Tail Gas Unsaturated Hydrocarbon Separation for Syngas Production
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Solution Overview
Problem
The existing hydrocarbon production processes face challenges in achieving high preheating temperatures for partial oxidation or autothermal reforming due to unsaturated hydrocarbons leading to soot deposits, which requires excessive oxygen use, impairing economic viability.
Innovation Solution
Separating unsaturated hydrocarbons from the tail gas using cryogenic methods to create a stream free of unsaturated hydrocarbons, allowing for higher preheating temperatures and reduced oxygen usage, and utilizing this stream in partial oxidation or autothermal reforming, while recycling saturated hydrocarbons for Fischer-Tropsch synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If unsaturated hydrocarbons are present in the tail gas and preheated, then the preheating temperature is limited, but higher preheating temperatures are needed for efficient partial oxidation or autothermal reforming
Solution Approach 1:
The invention extracts and removes unsaturated hydrocarbons from the tail gas stream through a separation unit positioned between the Fischer-Tropsch synthesis and the preheating stage. This removal eliminates the source of soot formation while allowing the remaining saturated hydrocarbons to be preheated to the high temperatures required for efficient partial oxidation or autothermal reforming.
2Ease of manufacture
If the preheating temperature is limited to prevent soot deposits, then soot formation is avoided, but excessive oxygen must be supplied to achieve conversion temperatures, impairing economic viability
Solution Approach 1:
The invention performs preliminary removal of unsaturated hydrocarbons from the tail gas before the preheating stage. This preliminary action prevents the formation of soot deposits that would otherwise require excessive oxygen supply for complete combustion, thereby reducing oxygen consumption and improving economic viability while still achieving the necessary conversion temperatures.
3Productivity
If tail gas is recycled to PDX or ATR, then process efficiency is improved, but unsaturated hydrocarbons in the recycled stream cause soot deposits
Solution Approach 1:
The invention converts the harmful effect of unsaturated hydrocarbons by separating and removing them from the recycled tail gas stream. This allows the beneficial recycling of tail gas to proceed without the harmful soot formation, as the unsaturated components are extracted before the preheating and reaction stages.
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
Enables preheating up to 450°C in PDX and 600°C in ATR reactors with lower oxygen consumption, enhancing process efficiency and economic viability by preventing soot deposits and optimizing hydrogen to carbon monoxide ratios in synthesis gas.
Implementation Method 1
For removal of the unsaturated hydrocarbons, cryogenic separation methods are appropriately employed
Implementation Method 2
The first feed substream, after preheating with cooling process streams
Implementation Method 3
the first feed substream is converted by means of partial oxidation or autothermal reforming to a first synthesis gas stream
Implementation Method 4
reacted in an exothermic process with oxygen which is supplied to the reactor
Implementation Method 5
the second feed substream is converted by means of steam reforming to a second synthesis gas stream
Implementation Method 6
at least a first portion is converted by Fischer-Tropsch synthesis to a crude product stream comprising hydrocarbons of different chain lengths
Implementation Method 7
the tail gas is separated from the crude product stream in a cold trap
Data Source
AI summary
A process for producing hydrocarbons is disclosed in which a first feed substream and a second feed substream are obtained from a hydrocarbonaceous feed stream, of which the first feed substream is converted by means of partial oxidation or autothermal reforming to a first synthesis gas stream and the second feed substream is converted by means of steam reforming to a second synthesis gas stream and subsequently combined with the first synthesis gas stream to give a third synthesis gas stream, of which at least a first portion is converted by Fischer-Tropsch synthesis to a crude product stream comprising hydrocarbons of different chain lengths, from which light hydrocarbons are separated in a tail gas, in order to recycle them and use them in the partial oxidation or autothermal reforming. The characteristic feature here is that unsaturated hydrocarbons are separated from at least a portion of the tail gas.