Conversion of Waste High-Density Polyethylene into Liquid Fuels

By: Kumar, SachinContributor(s): Singh, R K [Supervisor] | Department of Chemical EngineeringMaterial type: TextTextLanguage: English Publisher: 2014Description: 231 pSubject(s): Engineering and Technology | Chemical EngineeringOnline resources: Click here to access online Dissertation note: Thesis (Ph.D)- National Institute of Technology, Rourkela Summary: The present work involves the experimental studies for the production of liquid fuel by thermal and catalytic pyrolysis of waste high-density polyethylene in a laboratory batch reactor. Thermal pyrolysis of virgin HDPE was performed at a temperature range from 400 °C to 550 °C and heating rate of 20 °C/min. The liquid yield is highest 50 wt. % at temperature 450 ºC. Reaction time decreases with increase in temperature. Maximum oil yield in thermal pyrolysis of waste HDPE was 50.8 wt. % at optimum condition of temperature, which is improved to 58.8 wt. %, in kaolin catalyzed degradation under optimum condition of temperature and feed ratio. The rate of reaction, oil yield and quality of oil obtained in the catalytic pyrolysis are significantly improved as compared to thermal pyrolysis. The catalytic activity of kaolin is further enhanced by treating it with four different acids and one base (acetic acid, phosphoric acid, nitric acid, hydrochloric acid and sodium hydroxide). Acid treatment increased the surface area, acidity and also alters the pore volume distribution of kaolin, which support the cracking reaction. The maximum yield of oil in the acid treated kaolin catalyzed pyrolysis of waste HDPE was 79% under optimum conditions. The composition of the oil was analyzed by FTIR and GC-MS. The oil obtained from the catalytic pyrolysis of waste HDPE mostly contains aliphatic hydrocarbons. The fuel properties of the oil obtained from the catalytic pyrolysis of waste HDPE is similar with that of petro-fuels. So they can directly be used as an engine fuel after fractionation or as a feedstock to petroleum refineries. Response surface methodology (RSM) was used to optimize the catalytic pyrolysis process of waste high-density polyethylene to liquid fuel over modified catalyst. The reaction temperature, acidity of the modified catalysts and mass ratio between modified catalysts to waste high-density polyethylene (HDPE) were chosen as independent variables. Optimum operating conditions of reaction temperature (450 °C), acidity of catalyst (0.341) and catalyst to waste HDPE ratio (1:4) were produced with respect to Abstract x maximum liquid product yield of 78.7 %. The polynomial model obtained fits well to predict the response with a high determination coefficient of R2 (0.995). The diesel blended plastic oil obtained by the catalytic pyrolysis of waste HDPE has been tested for its performance and emission in a CI diesel engine. Engine was able to run with maximum 40% waste plastic oil- diesel blends. The engine vibrates at and above this blend. Brake thermal efficiency of the waste HDPE oil blend is lower to diesel at all loads. This may be due to lower calorific value of Waste HDPE Oil-diesel blend than diesel. The BSEC increases with the increasing WPO blend ratio at all engine loads and decreases with increase in engine load. Mechanical efficiency increases with increasing brake power for all fuel blends. The NOx emission increases with increase in percentage of waste plastic oil in blends and decreases with increase in engine load. The unburnt hydrocarbon emission is decreasing with increase in the engine load and increases with increase in percentage of waste plastic oil in blends. The CO emission increases with the increasing WPO blend ratio and engine load. The carbon dioxide emission for the blends is lower than diesel for almost all loads and all blends. The thermo gravimetric analysis of waste HDPE at 10 ºC/min, 20 ºC/min and 40 ºC/min in the N2 atmosphere was studied and kinetic parameter (activation energy) was determined by using thermogravimetric curves. When the heating rate increases, the activation energy and degradation temperature of the waste HDPE also increases. The activation energy values of waste HDPE have been calculated as 207.43, 268.22 and 473.05 kJ/mol at 10, 20 and 40 °C/min heating rates respectively. Reasonable fits of data to straight lines in kinetic study plot indicate that the assumption of first-order kinetics for thermal degradation of waste HDPE is acceptable.
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Thesis (Ph.D)- National Institute of Technology, Rourkela

