-1000 ℃ and the preheating time is 20-50min to obtain a mixture of limestone and quicklime; step 3), calcining: the preheated mixture enters a calcining zone, the temperature of the calcining zone is controlled to be between 1100 and 1200 ℃, the calcining time is 3 to 5 hours, and meanwhile sodium nitrite is sprayed to the preheating zone to obtain a quicklime crude product; step 4), cooling: putting the quicklime crude product into a cooling zone, wherein the temperature of the cooling zone is controlled below 100 ℃; and 5) collecting materials. On the one hand, the lime kiln is not easy to agglomerate, and on the other hand, the quicklime with high activity can be obtained.

Description

Production process for preventing lime nodulation and increasing lime activity

Technical Field

The invention relates to the field of lime processing, in particular to a production process for preventing lime nodulation and increasing lime activity.

Background

Lime is generated by lime rotary kiln nodulation limestone, which is a simple chemical reaction, and excessive heat input causes excessive temperature or excessive reaction time, so that excessive burning can occur. Lime adheres to each other or to surrounding materials in normal state or to kiln walls to form knots.

When the kiln temperature is too high, local temperature is too high to cause adhesion after frequent or large-scale adjustment, but the kiln is easy to break by beating and other modes. In the process of discharging ash from the kiln bottom, the conditions of individual burning and adhesion are observed. The activity of the product is reduced, the permeability of the kiln body is affected, and the method is a cause of nodulation. If the slight adhesion is not found in time, the adhesion knots can develop into large-area adhesion knots, the adhesion knots are blocked at the bottom of the kiln and can not be discharged, and high temperature is generated in a discharging area, so that a discharging platform and a hydraulic cylinder are damaged. The temperature of the discharging platform rises sharply, the material level of the kiln inclines, and the action frequency of the discharging platform is obviously increased. The discharging platform, the blast cap and the hydraulic equipment are damaged, the quality and the yield of lime are seriously affected, the treatment is time-consuming and labor-consuming, the treatment time is more than 10 hours, and the treatment time is 10-15 days.

When the internal temperature of the silicon dioxide reaches 700-800 ℃, the silicon dioxide is in a solid state and reacts with the calcium oxide to gradually generate dicalcium silicate and silicon dioxide, and because a large amount of calcium oxide still exists in the limestone, the larger reaction can occur until the metal oxide SiO is generated ₂ Will slowly stop, the silica affects the speed of the reaction, the more evenly it is distributed over the limestone, the more counterThe faster the reaction speed will be, and if not evenly distributed, the reaction speed will be decreased. When the internal temperature of the ferric oxide reaches 800-900 ℃, chemical reaction is generated with calcium oxide, so that calcium oxide, ferric oxide and two calcium oxide molecules, ferric oxide are sequentially generated, the substances can form uniform solution substances, and the substances can be slowly combined in a lime kiln to slowly generate blocks, so that kiln tumors are derived.

At present, aiming at the problem of lime nodulation, the adopted means are generally to clean in time to avoid the generation of large lime nodulation, but the cause and the symptoms are treated all the time, and further improvement is needed for improving the calcination efficiency and quality of the limestone.

Disclosure of Invention

In order to reduce the occurrence of the caking problem of the lime kiln and improve the activity of quick lime, the application provides a production process for preventing lime caking and improving the activity of lime.

The production process for preventing lime nodulation and increasing lime activity comprises calcining in a vertical lime kiln, wherein the vertical lime kiln comprises a preheating zone positioned at the upper part of the lime kiln, a combustion zone positioned at the middle part of the lime kiln and a cooling zone positioned at the middle lower part of the lime kiln, and specifically comprises the following steps:

step 1), crushing: crushing the massive limestone into crushed stone with the particle size of 60-80 mm.

Step 2), preheating: and (3) putting the crushed limestone into a preheating zone, wherein the temperature of the preheating zone is controlled to be 900-1000 ℃, and the preheating time is 20-50min to obtain a mixture of limestone and quicklime.

Step 3), calcining: the preheated mixture enters a calcining zone, the temperature of the calcining zone is controlled between 1100 ℃ and 1200 ℃ for 3 to 5 hours, and sodium nitrite is sprayed to the preheating zone at the same time, so that a quicklime crude product is obtained.

Step 4), cooling: and (3) putting the quicklime crude product into a cooling area, wherein the temperature of the cooling area is controlled below 100 ℃.

And 5) collecting materials.

Preferably, the sodium nitrite is used in an amount of 0.5 to 2% of the mixture in step (2).

