SU763288A1 - Method of dust utilization - Google Patents

Description

one

The invention relates to the field of production in living material, mainly to methods for returning dust to a rotary kiln at operating cement plants.

In modern cement plants, dust collected by electrostatic precipitators is returned to the process, either in conjunction with the raw mix, or JQ leaked into the burning zone of the rotary kiln.

There is a known method of returning dust to a cement-burning kiln, which includes trapping, dust granulation and giving granules of 3–30 mm in size with a moisture content of 10–25% into the kiln together with the raw material mixture ij.

The disadvantages of this method are recirculation of alkali contained in dust, 20 low speed of the clinker formation process and quality of cement.

The closest technical solution to the invention is a method of disposing of dust collected from waste gas of a rotary kiln, including sedimentation, transportation and supply of dust to the burning zone 2.

The disadvantages of the known method of disposal of dust - low speed O7 30

clinker formation and reduced cement strength.

The purpose of the invention is to intensify the process of clinker formation and increase the strength of cement.

The goal is achieved by the fact that in the method of disposing of the dust collected from the exhaust gases of the incinerating furnace, including sedimentation, transportation and supply of dust to the clinker burning zone, the dust is fed with the additive before it enters the burning zone with an additive. melting 900-1300 C.

In addition, either magnesium chloride or sodium chloride or sodium sulfate is used as additives, and the additives are added in an amount of 3-10% by weight.

When dust is supplied to the burning zone together with the components forming a mixture with it, which melts at a temperature below, the material undergoes intensive melting in a gaseous stream. As a result of the melt droplets caused by the surface tension of the liquid phases in contact with the flow, there is a rapid increase in the size of the moving droplets, which causes them to fall out of the gas at Tt5Ka at the end of the burning zone at 13001350s. Due to the low temperatures and the reaction time (10-15 minutes), the additive does not have time to fully react with the recovery of the clinker eren. The resulting clinker is characterized by an uneven composition and an increased content of free calcium oxide, which causes low strength characteristics of the cement produced from it. introducing dust or a mixture based on it, melting at a higher temperature, only partial melting and dispersion of the material occurs in the burning zone, and the main part (80-90%) gas flow into the low-temperature zones (less than the furnace and is deposited in them in the solid state. At the same time, the homogeneity of the system is not reached, because the dust, due to its high fluidity, is stirred across the surface of the calcined material. Calcium oxide present in the dust recrystallizes The formation of dense conglomerates of 100-200 microns in size, which slowly dissolve in the clinker melt formed in the burning zone. As a result, the speed of the clinker production process is reduced, which causes a reduced productivity of the drying furnace. Cro

In addition, the smallest particles of dust do not have time to be removed from the gas stream in the furnace and are deposited in the roaster dust collectors, which significantly increases the dust from the furnace and the heat consumption for clinker burning. If the mixture of dusts with an additive melts at 900–1300 s, then the bulk of the melt droplets formed falls on the clinker in the area from the beginning (to the middle (1450s) of the firing zone. At the same time, the melt gets to the surface of the material, which migrates deep into grains over their capallary system. As a result, the composition of clinker granules is rapidly averaged, while calcium oxide does not have time to recrystallize and instantly reacts to the formation of clinkers. Allows a 10–15% increase in the productivity of rotary kilns, and the formation of a clinker of uniform composition results in high-strength cement. The method is as follows. Based on limestone, clay and butts, a porflandtsement raw material mixture is prepared by using wet grinding. and the charge held in the table., 1.

3.45 0.950.37 53.01 0.450.1241.68

65.34 15.294.46 2.07 2.352.557.02

10.58 2.8672.97 7.50 -7.50

13.58 3,542.75 41.36 2.320.2534.89

After drying at a residual moisture content of less than 0.1%, the mixture is bred at a specific pressing pressure of 300 kgf / cm. The resulting briquettes with a diameter and height of 20 mm are heat treated according to the mode simulating clinker burning in rotary kilns: heating at a rate of 400 deg / h to 1: 450 ° C, isothermal holding for 15 minutes at 1450 ° C, cooling in the range of 1450-1300 s for 15 min, followed by quenching. Dust in the amount of 10% of the weight of the briquettes, mixed with the additive, is applied to the surface of the calcined clinker at different temperatures, depending on the melting temperature of the added mixture. For its preparation, dust composition, wt.%:

Sao38,32

SiOa11.56

A, aO, 3.22

Fe O-i2,17

MgO2.35

, 7

Na, 0 + K2.0 10.90

PPP. 25.78 and additives: magnesium chloride, sodium chloride, sodium sulfate.

The kinetics of the clinker formation process is estimated from the residual content of free Klyca oxide in the synthesized klinkoax.

The results of determining the nature of the influence of the melting point of the mixture

1360

100 (prototype)

magnesium chloride

1300

3 6 1100

900

ten

90

15

850

85

sodium chloride

1100

3 10 900

sodium sulfate

1100

3

900

ten

870

20

An analysis of the results presented in the table shows that, in the case of additive to granules, the compression of a mixed clinker mixture, melting in the range of 900-1300 ° C and containing dust with various additives, is observed in i-iO and the high rate of the clinker-forming process, which causes the minimum content of free oxide in the specs. Cements obtained from these clinkers are characterized by increased-65

dust with an additive (and, consequently, the amount of dust added to the raw material charge) for completeness of the clinker formation process, as well as cement strength after 28 days of hardening in air-wet conditions are given in Table. 2

Table 2

4.1

1000

350

2.0

420,470 0.7

2.7

415

365

6.2

395

1.2 380 3.4

418

1.1 3.1 400 5.8 370

30–120 kgf / cm compressive strength after 28 days of hardening. The best results were obtained for a mixture melting at 900-1300 ° C and consisting of dust and 3-10% by weight of magnesium chloride.

Thus, the use of the proposed method of dust utilization makes it possible to intensify the process of clinker formation and increase the strength

cement compared to the known method.

The application of the proposed method does not require significant capital expenditures, which makes it possible to recommend it in existing cement plants.

As a result of the intensification of the processes of clinker formation, which causes a reduced content of free calcium oxide in the clinkers (Table 2), the duration of the synthesis of clinkers decreases by 10–15%. The reduction in the residence time of the material in the sintering zone allows for a 1s load of its material and, thus, the productivity of the rotary kiln.

Claims (3)

1. Method of utilization of dust collected from rotary junction furnace exhaust gases, including deposition, transportation and supply of dust to the burning zone clinker, characterized in that, in order to intensify the process of clinker formation and improve the strength of cement, the dust is first mixed with the additive, melting with a melting point of 900-1300 C, before being fed into the burning zone. 2. The method according to claim 1, characterized in that either magnesium chloride, or sodium chloride, or sodium sulfate is used as additives. 3. Method of iopp. 1 and 2, characterized in that the additives are introduced in an amount of 3-10% by weight. 5 Sources of information taken into account during the examination 1. The patent of Japan 50-20090, cl. 22/3 / A9, publ. 1975. 2. Chev V.A. Advantages of blowing dust into the furnace sintering zone. Cement, B 3, 1973, p. 12 and 13.