CS230487B1 - A method of controlling the hydration reactivity of lime in industrial firing - Google Patents

Abstract

The invention falls within the field of industrial lime production. It addresses a method of regulating the hydration reactivity of lime during industrial calcination. The procedure is that lime is calcined in an atmosphere with a controlled CO2 and/or H2O tension in the range of 0.03 to 75% by volume for CO2 and H2O at the inlet to the calcination zone, provided by the type and composition of the fuel and/or flue gas recirculation using air or a mixture of air and oxygen. When using solid fuel, the controlled CO2 tension is 1.5 to 30% by volume. When using gaseous and liquid fuel, the controlled CO2 tension is 9.5 to 75% by volume and H2O is 0.03 to 18% by volume. When using gaseous fuel, the controlled CO2 tension is 9.03 to 15% by volume and H2O is 5 to 70% by volume.

Description

The invention relates to a method for controlling the hydration reactivity of lime in industrial firing

Industrial lime has been produced so far in shaft kilns, rotary, fluidized, circular and in shaft kilns in a thin phase, heated by combustion of natural gas, generator gas, heavy oil, coal or coke with air. It is known that the hydration reactivity of the lime thus obtained - the hardness of the firing depends on the type of limestone, the temperature course in the calcining zone of the kilns and the time of lime residence at the temperature. in practice this means that the reactivity of the product is determined by the location of the limestone quarry, the type of fuel, the type of kiln aggregate, the consumption and performance standards. Industrial lime consumers demand lime of various, sometimes regulated quality standards, which often do not meet production standards®

The above drawbacks are eliminated in the method of controlling the hydration reactivity of lime in industrial firing according to the invention, which is based on the fact that the lime is fired in an atmosphere with a controlled tension of CO ₂ and / or HgO in the range of 0.03

- 2 230 487 to 75% vol. Of CO ₂ and also H ₂ O at the inlet to the calcining zone, provided by the type and composition of the fuel and / or flue gas re-recirculation using air or air / oxygen mixture. CO ₂ is 1.5 to 30% by volume using solid fuel, violet may be such that the regulated CO ₂ pressure is 9.5 to 75% by volume and H ₂ 0 is 0.03 to 18% by volume when using gaseous fuel and liquid fuels, such as generator, gas, natural gas, technical carbon monoxide, Fischer-ovropsch synthesis gas and liquid fuels, or the regulated CO ₂ pressure is 0.03 to 15% by volume and HgO is 5 to 75 # by volume when used gaseous fuel, such as ammonia synthesis gas, nitrogen / hydrogen mixture in different volume ratios, technical hydrogen · Product - lime of different hydration reactivity is obtained by influencing the composition of the firing atmosphere in the decomposition zone of the furnace, namely the volume nitrogen, oxygen and mainly carbon dioxide and water vapor.

In the process according to the invention, the production facilities are operated in such a way that the choice of fuel, air or air / oxygen mixture in the combustion medium, its excess over the stoichiometric ratio to fuel and flue gas recirculation guarantee the atmosphere composition upon entering the calcining zone at a given temperature of the calcination zone, the carbon dioxide and water contents corresponded to the desired reactivity of the product. The carbon dioxide tension in the decomposition zone of the furnaces has a particularly significant effect on the hydration reactivity of the lime. High reactivity is characterized by lime burned in an atmosphere with low CO ₂ pressure and high water vapor pressure. hard lime is obtained by firing in an atmosphere containing carbon dioxide in a volume fraction above 24% ·

For the production of lime with very low hydration reactivity, the regulated CO ₂ tension is 1.5 to 30% by volume and a solid fuel combusted with a mixture of oxygen and air or air is used.

230 407

Possible recirculation of part of the flue gases below the calcination zone. For the production of lime of medium hydration reactivity, the CO 2 tension is 9.5-75% by volume and E ^O 0.03-0.03% by volume and natural gas, generator gas, water gas, Fischer-Tropsch synthesis gas or air-burned heavy oil are used. enriched in oxygen, air, or only part of the possible recirculation of flue gas below the calcining zone and the level of Horakov · for lime hydration j extremely high reactivity of the controlled tension cog from 0.03 to 15% by volume of H ₂ 0 and is 5 to 75% by volume and the fuel used is ammonia synthesis gas, a mixture of hydrogen and nitrogen in other mixing ratios, hydrogen, or air gas combusted only with air, possibly recirculating part of the flue gases below the decomposition zone or to the burner level ·

FROM

The advantage of industrial firing control according to the invention is that it is possible to control the hydration reaction of the lime - the hardness of the lime at a constant temperature in the positive zone and without changing the residence time of the material in the furnace. in the vicinity of atmospheric pressure, the morphology of the product, i.e. the size of the CaO particles, their habitus, the total pore volume, the pore size and distribution, and the specific surface area can be significantly influenced. These changes also result in a change in the chemical properties of lime, namely their chemical reactions in different reactions.

