Pitch Composition Handling via Second Vacuum Column Separation
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Solution Overview
Problem
The processing of pitch produced from slurry hydrocracking (SHC) is challenging due to its sticky nature and difficulty in handling, as it can become brittle or sticky at different temperatures, making it impractical for bulk transportation and storage, and existing methods are inefficient for assessing its manageability.
Innovation Solution
A second vacuum column is introduced in the recovery process to separate vacuum gas oil (VGO) from pitch, allowing for lower temperatures and reducing coking concerns, resulting in pitch that can be formed into free-flowing solid particles, which are easier to manage during transportation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pitch is produced from slurry hydrocracking, then heavy hydrocarbons are converted to lighter fractions, but the pitch becomes sticky and difficult to handle at transportation temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of pitch by controlling the hydrocracking process to limit aromatic content to 10-30 wt% and saturates to 70-85 wt%. This parameter change modifies the physical properties of pitch, specifically raising its softening point above 100°C, which eliminates the stickiness problem and improves handling ease while maintaining conversion productivity
Solution Approach 2:
The patent utilizes phase transition concepts by ensuring pitch remains in a solid or semi-solid state at transportation temperatures through compositional control. The pitch transitions from a sticky, temperature-sensitive material to a stable solid form with defined softening point, enabling bulk handling without phase change complications
2Ease of operation
If pitch is heated for processing, then it becomes more fluid for handling, but it undergoes coking and degradation
Solution Approach 1:
The patent changes the chemical composition parameters of pitch by controlling the hydrocracking process to limit aromatic content to 10-30 wt% and saturates to 70-85 wt%. This parameter change modifies the physical properties of pitch, specifically raising its softening point above 100°C, which eliminates the stickiness problem and improves handling ease while maintaining conversion productivity
Solution Approach 2:
The patent converts the potential harm of coking into a benefit by producing a pitch composition that is inherently more stable. The controlled composition with limited aromatics and high saturates content prevents coking reactions, allowing pitch to be heated and processed without degradation, thus turning a previously harmful tendency into a stable,processable material
3Quantity of substance
If conventional vacuum distillation is used to separate VGO from pitch, then separation is achieved, but high temperatures cause coking and cracking
Solution Approach 1:
The patent changes the operating parameters of vacuum distillation by reducing the temperature to below 200°C. This parameter change, combined with the modified pitch composition (10-30 wt% aromatics, 70-85 wt% saturates), enables effective separation of VGO from pitch without causing coking or cracking reactions that occur at conventional higher temperatures
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 use of a second vacuum column produces pitch with a higher onset of softening point, making it non-sticky at anticipated transportation temperatures, thus facilitating easier handling and storage, and reduces coking risks in heating apparatuses.
Implementation Method 1
A second vacuum column is introduced in the recovery process to separate vacuum gas oil (VGO) from pitch
Implementation Method 2
SHC produces a pitch byproduct... Pitch is the hydrocarbon material boiling above 538° C. (1000° F.)... Pitch byproduct may then be formed into solid particles
Data Source
AI summary
A process and apparatus is disclosed for converting heavy hydrocarbon feed into lighter hydrocarbon products. The heavy hydrocarbon feed is slurried with a particulate solid material to form a heavy hydrocarbon slurry and hydrocracked in a slurry hydrocracking unit to produce vacuum gas oil (VGO) and pitch. A first vacuum column separates VGO from pitch, and a second vacuum column further separates VGO from pitch. As much as 15 wt-% of VGO can be recovered by the second vacuum column and recycled to the slurry hydrocracking unit. A pitch composition is obtained which can be made into particles and transported without sticking together.