JPH1087354A - Production of cement clinker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amt. of fuel used and free lime by adding a lime-contg. hydrating compsn. after use in the treatment of stack gas to prepd. starting materials and firing them. SOLUTION: A hydrating compsn. contains calcium oxide, silicon dioxide, aluminum oxide and a sulfuric acid compd. A pref. combination of starting materials is a combination of coal ash and/or a used lime-contg. waste gas treating agent with one or more among slaked lime, quick lime, gypsum and volcanic ash. When the hydrating compsn. is used in the treatment of SOx-contg. stack gas, a used stack gas treating agent contg. 40-70% CaSO4 , 5-25% Al2 O3 and 5-60% SiO2 is obtd. This used stack gas treating agent is blended with other starting materials far cement clinker so as to attain <=5wt.% CaSO4 content, a hydraulic modulus of 2.1-2.2, a silica rate of 2.5-2.1 and an iron rate of 1.6-1.7 in the case of ordinary Portland cement clinker and crushing to a prescribed particle size with a mill and firing at 1,400-1,450 deg.C for about 1hr are carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing clinker which can reduce the consumption of natural resources and calcine clinker under milder conditions than before. To be more specific, mix the used flue gas treatment agent, which absorbs and fixes sulfur oxides, nitrogen oxides, hydrogen halide compounds, etc., in the flue gas into the raw material for cement, and uses it as a raw material for cement. Production of clinker that can save resources such as limestone, clay, and silica stone, reduce the amount of carbon dioxide released from limestone, contribute to the preservation of the global environment, and reduce clinker firing conditions .

[0002]

2. Description of the Related Art Limestone, clay, silica, and iron oxide raw materials are used as raw materials for preparing Portland cement clinker. In addition, blast furnace slag mainly composed of calcium oxide, silicon dioxide, aluminum oxide, etc.
Fly ash containing silicon dioxide, aluminum oxide, iron oxide or the like as a main component is sometimes used. The ratio of the chemical components of each raw material is adjusted to a certain range and blended so that a predetermined amount of the clinker constituent compound is obtained in accordance with the type of cement to be fired.

[0003] Table 1 shows the ratio (rate coefficient) of the chemical components of each raw material for ordinary Portland cement clinker and early-strength Portland cement clinker, that is,
"Silicon dioxide (SiO ₂ ) + aluminum oxide (Al
₂ O ₃ ) + iron oxide (Fe ₂ O ₃ ) ”and“ calcium oxide (calcium sulfate correction) (CaO−0.7S)
O ₃ ) ”(abbreviated as hydraulic modulus, HM),“ Al
The proportion of "SiO _2" for ₂ O ₃ + Fe ₂ O ₃ "(silicate ratio, abbreviated as SM.), Abbreviated" percentage of Al ₂ O ₃ "(iron ratio, and IM for" Fe ₂ O ₃ " .).

[0004]

[Table 1]

[0005] In order to obtain a clinker having such a coefficient, each raw material is blended, pulverized and kilned in consideration of the amount of dust scattering during firing and the amount of coal brought in from ash. To produce cement clinker. Here, during the firing process, the limestone releases carbon dioxide gas according to the following equation. The quicklime produced from CaCO ₃ → CaO + CO ₂ reacts with other components of the raw materials to form a clinker constituent compound, ie, 3CaO · SiO ₂ , 2CaO.
_{· SiO 2, 3CaO · Al 2} O 3, 4CaO · Al 2
O ₃ · Fe ₂ O _{3 and the} like are generated.

[0006]

As is clear from the component ratios in Table 1, a large amount of resources such as limestone and silica stone are used for the production of cement clinker. In addition, a fuel for obtaining the calorific value of limestone decomposition is required. In addition, there is also a problem that a large amount of carbon dioxide gas is generated during firing, which adversely affects the global environment.

To produce one ton (t) of ordinary Portland cement clinker, typically 1140 kg of limestone,
239 kg of clay (main component: 45 to 78% of SiO ₂ ,
Al ₂ O ₃ 10~26%), and required iron oxide raw material 56kg. In addition, 111 kg of coal is consumed as burning fuel. Of this, 65 kg is consumed for the decomposition of limestone,
This decomposition releases 500 kg of carbon dioxide gas.

[0008] If CaO is present in the form of free CaO (free lime) without being a constituent compound in the clinker, the strength of the cement is reduced, causing cracks in the concrete and having a harmful effect. Since the amount of free lime is reduced by raising the firing temperature, firing should be performed at the highest possible temperature (1400
~ 1450 ° C, sometimes around 1500 ° C).

