Polyphosphoric acid calcium magnesium fertilizer, polyphosphoric acid calcium magnesium fertilizer prepared by using phosphoric acid and phosphorus tailings as raw material and preparation method therefor

Abstract

The present invention relates to a polyphosphoric acid calcium magnesium fertilizer prepared by using phosphoric acid and phosphorus tailings as raw materials and a preparation method therefor. The polyphosphoric acid calcium magnesium fertilizer is prepared by using phosphorus tailings and phosphoric acid as raw materials. Based on P.sub.2O.sub.5, MgO and CaO, in the polyphosphoric acid calcium magnesium fertilizer: total phosphorus is 50-68%, effective phosphorus is 47-66%, total magnesium is 5-18%, effective magnesium is 4-15%, total calcium is 11-20%, effective calcium is 10-18%, and all are expressed in mass percentage. Based on P.sub.2O.sub.5, the polymerization rate of the polyphosphoric acid calcium magnesium fertilizer is ≥50%. The present invention also provides a preparation method for the fertilizer. The phosphorus in the product prepared by the invention has sustained-release properties. The fertilizer is well suited for crops requiring large amounts of calcium and magnesium.

Claims

1. A method for preparing a calcium magnesium polyphosphate fertilizer by using wet-process phosphoric acid and phosphorus tailings as raw materials, comprising the following steps: (1) mixing and reacting the phosphorus tailings and the phosphoric acid at room temperature, to obtain a reaction mixture; and (2) at a high temperature of 200° C. to 600° C., subjecting the reaction mixture to a calcination reaction or a polymerization reaction under the action of hot air, and quenching the reaction when a polymerization rate of the phosphoric acid, based on P.sub.2O.sub.5, reaches ≥50%, to obtain the calcium magnesium polyphosphate fertilizer; wherein based on P.sub.2O.sub.5, MgO and CaO, the calcium magnesium polyphosphate fertilizer comprises 55%-65% of total phosphorus, 54%-64% of available phosphorus, 8% to 15% of total magnesium, 8% to 14% of available magnesium, 13% to 20% of total calcium, and 12% to 17% of available calcium, with all the values being expressed in mass percentage; wherein “available phosphorus”, “available magnesium” and “available calcium” refer to phosphorus (based on P.sub.2O.sub.5), magnesium (based on MgO) and calcium (based on CaO) that can be extracted by ethylenediaminetetraacetic acid under an alkaline conditions of pH value ranging from 12 to 13.

2. The method according to claim 1, wherein a duration of mixing and reacting the phosphorus tailings and the phosphoric acid at room temperature in step (1) is 1-3 h.

3. The method according to claim 1, wherein the phosphorus tailings in step (1) comprise 4% to 8% by mass of phosphorus based on P.sub.2O.sub.5, 15% to 19% by mass of magnesium based on MgO, and 28% to 38% by mass of calcium based on CaO.

4. The method according to claim 1, wherein in step (1), the phosphorus tailings and the phosphoric acid are added in a ratio such that the molar ratio of P.sub.2O.sub.5: (CaO+MgO) in the reaction mixture is from 1:1.2 to 1:1.8.

5. The method according to claim 4, wherein in step (1), the phosphorus tailings and the phosphoric acid are added in a ratio such that the molar ratio of P.sub.2O.sub.5: (CaO+MgO) in the reaction mixture is from 1:1.25 to 1:1.45.

6. The method according to claim 1, wherein in step (2), the calcination reaction is performed in a temperature of 35020 C. to 450° C.

7. The method according to claim 1, wherein in step (2), before the calcination reaction, the reaction mixture is concentrated at a temperature of 60° C. to 100° C. and a pressure of 10 kPa to 90 kPa until a mass percentage of water in the reaction mixture is 35% to 45%.

Description

DETAILED DESCRIPTION

(1) The present disclosure is further described below through specific examples, but not limited herein.

(2) In the examples, all “%” refers to percentage by mass.

