CN1556060A

CN1556060A - Full fly ash building brick and its manufacturing method and special additive

Info

Publication number: CN1556060A
Application number: CNA2003101097364A
Authority: CN
Inventors: 鹏刁; 刁鹏
Original assignee: SHANXI MINXING INDUSTRY Co Ltd
Current assignee: SHANXI MINXING INDUSTRY Co Ltd
Priority date: 2003-12-31
Filing date: 2003-12-31
Publication date: 2004-12-22
Anticipated expiration: 2023-12-31
Also published as: CN1280228C

Abstract

A flyash brick for building is prepared from the flyash (90-96 wt.%) and the composite additive (4-10 wt%) containing water glass, alkaline oxide or the alkaline compounds, bentone, and iron oxide. Its advantages are high strength and low cost.

Description

Full fly ash building brick and its making method and special additive

Technical Field

The invention relates to a building brick using fly ash as a raw material, a manufacturing method thereof and a special additive for producing the building brick.

Background

The fly ash is used as raw material to produce building brick, but the fly ash brick of the prior art is mostly low in mixing amount, generally not more than 40%, and the rest raw materials are mostly high-plasticity high-quality clay, or crushed clayey coal gangue or clayeyshale (crushed), some of which are all the same. The production process is mainly wet production, namely adding water with the amount of more than 20 percent, and performing vacuum extrusion forming. The plasticity index of the blank is greater than 7, so that a series of large power equipments are needed to meet the technological requirements of raw material pretreatment, kneading and pugging. Therefore, a large amount of capital is occupied in equipment investment, and the inevitable result that the product consumes much power and has high cost is brought, so that the product is difficult to obtain market acceptance and is not competitive with clay bricks. Secondly, the raw material proportion still needs a large amount of clay materials, which neither meets the national policy of protecting cultivated land, natural ecology and wall material reformation, nor can really meet the requirement of coal ash treatment. Thirdly, most of the existing fly ash bricks are insufficient in strength and are used as partition wall material bricks in large quantity, and after the current state adopts the policy of restricting clay bricks, the market low-rise buildings need new bricks for bearing walls to replace the clay bricks.

Chinese patent 02129387.2 discloses a high-content flyash sintered brick for building and its preparation method, in which the flyash content can be up to 85-95 weight portions, and the rest is sodium-base bentonite and modified additive formed from magnesium sulfide, ferric oxide and ferrous oxide. The highest content of the fly ash can only reach 86.36 percent in percentage, while the cost of the expensive sodium bentonite and the modifying additive is at least 13.64 percent, and the cost of the finished product is obviously higher and is difficult to be established in the market. In addition, the fly ash brick is produced by a wet method, the water content reaches 18-22%, the mixture must be subjected to a high-power mud kneading pretreatment andextrusion cutting blank making process, the investment of the equipment is large, the energy consumption is high, the brick making cost is high, the large-scale popularization is difficult, and the product lacks competitiveness. Further, since the water content is large, the drying time is inevitably increased, and even if the hot air drying is performed, it is usually 8 to 14 hours. Thirdly, since the basic components of the fly ash are silicon dioxide and aluminum oxide microbeads which have high hardness, most of the microbeads are difficult to crush by rolling according to a common process. The presence of a large number of microbeads directly affects the strength of the finished brick.

The Chinese patent 91110966.8 discloses a flyash brick and its production process, the flyash content of said flyash brick can be up to above 95%, and the rest 3-5% of water glass can be used as adhesive, and its existent defect is that the water glass content is too high. The price of the water glass in the current market is 700 yuan per ton, the cost of the water glass converted into each standard brick is 0.07 yuan calculated by 5 percent of admixture, the price of the water glass is almost the same as that of the clay brick in the current market, and the cost of each brick is about 0.15 yuan in addition to other costs, so that the market is difficult to bear. In addition, the fly ash component of the brick has the advantages of complex production process, long time and long drying time, and the drying time is still 36 to 48 hours when the brick is dried by using a drying medium in an artificial environment. The roasting time is about 17-20 hours, the temperature needs to be increased in a step-type manner in the roasting process, the process control is not easy to master, and the quality of the brick is difficult to ensure.

