KR102155173B1 - Method for producing quicklime using oyster shell powder and lime sludge - Google Patents

Abstract

The present invention relates to a method for manufacturing quicklime which comprises the following steps: mixing an oyster shell powder, a limestone sludge, and dust to manufacture a blended raw material; and charging the blended raw material to a sintering furnace and performing a sintering process, so that the hydration rate of the blended raw material is 90% or more and 100% or less, and the differentiation rate of the blended raw material is 14 to 16%. The present invention has the advantage of stably supplying quicklime with stable quality and high quality.

Description

Method for producing quicklime using oyster shell powder and limestone sludge{Method for producing quicklime using oyster shell powder and lime sludge}

The present invention relates to a method for producing quicklime by simultaneously using waste shell powder as a marine by-product and limestone sludge and dust as an iron-making by-product,

Oyster shell powder, which is a lung shell powder; Including the steps of preparing a blended raw material by mixing limestone sludge and dust, and charging the blended raw material into a sintering furnace and performing a firing process, the hydration rate of the blended raw material is 90% or more and 100% or less, It relates to a method for producing quicklime to be prepared so that the conversion rate is 14 to 16%.

Limestone is used as an important auxiliary material after iron ore and coal in the steelmaking process, and quicklime obtained by calcining limestone in the steelmaking process is mainly used in the refining process.

In the ironmaking process, limestone plays a role in slag formation and refining, and in the steelmaking process, quicklime plays an important role as an auxiliary material to control the basicity of slag.

On the other hand, limestone sludge and dust generated in a conventional limestone sintering furnace of a steel mill, and limestone sludge generated together with sewage when washing with limestone ore has no proper use.

Although it is used in small amounts for cement raw materials or raw materials for light calcium carbonate production, most are buried and disposed of.

Even when used as a subsidiary material for cement, there is a concern that the strength may decrease due to impurities contained in the sludge. In the case of mixing with cement in this way, there is a problem that it is dissociated and scattered into the air and the problem of air pollution occurs.

In addition, when sludge is used as medium and light calcium carbonate, the use of the sludge is limited because it causes a problem of lowering the purity due to the incorporation of a large amount of impurities.

The method of manufacturing and reusing light carbonate by a chemical treatment method is also not practical because the cost required for treatment is enormous due to an increase in treatment process and an excessive amount of impurities.

In general, a large amount of oyster shells produced and disposed of in South Korea's southern coasts are recycled in some very small quantities, and most of them are dumped in the ocean or buried on land, which causes the problem of environmental pollution by contaminating the surrounding water. have.

There is a difficulty in the treatment of oyster shells, a by-product generated in the process of producing oysters. As a result, the shell of oysters reaches hundreds of thousands of tons per year, but the use of waste materials is extremely poor.

Hundreds of thousands of tons of oyster shells are turned into waste, causing various environmental pollution and devastation. Oyster shells are loaded and neglected in each place, giving off a bad smell, and providing a place for flies and mosquitoes to inhabit, which has an adverse effect on hygiene.

Although the oyster shells are dried and pulverized to produce powdered fertilizer as a method of utilizing oyster shells, the fertilizer contains salt as well as the loss of fertilizer due to scattering of fertilizers or rainwater on farmland. Etc.

In addition, even if it is molded into a granular shape in consideration of the above scattering and loss problems, the granular oyster shell made of only oyster shells does not have good decomposition efficiency, so the effect of plant growth or land improvement is greatly reduced. I can't.

In relation to the present invention, in the'manufacturing method of coniferous lime using limestone sludge', registered patent 10-0128125 (registration date October 29, 1997), the limestone sludge generated in the manufacturing process of quicklime is mass-treated by a conventional method. After drying, and then firing at a temperature of 850 to 1050 °C for 40 to 80 minutes, a technique for a method for producing conidia using limestone sludge has been disclosed.

Patent Publication 2002-0044434 (Publication date: June 15, 2002) In the'manufacturing method of quicklime using limestone sludge mixed with coal ash', in the method of calcining limestone sludge into quicklime by indirect heating method, the limestone sludge is Disclosed is a technology for a method for producing quicklime using limestone sludge mixed with carbonaceous material, characterized in that it consists of mixing powdery or bulky carbonaceous material to be agglomerated by a conventional method and supplying separate oxygen to the limestone sludge. There is a bar.

