DE2349087C2 - Process for the production of hydrated lime - Google Patents

Description

This process, which has been used industrially for a long time, always produces residues, the so-called "grits". These consist essentially of inextinguishable components such as CaCO ₃ , of not extinguished quicklime CaO or, in particular, of agglomerates and secondary particles of calcium hydroxide Ca (OH) ₂ , the greater the proportion of soft quicklime in the initial lime (cf. »Series of publications of the Federal Association of the German Lime Industry ", Cologne 1973, issue 11, pp. 31 to 49). In industry as well as in the following, grit is understood to mean, in particular, the sieve residue on the DIN sieve 0.09 mm. The grits obtained from the wet slaking of harder burnt lime consist mainly of silicates, aluminates, carbonates, etc. These compounds cannot be converted into slaked lime by a normal slaking process.

In recent years, the lime industry has been increasing in line with customer demand Dimensions of soft quicklime, d. H. a quicklime with high reactivity. When deleting this soft quick lime, the amount of semolina is particularly high and is sometimes over 50%, based on the quicklime used. From the mass balance it can be seen that this meal consist predominantly of calcium hydroxide, as the theoretical possibility that it is undeleted Lime can deal, with soft quicklime not applicable.

In the production of milk of lime is already suggested been that the residues that occur when the raw milk of lime goes through a first Separator incurred, a post-extinguishing and the post-extinguished residues fed to a second separator the milk of lime leaving the individual separators in a next processing stage is forwarded. This process ensures that the lime is completely extracted during production milk of lime, but is unsuitable for the production of dry hydrated lime. So far have been therefore the semolina separated by a visual process and then ground and then extinguished again; however, the hydrate obtained is of inferior quality.

The object of the invention is to reduce the amount of semolina when slaking lime decrease without affecting the severed gneiss especially need to be processed.

Surprisingly, it was found that a significant reduction in the amount of semolina can be achieved If the resulting hydrated lime is sighted, the grain size of a residue on DIN sieve 0.09 mm corresponding hydrated lime grits separated from the fine material and a part of these gneisses together with fresh quicklime the extinguisher is again given up.

The amount of hydrated lime semolina added together with the quicklime still to be removed is preferably 10 to 50 percent by weight, based on the quicklime.

The amount of gneiss that then arises is of course larger than the one without the inventive Partial repatriation would receive. However, if you take the amount of gneiss given to the extinguishing device from, the remaining "net gneiss" compared to the zero attempt are surprisingly significantly reduced. Table 1 shows the results of laboratory extinguishing operations.

Table 1

Semolina attack N etK. ₌ ;;; ßc
% Semolina addition
% Overall size
% 39.5 O 39.5 31.1 10 41.1 28.9 20th 48.9 23.5 30th 53.5 21.9 40 61.9 16.8 50 66.8

The Pro ^ ent information. relate to a quick lime task of 100 percent by weight.

It can be seen that the net semolina accumulation of 39.5 can be reduced to 16.8% if the deletion is carried out with a 50% addition of grits. In each case 200 g of a soft quicklime comminuted to 0 to 5 mm with a U-value of 41 in an insulated extinguishing vessel according to the small extinguishing method according to Din 1060 with the addition of 120 g of water are extinguished each time. The U value is the percentage conversion per minute in the reaction of To understand quicklime with water, which is a measure of the degree of burning, see E. Schiele and L. W. B e r e η s, Kalk, 1st edition, Verlag Stahl and Eisen, Düsseldorf 1972, p. 544 ff.

The quicklime used had the following sieve analysis and composition:

Sieve analysis
of the task lime 4.0% Chemical analysis 4 to 5 mm 19.9% CaO 95.68% 3 to 4 mm 23.9% MgO 1.69% 2 to 3 mm 17.6% SiO ₈ 0.82% 1 to 2 mm 11.1% Al ₂ O ₃ 0.26% 0.5 to 1 mm 14.2% Fe ₂ O ₃ 0.32% 0.09 to 0.5 mm 9.3% Mn ₃ O ₄ 0.06% 0.09 mm SO ₃ 0.04% Loss on ignition 1.13% CO _a 0.69%

The dependency of the net amount of semolina as well as that of the total amount of semolina on that when discharging The amount of semolina added is shown in FIG.

Since the total amount of weight increases with increasing semolina

increases, the extinguishing device and sifter are more heavily loaded. To make statements about this received, the mass balances were drawn up. Dice are shown in Table 2.