Disclosure of Invention

Aiming at the defects in the prior art, the invention develops a full fly ash building brick, a manufacturing method and a special additive thereof, and improves the production method of the existing fly ash brick. The high-fly ash content building brick of the invention has the advantages of large fly ash content, simple production process and low cost. The production process of the invention has the advantages of simple required equipment, less investment and short plant construction period. The special additive has wide raw material source and low price, can greatly reduce the production cost, shorten the production period, effectively reduce the total cost of the product, and has higher economic and social benefits.

The brick contains 90-96 wt% of fly ash and the rest is additive; wherein the additive is a composite additive, the components of the composite additive contain water glass, and also contain alkali, bentonite or the like and/or iron oxide, wherein the content of the alkali is 30-60% (by weight); the content of bentonite or its congeners is 10-40% (by weight); the water glass content is 5-10 wt%; the iron oxide content is 10-40% by weight.

The all-fly ash building brick comprises an alkaline oxide, a hydroxide or a carbonate (normal salt), wherein the alkaline oxide is lime powder (CaO is more than or equal to 60 percent), and the alkaline oxide can be replaced by the hydroxide or the carbonate (normal salt) with equivalent weight.

The full fly ash building brick is characterized in that hydroxide is NaOH in papermaking waste liquidOr alkali substances in other alkaline waste liquid, wherein the carbonate (normal salt) is Na in the alkaline earth₂CO₃Or the like.

The preferred content of the fly ash in the full fly ash building brick is 95 percent (weight), and the preferred content of the composite additive is 5 percent (weight).

The method for manufacturing the full fly ash building brick comprises the following steps:

a. preparing materials, namely putting 90-96% (by weight) of fly ash into a stirrer;

b. preparing additive, taking 4-10% of composite additive (by weight), adding 10-12% of water (by weight of the dry fly ash) with the temperature of more than 60 ℃, fully stirring and hydrolyzing;

c. mixing and stirring, namely mixing the fly ash and the hydrolysis composite additive and then stirring strongly to fully mix the fly ash and the hydrolysis composite additive;

d. aging the blank, heating and standing the stirred blank for about one hour;

e. rolling the blank, and continuously rolling the aged blank for 3-10 minutes by using an edge runner mill;

f. secondarily aging the blank, and heating and standing the rolled blank for about one hour;

g. secondarily rolling the blank, and using a mixing mill to roll the re-aged blank for 2-5 minutes;

h. molding, namely molding the blank after the secondary milling;

I. drying to make the water content of the green brick less than 6%;

J. and (3) putting the dried green bricks into a kiln for roasting, keeping the temperature constant for 2 hours when the temperature in the kiln is raised to about 1000 +/-50 ℃, and then gradually reducing the temperature to the normal temperature and taking the green bricks out of the kiln.

The special additive for producing the building brick with the whole fly ash contains water glass, alkaline inorganic matters, bentonite or the like and iron oxide, wherein the water glass content is 5 to 10 percent (by weight); the alkaline inorganic substance is lime powder (CaO is more than or equal to 60 percent), the content is 30 to 60 percent (weight), or equivalent sodium carbonate (Na)₂CO₃) Or equivalent sodium hydroxide (NaOH), the content of the bentonite or the congener thereof is 10-40% (weight), and the content of the iron oxide is 10-40% (weight).

Special additive for producing building brick from fly ash, sodium carbonate (Na) therein₂CO₃) Is obtained from alkaline earth or its congener, and sodium hydroxide (NaOH) is obtained from paper-making waste liquid or other alkaline waste liquid.

The special additive for producing the building brick with the whole fly ash comprises 6 to 8 weight percent of water glass; the preferable content of the lime powder (CaO is more than or equal to 60 percent) is 35 to 55 percent (by weight), orEquivalent amount of earth alkali (Na)₂CO₃) Or equivalent papermaking waste liquid (NaOH is used as an effective component); the preferred content of said bentonite is 15-30% by weight; the iron oxide is preferably present in an amount of 10 to 30% by weight.

The special additive for building brick made of full fly ash is prepared from iron oxide FeO or ferric oxide Fe₂O₃。

The full fly ash building brick of the invention can save a large amount of cultivated land and increase the fly ash consumption because the fly ash mixing amount can reach more than 95 percent and clay is not basically used as an additive, 13 ten thousand tons of fly ash are used per year in a brickyard producing 6000 ten thousand standard bricks per year, which is equivalent to the annual fly ash output of a large-scale generator set. The brick for the building is high in quality, completely meets the requirements of national standards on bearing bricks for the building, and the detection data are shown in table 1.

