Alkylation Product Separation via Dual-Pressure Fractionation
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Solution Overview
Problem
The high energy consumption in the separation process of alkylation products is primarily due to the inefficient recovery and utilization of low-carbon hydrocarbons' condensation heat, leading to significant energy expenditure in alkylation processes, particularly in the fractionating columns.
Innovation Solution
A process utilizing a high-pressure flash evaporation method to increase the potential temperature of the recycled stream, which is then heat-exchanged with the alkylation product, combined with a high-pressure fractionating column followed by a low-pressure fractionating column, to concentrate the alkylation oil and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high external alkane/alkene ratio is used in the alkylation reaction to suppress side reactions and increase reactant concentration, then the selectivity and reaction efficiency are improved, but the proportion of alkylation oil in the reactor outlet stream becomes very low (10%-30% for liquid acid, less than 10% for solid acid), resulting in high energy consumption in the fractionating column
Solution Approach 1:
The separation process is divided into two independent fractionating columns operating at different pressures. The first column separates light components (C1-C4) from the reactor outlet stream, while the second column separates alkylation oil from unreacted isobutane. This segmentation allows each column to handle a specific separation task efficiently, reducing the total energy consumption compared to a single column handling all separations.
Solution Approach 2:
The invention changes the operating pressure parameter of the fractionating columns. The first fractionating column operates at high pressure (0.5-3.0 MPa) to separate light components, while the second column operates at lower pressure (0.1-1.0 MPa) to separate alkylation oil. This parameter change optimizes the separation efficiency and energy consumption for different separation tasks.
2Productivity
If a large amount of isobutane is recycled to maintain high alkane/alkene ratio in the reaction system, then the reaction efficiency and selectivity are improved, but the energy consumption in the separation process increases significantly, with at least 80% of total energy consumption used in separating alkylation oil from recycled isobutane
Solution Approach 1:
The separation of isobutane recycling is segmented into two stages. The first fractionating column removes light components that would otherwise require additional energy for separation. The second column then separates alkylation oil from isobutane more efficiently. This segmentation reduces the energy burden on any single separation step and optimizes the overall recycling process.
Solution Approach 2:
By operating the first fractionating column at high pressure and the second at lower pressure, the invention optimizes the phase behavior and separation efficiency for different components. This parameter optimization reduces the reboiler duty and condenser load, thereby reducing the energy consumption associated with isobutane recycling.
3Device complexity
If the condensation low-temperature heat of low-carbon hydrocarbons is not effectively recovered and utilized, then the separation process is simple, but the energy consumption becomes very high, with the alkylation process consuming about 100kgEo/ton for liquid acid and 200kgEo/ton for solid acid
Solution Approach 1:
The invention converts the waste heat from the fractionating columns into useful energy by generating steam that drives a turbine for power generation. The low-temperature heat from condensing light components and the high-temperature heat from the reboiler are both utilized to generate steam at different pressures, which then drives the turbine. This transforms what would be waste heat into a beneficial energy source, significantly reducing the net energy consumption of the alkylation process.
Solution Approach 2:
The invention merges the heat recovery system with the power generation system. The steam generated from heat recovery in the fractionating columns is combined and used to drive a turbine, integrating two functions (heat recovery and power generation) into a unified system. This merging maximizes energy utilization and reduces overall energy consumption.
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 effectively saves energy by improving heat utilization, simplifying equipment design, reducing operation complexity, and significantly lowering the overall energy consumption in the separation process.
Implementation Method 1
introduced into a high-pressure fractionating column and subjected to fractionation to obtain a vapor phase stream and a liquid phase stream
Implementation Method 2
introduced into a low-pressure fractionating column and subjected to fractionation, to obtain a low-carbon alkane and an alkylation oil product
Implementation Method 3
the vapor phase stream from the column top is heat-exchanged with the liquid phase alkylation product to be separated and is wholly condensed into the liquid phase
Implementation Method 4
the vapor phase stream from the column top is heat-exchanged with the liquid phase alkylation product to be separated
Data Source
Figure 1~2
AI summary
A process for separating an alkylation product, an alkylation reaction and separation process, and/or a related apparatus. A liquid phase alkylation product from an alkylation reaction unit is introduced into a first heat-exchanger directly or after being pressurized with a pressure pump and heat-exchanged with a vapor phase stream from the column top of a high-pressure fractionating column, then introduced into a second heat-exchanger and further heated to 100°C-150°C, then introduced into the high-pressure fractionating column and subjected to fractionation under a condition of 2.0MPa-4. 0MPa, the vapor phase stream from the column top of the high-pressure fractionating column is heat-exchanged with the liquid phase alkylation product to be separated, a liquid phase stream from the column bottom of the high-pressure fractionating column is introduced into a low-pressure fractionating column and subjected to fractionation under a condition of 0.2MPa-1.0MPa, a low-carbon alkane is obtained from the column top of the low-pressure fractionating colum, and a liquid phase stream obtained from the column bottom of the low-pressure fractionating colum is an alkylation oil product. The process according to the present invention can improve the heat utilization efficiency and reduce the energy consumption of the separation operation in the alkylation process.