Registered Patent 10-1256807 (Registration Date April 16, 2013)'Quicklime molded body using limestone powder with low utilization and its manufacturing method and hard calcium carbonate' include limestone and dust generated in limestone processing or limestone plastic processing. , 95~99wt% of limestone powder obtained by pulverizing limestone of 20㎜ or less generated during particle size classification after mining of sludge or mine, and calcium chloride (CaCl ₂ ) and magnesium chloride (MgCl ₂ ㆍ6H ₂ O) which are _divalent metal chlorides A technique for a quicklime molded body using limestone having low utilization, characterized in that it contains 1 to 5 wt% of one or more, has been disclosed.

Although the above disclosed patents and registered patents disclose a technology using limestone sludge or limestone powder as a quicklime manufacturing technology, a technology for manufacturing quicklime with stable quality and high quality by using it simultaneously with oyster shell powder, which is marine waste, is disclosed. There is no bar. Therefore, it is difficult to easily derive an effect to be presented through the present invention from the technologies disclosed in the above-described published patents and registered patents.

Registered patent 10-0128125 (Registration date October 29, 1997) Patent Publication 2002-0044434 (Publication date June 15, 2002) Registered Patent 10-1256807 (Registration date April 16, 2013)

An object of the present invention is to provide a method for producing quicklime with stable quality and high quality by mixing and sintering oyster shell powder generated as marine by-products and limestone sludge and dust generated as iron-making by-products.

To achieve the above object,

The present invention is oyster shell powder; Preparing a blended raw material by mixing limestone sludge and dust;

Including the step of charging the blended raw material into a firing furnace and performing a firing process,

It provides a method for producing quicklime using oyster shell powder and limestone sludge, for preparing quicklime so that the hydration rate of the blended raw material is 90% or more and 100% or less, and the differentiation rate is 14 to 16%.

Also,

Preparing oyster shell powder having a grain size of 7 mm to 70 mm, limestone sludge and dust having a grain size of more than 0 and less than 14 mm, and

The oyster shell powder; Preparing a blended raw material by mixing limestone sludge and dust;

Including the step of charging the blended raw material into a firing furnace and performing a firing process,

It provides a method for producing quicklime using oyster shell powder and limestone sludge, for preparing quicklime so that the hydration rate of the blended raw material is 90% or more and 100% or less, and the differentiation rate is 14 to 16%.

Oyster shell powder according to the present invention; The quicklime manufacturing method using limestone sludge and dust has the advantage of being able to manufacture quicklime, a subsidiary raw material of the ironmaking process, by simultaneously treating marine by-products of oyster shells and iron-making by-products of limestone sludge. It has the advantage of stably supplying quicklime with stable quality and high quality.

1 is an oyster shell powder of the present invention; Process flow chart according to the quicklime manufacturing method using limestone sludge and dust.
2 is an oyster shell powder of the present invention; A graph showing the differentiation rate and hydration rate according to the mixing ratio of limestone sludge and dust.

Hereinafter, the oyster shell powder of the present invention; The technical composition of the quicklime manufacturing method using limestone sludge and dust will be examined in more detail.

As shown in Figure 1,

Quicklime manufacturing method according to the present invention

Oyster shell powder of soft limestone; Preparing a blended raw material by mixing hard limestone limestone sludge and dust;

Including the step of charging the blended raw material into a firing furnace and performing a firing process,

Quicklime is prepared so that the hydration rate of the blended raw material is 90% or more and 100% or less, and the differentiation rate is 14 to 16%.

In addition, as a step before the step of preparing the blended raw material,

Oyster shell powder with a grain size of 7 mm or more and 70 mm or less,

It may further include preparing limestone sludge and dust having a grain size of more than 0 and less than 14 mm.

According to the manufacturing method of quicklime presented in the present invention, oyster shell powder; After preparing a blended raw material by mixing limestone sludge and dust, the prepared blended raw material is charged into a sintering furnace and a sintering process is performed.At this time, the hydration rate of the blended raw material is 90% or more and 100% or less. And the differentiation rate satisfies 14 to 16%.

The hydration rate indicates the degree of sintering of the quicklime constituting the compounding material.

If the hydration rate of the blended raw material is less than 90%, the desulfurization rate is lowered when the quicklime produced through the firing process is applied to the desulfurization reaction.

The differentiation rate indicates the degree of differentiation of the raw material, that is, quicklime.

The lower the differentiation rate is, the more effective it is to improve productivity.

However, if the differentiation rate is less than 14%, the hydration rate is relatively low, and it is difficult to satisfy the hydration rate of 90% or more and 100% or less.

If the differentiation rate exceeds 16%, productivity is lowered, and the air permeability in the kiln is deteriorated due to the differentiation phenomenon, so uniform firing is not achieved, and a load is generated on the kiln.

The hydration rate and differentiation rate are measures of quicklime quality.

