RU2342337C1 - Method of production of cement clinker - Google Patents

Abstract

FIELD: building.

SUBSTANCE: invention concerns industry of building materials, mainly, method of production of a cement clinker with mineral additives. In method of production of cement clinker with the mineral additive, including raw mix roasting in the rotating furnace, feed of the mineral additive in a refrigerator to the received heated clinker, chilling, grinding, as the mineral additive use rubble of by-product overburden of coal mining or a carbonaceous technogenic waste of fraction of 5-50 mm, with the coal content in limits from 5 to 15 wt %, supply of the specified additive is performed in quantity from 5 to 50 wt % from the clinker in its stream falling from the furnace.

EFFECT: creation of effective method of production of cement clinker with mineral additives.

4 ex, 1 tbl

Description

The present invention relates to the construction materials industry, mainly to methods for the production of cement clinker with mineral additives.

A known method for the production of cement clinker with mineral additives, including the supply of mineral additives, for example, phosphogypsum in a rotary kiln (see, for example, ed. Certificate of the USSR No. 270566, class C04B 7/44, 1968).

However, this method leads to increased dust removal from the furnace, to an uneven distribution of the additive along the entire length of the rotary kiln, which reduces the effectiveness of their action.

There is also a known method for the production of cement clinker, in which a silicate-containing mineral additive — blast furnace granulated slag — is supplied from the hot end of a rotary kiln (see, for example, ed. Certificate of the USSR No. 576761, class C04B 7/44, 1974). The disadvantage of this method is the addition of slag to the clinker in the furnace, a decrease in its basicity and low hydraulic activity of the cement obtained in this process.

In another well-known solution (see, for example, ed. Certificate of the USSR No. 1280839, class С04В 7/44, 1974), a mineral additive for quick cooling of clinker in the refrigerator is fed to a layer of hot clinker towards the cooling air. As a cooler in this method, blast furnace granulated slag with a moisture content of 10% is used. Moreover, if the temperature of the clinker exiting the furnace is 1150-1200 ° C, and when cooling only with air in the region of the second window of the refrigerator - 850 ° C, then when the slag is fed into the refrigerator according to the known method, the temperature of the material in the region of the second window of the refrigerator is already 600-675 ° C, and at the outlet of the refrigerator - 60-80 ° C instead of 200 ° C. At the same time, the output of clinker increases, its grinding ability increases slightly.

However, the irrevocable and unstable slag removal into the furnace with secondary air amounts to 10-20% of the initial mass in the known method and requires constant operational adjustment of the raw material mixture, which turned out to be a very difficult operation, which does not provide stable cement activity, which varies significantly.

Closest to the proposed technical essence is a method of increasing the yield of cement clinker to obtain cement with mineral additives, including firing the raw material mixture in a rotary kiln, cooling clinker in the refrigerator with the simultaneous supply of mineral additives to a layer of hot clinker and co-grinding the clinker with additives (see , for example, RF patent No. 2288900, class C04B 7/43, 2002). In this method, to increase the yield of cement clinker from the firing plant, crushed materials with a high content of silicon dioxide and additionally containing calcium, aluminum, or both, capable of reacting with silicon dioxide at an elevated temperature, are introduced into the hot clinker as a mineral additive in a refrigerator to form crystalline calcium silicates and aluminum silicates. At the same time, coal ash, blast furnace slag, and volatile silicon dioxide (a by-product of the production of silicon or iron and silicon alloys) can be used as a mineral additive.

According to a known method, these additives are introduced into the cement clinker layer either in the region of the discharge end of the furnace or in the region of the upstream end of the refrigerator under the layer of hot clinker.

However, when feeding the crushed additive at the outlet end of the furnace, it is quite difficult to ensure an even distribution of the additive over the entire clinker flow width, and when introducing from under the clinker layer in the region of the upstream end of the refrigerator, significant losses of the unburnt (semi-burnt) additive with intense cooling air flows are possible its high dispersion.

It should be noted that the main content of the considered known solution is to increase the volume of outgoing clinker. However, the implementation of the known technical solution, which provides for the mandatory chemical reaction of at least 50% wt. additives of a siliceous composition with clinker significantly affect the decrease in the clinker saturation coefficient with lime and worsen the mineralogy of cement, reducing the content of C ₃ S and reducing the activity of cement. Such a chemical reaction occurs only in a rotary kiln, and during the stay in the refrigerator, where temperatures fall from 1300-1350 ° C to 600-700 ° C for 5-10 minutes, mineral formation reactions with clinker cannot take place.