Therefore, conventionally, blast furnace slag and fly ash have been used as blending raw materials from the viewpoint of resource saving. Since blast furnace slag and fly ash do not contain CO ₂ components,
Although the amount of heat for decarboxylation is not required and the fuel efficiency is improved, the sintering temperature cannot be lowered by using them, and the amount of fuel used is large. Therefore, an object of the present invention is to save resources and fuels, suppress the generation of carbon dioxide from the viewpoint of preserving the global environment (ie, refrain from using limestone), and use other by-products and industrial materials. It is an object of the present invention to provide a method for producing a cement clinker capable of positively utilizing waste.

[0010]

The present inventors have conducted various studies to reduce the amount of fuel used, and as a result, have found that the present inventors have developed a lime-based hydrating composition which has already been developed as a flue gas treating agent. It has been found that by adding the treated composition subjected to the flue gas treatment to the prepared raw material and firing it, the amount of fuel used can be reduced and free lime decreases, and the present invention has been completed.

That is, the present invention provides: 1) a used flue gas treating agent obtained by using a hydrating composition containing calcium oxide, silicon dioxide, aluminum oxide, and a sulfate compound for flue gas treatment; 2) a method for producing a cement clinker, wherein the method comprises the steps of: 1) using a spent smoke-treating agent used for treating flue gas containing sulfur oxides; 3) The above 1 or 2 wherein the calcium sulfate component of the used flue gas treating agent is blended in an amount of 5% by weight or less with respect to the prepared raw material.
3. A method for producing a cement clinker according to (1).

Hereinafter, the present invention will be described in detail. The used flue gas treating agent used in the present invention is described in JP-A-61-20
No. 9038, JP-A-63-283745 and JP-A-64-38130. For example, flue gas treatment agents
A substance capable of supplying calcium oxide and one or more substances selected from a group of substances capable of supplying a sulfuric acid compound, a halogen element compound, silicon dioxide, aluminum oxide, sulfide, and a hydroxide of an alkali metal are mixed with water. It is manufactured as a hydration treatment composition obtained by curing with water (see JP-A-63-2837).
No. 45), in the present invention, a hydration treatment composition containing calcium oxide, silicon dioxide, aluminum oxide and a sulfate compound is used.

[0013] The hydration hardening in the hydration treatment composition means that water is added to a raw material mixture to perform hydration treatment, and a hydration reaction between various substances (raw materials) proceeds to harden.
Curing such as moist air curing, hot water curing, and steam curing is also included.
Examples of the substance that can supply calcium oxide, which is a main component of the hydration treatment composition, include quick lime, slaked lime, carbonated lime, cement, slag, dolomite plaster (containing lime), and by-products such as acetylene slag. Can be

Examples of the substance capable of supplying a sulfate compound include calcium sulfate, magnesium sulfate, sodium sulfate, gypsum, other sulfite compounds, ettringite, calcium sulfoaluminate and hydrates thereof.

Further, examples of substances that can be supplied simultaneously with at least two or more of the four components of silicon dioxide, aluminum oxide, calcium oxide, and a sulfate compound include coal ash and volcanic ash, cement and cement clinker, slag and shirasu, Clay minerals, reactive silicon dioxide such as ettringite, and minerals containing oxides and sulfates such as aluminum and calcium, desulfurized ash in the furnace such as fluidized bed combustion ash and used flue gas treatment agents, and sludge incineration Ash,
Examples include municipal waste incineration ash, cement waste, and acetylene slag.

Among the above-mentioned raw materials, a preferable combination is a coal ash and / or spent lime-based exhaust gas treating agent (consisting of substantially the same components as the above-mentioned hydrating composition, and containing slaked lime and limestone powder as other components). And slaked lime, quicklime,
It is at least one combination selected from the group consisting of gypsum and volcanic ash. In the present invention, a flue gas treating agent comprising a composition containing calcium oxide, a sulfate compound, aluminum oxide, and a silicon dioxide-based cured product obtained by mixing and hydrating and curing these materials is used as a sulfur oxide. A composition containing calcium sulfate after treating flue gas containing nitrogen oxides, hydrogen halide compounds and the like, particularly flue gas containing sulfur oxides is used.

[0017] That is, by subjecting the above composition to a known flue gas treatment, SO _x in the active calcium oxide in the composition is the flue gas, NO _X, them by catalytic reaction with hydrogen halide gas While fixed, the SO _x component is fixed as calcium sulfate.

For example, the respective component ratios of the cured product of the flue gas treating agent (hydration treatment composition) after the SO _x -containing flue gas treatment vary greatly depending on the source material, but are in the following range.

