CA1169630A - Process for producing potassium sulfate - Google Patents
Process for producing potassium sulfateInfo
- Publication number
- CA1169630A CA1169630A CA000355026A CA355026A CA1169630A CA 1169630 A CA1169630 A CA 1169630A CA 000355026 A CA000355026 A CA 000355026A CA 355026 A CA355026 A CA 355026A CA 1169630 A CA1169630 A CA 1169630A
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- Prior art keywords
- reaction
- potassium
- reactor
- temperature
- chloride
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/02—Preparation of sulfates from alkali metal salts and sulfuric acid or bisulfates; Preparation of bisulfates
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- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
Abstract of the Disclosure A process for producing K2SO4 by reacting KC? with H2SO4 is provided wherein 2.0 - 2.2 mols of KC? are reacted with one mol of H2SO4 with stirring at room temperature to 100°C, and the resulting KHSO4 is reacted with unreacted KC? at 300° - 400°C. Muffle furnace is suitable as the reactor of the second step.
According to this two-step process, reaction can be carried out at lower temperature and in shorter time, and a long time continuous operation is possible.
According to this two-step process, reaction can be carried out at lower temperature and in shorter time, and a long time continuous operation is possible.
Description
- I 1 fi9631) TITLE OF TI~E INVENTION
Process for producing potasslum sulfate BACKGROUND OF TIIE INVENTION
Field of the Invention: .
This invention relates to a process for producing potassium sulfate from potassium chloride and sulfuric acid in two steps.
Description of the Prior Art:
A process of reacting 2 mols of potasqium chloride with one mol of sulfuric acid to obtain potassium sulfate via potassium hydrogen sulfate and also recover hydrogen chloride evolved, has been commercially operated, When this reaction is carried out in dry manner, it is separated into the following two steps:
The first step reaction proceeds even at a relatively low temperature such as room temperature to 100C, but a considerably high temperature such a~ 300C to 500C is necessary for advancing the second step reaction to~a su~stantial extent. Thus, although the reactions of the first and second steps can be carried out in the same reactor ~only the reactor : of the second step will be hereinafter referred to as reaction furnace), it i~ regarded as preferable and efficient particu-larly for the continuous production process to separate the two step~ into a first step carried out in a reactor and ~.
I ~ 8~3(~
a second step carried out in a reaction furnace to thereby substantially alleviate the load of the reaction furnace for the second step.
First step: ~C~ + i~2SO~ c KIISO4 ~ HCQ ~ 3RCaQ (1) Second step: K~ISO4 + KCQ ~ K2S04 + HCR - 17KCaQ (2) "
Now, Japanese patent publication No. 756/1957 disclose~
a process of carrying out the reaction in two steps wherein separate reactors are employed in the respective steps.
The gist of the process is as follows: a process for produc-ing alkali metal sulfates and hydrogen chloride gas from alkali metal chlorides and sulfuric acid which consists of a first step of feeding into a reactor, an alkali metal chloride and sulfuric acid in such amounts that an acid salt containlng 35% or less of a normal salt i8 prepared, and maintaining the reaction temperature at a temperature at which the resulting material is molten, and a second step of feeding a deficient amount of the alkali metal chloride necessary for preparing the normal salt, to the molten material to somplete the formation reaction of the normal salt.
According to the process, however, problems with respect of operation and corrosion have been raised. Namely, in the first step, a temperature of 200 to 250C is required for forming 35~ or less of the normal salt, while, in case where the acid salt 1~ potaYsium yd gen sulfate, it melts at _ ..
;~
I 1 6963() about 210C; hence agitation is difflcult as compared with the case where they are mixed together both in the form of powder. Further, in order to withstand hydrogen chloride evolved at such a temperature, lt is nece~sary to employ e.g. acid resistant brick as the material for the reactor, and also in order to maintain the reaction temperature, external heating is nece~sary. In addition, since a solid phase reaction i8 carried out at 400C or higher in the second step, heat conduction is so poor that a high temper-ature and long time treatment is compelled.
The above-mentioned problems of the Japanese patent publication No. 756/1957 have been partly solved by a process disclosed in Japanese patent publication No. 2,666/1957..
Namely, accordlng to the proce~s, an acid salt containing 45~ or less of a normal ~alt i~ formed.in the reactor of the first step, and it is once cooled, to solidify it, followed by fine pulverization. Thereafter, a deficient amount of the chloride necessary for preparing the normal salt is added thereto, and they are uniformly mixed together and then fed to the reactor of the second step, whereby the time required at 300 to 500C is shortened for example, from 6 hours to 3 hours. However, even when the process of Japanese patent publication No. 2666/1957 i~ employed, the problem that such a high temperature as 250C is required in the reactor of the first step cannot be overcome, and I 1 6!~fi3~
al~o the process of Japanese p~tent publication No. 2666/1977 has a disaclvantage that steps of cooling and mill-m$xing the reaction product of the first step are newly added.
