Solvent-Free Layer Crystallizer for High-Purity Wax Fractionation
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Solution Overview
Problem
Existing methods for fractionating crude mixtures containing oil and wax, particularly those with long carbon chain waxes, are inefficient and result in low yields with poor purity of oil and wax fractions.
Innovation Solution
A method involving solvent-based dewaxing followed by solvent-free deoiling, where the crude mixture is mixed with a solvent, subjected to crystallization stages to separate dewaxed oil and slack wax, and then further processed in a layer crystallizer to obtain hard and soft wax fractions, with recirculation of soft wax to enhance yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If solvent-free crystallization methods are used, then energy consumption is reduced, but the method is only suitable for oils with short carbon chain waxes and cannot handle long carbon chain waxes
Solution Approach 1:
The crystallization process is divided into two distinct stages: first, solvent-based crystallization to remove the majority of wax and reduce energy consumption; second, solvent-free crystallization to further purify the oil and handle long carbon chain waxes. This segmentation allows each stage to be optimized for its specific function, combining the energy efficiency of solvent-free methods with the versatility of solvent-based methods for handling diverse wax compositions.
Solution Approach 2:
A solvent is used as an intermediary substance in the first crystallization stage to enable the separation of wax from oil. The solvent facilitates the dissolution and subsequent crystallization of wax, making the process applicable to oils with long carbon chain waxes. After the first stage, the solvent is removed or reduced, transitioning to the solvent-free second stage, thus using the solvent as a temporary mediator to achieve the desired separation.
2Adaptability or versatility
If high volume of solvent is added for crystallization, then all kinds of waxes can be removed, but the method becomes energetically expensive and requires complex plant
Solution Approach 1:
The process extracts and removes the solvent after the first crystallization stage, separating it from the oil-wax mixture. This extraction step reduces the solvent volume significantly before proceeding to the second crystallization stage, thereby reducing the energy required for solvent recovery and simplifying the overall plant complexity while maintaining the ability to handle all kinds of waxes.
Solution Approach 2:
The crystallization process is divided into two distinct stages: first, solvent-based crystallization to remove the majority of wax and reduce energy consumption; second, solvent-free crystallization to further purify the oil and handle long carbon chain waxes. This segmentation allows each stage to be optimized for its specific function, combining the energy efficiency of solvent-free methods with the versatility of solvent-based methods for handling diverse wax compositions.
3Productivity
If conventional crystallization methods are used, then wax is removed from oil, but the yield is comparably low
Solution Approach 1:
The process employs continuous circulation of the oil phase between the two crystallization stages. The oil that exits the first crystallization stage is fed into the second stage, ensuring that any remaining wax is further removed. This continuous action maximizes the recovery of both oil and wax, significantly improving the yield compared to single-stage or batch processes.
Solution Approach 2:
The process incorporates a feedback mechanism where the output of the first crystallization stage is monitored and fed into the second stage for further purification. The circulation and re-processing of the oil phase ensure that wax removal is maximized, and the yield of both oil and wax fractions is enhanced by continuously optimizing the separation based on the composition of the incoming stream.
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 method achieves a high yield with excellent purity of both oil and wax fractions, is energy-efficient, and can handle crude oils with up to 50% by weight of long carbon chain waxes.
Implementation Method 1
selective dissolution of the oil fraction in a solvent, which does not dissolve the wax
Implementation Method 2
cooling the mixture in a crystallizer so that the wax fraction crystallizes
Implementation Method 3
the wax fraction crystallizes, which is then separated from the liquid solvent-oil phase
Data Source
Figure 1
AI summary
The present invention relates to a method for fractionating a crude mixture comprising at least one oil and at least one wax, which comprises the following steps: (a) mixing the crude mixture with a solvent to obtain a crude solvent-mixture, (b) carrying out at least one crystallization stage with the solvent-mixture obtained in step (a) to prepare a first fraction containing dewaxed oil and a second fraction containing slack wax, (c) carrying out at least one crystallization stage with the second fraction obtained in step (b) in a layer crystallizer, wherein to the second fraction prior to the crystallization in step (c) no solvent or at most 100% by weight of solvent relative to the weight of the second fraction are added, to prepare a third fraction containing hard wax having an oil content of at most 1.5% by weight and a fourth fraction containing soft wax having an oil content of more than 1.5% by weight and (d) circulating at least a part of the fourth fraction into at least one of the at least one crystallization stage of step (b).