Method for preparing potash fertilizer or sylvite from potassium-rich rock-lime hydrothermal method
The present invention relates to a method for preparing potassium fertilizer (potassium salt) by using potassium-rich rock-lime hydrothermal method.
Potassium-rich rock (insoluble potassium ore) refers to a special class of rock that is composed primarily of authigenic high-potassium silicate minerals. In the rock, the potassium-containing minerals mainly comprise potash feldspar, illite, glauconite, mica minerals, etc., and the chemical components are K2The content of O is higher, and is generally between 8 and 16 percent. China reserves abundant potassium-rich rock resources and is widely distributed. According to the estimation of experts of the regional mine department, the reserves of the potassium-rich rocks in the whole country are converted into K2O is about 50 million tons or more.
China is a country with very short soluble potassium salt resources, and in order to solve the serious shortage problem of agricultural potassium fertilizers, the method is combined with Israel to develop soluble potassium salt ores of salt lakes of the Qinghai and Chaohan, a large amount of KCl is imported from abroad every year, and the method is planned to be combined with peripheral countries (such as Thailand and the like) to develop local soluble potassium salt ores, but the problem cannot be completely solved. If the potassium fertilizer is successfully prepared by using the potassium-rich rock and can be put into production in large quantity, great contribution is made to the sustainable and healthy development of agriculture in China.
The resource of soluble potassium salt is rich in foreign industrial developed countries (such as Canada, France, Germany, Russia, America and the like), so research on preparing potassium fertilizer by using insoluble potassium ore is relatively less developed. The research of extracting potassium from potassium-rich rock in China begins in the fifties and is increasingly concerned by people in the last decade. In conclusion, at present, there are three ways to prepare potash fertilizer by using potassium-rich rock at home and abroad, namely, a calcining method or a sintering method, a hydrothermal chemical method and a microbial decomposition method.
1. By calcining or sintering processes
The method has more researches, and the principle is that the potassium-rich rock and other ingredients are calcined under the high-temperature condition to destroy the structure, so that the potassium and other elements form soluble potassium salt to achieve the aim of extracting the potassium. Among many methods, the alkali fusion method is dominant. The alkali fusion method refers to mixing feldspar minerals with alkali (NaOH, Na)
2CO
3) Or/and CaCO
3Co-melting at high temperature, immersing slag in water, dissolving potassium metaaluminate, and carbonizing to obtain K
2CO
3And Al (OH)
3The reaction can be expressed as:
the research institute of mine design in chemical industry department adopts potash feldspar and limestone 1: 2.61, and makes them melt at 1330 deg.C, and after the clinker is ground, the potassium-containing solution is leached to prepare K2CO3And the residue is used for preparing cement. The Marhongwen et al of China geological university adopts potassium-rich volcanic rock mineral powder and Na2CO3Calcining at 830 deg.C for 1.5-2 hr at 1: 1.1-1.4, and using the leaching solution to prepare K2CO3And the residue is used for synthesizing zeolite. The report of Wangxuan university chemical industry institute Wangxingsheng adopts potash feldspar, gypsum and limestone as the ratio of 1: 0.39: 3, and 2.5 percent of 2 is doped at the same time#The assistant reacts for 3 hours at 900 ℃, and the dissolution rate of potassium can reach 93 percent. Sichuan people adopt mung bean rockCalcining limestone and NaCl in the ratio of 1 to 0.6 at 800-820 deg.c, and soaking clinker to extract KCl. KCl is extracted by a salt chlorination roasting method in a potash fertilizer factory in Feng county of Jiangsu province, and the roasting temperature is up to 1900 ℃. It has also been reported that the potassium conversion rate can reach 66% by mixing the potassium-containing rock with limestone and calcium oxide and then roasting at 700 deg.C for 1 h; smelting the mixture of potassium feldspar, limestone, dolomite, fluorite and coke at 1500 deg.C to extract K2CO3(ii) a The potassium-rich shale, the apatite, the dolomite and the coke are melted at the temperature of 1200-sand at 1300 ℃ to obtain the calcium-magnesium-phosphorus-potassium fertilizer. K-containing rock rich in potassium is added in cement production in Beijing colored glaze river cement factory and other units, and at 1300-1500 deg.C2CO3And K2SO4The kiln dust can be used for obtaining the kiln dust potash fertilizer by a trapping method. The former Soviet Union uses nepheline to extract potassium, but mainly prepares alumina and produces potassium salt as a byproduct.
2. Hydrothermal chemical process
The principle is that chemical products such as acid and alkali are adopted to decompose potassium-rich rock in solution, so as to achieve the purpose of dissolving and separating potassium ions. It can be subdivided into acid and alkaline processes.
