Разработка технологии получения фосфорных и сложных азотнофосфорных удобрений на основе фосфоритов Центральных Кызылкумов

Аннотация

Topicality and demand of the subject dissertation. One of the most topical problems in the world is the rapid development of agriculture and its needs in mineral fertilizers. Through the use of mineral fertilizers 40-50% increase in crop’s yield on average is provided. Uzbekistan has a large chemical industry to ensure the needs of agriculture in nitrogen, phosphate and potash fertilizers. In the Republic the products range of enterprises producing phosphorus fertilizers, consists mainly of complex nitrogenphosphorus fertilizers. They are widely used for bringing in with the sowing and fertilizing. The phosphorus fertilizers are mostly effective when they are used just under autumn plowing. Therefore, the development of new technology of single concentrated phosphate fertilizers is an important task. The complex nitrogen-phosphorus fertilizers’ production requires modernization. The fact is that their manufacture is based on the decomposition of sulfuric acid to yield the phosphate raw phosphoric acid. At the same time phosphogypsum as industrial wastes is generated. Therefore, the current phosphate processing, in which instead of gypsum a calcium nitrate is formed being effective fertilizer, especially in saline soils, becomes an urgent deal. Processing of calcium nitrate into the liquid fertilizer as the cheapest form of mineral fertilizer becomes urgent too. The development of a thermostable form of ammonium nitrate is also an urgent problem of the chemical industry. In Uzbekistan, the ammonium nitrate is produced in quantity of more than 1 million 700 thousand tones per year. Because of the explosions in violation of the safety of its production and storage of the task is stated to create on the basis of ammonium nitrate the fertilizer, preserving its agrochemical efficiency with significantly greater resistance to external influences and therefore at risk of explosion. The present research is focused on the implementation of the resolutions of the President of the Republic of Uzbekistan the №PR-1442 dated December 15, 2010 y. «On the priorities of industrial development of Uzbekistan in 2011-2015» and the №PR-2151 dated March 14, 2014y. «On measures to ensure agricultural fertilizers in 2014 year», aimed at accelerating the introduction to the industries of modern scientific achievements and advanced innovative technologies, the expansion of markets for products based on the diversification of production, increase of production of export-oriented, competitive industrial products based on in-depth and high-quality processing of domestic raw materials, as well as the provision of agricultural fertilizers. On this basis, to solve the above mentioned problems it requires to carry out new researches and developments, aimed at involving into the processing of poor phosphate raw materials, to upgrade technology of complex nitrogen-phosphorus fertilizers, to increase the production of phosphate fertilizers, to expand their range of production, to reduce their costs, as well as to establish of export-oriented thermostable ammonium nitrate’s development. Purpose of research is to develop technologies for the production of single phosphate fertilizers, nitrogen-phosphorus and nitrogen-calcium liquid fertilizers, thermostable ammonium nitrate by using the Central Kyzylkum low-grade phosphate raw materials. Scientific novelty of the dissertation research consist in the following: the optimum conditions of the interaction processes of low-grade Central Kyzyl Kum phosphorites with phosphoric acid gypsum slurry are studied and the technology of the single phosphorus fertilizers was created; the liquid nitrogen-calcium and solid nitrogen-phosphorus-calcium fertilizers are produced by mean of removing calcium nitrate from nitro-calcium phosphate pulp that obtained decomposition Central Kyzylkum phosphorites with nitric acid. The correlation between the composition and properties of liquid nitrogen-calcium fertilizers depend on the norm of nitric acid and the weight ratio of nitrate ammonium calcium solution to ammonium nitrate, urea and a solution of urea-ammonium nitrate was revealed; it was determined that the phosphate additive does increase the temperature of modification’s transformation of ammonium nitrate IV —» 111, does decrease thermal effects of modification’s transactions, does increase decomposition temperature on 29-39°C, does reduce crystal sizes of fertilizer’s granules, as the result the thermal stability of nitrogen-phosphorus fertilizer does increase; the technology of novel fertilizers containing of assimilable forms of P2O5 and CaO on the basis of introduction of various types of high calcareous Central Kyzylkum phosphorites into ammonium nitrate melt was created. Conclusion The thesis contains the solution of very relevant scientific and technical problems in the field of chemistry and chemical technology of mineral fertilizers, laying a theoretical and applied research, ensuring development of resource-saving technology for new types of single phosphorus, nitrogen-phosphorus and liquid nitrogen-calcium fertilizers based on complex processing of the Central Kyzylkum phosphorites. The main scientific and practical results obtained in the performance of the thesis are as follows: 1. The study of graphoanalitical analysis of CaO^Os-SOs-fTO and CaO-P2O5-N2O5-H2O systems has theoretically proved the process of interaction between the Central Kyzylkum phosphorites with phosphoric acid-gypsum pulp and nitric acid with reduced norm. New scientific evidence obtained allows to justify and to predict the flow conditions and processes of single nitrogen-phosphorus-calcium fertilizers during the processing of Kyzylkum phosphorites and to find optimal compositions. 2. The interaction between different types of the Central Kyzylkum phosphorites and a phosphoric acid gypsum pulp obtained by the decomposition of washed calcined concentrate with sulfuric acid, in the range of mass ratios PAGS:PR = 100 : (25-70) was investigated. Ratios and concentrations limits of the reactants involved in the process were established. It is shown that the optimal ratio of PAGS:PR is 100 : (25-30), in which single fertilizer with a maximum content of digestible and water-soluble form of P2O5 and CaO can be obtained. To improve the marketable properties of the product in sulfo-calcium phosphate slurry it is recommended to add the sour runoff - absorption solution of EPA production. 