FROM

The subject of the invention is illustrated by the conversion examples ·

Example 1

Limestone of grain size 0,8 to 2,0 mm from the locality Vajarská weighing 8 g was fired in a vertical erusulite laboratory furnace, automatically regulated to a temperature of 1 100 ° 6. Limestone contained in the corundum tube was blown through an atmosphere containing 35% by volume carbon dioxide and 65% by volume du4

230 487 sika v příoku 2 l.min * ¹ . The limestone was fired to moderate and after cooling the sample in the desiccator, the hydration reactivity was determined on a Directochrom D apparatus according to the following procedure.

2.00 g of lime were poured into 200 ml of distilled water heated to 30 ° C by stirring with a magnetic stirrer. The temperature increase aa registered by a thermocouple on a connected TZ 21-8 recorder _{with a} 100% displacement response to the released heat of 166.9%.

Example 2

The procedure was as in Example 1 except that the ataoefera contained 25 vol.% CO ₂ and 75 # vol. Mg. The hydration reactivity of the obtained lime, as determined by the method described in Example 1, is shown in Figure 1, curve 2. hydration reactivity ·

Example 3

The procedure was as in Example 1 except that the atmosphere contained 15% by volume of CO ₂ and 85% by volume of N _2. The hydration reactivity of the lime obtained, determined by the method described in Example 1, is shown in FIG. 1, curve 3. Lime of moderate hydration reactivity was prepared.

Example 4

The procedure was as in Example 1 except that the atmosphere contained 10% by volume of CO ₂ and 90% by volume of N ₂ · Hydration reactivity of the obtained lime * determined by the method described in Example 1 is shown in Fig. 1, curve 4 medium hydration reactivity.

Example <5

230 487

The procedure was as in Example 1, except that the atmosphere contained 5% by volume of CO ₂ and 95% by volume of N _2. The hydration reactivity of the lime so obtained is high and the hydration curve is shown in FIG. 1, curve 5.

Example 6

The procedure was as in Example 1 except that the atmosphere contained a / 0% CO ₂ , b / 100% HgO. Lime of high hydration reactivity was obtained. The hydration curve is shown in FIG. 1, curve 6.

EXAMPLE 7 Limestone of grain size 0.3-2.0 mm from the Vajarská site in batch 8 S was fired in a horizontal silsit furnace with automatic temperature control at 1200 ° C on an ozone boat. The atmosphere which is purged oven contained 100% by volume of CO ^, flow rate of 2 L · min ^1, the firing time of 15 minutes. Lime of low hydration reactivity was obtained, the curve shown in FIG. 2, curve 1.

Example 8

The procedure was as in Example 7 except that the atmosphere was N ₂ containing 0.03% HgO by volume. Lime of moderate hydration reactivity was obtained, the hydration curve is shown in FIG. 2, curve 2.

Example 9

The procedure was as in Example 7 except that the atmosphere contained 100% H 2 O by volume. Lime of high hydration reactivity was obtained, the hydration curve is shown in FIG. 2, curve 3.

Claims (2)

OBJECT OF THE INVENTION 230 487 Process for controlling the hydration reactivity of lime in industrial firing, characterized in that the lime is fired in an atmosphere with a controlled carbon dioxide and / or water vapor pressure in the range of 0.03 to 75% by volume for carbon dioxide and water vapor at the inlet to the calcining zone, provided by the type and composition of the fuel and / or recirculation of the flue gas using air or a mixture of air and oxygen. ³ 2 ₃ the control method of the hydration reactivity of Industrial box according to claim 1, characterized in that the controlled tension of carbon dioxide in the combustion medium or in a mixture with recycled is up to 35% by volume and / or oxygen tension 22-66% by volume using a conventional solid, liquid and gaseous and synthetic fuels such as generator gas, carbonizing gas, Eischer-Tropsch synthesis gas, water gas, ammonia synthesis gas and other mixtures of carbon monoxide, hydrogen, nitrogen and hydrocarbon © v.