Method and plant for converting plastic into oil

Abstract

A method and plant for conversion into oil is provided which can completely heat and decompose a large amount of a plastic raw material, and treat a harmful gas. The plastic raw material is dissolved in a dissolution section ( 31 ) to form an expanded plastic. The expanded plastic is sent to an inclined first-stage decomposition column ( 47 ) and a second-stage decomposition column ( 48 ) adjacent to the first-stage decomposition column, both having fixed temperature distributions, which depolymerize and decompose the plastic into a light secondarily decomposed gas. The extracted secondarily decomposed gas is cooled into oil in condensers ( 37, 38 ) and collected in oil storage tanks ( 42, 43 ).

1 . A method for converting plastic into oil, comprising: 
 a dissolution step of heating and dissolving the plastic into expanded plastic; and    a decomposition step of removing the expanded plastic, heating and depolymerizing the expanded plastic, and cooling the expanded plastic into oil.    
     
     
         2 . The method for converting plastic into oil according to  claim 1 , 
 wherein, in the decomposition step, the expanded plastic is removed by being lifted at an angle.    
     
     
         3 . The method for converting plastic into oil according to  claim 1 , 
 wherein, in the decomposition step, the expanded plastic is removed by being lifted at an angle of 25-30° relative to the horizontal.    
     
     
         4 . The method for converting plastic into oil according to  claim 2 , 
 wherein, in the decomposition step, the expanded plastic is heated with being lifted at an angle and the expanded plastic is heated to higher temperatures at higher positions.    
     
     
         5 . The method for converting plastic into oil according to  claim 1 , 
 wherein, in the dissolution step, the plastic is dissolved in a dissolution section including a plurality of dissolution columns with different temperature ranges.    
     
     
         6 . The method for converting plastic into oil according to  claim 1 , 
 wherein, in the dissolution step, the dissolved plastic is added with vegetable oil or animal oil or mineral oil to generate expanded plastic of a mixture of the plastic and the vegetable oil or animal oil or mineral oil, and    in the decomposition step, the expanded plastic is removed, heated and depolymerized, and cooled into oil.    
     
     
         7 . The method for converting plastic into oil according to  claim 1 , 
 wherein, in the decomposition step, the expanded plastic is removed and heated in a decomposition section including a plurality of decomposition columns with different temperature ranges.    
     
     
         8 . The method for converting plastic into oil according to  claim 1 , further comprising 
 a hydrogen chloride gas treatment step of separating a hydrogen chloride gas generated in dissolving the plastic in the dissolution step from other decomposed gases, then reacting the hydrogen chloride gas with hydrated lime, and collecting the hydrogen chloride gas as calcium chloride.    
     
     
         9 . The method for converting plastic into oil according to  claim 1 , further comprising 
 a off gas treatment step of treating an off gas not converted into oil in the decomposition step by catalytically cracking the off gas with a hot ceramic.    
     
     
         10 . A plant for conversion into oil, comprising: 
 a dissolution section for heating and dissolving the plastic into expanded plastic; and    a decomposition section for removing the expanded plastic, heating and depolymerizing the expanded plastic, and cooling the expanded plastic into oil.    
     
     
         11 . The plant for conversion into oil according to  claim 10 , wherein the decomposition section comprises removal means for removing the expanded plastic by lifting the expanded plastic at an angle.  
     
     
         12 . The plant for conversion into oil according to  claim 10 , wherein the decomposition section comprises removal means for removing the expanded plastic by lifting the expanded plastic at an angle of 25-30° relative to the horizontal.  
     
     
         13 . The plant for conversion into oil according to  claim 11 , 
 wherein the decomposition section comprises heating means for heating the expanded plastic with lifting the expanded plastic at an angle and for heating the expanded plastic to higher temperatures at higher positions.    
     
     
         14 . The plant for conversion into oil according to  claim 10 , wherein the dissolution section comprises a plurality of dissolution columns with different temperature ranges.  
     
     
         15 . The plant for conversion into oil according to  claim 10 , comprising 
 oil injection means for injecting vegetable oil or animal oil or mineral oil into a connection between the dissolution section and the decomposition section.    
     
     
         16 . The plant for conversion into oil according to  claim 10 , wherein the decomposition section comprises a plurality of tilted decomposition columns with different temperature ranges.  
     
