Decomposition of waste plastics

Abstract

Far infrared ray heating technology is used to breakdown waste plastic and resultant heavy oils into usable products. Waste plastics may thus be processed into petroleum products and used to generate energy.

1 . A process for converting waste plastic into oil, comprising subjecting waste plastic to a plurality of far infrared radiation sources in intimate contact with said plastic in a reactor which contains an agitator which distributes the waste plastic past the radiation sources. 
     
     
         2 . The process according to  claim 1 , wherein the far infrared sources comprise an electrical resistance heating element, a heat-absorbing material, a protective shell and thereon a far infrared radiation generating coating. 
     
     
         3 . The process according to  claim 2 , wherein the protective shell forms a rod over the heating element and heat-absorbing material. 
     
     
         4 . The process according to  claim 3 , wherein the rod is bullet-shaped. 
     
     
         5 . The process according to  claim 1 , wherein the far infrared radiation sources are disposed about the reactor such that the radiation generated from each source intersects with that of another source. 
     
     
         6 . The process according to  claim 1 , wherein the plastic is polypropylene, polyethylene, polyethylene terephthalate, polystyrene or a mixture thereof. 
     
     
         7 . The process according to  claim 6 , wherein the plastic contains polyvinylchloride in an amount of up to 2% by weight. 
     
     
         8 . A process according to  claim 1 , wherein the plastic is crushed and melted in a screw extruder prior to introduction to the reactor, and decomposition of the plastic takes place in the liquid phase. 
     
     
         9 . The process according to  claim 1 , wherein the far infrared radiation has a frequency which is selected to maximize absorption by the plastic. 
     
     
         10 . The process according to  claim 1 , wherein melted plastic undergoes pyrrolysis to produce a gas-oil mixture. 
     
     
         11 . The process according to  claim 10 , wherein pyrrolysis produces coke, which is removed from the reactor, and wherein the gas-oil mixture is subjected to further processing to recover gas, a light oil and a heavy oil. 
     
     
         12 . A process according to  claim 1 , comprising:
 a) subjecting the plastic material to thermal decomposition and pyrrolysis in liquid form in a reactor vessel (R- 1 );   b) fractionating resultant decomposition product so as to obtain gas, light oil and crude diesel oil;   c) continuously draining out sludge produced during pyrolysis and re-cracking the sludge to obtain byproduct of carbon residual,   d) subjecting the crude diesel oil to desulphurization treatment and consecutive solvent-extraction treatment to obtain diesel oil.   
     
     
         13 . The process according to  claim 12 , wherein a first fractionation tower is mounted directly on top of the reactor vessel. 
     
     
         14 . The process according to  claim 12 , wherein in (d), the sludge in the bottom of reactor vessel R- 1  is dried by a cylinder screw dryer with jacketed heater, and the sludge is discharged continuously into the dryer from an inlet near an end of the heater containing a motor driving the screw, and pushed to an outlet close to an opposite end, the middle of the dryer is heated to 600-700° C. by the jacketed heater, heavy oil components in the sludge are decomposed into low-weight gases and conveyed back to the reactor vessel or cooled and collected, the dried sludge is crushed into powder vessel at the outlet of the dryer and collected as carbon residual. 
     
     
         15 . The process according to  claim 12 , wherein the diesel oil is subjected to desulfurization. 
     
     
         16 . The process according to  claim 15 , wherein desulfurization is performed by subjecting the diesel oil to ultrasound energy, in the presence of an oxidizing solution. 
     
     
         17 . The process according to  claim 15 , wherein (e), the diesel oil is separated and further subjected to solvent extraction. 
     
     
         18 . A reactor for the pyrrolysis of waste plastic, comprising a reactor vessel having a feeding inlet ( 16 ) admitting plastic to a reactor chamber, a plurality of far infrared heating rods ( 15 ) and ( 17 ) disposed about the reactor chamber able to achieve intimate contact with said waste plastic, an agitator ( 13 ) which distributes the plastic past the rods, a sludge outlet ( 20 ) and a gas outlet ( 12 ). 
     
     
         19 . The reactor according to  claim 18 , further comprising two agitators that are separately drawn by their own motor reducer ( 28 ) and ( 29 ), a first agitator being a column form impeller ( 25 ), and a second agitator being a gate paddle impeller ( 26 ), and between the two agitators are installed infrared heating rods fixed on a bottom head of the reactor. 
     
     
         20 . The reactor according to  claim 18 , further comprising a fractionation tower (FT- 1 ) connected to gas outlet ( 12 ) said fractionation tower comprising an umbrella-shaped cap and an upside-down cone, a packing bed capable of exchanging heat and mass with top reflux in the fractionation tower, a second fractionation tower (FT- 2 ) having a bottom inlet in communication with the top of (FT- 1 ), and an outlet leading to heat exchanger (HE- 1 ), said heat exchanger capable of passing product of the second fractionation tower to a gas/oil separator (GOS- 1 ) capable of separating gas/oil into low pressure gas and liquid light oil, said separator (GOS- 1 ) having a recycle via a pump (P- 10 ) to FT- 2  as top reflux, and an outlet for sweet gas from the top of GOS- 1 , optionally to a gas storage tank (GST- 1 ), an outlet to a stripping tower (STT- 1 ) capable of producing crude diesel oil, said stripping tower connected to a desulphurization and solvent-extraction unit.