Acid process
The potassium-rich rock containing illite and hydromica reacts with acid to release most of potassium in the rock, but the acid (except hydrofluoric acid) is difficult to dissolve out potassium in the potassium feldspar crystal lattice. It is reported that illite is crushed and then calcined at 800-850 ℃ for 2H, and then 30% H is used2SO4Leaching the solution at 70-80 deg.C at a liquid-solid ratio of 3: 1 to obtain K2SO4. The Tianjin design institute of chemical industry and Wuan chemical fertilizer plant in Hebei province adopt a pressurized acid dissolution method to extract potassium from illite. The Changsha chemical mine design research institute adopts H2SO4And an auxiliary agent (possibly fluoride), decomposing the potassium feldspar at 100 ℃ to extract potassium, and recycling the auxiliary agent. There are reports that strong acids have been usedBy leaching in H2SO4In the presence of the potassium salt, potassium in the feldspar is dissolved out by hydrofluoric acid to prepare the potassium salt.
Alkaline process
Alkaline process for extracting potassiumVery few studies have been made. Japanese has adopted 100 ℃ and 400 ℃ NaOH-Ca (OH)2The mixed solution is used for extracting potassium from the potassium feldspar under high pressure. Cherman found that, at 200 ℃ of 150-. According to the reports of 24 days 1 month in 1994 of the Chinese science newspaper, the Yongjie professor of the university of east China adopts a pressurized lime method to carry out potassium extraction research on two potassium feldspars in Hunan province and Jiangsu province, but the detailed conditions are not reported.
3. Microbial decomposition method
The K-907 strain screened by nuclear radiation mutagenesis is taken as an activating agent by units such as geological mechanics research institute of Chinese geological academy of sciences, so that the structural potassium in glauconite and illite is converted into soluble potassium which can be absorbed and utilized by plants. The research on the dissociation of potassium in the potassium feldspar by silicate bacteria is carried out by the Shenyang application ecology institute of Liaoning microbiology institute and Chinese academy. The biological potassium fertilizer 'giant microbial potassium' is researched by the institute of microbiology of academy of sciences in Hebei province. The research of biological preparation of potash fertilizer has also been carried out by the Chinese academy of agricultural sciences.
The invention aims to provide a novel method for preparing potassium fertilizer (sylvite) from potassium-rich rock, which reduces energy consumption and cost.
Since 1996, the inventor of the invention develops a research on extracting potassium from potassium-rich rock, and creates a new process for extracting potassium by a lime hydrothermal method in a semi-wet state on the basis of referring to potassium extraction experiences at home and abroad. The reaction is carried out under a static condition, the energy consumption can be greatly reduced, and KOH and K are obtained2CO3And K2SO4An article of manufacture. If the slag can be further reasonably utilized, the cost can be greatly reduced, and a new way is created for solving the problem of serious deficiency of the potash fertilizer in China.
The invention provides a method for preparing a potash fertilizer (sylvite) from potassium-rich rock, which comprises the following steps:
(1) crushing the potassium-rich rock and lime to below 2 cm;
(2) conveying potassium-rich rocks and lime fragments of less than 2cm to a ball mill for wet ball milling according to the proportion of 1: 0.8-1 of potassium-rich rocks and lime, wherein when the wet ball milling is carried out, the ratio of solid to liquid is 1: 0.75-1.20, and grinding the materials to be less than 200 meshes through the wet ball milling;
(3) conveying the ground materials into a material storage device, adjusting the water content to ensure that the solid-liquid ratio is 1: 1-3, and stirring and mixing;
(4) transferring the material to a high-pressure reaction kettle, introducing high-pressure steam, performing hydrothermal reaction at the temperature of 130-250 ℃, preferably 170-190 ℃, and keeping the temperature for 5-24 hours, preferably 7-12 hours to obtain KOH;
(5) the obtained KOH is used to prepare potassium salt.
In the above method of the present invention, the reaction vessel may be opened after the high-pressure reaction is completed, the reactant may be taken out for filtration, the slag may be comprehensively utilized, and the KOH-containing extract may be fed to the evaporator. The KOH solution is then concentrated in an evaporator, together with unreacted Ca (OH)2And CaSO4Separating out the residue. Then, the second filtration is carried out to remove the residue, so as to obtain the KOH solution with higher concentration.
In the above process of the present invention, the step of using the obtained KOH to prepare the potassium salt may be carried out by introducing CO into the KOH concentrate2Gas (or addition of H)2SO4) Then evaporating and crystallizing to obtain K2CO3(or K)2SO4) And (5) producing the product.
In the above method of the present invention, the step of crushing the potassium-rich rock, lime and gypsum may be performed by using a jaw crusher.
The extraction of potassium using the method of the invention averaged 62.10% in 8 trials.
