Obtaining NPK fertilizers using decomposition of phosphate rock by sulphuric acid

In this study a method for obtaining granular NPK fertilizers of various grades has been established. Kola apatite or Baltic phosphorites were dissolved in 57% H₂SO₄; the resulting slurries were then ammoniated, evaporated and mixed with urea or ammonium nitrate and potassium salts. In some experiments micronutrients (B, Cu, Mo, Co or Mn) were added. The mixtures were dried and granulated. When using urea, granulation was carried out by heating the mixture until partial melting occurred, but the mixtures with ammonium nitrate had to be granulated with the addition of water. The products contained 29–38% fertilizer nutrients (N soluble in water, P₂O₅ soluble in citric acid and K₂O soluble in water) and had a ratio of over 90% of P₂O₅ soluble in citric acid to the P₂O₅ total. The granules were hygroscopic, but little caking occurred. The urea-containing materials produced better granules. Adding micronutrients usually resulted in an improvement in the product quality (an increase in the granule hardness and phosphorus solubility).     

Compression testing of granular NPK fertilizers

The crush strength of granular NPK fertilizer has been accurately determined using Instron compression testing equipment. Stress-strain analysis shows a distinctive break point followed by break up of granule fragments. The force required to crush the granules is a function of the granule diameter but the calculated pressure required to crush each granule remained relatively constant. Factors such as moisture ingress and coating oils have been shown to affect granule strength. A direct link between caking of granular fertilizers and crush strength has been established. This revised version was published online in August 2006 with corrections to the Cover Date.     

尿素过磷酸钙复肥生产工艺

介绍了尿素过磷酸钙（USP）复肥的主要生产工艺过程及条件,认为USP复肥是普通过磷酸钙（SSP）生产厂理想的升级产品。     

Availability of banded triple superphosphate with urea and phosphorus use efficiency by corn

Phosphorus fixation results in low P use efficiency in acid soils. Increase in soil pH through urea hydrolysis may improve P availability and use efficiency. Growth chamber and field experiments were conducted to evaluate effects of urea on triple superphosphate (TSP) transformation and P use efficiency. A Ste. Rosalie clay (Typic Humaquept), an Ormstown silty clay loam (Typic Humaquept) and a Chicot sandy clay loam (Typic Hapludalf) were used in the growth chamber experiment with three rates of N (0, 200 and 400 mg N kg-1), two N sources, either urea or NH4 NO3, based on 87 mg P kg-1 soil. In the field, three rates of urea (0, 60 and 120 kg N ha-1) and two rates of TSP (26 and 52 kg P ha-1) were compared on a Ste. Rosalie clay and an Ormstown silty clay loam. Compacted or blended mixtures of urea-TSP with different ratios of N:P were used in the field experiment. In the growth chamber experiment, soil pH and dissolved organic carbon (DOC) concentration was increased by added urea, and Mehlich (3) and water extractable P thus increased with increased urea. Soil pH, DOC and available P levels were not significantly affected by added NH4 NO3. Phosphorus uptake increased with added N, either urea or NH4 NO3, but P concentration increased only with addition of urea. In the field, soil Mehlich (3)-P at day 20, P uptake and use efficiency, corn yields increased when urea was applied with TSP. Compacted mixtures of urea-TSP increased P uptake and use efficiency, corn yields in comparison with blended mixtures. The beneficial effects of banded urea with TSP on P availability and P use efficiency were primarily attributed to urea hydrolysis, subsequent pH increase and organic matter dissolution as well as synergistic effect of N and P. These results indicate that compaction of urea plus TSP may offer a significant advantage over blended mixtures.     