EXAMPLES

Example 1

(3) Provided is a method for preparing calcium magnesium polyphosphate fertilizers by using wet-process phosphoric acid and phosphorus tailings, wherein the used raw materials have the following characteristics: wet-process phosphoric acid: w(P.sub.2O.sub.5) 23.39%, w(MgO) 1.01%, w(CaO) 0.12%; phosphorus tailings: w(P.sub.2O.sub.5) 7.07%, w(MgO) 16.2%, w(CaO) 35.11%.

(4) The method comprises the following steps: (1) mixing and reacting 100 kg of the phosphorus tailings and 400 kg of the wet-process phosphoric acid in a reactor at room temperature for 1.5 hours, to obtain a reaction mixture; (2) calcining the obtained reaction mixture at a temperature of 350° C. for 3.5 hours, and then grinding into powder to obtain a calcium magnesium polyphosphate product.

(5) The analysis results of the product are showed in the following table:

(6) TABLE-US-00001 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH (1%) 58.66% 57.74% 11.73% 10.98% 18.87% 15.51% 80.54% 4.3

Example 2

(7) Provided is a method for preparing calcium magnesium polyphosphate fertilizers by using wet-process phosphoric acid and phosphorus tailings, wherein the used raw materials have the following characteristics: wet-process phosphoric acid: w(P.sub.2O.sub.5) 22.39%, w(MgO) 1.23%, w(CaO) 0.15%; phosphorus tailings: w(P.sub.2O.sub.5) 6.18%, w(MgO) 15.23%, w(CaO) 34.32%.

(8) The method comprises the following steps: (1) mixing and reacting 100 kg of the phosphorus tailings and 520 kg of the phosphoric acid in a reactor at room temperature for 2 hours, to obtain a reaction mixture; (2) concentrating the obtained reaction mixture at a temperature of 80° C. and a pressure of 30 kPa, to obtain a concentrated liquid having 44% to 45% by mass of water in the slurry; (3) calcining the obtained concentrated liquid at a temperature of 450° C. for 3 hours, and then grinding into powder to obtain a calcium magnesium polyphosphate product.

(9) The analysis results of the product are shown in the following table:

(10) TABLE-US-00002 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 63.50% 63.13% 9.94% 9.4% 16.37% 15.94% 85.12% 3.1

Example 3

(11) Provided is a method for preparing calcium magnesium polyphosphate fertilizers by using wet-process phosphoric acid and phosphorus tailings, wherein the used raw materials have the following characteristics: wet-process phosphoric acid: w(P.sub.2O.sub.5) 22.39%, w(MgO) 1.33%, w(CaO) 0.19%; phosphorus tailings: w(P.sub.2O.sub.5)7.02%, w(MgO) 17.23%, w(CaO) 33.35%.

(12) The method comprises the following steps: (1) mixing and reacting 100 kg of the phosphorus tailings and 580 kg of the phosphoric acid in a reactor at room temperature for 1 h, to obtain a reaction mixture; (2) concentrating the obtained reaction mixture at a temperature of 90° C. and a pressure of 30 kPa, to obtain a concentrated liquid having 35% to 36% by mass of water in the slurry; (3) calcining the obtained concentrated liquid at a temperature of 600° C. for 2 hours, and then grinding into powder to obtain a calcium magnesium polyphosphate product.

(13) The analysis results of the product are shown in the following table:

(14) TABLE-US-00003 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 64.12% 51.65% 9.25% 7.01% 16.52% 10.17% 83.2% 5.4

Example 4

(15) Provided is a method for preparing calcium magnesium polyphosphate fertilizers by using wet-process phosphoric acid and phosphorus tailings, wherein the used raw materials have the following characteristics: wet-process phosphoric acid: w(P.sub.2O.sub.5) 22.39%, w(MgO) 1.33%, w(CaO) 0.19%; phosphorus tailings: w(P.sub.2O.sub.5) 5.02%, w(MgO) 17.03%, w(CaO) 32.15%;

(16) The method comprises the following steps: (1) mixing and reacting 100 kg of the phosphorus tailings and 500 kg of the phosphoric acid in a reactor at room temperature for 1 h, to obtain a reaction mixture; (2) concentrating the obtained reaction mixture at a temperature of 90° C. and a pressure of 30 kPa, to obtain a concentrated liquid having 35% to 36% by mass of water in the slurry; (3) calcining the obtained concentrated liquid at a temperature of 200° C. for 4 hours, and then grinding into powder to obtain a calcium magnesium polyphosphate product.

