Deep Hydroconversion of Vacuum Residue for Asphalt Reduction
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Solution Overview
Problem
Current processes for converting heavy hydrocarbon feedstocks with high boiling points face limitations in achieving high conversion rates and reducing asphalt yields, due to constraints on sulfur content in bunker fuels and market demands for fuels distilled at low temperatures.
Innovation Solution
A process involving successive stages of deep hydroconversion, separation, and deasphalting, using catalysts with metals from Group VIII and VIb, and operating at specific pressure and temperature conditions to enhance conversion efficiency and reduce asphalt production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hydroconversion processes are used to convert heavy hydrocarbon feedstocks, then the process is relatively simple and economical, but the conversion rate is limited and asphalt yields are high
Solution Approach 1:
The hydroconversion process is divided into multiple sequential stages (first hydroconversion stage, second hydroconversion stage) with different operating conditions. The first stage operates at lower severity to protect the catalyst, while the second stage operates at higher severity to achieve deeper conversion and reduce asphalt formation, thereby resolving the contradiction between conversion rate and asphalt yields
Solution Approach 2:
The process employs parameter changes by operating at different space velocities in different stages (0.1-10 h⁻¹ in the first stage, 0.01-1 h⁻¹ in the second stage), and adjusting temperature and pressure conditions to optimize both conversion rate and minimize asphalt formation. This multi-parameter optimization resolves the technical contradiction
2Productivity
If high space velocities are used in hydroconversion stages, then productivity is improved, but the formation of asphalt increases and limits maximum overall conversion
Solution Approach 1:
The process segments the hydroconversion into two stages with different space velocity ranges. The first stage uses higher space velocities (0.1-10 h⁻¹) for initial conversion, while the second stage uses lower space velocities (0.01-1 h⁻¹) to minimize asphalt formation and achieve deeper conversion, thereby resolving the contradiction between productivity and asphalt formation
Solution Approach 2:
The first hydroconversion stage performs preliminary conversion at moderate conditions before the second stage operates at higher severity. This preliminary action protects the catalyst in the second stage from rapid deactivation and allows for more efficient conversion with less asphalt formation, resolving the contradiction between space velocity and asphalt 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
The process achieves higher conversion rates of naphtha, kerosene, and gas oil while reducing asphalt yields and improving operability, with a better return on investment and capital savings.
Implementation Method 1
with a catalyst containing at least one metal from Group VIII chosen from nickel and cobalt and at least one metal from Group VIb chosen from molybdenum and tungsten
Implementation Method 2
a first deep hydroconversion of said hydrocarbon feedstock is carried out in the presence of hydrogen
Implementation Method 3
deep hydroconversion of said hydrocarbon feedstock is carried out in the presence of hydrogen
Implementation Method 4
a deasphalting stage e), with a hydrocarbon solvent having from 3 to 7 carbon atoms
Data Source
AI summary
The invention concerns a method for converting heavy hydrocarbon feedstocks of which at least 50% by weight boils at a temperature of at least 300° C., and in particular vacuum residues. The feedstocks are subjected to a first step a) of deep hydroconversion, optionally followed by a step b) of separating a light fraction, and a heavy residual fraction is obtained from step b) of which at least 80% by weight has a boiling temperature of at least 250° C. Said fraction from step b) or the effluent from step a) is then subjected to a second step c) of deep hydroconversion. The overall hourly space velocity for steps a) to c) is less than 0.1 h−1. The effluent from step c) is fractionated to separate a light fraction. The heavy fraction obtained, of which 80% by weight boils at a temperature of at least 300° C., is sent to a deasphalting step e). The deasphalted fraction DAO is then preferably converted in a step f) chosen from ebullated bed hydroconversion, fluidised bed catalytic cracking and fixed bed hydrocracking.