The decomposition mechanism of ammonium sulfate catalyzed by ferric oxide was investigated in this paper. The decomposition kinetics parameters were determined via a global optimization of the Kissinger iterative meth...The decomposition mechanism of ammonium sulfate catalyzed by ferric oxide was investigated in this paper. The decomposition kinetics parameters were determined via a global optimization of the Kissinger iterative method using the non-isothermal thermogravi- metric analysis data. The products and intermediates were synchronously characterized by X-ray diffraction and mass spectrometry. The obtained results indicate that the decomposition process of ammonium sulfate catalyzed by ferric oxide can be divided into four stages of which the activation energies are 123.64, 126.58, 178.77 and 216.99 kJ. mol^-1 respectively. The decomposition mechanisms at the first and the fourth stage both belong to Mample power theorem, the second stage belongs to Avrami-Erofeev equation and the third belongs to contracting sphere （volume） equation. The corresponding pre-exponential factors （A） are calculated simultaneously.展开更多
Ammonium sulfate residue is a particulate solid and is produced during the manufacture of ammonium sulfate fertilizer. The residue used in this study contained a large portion of calcium carbonate, from which active l...Ammonium sulfate residue is a particulate solid and is produced during the manufacture of ammonium sulfate fertilizer. The residue used in this study contained a large portion of calcium carbonate, from which active lime （CaO） was recovered via thermal decomposition. We used a purpose-built device to decom- pose the residue in a semi-suspension state. We found that CaO had the highest activity when residue was decomposed at 850-900 ~C. Our experiments indicated that ammonium sulfate residue should be decom- posed in a suspension state to produce active CaO. Based on our laboratory test findings, an industrial-scale production line with a high solid/gas ratio in a suspension state was devised. The optimal operating con- ditions for the decomposition of the ammonium sulfate residue to produce high quality CaO were also investigated.We found that the CaCO3 decomposition rate was high and the CaO product was highly active, averaging 170 s by the citric acid method. Morphology measurements showed that the CaO product had a porous structure and a large specific surface ensuring high activity.展开更多
This paper describes a novel, facile chemical pathway for preparing synthetic rutile from ilmenite. The pathway consists of two primary units, i.e., selectively sulfating ilmenite, which was realized via roasting ilme...This paper describes a novel, facile chemical pathway for preparing synthetic rutile from ilmenite. The pathway consists of two primary units, i.e., selectively sulfating ilmenite, which was realized via roasting ilmenite with(NH_4)_2SO_4followed by selective thermal decomposition of the sulfated ilmenite, and targeted leaching of the impurities. The effects of the process parameters were systematically investigated. The results showed that the optimum sulfation conditions were a mass ratio of(NH_4)_2SO_4to ilmenite of 14, temperature of 360 °C, and time of 120 min with a sulfation ratio of ~ 95%. The optimum thermal decomposition conditions were480 °C in N_2 atmosphere, and nearly all Ti OSO_4 were decomposed with co-decomposition of Fe SO_4 of 23%. For acid leaching, the optimum conditions were 2.5 wt% HCl, 98 °C and 120 min. Under those conditions, 94.2% iron was removed with a Ti O_2 dissolution loss b 1%. For alkali leaching, 67% Si O_2 was removed in 5 wt% Na OH at102 °C for 1 h. A synthetic rutile with a Ti O_2 content N 92 wt% and total Mg O + Ca O b 1.5 wt% was obtained.Based on these results, a schematic flowsheet was proposed. Additionally, it was found that the decomposition of Fe SO_4 mixed with Ti OSO_4 under N_2was inhibited due to its oxidation to a higher thermal stability Fe_2(SO_4)_3by oxygen emitted from the decomposition of Ti OSO_4. At the same time, Ti OSO_4 decomposition was promoted due to the immediate in situ consumption of oxygen by Fe SO_4. The synergetic effect might be responsible for the enhanced selectivity of sulfated ilmenite thermal decomposition.展开更多
In this paper,on the basis of chemical analysis and IR analysis,the mechanism of the thermal decomposition for ammonium sulfate was put forward.The thermal decomposition process consists of three steps:ammonium bisulf...In this paper,on the basis of chemical analysis and IR analysis,the mechanism of the thermal decomposition for ammonium sulfate was put forward.The thermal decomposition process consists of three steps:ammonium bisulfate was produced firstly,ammonium pyrosulfate secondly,and broken down into NH 3,SO 2,and others lastly.The relation between the rate of decomposition and the atmosphere was discussed.展开更多
文摘The decomposition mechanism of ammonium sulfate catalyzed by ferric oxide was investigated in this paper. The decomposition kinetics parameters were determined via a global optimization of the Kissinger iterative method using the non-isothermal thermogravi- metric analysis data. The products and intermediates were synchronously characterized by X-ray diffraction and mass spectrometry. The obtained results indicate that the decomposition process of ammonium sulfate catalyzed by ferric oxide can be divided into four stages of which the activation energies are 123.64, 126.58, 178.77 and 216.99 kJ. mol^-1 respectively. The decomposition mechanisms at the first and the fourth stage both belong to Mample power theorem, the second stage belongs to Avrami-Erofeev equation and the third belongs to contracting sphere （volume） equation. The corresponding pre-exponential factors （A） are calculated simultaneously.