Table 1 for comparing the quality data of the bricks for construction made of all fly ash

	Compressive strength	High folding strength	Freezing and thawing	Error in dimension	Appearance of the product Quality of	Lime Burst out	Color wash Color(s)
	Compressive strength	High folding strength	Freezing and thawing	Error in dimension				Unit of	Mpa	Mpa	15 times of	±mm
National standard	10		15	3				Unit of	Mpa	Mpa	15 times of	±mm	Clear corners Six-face smooth and clean
National standard	10		15	3	The invention	≥15	≥4	Qualified	2	Clear corners Six-face smooth and clean	Superior product	Light red	Clear corners Six-face smooth and clean

In addition, the full-fly ash building brick does not need to be added with clay, so that the transportation cost is reduced. The additive is less in use amount, the main component of the additive is common lime powder, and the cost is lower, so that the overall cost is greatly reduced, and the cost of each brick is less than or equal to 0.08 yuan. Can meet the requirement of replacing clay bricks as bearing bricks for buildings at present and can also be used as partition bricks.

The method for manufacturing the all-fly ash building brick has the advantages that the added water amount is less, only 10-12% of the total weight of dry materials is used, the method belongs to the field of semi-dry material brick making, high-power mud kneading pretreatmentequipment and extrusion cutting blank making equipment are omitted, a large amount of equipment investment can be saved, the time and power consumption cost in the brick making process is reduced, and the installed capacity of a brick factory which produces 6000 million standard bricks per year is less than 300 KW. Compared with the existing fly ash sintered brick factory, the cost is reduced by 45-75%, and the electricity consumption cost of each brick can be reduced by 1.5-2.5 cents. The investment for building the factory can be reduced by 30-85%. In addition, the water adding amount is small, so that the drying time and the sintering time are shortened, and the comprehensive cost can be effectively reduced.

Secondly, the brick making method of the invention adds the alkaline additive to carry out alkali activation on the fly ash, and adopts two times of aging on the blank, which is beneficial to softening and crushing the fly ash particles, so that the fly ash surface is fully contacted with the composite additive, the alkali activation reaction is more thorough, and the mixture of the fly ash and the additive in a gel state is formed. Is beneficial to blank making and sintering, reduces the blank making and sintering time and lowers the sintering temperature.

Thirdly, the spherical fly ash particles are crushed by two times of rolling to form irregular micro-particles, which is beneficial to the tight combination of the particles and ensures that the molding is more compact. In addition, the fly ash and the composite additive can be fully combined, and a gel-state mixture is formed on the surface, so that the molding is facilitated and the strength of a finished brick is improved.

The composite additive of the invention mainly uses lime powder (CaO), and has very low cost (lower cost if alkaline earth or papermaking waste liquid is used, and environmental protection benefit).Because it is a composite type, the comprehensive effect of each component is to reduce the production cost on the premise of improving the quality of the fly ash brick, therefore, the comprehensive economic and social benefits are very obvious. Is beneficial to large-scale popularization and application.

The additive is alkaline matter, and has softening effect on silicate grains and aluminate grains in the fly ash, so that the additive is favorable for crushing the silicate grains and the aluminate grains, can form gel-state substances with the surfaces of the silicate grains and the aluminate grains, and is favorable for improving the bonding strength of the brick and the forming of the brick.

The bentonite can improve the wet strength of the brick, improve the yield of the brick and reduce the cost. Particularly, the cost is lower when the waste sludge is used conditionally, and the method has obvious environmental protection and social benefits.

After water glass is added, the dry strength of the brick can be effectively improved. Furthermore, the water glass can be replaced by a mixture of waste flour from flour mills and caustic soda. The cost is lower.

By adopting the additive, the proportion of the fly ash in the brick is greatly improved from 45-86% of the current common proportion to 95% or even higher. Provides a feasible technical proposal for thoroughly solving the pollution of the fly ash and changing waste into benefit.

The composite additives of the invention are all low melting point substances, and are mixed with the fly ash and fully contacted after rolling, thereby effectively reducing the sintering temperature of the fly ash brick, which is generally not more than 1000 ℃, so that the process requirements can be met by using the prior annular kiln for brick making, and the sintering can be carried out without using a high-temperature resistant special kiln built by refractory bricks.