Interaction of urea with triple superphosphate in a simulated fertilizer band

Fertilizer nutrient diffusion from fertilizer bands and transformations in soil can affect fertilizer nutrient availability to crops and knowledge of the transformations is necessary for proper management. The interaction of urea and triple superphosphate (TSP) on urea hydrolysis and P transformations during diffusion processes from a fertilizer band was evaluated in a laboratory incubation experiment with two eastern Canadian soils (Ste Rosalie clay, Modifiers Typic Humaquept, pH 5.0; Ormstown silty clay loam, Modifiers Typic Humaquept, pH 6.0). Two fertilizer sources (urea and TSP) and three N and P rates (0, 100 and 200 kg ha^–1) were combined in a factorial arrangement. Fertilizer combinations were placed on segmented soil columns, incubated and segments were analyzed for N and P content. Acidification from dissolution of TSP retarded urea hydrolysis, and curtailed the rise in soil pH surrounding the fertilizer band. Urea hydrolysis caused dissolution of organic matter in soils, which might inhibit precipitation of insoluble phosphates. Banding urea with TSP increased 1M KCl extractable soil P, soil solution P, sorbed P concentration and total P diffused away from the band. Urea decreased 0.01M CaCl₂ extractable P, indicating probable precipitation of calcium phosphates with CaCl₂ extraction. Banding urea with TSP could benefit P diffusion to plant roots in low Ca soils and increase fertilizer P availability.     

Ammonia volatilization from urea and ammoniacal fertilizers surface applied to winter wheat and grassland

Ammonia volatilization from urea, diammonium phosphate, ammonium sulphate and calcium ammonium nitrate surface applied to winter wheat and grassland was determined with windtunnels. The fertilizers were applied at a rate of 8–12 g N m^–2 to plots on a non-calcareous sandy loam. Five experiments were carried out during March to June 1992, each experiment including 2 to 4 treatments with two or three replications. The daily ammonia loss rate was measured during 15 to 20 days. Cumulated daily loss of ammonia from urea followed a sigmoidal expression, while the cumulated ammonia loss from diammonium phosphate showed a logarithmic relationship with time from application. For ammonium sulphate and calcium ammonium nitrate no significant loss could be determined, because daily loss of ammonia were at the detection limit of the wind tunnels. Mean cumulated ammonia loss from plots receiving urea, diammonium phosphate, ammonium sulphate and calcium ammonium nitrate were 25%, 14%, <5% and <2%, respectively, during a 15–20 day measuring period.     

Use of urease inhibitors and urea fertilizers on winter wheat

Phosphoroamide urease inhibitors were evaluated for their ability to increase grain protein and yield of winter wheat (Triticum aestivum L.) when added to surfaceapplied urea-based fertilizers. Six urease inhibitors [trichloroethyl phosphorodiamidate, diethyl phosphoric triamide, dimethyl phosphoric triamide, N-(diaminophosphinyl)-cyclohexylamine, N-benzyl-N-methyl phosphoric triamide, and phenylphosphorodiamide] were evaluated. Nitrogen treatments were urea prills, urea solution, and ureaammonium nitrate (UAN) solution broadcast and UAN solution band applied. Ammonium sulfate and no N treatments were included as controls. Fertilizer treatments were applied in the fall and spring. Soils were Ryker silt loam (Typic Paleudalf), Rensselaer loam (Typic Argiaquoll), and Avonburg silt loam (Aeric Fragiaqualf).Grain yield was a more responsive indicator of N addition than was grain N content. Urea prills and ammonium sulfate were more effective fertilizers than was UAN solution. UAN was not more effective applied in a band than broadcast. Urease inhibitors did not improve the efficiency of urea fertilizers since NH₃ volatilization did not appear to be a problem following addition of urea fertilizers in spring or fall.Journal Paper No. 10528. This work was supported in part by a grant from Allied Chemical, Solvay, NY 13209.     

The manufacture and evaluation of granular potassium chloride fertilizers

A finely divided red potassium chloride (KCl) (particle size distribution: 79% <0.5 mm, 20% 1-0.5 mm and 1% 1–2 mm) was granulated by adding eight readily available and relatively inexpensive binders using a rotating drum in the laboratory. The binders used were: urea, pulp and paper waste liquor containing lignosulphonate, urea + pulp and paper waste liquor, Borrebond powder (a commercial product containing lignosulphonate), urea + formaldehyde, ammonium sulphate, ammonium sulphate + pulp and paper waste liquor and a waste liquor containing ammonium sulphate from a Ferritin production plant. Of these, except for urea and urea + pulp and paper waste liquor which produced KCl granules having low critical relative humidity at 30°C (CRH) (<55%) and Borrebond which produced KCl granules of low crushing strength (1.1 kg for 2–3 mm granules) the other five binders produced granules with good size distributions, high crushing strengths (2.0–2.5 kg for 2–3 mm granules), CRH (65–70%) and suitable nutrient contents (K, 46–50%, Cl, 42–47%). These values are very close to those of the standard chipped KCl (crushing strength, 2.5 kg; CRH, 65–70%; K, 50%; Cl, 47%).Crushed chipped KCl (74% <1 mm, 25% 1–2 mm, 1% 2–3 mm) when cogranulated in the pilot plant with the 5 binders found successful in the laboratory, produced granules having similar characteristics as the corresponding ones produced in the laboratory. Granules produced both in the laboratory and the pilot plant had lower abrasion resistance (higher % degradation) than chipped KCl. The abrasion resistance however markedly increased when the fines (<1.4 mm) in the granules were removed.Glasshouse trials using barley as test crop demonstrated that the agronomic values of the KCl prototype granules produced with the 5 binders were similar to chipped KCl and granules produced from the feedstock KCl and water.     