     
         17 . The plant for conversion into oil according to  claim 10 , further comprising 
 a dechlorination system for treating a hydrogen chloride gas generated in the dissolution section,    wherein the dechlorination system comprises a separator for separating the hydrogen chloride gas from other decomposed gases, and a reactor for reacting the hydrogen chloride gas separated by the separator with hydrated lime into calcium chloride.    
     
     
         18 . The plant for conversion into oil according to  claim 10 , further comprising 
 an off gas treatment system for treating an off gas not converted into oil after cooling in the decomposition section by catalytically cracking the off gas with a hot ceramic.    
     
     
         19 . The plant for conversion into oil according to  claim 16 , wherein each of multistage decomposition columns depolymerizes the plastic into a decomposed gas which is cooled into oil.  
     
     
         20 . The plant for conversion into oil according to  claim 16 , wherein at least part of the decomposition column comprises a superheat for further depolymerizing the depolymerized plastic.  
     
     
         21 . The plant for conversion into oil according to  claim 16 , wherein the decomposition column is heated with increasing temperatures from bottom to top.  
     
     
         22 . The plant for conversion into oil according to  claim 16 , comprising 
 residual collection means at a top of a final stage decomposition column of the multistage decomposition columns.    
     
     
         23 . The plant for conversion into oil according to  claim 22 , wherein the residual collection means comprises a column with its upper opening at the top of the final stage decomposition column and its lower opening in an atmosphere of an inactive gas heavier than an air.  
     
     
         24 . The plant for conversion into oil according to  claim 10 , further comprising a hopper for storing and supplying the plastic into the dissolution section, 
 wherein the hopper comprises a lead screw with a spiral blade.    
     
     
         25 . The plant for conversion into oil according to  claim 24 , further comprising an unheated section formed as an unheated area of a predetermined length between the hopper and the dissolution section.  
     
     
         26 . The plant for conversion into oil according to  claim 14 , wherein the plurality of dissolution columns each comprise a lead screw with a spiral blade for carrying the plastic, 
 a beginning dissolution column of the plurality of dissolution columns comprises the lead screw blade with a greater pitch than the lead screws blades in other dissolution columns.    
     
     
         27 . The plant for conversion into oil according to  claim 14 , 
 wherein the dissolution section and the decomposition section each comprise: an inner column; an outer column around the inner column; a hot air space between the inner column and the outer column and through which an hot air circulates; and a temperature sensor for detecting a temperature in the dissolution section or the decomposition section, and    wherein the plant further comprises a carbon dioxide gas supplying system for supplying the carbon dioxide gas into the hot air space if the temperature sensor detects an abnormal temperature equal to or greater than a predetermined temperature.    
     
     
         28 . The plant for conversion into oil according to  claim 14 , 
 wherein the dissolution section and the decomposition section each comprise: an inner column; an outer column around the inner column; and a hot air space between the inner column and the outer column and through which an hot air circulates,    wherein the plant further comprises: a hot air production system for generating by combustion the hot air to be supplied into the hot air space; and a drying system for drying the plastic to be supplied into the dissolution section, and    wherein an air in the drying system is supplied into the hot air production system to be deodorized by combustion.    
     
     
         29 . The plant for conversion into oil according to  claim 18 , further comprising 
 a drying system for drying the plastic to be supplied into the dissolution section,    wherein an air in the drying system is supplied into the off gas treatment system to be deodorized by being catalytically cracked with a hot ceramic.    
     
     
         30 . The plant for conversion into oil according to  claim 14 , 
 wherein an extendable column which is extendably formed is used in a part of the dissolution column includes, and    wherein the extendable column comprises: an inner column; a bellows around the inner column which has one end fixed on the inner column and an other end slidable relative to the inner column; and an outer column which is fixed on the other end of the bellows and slidably contains the inner column.    
     
     
         31 . The plant for conversion into oil according to  claim 10 , 
 wherein the dissolution section comprises: an inner column; an outer column around the inner column; and a heating medium space between the inner column and the outer column and through which a liquid heating medium circulates, and    wherein the plant further comprises a heating medium supplying system for supplying the liquid heating medium into the heating medium space.