Optimization of the phosphogypsum granulation for bio-desulfurization systems

Phosphorite, or phosphate rock, is the most significant secondary rare-earth resource. It contains high amounts of phosphate-bearing minerals along with low contents of rare earth elements (REEs). In Florida, about 19 Mt of phosphate rock are mined annually and most are used to manufacture fertilizers using a wet process, in which sulfuric acid reacts with phosphates to produce phosphoric acid and phosphogypsum. In the wet process, REEs are also leached out into solution and eventually get lost in the leaching residue and phosphate fertilizer. Recovering REEs from Florida phosphate rock in the wet process will be beneficial to broadening rare-earth availability, improving the quality of phosphoric acid product and protecting the environment. This study focuses on the influences of wet-process operating conditions on REE leaching efficiency. The results indicate that REE leaching efficiency increases with phosphoric acid addition in the initial pulp. At a temperature of 75 °C, a stoichiometric ratio of sulfuric acid (H2 SO4) to calcium oxide (CaO) of 1.05 and a weight ratio of liquid to solid of 3.5, REE leaching efficiency reached a relatively high value of 52.82 percent. The trends of REE leaching efficiency were similar to those for phosphoric acid (P2O5). Extensive tests on the leaching residue showed that during leaching, about 90 percent of the REEs were released from the phosphate rock but only 52.82 percent ended up in the leaching solution. This phenomenon can be attributed to two factors: (1) the effect of phosphate ions (PO 4 3- ) in the solution, which caused REE ions to form REE phosphates and be precipitated into the leaching residue, and (2) the influence of large amounts of anions such as sulfate (SO 4 2- ), dihydrogen phosphate (H2 PO 4 - ) and hydrogen phosphate (HPO 4 2- ) anions as well as the polar molecule H3 PO4, which surrounded the REE cations and formed an ion atmosphere that prevented the PO43- from contacting and combining with REE cations. Interaction of these two opposite effects determined the REE distribution between leaching solution and residue.

Phosphate rocks (PRs) play a crucial role in ensuring the availability of phosphorous for the world's food needs. PRs are used to manufacture phosphoric acid in the wet process as well as P-fertilizers. The chemical and mineralogical compositions of PRs from Djebel Onk (Algeria), Khneifiss (Syria), Negev (Israel), Bou Craa (Morocco), and Khouribga (Morocco) are discussed in this study. PRs were characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), cold vapor atomic absorption spectrometry (CVAAS), ion chromatography (IC), and X-ray diffraction (XRD), as well as gravimetric and potentiometric methods. All PRs were mainly composed of CaO, P2O5, SiO2, F, SO3, Na2O, MgO, Al2O3, Fe2O3, SrO, and K2O at the level of wt.%. The P2O5 content accounted for 28.7-31.2%, which indicates that these are beneficial rocks to a marketable product. The degree of PR purity expressed by the minor elements ratio index (MER index) varied from 2.46% to 10.4%, and the CaO/P2O5 weight ratio from 1.6 to 1.9. In addition, the occurrence of trace elements such as As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Ti, V, U, and Zn, as well as Cr(VI) and Cl ions at the level of mg∙kg-1 was found. Since PRs will be used to produce P-fertilizers, their composition was compared with the regulatory parameters set up by EU Regulation 2019/1009 related to the heavy metals (As, Cd, Pb, Ni, Hg, Cu, Zn) and Cr(VI) contents in inorganic fertilizers. The heavy metals and Cr(VI) content in all PRs did not exceed the limit values. XRD analysis revealed that fluorapatite, hydroxyapatite, carbonate fluorapatite, and carbonate hydroxyapatite were the dominant minerals. The accuracy and precision of the used methods were evaluated by analysis of standard reference materials (SRM) for Western Phosphate Rock (NIST 694). The recovery was 85.3% for U and 109% for K2O, and the RSD ranged from 0.67% to 12.8%.

Granulation time in fluidized bed granulators

Optimisation of high shear granulation of multicomponent fertiliser using response surface methodology

1. During the rotation granulation process, ZrC-W cermet powders of larger specific surface form, other things being equal, spherical granules of smaller size. 2. As the wetting liquid (dibutyl phthalate) content of the powder is increased from 0.1 to 0.6 wt.%, the mean granule size decreases almost linearly; with further increase in dibutyl content, from 0.6 to 0.9%, the granules continue to increase slightly in size if the granulation time does not exceed 2 h. 3. The granule size increases with increase in granulation time. 4. Variation in powder charge weight in the range 40–200 g has virtually no effect upon the rate of granule growth. 5. The density of sintered granules grows with decrease in granule size. The apparent and tap densities of sintered granules and their flowability are independent of their size (for 300 to 80μ fractions).

