DE2637504A1 - Slaking lime with excess water - under shearing, using lime and-or water esp. contaminated with sulphate(s) - Google Patents

Abstract

Lime is slaked with excess water, using a contaminated lime and/or a contaminated slaking water. Contaminants are esp. sulphates. Shearing forces are applied during or after slaking. Process allows use of recycle water. Shearing prevents slaking gravel formation, leading to abrasion of pipes and pumps. Thus, slaking gravel formation, which was increased from 3.49% to 27.2% (w.r.t. CaO) on replacing distilled water by saturated gypsum water, was decreased to 0.56% under shearing generated, during slaking, by a stirred turning at 8000 rpm.

Description

Procedure for slaking lime

The invention relates to a method for slaking lime with excess water, This type of lime quenching is commonly called wet quenching and results in one Ralk hydrate suspension. Impurities present in the water or in the lime such as Chlorides and especially sulphates lead to the build-up of extinguishing particles during extinguishing.

In accordance with the literature (G. Pohl, Zement-Kalk-Gips 8 (1955), pages 393-397, The influence of SO4 ions in extinguishing of white lime) the proportions> 0.09 mm present after deletion are understood.

Other properties of the hydrated lime suspension, such as sediment volume and reactivity become frequent due to such substances that affect the extinction deteriorated in the same way: but there is no clear dependency between Grit formation on the one hand and sediment volume and reactivity on the other.

Because of these disadvantageous properties, especially in extinguishing water existing impurities will be on the part of the ralk manufacturer and the manufacturer from extinguishing systems pointed out again and again, for wet extinguishing of lime if possible to take pure water. This is a requirement that is certainly not being implemented everywhere can be so that more often with more sulphate-containing water inevitably extinguished is, whereby the disadvantages caused by it have to be accepted.

With the increasing importance of environmental protection, one goes more and more about using water in the circuit.

This is the case with flue gas desulphurisation with lime, its end product Gypsum is customary to recycle the gypsum water produced in the process use and then extinguish with sulphate-containing water. The in this species However, the deletion quantities resulting from the deletion lead to severe signs of wear in pipes and pumps.

The object of the present invention is to create a method that allows a contaminated, especially those containing sulfates To use lime for extinguishing and / or with a contaminated, in particular sulfate-containing To extinguish extinguishing water without the disadvantages described above, in particular the increased To show sludge accumulation.

According to the invention, the deletion of the task consists in the deletion with - especially sulphate - contaminated lime or water when using high shear forces.

To carry out the procedure - the application of high shear forces at the time of extinguishing - a high-speed stirrer was provided as a device, the which creates high shear forces. (The circumferential speed which was 0.66 m / s in tests.) It is well known (Tonindustrie-Zeitung 89 (1965), pages 197-202, W. Ohnemüller, The properties of wet mechanically processed Hydrated lime), the lime quenching using high shear forces to be carried out, whereby an improved sediment volume is to be achieved.

About a possible change in the erasure size that forms nothing reported in the aforementioned prior publication. For the examined dry hydrates which were mainly the subject of investigation is even deteriorated because of the Reactivity concluded that no crystals due to the preparation process be destroyed, but before the disorder is eliminated.

Surprisingly, it has been found that using high shear forces the adverse effect of impurities, especially sulfate in lime or in Extinguishing water, which leads to an increased formation of extinguishing powder, can be avoided.

The results of extinguishing attempts listed in Table 1 show this measure according to the invention on Example of a sulfate-containing Extinguishing water.

A fine white lime with a ttJ value of 3.9 min used. This gave when it was extinguished in the Dewar vessel with distilled Water - in accordance with the test procedure of the Federal Association of the German Lime Industry E.V. worksheet 1 (January 1971) - a lime suspension with a sediment volume of 582 ml and a Dry semolina content of 0.73 g; this is 0.49%, based on the amount of lime used from 150 g.

The deletion took place in the same way instead of with distilled Water with a saturated gypsum water, so only a sediment volume of 380 ml was determined and the ash residue increased to 40.8 g = 27.2%.