CaSO ₄ 40-70% Al ₂ O ₃ 5-25% SiO ₂ 5-60%

The used flue gas treating agent thus obtained is blended together with the other raw materials of cement so as to obtain a rate coefficient in the range as described above, and a predetermined particle size (90 μ residue Is about 10 to 20%) and provided for firing. The sintering is performed at a temperature of 1400 to 1450 ° C. for about 1 hour as in the conventional method.

The amount of the used flue gas treating agent is adjusted so that the calcium sulfate component is 5% by weight or less based on the prepared raw material. When the content exceeds 5% by weight, in a rotary kiln with a suspension preheater, the sulfur trioxide of calcium sulfate is decomposed and volatilized from around 1200 ° C and condenses again in the suspension preheater when the baking equipment is attached at around 1200 ° C, and the suspension preheater adheres to the passing raw material. This is because there is a risk of blocking.

In addition, sulfur trioxide remains in the calcined clinker, and when gypsum as a setting modifier is further added, the standard of sulfur trioxide of cement specified in JIS (3.0% for ordinary Portland cement) is used. Below, 3.5% or less for early Portland cement).
Further, if the amount of sulfur trioxide in the clinker is too large, the strength of the obtained cement may decrease.

[0023]

The saving of resources and the suppression of the generation of carbon dioxide by using the used flue gas treating agent are based on the following operations. As described above, the used flue gas treatment agent contains calcium oxide, silicon dioxide, and aluminum oxide, which are components of the cement, so that the use of natural resources can be reduced. Also, the calcium oxide contained in this is CO ₂
Since it does not contain any components, it does not generate carbon dioxide gas during heating unlike limestone.

The saving effect of the calcined fuel according to the present invention is considered as follows. When the raw material that has passed through the suspension preheater is heated in the rotary kiln to generate a clinker constituent compound, calcium sulfate contained in the flue gas treatment agent is melted, thereby lowering the melting temperature of the entire raw material.

Each raw material component reacts and binds in a molten liquid phase to form each clinker constituent compound. Calcium sulfate melts at a lower temperature than other raw materials, melts in other raw materials, and promotes their melting, thus lowering the overall liquid phase forming temperature. Therefore, the reaction for producing the clinker constituent compound also occurs at a low temperature, and the unit fuel consumption decreases.

As described above, the amount of free lime of the clinker to be obtained is reduced due to the ease of firing as a whole, and the quality of cement is improved. Iron oxide also promotes melting and acts as a component that lowers the liquid phase formation temperature.However, the use of a large amount of iron oxide has the problem of adversely affecting the strength and color tone. For example, the effect of promoting melting can be obtained without causing any problem in strength and color tone.

As a method of using gypsum and sulfur for baking clinker, Japanese Patent Application Laid-Open No. 2-33659 discloses a method in which gypsum is put in the middle of a suspension preheater. This method reduces gypsum used for cement. The purpose is. The method disclosed in Japanese Patent Publication No. 46-43398 is intended to improve the strength of early-strength cement. The present invention uses a used flue gas treating agent instead of gypsum, and aims at effective utilization and resource saving. Also, the aim is to reduce the fuel used in the kiln, which is completely different from the conventional technology.

[0028]

The present invention will be described below with reference to examples. In the following description, “%” is based on weight unless otherwise specified.

Example 1 1% of a used flue gas treating agent comprising the chemical components shown in Table 2
With the aim of the mixing ratio of limestone, granulated slag, quartzite, iron raw material, and various cement raw materials such as iron ash and coal ash, they are blended so that the coefficient of clinker becomes the value of Table 3 and pulverized by a raw material mill. A prepared raw material for Portland cement clinker was obtained. Comparative Example 1 is a normal blending of the blended raw materials without using the used flue gas treating agent.

[0030]

[Table 2] Table 2: Chemical components of used flue gas treatment agent Content (%) Ignition loss 14.7 SiO ₂ 23.7 Al ₂ O ₃ 7.9 Fe ₂ O ₃ 2.1 CaO 25.5 SO ₃ 24.9

[0031]

[Table 3] Table 3: Target rate coefficient of ordinary Portland cement clinker Hydraulic rate 2.20 Silica rate 2.60 Iron rate 1.60

[0032]

[Table 4] Table 4: Formulation of blended raw materials (kg / clinker / t) Kind of raw material Example 1 Comparative example 1 Limestone 1185 1203 Granulated slag 153 162 Silica 69 64 Iron oxide raw material 42 41 Coal ash 30 29 Smoke exhaust agent 1 50 Total 1494 1499

