Title of Invention

"A PROCESS FOR MAKING SLOW RELEASE PHOSPHATE FERTILIZER"

Abstract

A process for making slow release fertilizer, which is fused calcium magnesium phosphate (FCMP) fertilizer, from low-grade rock phosphate ore (LGO) and serpentinite is provided. To conserve the depleting and limited rock phosphate resources of our country, the present invention provides a process to utilize the LGO to the maximum possible extent and utilize serpentinite waste of decor stone industry. The slow release fused calcium magnesium phosphate fertilizer having high citrate solubility of P2O5 content is produced from low-grade rock phosphate ore by fusing with serpentine, which is available in abundance in Udaipur, Rajasthan.

Full Text

Field of the invention The present invention relates to a process for making slow release phosphate fertilizer. The slow release phosphate fertilizer refers to Fused Calcium Magnesium Phosphate/ Fused Magnesium Phosphate (FCMP/FMP). More particularly, the invention relates to a process for making FCMP from "Low grade rock phosphate ore (LGO)" available from Jhamarkotra mines of RSMM Ltd., Udaipur and serpentinite. Background and prior art of the invention Reference may be made to a US patent number 6,451,276, which discloses a method of recovering elemental phosphorus from a sludge that contains water, dirt, and elemental phosphorus. In the first step, the sludge is melted. A mixture is formed of the melted sludge and about 0.5 to about 5 wt % of an oxidizing agent, based on the weight of elemental phosphorus in the sludge, and about 75 to about 580 wt % water, based on the weight of the sludge. The mixture is stirred until a continuous elemental phosphorus phase forms. The purified phosphorus phase is separated from the mixture. Reference may be made to a Japanese application numbered 08-188462, which deals with a method of production of fertilizer which functions as a promoter for humification ripening of organic matter and enables the preparation of well-balanced soil by using calcium cynamide and fused magnesium phosphate as the major components of the fertilizer. In this application, FMP is used as one of the source materials and is not the end product. Reference may be made to another US patent numbered 5,158,594, which discloses preparation of phosphated or nitro-phosphated fertilizers through solubilization of phosphate rock. This method does not involve the use of an electric furnace. The final product is phosphoric acid made from phosphate rock by acid digestion. Neither gypsum slurry nor solubilization of phosphate rock are involved. Reference may be made to another US patent number 3,993,733, which involves preparation of food grade alkali metal phosphates by a sequence of steps. The resulting wet process phosphoric acid contaminated with impurities has extensive use in the fertilizer industry. But the cited patent does not produce direct FCMP/FMP, which is produced by the process of the present invention. The cited patent is for alkali metal phosphate of food grade made by a wet process, which is still another process of making phosphoric acid that is subsequently used for fertilizer industry. Reference may be made to another US patent numbered 4,284,614, which involves a process for the production of high purity phosphoric acid from high alumina phosphate pebble rock, the said patent talks about production of phosphoric acid from phosphate rock and high alumina pebble which is a byproduct of phosphate rock mining operations, which can be used as one of the components of fertilizers. None of the patents reported here or anywhere else teach any direct method for the production of FCMP for fertilizer applications. The present invention is solving this problem of prior art by providing fertilizer grade FCMP from low-grade rock phosphate ore and serpentinite. Objects of the invention The primary object of the present invention is to provide a process for making slow release phosphate fertilizer to reduce import of high-grade rock phosphate and fertilizer to meet the demands of greater food production. Another object of the present invention is to provide a process for making Fused Calcium Magnesium Phosphate (FCMP) using "Low grade rock phosphate ore (LGO)" and waste serpentinite rocks. Still another object of the present invention is to provide a process for making Fused Calcium Magnesium Phosphate (FCMP) that can be used as fertilizer. Yet another object of the present invention is to provide a process for making Fused Calcium Magnesium Phosphate (FCMP), which can be used as fertilizer for acidic soils and a variety of crops. Statement of the invention Accordingly, the present invention provides a process for making slow release fused calcium magnesium phosphate fertilizer, the said process comprising the steps of crushing low grade rock phosphate ore received from the mines; crushing serpentinite and optionally quartz to a size in the range of -10 + 5 mm and storing separately; weighing the two ingredients and mixing proportionately to obtain the required composition of said fertilizer; feeding the composition to a furnace for fusion; fusing the composition in a furnace to obtain a melt; quenching the melt as obtained to a temperature in the range of 30-50 degree C; drying the quenched melt in a drier and grinding to 150 microns to obtain the desired fused calcium magnesium phosphate fertilizer. Detailed description of the invention At the outset of the