Integral Vapor-Liquid Separation in Steam Cracking Convection Sections
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Solution Overview
Problem
Conventional steam cracking processes face inefficiencies due to the need for operating at atmospheric pressures, which can be uneconomical, and the use of catalysts instead of steam to lower activation energy, leading to suboptimal product yields.
Innovation Solution
Integration of a vapor-liquid separation device within the steam pyrolysis cracking unit, allowing for efficient separation of vapor and liquid phases, which can be recycled or processed further, enhancing the steam cracking process by optimizing reaction conditions and product formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam pyrolysis cracking is performed at or above atmospheric pressure without effective vapor-liquid separation, then the process can operate at economically viable pressures, but the reaction conditions become suboptimal and yield of desirable hydrocarbons decreases
Solution Approach 1:
The patent combines the vapor-liquid separation function directly into the convection section by integrating a liquid outlet at the lowest point of the convection section furnace tube. This merging of separation functionality into the existing heating structure eliminates the need for separate external separation equipment, thereby improving hydrocarbon yield through effective separation while avoiding increased device complexity
Solution Approach 2:
The patent introduces steam as an intermediary substance that facilitates both the cracking reaction and the vapor-liquid separation process. Steam serves as a heat transfer medium in the convection section and also helps maintain the vapor phase while allowing liquid products to separate and drain, thus improving productivity without requiring complex separation machinery
2Loss of energy
If conventional steam cracking process operates without integrated vapor-liquid separation, then the process structure remains simple, but energy consumption increases and intermediate products cannot be efficiently recycled
Solution Approach 1:
The patent implements a feedback mechanism where liquid effluent separated in the convection section is recycled back to the feed stream. The liquid outlet at the bottom of the convection section furnace tube captures intermediate liquid products, which are then fed back into the cracking process, creating a closed-loop system that reduces energy loss by reprocessing intermediates rather than discarding them
Solution Approach 2:
The patent performs preliminary vapor-liquid separation within the convection section before the effluent enters the pyrolysis section. By separating and recycling liquid intermediates at this early stage, the system prevents energy waste that would occur if these intermediates were processed again in subsequent sections, thereby reducing overall energy consumption without adding complex post-processing equipment
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
The vapor-liquid separation device improves the steam cracking process by enabling more favorable reaction conditions, increasing desired product yields without the need for additional power or chemical supplies, and maintaining a maintenance-free operation.
Implementation Method 1
the convection section effluent is separated in a vapor- liquid separator
Implementation Method 2
The convection section of the steam pyrolysis cracking zone is used to heat the feed to the required reaction temperatures
Implementation Method 3
the pyrolysis cracking reaction occurs. Steam pyrolysis cracking reactions typically convert a relatively heavy hydrocarbon feedstock into lighter, and more desirable, hydrocarbons
Data Source
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AI summary
An integrated vapor-liquid separation device is provided in conjunction with a steam pyrolysis cracking unit operation. In certain aspects, a feed is charged to the inlet of a convection portion of a steam pyrolysis unit where the feed is heated to conditions effective for steam cracking. The convection section effluent is separated in a vapor-liquid separator and the separator vapor effluent is charged to the inlet steam cracking portion of the steam pyrolysis zone. The liquid effluent can be further processed, recycled within the system or a combination thereof. In additional aspects, a feed separated upstream of the convection portion of a steam pyrolysis unit using a flash vessel equipped with a vapor-liquid separator device described herein.