The present inventors have made studies through practical operations for many years on the technical problems with regard to the produc~ion ~rocess of potassium sulfate, and as a result, the ~ollowing process ha~ been founa:
One mol of sulfuric acid and 2.0 to 2.2 mol~ of pota~sium chloride are first subjected to the above-mentioned reaction of the first step i.e. formation of potassium hydrogen ~ulfate, at a temperature of room temperature to 100C in the form of powder as it i8, and thereafter a mixture of potassium hydrogen sulfate as the re~ulting product with unreacted potasslum chloride is reacted together at a temperature of 300 to 400C in a reaction furnace of the ~econd ~tep.
At that time, by employing a definite muffle furnace as a reaction furnace of the second step, and also by carrying out feed of the raw materials and withdrawal of the reaction product in adequate manners, the problem of melting and corrosion brought about by the high temperature of the first step as well as the problem of the life of the furnace brought about by the necessity of a long retention time at high temperature in the second step, have been both solved.
1 1 6963t~
SUMMARY OF THE INVENTIO~
As is apparent from the above description, a fir~t object of the present invention is to provide a dry process for producing potassium sulfate by way of a new two-step process. A second object thereof is to provide said process wherein mixing with stirring i3 well effected and react$on can be completed in a shorter time. Other objects thereof will become apparent from the following description.
The present invention re6ides in:
(l) In the proce~s for producing potassium ~ulfate or a mixture thereof with a ~mall amount of unreacted potasslum chloride, by reacting potassium chloride with sulfuric acid, the improvement which comprises ~ reacting 2.0 to 2.2 mols of potassium chloride with one mol of sulfuric acid under mixing at a temperature of room temperature to 100C to form potassium hydrogen sulf~te, and then ~ reacting this potassium hydrogen sulfate with unreacted potassium chloride at a temperature of 300 to 400C to produce potas~ium sulfate.
The present invention further resides in the following processes:
Process for producing potasslum sulfate BACKGROUND OF TIIE INVENTION
Field of the Invention: .
This invention relates to a process for producing potassium sulfate from potassium chloride and sulfuric acid in two steps.
Description of the Prior Art:
A process of reacting 2 mols of potasqium chloride with one mol of sulfuric acid to obtain potassium sulfate via potassium hydrogen sulfate and also recover hydrogen chloride evolved, has been commercially operated, When this reaction is carried out in dry manner, it is separated into the following two steps:
The first step reaction proceeds even at a relatively low temperature such as room temperature to 100C, but a considerably high temperature such a~ 300C to 500C is necessary for advancing the second step reaction to~a su~stantial extent. Thus, although the reactions of the first and second steps can be carried out in the same reactor ~only the reactor : of the second step will be hereinafter referred to as reaction furnace), it i~ regarded as preferable and efficient particu-larly for the continuous production process to separate the two step~ into a first step carried out in a reactor and ~.
I ~ 8~3(~
a second step carried out in a reaction furnace to thereby substantially alleviate the load of the reaction furnace for the second step.
First step: ~C~ + i~2SO~ c KIISO4 ~ HCQ ~ 3RCaQ (1) Second step: K~ISO4 + KCQ ~ K2S04 + HCR - 17KCaQ (2) "
Now, Japanese patent publication No. 756/1957 disclose~
a process of carrying out the reaction in two steps wherein separate reactors are employed in the respective steps.
The gist of the process is as follows: a process for produc-ing alkali metal sulfates and hydrogen chloride gas from alkali metal chlorides and sulfuric acid which consists of a first step of feeding into a reactor, an alkali metal chloride and sulfuric acid in such amounts that an acid salt containlng 35% or less of a normal salt i8 prepared, and maintaining the reaction temperature at a temperature at which the resulting material is molten, and a second step of feeding a deficient amount of the alkali metal chloride necessary for preparing the normal salt, to the molten material to somplete the formation reaction of the normal salt.
According to the process, however, problems with respect of operation and corrosion have been raised. Namely, in the first step, a temperature of 200 to 250C is required for forming 35~ or less of the normal salt, while, in case where the acid salt 1~ potaYsium yd gen sulfate, it melts at _ ..
;~
I 1 6963() about 210C; hence agitation is difflcult as compared with the case where they are mixed together both in the form of powder. Further, in order to withstand hydrogen chloride evolved at such a temperature, lt is nece~sary to employ e.g. acid resistant brick as the material for the reactor, and also in order to maintain the reaction temperature, external heating is nece~sary. In addition, since a solid phase reaction i8 carried out at 400C or higher in the second step, heat conduction is so poor that a high temper-ature and long time treatment is compelled.
The above-mentioned problems of the Japanese patent publication No. 756/1957 have been partly solved by a process disclosed in Japanese patent publication No. 2,666/1957..
Namely, accordlng to the proce~s, an acid salt containing 45~ or less of a normal ~alt i~ formed.in the reactor of the first step, and it is once cooled, to solidify it, followed by fine pulverization. Thereafter, a deficient amount of the chloride necessary for preparing the normal salt is added thereto, and they are uniformly mixed together and then fed to the reactor of the second step, whereby the time required at 300 to 500C is shortened for example, from 6 hours to 3 hours. However, even when the process of Japanese patent publication No. 2666/1957 i~ employed, the problem that such a high temperature as 250C is required in the reactor of the first step cannot be overcome, and I 1 6!~fi3~
al~o the process of Japanese p~tent publication No. 2666/1977 has a disaclvantage that steps of cooling and mill-m$xing the reaction product of the first step are newly added.
