Acetic Acid Heat Exchanger Recycle Loop
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Solution Overview
Problem
Large-sized acetic acid production plants face challenges in efficiently removing reaction heat and maintaining catalyst activity, leading to increased energy costs and equipment expenses, as well as losses of carbon monoxide due to insufficient heat removal methods.
Innovation Solution
Introducing a vaporized stream from a flasher into a heat exchanger for condensation and recycling the condensed stream back to the reactor, eliminating the need for a cooling unit in the reactor and minimizing carbon monoxide loss, while using a miniaturized distillation column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cooling unit is installed in the reactor to remove reaction heat, then the reaction heat can be removed, but carbon monoxide is consumed in pipelines and catalyst activity decreases
Solution Approach 1:
The invention extracts the heat removal function from the reactor by introducing a separate heat exchanger into the recycle line. This allows reaction heat to be removed without exposing the reactor contents to conditions that cause carbon monoxide consumption and catalyst deactivation. The heat exchanger is positioned downstream where the reaction mixture has already left the reactor, thus protecting the catalyst system while still achieving effective heat removal.
Solution Approach 2:
The heat exchanger acts as an intermediary device that transfers heat from the reaction mixture to the incoming reactant stream. This indirect heat removal method avoids direct contact between the cooling medium and the catalyst system, preventing carbon monoxide consumption and maintaining catalyst activity while still achieving the desired temperature control.
2Temperature
If a catalyst recycle line with cooling unit is used to control reactor temperature, then temperature control is achieved, but expensive equipment with high-grade materials is required and heat removal amount is small
Solution Approach 1:
The invention utilizes the incoming reactant stream (methanol and carbon monoxide) as the cooling medium itself. The reactants are cooled in the heat exchanger before entering the reactor, and this cooled stream then serves to absorb reaction heat. This self-service approach eliminates the need for separate cooling systems with expensive high-grade materials, as the process stream itself performs the heat removal function.
Solution Approach 2:
The heat exchanger serves multiple functions: it pre-cools the incoming reactant stream, removes reaction heat from the recycle stream, and potentially condenses some vapor. This multi-functionality reduces the need for separate dedicated cooling equipment, thereby reducing overall device complexity and equipment costs while maintaining effective temperature control.
3Temperature
If reaction heat is removed by condensing flash vapor in a condenser installed to the top of the distillation column, then heat removal is achieved, but the condenser and distillation column size must be increased for large-sized plants
Solution Approach 1:
The invention segments the heat removal function from the distillation column by introducing a dedicated heat exchanger in the recycle line. This separates the temperature control function from the separation function, allowing the distillation column to be sized only for separation requirements rather than having to handle both heat removal and separation. Consequently, the condenser and distillation column sizes can be reduced for large-sized plants.
Solution Approach 2:
The heat removal function is extracted from the distillation column system and placed in a separate heat exchanger located in the recycle line. This extraction allows the distillation column to operate at optimal conditions for separation without the burden of handling large heat removal loads, thereby reducing the required size of the condenser and distillation column for large-sized plants.
4Device complexity
If sensible heat cooling is used in the reactor, then equipment cost is reduced, but the amount of heat removed is insufficient
Solution Approach 1:
The invention utilizes phase transition (condensation) in the heat exchanger to enhance heat removal efficiency. By condensing some of the vapor in the recycle stream, latent heat is released and transferred to the incoming reactant stream. This phase change process provides significantly higher heat removal capacity compared to sensible heat cooling alone, while still using relatively simple equipment without high-grade materials.
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 high-purity acetic acid production with high yield in a resource-saving and energy-saving manner, reducing equipment costs and preventing carbon monoxide loss, even in large-sized plants.
Implementation Method 1
introducing part of a vaporized stream (or a vapor product or a lower boiling point fraction) withdrawn from a flasher into a heat exchanger, condensing the introduced vaporized stream
Implementation Method 2
part of the quantity of heat transferred from the reaction solution to the flash vapor can be removed before heat removal utilizing a latent heat of evaporation in the distillation column
Implementation Method 3
a flash evaporation step for continuously feeding a flasher with a liquid reaction medium (or a reaction mixture) withdrawn from the reactor to separate a liquid stream (or a higher boiling point fraction) and a vaporized stream (or a lower boiling point fraction) from the liquid reaction medium
Implementation Method 4
a distillation step for feeding a distillation column with the vaporized stream for obtaining a purified acetic acid
Data Source
Figure 1
AI summary
A production process of acetic acid comprises a reaction step for continuously allowing at least one member selected from the group consisting of methanol, dimethyl ether, and methyl acetate to react with carbon monoxide in a catalyst system comprising a rhodium catalyst, an iodide salt, and methyl iodide in the presence of acetic acid and water in a reactor 1; a flash evaporation step for continuously feeding a flasher 2 with a liquid reaction medium withdrawn from the reactor 1 to separate a liquid stream and a vaporized stream from the liquid reaction medium; and a distillation step for feeding a distillation column 3 with the vaporized stream for obtaining a purified acetic acid; wherein part of the vaporized stream is introduced into a heat exchanger 7 for condensation, and a liquefied stream condensed by the heat exchanger 7 is recycled to the reactor. The process achieves a production of acetic acid with a high purity in a resource-saving and energy-saving equipment by efficiently removing a reaction heat even in a large-sized plant.