Now was the extinguishing with gypsum water using high shear forces made, generated with a high speed stirrer at a speed of 8,000 Rpm in a steel beaker resulted in a sediment volume of 600 ml and an amount of quenching gravel found to be 0.84 g = 0.56%.

In other words, roughly the same values were obtained as during the deletion with distilled water, which was carried out at low speeds. From it it can be seen that the influence of the SO4 ions is compensated for during erasure if high shear forces are applied during the erasure.

In the tests, the high shear forces were measured by means of a stirrer generated high speed, the peripheral speed was 0.66 m / s. It lies Of course, within the scope of the invention to take other measures to Lead generation of high shear forces.

It was also examined whether the deletion in the presence of Sulphate ions are produced by subsequent treatment of the hydrated lime suspensions can be reduced using high shear forces.

The results of corresponding tests listed in Table 2 show that that according to the invention also a subsequent application of higher Shear forces lead to a reduction in the amount of sludge. The effect is, however not as pronounced as when the shear forces were applied during quenching. In practice, however, the achievable results may be sufficient in some cases so that then only one post-treatment device in a conventional manner produced milk of lime is required.

Examples of impurities other than sulfates are given in the table 3 Test results for the extinguishing with and without the addition of calcium chloride are given. It can be seen that the influence of the chloride ions in the formation of extinguishing particles and Sediment volume is less pronounced than the influence of sulfate ions. At a Concentration of 10 g Cl / liter (= 0.28 equivalents / liter) becomes 5.74 g of the sludge (= 3.83%), while saturated gypsum water 0.03 equivalents / liter 40.8 g = 27.2% extinguishing substance resulted, however, if the extinguishing with chloride-containing water is carried out using high shear forces, the values obtained are approximately the same as with normal deletion with distilled water. It shows So also with the chloride ions, that the negative influence in particular on the formation of erosion particles during erasure through the application of high shear forces during the The deletion process is to be compensated.

Table 1 Extinguishing with and without sulphate extinguishing vessel Dewar Dewar steel beaker Speed rpm 250 250 8,000 extinguishing water - distilled saturated saturated H20 Gypsum water Gypsum water Amount of lime g 150 150 150 Amount of extinguishing water ml 600 600 600 tu min 3.9 lo.3 sediment volume ml 582 380 600 extinguishing size o, o9 mm g o, 73 40.8 o, 84 Tabel 2 Extinguishing with gypsum water Comparison between extinguishing with the application of high shear forces during deletion and a normal deletion with subsequent application of higher Shear forces Application of shear forces during extinguishing after extinguishing Steel bucket Dewar speed when extinguishing (rpm) 8 000 250 speed after extinguishing (Rpm) - 8 000 vessel for post-treatment - steel beaker of extinguishing water saturated Gypsum water saturated gypsum water sediment volume (ml) 600 560 extinguishing substance 0.09 mm (g) 0.84 2.52 Table 3 Extinguishing with and without the addition of chloride Dewar Dewar Dewar steel beaker speed rpm 250 250 250 8000 CaCl2 water Extinguishing water distilled CaCl2- CaCl2-water water water chloride concentration g C @ / @ @ 1 10 10 in the extinguishing water g Cl / l O 1 10 10 amount of lime g 150 150 150 150 amount of extinguishing water ml 600 6000 600 600 tU min 3.9 2.6 1.15 -Sediment volume ml 582 580 440 585 sludge g o.73 1.81 5.74 l, oo

Claims (3)

Claims 1. Method of slaking lime with excess water, with a contaminated Lime and / or contaminated extinguishing water is used and the impurities consist in particular of sulfates, characterized in that during the extinguishing process or then high shear forces are applied. 2. Method according to Claim 1, characterized in that the shear forces can be generated by means of a stirrer, the peripheral speed of which is> 0.3 m / s amounts to. 3. Method according to Claim 1, characterized in that during deletion Hydrated lime suspension resulting from contaminated excess water has high shear forces is exposed.