The present inventors have made studies through practical operations for many years on the technical problems with regard to the produc~ion ~rocess of potassium sulfate, and as a result, the ~ollowing process ha~ been founa:
One mol of sulfuric acid and 2.0 to 2.2 mol~ of pota~sium chloride are first subjected to the above-mentioned reaction of the first step i.e. formation of potassium hydrogen ~ulfate, at a temperature of room temperature to 100C in the form of powder as it i8, and thereafter a mixture of potassium hydrogen sulfate as the re~ulting product with unreacted potasslum chloride is reacted together at a temperature of 300 to 400C in a reaction furnace of the ~econd ~tep.
At that time, by employing a definite muffle furnace as a reaction furnace of the second step, and also by carrying out feed of the raw materials and withdrawal of the reaction product in adequate manners, the problem of melting and corrosion brought about by the high temperature of the first step as well as the problem of the life of the furnace brought about by the necessity of a long retention time at high temperature in the second step, have been both solved.
1 1 6963t~
SUMMARY OF THE INVENTIO~
As is apparent from the above description, a fir~t object of the present invention is to provide a dry process for producing potassium sulfate by way of a new two-step process. A second object thereof is to provide said process wherein mixing with stirring i3 well effected and react$on can be completed in a shorter time. Other objects thereof will become apparent from the following description.
The present invention re6ides in:
(l) In the proce~s for producing potassium ~ulfate or a mixture thereof with a ~mall amount of unreacted potasslum chloride, by reacting potassium chloride with sulfuric acid, the improvement which comprises ~ reacting 2.0 to 2.2 mols of potassium chloride with one mol of sulfuric acid under mixing at a temperature of room temperature to 100C to form potassium hydrogen sulf~te, and then ~ reacting this potassium hydrogen sulfate with unreacted potassium chloride at a temperature of 300 to 400C to produce potas~ium sulfate.
The present invention further resides in the following processes:
(2) A process according to that of the above item (l) wherein the formation reaction of potassium hydrogen sulfate is con-tinoously carr~ed out in a r-a~ or of the flrRt step and that .
, of potassium sulfate is continuously carried out in a reactor of the second step.
~3) A process according to that of the above item ~2) wherein a muffle furnace whose upper half surface alone can be heated is employed as the reactor of the second step.
(4) A proce~s according to that of the above item (2) wherein the reaction product of the second step is recovered by over-1Ow.
DETAILED DESCRIPTION OF THE INVENTION
The constitution and effectiveness of the pre~ent invention will be described below in detail.
~a) Reaction of the first step in the reactor of the first step:
As is seen in the above-mentioned equation of the react$on of the first ~tep, one mol of potassium chloride and one mol of sulfuric acid yield one mol of potassium hydrogen ~ulfate and one mol of hydroqen chloride, but, in the present inventlon, sulfuric acid (98~) and potassium chloride are employed in a proportion of one mol of the former and 2.0 to 2.2 mol~ of the latter, and potassium chloride to be reacted in the second step is mixed in advance in the first step. The reaction temperature i8 in the range of room temperature to 100C, and the reactor employed may be those made of a material resistant to sulfuric acid and dry hydrogen chloride at the reaction temperature;
1 1 69~3 ~) no special material such as acid resistant brick is required aue to the low reaction temperature~ Further, it i8 prefer-able to employ an agitator e.g. paddle or ribbon agitator (preferably equipped with double or more shafts) suitable for mixing pewder ~potassium chloride, etc.) with liquid ~sulfuric acid). As for the type of the reaction vessel, either vertical typé or horizontal type may be employed.
The reaction of the first step in the process of the present invention proceeds very smoothly and rapidly even at a temper-ature of room temperature to 100C, due to the pre~ence ofexcessive potassium chloride, and since only a small amount of unreacted ~ulfuric acid is present in the reaction product, this product is of flowable powder; hence it i8 easy to transfer the product into the reactor of the second step.
On the other hand, hydrogen chloride evolved i~ ~ent to an apparatus for producing concentrated hydrochloric acid, and its concentration is in the range of 40 to 60~ by volume although it is v~ied dependlng on the operational conditions.
The retention time in the reactor of the first step may be in the range of 30 minutes to 3 hours, preferably in the range of 30 minutes to one hour, both in the case of batch process and in the case of continuous process.
