Process for heating the column for distillation of the c3 fraction from an fcc unit by means of a circuit of water heated by streams belonging to units placed upstream and/or downstream of the fcc unit
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Solution Overview
Problem
The separation of propane and propylene by fractionation in fluidized bed catalytic cracking (FCC) units is energetically costly due to their close boiling temperatures, requiring significant energy expenditure for reboiling processes, and existing methods like high-pressure separation with cooling water or low-pressure steam reboiling are inefficient.
Innovation Solution
The process involves heating a hot water circuit used for reboiling the propane/propylene separation column with process fluids from upstream and downstream units, including overhead vapors from mild hydrocracking, hydrodesulfurization reactors, and other high-temperature streams to enhance thermal integration and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-pressure separation with cooling water is used, then the separation of propane and propylene can be achieved, but the energy expenditure is very high due to the need for significant cooling capacity
Solution Approach 1:
The patent changes the pressure parameter from high-pressure (20-25 bars) to low-pressure (10-15 bars and less) operation. This parameter change allows the system to achieve the same separation purity while reducing the energy expenditure for cooling, as lower pressures require less cooling capacity to condense the overhead vapors.
Solution Approach 2:
The patent utilizes phase transitions (condensation of overhead vapors) at optimized pressure and temperature conditions. By operating at low pressure, the condensation temperature is reduced, which decreases the temperature difference between the column overhead and cooling water, thereby reducing the cooling energy requirement while maintaining separation effectiveness.
2Manufacturing precision
If low-pressure steam or hot water circuit is used for reboiling, then the separation can be maintained, but the thermal efficiency is insufficient due to inadequate temperature differences
Solution Approach 1:
The patent merges multiple heat sources into a single integrated reboiling system. It combines low-pressure steam and hot water circuit heating, allowing the system to utilize both thermal sources simultaneously or alternatively to achieve the required reboiling duty with improved thermal efficiency by optimizing the temperature differences in heat exchange.
Solution Approach 2:
The patent employs a composite heating approach using two different thermal media (steam and hot water) with different temperature characteristics. This composite heating system allows flexible optimization of heat transfer efficiency by selecting or combining heat sources based on their temperature profiles and availability, thereby improving overall thermal efficiency.
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 allows for complete reboiling of the propane/propylene fractionation column without using low-pressure steam, minimizing energy costs and improving thermal efficiency by utilizing higher temperature differences across exchangers.
Implementation Method 1
heating the water of a hot water circuit by means of process fluids from units placed upstream and/or downstream of the FCC unit
Implementation Method 2
heating the water of a hot water circuit by means of one or more process fluids coming from units placed upstream and/or downstream of the FCC unit and called fluids hot
Implementation Method 3
reboiling of the propane/propylene fractionation column is not done entirely by heat exchange with process fluids from the FCC unit
Implementation Method 4
addition of calories necessary to reach the temperature at the bottom of the column
Implementation Method 5
separation by fractionation of propane and propylene from a fluidized bed catalytic cracking (FCC) unit
Implementation Method 6
The separation by fractionation of propane and propylene can typically be done: either at high pressure (approximately 20-25 bars) with condensation of the overhead vapors
Implementation Method 7
condensation of the overhead vapors with cooling water
Implementation Method 8
heat recovery at the top of an FCC unit for the reboiling of the propane/propylene fractionation column
Data Source
Figure 1
AI summary
The present invention describes a process for heating the reboiler of the propane/propylene separation column located downstream of an FCC unit and fed with the C3 fraction from said FCC unit, said process consisting in heating the water of a hot water circuit by means of one or more process fluids originating from units placed upstream and/or downstream of the FCC unit and called hot fluids, one of these fluids consisting of the vapours from the top of the fractionation column linked to the mild hydrocracking unit.