USE OF A THERMOPHOSPHATE FERTILIZER THAT HAS LOW SOLUBILITY IN WATER AND METHOD FOR REDUCING EUTROPHICATION OF WATER BODIES DUE TO FERTILIZERS

Abstract

The present invention relates to the use of a poorly water-soluble thermophosphate fertilizer to reduce water eutrophication caused by fertilizers, particularly due to fertilizer production or soil fertilization. The invention further relates to a method of reducing water eutrophication caused by fertilizers.

Claims

1. A poorly-water-soluble thermophosphate fertilizer, for reducing water eutrophication caused by fertilizers.

2. The fertilizer according to claim 1, comprising, in % by mass based on the total mass of the fertilizer: (a) a minimum 15.0% and maximum 21.0% of P.sub.2O.sub.5; (b) a minimum 13.5% and maximum 22.5% of Ca; (c) a minimum 3.0% and maximum 11.0% of Mg and (d) a minimum 6.3% and maximum 13.7% of Si.

3. The fertilizer according to claim 1 presenting phosphorus solubility (in terms of P.sub.2O.sub.5) in water of at most 1000 ppm.

4. The fertilizer according to claim 3, exhibiting phosphorus solubility (in terms of P.sub.2O.sub.5) in water of at most 600 ppm.

5. The fertilizer according to claim 4, exhibiting phosphorus solubility (in terms of P.sub.2O.sub.5) in water of at most 400 ppm.

6. The fertilizer according to claim 1, obtained by melting at temperatures of from 1350 C. to 1450 C., followed by quenching.

7. A method of reducing water eutrophication caused by fertilizers, comprising the step of fertilizing the soil with a poorly water-soluble thermophosphate fertilizer.

8. The method according to claim 7, comprising, in % by mass based on the total mass of the fertilizer: (a) a minimum 15.0% and maximum 21.0% of P.sub.2O.sub.5; (b) a minimum 13.5% and maximum 22.5% of Ca; (c) a minimum 3.0% and maximum 11.0% of Mg and (d) a minimum 6.3% and maximum 13.7% of Si.

9. The method according to claim 7, wherein the poorly water-soluble thermophosphate fertilizer has phosphorus solubility (in terms of P.sub.2O.sub.5) in water of at most 1000 ppm.

10. The method according to claim 9, wherein the poorly water-soluble thermophosphate fertilizer exhibits phosphorus solubility (in terms of P.sub.2O.sub.5) in water of at most 600 ppm.

11. The method according to claim 10, wherein the poorly water-soluble thermophosphate fertilizer exhibits phosphorus solubility (in terms of P.sub.2O.sub.5) in water of at most 400 ppm.

12. The method according to claim 7, wherein the poorly water-soluble thermophosphate fertilizers are obtained by melting at temperatures of from 1350 C. to 1450 C., followed by quenching.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0039] FIG. 1 depicts a dam next to a thermophosphate manufacturing plant subject to the use and method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0040] Given the environmental issues caused by the use of fertilizers having water-soluble components, which causes leaching thereof and consequent eutrophication of the final aquatic environment, it was found that the use of a poorly soluble fertilizer has resulted in reduced eutrophication of waters near to sites where fertilizers are produced or applied.

[0041] Thus, one embodiment of the invention is the use of a poorly water-soluble thermophosphate fertilizer to reduce water eutrophication caused by fertilizers, particularly due to fertilizer production or soil fertilization (application of fertilizers).

[0042] The term poorly water-soluble thermophosphate fertilizer means the thermophosphate fertilizer having one or more elements (e.g., phosphorus, nitrogen, etc.) that solubilize in very small amounts in water. In one embodiment of the invention the poorly water-soluble thermophosphate fertilizer of the invention exhibits phosphorus solubility (in terms of P.sub.2O.sub.5) in water of at most 1000 ppm, preferably at most 600 ppm, and more preferably 400 ppm. Fertilizers are, however, soluble in 2% citric acid and also in ammonium neutral citrate plus water (CNA).

[0043] Below Table 3 is provided showing water solubility of ready thermophosphate fertilizers that are within the scope of the invention (Yoorin thermophosphates)

TABLE-US-00003 TABLE 3 P.sub.2O.sub.5 water solubility of thermophosphate fertilizers that are within the scope of the invention % P.sub.2O.sub.5 soluble Water- in 2% % CNA soluble FERTILIZER % P.sub.2O.sub.5 Total citric acid soluble P.sub.2O.sub.5 P.sub.2O.sub.5 (ppm) YOORIN 18.52 (<0.15 mm) (<0.15 mm) (<0.15 mm) MASTER 17.5 9.55 503 MG YOORIN 18.52 (9 < 0.15 (<0.15 mm) (<0.15 mm) mm) 17.39 10.66 592 MC 60 S 17.40 12.04 4.80 390 YOORIN YOORIN 18.10 16.52 7.95 367 MASTER

[0044] Table 3 shows that ready thermophosphate fertilizers are nearly water insoluble and therefore do not contribute to eutrophication processes.

