PROCESS FOR PRODUCING AN AMMONIUM NITRATE OR CALCIUM AMMONIUM NITRATE FERTILIZER GRANULATE AND FERTILIZER GRANULATES PRODUCED THEREBY

Abstract

A method may be employed to produce a fertilizer granulate comprising an ammonium salt and, as a filler material, limestone, dolomite, and/or magnesite. At least a proportion of the limestone or dolomite or magnesite is at least partially calcinated prior to use in the fertilizer granulate. A targeted adjustment of the reactivity of the filler material may occur by its degree of calcination and/or its calcite proportion. If, for example, dolomite is used as a filler material, the calcination results in separation of carbon dioxide from the mineral. This calcination is a two-stage process in which the dolomite is first converted to periclase (MgO) and calcite (CaCO3), and the calcite is also converted by decomposition and release of carbon dioxide only at a higher temperature.

Claims

1.-24. (canceled)

25. A method for producing a fertilizer granulate comprising an ammonium salt and a filler material, the method comprising: at least partially calcining limestone or dolomite as the filler material prior to use in the fertilizer granulate; adjusting a reactivity of the filler material in a targeted manner by way of degree of calcination of the filler material; and adding to the fertilizer granulate the filler material, which filler material comprises at least one of calcined limestone, partially calcined limestone, calcined dolomite, or partially calcined dolomite in a total amount of up to 10% by weight.

26. The method of claim 25 wherein the fertilizer granulate comprises ammonium nitrate as a primary component.

27. The method of claim 26 wherein the fertilizer granulate comprises at least 80% ammonium nitrate.

28. The method of claim 26 wherein the filler material is added to the fertilizer granulate in a total amount of up to 5% by weight.

29. The method of claim 25 wherein the fertilizer granulate comprises acid-releasing additives or sulfate-containing additives in a total amount of up to 10% by weight.

30. The method of claim 25 wherein the fertilizer granulate comprises calcium ammonium nitrate as a primary component.

31. The method of claim 30 wherein the filler material comprises calcined magnesite or partially calcined magnesite in a total amount of up to 40% by weight.

32. The method of claim 30 wherein the fertilizer granulate comprises at least 60% by weight calcium ammonium nitrate.

33. The method of claim 25 comprising heating at least a portion of the filler material in a calcining oven.

34. The method of claim 33 wherein the at least the portion of the filler material is heated in the calcining oven to a degree of calcination, the method further comprising determining the degree of calcination via an analytical method.

35. The method of claim 33 wherein the at least the portion of the filler material is heated in the calcining oven to achieve a degree of calcination and the reactivity of the filler material, wherein after or during the calcination and prior to use of the filler material the reactivity of the filler material connected with the degree of calcination of the filler material is determined via an analytical method.

36. The method of claim 35 comprising determining the reactivity of the filler material by way of its reaction with a primary component of the fertilizer granulate.

37. The method of claim 25 wherein the calcination occurs at a temperature of less than 800 C.

38. The method of claim 25 wherein a degree to which the filler material is calcined is determined by determining a calcite proportion by way of x-ray diffractometry.

39. The method of claim 25 wherein a degree to which the filler material is calcined is achieved via a temperature and/or a duration of calcination.

40. The method of claim 29 wherein the duration of the calcination is between 2 minutes and 24 hours.

41. The method of claim 25 wherein dolomite is used as the filler material, the dolomite being calcined until such a proportion of calcium originally contained in the dolomite has been converted to calcite such that a calcite proportion in the filler material is at least approximately 20% by weight.

42. The method of claim 25 comprising selecting a degree to which the filler material is calcined based on calcite content of the filler material.

43. The method of claim 25 wherein the filler material comprises uncalcined dolomite and calcined dolomite.

44. The method of claim 43 wherein the reactivity of the filler material is adjusted via a ratio of uncalcined dolomite to calcined dolomite in the filler material.

45. The method of claim 25 wherein the filler material comprises dolomite that has been calcined at a temperature for a duration such that the filler material has a total reactivity of at least 2% mol.