At this time, oyster shell powder 10.0 to 40.0 wt% and limestone sludge and dust are mixed within the range of 60.0 to 90.0 wt% so that the hydration rate of the blended material is 90% or more and 100% or less and the differentiation rate is 14 to 16%.

Since quicklime for iron making should have high quality of CaO, limestone, which is a raw stone, has as high as possible CaO, and a fine grain size should be selected to suppress differentiation during firing, and should not be overfired.

In particular, since the quality of calcining limestone greatly affects the quality of quicklime, and quicklime influences the quality of steel, the quality of calcining limestone and manufactured quicklime must be strictly managed according to the purpose.

Therefore, if the types of limestone are different, each storage room is separately managed, and the firing conditions are also different for operation. However, in this case, there is a restriction on the use of the yard, so it is necessary to secure a site, and if limestone is changed due to the difference in firing conditions during operation according to each limestone inventory, the quality of the manufactured quicklime will deteriorate for at least 3 days, and steelmaking It becomes difficult to use in the firing process of or iron making.

In order to manage this, soft limestone oyster shell powder 10.0 ~ 40.0 wt%; Prepare a blended raw material by mixing the hard limestone limestone sludge and dust at a blending ratio of 60.0 ~ 90.0 wt%;

The oyster shell powder, limestone sludge, and dust are classified according to the grain size.

The oyster shell powder is washed by collecting discarded oyster shells, and after removing organic matter and coating sand attached to the oyster shell,

After drying for 20 to 30 hours in a drying furnace at 100 to 500 °C, pulverized so that the crystal grain size is not less than 7 mm and not more than 70 mm is used.

The oyster shell powder is a limestone having a grain size of 7 mm to 70 mm, and the limestone sludge and dust are limestone having a grain size of more than 0 and less than 14 mm.

Among the limestones, limestone having a crystal grain size of more than 0 and less than 70 ㎜ is used for iron making, and it is again used as oyster shell powder; It is classified into limestone sludge and dust. The grain size is a numerical representation of the grain size.

Limestone sludge and dust have small grain size and are hard and have a long firing time.

On the other hand, oyster shell powder, which has a larger grain size than limestone sludge and dust, is soft, generates more dust, and shortens the firing time. This is because limestone shows a difference in plastic properties depending on the grain size.

As the grain size of limestone increases, it is weak to impact and the tendency of eruption increases rapidly. This is because the larger the crystal grain size of the limestone, the greater the increase in stress inside the limestone as it is heated, resulting in more cracks. If a lot of cracks are generated, dust is likely to be generated by friction between limestones or with the inner wall of the kiln or mechanical impact due to falling.

When the grain size is large, the tendency of differentiation increases rapidly, but cracks generated during firing act as a heat transfer path through CO ₂ emission and convection, which is advantageous for firing.

And, the long firing time of limestone sludge and dust is because the grain size is small, the pores are dense, and it is difficult for CO ₂ to escape through the dense structure.

Therefore, in consideration of conditions such as differentiation rate and firing time, oyster shell powder; Limestone sludge and dust are mixed.

Because, if the ratio of limestone sludge and dust is high, the differentiation rate and hydration rate are lowered, which causes the problem of lowering the desulfurization rate when applied to the desulfurization process of steelmaking. If the ratio of oyster shell powder is high, the differentiation rate is high, and limestone sludge and dust This is because underfiring may occur if the firing time of the furnace is matched.

Oyster shell powder; In a blended raw material that combines limestone sludge and dust,

When the mixing ratio of the limestone sludge and dust is less than 60.0 wt%, the differentiation rate does not satisfy 14% or more, and when it exceeds 90.0 wt%, the hydration rate decreases, and thus the hydration rate does not satisfy 90% or more and 100% or less.

Oyster shell powder and oyster shell powder at the mixing ratio presented above; The average particle size (average size) of the blended raw material mixed with limestone sludge and dust is 19 ~ 22 mm.

The average particle size stabilizes the quality of quicklime by increasing the plasticity of the blended raw materials.

The average particle size is related to sintering, and sintering is difficult if the average particle size is excessively large.

The average particle size means the average particle diameter (diameter) of a group of distributed particles.

On the other hand, the above-described blended raw material is charged into a sintering furnace and a sintering process is performed to produce quicklime. The firing temperature of the kiln is preferably 900 to 1,250°C, more preferably 900 to 1,100°C. The firing time is preferably 2 to 6 hours.

The kiln has a structure in which a preheater is provided on one side and a burner is provided on the other side. When the mixing raw material is charged into the inside of the kiln through the preheater, it rotates and fires the mixed raw material charged therein.

The reaction formula that the blended raw material is fired in the kiln to make quicklime is shown in Reaction Equation 1 below.