(b) Reaction of the second step in the reactor of the second step:
As is ~een in the equation of the reaction of the second 1 1 69fi3() ~tep, one mol of potassium hydrogen sulfate and one mol of potassium chloride theoretically yield one mol of potassium sulfate and one mol of hydrogen chloride, but, in the process of the present invention, the amount of pota~ium chloride fed into the reactor of the first step is in the range of 2.0 to 2.2 mols per mol of sulfuric acid. If it exceeds 2 mols, the resulting product is a mixture of pota~sium sulfate with potassium chloride, and potassium chloride contributes to preventing unreacted potassium hydrogen sulfate from discharge in molten state to thereby make easy the transfer of the reaction product after the reaction of the ~econd step. On the other hand, even when the equimolec-ular reaction of the present invention ~i.e. amount of RC~, 2.0 mols; amount of sulfurlc acid, one mol) $s carried out, the presence of unreacted potassium chloride corresponding to the presence of potassium hydrogen chloride as an inter-mediate in the product contained in the reactor of the ~econd step, make~ it possible to notably reduce the ~urface tackiness of the reaction product. The reaction of the second step is a reaction between a ~olid (KC~) and a melt ~KHSO4) and yet is an endothermic reaction. Thus, unles~ the mutual contact and heating ~and hence heat tran~fer) of the reactants are ~ufficient, it is impossible to improve the conver6ion and shorten the reaction time ~retention time). Further, in the case of continuous reaction, particularly an unreacted 1 3 696~() portion of the reaction mixture where reaction has not yet advanced sufficiently should be prevented from di~charge ln ~hort-circuit manner, Now the pre~ent inventors have found that ~ muf1e furnace capable of heating the reaction mixture rom its upper ~urface alone is surprisingly more suitable for attaining the above-mentioned ob~ects of the present invention than tubular furnace capable of heating the reaction mixture from its total periphery. Further the present inventor~ have also found that ~ it i8 effective for prevent-ing the above-mentioned di wharge in ~hort-circuit manner to di~charge the reaction product of the second ~tep by overflow.
The reason fox the above item ~ iB presumed to be in that, in the case of tubular furnace, molten potassium hydrogen sulfate i~ more liable to adhere to the ~urface of the lower half part of the furnace~ At any rate, heat transfer iB poor on the surface of the lower half part of the furn~ce. Similarly the reason for the above item ~ is presumed to be in that, in the ca~e of overflow, a portion of the reaction mixture contain-ing a smaller amount of melt is more liable to be smoothly discharged. These method~ ~ and ~ , however, could not have been entirely antlcipated from the above-mentioned Japanese patent publication Nos. 756~1957 and 2666/1957 wherein tubular furnace was substantially employed ~Note: The appli-cants of these prior art inventions are substantiAlly the same company. In addition, see Japanese patent publication ~ 1 6~630 No. 10153/1959). Further r according to these prior art inventions, the reaction of the fir~t step is so adjusted as to contain 35~ to 45~ of a normal salt tpotassium sulfate) to thereby reduce the ~ubstantial load of the reactlon furnace of the second step. In this respect, it is clear that the techniques of these inventions are different from the proce~s of the present invention.
As a re~ult, in the case of the Japanese patent publication No. 2666~1957, the residual percentage of chlorine is 2.4 to 1.6% by we$ght at 300 to 400C in one hour, wherea~
according to the proces~ of the present invention, it i8 possible to attain conversions to the same extent after completion of the reaction of the second step, without pa~ing through steps of cooling, solidification and fine milling between the fir~t ~tep and the ~econd step.
~c) Quenching of the reaction product discharged from the reactor of the second step:
The reaction product has a temperature of about 300 to 370C, and depending on the reaction condition~, it still contains about 1.5 to 2.5~ by weight of chlorine and also about 2.0 to 3.0~ by weight of sulfuric acid. Thus, when the product is used as potassium sulfate for fertilizers or indu~tries, it is necessary to neutralize the product with lime or the like in a separate step, and also the product must be cooled down to a suitable temperature ~uch as room '`i ' ' . . .
~i ' 1 J 6963', temperature to 200C, for it~ transfer. According to an embodiment of the present invention, it i~ possible to partly cool the discharge by scatterlng or dropwise adding a small amount of water thereon. The water-pourlng of this embodiment i~ carried out by scattering or dropwise adding water in such an extent of amount that its temperature ls elevated by the sensible heat of the reaction product of the second step di~charged by overflow whereby it i~
vaporized~ in a cooler or a transfer vessel ~r the product.
More concretely, for example, 40 to 60 Kg of water is scattered on 1,000 Kg of the mixture at 300C. When the temperature of the reaction product i~ reduced down to 100C
or lower by the water-pouring, it become~ imposslble to vaporize the scattered water, and hence the subsequent cooling is carried out by heat transfer or alr cooling.
~d) Summary of the effectiveness o~ the process of the present invention:
~ he novelty and characteri~tic effectiveness of the proce3s of the present invention have already been clarified by the detailed descriptions in the foregoing items (a), ~b) and (c), and they may be summarized as follows:
~ Due to the low reaction temperature in the reactor of the first ~tep, carrying out of the reaction of the first step, and transfer and supply of the resulting reaction product to the reactor of the second step are very easy.
~ 1 6963V
Thi~ i8 brought about by the fact that no melt of pota~sium hydrogen ~ulfate i8 formed in the reactor of the first step.