The purpose of the invention is to increase the production of cement clinker and cement, reducing its cost, maintaining the quality of cement.

This goal is achieved by the fact that in the method of increasing the yield of cement clinker to obtain cement with mineral additives, including burning the raw material mixture in a rotary kiln, cooling clinker in the refrigerator with the simultaneous supply of mineral additives to a layer of hot clinker and joint grinding of clinker with additives, the mineral additive is fed in the flow of hot clinker falling from the furnace, while gravel of associated overburden of coal mining of a fraction selected in the range of 5 to 50 mm is taken as an additive with soda zhaniem coal in the range of from 5 to 15 wt.%, and the amount of additive selected volume from 5 to 50% by weight. clinker. In addition, appropriate granular (lumpy) aluminosilicate carbon-containing technogenic wastes can be used as a mineral additive.

The essence of the proposed technical solution is as follows. When a carbon-containing mineral additive with ambient temperature and low humidity is fed into the stream of hot clinker falling from the furnace, the temperature of which reaches 1250–1300 ° С, the crushed stone of the mineral additive undergoes intense heating and undergoes “thermal shock”, which leads to to its cracking, thermal activation and the formation of a "fluidized" layer together with cement clinker. The red-hot clinker intensively gives off heat to dispersed (5-50 mm) additive particles, being well cooled in the "fluidized" layer, and requires the supply of a smaller volume of cold air for its cooling. This significantly improves the work of grates, protecting them from overheating with a hot clinker

In contrast to the prototype, the fine coal fraction (gas suspension) formed according to the claimed method is carried away by the secondary air stream into the furnace, making up no more than 3-5% by weight of the dry mineral additive, and burns completely in the sintering zone, entering into exothermic clinker reactions melt, forming an additional amount of clinker without impairing its mineralogy. A small additive of gas suspension in the furnace from the content of coal in the additive improves its heat balance and increases its productivity without additional heat consumption for firing. Small volumes of water vapor falling into the hot end of the furnace have a catalytic positive effect on the firing regime. When in contact with lumpy particles of the additive, the hot clinker is intensively cooled and, due to evaporation of moisture and heat transfer in the layer of materials of the refrigerator, improves the thermal operating mode of the refrigerator, increasing its reliability.

Due to the supply of the mineral additive to the incident clinker stream, which has a maximum temperature at the furnace exit, the most complete combustion of the coal component from the additive occurs, which not only reduces the specific fuel consumption for cement production, but also improves its quality, since the mineral composition of coal-bearing rocks after The heat treatment in the refrigerator is represented by quartz, feldspars, mica, and other silicate and aluminosilicate minerals, which positively affect the activity of cement when co-milling with cl nkerom.

Particles of additives in a clinker refrigerator are evenly mixed with clinker, form a dry mixture, ready for grinding. Due to the more intensive cooling of clinker and the thermal activity of the additive, the resulting mixture has a high grinding ability, which increases the performance of grinding units. Thus, the proposed method can be attributed to energy-saving.

The proposed method is as follows. Clinker obtained in a rotary kiln is fed to the cooling grid of the refrigerator. At the same time, a mineral carbon-containing additive is fed to the incandescent clinker stream falling from the furnace at the same time as crushed stone of associated overburden of coal mining or the corresponding granular (lumpy) aluminosilicate carbon-containing industrial waste, for example, fuel waste from Moscow thermal power plants, fractions ranging from 5 to 50 mm, with the content of the coal component in the range from 5 to 15% wt. Moreover, take the additive in an amount of from 5 to 50% wt. clinker. When in contact with a layer of hot clinker, a carbon-containing mineral additive is heated and cracked intensively to form a “fluidized” layer together with cement clinker. At the same time, small coal particles are intensely heated, burned out and carried away by a stream of secondary air into the furnace, where they completely burn out in the sintering zone, and the dusty (ash) part of the additive reacts with the clinker melt, forming an additional amount of clinker.

When moving along the cooling grate in contact with lump particles of the additive, as well as under the influence of jets of cold air supplied under pressure from under the cooling grate, the hot clinker is intensively cooled, and at the outlet of the refrigerator, the clinker temperature is 50-70 ° С.

Upon leaving the refrigerator, the mixture of the additive and clinker is fed to the clinker warehouse and then to the grind to obtain a marketable product - cement.