Effect of amounts and sequence of additions of urea and water on hydrolysis of surface-applied granular urea in unsaturated soils

The hydrolysis of surface-applied granular urea ( 15 mg of urea/particle) in 14 unsaturated soils as influenced by the amounts and the sequence of additions of urea and water and studied using open and covered soil column systems was in the following order: well-mixed surface-applied surface-applied surface-applied urea, granular urea, granular urea, granular urea, water added > water added > water added water added before, after, before, before, no drying no drying no drying drying The retarded hydrolysis' of surface-applied granular urea is attributed to retarded soil urease activity. Under the nondrying and drying conditions, the positive effect of increasing amounts of added water on the hydrolysis was less apparent when water was added 24–48 hours before than when it was added immediately after surface application of granular urea. When an increasing number of urea granules were evenly placed on a finite surface of unsaturated soil, the rate of urea application (quantity factor) increased but the percentage of urea hydrolyzed remained practically unchanged. These results suggest that it is necessary to consider effective urea concentration and effective urease activity for adequate understanding of in situ hydrolysis of broadcast fertilizer urea in unsaturated soil.     

大峪口矿肥结合工程中采用单管式反应器工艺生产DAP／NPK

介绍湖北大峪口矿肥结合工程启动项目,采用并发展中阿公司独有的单管反应器转鼓氨化粒化技术生产DAP/NPK,单独使用铁铝镁杂质含量高的湖北矿,DAP产品各项指标符合国标优等品。该技术的突出优点是:对磷矿适应性强,生产灵活性大,容易操作。从我国磷矿资源情况来看,推广应用这种流程对磷铵生产有非常大的现实意义。     

Greenhouse evaluation of phosphorus availability from compacted phosphate rocks with urea or with urea and triple superphosphate

The possible effect of urea hydrolysis on the availability of phosphorus (P) from phosphate rock (PR) was evaluated in two greenhouse experiments with maize, using two sources of PR — Pesca (Colombia) and Bayovar (Peru) — representing low and high chemical reactivity, respectively.In Experiment I, on a neutral Josephine silty clay loam (pH 6.2) (Typic Haplozerult), Bayovar PR compacted with urea (Bayovar PR + urea) performed better than Bayovar PR compacted with NH₄Cl (Bayovar PR + NH₄Cl) in increasing dry-matter yield at a rate of 100 mg P kg^–1 but not at rates of 50 and 200 mg P kg^–1. It was also found that the dry-matter yield obtained with compacted Bayovar PR products was significantly higher when the N ratios of urea: NH₄Cl were 1:1 or higher than when the ratios were below 1:1. Although Bray I–P can overestimate available P from PR with respect to that from TSP, a good relationship was observed between Bray I–P and dry-matter yield from various compacted Bayover PR products with a small particle size (–0.43 + 0.15 mm).In Experiment II an acid Bladen sandy loam (pH 4.5) (Typic Albaquult) was used. Finely ground Bayovar PR (– 0.07 mm) was about 66% as effective as TSP in increasing dry-matter yield, whereas Pesca PR was ineffective. When Pesca PR was partially acidulated with H₃PO₄ at 20% level (PAPR), it became 70% as effective as TSP. Granulated PAPR and Pesca PR compacted with TSP (Pesca PR + TSP) were found to be equally effective in increasing dry-matter yield when both products had the same particle size and the same water-soluble and citrate-soluble P as percent of total P, and when prilled urea was used as the N source. However, when urea was compacted with Pesca PR and TSP, the product's effectiveness was further increased by 30% and to the same level as TSP.In summary, the results tend to support the suggestion that urea hydrolysis can be beneficial in increasing the availability of P from PR to plants in soils having medium to high organic matter contents.     

