4, summary of the invention
The present invention is to the effect that: (Wingdale major ingredient is calcium carbonate first to select nitric acid and Wingdale, also unslaked lime or white lime can be selected) reaction generation ca nitrate soln, then ca nitrate soln and potassium sulfate are carried out replacement(metathesis)reaction, generate calcium sulfate precipitation and potassium nitrate solution, the potassium nitrate solution generated after removing calcium impurities, then is industrial potassium nitrate through evaporation, crystallization, separation, drying.React with nitric acid, Wingdale and potassium sulfate and produce saltpetre and calcium sulfate total reaction equation is as follows:
CaCO
3+2HNO
3+K
2SO
4+H
2O=2KNO
3+CaSO
4·2H
2O↓+CO
2↑····(1)
Also nitric acid, unslaked lime (major ingredient is calcium oxide) and potassium sulfate can be selected to react and produce saltpetre and calcium sulfate, total reaction equation is as follows:
CaO+2HNO
3+K
2SO
4+H
2O=2KNO
3+CaSO
4·2H
2O↓····(2)
Also nitric acid, white lime (major ingredient is calcium hydroxide) and potassium sulfate can be selected to react and produce saltpetre and calcium sulfate, total reaction equation is as follows:
Ca(OH)
2+2HNO
3+K
2SO
4=2KNO
3+CaSO
4·2H
2O↓····(3)
React for nitric acid, unslaked lime and potassium sulfate below and produce saltpetre and calcium sulfate, describe this in detail
Summary of the invention:
(1) neutralization reaction produces ca nitrate soln:
In neutralization reactor, add the circulation potassium mother liquor III returned in (6), add the calcium carbonate impurity returned in (5), add unslaked lime, then slowly add salpeter solution, under constant agitation, neutralization reaction occurs, and generate ca nitrate soln, its main chemical reactions equation is expressed as follows:
CaO+2HNO
3=Ca(NO
3)
2+H
2O·········(4)
In reaction process, control feed rate, controls temperature of reaction is 60-100 DEG C, control adjustment reacting solution pH value be 6.5-7.0, control reaction produce in feed liquid in ca nitrate soln massfraction be 30-70%.If unslaked lime is excessive, solution, 25 DEG C time, can form three hydrated basic nitrocalcite, 100 DEG C time, has dihydrate and semihydrate formation.Its main chemical reactions equation is expressed as follows:
Ca(OH)
2+Ca(NO
3)
2+2H
2O=Ca(NO
3)
2·CaO·3H
2O········(5)
Ca(OH)
2+Ca(NO
3)
2+H
2O=Ca(NO
3)
2·CaO·2H
2O·········(6)
2Ca(OH)
2+2Ca(NO
3)
2=2Ca(NO
3)
2·2CaO·H
2O+H
2O·······(7)
So need strict control nitric acid and unslaked lime reaction ratio, controlling adjustment reacting solution pH value is 6.5-7, prevents hydrated basic nitrocalcite.
(2) filtering and impurity removing
By during reaction generates in (1) and feed liquid pass through frit removing impurity, filtered impurities 30-95 DEG C of water washing, filtrate and washings merge and are purer neutralizer, and major ingredient is contain nitrocalcite and potassium nitrate solution.
(3) replacement(metathesis)reaction extracting sulfuric acid calcium:
In double decomposition reactor, add the neutralizer of removing impurity in (2), under agitation, slowly add potassium sulfate, nitrocalcite and potassium sulfate replacement(metathesis)reaction generate sulfate dihydrate calcium deposit and saltpetre.In reaction process, control temperature of reaction is 60-100 DEG C, and control potassium sulfate in reaction soln: nitrocalcite (mol ratio)=1: (1-1.2), its main chemical reactions equation is as follows:
Ca(NO
3)
2+K
2SO
4+2H
2O=2KNO
3+CaSO
4·2H
2O↓·····(8)
K
2SO
4+CaSO
4+H
2O=K
2SO
4·CaSO
4·H
2O·······(9)
In above-mentioned replacement(metathesis)reaction, in order to reduce and avoid generating K
2sO
4caSO
4h
2o double salt precipitation, reduces the loss of potassium, therefore adds excess nitric acid calcium.Potassium sulfate in optimum control reaction soln: nitrocalcite (mol ratio)=1: 1.05.
(4) terra alba separating, washing:
Reaction feed liquid in (3) is passed through frit and is separated to obtain terra alba crystal, the terra alba 30-95 DEG C of water washing of separation, separation terra alba filtrate and washings merge, and major ingredient, for containing potassium nitrate solution, is referred to as potassium mother liquor I.