46. The method of claim 25 wherein the filler material comprises a mixture of limestone and dolomite.

47. The method of claim 25 wherein the production of the fertilizer granulate occurs in a pugmill granulator.

48. A fertilizer granulate comprising ammonium nitrate or calcium ammonium nitrate as a primary component and at least a proportion of an at least partially calcined limestone and/or dolomite as a filler material, wherein a reactivity of the filler material has been adjusted in a targeted manner by way of its degree of calcination according to the method of claim 25.

49. A fertilizer granulate comprising ammonium nitrate or calcium ammonium nitrate as a primary component and at least a proportion of an at least partially calcined limestone and/or dolomite as a filler material, wherein a reactivity of the filler material has been adjusted in a targeted manner by way of its degree of calcination.

Description

[0069] The present invention is explained in further detail below by means of exemplary embodiments with reference to the attached drawings. The figures show the following:

[0070] FIG. 1 shows a graphic representation of a thermogravimetric analysis of a two-stage calcining process;

[0071] FIG. 2 shows a graphic representation of a thermogravimetric analysis of a dolomite under atmospheric conditions; and

[0072] FIG. 3 shows a graphic representation of the contents of dolomite, calcite, periclase and calcium oxide (and also of the hydration product calcium hydroxide) as a function of the calcination conditions.

EXAMPLE 1

[0073] Dolomites deacidify in the calcining process via a two-stage process, wherein in a first step, essentially the MgCO.sub.3 portion of the crystal lattice first deacidifies, after which MgO and CaCO.sub.3 are produced. In a second step, the CaCO.sub.3 then decomposes, resulting in completely calcined dolomite in the oxide forms MgO and CaO. In FIG. 1, this process is graphically represented based on a thermogravimetric analysis. In the upper figure, on the ordinate, the mass of a sample is shown with respect to the mass at the beginning of the analysis, which was carried out in a crucible. The curve therefore begins at 100%. It can be seen that after a certain duration, on heating of the sample to a temperature of approx. 700 C., the decomposition process begins and CO.sub.2 escapes, causing the mass of the remaining sample to decrease. Two curves were recorded in order to visualize the influence of the CO.sub.2 partial pressure in the crucible, wherein one of the curves was recorded with a crucible not having a lid (atmospheric condition) and the other was recorded with a lid in place (in a vacuum; increased CO.sub.2 partial pressure). As expected, in the case of the sample having a lid, the process is slowed by the higher CO.sub.2 partial pressure and thus shifted to higher temperatures. Moreover, it can be seen that an increase in the CO.sub.2 partial pressure leads to better separation of the two calcination stages. In this manner, the calcination can be controlled by adjusting the CO.sub.2 partial pressure as a further parameter.

[0074] In the lower area of FIG. 1, two further curves relating to this experiment are shown, wherein the heat flow in W/g is shown on the ordinate and the duration of the experiment and the increasing temperature are shown on the abscissa, wherein heating was carried out beginning at room temperature. It can be seen that after a heating time of approx. 75 min, a temperature of approx. 700 C. was reached, at which point the heat flow increases sharply (increase in negative heat flow, i.e. increase in the endothermal range), as the decomposition of the carbonates is an endothermal process in which heat is consumed.

[0075] In this lower area, it can be clearly seen that the decomposition takes place in two stages, with a first maximum at approx. 780 C. and a second maximum at approx. 860 C., wherein these maxima are displaced toward the second recorded curve, which again was recorded with a crucible having a lid, because of the higher partial pressure of CO.sub.2 corresponding to higher temperatures.

[0076] FIG. 2 shows a further thermogravimetric analysis of a dolomite under atmospheric conditions, wherein it can be seen here that at low CO.sub.2 partial pressure, the two deacidification stages can merge into one another, for which reason the calcination step is preferably carried out under a CO.sub.2 atmosphere.

EXAMPLE 2

[0077] Different degrees of calcination were produced for a dolomite based on the results of the thermogravimetric analysis, and the composition was first investigated by means of x-ray fluorescence analysis (RFA) and powder diffractometry (XRD). It was found that depending on the calcination duration and temperature, it is possible to adjust the composition with respect to dolomite, calcite and magnesium oxide (as well as calcium oxide, and as its hydration product, calcium hydroxide) as desired.

[0078] Table 1 below shows the result of a quantitative powder diffractometry analysis (XRD analysis) of a dolomite sample in the original state and after various degrees of calcination.

