Hydrocracking Steam Cracker Feedstock to Reduce Coke Deposition
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Solution Overview
Problem
Conventional hydrocarbon processing methods, such as steam cracking and hydrocracking, face inefficiencies in upgrading naphtha and heavy liquid feeds to produce valuable aromatics and olefins, leading to substantial production of low-value heavy by-products and high capital costs, as well as challenges in processing heavy crude oil cuts due to incomplete evaporation and coke deposition in steam cracker tubes.
Innovation Solution
A process involving multiple hydrocracking units with different conditions, separation, and extraction units to optimize the production of mono-aromatics and C2-C4 paraffins, where aromatics are recycled and further processed to enhance aromatics production efficiency, and paraffins are hydrocracked to LPG, with hydrogen and methane being reused to improve energy performance and hydrogen balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional steam cracking is used to process heavy crude oil cuts, then light olefins and aromatic compounds can be produced, but incomplete evaporation occurs and coke is rapidly deposited on tube surfaces reducing heat transfer and increasing pressure drop
Solution Approach 1:
The heavy crude oil cuts are preheated to a temperature of 350°C to 400°C in a preheating section before entering the cracking section. This preliminary heating ensures complete evaporation of the heavy feeds before they encounter the high temperatures that would cause coke deposition, thereby maintaining reliable operation of the steam cracker.
2Quantity of substance
If heavy crude oil cuts are processed in steam crackers, then more feedstock can be utilized, but substantial quantities of heavy by-products such as C9+ aromatics and condensed aromatics are formed
Solution Approach 1:
A hydrocracking unit is introduced as an intermediary process between crude oil distillation and steam cracking. This hydrocracking unit pre-processes the heavy crude oil cuts under controlled conditions to break down complex molecules before they enter the steam cracker, thereby reducing the formation of heavy by-products like C9+ aromatics and condensed aromatics while allowing greater feedstock flexibility.
3Productivity
If hydrocracking is used to upgrade steam cracker heavy by-products, then higher value chemicals can be produced, but capital costs are too high to justify the investment
Solution Approach 1:
The hydrocracking unit is merged with the existing steam cracker to form an integrated processing system. The hydrocracking unit processes a portion of the crude oil distillation cuts before they enter the steam cracker, and the combined system optimizes the overall yield of valuable products while sharing infrastructure and reducing duplicate capital investments.
Solution Approach 2:
The hydrocracking unit operates under specific parameter conditions (temperature of 300°C to 400°C, pressure of 30 to 200 atmospheres, and controlled residence time) that are optimized to maximize the production of steam cracker feedstock and minimize heavy by-product formation, thereby improving the economic viability of the integrated system.
4Productivity
If conventional hydrocracking conditions are used for heavy refinery streams, then conversion is achieved, but hydrogen consumption increases and light molecules such as methane are produced at the expense of more valuable species
Solution Approach 1:
The hydrocracking process uses dynamic control of operating parameters including temperature (300°C to 400°C), pressure (30 to 200 atmospheres), and residence time to optimize the conversion of heavy refinery streams. These dynamic parameters are adjusted to maximize the production of valuable aromatic hydrocarbons and C2-C4 paraffins while minimizing hydrogen consumption and unwanted methane formation.
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 increases the yield of high-value chemicals like ethylene and propylene, reduces heavy by-product formation, and allows for more efficient processing of heavy crude oil cuts, improving energy efficiency and hydrogen utilization while minimizing capital costs.
Implementation Method 1
hydro-cracking (whereby the hydro-cracker feed is exposed to a suitable catalyst under conditions which result in some fraction of the feed molecules being broken into shorter hydrocarbon molecules with the simultaneous addition of hydrogen)
Implementation Method 2
via distillation, into a number of cuts such as naphtha, gas oils and residua
Implementation Method 3
an extraction unit, wherein the aromatics fraction obtained is directly sent to the steam cracker separation section
Implementation Method 4
the hydrocarbon feed stream is evaporated and diluted with steam then exposed to a very high temperature (800°C to 860°C) in short residence time
Implementation Method 5
steam cracking in which the hydrocarbon feed stream is evaporated and diluted with steam then exposed to a very high temperature (800°C to 860°C) in short residence time
Implementation Method 6
hydrogen and methane being reused to improve energy performance and hydrogen balance
Data Source
Figure 1
AI summary
The present invention relates to process for cracking a hydrocarbon feedstock in a steam cracker unit, comprising the following steps of: feeding a hydrocarbon feedstock to a first hydrocracking unit, feeding the hydrocarbon feedstock thus cracked to a separation unit for obtaining a stream high in paraffins and naphtenes, a stream high in heavy aromatics and a stream high in mono-aromatics feeding the stream high in paraffins and naphtenes to a second hydrocracking unit, wherein the process conditions in the first hydrocracking unit differ from the process conditions in the second hydrocracking unit, separating the stream thus hydrocracked in the second hydrocracking unit in a high content aromatics stream and gaseous stream comprising C2-C4 paraffins, hydrogen and methane, feeding the gaseous stream to a steam cracker unit.