(5) potassium nitrate solution deliming:
Add in calcium-removing reactor by potassium mother liquor I in (4), add salt of wormwood, stirring reaction in calcium-removing reactor, by the calcium ion removing in the calcium sulfate containing trace in potassium mother liquor I and nitrocalcite, its main chemical reactions equation is as follows:
CaSO
4+K
2CO
3=K
2SO
2+CaCO
3↓·······(10)
Ca(NO
3)
2+K
2CO
3=2KNO
3+CaCO
3↓·······(11)
Control temperature of reaction 60-100 DEG C, reaction times 1-3 hour, controlling adjustment reacting solution pH value is 7-7.5, and crossed by solution after reaction after filtering calcium impurities and obtain potassium mother liquor II, calcium impurities, because of containing calcium carbonate, returns in (1) and recycles.
(6) evaporative crystallization be separated drying:
Potassium mother liquor II heating evaporation in (5) is concentrated into 45-55 degree Beaume, be cooled to 20 DEG C to 50 DEG C again, solution crystallization separates out a large amount of potassium nitrate crystals, then potassium nitrate crystals feed liquid is carried out centrifugation obtains potassium nitrate crystals, is separated potassium nitrate crystals is industrial potassium nitrate after drying.Separation saltpetre gained potassium mother liquor III returns in (1) and recycles.
By above-mentioned steps cyclical operation, industrial potassium nitrate and terra alba can be obtained continuously.
5, invention feature
The present invention has following advantage:
(1) potassium transformation efficiency of the present invention is high, reaches more than 97%, and the potassium transformation efficiency of current domestic ammonium nitrate and Repone K preparing potassium nitrate by means of double decomposition technique is generally 90%.In the present invention, nitric acid and neutralization with lime react and nitrocalcite and potassium sulfate replacement(metathesis)reaction all fully completely, therefore potassium transformation efficiency is high.
(2) energy consumption of the present invention and process cost low, energy consumption and the process cost of current domestic ammonium nitrate and Repone K preparing potassium nitrate by means of double decomposition technique are higher.Present invention process flow process is very simple, and easy to operate, saltpetre per ton needs evaporated water to be no more than 1.0 tons, thus energy consumption and process cost low.
(3) potassium nitrate product quality of the present invention is good, can reach the requirement of Chinese industrial saltpetre GB/T1918-2011 national standard premium grads, main content massfraction >=99.7% of saltpetre.
(4) raw material nitric acid, the Wingdale (or unslaked lime or white lime) selected of the present invention is all cheap and easy to get with potassium sulfate, and technique is simple, and energy consumption is low, and cost is low.
(5) gained terra alba of the present invention meets Food Additives Used in China-calcium sulfate standard GB/T 1892-2007 requirement, main content massfraction >=98.0%, can be used as foodstuff additive, also can be used as the high purity gypsums such as medical gypsum, mould gypsum, filler.
6, accompanying drawing illustrates:
Be raw material with Wingdale (or unslaked lime, white lime), nitric acid, potassium sulfate, produce industrial potassium nitrate and calcium sulfate technological process block-diagram as shown in Figure 1.
In neutralization reactor, add the circulation potassium mother liquor III returned, add the calcium carbonate impurity returned, add Wingdale (or unslaked lime, white lime), add salpeter solution, reaction generates ca nitrate soln; The ca nitrate soln generated passes through frit removal of impurities and washes with water, filters ca nitrate soln (containing washing water) send in double decomposition reactor, adds potassium sulfate reaction and generates calcium sulfate precipitation; Calcium sulfate feed liquid filtration washing obtains terra alba and potassium mother liquor I (containing washing water); Potassium mother liquor I is added calcium impurities in salt of wormwood removing solution, calcium impurities returns in neutralization reactor and recycles; Gained potassium mother liquor II concentrates through heating evaporation, then crystallisation by cooling separates out saltpetre, then centrifugation obtains saltpetre and mother liquor III, is finished industrial saltpetre after being separated saltpetre drying.Mother liquor III returns in neutralization reactor and recycles.
Below with nitric acid, unslaked lime, potassium sulfate for raw material, specifically introduce the present invention and produce saltpetre and calcium sulfate technique.