~ Carrying out of the reaction of the ~econd step in the reactor of the second step and continuous discharge of the resulting reactlon product are very easy, and also it i8 poss~ble to complete the reactlon at a relatlvely low temper-ature such a~ 300 to 400C, and in a reactlon time as short as one hour. This is presumed to be brought about by the following fact~.
0 (A) In case where the ~mount of potassium ahloride i~
in small exces~ of the equivalent to that of sulfurlc ac~d in ~uch a manner that the molar ratio by mol of potasslum chloride to sulfuric acid as raw materials employed is more than 2.0 and not more than 2.2, the molar ratio of unreaoted potass~um hydrogen sulfate to unreacted potas~lum chloride becomes le~s with the progres~ of the reaction in the reactor of the second step, whereby the amount of unreacted KHSO4 can be rapidly reduced down to a definite value.
(b) Further, in the case of a ratio of ~ulfuric acid/
potassium chloride of 2.0, too, the reaction mlxture of the fir6t ~tep (pota~ium hydrogen sulfate plus potassium chlorlde) in a very good finely mlxed state is supplied to the reactor of the ~econd step, whereby the amount of the reaction mlxture aischarged in ~hort-circult manner is extremely small.
~ Slnce the reaction temperature ln the reactor of the second I 1 6963() step ia not necessary to be a~ high a temperature as 400-to 500C, the 10~8 of the heat re~istant bricks on the ~urface of radlation heat muffle furnace i~ le88 tnote:
the temperature in~lde the flue of mu~fle furnaco i9 1100-to 1200C), which make~ pos~l~le a long time operatlon as long a~ one to three year~. Further, since the heat trsnsfer area per unit volume may be small, it 1~ easy to make the capaclty larger than tubular furnace.
The present invention will be further illu~trated by way of Example, but lt should not be construed to be limited thereby.
Example 1 Into a flrst step reactor of clo~ed and horizontal type equipped wlth an agitatox wore contlnuously fed 163 Kg~hr o~
96~ potasslum chloride and 100 ~g/hr of 98~ sulfuric acld, and the xeaction temperature was malntalned at 60- to 70-C
~y allowing them to cool ~KC~/H2SO4 - 2.1). In order to prevent hydrogen chloride gas evolved, from scattering away to the atmo~phere, the pre~ure in~ide the reactor was maintained under a slight reduced pre~sure of -5 to -10 mm water-gauge to obtaln 40.3 Nm3/hr of hydrogen chloride having a concentration of S0~ by volume.
Next, the total amount o~ the reaction product of the flrst step was continuously fed to a reactor of the second ~tep ~muffle furnace) whose upper half surface alone can be 1 1 69~3~) -heated by radiatlon and which i8 equlpped wlth a double-~haft agltator.
The reaction product of the first ~tep wa~ fed into the muffle furnAce at a location between the central part and the raw material-feeding port of the furnace and clo~o to this feeaing port; the temperature of the reaction mlxture ln the furnace wns malntalned at 350-C; and the retentlon time was one hour. The pressure inside the reactor of the second step was maintained under 0 to -5 mm water-gauge.
As a re~ult, 39.6 Nm3/hr of hydrogen chloride having a con-centration of 608 by volume were obtained. Further, 183 Rg/
hr of the reaction product were overflown from the reactor of the second step. Other re~ults are shown in Table 1.
Comparative exmaPle 1 Thl~ experlment wa~ carriod out ln the same manner a~
ln Example 1 except that potas~lum chloride and conc. ~ulfurlc acid were fed dlrectly to the reactor of the ~econd ~tep, and the retention time in~ide the reactor was 2 hour~. The re~ult~
are shown in Table 1. 71.7 Nm3/hr of hydrogen chloride havlng a concentration of 60% by volume and 184 Xg/hr of a reactlon product were obtained. Other results are al~o ~hown in Table 1.
1 1 69~3~
Table l Result~ of reaction .
~eaction product Reaction product of of first step second ~tep C~ ~ ~12SO4 ~ C~ conver- Cl ~ H2SO4 ~ C~ conver-~ion ~ sion _ Example 18.6 4.342,9 2.7 1.07 93.4 Compara-tive ex. 3 5 2.13 91.4 It is evident from Table l that ln the case of Comparative example 1, the amount of chlorine and that of sulfuric acld are both largerand the reaction 18 in~ufficient.
, ...
s .:~
. :
, of potassium sulfate is continuously carried out in a reactor of the second step.
~3) A process according to that of the above item ~2) wherein a muffle furnace whose upper half surface alone can be heated is employed as the reactor of the second step.
(4) A proce~s according to that of the above item (2) wherein the reaction product of the second step is recovered by over-1Ow.
DETAILED DESCRIPTION OF THE INVENTION
The constitution and effectiveness of the pre~ent invention will be described below in detail.
