DE2142114C3 - Process for the production of practically chloride-free K2 SO4 - Google Patents

Description

as oil% chloride in several stages and the cover liquor is used for the measure (11 and the practically chloride-free K ₂ SO _{4 is} dried

(4) The NH _{3 is} removed from the K ₂ SO ₄ mother liquor and fed back into the process, while the practically NH ₃ -free KoSO ₄ mother liquor evaporates up to 75% of the water and that in the course of the ^{Cooling: l3} cooling of this mother liquor, NH ₄ Cl from the mother liquor almost free of intergrowth

^dd 114

The German patent specification 9 46 434 relates to a process ;; ur production of KoSO ₁ and NH ₄ CI by double: conversion of KCI and (NH ₄ ) ₂ SO ₄ . This process works in such a way that gaseous NH _{11 is} introduced into the reaction liquor until it is saturated, further (NH ₄ ) ₂ SO _{4 being} added for complete conversion of the KCI. The starting materials KCI and (NH ^) ₃ SO ₄ and, at the same time, the resulting K ₂ SO ₄ are therefore present in the suspension. It is noted in this patent that by the repeated addition of (NH _4), SO ₄ to the mother liquor and due to the entrance into the mixed crystal has a molar ratio i (NIH ₄₎ "SO _4.:. (KCI) = 53:47

is required.

The precipitated K ₂ SO ₄ has the following composition

Settlement:

K ₂ SO ₄ 92.1%

<NH ₄ ) oSO ₄ 7.35%

KCI 0.55%

_{this method is generated as 0 a} K ₂ SQ ₄ ,

which is evidently strongly due to mixed crystals of K ₂ SO ₄

and (NH ₄ ) ₂ SO _{4 is} contaminated by leaching

_not be able to flock ^{duck 2} _rnt. That after this

drive received K ₂ SO ₄ contains a maximum of 49.2 to

Weight percent K "O or 91 to 93 weight

^ _Q ^p _{High Concentrations} are not to

reach.

As a coupled product is from the ammoniaka _metallic ^g ^ _Lös comparable _by evaporation to dryness * * _fo | _gender ^V _Zusamme he nsetzung ^zeu S ^t:

NH ₄ Cl 98.8%

(NH ₄ ) ₂ SO ₄ 0.7%

K ₂ SO ₄ 0.5%

From the patent it can be seen that for

2. The method according to claim 1, characterized in that the suspension of technical KCI and cover liquor has a solids content of 30 to 60 percent by weight.

3. The method according to claim 1, characterized in that the aqueous solution of technical (NH ₄ ) ₂ SO _{4 has} a concentration of 30 to 44 percent by weight.

4. The method according to claim 1, characterized in that in stage 4 the practically NH ₃ -free mother liquor is removed by evaporation from 65 to 70 percent by weight of water.

5. The method according to claim 1, characterized in that in stage 5, the adhered solution of the separated NH ₄ Cl on a filter or a centrifuge with approximately 20 to 40 Gewichtsproj.ent water, based on the NH ₄ C1-amount, and the displaced Cover water with the rpaktisch NH ₃ -fre: ien KoSOj mother liquor of stage 4 is combined.

a process for the production of alkali sulfate from wet gypsum, whereby initially by implementing the ilfiiMNH ^ COLösungiNH ^ SO

Calcium SulphateMNH ^ oCagi ^! is produced. The (NH ₄ ) ₂ SO ₄ solution is stirred in stirred vessels with KCi and methanol until it is practically complete. The precipitated K ₂ SO ₄ is washed out, with a diluted

Methanol solution is produced. From the NH ₄ Cl aqueous methanol solution containing the methanol is recovered by distillation to obtain a hot NH ₄ Cl solution resulted.

The use of methanol to separate the

.55 NH ₄ C1 solution has the disadvantage that considerable amounts of an organic solvent have to be used in order to achieve complete conversion of the KCl to K ₂ SO ₄ . The recovery of the methanol by evaporation means an additional

Liehe process stage, which also leads to losses of this solvent.

No degrees of purity of the K ₂ SO ₄ and NII ₁ CI produced are disclosed for this process. The description shows that NaCI-free KCI is a

has been set. According to the state of the art, it must be assumed that only the same degree of purity as is achieved by the method of German patent specification 9 46 434.

There has now been a process for the production of practically chloride-free K ₂ SO ₄ and pure NH ₄ Cl from KCl and (NH ₄ ) _a SO ,, by continuously stirring in a concentrated to saturated solution of technical (NH ₄ ) .. SO ₄ with a small upper weft from about 5 to 10 mole percent in an aqueous slurrying of KCl and reaction with the KCI under crystallization of the main amount of K ₂ SO _4, followed by introduction of NH ₃ to the practical saturation while maintaining a temperature of 15 to 4O ⁰ C under Crystallization of the remaining amount of K ₂ SO ₄ and separation of the K ₂ SO ₄ from the mother liquor found.

