Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the n...Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the new emissions standards. In this paper, urea deposit samples collected from engine test bed and tube furnace were characterized by thermogravimetric analysis and Fourier transform-infrared analysis to aid the comprehension of urea deposit formation. Moreover, thermogravimetric tests were conducted to disclose the effects of catalyst on the thermal decomposition processes of urea deposit. The results indicated that less temperature resistant species are formed in the engine test bed than in the tube furnace at conditions with the same temperatures. The main compositions in the World Harmonized Transient Cycle(WHTC) urea deposits are urea, cyanuric acid(CYA) and ammelide, implying that accelerating the decomposition of these species could prevent the accumulation of urea deposit. CuWTi, Cu β and CuZSM catalysts could lead to increased yield of CYA during pure urea thermolysis. Cu β, CuWTi and VWTi catalysts tend to promote the thermolysis of CYA while VWTi has the most significant catalytic effects on the thermal decomposition of ammelide and ammeline.展开更多
The Ni-La alloy was electro-deposited in urea-NaBr melt. The codeposition behavior and effect of the cathodic current density on the coating composition were examined. As a result, lanthanum codeposited with nickel to...The Ni-La alloy was electro-deposited in urea-NaBr melt. The codeposition behavior and effect of the cathodic current density on the coating composition were examined. As a result, lanthanum codeposited with nickel to form Ni-La alloy under the inducement effect of nickel. With the increase of the cathodic current density, the content of lanthanum of the deposit rose at first, then decreased, and reached the maximal value (10.3%(atom fraction)) at the current density 15 mA·cm-2. The crystallization behavior of Ni89.7La10.3 coating was investigated by means of differential scanning calorimetry and X-ray diffraction. The structure of Ni89.7La10.3 as-plated coating was amorphous phase. The amorphous phase was converted into center cubic close packed Ni-La (Fm3m) solid solution at 469.8 ℃. The electro-catalytic activity of hydrogen evolution of Ni89.7La10.3 coating was studied using electrochemical experiments, the results showed that the electro-catalytic activity of hydrogen evolution of Ni89.7La10.3 coating was better than that of nickel.展开更多
The fertiliser industry faces a continuing challenge to improve the efficiency of their products,particularly of nitrogenous fertilisers,and to minimise adverse impacts.Therefore,a new slow release fertilizer,ureaimpr...The fertiliser industry faces a continuing challenge to improve the efficiency of their products,particularly of nitrogenous fertilisers,and to minimise adverse impacts.Therefore,a new slow release fertilizer,ureaimpregnated woodchips from tropical plant biomass(oil palm frond and rubberwood),was developed.The morphology of the impregnated woodchips was investigated by scanning electron microscopy and the success of impregnation of urea and nitrogen deposition into the woodchips was confirmed by energy dispersive X-ray spectrometry.When nitrogen release patterns from impregnated woodchips fertiliser were simulated using a soil solution and distilled water as leaching solutions in a static condition for 768 h,release was slow and steady,although the release rate was lower in distilled water than in the soil solution.展开更多
The kinetics of La-Co alloy film in acetamide-urea-NaBr molten salt electrolyte at 353K was investigated. It is shown that the reduction of Co(Ⅱ) to Co is irreversible reaction with the transfer coefficient of 0.28...The kinetics of La-Co alloy film in acetamide-urea-NaBr molten salt electrolyte at 353K was investigated. It is shown that the reduction of Co(Ⅱ) to Co is irreversible reaction with the transfer coefficient of 0.28 and the diffusion coefficient of 7.46×10 -5 cm 2/s. While La(Ⅲ) cannot be reduced to La directly; but can be codeposited with cobalt. The content of La in the uncrystallized La-Co alloy film increases with increasing cathodic overpotential, molar ratio of La 3+ to Co 2+ and electrolysis time as well, and reaches the maximum of 66.32%.展开更多