3. The advanced technology of nitrogen-phosphorus-calcium containing and liquid nitrogen-calcium fertilizer production by partial release of calcium nitrate from ammoniated nitrogen-calcium phosphate slurry by various options was developed. Il is shown that in the proposed NPCa fertilizers content of P2O5 is 7-10% higher than in NCPF (nitrofos), which is produced at JSC «Samarkandkimyo». The studies have been conducted on the processing of NACS, which is the liquid phase of nitrogen-calcium phosphate slurry, in various marks of LNCF. The different composition of LNCF was obtained with evaporation method of NACS and neutralization with ammonia depending on the norm of nitric acid. And by adding ammonium nitrate, urea and CAN solution to NACS a wide range of LNCF with high nitrogen content was obtained. 4. The possibility of obtaining of NPF on the basis of interaction of different types of the Central Kyzylkum phosphorites with a melt or concentrated solution of AN was studied. The kinetics of decarbonization and activation of ordinary phosphorite flour in AN melt were studied. It is shown that a high degree of decarbonization and activation of phosphate raw materials in NPF observed after 20 minutes of initial regents’ interaction. It was found out that the introduction of phosphate additives into ammonium nitrate significantly increases the hardness of granules, i.e. on average for 2.0-5.5 times. Adding phosphorite powder to an amount of 5% in terms of P2O5 to AN melt reduces porosity of its granules from 9.15 to 7.08%. Caking of NPF containing 3.0-5.04% P2O5 is 1.71-1.87 kg/cm2 that 2.5-2.7 times less than the net AN caking. 5. The effect of phosphate additives on the modificational conversions of ammonium nitrate was studied. Determined that for AN transformation temperature IV—>111 is 44.8°C, and with the addition of phosphate raw materials in the amount of 1.05-5.04% P2O5 to AN the temperature of this transformation increases from 53.7 to 56.6°C. This reduces the melting temperature and crystallization of AN. Rising the transition temperature IV —> 111 contribute to the preservation of high strength and to reduction of NPF granules caking during transport and storage in hot climates. Thermal effects of modificational transitions of NPF were defined. It is shown that their values are much lower than the initial AN’s heat of transition. Consequently, they occur with minimal thermal effects and the additive has an inhibitory effect on modificational transformation and at the transition points of transformation does not proceed until the end, and that helps to reduce the level of granules’ destruction, sealing their structure and thus the preservation of increased strength. 6. It was shown that when AN is heated the phosphate additives have beneficial buffering action and stabilize its pH value. The temperatures of the beginning of their decomposition and energy of their activation process were determined. It was found out that the onset temperature of thermal decomposition of the AN as part of NPF compared to net AN depending on the amount of phosphorite additives, increased from 29 to 39°C. It is shown that the activation energy of NPF decomposition, containing from 1 to 5% P2O5 varies between 46.6-51.6 kcal/mol, which is 4.7-9.7 kcal/mol higher than the activation energy of pure AN decomposition. This indicates a significant increase in thermal stability of phosphatized AN. Conducted electron-microscopic study of micro-structures of NPF granules shows that the phosphate additive reduces the size of ammonium nitrate crystals. Phosphorite settles into the pores and microcracks, filling them, forming a more perfect surface and internal structure of the NPF granules. By conducting of pilot tests in the workshop number 3 at JSC «Navoiazot», the losses of ammonium and nitrate nitrogen at release of developed nitrogenphosphorus fertilizer were identified. Losses per 1 t of NPF were: in the form of NIL - 0.52 kg/t, and in the form of NH4NO3 - 0.41 kg/t, i.e. overall loss at the mixing and granulation stage of NPF in terms of nitrogen amounted to 0.572 kg/t which is the allowable value. 7. Physicochemical and rheological properties of solutions, pulps and melts which were formed at various stages of technological process of the Central Kyzylkum phosphorites processing were determined. With the use of X-ray methods and 1R spectroscopic analysis the salt composition of the products was established, also the physicochemical and product properties of single, nitrogenphosphorus and NPCa fertilizers were studied. 8. Based on the results of the laboratory experiments, data of tests carried out at the model installation and at a pilot works the technological scheme was designed and material balance of production of singles, nitrogen-phosphorus, NPCa and liquid nitrogen-calcium fertilizers was composed. The results of the physical, chemical and applied researches on the decomposition of the Central Kyzylkum phosphorites with phosphoric acid-gypsum pulp formed the basis for the development of technology for single-phosphorus fertilizer, which has been successfully tested at JSC «Ammofos-Maxam» with the release in 2009 of 60 tons, and in 201 1, 100 tons of a new type of fertilizer. Production technology of NPF based on ammonium nitrate melt and the Central Kyzylkum phosphorite flour is implemented at JSC «Navoiazot». Since the beginning of 2009 to the present time more than 300 thousand tons of new type of NPF in the amount of 165 billion soums were produced. 9. Technical and economic calculations were fulfilled for the single, NPCa and liquid nitrogen-calcium fertilizers. In organizing the production of single phosphorus fertilizer the norm of sulfuric acid per 1 ton of 100% P2O5 compared to the production of suprefos reduced to 30-35%. Wholesale price of granular NPCa fertilizer is 565511 soums compared to NCPF on 118643 soums cheaper. Wholesale price of LNCF, which is obtained with the addition to NACS ammonium nitrate and urea is 192722 and 285548 soums respectively. With the release of 100 thousand tons of NPF per year only due to the absence of special protection and support more than 2 billion soums are saved. 10. Agrochemical tests of derived fertilizers at cotton plants’ fields in the microlysimetric, pushed plot and field conditions were held. These results indicate that the efficiency of the developed agrochemical fertilizers is close to the efficiency of mixtures of traditional fertilizers with an equivalent amount of nutrients.