The calcining temperature is not controlled well in operation, and the nodulation is easy to form. Because the higher the calcining temperature is, the substances with low melting points in the materials in the kiln are easier to melt into liquid phase, so that lime is mutually bonded into blocks or is bonded on the kiln wall to gradually form wall-hanging kiln nodules, and the higher the temperature is, the more easily the various components in the materials react or are chemically reacted with the kiln lining to generate more substances with low melting points, thereby promoting the formation of kiln nodules. Therefore, the calcination temperature should be reasonably controlled according to the content of impurities in the calcination. Compared with the conventional process, the method has the advantages that the particle size of the limestone is controlled to be larger, the cost of raw material crushing is reduced, the calcination temperature of the limestone with the large particle size is higher, but the problem of sandwich is easy to generate due to the high calcination temperature, namely the condition that the outside of the limestone is burnt well and then the inside of the limestone is not completely calcined. Therefore, the addition of sodium nitrite can fully burn limestone, reduce the problem of sandwich, and promote the growth of crystals in calcined quicklime. Since the crystals are not fused and connected and are rich in air holes, the overburning can be prevented, the hydration speed of the biscuit firing lime which is fired at low temperature to obtain porous lime is high, and the porous lime is rich in air holes even when being fired at high temperature during salt firing, so that the salt firing is suitable for a wide firing temperature range, and the limestone is easier to be fired uniformly.

The lime comprises free calcium oxide and combined calcium oxide, and the free calcium oxide comprises active calcium oxide and inactive calcium oxide. Under ordinary digestion conditions, the inactive calcium oxide cannot react with water, but may be converted into active calcium oxide (e.g., after grinding). The active calcium oxide is the part of free calcium oxide which can react with water under the ordinary digestion condition, and the combined calcium oxide is not recoverable, so the active calcium oxide cannot be called as inactive calcium oxide. The reactivity of lime can be seen as, in fact, the amount of active calcium oxide in the total amount of free calcium oxide. Calcination of limestone is a process of changing the diamond lattice of limestone from recrystallisation to cubic lattice of lime. The crystal structure obtained by its change is related to the rate of formation of new phase nuclei and its growth rate. When the former is larger than the latter, fine-grained crystals are obtained, the number of active calcium oxide molecules is large, and the surface energy is high; on the contrary, the obtained coarse-grain crystals with low surface energy have small molecular number of active calcium oxide. Under the condition of quick heating and calcining of limestone, the obtained lime with a fine grain crystal structure has high activity; when the lime is calcined by slow heating, the activity of the lime obtained is low. By adopting the technical means, the lime stone calcining time is reduced, and the activity of the quicklime is improved.

Preferably, the limestone is selected from SiO ₂ 、Fe ₂ O ₃ 、Al ₂ O ₃ And MgCO ₃ A content of less than 0.08%.

The impurity in the limestone raw material can also cause caking of the lime kiln. The higher the impurity content of the limestone raw material entering the kiln, the more easily the material participates in the reaction in the kiln, and is melted or stuck on the kiln wall, and the formation of kiln nodules is easily caused. The more easily these impurities react with CaO in a series to form various low melting point compounds, which cause the lime to adhere to each other and form lumps.

Preferably, the particle size of the limestone is 60-70mm.

The size of the limestone greatly affects the firing rate of lime, and the too large size can prolong the material residence time and affect the capability of the lime kiln, and conversely, the too small size of the limestone has short residence time in the kiln. However, there is also a need for a reduced limestone particle size which increases the drag in the kiln. The gas distribution is worsened, the calcination working condition of the lime kiln is destroyed, partial calcination and local high temperature are formed or 'nub' is generated, the fuel consumption is increased, and the production capacity of the lime kiln and the kiln gas CO are reduced ₂ Concentration. Therefore, the limestone granularity should be uniform and the calcination can be stable, which is beneficial to the stable operation of the lime kiln and the improvement of the decomposition rate. By further controlling the particle size of the limestone, the limestone can be combusted more fully and is not easy to burn excessively.

Preferably, the temperature of the cooling zone is 20-50 ℃.

Preferably, a shell is added together with the limestone, the shell being 1-3% by weight of the limestone.

Preferably, the shell weight is 1.3-2.1% of limestone.

The scheme aims at reducing the 'sandwich' of the limestone, but the hardness of the quicklime is increased due to the use of sodium nitrite, and the quicklime is easy to crack when being smeared on a wall after being reacted with water, so that the quality of the lime is affected. The hardness of lime is reduced by calcining the shells and the limestone, and the addition amount of the shells is controlled, so that the lime activity is not easily affected.

Preferably, the fuel of the lime kiln is anthracite and coke, and the usage amount of the anthracite is 5-8% higher than that of the coke.