The reduction of Ni(Ⅱ) is an irreversible reaction and La(Ⅲ) cannot be reduced to La directly but be co-deposited inductively in the present of Ni(Ⅱ) in the Acetamide-Urea-NaBr molten salt electrolyte at 353 K. The...The reduction of Ni(Ⅱ) is an irreversible reaction and La(Ⅲ) cannot be reduced to La directly but be co-deposited inductively in the present of Ni(Ⅱ) in the Acetamide-Urea-NaBr molten salt electrolyte at 353 K. The uncrystallized alloy film of La-Ni is obtained by potentiostatic electrolysis, and the amount of La grows with increasing cathodic overpotential, molar ratios of La(Ⅲ) to Ni(Ⅱ) and the electrolysis time. The maximum amount of La in alloy film reaches to 78.81% (mass fraction) in present study.展开更多
在353K的乙酰胺-尿素-N aB r熔体中,P t、Cu电极上,Co(Ⅱ)+2e→Co(0)是一步完全不可逆反应,测得0.060m o l.L-1CoC l2-乙酰胺-尿素-N aB r中,Co(Ⅱ)在P t上,传递系数α=0.28,扩散系数D0=4.68×10-5cm2.-s 1,Cu上α=0.28,D0=4.06...在353K的乙酰胺-尿素-N aB r熔体中,P t、Cu电极上,Co(Ⅱ)+2e→Co(0)是一步完全不可逆反应,测得0.060m o l.L-1CoC l2-乙酰胺-尿素-N aB r中,Co(Ⅱ)在P t上,传递系数α=0.28,扩散系数D0=4.68×10-5cm2.-s 1,Cu上α=0.28,D0=4.06×1-0 7cm2.-s 1。G d(Ⅲ)不能单独还原为G d(0),但可以被Co(Ⅱ)诱导共沉积。由恒电位电解法得到非晶态的G d-Co合金,G d的含量随阴极电位的负移,G d(Ⅲ)/N i(Ⅱ)摩尔比增大以及电解时间延长而增大。展开更多
A new design of a selective catalytic reduction(SCR)mixer called tornado was developed for a heavy-duty diesel engine to solve the urea deposition problem.A combination of CFD simulation and experimental studies was u...A new design of a selective catalytic reduction(SCR)mixer called tornado was developed for a heavy-duty diesel engine to solve the urea deposition problem.A combination of CFD simulation and experimental studies was used to comprehensively evaluate the performance of the tornado mixer.According to the numerical simulations,this mixer can improve the front surface flow uniformity of the SCR carrier by 6.67%and the NH3 distribution uniformity by 3.19%compared to a traditional mixer.Similarly,steady state SCR conversion efficiency test results have shown that the tornado mixer can increase the average SCR conversion efficiency by 1.73%compared to a traditional mixer.Therefore,the tornado mixer outperforms traditional mixers in terms of mixing uniformity,resistance to deposition and impact on NOX emissions.In addition,a dimensionless parameter,the“limiting deviation rate”,is proposed in the present study to improve the mixing uniformity assessment method for SCR mixers(with the explicit intent to evaluate the mixing uniformity more accurately).展开更多
基金supported by the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2018A10)the Science Fund for Young Scholars of Natural Science Fund in Hebei Province(No.E2019202198)+1 种基金the Science and Technology Research Project of Colleges and Universities in Hebei Province(No.QN2019056)the State Key Laboratory of Engines,Tianjin University(No.K2020-15)。
文摘Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the new emissions standards. In this paper, urea deposit samples collected from engine test bed and tube furnace were characterized by thermogravimetric analysis and Fourier transform-infrared analysis to aid the comprehension of urea deposit formation. Moreover, thermogravimetric tests were conducted to disclose the effects of catalyst on the thermal decomposition processes of urea deposit. The results indicated that less temperature resistant species are formed in the engine test bed than in the tube furnace at conditions with the same temperatures. The main compositions in the World Harmonized Transient Cycle(WHTC) urea deposits are urea, cyanuric acid(CYA) and ammelide, implying that accelerating the decomposition of these species could prevent the accumulation of urea deposit. CuWTi, Cu β and CuZSM catalysts could lead to increased yield of CYA during pure urea thermolysis. Cu β, CuWTi and VWTi catalysts tend to promote the thermolysis of CYA while VWTi has the most significant catalytic effects on the thermal decomposition of ammelide and ammeline.