增效过磷酸钙肥料的生产及其对钙的缓释作用

以过磷酸钙(SSP)为主要原料,氨化中和后转鼓造粒,在包膜油和包膜粉中添加植物生长调节剂和生物菌剂,进行包膜生产增效过磷酸钙肥料,并对其进行水培及土柱淋溶实验。结果表明,增效肥料在水中的初期(前3 d)溶出率(35.17%±0.41%)显著优于过磷酸钙(33.01%±0.79%),增效肥料的钙累积溶出率(51.22%±0.10%)显著高于过磷酸钙(48.62%±1.57%)。淋溶实验表明,增效肥料包膜后,对钙的初期释放可以起到缓释作用,其中第1天达到了显著水平,包膜前为(19.14%±0.53%),包膜后为(15.20%±1.11%)。缓释增效过磷酸钙肥料可以改善过磷酸钙的理化性质。     

普钙生产新型混合反应装置的应用及经济效益

介绍了由一个喷射管和一个折流室构成的用于普钙生产的新型混合反应器。该装置结构简单、操作方便 ,能降低成本、节能。     

An assessment of granular urea/ammonium sulphate and urea/potassium nitrate fertilizers on nitrogen recovery by ryegrass

The comparative effects of ammonium sulphate (AS), potassium nitrate (KNO₃), urea (U) or combined 1:1 (w/w) U/KNO₃, U/AS granular products were investigated on dry matter (DM) yield and¹⁵N utilisation by perennial ryegrass grown under controlled environmental conditions.The DM yield and apparent N recovery with the single N sources was in the order KNO₃ > AS > U. The¹⁵N budget in shoots, roots and soil indicated that only 55% of the urea N was recovered at the end of the experiment compared with 87% and 86% for AS and KNO₃ respectively. The DM yield and apparent N recovery from the combined U/AS source was significantly higher than would be expected (P < 0.01) based on the proportions of each N source in the mixture. Differentially labelling the U and AS with¹⁵N indicated that AS enhanced the shoot % utilisation of urea by 38% (P < 0.001) whereas urea reduced the shoot % utilisation of AS by 14% (P < 0.01). These results indicate that an interaction occurred between U and AS when combined in a 1:1 (w/w) ratio in the same pellet.     

过磷酸钙混合化成尾气氟吸收系统改造

针对过磷酸钙生产中混合化成含氟尾气吸收系统存在的问题对氟吸收塔、喷头、工艺管道等进行改造。改造后提高了氟吸收率,外排气体中ρ(F)达到10 mg/m3,远低于国家标准排放限值,保证了生产的稳定运行。     

尿素熔融喷浆造粒工艺在复合肥生产过程中存在的问题及对策

介绍在团粒法工艺的基础上，将尿素熔融成尿液进行喷浆造粒生产复合肥的过程中，存在的问题，原因及解决的对策。     

Preparation and characterization of polyurethane-/MMT nanocomposite-coated urea as controlled-release fertilizers

ABSTRACT

A new nanocomposite coating was synthesized by MMT and polyurethane for controlled-release fertilizers (CRFs). The structure and properties of samples were characterized. The nutrient release behavior of nanocomposite-coated fertilizers (MPUs) and polyurethane-coated fertilizers (PU) in water and in soil were determined. SEM and TEM exhibited good dispersion of MMT lamellae in the MPU coatings. The results also showed that the water contact angle of the MPU coating was greatly improved, the water absorption was reduced by 65.7%, and the coating porosity was reduced by 30.0%. In addition, MPUs exhibited longer nutrient release longevity than that of PU (26 days), especially MPU with 5% MMT (90 days). Therefore, MPUs with excellent properties can provide information for the development of CRFs.     