A characteristic of this process is that

»5

(1) for mashing the technical grade KCl to a suspension which is used from the K ₂ SO ₄ cleaning of the cover liquor recycled;

(2) in the reaction of KCl and (NH ₄ ), SO ₄ in the ammonia-containing mother liquor, the ammonium chloride concentration is below 18 percent by weight NH ₄ Cl;

(3) the separated K ₂ SO ₄ covered with water up to a content of more than 51 % K ₂ O and less than 0.1% chloride and the cover liquor »5 used for measure (I) and the practically chloride-free K ₂ SO _{4 is} dried;

(4) the NH _{3 is} driven off from the K ₂ SO ₄ mother liquor and fed back into the process, while _{the water evaporates up to about 75% from the practically NH 3} -free K ₂ SO ₄ mother liquor, and that in the course of cooling _{NH 4} Cl which is obtained from this mother liquor almost free of intergrowths is separated off from the mother liquor and

(5) the NH ₄ Cl is purified by displacing the adhering solution with water to give a product with a purity of over 99% and dried.

The suspension of technical grade KCl and cover liquor should advantageously have a solids content of 30 to 60 percent by weight. Furthermore, the concentration of the aqueous solution of technical grade (NH ₄ I ₂ SO _{4 is} advantageously 30 to 44 percent by weight.

As already mentioned, the NH ₄ C1 concentration of KCl and (NH ") ₂ SO ₄ " in the NH ₃ -containing mother liquor should advantageously be below 18 percent by weight, preferably between 14 and 17 percent by weight.

About 50 to 75 percent by weight of water, preferably 65 to 70 percent by weight, can be removed from the _{practically NH 3} -free mother liquor obtained in stage 4 by evaporation. During the cooling of the evaporated mother liquor, ammonium chloride, which is almost free from intergrowth, is obtained as a crystalline product, which is separated off. The solution adhering to this ammonium chloride is displaced with water on a filter or on a centrifuge, which requires about 20 to 40 percent by weight of water, preferably 30%, based on the amount of _{NH 4 Cl.} This cover water can be combined with the practically NH ₃ -free K ₂ SO ₁ mother liquor of stage 4.

_{The NH 4} C1 mother liquor obtained after the ammonium chloride has been separated off in stage 4 can be repelled or evaporated to dryness, whereby ^{5 can be produced} from the evaporation residue by sublimation of NH ₄ Cl of the highest purity (over 99.5% NH ₁ C!).

The process of the invention is illustrated by the example below and by the process scheme described in more detail.

The method of the invention has the advantage that for the preparation of K ₂ SO ₄ and NH ₄ CI from KCI and (NH _{4) ä} SO ₄ technical Ausgnagsstoffc can be used, ie technical KCI the potash industry, and (NH ₄ J ₂ SO ₄ , which is obtained, for example, as a by-product in organic syntheses.

The process of the invention also makes it possible to produce _{practically chloride-free K 2} SO ₄ with 52% K ₂ O and pure NH _{4 Cl from these technical salts.} The method of the invention is based on the surprising finding that the mixed crystal formation of K ₂ SO ₄ and (NH ₄ I ₂ SO ₄ , which has a decisive influence on the degree of _{purity of the K 2} SO _{4 produced} , can be reduced if the NH _{4 C1-} The concentration in the NH ₃ -saturated mother liquor of the K ₂ SO ₄ crystallization is advantageously below 18 percent by weight NH ₄ Cl. Due to the reduced mixed crystal content in the reaction product, it is only possible to wash out _{the (NH 4 I 2} SO _{4 preferably by blanketing with water up to} to achieve a concentration level of the covered K ₂ SO ₄ of 52% K ₂ O, corresponding to 96% K ₂ SO ₄ , and less than 0.1% chloride.

The method of the invention also offers the advantage that the cover liquor which is obtained in the purification of the K ₂ SO _{4 associated with (NH 4} ) ₂ SO ₄ can be used for mashing the technical KCl. According to the prior art, however, only water can be used for this purpose in order to reduce the unfavorable formation of mixed crystals. Since it is possible according to the process according to the invention to accommodate the cover liquor in the process, _{practically no additional losses occur due to the K 2} SO ₄ purification, so that even when using technical KCl a 98% conversion of the amount introduced K ₂ O is reached.