Granulation of an insoluble powder in a spouted bed

Controlling granule size through breakage in a novel reverse-phase wet granulation process; the effect of impeller speed and binder liquid viscosity

Using high temperature gas-cooled reactors for greenhouse gas reduction and energy neutral production of phosphate fertilizers

\n Phosphogypsum is a waste produced by the phosphate fertiliser industry. It is formed by precipitation during wet sulphuric acid processing of phosphate rocks. Although phosphogypsum is mainly calcium sulphate dihydrate, it contains elevated levels of impurities, which originate from the source phosphate rock used in the phosphoric acid\nproduction. Among these impurities, radionuclides from U-238 and Th-232 decay series, particularly Ra-226, Ra-228\nand Pb-210, are of most concern due to their radiotoxicity. The phosphate fertiliser complex located in Santos Basin, Southwest Brazil, is responsible for the production of approximately 2000 tons of phosphogypsum per day. This phosphogypsum waste is stockpiled and presents a potential threat to the surrounding environment. This study aims to determine the activity concentration of Ra-226, Ra-228, Pb-210 and K-40 in the stockpiled phosphogypsum of the two main local producers. As a complementary study, trace and microelements (Ba, Co, Cr, Fe, Hf, Sb, Sc, Ta, Th, U, and rare earths Ce, Eu, La, Lu, Nd, Sm, Tb and Yb) were also determined by instrumental neutron activation analysis (INAA). Mean activity concentrations of 401±108 Bqkg-1, 173±65 Bqkg-1 and 389±106 Bqkg-1 were observed for Ra-226, Ra-228 and Pb-210 for one producer. The results obtained for the second producer were 840±275 Bqkg-1, 225±32\nBqkg-1 and 827±276 Bqkg-1 for Ra-226, Ra-228 and Pb-210, respectively. Phosphogypsum samples are enriched in rareearths\nelements, specifically Ce, Eu, La, Nd, Sm, and Tb, and the elements Ba and Ta. The radiochemical and elemental\ncharacterisation of the phosphogypsum from industry A and C show that the stacks are quite homogeneous and mainly\ndependent upon the origin of the phosphatic rock used as raw material. This information is important and necessary for\ndecision making on possible uses of this waste. The radionuclides Ra and Pb, which present high radiotoxicity, although present in the phosphogypsum, are not available for the surrounding environment.\n

Application prospect of advanced oxidation technology in wet process phosphoric acid production

امروزه از کود کمپوست به‌عنوان جایگزینی برای کودهای شیمیایی که خساراتی را برای سلامتی انسان ها و همچنین برای زمین‌های کشاورزی به بار می آورد، یاد می شود. مشکلاتی مانند؛ حمل و نقل (حجم زیاد)، رطوبت زیاد، توزیع کود در مزرعه، گرد و غبار و انبارداری، در ارائه این کود به مزرعه وجود دارد. برای حل مشکلات مطرح شده فرآیند فشرده سازی مانند تولید پلت و گرانول، پیشنهاد می شود. در این تحقیق تأثیر پارامترهای گرانول کردن کود کمپوست بر روی درصد گرانول مفید تولید شده با استفاده از دستگاه استوانه دوار در مقیاس آزمایشگاهی مورد بررسی قرار گرفت. نتایج نشان داد که افزایش زمان گرانول کردن، موجب کاهش مقدار مفید گرانول تولیدی می شود. شرایط بهینه برای تولید گرانول زمانی حاصل می شود که در آن سرعت چرخش استوانه 38/40 دور بر دقیقه، زمان گرانول کردن 15 دقیقه، درصد پرشدگی 10 درصد از حجم استوانه و درصد چسباننده ملاس 97/40 درصد، باشد که با توجه به این شرایط پاسخ مقدار گرانول های مفید 6/81 درصد تخمین زده شد.

The Effect of Granulation Time of the Pan Granulation on the Characteristics of the Aggregates Containing Dunkirk Sediments

Increasing the Filtration Rate of Phosphor-gypsum by Using Mineral Additives

Fuzzy Modelling and Dynamic Simulation of a Fluidised Bed Granulator

Purpose. To study the granulometric composition of starch in grain of collection samples of winter triticale (Triticosecale Wittm.) and to identify forms with minimal variation in the size of starch granules for further creation of source material when breeding varieties being optimal for starch and bioethanol production. Methods. The studies were carried out in 2016, 2017 at the department of breeding and seed production of grain crops of the NSC “Institute of Agriculture of NAAS” with 142 collection samples, varieties and breeding lines of hexaploid winter triticale and 22 samples of bread winter wheat (as a control) grown in breeding crop rotation of the Institute in individual experiment on uniform agrotechnical background. The granulometric structure of starch was investigated by light microscopy of milled triticale grains in combination with digital image analysis. For data processing, parametric methods of variation statistics, regression and factor analysis were used using licensed programs Microsoft Office Excel 2007 and StatSoft STATISTICA 8.0.360. Results. The analysis of 164 samples of triticale and wheat by the size of starch granules showed the variability of this trait. The most of the samples had variation coefficient in the range of 12–30 %. In triticale, the average granule size was maximal in the line 244/16 (24.20 µm), and minimal one was in the Yasha variety (15.79 µm). In the samples studied, the size of the most of the granules was 16–22 μm, but size distribution within the sampling was uneven. The least variability was found in the line 145/16 (10.97 %), the most one in the line 181/16 (37.56 %). Conclusions. A significant difference between winter triticale by starch granule size within the species, between individual lines and varieties was established. The minimum coefficient of variation of the starch granules size was in samples with the least average size. The lines 202, 206 and 220 are recommended as sources in breeding triticale varieties to produce starch for technical purposes, and the varieties Petrol, Yasha and Mundo for the alcohol-distillate direction of the technological use of grain.