description that follows, it is to be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only exemplary embodiment and without intending to be understood as exemplary teaching of the invention and not to be taken restrictively. The starting material for making FCMP/FMP is "Low grade rock phosphate ore (LGO)" available from Jhamarkotra mines of RSMM Ltd., Udaipur. A typical range of constituents of LGO is given in Table-I. A minimum of 16 percent P2O5 is required for making FMP. Other additives suggested for improving fusion and citrate solubility are "Serpentinite" and optionally "Quartz". The proposed product may be named either "Fused Calcium Magnesium Phosphate (FCMP)" or "Fused Magnesium Phosphate (FMP)" or both. To obtain good fusion and citrate soluble P2O5, MgO to SiO2 ratio should be around 0.95 in the feed mix. Table-I Constituents' range of raw materials: (Table Removed ) Table-II Details of the recipe that was fused successfully: (Table Removed ) %CS P2O5 = (Citrate soluble P2O5 content in the sample/Total content of P2O5 in the sample) x 100 DESCRIPTION OF THE PROCESS: Preparation of feed mix: Low-grade ore (LGO) received from the mines (-150 mm size) is crushed to -10 +5 mm in two-stage crushing and stored. Serpentine and quartz (if used) are also crushed to -10 +5 mm and stored separately. These materials are weighed and mixed proportionately to give required composition and fed to an electric furnace for fusion. An optional pre-heating of reactants by solar / conventional energy may be done before feeding to the furnace for fusion. The ratio in terms of amount of rock and serpentine mixed varies from 10:3 to 10:6. Serpentinite used may be obtained from deco-stone industry waste of Kherwara near Udaipur city. Quartz, if added, may be obtained from reef quartz of low commercial value available around Udaipur or from the siliceous phosphate tailings/ore of Maton mine. Fines may be agglomerated by pelletization to give required size along with additives and fed along with the feed mix or alternatively used. The fines may be used for direct fertilizer application in acidic soils (as per present practice). Fusion process: The feed mix prepared is fed to a three-phase electric furnace and fused at a temperature within the range of 1400 to 1500 degree C. The material is retained for a time period of 15 to 30 minutes in the furnace at this temperature to convert the mineral apatite to alpha-tri-calcium-phosphate. The melt is ready for quenching and poured into running water-quenching trough. Quenching of the melt: The melt is quenched quickly with high pressure water jets and flowing water in a trough to room temperature. Preparation of the product: The quenched melt is heaped to drain out water. Wet product FCMP/FMP, which is granular and porous, is dried in a rotary drier / solar tunnel dryer to less than 1 percent moisture. The dried product is ground to 80 percent -100 µ (micron) in a ball mill and packed in poly-propylene bags, which contains 14 percent P2O5 minimum and 75 percent citrate soluble P2O5. The gaseous by-products: The flue gases contain mainly CO2 and minor quantities of HF, SiF4. The gases are passed through scrubbing chambers where it is scrubbed with water spray. HF and SiF4 get dissolved in water forming H2SiF6. The gas leaving the scrubbers contains high concentration of CO2 that can be compressed and cooled to make dry ice or liquid CO2 or for other commercial use. Metal by-products: In the lower zone of the furnace, ferro phosphorous (iron phosphide) compounds are formed as metal by-products that can also be utilized. The fertilizer produced by the present invention is used widely for acidic soils and a variety of crops. It not only contains essential primary nutrient phosphorous but also secondary nutrients CaO and MgO in good amounts. It also contains silica, which makes soil porous. As FCMP is insoluble in water, it does not get drained along with water when fields are watered. It is long lasting and releases P to the plants in a sustained manner. In a preferred embodiment of the present invention, the low grade rock phosphate ore used is having P205 in the range of 14 to 17.5 percent, CaO in the range of 43 to 48 percent, MgO in the range of 10 to 12 percent, SiO2 in the range of 4 to 6 percent and R2O3 in the range of 1 to 2 percent, wherein R is aluminum and/ or iron. In another embodiment of the present invention, the serpentine used is having 24.50 percent MgO, 45.20 percent SiO2, 16.00 percent R2O3 and 14.00 percent of H2O, wherein R is aluminum and/or iron. In a further embodiment of the present invention, the ratio of rock and serpentine mixed is in the range of 10:3 to 10:6 by weight. In yet another embodiment of the present invention, the temperature used for fusion is in the range of 1400 to 1500 degree C. In another embodiment of the present invention, the time period for which fusion takes place is in the range of 15 to 30 minutes. In still another embodiment of the present invention, the quenched melt is dried to a moisture content of less than 1 percent to obtain the desired product. Advantages of the invention: l.The process utilizes available waste serpentine as source of magnesium rather than the more expensive and difficult to fuse olivine that is being used in conventional methods; part of magnesium is also available from the dolomite source rock. 2.The present process does not result any solid waste whereas in flotation process, 50-55 percent waste is generated while making concentrate and 20 percent P2O5 is lost with the waste along with other nutrients - CaO, MgO, SiO2 etc. 3.The process generates by-products viz. ferro-phosphorous (Fe2P), hydro-fluosilicic acid, ammonium carbonate, solid carbon dioxide (dry ice) / compressed carbon dioxide. 