~a) Reaction of the first step in the reactor of the first step:
As is seen in the above-mentioned equation of the react$on of the first ~tep, one mol of potassium chloride and one mol of sulfuric acid yield one mol of potassium hydrogen ~ulfate and one mol of hydroqen chloride, but, in the present inventlon, sulfuric acid (98~) and potassium chloride are employed in a proportion of one mol of the former and 2.0 to 2.2 mol~ of the latter, and potassium chloride to be reacted in the second step is mixed in advance in the first step. The reaction temperature i8 in the range of room temperature to 100C, and the reactor employed may be those made of a material resistant to sulfuric acid and dry hydrogen chloride at the reaction temperature;
1 1 69~3 ~) no special material such as acid resistant brick is required aue to the low reaction temperature~ Further, it i8 prefer-able to employ an agitator e.g. paddle or ribbon agitator (preferably equipped with double or more shafts) suitable for mixing pewder ~potassium chloride, etc.) with liquid ~sulfuric acid). As for the type of the reaction vessel, either vertical typé or horizontal type may be employed.
The reaction of the first step in the process of the present invention proceeds very smoothly and rapidly even at a temper-ature of room temperature to 100C, due to the pre~ence ofexcessive potassium chloride, and since only a small amount of unreacted ~ulfuric acid is present in the reaction product, this product is of flowable powder; hence it i8 easy to transfer the product into the reactor of the second step.
On the other hand, hydrogen chloride evolved i~ ~ent to an apparatus for producing concentrated hydrochloric acid, and its concentration is in the range of 40 to 60~ by volume although it is v~ied dependlng on the operational conditions.
The retention time in the reactor of the first step may be in the range of 30 minutes to 3 hours, preferably in the range of 30 minutes to one hour, both in the case of batch process and in the case of continuous process.
(b) Reaction of the second step in the reactor of the second step:
As is ~een in the equation of the reaction of the second 1 1 69fi3() ~tep, one mol of potassium hydrogen sulfate and one mol of potassium chloride theoretically yield one mol of potassium sulfate and one mol of hydrogen chloride, but, in the process of the present invention, the amount of pota~ium chloride fed into the reactor of the first step is in the range of 2.0 to 2.2 mols per mol of sulfuric acid. If it exceeds 2 mols, the resulting product is a mixture of pota~sium sulfate with potassium chloride, and potassium chloride contributes to preventing unreacted potassium hydrogen sulfate from discharge in molten state to thereby make easy the transfer of the reaction product after the reaction of the ~econd step. On the other hand, even when the equimolec-ular reaction of the present invention ~i.e. amount of RC~, 2.0 mols; amount of sulfurlc acid, one mol) $s carried out, the presence of unreacted potassium chloride corresponding to the presence of potassium hydrogen chloride as an inter-mediate in the product contained in the reactor of the ~econd step, make~ it possible to notably reduce the ~urface tackiness of the reaction product. The reaction of the second step is a reaction between a ~olid (KC~) and a melt ~KHSO4) and yet is an endothermic reaction. Thus, unles~ the mutual contact and heating ~and hence heat tran~fer) of the reactants are ~ufficient, it is impossible to improve the conver6ion and shorten the reaction time ~retention time). Further, in the case of continuous reaction, particularly an unreacted 1 3 696~() portion of the reaction mixture where reaction has not yet advanced sufficiently should be prevented from di~charge ln ~hort-circuit manner, Now the pre~ent inventors have found that ~ muf1e furnace capable of heating the reaction mixture rom its upper ~urface alone is surprisingly more suitable for attaining the above-mentioned ob~ects of the present invention than tubular furnace capable of heating the reaction mixture from its total periphery. Further the present inventor~ have also found that ~ it i8 effective for prevent-ing the above-mentioned di wharge in ~hort-circuit manner to di~charge the reaction product of the second ~tep by overflow.
The reason fox the above item ~ iB presumed to be in that, in the case of tubular furnace, molten potassium hydrogen sulfate i~ more liable to adhere to the ~urface of the lower half part of the furnace~ At any rate, heat transfer iB poor on the surface of the lower half part of the furn~ce. Similarly the reason for the above item ~ is presumed to be in that, in the ca~e of overflow, a portion of the reaction mixture contain-ing a smaller amount of melt is more liable to be smoothly discharged. These method~ ~ and ~ , however, could not have been entirely antlcipated from the above-mentioned Japanese patent publication Nos. 756~1957 and 2666/1957 wherein tubular furnace was substantially employed ~Note: The appli-cants of these prior art inventions are substantiAlly the same company. In addition, see Japanese patent publication ~ 1 6~630 No. 10153/1959). Further r according to these prior art inventions, the reaction of the fir~t step is so adjusted as to contain 35~ to 45~ of a normal salt tpotassium sulfate) to thereby reduce the ~ubstantial load of the reactlon furnace of the second step. In this respect, it is clear that the techniques of these inventions are different from the proce~s of the present invention.
As a re~ult, in the case of the Japanese patent publication No. 2666~1957, the residual percentage of chlorine is 2.4 to 1.6% by we$ght at 300 to 400C in one hour, wherea~
according to the proces~ of the present invention, it i8 possible to attain conversions to the same extent after completion of the reaction of the second step, without pa~ing through steps of cooling, solidification and fine milling between the fir~t ~tep and the ~econd step.