In the examples using the used flue gas treating agent as a raw material, the amount of limestone used per ton of clinker is reduced as compared with the comparative example. Also, the total amount of raw materials has decreased. It is considered that the reduction in the amount of limestone used reduced the amount of carbon dioxide gas released by decomposition and reduced the total amount. These prepared raw materials were fired in a five-stage NSP kiln (4.2 mφ × 61 mL, 3000 t class / day production capacity) to produce cement clinker. Production capacity at that time,
Table 5 shows the unit fuel consumption in terms of heavy oil (in terms of liter of heavy oil per ton of clinker) and the amount of free lime of the produced clinker.
Shown in

[0034]

[Table 5] Table 5: Firing capacity, unit fuel consumption Kind of raw material Example 2 Comparative example 2 Clinker production capacity (t / h) 118.7 120.2 Fuel consumption unit (l / clinker t) 73.9 78.0 Clinker free lime amount (%) 0.6 0.9

The fuel consumption rate of the example is greatly reduced as compared with the comparative example, the amount of free lime of the clinker is also reduced, and the effect of the used flue gas treating agent is recognized.

Example 2 Spent used chemical components shown in Table 6 (according to the Cement Institute of Japan standard test method “Chemical analysis method of siliceous raw materials” CAJS 1-12 and JIS R 5202 “Chemical analysis method of Portland cement”) The smoke treatment agent was mixed with various cement raw materials, such as limestone, granulated slag, silica stone, iron raw material, and coal ash, in the same manner as in Example 1, with a mixing ratio of 2% as a target, so that the coefficient of clinker became the value shown in Table 7. Then, the mixture was pulverized in a raw material mill to obtain a compounded raw material for Portland cement clinker shown in Table 8 at an early stage. Comparative Example 2 is a blending of a blended raw material at normal time without using a used flue gas treating agent.

[0037]

[Table 6] Table 6: Chemical components of used flue gas treatment agent Content (%) Ignition loss 14.2 SiO ₂ 23.6 Al ₂ O ₃ 7.9 Fe ₂ O ₃ 3.5 CaO 25.3 SO ₃ 24.2

[0038]

[Table 7] Table 7: Target rate coefficient of early-strength Portland cement clinker Hydraulic rate 2.26 Silicate rate 2.72 Iron rate 1.65

[0039]

Table 8: Formulation of blended raw materials (kg / clinker / t) Kind of raw material Example 2 Comparative example 2 Limestone 1130 1211 Granulated slag 218 189 silica stone 81 68 Iron oxide raw material 44 44 Smoke exhaust agent 300 0 Total 1503 1512

In the embodiment using the used flue gas treating agent as the raw material, the amount of limestone used per ton of clinker and the total amount of the raw material are reduced as compared with the comparative example, similarly to the case of ordinary Portland cement. I have. It is believed that the reduced amount of limestone also reduces the amount of carbon dioxide generated. These prepared raw materials were fired in a five-stage NSP kiln as in the case of ordinary Portland cement to produce a cement clinker. Table 9 shows the production capacity at that time, the unit fuel consumption in terms of heavy oil, and the amount of free lime of the produced clinker.

[0041]

[Table 9] Table 9: Firing capacity and fuel consumption Kinds of raw materials Example 1 Comparative Example 1 Clinker production capacity (t / h) 110.2 104.0 Fuel intensity (l / clinker t) 76.7 84.0 Free lime content of clinker (%) 0.9 1.3

The fuel consumption rate is greatly reduced in the example compared to the comparative example. Further, the amount of free lime of the clinker was also reduced as compared with the comparative example, and the effect of the used flue gas treatment agent was recognized.

[0043]

As described above, the present invention contains calcium oxide, silicon dioxide, aluminum oxide and a sulfate compound, and fixes sulfur oxides, nitrogen oxides, hydrogen halide compounds and the like in flue gas. It mixes used flue gas treating agent into the raw material of cement, which not only saves natural resources but also reduces clinker sintering conditions. .

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Kunihiro Mori 163-1 Nagawacho, Date City, Hokkaido Hokkaido Electric Power Company, Date Power Plant Co., Ltd. (72) Takeshi Murayama 2-1 Egan-shi vs. Goose Hokkaido Hokkaido Electric Power Company In-house (72) Inventor Tsukasa Ueno 2-1 Egan-shi vs. Goose Hokkaido Hokkaido Electric Power Company Research Institute

Claims (3)

[Claims] A hydrate treatment composition containing calcium oxide, silicon dioxide, aluminum oxide and a sulfuric acid compound is used in a flue gas treatment, and a used flue gas treating agent is mixed with a raw material for cement mixing and calcined. A method for producing a cement clinker. 2. The method for producing a cement clinker according to claim 1, wherein a spent flue gas treating agent used for treating flue gas containing sulfur oxides is used. 3. The method for producing a cement clinker according to claim 1, wherein the calcium sulfate component of the used flue gas treatment agent is blended in an amount of 5% by weight or less based on the prepared raw material.