Among fuels used in limestone calcination, fuels with high ash content have a reduced firing value and correspondingly lower lime quality. High volatile content, causing long flame and increased calcination area, requires high fuel holding carbon. The burning speed of the coke is faster than that of the anthracite, and under the same condition, the large layer of the limestone is concentrated by using the coke to calcine; in contrast, anthracite has low burning speed and low burning point, and is easy to form and elongate in calcining area, so that kiln gas temperature and ash discharge temperature are high. Because the volatile components in the anthracite are large, the anthracite is used for calcining the limestone, so that the two ends of the limestone are high easily. The volatile component volatilizes at a lower temperature, namely in a preheating zone, resulting in a high kiln temperature. Anthracite coal burns slowly, resulting in high ash content and heat loss. The fuel proportioning amount is key to influencing the calcination and decomposition of limestone. The mixture ratio is low, the temperature can not meet the requirement, the calcination is insufficient, and the lime belt is seriously burned; conversely, excessive proportions are liable to cause nodulation. Therefore, in the practical production of the limestone with large particle size, the anthracite and the coke are properly proportioned, so that the limestone is not easy to agglomerate in the lime kiln, and the limestone can be calcined more fully.

In summary, the particle size of the limestone is controlled to be larger than that of the limestone prepared by the conventional process, and sodium nitrite is added to fully burn the limestone and reduce the problem of sandwich, so that the growth of crystals in calcined quicklime can be promoted. Since the crystals are not fused and connected and are rich in air holes, the overburning can be prevented, the hydration speed of the biscuit firing lime which is fired at low temperature to obtain porous lime is high, and the porous lime is rich in air holes even when being fired at high temperature during salt firing, so that the salt firing is suitable for a wide firing temperature range, and the limestone is easier to be fired uniformly.

Adding sodium nitrite in order to reduce the problem of "sandwich" of lime stone, but so the hardness of lime will increase, with water reaction quick lime after scribble on the wall easy fracture, this application calcines through shell and lime stone together for the hardness of quick lime can reduce, and the addition of control shell makes it be difficult for producing the influence to the activity of lime simultaneously.

Detailed Description

Examples

The production process for preventing lime from caking and increasing lime activity comprises calcining in a vertical lime kiln, wherein the vertical lime kiln comprises a preheating zone positioned at the upper part of the lime kiln, a combustion zone positioned at the middle part of the lime kiln and a cooling zone positioned at the middle lower part of the lime kiln, an ash discharging rotary table is arranged below the cooling zone, an ash discharging machine is connected with the ash discharging rotary table, calcined lime is discharged from the ash discharging rotary table to the ash discharging machine, and the ash is discharged from the ash discharging machine every 300 seconds, and is further discharged through a climbing machine. The blower blows air from the bottom of the lime kiln, the pressure of the air chamber is 4.5Kpa, and the blowing frequency is 25Hz.

Limestone selection of SiO ₂ 、Fe ₂ O ₃ 、Al ₂ O ₃ And MgCO ₃ Raw stone with a content of less than 0.08%.

Example 1

The fuel used in the lime kiln is 78Kg of anthracite and coke, and the using amount of the anthracite is 5% higher than that of the coke, namely 40Kg of anthracite and 38Kg of coke.

The embodiment discloses a production process for preventing lime nodulation and increasing lime activity, which comprises the following steps:

step 1), crushing: 1000Kg of large limestone is crushed into crushed limestone with particle size of 60-80mm by a crusher.

Step 2), preheating: the crushed limestone enters a preheating zone, the temperature of the preheating zone is controlled at 900 ℃, and the preheating time is 50min, so that a mixture of limestone and quicklime is obtained.

Step 3), calcining: the preheated mixture enters a calcining zone, the temperature of the calcining zone is controlled to be between 1100 ℃ and the calcining time is 5 hours, and meanwhile 5Kg of sodium nitrite is sprayed to the preheating zone to obtain a quicklime crude product.

Step 4), cooling: the quicklime crude product enters a cooling zone, and the temperature of the cooling zone is controlled at 60 ℃. Cooling for 20min.

And 5) collecting materials.

Example 2

The fuel used in the lime kiln is 78Kg of anthracite and coke, and the using amount of the anthracite is 8 percent higher than that of the coke, namely 40.5Kg of anthracite and 37.5Kg of coke.

step 1), crushing: 1000Kg of large limestone is crushed into crushed limestone with the particle size of 60-80mm by a crusher.

Step 2), preheating: the crushed limestone enters a preheating zone, the temperature of the preheating zone is controlled at 1000 ℃, and the preheating time is 30min, so that a mixture of limestone and quicklime is obtained.

Step 3), calcining: the preheated mixture enters a calcining zone, the temperature of the calcining zone is controlled to be between 1200 ℃ and the calcining time is 3 hours, and meanwhile 5Kg of sodium nitrite is sprayed to the preheating zone to obtain a quicklime crude product.

Step 4), cooling: the quicklime crude product enters a cooling zone, and the temperature of the cooling zone is controlled at 30 ℃. Cooling for 20min.

And 5) collecting materials.

Example 3

The difference from example 2 is that: the particle size of the limestone is 60-70mm.