Furthermore, the method according to the invention offers the advantage that after the ammonia has been driven off from the mother liquor of the K ₂ SO ₄ crystallization, the NaCl introduced with the technical KCl and the KCl not converted to K ₂ SO ₄ and (NH ₄ J ₂ sO ₄ contains ammonium chloride can be obtained with a purity from 99.4 to 99.5% NH ₁ Cl this is achieved by evaporating the practically _NH., -free liquor, namely so far that the crystallized NH ₄ Cl The mother liquor from the NH ₄ C1 crystallization, which contains the accompanying substances that have not been separated out, is evaporated to dryness and sublimated NH ₁ Cl of the highest purity (over 99.5% NH ₁ C!) generated.

example

100 kg technical KCl with the following composition:

KCl (60.2% K., OJ 95.3%

NaCl 4.2%

MgSO, 0.3%

CaSO, 0.05%

ILO 0.15%

are at room temperature (20 to 25 ° C) with 180 kg of recycled cover liquor from the cleaning of the K ₂ SO ₁ , which has the following composition:

K ₂ SO ₄ 8.8%

(NH ₄ I ₈ SO ₄ 4.4%

NH ₄ Cl 1.8%

NaCl 0.1%

NH ₃ 1.3%

H ₂ O 83.6%

Mashed to a suspension with a solids content of 36 percent by weight (stage 1).

_{220 kg of a technical grade (NH 2} ) 2 SO ₄ solution containing 91.5 kg of (NH ₄ ) ₂ SO ₄ are continuously introduced into this suspension over 90 min, with vigorous stirring, and stirring is continued for a further 20 min. _{Thereafter, gaseous NH 3} is introduced into the reaction mixture, in which about 68% of the KCl used has _{crystallized out as K 2} SO ₄ , with continued stirring until about 26 percent by weight of NH _{3 is} practically saturated, in order to separate out the remaining K ₂ SO ₄ (stage 2). The K ₂ SO _{4 is then separated} from 432 kg of mother liquor, which has the following composition:

NH ₄ Cl 15.5%

(NH ₄ J ₁ SO ₄ 1.00%

NaCl 0.97%

KCI 0.37%

MgCl ₂ 0.06%

NH ₃ 25.8%

H ₂ O 56.3%

The _{mother liquor containing NH 3} only contains 1.7% of the KCl used, so that 98.3% of the KCl used has been converted to K ₂ SO ₄ , while the NaCl introduced with the KCl is in the K ₂ SO ₄ -Mother liquor remains enriched. The filter-damp, uncleaned K ₂ SO ₄ is covered in several stages with a total of 158 kg of water (stage 3). This produces 180 kg of concentrated liquor, which is returned in stage 1 to the mashing of the technical KCI

the. After drying the practically chloride-free K ₂ SO ₄ , 114 kg of K ₂ SO _{4 of the} following purity are obtained:

K ₂ SO ₄ (52.0% KoO) 96.2%

(NIU) ₂ SO ₄ 3.6%

Cl 0.05%

432 kg of NHa-saturated mother liquor are _{evaporated after the NH 3 has been} stripped off until 70% of its water content has been removed. After the evaporation mixture has been cooled to 25 to 20 ^° C., the crystallized NH ₄ Cl is separated off from 90 kg of mother liquor (stage 4), which has the following composition:

NH ₄ Cl 22.1%

(NH ₄ ) ₂ SO ₄ 4.1%

NaCI 3.9%

KCl 1.4%

MgCl ₂ 0.2%

_ao H ₂ O 68.3%

18 kg of water are added to the filter-moist NH ₄ Cl to displace the adhering solution (stage 5). This produces 34 kg of cover water, which is combined with the next batch of practically a5 NH ₃ -free mother liquor from the K ₂ SO ₄ crystallization of level 4, which is to be evaporated.

After the purified NH ₄ Cl has been dried, 39 kg of NH ₄ Cl of the following purity are obtained:

NH ₄ Cl 99.5%

K 0.15%

'Na 0.05%

SO ₄ 0.12%

_{For further utilization, the NH 4} Cl mother liquor is evaporated and 16 kg of NH 4 Cl of the highest purity (over 99.5% NH ₄ Cl) are obtained from the evaporation residue by sublimation.

1 sheet of drawings

Claims (1)

21 Claims · P 1. Process for the production of practically chloride-free K “SO ₄ and of pure NH ₄ CI from KCI and (NH ₄ ^ SO ₄ by continuously stirring in a concentrated to saturated solution of technical grade (NH ₄ ), SO ₄ with a small excess of about 5 to 10 mole percent in an aqueous mashing of KCl and reaction with the KCl with crystallization of the main amount of K., SO ₄ and subsequent introduction of gaseous NH ₃ to practical saturation while maintaining a temperature of 15 to 40 ⁰ C with crystallization of the rest Amount of K., SO ₄ and separating the K »SO ₄ from the mother liquor, characterized in that (1) to mash the technical KCl to a suspension, the _{cover liquor returned from the K 2} SO ₄ cleaning is used; ^ao (2) in the reaction of KCl and (NH ₄ ) ₂ SO ₄ ΐ Yu ^A rTr ^niak _t ^en _t ^thalten f ⁿ mother liquor ⁴ Su rn ° ^{n Un weight} " percent INH ₄ Cl is; _a5 (3) the separated K ₂ SO ₄ with water up to