Feed amount of brandy 100
0 Tabel 2 100
20th 100
30th 100
40 100
50 IC lime
Semolina task 100 120 130 140 150 G. A Total load 100
10 Total extinguishing goods 129 110 149 159 169 ] 79 H (Hydrate) 89.5 101.1 105.5 109.1 111.5 Finished product (fine product) 39.5 139 47.9 53.5 60.0 67.5 F. Overall size 39.5 95.7 27.9 23.5 20.0 17.5 G Net size 43.3 NG. 33.3

The associated process control scheme shows F i g. 2, from which the names for the table! and their sources can be found (L = Loicher, S = classifier).

From the table it can be seen that ζ. Β. with a semolina load of 30% the total extinguishing material (i.e. the amount to be given to the classifier)

IOD

129

23.2%

increases.
The amount of finished product is around

₁₀₀ . 005.5- ^ 9.5)

89.5 '"

elevated

and the amount of semolina (net) around

100-

39.5

= 40.5%

decreased.

The same effect is normal with the method according to the invention when deleting a quick lime, e.g. B. with a U-value of 5.6% conversion / minute is achieved. Table 3 contains the results corresponding deletion attempts.

Table 3

Semolina addition

0
30th

Semolina attack
Overall size Net size

5.52
22.54

5.52
-7.46

the recirculation of semolina reduces the amount of new semolina, d. that is, that they led back Particles must be subject to further fragmentation during the extinguishing process.

According to a further embodiment of the invention, grit that is lost during deletion of a lime product can also be abandoned when another lime product is discharged.

Another laboratory test produced the following results:

^L.

200 g quicklime, 96.22% CaO, 0.8% MgO. 0.84% SiO ₂ , 0.31% Al ₂ O ₃ , 1.54% loss on ignition, 120 g of water were mixed as a Nuil test (without the addition of semolina) and I ¹ /, hours were left to their own devices.

35

40 2.

200 g quicklime,
120 g water,

60 g of semolina were treated accordingly as experiment I.

2a.

The zero test showed an exothermic reaction (vapor development) when mixing, the same the attempt; Semolina alone remains without a reaction when qualitatively drawing in water, which proves that slaked lime is present.

3.

After the specified time, the test products stored in metal containers were removed, weighed and ever

3 a.

100 g in an air jet sieve
4 '/ j min treated.

DlN 0.09 during

The amount of semolina resulting from the Nuilversuch is 5.52% so small that measures to reduce it are not strictly necessary. Are the quicklime to be extinguished z. B. 30% semolina one prior deletion added, the result is 22.54% total size, while the amount of net size assumes a negative value (- 7.46%). This result is only apparently surprising and due to the fact that more semolina was added to the feed material than in the zero attempt would arise. But it follows from this that 4.

Trial 0 'total yield ...
Trial l / total yield ...

5.

Semolina at 0 (100 g) = 45.11 g,
Semolina at I (100 g) -49.66 g,

based on the yield of

0 = 255.93 g = 115.5 g = 57.75%,

1 == 314.85 g = 156.5 g -78.25%.

255.93 g
314.85 g

This is a significant reduction in the formation of semolina and the inclusion of the added Semolina detected in sales (difference in percentages).

From the following analysis of extinguishing debris incurred from another zero attempt, which was carried out during Use of soft quicklime have arisen, it can be seen that the resulting product is in primarily calcium hydroxide:

CaO 72.31%

MgO 1.24%

SiO ₂ 1.16%

Al ₂ O ₃ 0.18%

Fe ₂ O ₃ 0.15%

Mn ₃ O ₄ 0.04%

SO ₃ 0.05%

Loss on ignition 24.87%

2.08%

H ₂ O free 0.49%

Converted stoichiometrically:

Ca (OH) ₂ 91.63%

CaCO ₃ 4.73%

CaSO ₄ -2H ₂ O 0.11%

2CaO-SiO ₂ )

CaO free V 3.16%

SiO ₂ (quartz) J.

MgO 1.24 ° /

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. Process for the production of hydrated lime by slaking quicklime, thereby characterized in that the resulting hydrated lime is sighted, while the grain size a residue on DIN sieve 0.09 mm corresponding hydrated lime grits separated from the fine material and part of this meal together with fresh quicklime again to the extinguisher is abandoned. 2. The method according to claim 1, characterized. that the abandoned hydrated lime semolina amount together with the fresh quicklime 10 to 50 percent by weight, based on the fresh quicklime. 3. The method according to claim 1, characterized in that hydrated lime grits are incurred a lime product in the deletion, abandoned when deleting a lime product other _M.