[0045] In contrast, when common phosphate fertilizers are taken into consideration, they are all found to be highly water-soluble, as shown in Table 4 below:

TABLE-US-00004 TABLE 4 Water-soluble Phosphate Fertilizers - P.sub.2O.sub.5 water solubility, 2% citric acid and CNA % P.sub.2O.sub.5 soluble % CNA Water- % P.sub.2O.sub.5 in 2% soluble soluble FERTILIZER Total citric acid P.sub.2O.sub.5 P.sub.2O.sub.5 (ppm) TSP 46.84 39.35 45.43 375,500 GRANULATE TSP FINE- 46.19 40.77 44.81 388,000 TRIPLE Simple SSP 19.70 17.66 17.60 169,300 Granulated MAP 54.75 51.30 53.32 465,100

[0046] All of the examples of Table 4 above are solubilized in water at levels close to 500,000 ppm, except for simple SSP, which is a fertilizer obtained by grinding phosphate rock and mixing it with sulfuric acid, having low P.sub.2O.sub.s content, but not comparable to those fertilizers within the scope of the present invention.

[0047] The poorly water-soluble thermophosphate fertilizer that reduces water eutrophication caused by fertilization comprises, in % by mass based on the total mass of the fertilizer:

[0048] P.sub.2O.sub.5: minimum 15.0% and maximum 21.0%;

[0049] Ca: minimum 13.5% and maximum 22.5%;

[0050] Mg: minimum 3.0% and maximum 11.0%; and

[0051] Si: minimum 6.3% and maximum 13.7%;

[0052] Said poorly water-soluble thermophosphate fertilizer is obtained by melting at temperatures from 1350 C. to 1450 C. and quenching, particularly with large volumes of water, even more particularly with 80 parts by volume of water for each part of volume of molten material. Thus, the molten material instantly solidifies as a poorly water-soluble phosphate glass.

[0053] All this water mass and poorly water-soluble glass is transported to a gravitational draining system (closed and continuous recycling system) consisting of several concrete tanks (sedimentation tanks) to separate molten phosphate glass from cooling water. The drained water separated from solids cools again the molten thermophosphate in other furnaces sequentially, while the phosphate glass placed in an open area drains the remaining volume of water. The phosphates (phosphate glasses) thus obtained, while still containing moisture water, are dried in rotary dryers, ground and packed in bags for different classes of thermophosphate fertilizers.

[0054] Examples of commercially available thermophosphate fertilizers available for application within the scope of the invention are: YOORIN MASTER, MG YOORIN, MC 60 S YOORIN.

[0055] The invention also relates to a method of reducing water eutrophication caused by fertilizers, particularly caused by the production of fertilizers or soil fertilization, which comprises the step of fertilizing the soil with a poorly water-soluble thermophosphate fertilizer having the aforementioned characteristics.

Examples

[0056] The following are examples that demonstrate the low solubility of thermophosphate fertilizers that reduce eutrophication caused by soil fertilization, as they are not leached or solubilized by rainwater or irrigation water and carried to ponds, lakes and reservoirs.

[0057] In the production of thermophosphates an open water recirculation system is used for external cooling of electric furnaces. In such cooling system, water has no direct contact with the product being processed. Cooling water comes from a dam, passes through the furnaces, refrigerates them and returns to a sedimentation tank, and from there, it goes back to the dam.

[0058] FIG. 1 shows a dam next to a thermophosphate manufacturing facility, particularly Yoorin thermophosphates, showing the water system used in the dam in the process of producing Yoorin molten phosphates, such as (I) furnace steel jacket cooling water working in an open-loop, and (II) phosphate glass washing and cooling water produced and processed in concrete tanks A, B, C, D and E (outside the lake), working in a closed-loop (see table 5, sedimentation tank). Another dam (not represented) designated herein as Represa Cip, which is used for generating electricity and supplying water to the city, forms a small river that leads upstream water to downstream of the dam, wherein the dam centered on the image of FIG. 1 is approximately 375 m long by 110 m wide.

[0059] Feedwater of the dam of FIG. 1 comes from the river upstream from the dam and flows downstream being carried by pipes into melting furnaces at Yoorin. This water, after being used as cooling water for phosphate melting furnace hoods, is drained downstream, continuing the Lake formation water stream (see Table 5, Upstream and Downstream).

[0060] Inlet and outlet water monitoring is made for phosphorus content (ppm), as can be seen in Table 5 below of P.sub.2O.sub.5 solubility in water.

TABLE-US-00005 TABLE 5 P.sub.2O.sub.5 water solubility in the production of thermophosphate fertilizer that is within the scope of the invention Phosphorus Amount Downstream Sedimentation Phosphorus Phosphorus Tank FERTILIZER (ppm) (ppm) (ppm) September/2015 1.04 0.970 November/2015 0.296 0.150 February/2016 1.980 1.560 April/2016 1.380 1.090 May/2016 17.28

[0061] The 17.28 ppm value present in Table 5 relative to the May 2016 sampling of closed-loop draining water also shows very low phosphorus solubilization by the manufacturing process conditions (high phosphate melting temperatures, contact time with cooling water, all of them being favorable conditions for an easy solubilization).

[0062] Moreover, by comparing the upstream and downstream phosphorus concentration, it is evident that the fertilizer in sedimentation tanks of an open-loop water cooling system, after washing, is not solubilized when washed with water. Thus, it is noted that the phosphorus concentration is very low downstream, being of at most 1.6 ppm, which causes reduced eutrophication caused by using fertilizers that provide soluble phosphorus to algae and microalgae. Thus, in the production of poorly soluble thermophosphate fertilizers there is reduced eutrophication.

[0063] FIG. 1 illustrates the quality of water free from eutrophication.

[0064] Thus, the use of poorly water-soluble thermophosphate fertilizers reduces eutrophication caused by fertilizers, particularly caused by their production or soil fertilization.