Non hygroscopic superphosphate fertilizer from apatite and hydrochloric acid

A method is described for the production of a nonhygroscopic fertilizer from apatite by treatment with hydrochloric acid.Apatite is acidulated with HCl to the stoichiometric level needed for generating dicalcium phosphate. The reaction product when mixed with ammonium sulphate sufficient to doubledecompose calcium chloride and dicalcium phosphate yields a nonhygroscopic product containing almost all phosphorus in the water-soluble form. Results of laboratory experiments conducted to determine the optimum conditions for the process, chemical properties of the material and its agronomic effectiveness are described. The studies were carried out with the intention of utilizing the reserve of apatite at Eppawala in Sri Lanka using indegenous raw materials.     

A comparative study of urea hydrolysis rate and ammonia volatilization from urea and urea calcium nitrate

A comparing of urea hydrolysis and NH₃ volatilization from urea supergranules and urea calcium nitrate (UCN, a new fertilizer produced by Norsk Hydro A/S, Norway) was made on two different flooded soil types, a high-CEC clay loam (Ås) and an intermediate-CEC clay loam (Kinn).Nitrogen loss by ammonia volatilization was reduced from 17% by surface application of urea supergranules (USG) on flooded Ås soil to 3% and 6% by UCN briquettes at either the same urea or nitrogen concentration as USG. A significant reduction was even found with the surface application of prilled UCN, 12% and 18% N-loss for prilled UCN and urea, respectively. The floodwater pH and NH ₄ ⁺ content was lower with UCN than urea, which reduced the potential for ammonia volatilization.NH₃-loss (5%) was significantly less when USG was surface applied on Kinn soil, while NH₃-loss from UCN briquettes was independent of soil type. The reduction in NH₃-loss from USG on Kinn soil was due to a decrease in the pH and NH ₄ ⁺ content of the floodwater caused by a reduced rate of urea hydrolysis.The rate of urea hydrolysis was lower with UCN than USG in both soils, but the difference between UCN and USG was greater in the Ås soil than in the Kinn soil. Three days after deep placement (10 cm), 18% of UCN urea and 52% of USG urea were hydrolyzed in Ås soil, while only 12% UCN and 17% USG were hydrolyzed in the Kinn soil.The surface application of USG on flooded soil reduced the rate of urea hydrolysis as compared to deep placement. 30% and 17% of USG urea was hydrolyzed after four days on Ås and Kinn soil, respectively. During the first few days the rate of hydrolysis of UCN was more affected by the soil type than the application method. Four days after surface application 32% and 13% UCN urea was hydrolyzed on Ås and Kinn soil, respectively. The rate of urea hydrolysis exhibited a zero-order reaction when USG and UCN-briquettes were point placed in flooded soils.     

Slow-release urea fertilizers — effect on floodwater chemistry,ammonia volatilization and rice growth in an alkali soil

In experiments with transplanted rice (Oryza sativa L.) at the Central Soil Salinity Research Institute, Karnal, India, two methods of application of granular urea, wholly as basal dose U(W) or in splits U(S) were compared with deep, point placement (8 cm) of urea supergranules and broadcast application of two slow-release sources, sulphur-coated urea (SCU) and lac-coated urea (LCU). Comparisons were made in wet season 1984 and 1985 on the basis of ammoniacal N concentration and pH of floodwater, ammonia volatilization, rice yield and N uptake.In 1984 the highest peak concentrations of ammoniacal N (AN) in the floodwater, > 12g m^–3, and ammonia volatilization losses 54% of applied N were produced in U(W). Application of N in splits U(S) reduced peak AN levels 5g m^–3 and losses to 45.1%. LCU was ineffective in reducing peak AN levels ( 7.5g m^–3) or losses (43.6%). However SCU and USG were effective in reducing peak AN levels to < 2g m^–3 and N losses to 16.9 and 3.4% respectively. Total ammonia volatilization losses as well as the initial rate of loss correlated very well with the peak levels (second day) of AN, NH₃ (aq.) as well as equilibrium vapour pressure of NH₃. Floodwater pH was between 9.5 and 10.0.Split application of granular urea was generally more efficient in terms of yield and N recovery (41.4%, average of two years) as compared to whole application (29.5%). LCU was ineffective in improving grain yields or N recovery (30.9%). SCU was ineffective in improving grain yields but improved N recovery to 57.9%., USG increased grain yields only in first year by 19% over U(S) and improved N uptake to 60.5%. A negative linear relationship was established between N uptake by rice at harvest and AN levels in floodwater two days after fertilization which can be used as an index to evaluate fertilizers.