Distillation Column Heat Integration for Caustic Soda Concentration
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Solution Overview
Problem
The existing 'balanced VCM process' for producing 1,2-dichloroethane (EDC) requires large quantities of cooling water to condense vapors, leading to inefficiencies and high costs, especially in remote areas where transporting caustic soda solutions is costly.
Innovation Solution
Utilizing the heat from condensation of vapors in the distillation column to evaporate and concentrate caustic soda solutions, reducing the need for cooling water and optimizing the use of reaction heat by integrating EDC from the direct chlorination unit to heat the distillation column and further concentrate caustic soda solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling water is used to condense vapors from the distillation column, then the distillation process can be operated, but large quantities of cooling water are required leading to high costs and inefficiencies
Solution Approach 1:
The patent combines two separate processes: the distillation column vapor condensation process and the caustic soda solution evaporation process. The heat that would otherwise be wasted in condensing distillation vapors is merged with the evaporation process of caustic soda solution, allowing simultaneous achievement of both condensation and concentration functions.
Solution Approach 2:
The heat exchanger is designed to perform multiple functions: it serves as both the condenser for distillation column vapors and the evaporator for caustic soda solution. This multi-functional design eliminates the need for separate cooling water systems and evaporation equipment.
2Adaptability or versatility
If caustic soda solution is transported over long distances, then production flexibility is maintained, but transportation costs are high especially in remote areas
Solution Approach 1:
The patent applies preliminary action by concentrating the caustic soda solution at the production site before transportation. By performing the evaporation and concentration process beforehand using the integrated heat exchanger, the solution reaches a higher concentration (50% or more) at the source, reducing the volume and weight that needs to be transported to remote locations.
Solution Approach 2:
The patent changes the concentration parameter of the caustic soda solution from approximately 33% at production to 50% or higher before transportation. This parameter change significantly reduces the transportation cost while maintaining production flexibility, as the concentrated solution can be transported and then diluted as needed at the destination.
3Use of energy by moving object
If heat of reaction from direct chlorination is used to heat the distillation column, then energy efficiency is improved, but the heat must be withdrawn to condense vapors requiring large cooling water quantities
Solution Approach 1:
The patent converts what would be a harmful waste (hot vapors needing cooling) into a beneficial resource (heat for evaporation). The heat contained in the vapors from the distillation column, which would normally be lost and require cooling water to remove, is instead utilized to evaporate water from the caustic soda solution, turning a potential energy loss into a useful energy source.
Solution Approach 2:
The patent utilizes phase transitions in both processes: the condensation of distillation column vapors (gas to liquid) and the evaporation of water from caustic soda solution (liquid to gas). By coupling these opposite phase transitions in a heat exchanger, the heat released during condensation is directly used to drive the evaporation process, achieving efficient heat recovery.
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
Substantially reduces the cooling water requirement and lowers transportation costs for caustic soda solutions by effectively utilizing reaction heat for evaporation, enhancing the overall efficiency of the process.
Implementation Method 1
a fractionating EDC purification step, in which the raw EDC, together with the recycle EDC returned from the VCM fractionation step, is freed from the by-products formed in the oxychlorination and EDC pyrolysis steps
Implementation Method 2
utilising the heat of reaction produced in this direct chlorination step; at least part of this EDC which was used to heat the distillation column
Implementation Method 3
concentrate by means of evaporation the caustic soda solution produced as co-product during the production of chlorine; at least part of this EDC which was used to heat the distillation column can then also be used as a heat transfer fluid to concentrate caustic soda solution by evaporation
Implementation Method 4
a direct chlorination step, in which a portion of the required EDC is produced from ethylene (C2H4) and chlorine (Cl2) and generated as pure EDC; Cl2+C2H4→C2H4Cl2 (pure EDC)+218 kJ/Mol
Data Source
AI summary
Process for operating a distillation column for the removal of water and lower-boiling components than 1,2-dichloroethane from 1,2-dichloroethane in which at least part of the heat from condensation of the aqueous vapors from the distillation column is used to concentrate caustic soda solution by evaporation; furthermore, at least part of the 1,2-dichloroethane formed when chlorine and ethylene react in a direct chlorination unit is used to heat said distillation column and can subsequently also be used as a heat transfer fluid to concentrate caustic soda solution by evaporation.