Vacuum pyrolysis was employed to dispose scrap brominated epoxy printed circuit boards (PCBs).Pyrolysis characteristics of waste PCBs under normal pressure and vacuum were investigated in this paper.A detailed study o...Vacuum pyrolysis was employed to dispose scrap brominated epoxy printed circuit boards (PCBs).Pyrolysis characteristics of waste PCBs under normal pressure and vacuum were investigated in this paper.A detailed study on the analysis of the elemental composition of PCBs and the pyrolysis products was performed.The thermal decomposition kinetics was measured by a thermogravimetric (TG) analyzer.The activation energy of pyrolysis under nitrogen atmosphere and vacuum were 193 kJ/mol to 206 kJ/mol and 145 kJ/mol to 165 kJ/mol,respectively.The composition of materials was analyzed by elemental analyzer.The pyrolysis products were analyzed by GC (gas chromatograph),GC-MS (chromatography and mass spectrometry) and FT-IR (Fourier transform infrared spectroscopy).Vacuum helped to increase the yield of pyrolysis oil.The liquid yield of PCBs pyrolysis at 15 kPa and normal pressure were 31.3% and 23.5%,respectively.The main components in pyrolysis oils were phenol,isopropyl-phenol,and their brominated substitution.展开更多
Waste print circuit board containing 11.38% Br was pyrolyzed in vacuum. Thermal stability of waste print circuit board was studied under vacuum condition by thermo-gravimetry(TG). Vacuum pyrolysis of WPCB was studied ...Waste print circuit board containing 11.38% Br was pyrolyzed in vacuum. Thermal stability of waste print circuit board was studied under vacuum condition by thermo-gravimetry(TG). Vacuum pyrolysis of WPCB was studied emphasizing on the kinetics of WPCB pyrolysis reactions. Based on the TG results, a kinetic model was pro- posed. Kinetic parameters were calculated for reaction with this model including all stages of decomposition. The average activation energy is 68 kJ/mol with reaction order 3. These findings provide new insights into the WPCB thermal decomposition and useful data for rational design and operation of pyrolysis.展开更多
This paper analyzes the observing results of vacuum degree in the the Jialichen bridge-head experimental site .The cause of vacuum degree developing below groundwater table is pointed out. The influence of vacuum degr...This paper analyzes the observing results of vacuum degree in the the Jialichen bridge-head experimental site .The cause of vacuum degree developing below groundwater table is pointed out. The influence of vacuum degree above the ground water table on pore water pressure is discussed. The results show that vacuum degree decreases along the depth because resistance. The resistance in the PVDS is lowest, in the silt is highest. Vacuum degree below groundwater table is produced mainly by dewatering or by escaping of sealed air from the end of flexible pipe. Vacuum degree above the ground water table in the sand drains makes great effect on pore water pressure. In the silt the pore water pressure does not change with the variation of vacuum degree under membrane in a short time.展开更多
Chalkboard erasers that are commonly used in many schools and education organizations have <span>the </span><span>poor ability in removing the dust off the chalkboard and collect them. The dust that ...Chalkboard erasers that are commonly used in many schools and education organizations have <span>the </span><span>poor ability in removing the dust off the chalkboard and collect them. The dust that is not collected will be taken into human bodies via inhalation, which will lead to respiratory diseases. Therefore, it is crucial to design a chalkboard eraser that can collect the dust effectively. If the eraser can be controlled both remotely and manually by people, it can further reduce the amount of dust taken in by human bodies. To achieve remote control, a micro-controller is needed to transfer the infrared radiation (IR) into signals that can control electric motors to move around on the chalkboard. Furthermore, the microfiber is also used as the cleaning material to improve the performance of dust cleaning and collecting. A vacuum pump is needed to create negative pressure between the eraser and the chalkboard so that the eraser can stick to it. The result shows a stronger ability in removing and collecting dust. With the help of the Arduino UNO board, the remote control is successfully achieved, and the eraser can move on the chalkboard freely according to the order.</span>展开更多
<正> The volatilization behavior of Cu, Pb, Sn, Sb, Ni, Zn, Mn, Co, Cr, Cd during pyrolysis of waste printed circuit boards was investigated in a bench-scale fixed-bed pyrolysis system. It was found that volatil...<正> The volatilization behavior of Cu, Pb, Sn, Sb, Ni, Zn, Mn, Co, Cr, Cd during pyrolysis of waste printed circuit boards was investigated in a bench-scale fixed-bed pyrolysis system. It was found that volatility of heavy metals increases with operating temperature elevating, and bromine and vacuum have an obvious promoting effect on volatility of most of heavy metals. Over 99% weight of Cu and Ni are still remained in solid residue after pyrolysis, about 20% weight of Sb, Zn and Cd are transfered into liquid and gas during a pyrolysis process at 600℃, volatilization fractions of Pb, Sn, Mn, Co, Cr are less than 10% at the same conditions. The contents of heavy metals in liquid and gas products depend on not only volatility of metals, but also their initial contents in printed circuit boards, pyrolysis liquid and gas are primarily contaminated by Cu, Pb, Sn, Sb and Zn, their contents in liquid vary from 10~2 to 10~3 μg/mL, Mn, Co, Cr, Cd were detected only at very low level, less than 10 μg/mL.展开更多
