Co-Conversion of Waste Plastics in Delayed Coker Units
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Solution Overview
Problem
Existing processes for converting waste plastics in Delayed Coker units face challenges with non-uniform mixing and enhanced coke formation due to varying melting points and metal contents, leading to potential furnace tube choking and coking issues, especially when processing metal-additized plastics.
Innovation Solution
A thermal cracking process that involves feeding waste plastics in a molten form into the Delayed Coker drum, where they are co-converted with petroleum residues, using a unique hardware system that includes a main fractionator column, furnace, and gas concentration and separation section to produce lighter distillate products, while preventing incremental coke deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If waste plastics are mixed with petroleum residues and processed through furnace and coke drums, then waste plastics can be converted into lighter distillate products, but non-uniform mixing occurs and enhanced coke formation is caused due to varying melting points and metal contents
Solution Approach 1:
The waste plastics are pre-melted in a dedicated melt tank before being introduced to the delayed coker drum. This preliminary melting action ensures the plastics are in a uniform liquid state with consistent viscosity and temperature, eliminating mixing issues that would occur if solid plastics with varying melting points were introduced directly. The pre-melting also prevents metal components from causing enhanced coke formation by ensuring uniform distribution before thermal cracking.
2Adaptability or versatility
If waste plastics are dissolved in highly aromatic solvents like furfural, then waste plastics can be processed in Delayed Coker, but the process complexity increases and additional treatment units are required
Solution Approach 1:
The invention extracts the melting function from the main Delayed Coker process by introducing a separate melt tank. This allows the waste plastics to be melted and prepared independently before being fed into the coker drum, thereby simplifying the overall process scheme by eliminating the need for complex solvent dissolution systems while maintaining the ability to process waste plastics effectively.
3Productivity
If polymer is melted and mixed with feedstock, then waste plastics can be co-processed, but high viscosity and density difference cause variation in flow pattern leading to choking and coking problems
Solution Approach 1:
The invention controls the temperature of the melted waste plastics in the melt tank to maintain optimal viscosity for co-processing. By adjusting this parameter, the melted plastics achieve a viscosity and density compatible with the hydrocarbon feedstock, ensuring stable flow patterns through the furnace tubes without choking or excessive coking. This parameter control enables smooth integration of plastic melts with petroleum residues.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process effectively converts waste plastics into valuable lighter distillate products like fuel gas, LPG, naphtha, and Coker Fuel Oil, while ensuring no incremental coke deposition in the furnace, thus addressing environmental concerns and generating value from low-cost waste plastics.
Implementation Method 1
thermal cracking a mixture of the secondary feed and the waste plastic to obtain a combined product vapor inside the coke drum
Implementation Method 2
feeding the secondary hydrocarbon feed after heating in a furnace to a delayed coker drum
Implementation Method 3
routing the combined product vapor to a main fractionator column to obtain a light coker gasoil, a heavy coker gasoil and a coke fuel oil along with a vapor fraction
Implementation Method 4
sending the vapor fraction to a gas concentration (GASCON section) and separation section for separating into fuel gas, LPG and naphtha
Data Source
AI summary
The present invention relates to a process for converting the waste plastic along with the petroleum residue feedstock in a Delayed Coker unit employed in refineries. The invented process aims to convert any type of waste plastic including polystyrene, polypropylene, polyethylene etc. including metal additized multilayer plastics along with the petroleum residue material from crude oil refining such as reduced crude oil, vacuum residue etc. Value added light distillate products like motor spirit, LPG, middle distillates etc. are produced upon co-conversion in the invented process and is recovered and treated along with the products of thermal cracking of hydrocarbon residues. The residual metals in the metal additized plastics upon co-conversion in the invented process will be deposited in the solid petroleum coke.