基金the Natural Science Foundation of Fujian Province of China (E0640004)
文摘The Ni-La alloy was electro-deposited in urea-NaBr melt. The codeposition behavior and effect of the cathodic current density on the coating composition were examined. As a result, lanthanum codeposited with nickel to form Ni-La alloy under the inducement effect of nickel. With the increase of the cathodic current density, the content of lanthanum of the deposit rose at first, then decreased, and reached the maximal value (10.3%(atom fraction)) at the current density 15 mA·cm-2. The crystallization behavior of Ni89.7La10.3 coating was investigated by means of differential scanning calorimetry and X-ray diffraction. The structure of Ni89.7La10.3 as-plated coating was amorphous phase. The amorphous phase was converted into center cubic close packed Ni-La (Fm3m) solid solution at 469.8 ℃. The electro-catalytic activity of hydrogen evolution of Ni89.7La10.3 coating was studied using electrochemical experiments, the results showed that the electro-catalytic activity of hydrogen evolution of Ni89.7La10.3 coating was better than that of nickel.
基金supported by Research University Grant Scheme(RUGS)University Putra Malaysia(No.03-02-12-2293RU)
文摘The fertiliser industry faces a continuing challenge to improve the efficiency of their products,particularly of nitrogenous fertilisers,and to minimise adverse impacts.Therefore,a new slow release fertilizer,ureaimpregnated woodchips from tropical plant biomass(oil palm frond and rubberwood),was developed.The morphology of the impregnated woodchips was investigated by scanning electron microscopy and the success of impregnation of urea and nitrogen deposition into the woodchips was confirmed by energy dispersive X-ray spectrometry.When nitrogen release patterns from impregnated woodchips fertiliser were simulated using a soil solution and distilled water as leaching solutions in a static condition for 768 h,release was slow and steady,although the release rate was lower in distilled water than in the soil solution.
文摘The kinetics of La-Co alloy film in acetamide-urea-NaBr molten salt electrolyte at 353K was investigated. It is shown that the reduction of Co(Ⅱ) to Co is irreversible reaction with the transfer coefficient of 0.28 and the diffusion coefficient of 7.46×10 -5 cm 2/s. While La(Ⅲ) cannot be reduced to La directly; but can be codeposited with cobalt. The content of La in the uncrystallized La-Co alloy film increases with increasing cathodic overpotential, molar ratio of La 3+ to Co 2+ and electrolysis time as well, and reaches the maximum of 66.32%.
文摘The reduction of Ni(Ⅱ) is an irreversible reaction and La(Ⅲ) cannot be reduced to La directly but be co-deposited inductively in the present of Ni(Ⅱ) in the Acetamide-Urea-NaBr molten salt electrolyte at 353 K. The uncrystallized alloy film of La-Ni is obtained by potentiostatic electrolysis, and the amount of La grows with increasing cathodic overpotential, molar ratios of La(Ⅲ) to Ni(Ⅱ) and the electrolysis time. The maximum amount of La in alloy film reaches to 78.81% (mass fraction) in present study.
文摘A new design of a selective catalytic reduction(SCR)mixer called tornado was developed for a heavy-duty diesel engine to solve the urea deposition problem.A combination of CFD simulation and experimental studies was used to comprehensively evaluate the performance of the tornado mixer.According to the numerical simulations,this mixer can improve the front surface flow uniformity of the SCR carrier by 6.67%and the NH3 distribution uniformity by 3.19%compared to a traditional mixer.Similarly,steady state SCR conversion efficiency test results have shown that the tornado mixer can increase the average SCR conversion efficiency by 1.73%compared to a traditional mixer.Therefore,the tornado mixer outperforms traditional mixers in terms of mixing uniformity,resistance to deposition and impact on NOX emissions.In addition,a dimensionless parameter,the“limiting deviation rate”,is proposed in the present study to improve the mixing uniformity assessment method for SCR mixers(with the explicit intent to evaluate the mixing uniformity more accurately).