4.FCMP obtained is water insoluble, so it does not get drained along with water when the crop fields are watered. 5.FCMP is long lasting and releases phosphorous to the plants in a sustained manner. 6.It does not deteriorate during storage and does not corrode packing material. Examples The following examples are for the purposes of illustration only and therefore should not be construed to limit the scope of the present invention: Example I Serpentine was taken from the locally available waste product of the decor stone industry. After retaining the constituents at melting temperature, the fused substance has been quenched. Various proportions of serpentine and optionally quartz were tried to study fusion and citrate solubility of the products. LGO, Silicate Tails (BCT, bulk circuit tails) and FCT were obtained from Jhamarkotra beneficiation plant direct from the process streams. These materials are 80 to 90 % -200-mesh size. Other additives were ground to 80% - 150 mesh before addition. Silica-graphite crucibles were used to fuse the hand-mixed material. A three-phase high temperature electric furnace with digital temperature control was used to carry out fusion. After fusion, the material was quickly quenched in a steel tank with flowing water facility. A granular, glassy Fused Calcium Magnesium Phosphate (FCMP) was obtained. Example II The product FCMP was ground to 80% -150 mesh size to analyze for citrate solubility. Neutral ammonium citrate was used to determine the solubility. Effect of temperature and effect of additives were studied to obtain good fusion and maximum citrate soluble P2O5 in the product. Carbon dioxide liberated during fusion was collected for its industrial utilization. Fluoride evolved at fusion and quenching stages was also collected by scrubbing with water for the production of fluosilicic acid. Composition and purity of the final product: Constituents Amount (percent Wt) P2O5 12 to 18 CaO 30 to 40 MgO 16 to 20 SiO2 20 to 25 Fused calcium magnesium phosphate contains about 40 to 75 percent CS (citrate soluble) P2O5 of the total. Micro-nutrients Fe, Mn, Cu, Zn etc. in ppm We Claim: 1. A process for making slow release fused calcium magnesium phosphate fertilizer, the said process comprising the steps of: a) crushing low grade rock phosphate ore received from the mines; b) crushing serpentinite and optionally quartz / siliceous phosphate to a size in the range of -10 + 5 mm and storing separately; c) weighing the ingredients of steps (a) and (b), and mixing proportionately to obtain the required composition of said fertilizer; d) feeding the composition as obtained in step (c) to a furnace for fusion; e) fusing the composition of step (d) in a furnace to obtain a melt; f) quenching the melt as obtained in step (e) to a temperature in the range of 30-50 degree C; g) drying the quenched melt of step (f) in a solar drier to obtain the desired fused calcium magnesium phosphate fertilizer. h) grinding the material of step (g) to 80 percent 150 microns. 2. A process for making slow release phosphate fertilizer as claimed in claim 1, wherein the low grade rock phosphate ore used in step (a) is having P2O5 in the range of 14 to 17.5 percent, CaO in the range of 43 to 48 percent, MgO in the range of 10 to 12 percent, SiO2 in the range of 4 to 6 percent and R2O3 in the range of 1 to 2 percent, wherein R is aluminum and/or iron. 3. A process for making slow release phosphate fertilizer as claimed in claim 1, wherein the serpentinite used in step (b) is having 24.50 percent MgO, 45.20 percent SiO2, 16.00 percent R2O5 and 14.00 percent of H2O, wherein R stands for aluminum and/or iron. 4. A process for making slow release phosphate fertilizer as claimed in claim 1, wherein the ratio of low-grade rock phosphate ore and serpentinite mixed in step (c) in the range of 10:3 to 10:6 by weight. 5. A process for making slow release phosphate fertilizer as claimed in claim 1, wherein the temperature used for fusion in step (e) is in the range of 1400 to 1500 degree C. 6. A process for making slow release phosphate fertilizer as claimed in claim 1, wherein the time period for which fusion takes place in step (e) is in the range of 15 to 30 minutes. 7. A process for making slow release fused calcium magnesium phosphate fertilizer as claimed in claim 1, wherein the quenched melt is dried in step (g) to moisture content of less than 1 percent. 8. A process for making slow release fused calcium magnesium phosphate fertilizer substantially as herein before described with reference to the foregoing examples.

Documents:

1556-del-2007-Abstract-(10-10-2014).pdf

1556-del-2007-abstract.pdf

1556-del-2007-Claims-(10-10-2014).pdf

1556-del-2007-claims.pdf

1556-del-2007-Correspondence Others-(10-10-2014).pdf

1556-del-2007-Correspondence Others-(17-10-2014).pdf

1556-DEL-2007-Correspondence-Others (02-09-2009).pdf

1556-del-2007-correspondence-others.pdf

1556-del-2007-description (complete).pdf

1556-del-2007-form-1.pdf

1556-DEL-2007-Form-18.pdf

1556-del-2007-Form-2-(10-10-2014).pdf

1556-del-2007-form-2.pdf

1556-del-2007-form-26.pdf

1556-del-2007-form-3.pdf

1556-del-2007-form-5.pdf