~c) Quenching of the reaction product discharged from the reactor of the second step:
The reaction product has a temperature of about 300 to 370C, and depending on the reaction condition~, it still contains about 1.5 to 2.5~ by weight of chlorine and also about 2.0 to 3.0~ by weight of sulfuric acid. Thus, when the product is used as potassium sulfate for fertilizers or indu~tries, it is necessary to neutralize the product with lime or the like in a separate step, and also the product must be cooled down to a suitable temperature ~uch as room '`i ' ' . . .
~i ' 1 J 6963', temperature to 200C, for it~ transfer. According to an embodiment of the present invention, it i~ possible to partly cool the discharge by scatterlng or dropwise adding a small amount of water thereon. The water-pourlng of this embodiment i~ carried out by scattering or dropwise adding water in such an extent of amount that its temperature ls elevated by the sensible heat of the reaction product of the second step di~charged by overflow whereby it i~
vaporized~ in a cooler or a transfer vessel ~r the product.
More concretely, for example, 40 to 60 Kg of water is scattered on 1,000 Kg of the mixture at 300C. When the temperature of the reaction product i~ reduced down to 100C
or lower by the water-pouring, it become~ imposslble to vaporize the scattered water, and hence the subsequent cooling is carried out by heat transfer or alr cooling.
~d) Summary of the effectiveness o~ the process of the present invention:
~ he novelty and characteri~tic effectiveness of the proce3s of the present invention have already been clarified by the detailed descriptions in the foregoing items (a), ~b) and (c), and they may be summarized as follows:
~ Due to the low reaction temperature in the reactor of the first ~tep, carrying out of the reaction of the first step, and transfer and supply of the resulting reaction product to the reactor of the second step are very easy.
~ 1 6963V
Thi~ i8 brought about by the fact that no melt of pota~sium hydrogen ~ulfate i8 formed in the reactor of the first step.
~ Carrying out of the reaction of the ~econd step in the reactor of the second step and continuous discharge of the resulting reactlon product are very easy, and also it i8 poss~ble to complete the reactlon at a relatlvely low temper-ature such a~ 300 to 400C, and in a reactlon time as short as one hour. This is presumed to be brought about by the following fact~.
0 (A) In case where the ~mount of potassium ahloride i~
in small exces~ of the equivalent to that of sulfurlc ac~d in ~uch a manner that the molar ratio by mol of potasslum chloride to sulfuric acid as raw materials employed is more than 2.0 and not more than 2.2, the molar ratio of unreaoted potass~um hydrogen sulfate to unreacted potas~lum chloride becomes le~s with the progres~ of the reaction in the reactor of the second step, whereby the amount of unreacted KHSO4 can be rapidly reduced down to a definite value.
(b) Further, in the case of a ratio of ~ulfuric acid/
potassium chloride of 2.0, too, the reaction mlxture of the fir6t ~tep (pota~ium hydrogen sulfate plus potassium chlorlde) in a very good finely mlxed state is supplied to the reactor of the ~econd step, whereby the amount of the reaction mlxture aischarged in ~hort-circult manner is extremely small.
~ Slnce the reaction temperature ln the reactor of the second I 1 6963() step ia not necessary to be a~ high a temperature as 400-to 500C, the 10~8 of the heat re~istant bricks on the ~urface of radlation heat muffle furnace i~ le88 tnote:
the temperature in~lde the flue of mu~fle furnaco i9 1100-to 1200C), which make~ pos~l~le a long time operatlon as long a~ one to three year~. Further, since the heat trsnsfer area per unit volume may be small, it 1~ easy to make the capaclty larger than tubular furnace.
The present invention will be further illu~trated by way of Example, but lt should not be construed to be limited thereby.
Example 1 Into a flrst step reactor of clo~ed and horizontal type equipped wlth an agitatox wore contlnuously fed 163 Kg~hr o~
96~ potasslum chloride and 100 ~g/hr of 98~ sulfuric acld, and the xeaction temperature was malntalned at 60- to 70-C
~y allowing them to cool ~KC~/H2SO4 - 2.1). In order to prevent hydrogen chloride gas evolved, from scattering away to the atmo~phere, the pre~ure in~ide the reactor was maintained under a slight reduced pre~sure of -5 to -10 mm water-gauge to obtaln 40.3 Nm3/hr of hydrogen chloride having a concentration of S0~ by volume.
Next, the total amount o~ the reaction product of the flrst step was continuously fed to a reactor of the second ~tep ~muffle furnace) whose upper half surface alone can be 1 1 69~3~) -heated by radiatlon and which i8 equlpped wlth a double-~haft agltator.
The reaction product of the first ~tep wa~ fed into the muffle furnAce at a location between the central part and the raw material-feeding port of the furnace and clo~o to this feeaing port; the temperature of the reaction mlxture ln the furnace wns malntalned at 350-C; and the retentlon time was one hour. The pressure inside the reactor of the second step was maintained under 0 to -5 mm water-gauge.
As a re~ult, 39.6 Nm3/hr of hydrogen chloride having a con-centration of 608 by volume were obtained. Further, 183 Rg/
hr of the reaction product were overflown from the reactor of the second step. Other re~ults are shown in Table 1.
