Plastic Feedstock Dechlorination for Refinery Co-Processing
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Solution Overview
Problem
The incorporation of plastic waste into conventional refinery processes poses challenges due to the presence of chlorine-containing polymers, which can cause corrosion of equipment and require additional reactor vessels for chloride removal, increasing capital investment and operational costs.
Innovation Solution
A method involving mixing plastic feedstock with additional feedstocks at a dechlorination temperature of 170° C. to 250° C. and passing a purge gas to remove HCl, minimizing the need for separate reactor vessels and reducing the formation of volatile organic compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a downstream hydroprocessing stage is added for chloride removal, then chloride content in products is reduced, but capital investment and operational costs increase
Solution Approach 1:
The patent performs dechlorination as a preliminary step before co-processing in the main reactor. By removing chlorine from plastic waste beforehand through controlled thermal decomposition at 250-450°C with nitrogen purge, the harmful chlorides are eliminated prior to entering the main processing system, avoiding the need for downstream hydroprocessing stages and their associated high capital and operational costs
Solution Approach 2:
The patent extracts and removes the harmful chloride component from the plastic waste feedstock through a separate dechlorination step. The chlorine is decomposed and purged from the system as HCl gas, separating the harmful element from the plastic material before it enters the main co-processing reactor, thereby protecting downstream equipment without requiring complex hydroprocessing infrastructure
2Object-affected harmful factors
If separate reactor vessels are used for chloride removal, then equipment corrosion is minimized, but the number of reactor vessels increases
Solution Approach 1:
The patent combines the dechlorination function with the main co-processing operation by using a single reactor vessel that can handle both functions. The plastic waste is fed into the reactor where dechlorination occurs first, followed by co-processing of the dechlorinated material with petroleum feedstocks, eliminating the need for separate reactor vessels while still protecting equipment from corrosion
Solution Approach 2:
The dechlorination process is performed as a preliminary step within the same reactor vessel before the main co-processing reaction. By removing chlorides in advance within the same equipment, the reactor is protected from corrosion during subsequent processing operations, avoiding the need for separate corrosion-protection vessels
3Reliability
If elevated temperatures and hydrogen treat gas are provided for hydroprocessing, then chloride removal effectiveness is improved, but energy consumption increases
Solution Approach 1:
The patent uses nitrogen gas as a disposable purge medium instead of expensive hydrogen treat gas. The nitrogen flows through the dechlorination zone, carrying away HCl as it forms, and is then vented or recycled. This approach achieves effective chloride removal without the high energy consumption and cost associated with maintaining hydrogen atmosphere and elevated temperatures required for hydroprocessing
Solution Approach 2:
The patent replaces the chemical hydroprocessing mechanism (requiring hydrogen and high energy input) with a thermal decomposition and gas purge mechanism. By using controlled heating with nitrogen flow to carry away decomposition products, the system achieves chloride removal with significantly lower energy consumption than conventional hydroprocessing
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 approach effectively reduces chloride content in plastic waste prior to co-processing, minimizing corrosion risks and equipment exposure, while simplifying the processing system and reducing the formation of undesirable carbon-containing products.
Implementation Method 1
maintaining the feedstock mixture in a vessel at the dechlorination temperature to form a dechlorinated mixture of feedstocks
Implementation Method 2
passing a purge stream comprising a purge gas through the vessel to form a purge exhaust stream containing at least a portion of the purge gas
Data Source
AI summary
Systems and methods are provided for reducing or minimizing the chloride content of products generated during co-processing of a plastic feedstock (such as plastic waste) in a refinery process. The reduction in chloride is achieved by mixing the plastic feedstock with one or more additional feedstocks for co-processing in a mixing and/or holding vessel that is maintained at a dechlorination temperature that allows for decomposition of chlorine from the plastic feedstock to form HCl, while reducing or minimizing other conversion of the plastic feedstock and/or the additional feedstock. A purge gas can be passed through the mixing/holding vessel to remove the evolved HCl from the vessel. Because the dechlorination temperature is selected to reduce or minimize conversion of the feedstocks in the mixture, the amount of carbon-containing products that are removed with the purge gas can be reduced or minimized. The dechlorinated mixture of plastic feedstock and additional feedstock(s) can then be processed in a convenient refinery process, such as a thermal cracking process (e.g., coking, visbreaking, other types of pyrolysis) or a catalytic conversion process (e.g., fluid catalytic cracking).