Examples of the method.

Example 1. On a stream of hot clinker falling from a rotary kiln, a mineral carbon-containing additive is supplied — crushed stone of associated overburden rocks of coal mining, whereby the additive is taken in a fraction of 5-10 mm with a coal content of 15% wt. in the amount of 30% wt. from the content of clinker, and upon leaving the refrigerator, the mixture of cement clinker and additives is milled.

Example 2. The technology of producing cement clinker with mineral additives as in example 1, while the mineral carbon-containing additive is taken in a fraction of 40-50 mm with a coal content of 10% wt. in the amount of 5% wt. from clinker content.

Example 3. The technology of producing cement clinker with mineral additives as in example 1, while the mineral carbon-containing additive is taken in a fraction of 15-20 mm with a coal content of 5% wt. in the amount of 50% wt. from clinker content.

Example 4. The technology for the production of cement clinker with mineral additives as in example 1, while granular (lumpy) aluminosilicate carbon-containing technogenic wastes — fuel wastes of Moscow TPPs — are taken as a mineral additive; the additive is taken in a fraction of 20-30 mm with a coal content of 13% wt. in an amount of 20% wt. from clinker content.

Outside of the parameters for the implementation of the proposed method, the goal is not achieved.

Technical and economic indicators of the proposed method and prototype are shown in the table.

The practical implementation of the proposed technical solution allows us to conclude that the new method effectively increases the mass of clinker without violating the basic technological process in a rotary kiln, by minimizing dust removal from the refrigerator, thermal activation of introduced carbon-containing additives, and preventing a significant reduction in the saturation coefficient clinker with lime and the associated decrease in the quality of cement activity. At the same time, the cost of cement is reduced depending on the volume of the added additive and its cost.

Table No. p / p Indicator Units rev. Technical and economic indicators Examples of the proposed method Prototype one 2 3 four one. Type of mineral carbon-containing additive Crushed stone of associated overburden of coal mining Fuel waste from Moscow CHP Coal ash 2. Additive Characteristic: - fraction mm 5-50 5-50 5-50 20-30 0,045 - content of the coal component % wt. fifteen 10 5 13 10 - count (of clinker content) % wt. thirty 5 fifty twenty fifteen 3. Technical and economic indicators: - dust removal of the additive, from the supplied amount % four 3 5 6 35 - reduction of clinker KN - 0.02 0.01 0,03 0.04 0.07 - fineness of clinker grinding % 0.7 1,5 0.9 0.9 1,2 - cement activity: compressive / bending strength after 28 days of hardening MPa 52.5 / 7.9 59.4 / 8.6 49.1 / 6.7 42.1 / 5.6 38.6 / 5, 1

According to average data, taking into account transport, the cost of natural carbon-containing additives is from 1/15 to 1/5 of the cost of cement. The necessary investments in the additive supply system to the clinker refrigerator are reduced to installing a receiving hopper for storing the additives crushed into crushed stone, a conveyor for continuously feeding the additive into the loading hopper above the refrigerator and a device in the form of an auger for feeding crushed stone to a given point in the refrigerator - a falling clinker stream from the furnace .

When applying 10-20% wt. additives from the volume of clinker to the clinker refrigerator, a small adjustment of the heat balance of the operation of the rotary kiln and the refrigerator is needed, and with an increase in the amount of additive from 20 to 50% wt. clinker requires more extensive adjustment of the fuel supplied to the furnace, the ratios of primary and secondary air to optimize the thermal regime of the units of the technological line.

An approximate decrease in the cost of cement, depending primarily on the cost of the additive, is: when 10% of the additive is supplied by weight of clinker - about 8-10% of the cost of cement, when 20% is supplied - about 13-15% of the cost of cement while maintaining his brand. With the introduction of up to 50% of the additive, the cost of cement of the corresponding brand can decrease by 18-20%. This eliminates the need for the introduction of other mineral additives except gypsum.

Claims (1)

A method for the production of cement clinker with a mineral additive, including burning the raw material mixture in a rotary kiln, feeding the mineral additive into the refrigerator to the obtained hot clinker, cooling, grinding, characterized in that as a mineral additive using crushed stone from overburden of coal mining or coal-containing technogenic waste fractions 5-50 mm with a coal content ranging from 5 to 15 wt.%, The supply of this additive is carried out in an amount of from 5 to 50 wt.% From clinker into its stream falling from the furnace.