Detailed Description

The brick for building is produced with flyash and through the following steps;

firstly, preparing a composite additive, namely mixing 60 parts of lime powder (CaO is more than or equal to 60%), 20 parts of bentonite, 6 parts of water glass and 14 parts of ferrous oxide powder according to the weight percentage, crushing, and screening to obtain powder with the granularity of about 200 meshes, preferably less than 200 meshes.

5 tons of the composite additive and 95 tons of power plant fly ash are taken for standby.

Heating 8-10 tons of water (8 tons in winter and 10 tons in summer) to above 60 deg.C, and heating to 70-80 deg.C in winter. The composite additive is put into water and fully stirred for about 5 to 10 minutes. Making into additive slurry.

The additive slurry and the spare fly ash raw material are put into a stirrer to be mixed and stirred for 5 to 6 minutes, and then a moisture-keeping measure (such as covering or sealing) is added to heat and stand for 1 hour. So that the activation reaction of the alkaline substance (the calcium oxide in the lime powder is converted into the calcium hydroxide) on the fly ash is fully carried out. The surface of the fly ash particles is softened, and the broken particles react with calcium hydroxide to generate gel. As the main components of the fly ash are silicon dioxide and aluminum oxide microbeads, the reaction formula after the fly ash is mixed with alkaline substances is as follows:

and (3) continuously rolling the aged raw materials in an edge runner mill for 3-5 minutes to crush the fly ash which is originally hollow glass microspheres to form irregular fly ash micro-particles. And standing for about 1 hour, namely performing secondary aging, and continuously reacting free calcium hydroxide (alkaline substance) with the new surface of the particle exposed after rolling to generate new gel. At this time, secondary milling is performed by an edge runner mill for about 2 to 3 minutes in order to further pulverize the fly ash and to homogenize the pulverized particles.

After the steps, the preparation process of the raw materials is basically finished. And (3) making the raw materials into blanks by a forming machine and forming. Because the semi-dry material is molded, a hydraulic molding machine is preferably selected to manufacture the green brick so as to ensure the compactness of the green brick.

And (4) stacking and drying, wherein if a natural drying method is adopted, the time is different according to different regions and seasons, and the stack can be put into a kiln for roasting until the water content is less than 6%. If in wet season or winter, the green bricks can be dried by selecting artificial environment. The method of the invention adopts the molding mode of the semi-dry material, so the drying time is short, and the natural drying time is about 10 hours in 4-5 months in northern areas after tests, thereby the requirements can be met. If the drying is carried out by the waste heat of the annular kiln, the standard of entering the kiln can be achieved in less than 4 hours.

The brick blank is baked, because the main component of the brick blank is fly ash which contains a certain amount of carbon element, no additional fuel is needed, and the brick blank is sintered by spontaneous combustion after ignition. Because the components of the coal ash after the coal combustion in different areas are slightly different, the sintering temperature of the green brick is slightly different along with the difference of the coal ash raw materials, generally between 950 ℃ and 1050 ℃, when the temperature reaches the sintering temperature, the temperature is kept for 1.5 to 2 hours, the temperature can be reduced, and the green brick is taken out of the kiln after being cooled to the normal temperature.

The amount of the fly ash in the full fly ash building brick is directly related to the amount of the composite additive. If the content of effective components in lime powder or alkaline earth in the additive is low, for example, less than 60%, the proportion of the composite additive can be increased, but the maximum content cannot exceed 10% of the total weight. If the content of the effective components in the additive is higher, for example, more than 80%, the proportion of the additive can be reduced to 4%. Some specific examples of the ratio of fly ash to the composite additive in the all fly ash building bricks of the present invention are shown in Table 1.