The method of the invention has the following characteristics:
(1) japanese scholar uses NaOH-Ca (OH)2The mixed liquor is used for extracting potassium from the potassium feldspar under high pressure, and although the high potassium dissolution rate can be obtained, the filtrate contains a large amount of Na after the reaction+In order to obtain potassium salt products, Na is required+K+The separation is complicated in process and high in cost. The Na is not contained in the process+Substance, use is made of Ca-containing2+The material can simplify the separation and purification process and easily obtain a purer sylvite product.
(2) The process adopts wet ball milling, can combine two procedures of fine milling and material mixing, fully mixes several materials participating in reaction in the grinding material, and can also achieve better dustproof effect.
(3) The amount of water used in the formulation is extremely important, and too much or too little water is detrimental to production. The process water has a low consumption (a solid-liquid ratio is 1: 1-3), so that on one hand, the potassium dissolution effect is ensured, on the other hand, the amount of materials participating in the reaction can be increased in a reaction kettle with the same volume, the material treatment capacity is improved, and the production scale is enlarged.
(4) When large-scale industrial production is carried out, a horizontal high-pressure reaction kettle can be adopted, materials are fully mixed after being finely ground, so that stirring is not needed in the kettle, the dissolution reaction can be carried out under a static condition, the operation is convenient, the energy consumption is low, and the production cost can be greatly reduced.
(5) When the production process is researched, the work is focused on the potassium dissolving-out process in potassium-rich rock, on one hand, the following potassium salt preparation process (from a filtering section) has a mature process which can be used for reference, and the innovative components are not large, on the other hand, the potassium dissolving-out process is only regarded as the production process of the silicon-calcium-potassium mixed fertilizer, and the silicon-calcium-potassium mixed fertilizer is an invention and an innovation, is particularly suitable for southern areas of China, is greatly beneficial to crops, and has lower production cost.
EXAMPLES starting materials
Potassium-rich rock: collected from south mountain of Miyun county, Beijing city, its chemical composition (%): SiO 22TiO2Al2O3(Fe2O3+FeO) MnO2CaO MgO K2O Na2O P2O5The loss on ignition totaled 63.090.7115.69 4.41 0.02 0.15 0.37 12.79 0.22 0.04 1.93 99.42
X-ray powder crystal diffraction analysis indicates that the potassium-rich rock mineral mainly comprises potassium feldspar, and the other parts comprise quartz and the like.
Lime: CaO content is 97%, and the CaO is purchased from the market.
(1) Putting 5.000g of potassium-rich rock coarse powder and 5.000g of lime coarse powder into an agate mortar, adding about 10ml of water, fully grinding to ensure that the granularity of the materials is below 200 meshes, uniformly mixing, transferring the materials into a plastic vessel, and adding a little water to ensure that the solid to liquid ratio is 1: 3;
(2) placing the plastic vessel containing the sample into a high-pressure reaction kettle, and keeping the temperature at 190 ℃ for 7 hours;
(3) after the high-pressure reaction kettle is cooled, taking out the plastic vessel, transferring the reaction product into a filter, filtering, and obtaining 100ml of potassium-containing extracting solution in the test by adopting excessive water in order to extract out soluble potassium in the reaction product as completely as possible;
(4) diluting the potassium extraction solution by20 × 10 to 200 times (two-stage dilution), measuring the potassium and sodium concentration in the solution sample by flame photometry, and converting the measurement result into K2O and Na2The O concentrations are 3960mg/l and 32mg/l, respectively, and Na is added2O/K2The concentration ratio of O is 0.0081, which is very beneficial to preparing pure sylvite later.
(5) K in potassium-rich rock2O12.79%, 5 g of powder sample may contain K2O639.5 mg, K is converted from the extract2The O concentration is 3960mg/l, 100ml contains K2O396.0 mg, therefore, the extraction rate of potassium from potassium-rich rock was 396.0 ÷ 639.5 × 100% ═ 61.92%.
(6) After the potassium-extracted slag is air-dried, the main phase is hydrated silicate through X-ray powder crystal diffraction analysis.
Mixing potassium-extracting solutions obtained in multiple tests, evaporating and concentrating in evaporator, and filtering to remove precipitate (mainly unreacted Ca (OH))2) Introducing CO into the obtained clear liquid2Gas (or addition of H)2SO4) And then evaporating and crystallizing to prepareTo obtain K2CO3(or K)2SO4) And (5) producing the product. The product phase was confirmed by X-ray powder diffraction analysis.
According to the research report of the Japanese scholars of Yuanshanyilang, calcium silicate hydrate can be used as a heavy metal adsorption material, and CuSO is utilized4The solution was subjected to qualitative tests, confirming this property. The comprehensive utilization of slag is under further study.
Instrument used in experiment
(1) Flame photometer HG-3 model, manufactured by Beijing environmental protection Instrument factories;
(2) x-ray diffractometer model Y-3, manufactured by Dandong instruments Ltd.