基金Funded by the National High Technology Research and Development Key Program of China (No. 2006AA06Z375)
文摘Vacuum pyrolysis was employed to dispose scrap brominated epoxy printed circuit boards (PCBs).Pyrolysis characteristics of waste PCBs under normal pressure and vacuum were investigated in this paper.A detailed study on the analysis of the elemental composition of PCBs and the pyrolysis products was performed.The thermal decomposition kinetics was measured by a thermogravimetric (TG) analyzer.The activation energy of pyrolysis under nitrogen atmosphere and vacuum were 193 kJ/mol to 206 kJ/mol and 145 kJ/mol to 165 kJ/mol,respectively.The composition of materials was analyzed by elemental analyzer.The pyrolysis products were analyzed by GC (gas chromatograph),GC-MS (chromatography and mass spectrometry) and FT-IR (Fourier transform infrared spectroscopy).Vacuum helped to increase the yield of pyrolysis oil.The liquid yield of PCBs pyrolysis at 15 kPa and normal pressure were 31.3% and 23.5%,respectively.The main components in pyrolysis oils were phenol,isopropyl-phenol,and their brominated substitution.
基金Supported by Science and Technology Research Project of Guangdong Province(2003e32104)
文摘Waste print circuit board containing 11.38% Br was pyrolyzed in vacuum. Thermal stability of waste print circuit board was studied under vacuum condition by thermo-gravimetry(TG). Vacuum pyrolysis of WPCB was studied emphasizing on the kinetics of WPCB pyrolysis reactions. Based on the TG results, a kinetic model was pro- posed. Kinetic parameters were calculated for reaction with this model including all stages of decomposition. The average activation energy is 68 kJ/mol with reaction order 3. These findings provide new insights into the WPCB thermal decomposition and useful data for rational design and operation of pyrolysis.
文摘This paper analyzes the observing results of vacuum degree in the the Jialichen bridge-head experimental site .The cause of vacuum degree developing below groundwater table is pointed out. The influence of vacuum degree above the ground water table on pore water pressure is discussed. The results show that vacuum degree decreases along the depth because resistance. The resistance in the PVDS is lowest, in the silt is highest. Vacuum degree below groundwater table is produced mainly by dewatering or by escaping of sealed air from the end of flexible pipe. Vacuum degree above the ground water table in the sand drains makes great effect on pore water pressure. In the silt the pore water pressure does not change with the variation of vacuum degree under membrane in a short time.
文摘Chalkboard erasers that are commonly used in many schools and education organizations have <span>the </span><span>poor ability in removing the dust off the chalkboard and collect them. The dust that is not collected will be taken into human bodies via inhalation, which will lead to respiratory diseases. Therefore, it is crucial to design a chalkboard eraser that can collect the dust effectively. If the eraser can be controlled both remotely and manually by people, it can further reduce the amount of dust taken in by human bodies. To achieve remote control, a micro-controller is needed to transfer the infrared radiation (IR) into signals that can control electric motors to move around on the chalkboard. Furthermore, the microfiber is also used as the cleaning material to improve the performance of dust cleaning and collecting. A vacuum pump is needed to create negative pressure between the eraser and the chalkboard so that the eraser can stick to it. The result shows a stronger ability in removing and collecting dust. With the help of the Arduino UNO board, the remote control is successfully achieved, and the eraser can move on the chalkboard freely according to the order.</span>
基金Supported by Science Technology Research Project of Guangdong Province(2003e32104)
文摘<正> The volatilization behavior of Cu, Pb, Sn, Sb, Ni, Zn, Mn, Co, Cr, Cd during pyrolysis of waste printed circuit boards was investigated in a bench-scale fixed-bed pyrolysis system. It was found that volatility of heavy metals increases with operating temperature elevating, and bromine and vacuum have an obvious promoting effect on volatility of most of heavy metals. Over 99% weight of Cu and Ni are still remained in solid residue after pyrolysis, about 20% weight of Sb, Zn and Cd are transfered into liquid and gas during a pyrolysis process at 600℃, volatilization fractions of Pb, Sn, Mn, Co, Cr are less than 10% at the same conditions. The contents of heavy metals in liquid and gas products depend on not only volatility of metals, but also their initial contents in printed circuit boards, pyrolysis liquid and gas are primarily contaminated by Cu, Pb, Sn, Sb and Zn, their contents in liquid vary from 10~2 to 10~3 μg/mL, Mn, Co, Cr, Cd were detected only at very low level, less than 10 μg/mL.