(17) The analysis results of the product are shown in the following table.

(18) TABLE-US-00004 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 55.23% 54.44% 11.78% 11.18% 15.86% 15.06% 57.96 2.85

Example 5

(19) Provided is a method for preparing calcium magnesium polyphosphate fertilizers by using wet-process phosphoric acid and phosphorus tailings, wherein the used raw materials have the following characteristics: wet-process phosphoric acid: w(P.sub.2O.sub.5) 25.41%, w(MgO) 1.41%, w(CaO) 0.23%; phosphorus tailings: w(P.sub.2O.sub.5) 5.91%, w(MgO) 18.33%, w(CaO) 31.35%;

(20) The method comprises the following steps: (1) mixing and reacting 100 kg of the phosphorus tailings and 500 kg of the phosphoric acid in a reactor at room temperature for 1.5 h, to obtain a reaction mixture; and (2) pumping the above reaction mixture into a top of a spray tower and spraying it out, then introducing hot air at 450° C. into the spray tower, and under the effect of the hot air, concentrating and polymerizing the reaction mixture, to obtain a calcium magnesium polyphosphate product.

(21) The analysis results of the product are shown in the following table:

(22) TABLE-US-00005 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 60.02% 59.54% 13.22% 12.31% 17.51% 16.17% 80.13 4.5

Example 6

(23) Provided is method for preparing calcium magnesium polyphosphate fertilizers by using wet-process phosphoric acid and phosphorus tailings, wherein the used raw materials have the following characteristics: wet-process phosphoric acid: w(P.sub.2O.sub.5) 22.39%, w(MgO) 1.33%, w(CaO) 0.19%; phosphorus tailings: w(P.sub.2O.sub.5) 5.91%, w(MgO) 18.33%, w(CaO) 31.35%;

(24) The method comprises the following steps: (1) mixing and reacting 100 kg of the phosphorus tailings and 500 kg of the phosphoric acid in a reactor at room temperature for 2 h, to obtain a reaction mixture; (2) concentrating the obtained reaction mixture at a temperature of 90° C. and a pressure of 30 kPa, to obtain a concentrated liquid having 35% to 36% by mass of water in the slurry; (3) calcining the obtained concentrated liquid at a temperature of 250° C. for 5 hours, and then grinding into powder to obtain a calcium magnesium polyphosphate product.

(25) The analysis results of the product are shown in the following table.

(26) TABLE-US-00006 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 58.33% 57.95% 12.65% 11.16% 17.79% 17.10% 65.39 3.6

Comparative Example 1

(27) The raw materials and the method are the same as in Example 1, except that the amount of the wet-process phosphoric acid in step (1) was changed to 350 kg.

(28) The analysis results of the product are shown in the following table:

(29) TABLE-US-00007 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 52.78% 48.23% 12.36% 8.12% 19.23% 15.11% 70.54% 4.6

Comparative Example 2

(30) The raw materials and the method are the same as in Example 1, except that the temperature during the reaction in step (2) was changed to 150° C.

(31) The analysis results of the product are shown in the following table:

(32) TABLE-US-00008 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 48.46% 45.95% 10.56% 7.25% 16.42% 13.89% 35.34% 4.1

Comparative Example 3

(33) The raw materials and the method are the same as in Example 3, except that the amount of the wet-process phosphoric acid in step (1) was changed to 650 kg.

