SU1206244A1 - Method of preparing lime - Google Patents

Description

The invention relates to the production of calcium lime with delayed hydration periods from soft varieties of carbonate rocks used to make products from dense silicate and cellular concrete and living limestone.

The purpose of the invention is to provide a slower rate of hydration.

The chemical content of carbonate rocks processed by the additive is given in Table 1 for the example of the Cretaceous rocks of the Brno and Belgorod deposits.

Sodium tripolyphosphate Noj-Pj and sodium carbonate Na CO can be used as a technical product with a useful substance content of 91.4 and 95.2%, respectively.

Electron microscopic studies of the structure of lime obtained by the proposed method with magnification of 15,000 times show that at calcination temperatures of 850–980 s, the structure of lime is composed of calcium oxide crystals ranging in size from 0.003 to 2.5 µm, having an oval and round shape , and relics of calcite. In the presence of an added additive, eutectic melts and complex compounds with calcium oxide, calcite and impurities are formed on the surface of calcium oxide grains, which, due to the even distribution of the added additive, are located on the surface of calcium oxide grains in the form of films with a low degree of penetration into the main phase. Such films in lime block the access of water molecules to the surface of calcium oxide and thereby slow down the quenching reaction.

With an increase in firing temperature (above 1000 ° C), the neoplasms rapidly decompose, migrate and accumulate in the dislocation growth stages of calcium oxide crystals, covering considerably smaller portions of the surface of the lime grains and providing good conditions for their interaction with water.

The effect of hydration retardation in lime is observed both under the effect of TFPN and under the influence of CS, but in the case of using a mixture of these additives, the effect is more intense. The total content of additives in

the chalk mass can be adjusted over a wide range from 0.05 to 1.2 percent or more, depending on the type of chalk and the desired retardation effect.

The preparation of lime according to the proposed method is carried out using known equipment: milling and throwing mills, hydrofol, talkers and other units for wet grinding of chalk, pumps for transportation and basins for storing chalky sludge, feeders for dosing grills and other kilns for firing and drying. In addition, aggregates are additionally used to prepare additive solutions, including aggregates for dosing, dissolving them in water, and dosing a solution of the additive to carbonate rock during grinding.

The method of preparation of lime is carried out as follows.

Extraction of chalk in the quarry is directed to a unit for wet grinding and spreading (mash, milling-throwing mill, hydrofol, or other aggregates). During the grinding and melting of chalk, the proposed additive is introduced with water. The prepared slurry is sent to a pool for reception and storage. The dosage of the additive and water is based on the desired effect on slowing down the hydration of lime and the desired moisture of the working chalky sludge. Drying, granulation and roasting of chalky sludge can be carried out in one heat unit, for example in a rotary kiln, or in separate units for granulating and drying (in a spray dryer) and in fluidized bed furnaces or

-turning furnaces - for firing.

Under laboratory conditions, the proposed method was tested. The compositions and test results are given in table 2.

From the data of Table 2 it can be seen that during calcining at low temperatures, before complete or partial decarbonization of chalk, lime with an activity of 72.0-93.5% is formed with different hydration periods, depending on the type of chalk, calcination temperature, amount of added additive and ratio in her components. With

In this case, the size of lime crystals is 0.003-1.8 µm in the whole of the sample}:, measured at these temperatures. By reducing the firing temperature from 980 to the duration of quenching at 11-31% compared with lime samples obtained at 980 ° C. At the same firing temperature of chalk with a high degree of contamination

a piece of chalk

Oxides content, May. %

SiO lAIiOj JMgO j SOj ppt Amount

Belgorod

Brno

2.17 0.81 0.32 52.96 0.29 0.01 0.36 0.80 41.95 99.60 1.60 0.54 0.30 53.58 0.10 - 0.20 0 , 05 43.37 99.96

Belgorod chalk

0.05

1.0

2.0

1206244,

due to natural impurities (Belgorod chalk), lime is obtained with longer hydration periods compared to lime made from chalk with a small

degree of contamination (chalk chalk In all cases, the quality of the resulting finished product satisfies the requirements for all indications of 1 lm.

Table 1

T a in l and c J

77.0 2.5 81.0

3.0

89.0

12.0 16.5 18.0

84.5 84.0 83.0

1.0 80.0

10,082,09,0

15,083,013,0

16,084,014,0

11,082,09,0

15.382.5. 13.5

17.083.014.5

9.5 14.0 15.0

0.5

88.0 86.0 85.0

88.0 85.0 83.5

89.0 86.0 84.0

92, .0

72fO

1.5 77.0

1.0

92.0

Editor I. Derbak

Compiled by A. Kulabukhova

Tehred I.Astalosh Corrector M.Maksimishinets

8641/23 Circulation - Subscription

VNIIPI USSR State Committee for Inventions and Discoveries 4/5, Moscow, Zh-35, Raushsk nab. 113035

Branch ShSh Patent, Uzhgorod, st. Project, 4

Claims (1)

METHOD FOR PREPARING LIME by grinding carbonate rock, mixing it with an additive, granulating and firing, characterized in that, in order to slow down the hydration rate, a mixture of sodium tripolyphosphate with sodium carbonate is introduced in the ratio 1: 4-1: 5, in the amount of 0.051.2X by weight of carbonate rock, and firing is carried out at 850-980 ° C. SS • 1206244