[Scheme 1]

CaCO ₃ → CaO + CO ₂ ↑

That is, oyster shell powder; When the blended raw material mixed with limestone sludge and dust is heated, an endothermic reaction occurs and CaCO ₃ is decomposed to produce quicklime.

The quicklime produced after firing is taken out from the kiln, charged to a cooler, and cooled for a predetermined time to produce quicklime. This manufacturing process is as shown in FIG. 1.

If the firing temperature is lower than 900° C., the reaction of Reaction Formula 1 does not occur, and if it exceeds 1,250° C., it is underfired and the firing effect is rather inferior.

If the calcination time is less than 2 hours, the reaction as quicklime is insufficient, and if it exceeds 6 hours, it is not preferable in terms of cost.

The quicklime produced in this way has a stable quality and high quality. In addition, oyster shell powder; For blended raw materials mixed with limestone sludge and dust, the stabilization period of operation is minimized to less than one day, so that the supply and demand of quicklime raw materials are stably achieved.

Table 1 below shows oyster shell powder; It shows the hydration rate, differentiation rate, and desulfurization rate according to the mixing ratio of limestone sludge and dust.

division Limestone sludge and dust (wt%) Soft limestone (wt%) Operation stabilization period Hydration rate (%) Differentiation rate (%) Desulfurization rate (%) Comparative Example 1 0 100 3 days 100 18 - Comparative Example 2 20 80 3 days 94 17 - Comparative Example 3 50 50 3 days 93 16 43 Example 1 60 40 Less than 1 day 91 15 47 Example 2 70 30 Less than 1 day 90 15 44 Comparative Example 4 80 20 1 day 88 14 29 Comparative Example 5 100 0 1 day 87 11 19

The desulfurization rate in Table 1 is the desulfurization rate when the prepared quicklime is applied to the desulfurization process. Quicklime was tested by adding 30 kg per ton of molten steel.

Looking at Table 1, oyster shell powder; It can be seen that when limestone sludge and dust are mixed in a weight ratio of 30:70 to 40:60, the hydration rate is 90% or more and 100% or less, and the differentiation rate is 14 to 16%.

In Comparative Examples 4 and 5 in which the mixing ratio of the limestone sludge and dust exceeded 70 wt%, the hydration rate was low, and in Comparative Examples 1 to 3 in which the ratio of limestone sludge and dust was less than 60 wt%, the powder The hwa rate was high.

This is a soft limestone oyster shell powder shown in Figure 2; It is also confirmed in the graph showing the differentiation rate and hydration rate according to the mixing ratio of limestone sludge and dust of hard limestone.

2, oyster shell powder; In a blended raw material that combines limestone sludge and dust, if the blending ratio of limestone sludge and dust is less than 60 wt%, the differentiation rate does not satisfy more than 14%, and if it exceeds 70 wt%, the hydration rate decreases, resulting in a hydration rate of 90% or more. Not satisfied with less than 100%.

In addition, according to Table 1, oyster shell powder; When limestone sludge and dust were mixed in a weight ratio ranging from 30:70 to 40:60, the stabilization period was also minimized to less than 1 day.

Through this, it can be seen that the supply and demand of quicklime raw materials in actual operation is easy, and the production of quicklime with stable quality and high quality is possible.

For reference, the present invention and oyster shell powder; It has been described as an example that a blended raw material mixed with limestone sludge and dust is calcined to be used in the manufacture of quicklime, but this is not necessarily the case, and the blended raw material can be applied to the firing process of ironmaking.

The rights of the present invention are not limited to the embodiments described above, but are defined by what is described in the claims, and those of ordinary skill in the technical field of the present invention can make various modifications and adaptations within the scope of the rights described in the claims. It is self-evident.

The method for producing quicklime using oyster shell powder and limestone sludge according to the present invention has the advantage of being able to manufacture quicklime, a subsidiary raw material of the ironmaking process, by simultaneously treating marine by-products of oyster shells and iron-making by-products of limestone sludge. It has the advantage of stably supplying this stable and high-quality quicklime, so it has great industrial applicability.

Claims (6)

The mixed raw material of soft limestone and hard limestone is charged into the kiln and fired.
In the method for producing quicklime so that the hydration rate of the blended raw material is 90% or more and 100% or less, and the differentiation rate is 14 to 16%,
The blending material is oyster shell powder 30.0 ~ 40.0 wt%; Limestone sludge and dust 60.0 ~ 70.0 wt%; Quicklime manufacturing method using oyster shell powder and limestone sludge, characterized in that replaced by one consisting of.
delete delete delete delete delete

Images