Comparative exmaPle 1 Thl~ experlment wa~ carriod out ln the same manner a~
ln Example 1 except that potas~lum chloride and conc. ~ulfurlc acid were fed dlrectly to the reactor of the ~econd ~tep, and the retention time in~ide the reactor was 2 hour~. The re~ult~
are shown in Table 1. 71.7 Nm3/hr of hydrogen chloride havlng a concentration of 60% by volume and 184 Xg/hr of a reactlon product were obtained. Other results are al~o ~hown in Table 1.
1 1 69~3~
Table l Result~ of reaction .
~eaction product Reaction product of of first step second ~tep C~ ~ ~12SO4 ~ C~ conver- Cl ~ H2SO4 ~ C~ conver-~ion ~ sion _ Example 18.6 4.342,9 2.7 1.07 93.4 Compara-tive ex. 3 5 2.13 91.4 It is evident from Table l that ln the case of Comparative example 1, the amount of chlorine and that of sulfuric acld are both largerand the reaction 18 in~ufficient.
, ...
s .:~
. :
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In the process for producing potassium sulfate, or a mixture thereof with a small amount of unreacted potassium chloride, by reacting potassium chloride with sulfuric acid, the improvement which comprises:
(i) continuously reacting by mixing in a first reaction zone potassium chloride and sulfuric acid in the mole ratio of 2 to 2.2:1 at a temperature of from ambient to 100°C to form potassium hydrogen sulfate; and (ii) continuously reacting in a second reaction zone separate from said first reaction zone the potassium hydrogen sulfate with unreacted potassium chloride at a temperature of 300 to 400°C to produce potassium sulfate, wherein the reactants in said second reaction zone are indirectly heated by application of heat only to the upper half surface thereof, and wherein the potassium sulfate product contains, by weight, 1.5 to 2.5% residual chlorine and 2 to 3% residual sulfuric acid.
(i) continuously reacting by mixing in a first reaction zone potassium chloride and sulfuric acid in the mole ratio of 2 to 2.2:1 at a temperature of from ambient to 100°C to form potassium hydrogen sulfate; and (ii) continuously reacting in a second reaction zone separate from said first reaction zone the potassium hydrogen sulfate with unreacted potassium chloride at a temperature of 300 to 400°C to produce potassium sulfate, wherein the reactants in said second reaction zone are indirectly heated by application of heat only to the upper half surface thereof, and wherein the potassium sulfate product contains, by weight, 1.5 to 2.5% residual chlorine and 2 to 3% residual sulfuric acid.
2. A process according to claim 1, wherein the reaction product of step (ii) is recovered by overflow.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP91811/1979 | 1979-07-19 | ||
| JP9181179A JPS5617921A (en) | 1979-07-19 | 1979-07-19 | Manufacture of potassium sulfate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1169630A true CA1169630A (en) | 1984-06-26 |
Family
ID=14037005
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000355026A Expired CA1169630A (en) | 1979-07-19 | 1980-06-27 | Process for producing potassium sulfate |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5617921A (en) |
| CA (1) | CA1169630A (en) |
| ES (1) | ES8105962A1 (en) |
| GB (1) | GB2053881B (en) |
| IT (1) | IT1149206B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1177222A (en) | 1980-09-30 | 1984-11-06 | Hidemaro Iwashita | Apparatus for producing an alkali metal salt of a mineral acid, and a process |
| JPS57205315A (en) * | 1981-06-15 | 1982-12-16 | Chisso Corp | Reducting method for amount of chlorine contained in modified potassium sulfate by very small amount |
| JPS58161917A (en) * | 1982-03-19 | 1983-09-26 | Onoda Kagaku Kogyo Kk | Manufacture of potassium sulfate |
| CN1042722C (en) * | 1995-07-23 | 1999-03-31 | 云南磷肥厂 | Non-recovery process for producing potassium sulphate by Mannheim furnace |
| EP3647300A1 (en) | 2018-11-01 | 2020-05-06 | Tessenderlo Group NV | Potassium sulfate containing trace elements |
| CN116022827A (en) * | 2022-12-07 | 2023-04-28 | 齐齐哈尔市茂尔农业有限公司 | Production process for potassium sulfate fertilizer |
-
1979
- 1979-07-19 JP JP9181179A patent/JPS5617921A/en active Granted
-
1980
- 1980-06-27 CA CA000355026A patent/CA1169630A/en not_active Expired
- 1980-07-10 IT IT49212/80A patent/IT1149206B/en active
- 1980-07-18 ES ES493528A patent/ES8105962A1/en not_active Expired
- 1980-07-21 GB GB8023793A patent/GB2053881B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2053881A (en) | 1981-02-11 |
| GB2053881B (en) | 1983-09-14 |
| JPS5617921A (en) | 1981-02-20 |
| IT1149206B (en) | 1986-12-03 |
| JPS6256085B2 (en) | 1987-11-24 |
| ES493528A0 (en) | 1981-07-01 |
| ES8105962A1 (en) | 1981-07-01 |
| IT8049212A0 (en) | 1980-07-10 |
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