TABLE 2

Examples	Fly ash and additive Ratio of contents	Additive composition and content (specific gravity% in total weight)
Examples	Fly ash and additive Ratio of contents					1	95∶5	Lime powder 3	Bentonite 1	0.3 parts of water glass	Ferrous oxide 0.7
2	94∶6	Alkaline earth 2.4	Refractory earth 1.8	0.48 parts of water glass	Iron oxide 0.72	1	95∶5	Lime powder 3	Bentonite 1	0.3 parts of water glass	Ferrous oxide 0.7
2	94∶6	Alkaline earth 2.4	Refractory earth 1.8	0.48 parts of water glass	Iron oxide 0.72	3	90∶10	Papermaking liquor 4.5	Cellulose 1	0.5 parts of water glass	Ferrous oxide 4
4	96∶4	Lime powder 1.2	Bentonite 1.6	0.4 parts of water glass	Iron oxide 0.8	3	90∶10	Papermaking liquor 4.5	Cellulose 1	0.5 parts of water glass	Ferrous oxide 4
4	96∶4	Lime powder 1.2	Bentonite 1.6	0.4 parts of water glass	Iron oxide 0.8	5	93∶7	Alkali of earth 3.2	Refractory soil 2.45	0.35 parts of water glass	1

In the above table, example 3 uses a paper mill effluent containing a relatively large amount of cellulose, and thus the amount of cellulose used is correspondingly reduced. In addition, the amount of water used should be correspondingly reduced when using paper-making waste liquor.

The amount of ferrous oxide used was increased in example 3 because the fly ash contained a greater amount of alumina, which is a high melting point material. In order to lower the firing temperature, therefore, the proportion of the low-melting ferrous oxide is increased. The ferrous oxide and the ferric oxide have the effects of coloring, so that the color of the brick is common red, and the brick is suitable for serving as an outer wall bearing brick. And secondly, the method is used for adjusting the roasting temperature, and when the content of high-melting-point substances in the fly ash is higher, the iron oxide is added, so that the roasting temperature can be reduced.

Additive and preparation: the additive components of the invention comprise lime powder or other inorganic alkaline substances such as sodium carbonate or sodium hydroxide; bentonite or other materials that can improve green strength, such as refractory or cellulosic or sewage plant, paper mill, drinking water plant sludge, and the like; water glass or other similar materials that can improve the green strength of the tile, such as a mixture of flour and caustic soda; the components are necessary for ensuring the quality of the fly ash brick.

In order to meet the aesthetic effect when the brick is used as an outer wall bearing brick, a proper amount of ferrous oxide powder or ferric oxide powder can be added for adjusting the color of the finished brick and the roasting temperature of the fly ash brick.

The content of calcium carbonate in the lime powder is usually more than 60%, and in the inorganic alkaline substance used for replacing the lime powder, the common low-cost soil alkali (the main component of which is sodium carbonate Na) is₂CO₃) Or paper-making waste liquid (the main component of which is sodium hydroxide NaOH). When substituted, the chemical equivalents of the active ingredients should be equal. When the alkaline earth is used, the content of effective components is low, so the dosage is large, and the total dosage of the additive is increased.

The proportion of each main component is as follows: 30-60% of lime powder; 10-40% of bentonite; 5-10% of water glass; 10-40% of iron oxide. The raw materials are mixed according to a certain proportion and then crushed, and the powder obtained by screening with a screening device with more than 200 meshes is the composite additive of the invention. When in use, the fly ash brick is firstly mixed with water in a certain proportion to form slurry, and then mixed with fly ash in a certain proportion and stirred, thus completing the preparation process of the high-doped fly ash brick raw material. The compounding ratio of the composite additive of the present invention is shown in Table 3:

table 3100% (by weight)

	Alkaline substance 30-60			Material for increasing wet strength 10-40			5-10 parts of water glass	Iron oxide 0-40
	Alkaline substance 30-60			Material for increasing wet strength 10-40			5-10 parts of water glass	Iron oxide 0-40			Lime powder CaO	Alkali earth Na₂CO₃	Papermaking liquid NaOH	Swelling and swelling Soil for soil	Fire-resistant Soil for soil	Cellulose, process for producing the same, and process for producing the same	Water glass	Substitution Article (A)	Oxidation by oxygen Ferrous iron	Oxidation by oxygen Iron
Example 1	60			20			6	14			Lime powder CaO	Alkali earth Na₂CO₃	Papermaking liquid NaOH	Swelling and swelling Soil for soil	Fire-resistant Soil for soil		Water glass	Substitution Article (A)	Oxidation by oxygen Ferrous iron	Oxidation by oxygen Iron
Example 1	60			20			6	14		Example 2		40			30			8		12
Example 3			45			10	5	40		Example 2		40			30			8		12
Example 3			45			10	5	40		Example 4	30			40				10		20
Example 5		50			35		5		10	Example 4	30			40				10		20

In the above table, in the material for increasing the green strength of the green brick, besides the refractory clay, bentonite and cellulose, waste sludge from sewage plants, paper mills, drinking water plants and the like can be used as a substitute. It is less costly.