(34) The analysis results of the product are shown in the following table:

(35) TABLE-US-00009 Total Available Total Available Total Available Polymerization P.sub.2O.sub.5 P.sub.2O.sub.5 MgO MgO CaO CaO rate pH(1%) 64.51% 52.23% 10.23% 8.22% 16.71% 11.25% 85% 5.0

(36) Due to excessive amount of phosphoric acid, the materials in the preparation process of the product obtained in this Comparative Example have an increased viscosity, resulting in a limited production and poor marketability.

(37) Test Example

(38) Raw materials: urea (N 46%), potassium nitrate (N 13.5%, K.sub.2O 46%), monoammonium phosphate (N 11%, P.sub.2O.sub.5 49%), calcium nitrate (N 11%, CaO 23%), magnesium sulfate heptahydrate (MgO 16%), ammonium polyphosphate (11-44-0) and water-soluble fertilizers (16-8-34) are all commercially available.

(39) Date and location for the test: the test was carried out in December, 2016 in a watermelon greenhouse in Fei Country, Linyi City, Shandong Province.

(40) The treatments in the test were as follow.

(41) Treatment 1: 18.5 kg of monoammonium phosphate, 16 kg of urea, 16 kg of potassium nitrate, 10 kg of calcium nitrate, and 8.8 kg of magnesium sulfate heptahydrate were applied as base fertilizers, and when the watermelon at the fruit enlargement stage grew as big as an egg, 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation, and another 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation again after 10 days.

(42) Treatment 2: 14 kg of the calcium magnesium polyphosphate obtained in Example 2, 16 kg of urea, and 16 kg of potassium nitrate were applied as base fertilizers, and when the watermelon at the fruit enlargement stage grew as big as an egg, 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation, and another 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation again after 10 days.

(43) Treatment 3: 20 kg of calcium magnesium polyphosphate product obtained in Comparative Example 2, 16 kg of urea, and 16 kg of potassium nitrate were applied as base fertilizers, and when the watermelon at the fruit enlargement stage grew as big as an egg, 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation, and another 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation again after 10 days.

(44) Treatment 4: 19 kg of ammonium polyphosphate (11-44-0), 16kg of urea , 16 kg of potassium nitrate , 10 kg of calcium nitrate , and 8.8 kg of magnesium sulfate heptahydrate were applied as base fertilizers, and when the watermelon at the fruit enlargement stage grew as big as an egg, 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation, and another 5 kg of water-soluble fertilizers (16-8-34) was applied with irrigation again after 10 days.

(45) There were 3 replicate groups for each treatment, and the average value was calculated. Only the first crop of watermelon was calculated. The results are shown as following.

(46) TABLE-US-00010 TABLE 1 Effects of different fertilization treatments on watermelon in greenhouse Yield Increased Fertilizer Soluble solid per mu production type Spad materials (g) (Kg) ratio (%) Treatment 1 68.6 9.5% 2320 — Treatment 2 72.1 10.3% 2695 16.2% Treatment 3 69.0 10.1% 2425 4.5% Treatment 4 69.7 9.6% 2489 7.3%

(47) As can be clearly seen from Table 1, the products in the present disclosure had effects of markedly improving quality and increasing production. In addition, although the amount of available phosphorus applied in treatment 3 is the same as that in treatment 2, due to the polymerization rate of phosphorus in Treatment 3 is lower, the increased production in Treatment 3 is reduced by 11.7% as compared with that Treatment 2. The term of “Spad” in Table 2 represents the measured value of chlorophyll.

(48) In addition, the application of ammonium polyphosphate instead of monoammonium phosphate in Treatment 4 can increase the yield by 7.3% as compared with that in Treatment 1, but it is still 8.9% less than that in Treatment 2, indicating that ammonium polyphosphate plus calcium fertilizer and magnesium fertilizer are difficult to achieve the same effect of calcium magnesium polyphosphate of the present invention

(49) The above examples are merely the preferred embodiments of the present disclosure, and are not intended to limit the present invention in any form. Moreover, anything that does not departed from the technical solutions of the present disclosure, including any simple amendments and equivalent variations as well as modifications of the above examples in accordance with the technical essence of the present disclosure, should fall within the scope of technical solutions of the present disclosure.