5, embodiment:
Embodiment 1:
In neutralization reactor, add 200 grams of water, add powdery unslaked lime 660 grams of (CaO massfraction>=85%, SiO
2massfraction≤3%, loss on ignition massfraction≤5%.Following quality all with), slowly add the salpeter solution of 1860 gram 68%, continuous stirring reaction, keep temperature of reaction 95 DEG C, solution ph is 6.5.By solution filtering and impurity removing, and with about 100 grams of 60 DEG C of water washings, add again in gained filtrate (containing washing water) potassium sulfate (massfraction >=50.0% of potassium oxide, massfraction≤1.50% of chlorion, following quality all with) 1850 grams, continuous stirring reaction, keep temperature of reaction 95 DEG C, filter to obtain calcium sulfate precipitation, and with about 500 grams of 90 DEG C of water washing calcium sulfate precipitations, record the main content massfraction 98.5% of sulfate dihydrate calcium deposit, containing potassium ion 0.25%.Separating calcium sulphate is precipitated gained potassium mother liquor I (containing washings) and add salt of wormwood stirring reaction, and adjustment control solution ph is 7.5, cross after filtering calcium carbonate impurity and obtain potassium mother liquor II, potassium mother liquor II heating evaporation is concentrated into 45 degree Beaume, cool to 20 DEG C again, obtaining saltpetre through centrifugation, being separated the mother liquid obtained III of saltpetre for recycling next time.Obtain 1520 grams, finished industrial saltpetre after being separated saltpetre drying, record containing saltpetre 99.85% (butt), water 0.08%, muriate 0.05%, carbonate 0.01%, vitriol 0.003%, water-insoluble 0.01%, water absorbability 0.25%, iron 0.000%.
Embodiment 2:
In neutralization reactor, add mother liquor III in embodiment 1, add calcium carbonate impurity in embodiment 1, add powdery unslaked lime 660 grams, slowly add the salpeter solution of 1860 gram 68%, continuous stirring reaction, keep temperature of reaction 60 DEG C, solution ph is 7.By solution filtering and impurity removing, and with about 100 grams of 60 DEG C of water washings, potassium sulfate 1700 grams is added again in gained filtrate (containing washing water), continuous stirring reaction, keep temperature of reaction 60 DEG C, filter to obtain calcium sulfate precipitation, and with about 500 grams of 60 DEG C of water washing calcium sulfate precipitations, record the main content massfraction 98.1% of sulfate dihydrate calcium deposit, containing potassium ion 0.45%.Separating calcium sulphate is precipitated gained potassium mother liquor I (containing washings) and add salt of wormwood stirring reaction, and to adjust solution ph be 7.0, cross after filtering calcium carbonate impurity and obtain potassium mother liquor II, potassium mother liquor II heating evaporation is concentrated into 50 degree Beaume, cool to 20 DEG C again, obtain saltpetre through centrifugation, being separated after saltpetre send drying machine drying and obtaining 1758 grams, finished product saltpetre, being separated saltpetre gained potassium mother liquor III (containing washings) for recycling next time.Record saltpetre containing saltpetre 99.90% (butt), water 0.1%, muriate 0.06%, carbonate 0.01%, vitriol 0.003%, water-insoluble 0.01%, water absorbability 0.24%, iron 0.000%.
Embodiment 3:
In neutralization reactor, add potassium mother liquor III in embodiment 2, add calcium carbonate impurity in embodiment 2, add powdery unslaked lime 660 grams, slowly add the salpeter solution of 1870 gram 68%, continuous stirring reaction, keep temperature of reaction 60 DEG C, solution ph is 6.5.By solution filtering and impurity removing, and with about 100 grams of water washings, potassium sulfate 1880 grams is added again in gained filtrate (containing washing water), continuous stirring reaction, keep temperature of reaction 80 DEG C, filter to obtain calcium sulfate precipitation, and with about 500 grams of 80 DEG C of water washing calcium sulfate precipitations, record the main content massfraction 98.8% of sulfate dihydrate calcium deposit, containing potassium ion 0.15%.Separating calcium sulphate is precipitated gained potassium mother liquor I (containing washings) and add salt of wormwood stirring reaction, and to adjust solution ph be 7.2, cross after filtering calcium carbonate impurity and obtain potassium mother liquor II, potassium mother liquor II heating evaporation is concentrated into 55 degree Beaume, cool to 46 DEG C again, obtain saltpetre through centrifugation, being separated after saltpetre send drying machine drying and obtaining 1949 grams, finished product saltpetre, being separated saltpetre gained potassium mother liquor III (containing washings) for recycling next time.Record saltpetre containing saltpetre 99.85% (butt), water 0.07%, muriate 0.05%, carbonate 0.00%, vitriol 0.001%, water-insoluble 0.01%, water absorbability 0.23%, iron 0.000%.