基金Wengfu Phosphate Fertilizer Plant(WPFP),WengFu(Group) Co.,Ltd,Guizhou,China for financial supportgrants from National Science and Technology Support Program(No.2012BAA08B00)Science and Technology Integrated Innovation Project of Shaanxi Province(No.2012KTZB03-04)
文摘Ammonium sulfate residue is a particulate solid and is produced during the manufacture of ammonium sulfate fertilizer. The residue used in this study contained a large portion of calcium carbonate, from which active lime （CaO） was recovered via thermal decomposition. We used a purpose-built device to decom- pose the residue in a semi-suspension state. We found that CaO had the highest activity when residue was decomposed at 850-900 ~C. Our experiments indicated that ammonium sulfate residue should be decom- posed in a suspension state to produce active CaO. Based on our laboratory test findings, an industrial-scale production line with a high solid/gas ratio in a suspension state was devised. The optimal operating con- ditions for the decomposition of the ammonium sulfate residue to produce high quality CaO were also investigated.We found that the CaCO3 decomposition rate was high and the CaO product was highly active, averaging 170 s by the citric acid method. Morphology measurements showed that the CaO product had a porous structure and a large specific surface ensuring high activity.
基金Supported by the National Key Projects for Fundamental Research and Development of China(2016YFB0600904)
文摘This paper describes a novel, facile chemical pathway for preparing synthetic rutile from ilmenite. The pathway consists of two primary units, i.e., selectively sulfating ilmenite, which was realized via roasting ilmenite with(NH_4)_2SO_4followed by selective thermal decomposition of the sulfated ilmenite, and targeted leaching of the impurities. The effects of the process parameters were systematically investigated. The results showed that the optimum sulfation conditions were a mass ratio of(NH_4)_2SO_4to ilmenite of 14, temperature of 360 °C, and time of 120 min with a sulfation ratio of ~ 95%. The optimum thermal decomposition conditions were480 °C in N_2 atmosphere, and nearly all Ti OSO_4 were decomposed with co-decomposition of Fe SO_4 of 23%. For acid leaching, the optimum conditions were 2.5 wt% HCl, 98 °C and 120 min. Under those conditions, 94.2% iron was removed with a Ti O_2 dissolution loss b 1%. For alkali leaching, 67% Si O_2 was removed in 5 wt% Na OH at102 °C for 1 h. A synthetic rutile with a Ti O_2 content N 92 wt% and total Mg O + Ca O b 1.5 wt% was obtained.Based on these results, a schematic flowsheet was proposed. Additionally, it was found that the decomposition of Fe SO_4 mixed with Ti OSO_4 under N_2was inhibited due to its oxidation to a higher thermal stability Fe_2(SO_4)_3by oxygen emitted from the decomposition of Ti OSO_4. At the same time, Ti OSO_4 decomposition was promoted due to the immediate in situ consumption of oxygen by Fe SO_4. The synergetic effect might be responsible for the enhanced selectivity of sulfated ilmenite thermal decomposition.
文摘In this paper,on the basis of chemical analysis and IR analysis,the mechanism of the thermal decomposition for ammonium sulfate was put forward.The thermal decomposition process consists of three steps:ammonium bisulfate was produced firstly,ammonium pyrosulfate secondly,and broken down into NH 3,SO 2,and others lastly.The relation between the rate of decomposition and the atmosphere was discussed.