TABLE-US-00001 TABLE 1 Mineralogische Analyse Dolomit Dolomit Dolomit 725 C., 750 C., 750 C., Mineral Dolomit 0.5 h 1 h 4 h % Dolomite CaMg(CO.sub.3).sub.2 99.6 31.0 1.7 0.0 % Calcite CaCO.sub.3 0.4 49.2 69.6 61.2 % Quartz SiO.sub.2 0.0 0.0 0.0 0.0 % Periclase MgO 0.0 19.8 28.7 30.9 % Brucite Mg(OH).sub.2 0.0 0.0 0.0 0.0 % Lime CaO 0.0 0.0 0.0 3.4 % Ca(OH).sub.2 0.0 0.0 0.0 4.5 Portlandite % Summe 100.0 100.0 100.0 100.0 Key: Mineralogical analysis Dolomite Total X-ray fluorescence analysis (RFA) shows that as expected, the chemical composition (within the measurement uncertainty of the method) remains identical as a percentage of the change in ignition loss (due to the prior deacidification by partial calcination) (cf. CaO/MgO ratio).

TABLE-US-00002 TABLE 2 RFA of the dolomite sample in the original state and after varying degrees of calcination. Chemische Analyse Dolomit Dolomit Dolomit 725 C., 750 C., 750 C., Bezeichnung Dolomit 0.5 h 1 h 4 h % GV (1050 C.) 46.78 36.19 32.34 27.37 % CaO 31.67 38.50 41.38 43.50 % MgO 20.76 24.63 25.59 28.44 % Rest 0.79 0.68 0.69 0.69 % Summe 100.00 100.00 100.00 100.00 CaO/MgO-Verh. (n/n) 1.096 1.123 1.162 1.099 Key: Chemical analysis Designation Residue Total Dolomite Ratio

EXAMPLE 3

[0079] For the dolomite samples of varying degrees of calcination listed in the above tables, the radioactivity values were determined according to equation 5 and the method described in the text. Taking into account the total amounts of Ca and Mg present in the filler material, the size of the reacted partial amount is determined according to equations 2 to 4. The results are shown below in Table 3 with respect on the one hand to the reacted partial amount of Ca (R.sub.Ca) or Mg (R.sub.Mg) and also as total reactivity (R.sub.ges) based on the total amount of the sum of Ca and Mg given in mol %. For the dolomite calcined for 4 h, no usable results were obtained due to the extremely intense reactivity. However, it can be assumed based on estimates and comparison with the sample calcined for 1 h that the total reactivity will be significantly greater than 50 mol %.

TABLE-US-00003 TABLE 3 Reactivities of the dolomite sample in the original state and after varying degrees of calcination. Reaktivitt nach Gleichung 1 bis 3 Dolomit Dolomit Dolomit 725 C., 750 C., 750 C., Reaktivitt Dolomit 0.5 h 1 h 4 h R.sub.Mg mol-% 3.9 48.4 83.4 n.a. R.sub.Ca mol-% 1.7 10.1 20.8 n.a. R.sub.ges mol-% 2.8 28.2 49.7 n.a. Key: Reactivity according to equations 1 to 3 Reactivity Dolomite

EXAMPLE 4

[0080] For a mixture of three parts by mass of untreated dolomite and one part by mass of dolomite calcined at 725 C. for 0.5 h, the reactivity within the meaning of equation 5 was investigated. The total reactivity was determined at R.sub.ges=18.4 mol % (cf. R.sub.ges=2.8 mol % or 28.2 mol %).

[0081] This example shows that targeted reactivity levels are also adjustable by means of defined mixing ratios.

[0082] FIG. 3 shows the respective content of a rock having an initial dolomite content of 99.6% as a function of different calcination conditions with respect to treatment temperature and treatment duration. It can be seen that the percentage by mass of dolomite is decreased by the treatment, and that of calcite increased. After 1 h treatment at 750 C., the calcite content is higher than in only 30 min treatment at a lower temperature of 725 C. After 4 h treatment at 750 C., no more dolomite is present, and the proportion of calcium oxide and its hydration product calcium hydroxide has increased. It can also be seen that the magnesium oxide content increases with increasing temperature and treatment duration.