The present work involves the experimental studies for the production of liquid fuel by
thermal and catalytic pyrolysis of waste high-density polyethylene in a laboratory batch
reactor.
Thermal pyrolysis of virgin HDPE was performed at a temperature range from 400 °C to
550 °C and heating rate of 20 °C/min. The liquid yield is highest 50 wt. % at temperature
450 ºC. Reaction time decreases with increase in temperature. Maximum oil yield in
thermal pyrolysis of waste HDPE was 50.8 wt. % at optimum condition of temperature,
which is improved to 58.8 wt. %, in kaolin catalyzed degradation under optimum
condition of temperature and feed ratio. The rate of reaction, oil yield and quality of oil
obtained in the catalytic pyrolysis are significantly improved as compared to thermal
pyrolysis.
The catalytic activity of kaolin is further enhanced by treating it with four different acids
and one base (acetic acid, phosphoric acid, nitric acid, hydrochloric acid and sodium
hydroxide). Acid treatment increased the surface area, acidity and also alters the pore
volume distribution of kaolin, which support the cracking reaction. The maximum yield
of oil in the acid treated kaolin catalyzed pyrolysis of waste HDPE was 79% under
optimum conditions. The composition of the oil was analyzed by FTIR and GC-MS. The
oil obtained from the catalytic pyrolysis of waste HDPE mostly contains aliphatic
hydrocarbons. The fuel properties of the oil obtained from the catalytic pyrolysis of waste
HDPE is similar with that of petro-fuels. So they can directly be used as an engine fuel
after fractionation or as a feedstock to petroleum refineries.
Response surface methodology (RSM) was used to optimize the catalytic pyrolysis
process of waste high-density polyethylene to liquid fuel over modified catalyst. The
reaction temperature, acidity of the modified catalysts and mass ratio between modified
catalysts to waste high-density polyethylene (HDPE) were chosen as independent
variables. Optimum operating conditions of reaction temperature (450 °C), acidity of
catalyst (0.341) and catalyst to waste HDPE ratio (1:4) were produced with respect to
Abstract
x
maximum liquid product yield of 78.7 %. The polynomial model obtained fits well to
predict the response with a high determination coefficient of R2
(0.995).
The diesel blended plastic oil obtained by the catalytic pyrolysis of waste HDPE has been
tested for its performance and emission in a CI diesel engine. Engine was able to run with
maximum 40% waste plastic oil- diesel blends. The engine vibrates at and above this
blend. Brake thermal efficiency of the waste HDPE oil blend is lower to diesel at all
loads. This may be due to lower calorific value of Waste HDPE Oil-diesel blend than
diesel. The BSEC increases with the increasing WPO blend ratio at all engine loads and
decreases with increase in engine load. Mechanical efficiency increases with increasing
brake power for all fuel blends. The NOx emission increases with increase in percentage
of waste plastic oil in blends and decreases with increase in engine load. The unburnt
hydrocarbon emission is decreasing with increase in the engine load and increases with
increase in percentage of waste plastic oil in blends. The CO emission increases with the
increasing WPO blend ratio and engine load. The carbon dioxide emission for the blends
is lower than diesel for almost all loads and all blends.
The thermo gravimetric analysis of waste HDPE at 10 ºC/min, 20 ºC/min and 40 ºC/min
in the N2 atmosphere was studied and kinetic parameter (activation energy) was
determined by using thermogravimetric curves. When the heating rate increases, the
activation energy and degradation temperature of the waste HDPE also increases. The
activation energy values of waste HDPE have been calculated as 207.43, 268.22 and
473.05 kJ/mol at 10, 20 and 40 °C/min heating rates respectively. Reasonable fits of data
to straight lines in kinetic study plot indicate that the assumption of first-order kinetics for
thermal degradation of waste HDPE is acceptable.

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