The water glass substitute for increasing the dry strength of the green brick is ground flour of a flour mill added with a small amount of caustic soda. Wherein the waste flour accounts for 80 percent (weight) and the caustic soda accounts for 20 percent (weight). In this case, the proportion of the additive in the composite additive should be 8-10 wt%. The use of such alternatives results in lower costs.

Claims

1. A kind of whole fly ash building brick, contain 90-96% (weight) of fly ash, the surplus is the additive, the said additive is the composite additive containing water glass, characterized by that the composite additive composition also contains alkaline material, bentonite or its congeneric substance and iron oxide, wherein, the alkaline material content is 30-60% (weight); the content of bentonite or its congeners is 10-40% (by weight); the water glass content is 5-10 wt%; the iron oxide content is 10-40% by weight.

2. The building brick made of full fly ash according to claim 1,wherein said basic substance comprises basic oxide, hydroxide, carbonate (normal salt), said basic oxide is lime powder (CaO is more than or equal to 60%), which can be replaced by equivalent amount of hydroxide or carbonate (normal salt).

3. The building brick made of full fly ash according to claim 2, wherein said hydroxide is NaOH in paper making waste liquid or alkaline substance in other alkaline waste liquid, and said carbonate (normal salt) is Na in earth alkali₂CO₃Or the like.

4. A full fly ash building brick as claimed in claim 1, 2 or 3 wherein said fly ash is preferably present in an amount of 95% by weight and said composite additive is preferably present in an amount of 5% by weight.

5. A method for manufacturing a full fly ash building brick comprises the following steps:

c. stirring, namely mixing the fly ash and the hydrolysis composite additive and stirring strongly to fully mix the fly ash and the hydrolysis composite additive;

d. aging the blank, heating and standing the stirred blank for about one hour;

f. performing secondary aging on the blank, heating and standing the rolled blank for about one hour;

g. secondarily milling the blank, and then milling the aged blank again for 2-5 minutes by using a mixing mill;

h. molding, namely molding the blank after the secondary milling;

I. drying to make the water content of the green brick less than 6%;

6. A special additive for producing the building brick of whole fly ash contains water glass, and is characterized by also containing alkaline matter, bentonite or its similar matter and iron oxide, the content of the water glass is 5-10% (weight); the alkaline substance is calcium oxide, and the content is 30-60% (by weight), or equivalent sodium carbonate (Na)₂CO₃) Or equivalent amounts of sodium hydroxide (NaOH); the content of the bentonite or the congener thereof is 10 to 40 percent (weight); the iron oxide content is 10-40% by weight.

7. The special additive for producing the all-fly ash building brick according to claim 6, wherein the alkaline oxide is obtained from lime powder (CaO is more than or equal to 60%), the sodium carbonate is obtained from soda ash or the like, and the sodium hydroxide is obtained from paper-making waste liquid or other alkaline waste liquid.

8. The special additive for producing all-fly ash building bricks according to claim 6, wherein the preferable content of said water glass is 6 to 8% by weight; the preferable content of the lime powder (CaO is more than or equal to 60percent) is 35 to 55 percent (weight) or equivalent of soda ash (Na)₂CO₃) Or equivalent papermaking waste liquid (NaOH is used as an effective component); the preferred content of said bentonite is 15-30% by weight; the iron oxide is preferably present in an amount of 10 to 30% by weight.

9. The special additive for producing a whole fly ash building brick according to claim 8, wherein the optimum content of said water glass is 7% by weight; the optimal content of the lime powder (CaO is more than or equal to 60 percent) is 50 percent (weight) or equivalent of soda ash (Na)₂CO₃) Or equivalent papermaking waste liquid (NaOH is used as an effective component); the optimum content of said bentonite is 30% by weight; the iron oxide content is preferably 13% by weight.

10. The special additive for the whole fly ash building brick according to any one of claims 6 to 9, wherein the iron oxide is ferrous oxide or ferric oxide.