Example 4

The difference from example 3 is that: also added with the limestone is a shell, the weight of which is 1% of that of the limestone, i.e. 10Kg.

Example 5

The difference from example 3 is that: also added with the limestone is a shell, the weight of which is 1.3% of that of the limestone, i.e. 13Kg.

Example 6

The difference from example 3 is that: also added with the limestone is a shell, the weight of which is 2.1% of that of the limestone, i.e. 21Kg.

Example 7

The difference from example 3 is that: also added with the limestone is a shell, the weight of which is 3% of that of the limestone, i.e. 30Kg.

Comparative example

Comparative example 1

The difference from example 2 is that sodium nitrite is replaced by equal mass of sodium chloride.

Testing

1. Observing the nodulation condition of the lime kiln after sintering for one week, cleaning when the nodulation is encountered, and counting the cleaning time.

2. Activity test of quicklime: YB/T105-2014, metallurgical lime physical test methods, results were measured on a 4N HCl-depleted volume basis and are reported in Table 1. 350ml 250

3. Testing cracking degree after quicklime digestion: examples and comparative examples calcined quicklime 5000g, flour 135g and caustic soda 30g. Firstly, quicklime is dissolved in water to become white slurry. Dissolving caustic soda in a container, adding water into flour, mixing into porridge-like paste, slowly pouring caustic soda solution into the paste, stirring at any time, mixing, and pouring into lime white slurry to obtain lime slurry for wall brushing. The total length of the crack was measured in cm after a lime slurry was spread evenly on a flat cement board (1 m 1) with a thickness of 20mm and left to stand for 72h and recorded in table 1.

Project	Cleaning time/h	Activity/ml	Cracking degree/cm
				Example 1	4	367	4.7
Example 2	4	369	5.4
				Example 3	4	376	4.9
Example 4	4	374	0
				Example 5	4	374	0
Example 6	4	376	0
				Example 7	4	376	0
Comparative example 1	5	344	2.6

As can be seen from Table 1, examples 1-7 have less nodulation cleaning time than comparative example 1 and have greater activity than comparative example 1, indicating that the calcination process of the present application has higher activity than the quicklime obtained in the prior art, less nodulation damage to the lime kiln, and greatly reduced nodulation cleaning time.

According to examples 4-7, compared with examples 1-3, there is no cracking, which shows that sodium nitrite is added to reduce the problem of "sandwich" of limestone, but then the hardness of lime is increased, and the lime is easy to crack when being smeared on a wall after being used for reacting quicklime with water.

The above-described embodiments are only preferred embodiments of the present invention, and are intended to illustrate the present invention and not to limit the scope of the present invention. The invention has been described with reference to specific embodiments. Those skilled in the art can appropriately change the links of the raw materials, the process conditions and the like to achieve the corresponding other objects by referring to the content of the present invention, and all the similar substitutions and modifications are obvious to those skilled in the art without departing from the content of the present invention, and are considered to be included in the scope of the present invention.

Claims

1. The production process for preventing lime nodulation and increasing lime activity is characterized by using a vertical lime kiln for calcination, wherein the vertical lime kiln comprises a preheating zone positioned at the upper part of the lime kiln, a combustion zone positioned at the middle part of the lime kiln and a cooling zone positioned at the middle lower part of the lime kiln, and the production process is characterized by comprising the following steps of:

step 1), crushing: crushing the massive limestone into crushed limestone with the particle size of 60-70 mm;

step 2), preheating: putting crushed limestone into a preheating zone, wherein the temperature of the preheating zone is controlled to be 900-1000 ℃ and the preheating time is 20-50min to obtain a mixture of limestone and quicklime;

step 3), calcining: the preheated mixture enters a calcining zone, the temperature of the calcining zone is controlled to be between 1100 and 1200 ℃, the calcining time is 3 to 5 hours, and meanwhile sodium nitrite is sprayed to the preheating zone to obtain a quicklime crude product;

step 4), cooling: putting the quicklime crude product into a cooling zone, wherein the temperature of the cooling zone is controlled below 100 ℃;

step 5), material collection;

the dosage of the sodium nitrite is 0.5-2% of the mixture in the step 2), and the limestone selects SiO ₂ 、Fe ₂ O ₃ 、Al ₂ O ₃ And MgCO ₃ A raw material content of less than 0.08%; also added with the limestone is a shell, the weight of the shell is 1-3% of that of the limestone;

the fuel of the lime kiln is anthracite and coke, and the using amount of the anthracite is 5-8% higher than that of the coke.

2. The production process for preventing lime nodulation and increasing lime activity according to claim 1, wherein: the temperature of the cooling zone is 20-50 ℃.

3. The production process for preventing lime nodulation and increasing lime activity according to claim 1, wherein: the weight of the shell is 1.3-2.1% of that of the limestone.