Polyalkylate Distillation Column Pressure Gradient Optimization
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Solution Overview
Problem
Current polyalkylate columns in cumene production suffer from significant yield losses of triisopropylbenzene (TIPB) in the heavies stream due to operating conditions and catalyst systems, which are not economically viable for recovering TIPB, despite newer catalysts producing increased TIPB amounts.
Innovation Solution
A process involving a distillation column operating at a top pressure of less than 35 kPa and a bottoms pressure of less than 21 kPa above the top pressure, with a bottoms temperature ranging from 224° to 241°C, to efficiently separate diisopropylbenzene (DIPB) and TIPB, achieving a side draw comprising at least 99.8 wt% of DIPB and 50 wt% of TIPB, and a bottoms stream with at least 95 wt% of heavies, utilizing a condenser to recycle hydrocarbon vapor and liquid for improved separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If high-pressure steam is used to reboil the bottom of the polyalkylate column, then the reboiling is economically efficient, but significant TIPB yield losses occur in the heavies stream
Solution Approach 1:
The patent changes the operating parameters of the polyalkylate column, specifically reducing the pressure gradient between bottom and top (from typical 40-50 kPa to less than 21 kPa) and lowering the bottom temperature (to 224-241°C). This parameter change allows efficient separation of TIPB from heavies while minimizing TIPB losses in the bottoms stream, resolving the contradiction between energy-efficient reboiling and TIPB yield preservation
Solution Approach 2:
The patent introduces dynamic control of the column operation by implementing a specific pressure gradient control strategy and temperature profile optimization. The system dynamically adjusts operating conditions to maintain the bottom temperature in the 224-241°C range while keeping the pressure differential below 21 kPa, enabling adaptive optimization of both energy efficiency and TIPB recovery
2Productivity
If conventional polyalkylate columns are designed to recover DIPB, then DIPB recovery is optimized, but TIPB recovery is not economically viable
Solution Approach 1:
The patent modifies the polyalkylate column design and operation to perform multiple functions: it maintains effective DIPB recovery while adding the capability to recover TIPB economically. By optimizing the pressure gradient and temperature profile, the column becomes versatile enough to handle both separation requirements simultaneously, making TIPB recovery economically viable for the first time
Solution Approach 2:
The patent applies parameter changes to the column operation conditions, specifically reducing the bottom temperature to 224-241°C and limiting the pressure gradient to less than 21 kPa. These parameter changes transform the column's separation characteristics, enabling it to recover TIPB effectively while maintaining DIPB recovery, thus achieving multi-functionality
3Manufacturing precision
If the pressure gradient in the polyalkylate column is reduced to less than 21 kPa, then TIPB separation from heavies is improved, but the column design must be modified
Solution Approach 1:
The patent achieves improved TIPB separation precision by changing the operating parameters of the existing column design, specifically reducing the pressure gradient to less than 21 kPa and controlling the bottom temperature to 224-241°C. Rather than requiring fundamental design modifications, the solution utilizes parameter optimization of the conventional column, minimizing device complexity while achieving the desired separation precision
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 process significantly increases the recovery of both DIPB and TIPB, thereby enhancing cumene yield through transalkylation techniques, with the potential to make TIPB recovery economically viable, leading to increased cumene production and reduced operational costs.
Implementation Method 1
introducing the feed into a distillation column operating at a column top pressure of less than 35 kPa (5 psia), a column bottoms pressure of less than 21 kPa (3 psi) above the column top pressure and a bottoms temperature ranging from 224° to 241°C (435° to 465°F)
Implementation Method 2
utilizing a condenser to recycle hydrocarbon vapor and liquid for improved separation
Data Source
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AI summary
Processes and apparatuses for separating diisopropylbenzene (DIPB) and triisopropylbenzene (TIPB) from a feed (21) comprising DIPB, TIBP, and polyalkylate heavies are disclosed. The disclosed processes include introducing the feed (21) into a distillation column (22) having a column top (24) pressure of less than 35 kPa (5 psia), a column bottoms (25) pressure of less than 21 kPa (3 psi), and preferably 14 kPa (2 psi) or less above the column top pressure with a bottoms temperature ranging from 224 to 241 C (435° to 465°F). The processes also include taking off a side draw (28) comprising at least 99.8 wt% of the DIPB and at least 50 wt% of the TIPB present in the feed (21) and a bottoms stream (41) comprising at least 95 wt% of the heavies contained in the distillation feed (21). The low temperature bottoms temperature enables high pressure steam to be used as the bottoms reboiler (38) heat source.