Static Mixer Emulsification for Cationic Bitumen Droplet Control
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Solution Overview
Problem
Current methods for preparing cationic bitumen emulsions, such as those using colloidal mills, face challenges with high energy consumption and maintenance costs, and struggle to produce monodisperse emulsions with controlled droplet sizes, especially when diluting very concentrated emulsions.
Innovation Solution
A continuous process involving static mixers is developed, where a bituminous binder is mixed with a cationic surfactant and an aqueous phase at high concentration, followed by controlled pressure differences to achieve emulsions with droplet sizes between 0.2 and 10 μm and bitumen content between 50 and 75% by weight, allowing for monodisperse and submicron emulsion production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If colloidal mills based on rotor-stator principle are used to produce bituminous emulsions, then emulsions with 60% to 70% bitumen content can be produced, but energy consumption and maintenance costs are high
Solution Approach 1:
The patent replaces the mechanical rotor-stator system with a static mixer that uses controlled pressure differences (ΔP ≤ 40 bar) to achieve emulsification. This substitution eliminates the need for high-energy mechanical shearing while maintaining effective bitumen droplet formation and emulsion stability.
Solution Approach 2:
The patent changes the operating parameters by using high bitumen concentration (>80% by weight) as input to the static mixer, which is then diluted to achieve the final 60-70% bitumen content. This parameter change allows the system to operate at lower energy consumption while achieving the same final product specification.
2Manufacturing precision
If colloidal mills are used to produce bituminous emulsions, then emulsions with median diameter of 3 to 7 μm can be obtained, but the maintenance costs are high
Solution Approach 1:
The patent replaces the complex mechanical rotor-stator system requiring maintenance with a simple static mixer having no moving parts. The static mixer achieves comparable or better droplet size control (0.5 to 10 μm) through controlled pressure differences, eliminating maintenance requirements while maintaining manufacturing precision.
3Quantity of substance
If continuous dilution of concentrated bitumen emulsion is performed by usual means, then the emulsion can be diluted to lower bitumen content, but the droplet size increases or emulsion breaks
Solution Approach 1:
The patent performs preliminary emulsification at high concentration (>80% bitumen) in the static mixer before dilution. This preliminary action creates a stable, highly concentrated emulsion that resists breaking during subsequent dilution, allowing continuous dilution to 60-70% bitumen content while maintaining droplet size and emulsion stability.
4Manufacturing precision
If static mixers are used with high bitumen concentration (>80% by weight), then monodisperse emulsions with controlled droplet size can be produced, but the emulsion requires further dilution for final applications
Solution Approach 1:
The patent uses the static mixer to perform preliminary emulsification at high bitumen concentration (>80%), achieving precise droplet size control and monodispersity. This concentrated emulsion is then continuously diluted to the final 60-70% bitumen content required for road applications, allowing the system to optimize for both precision and practicality.
Data Source
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AI summary
The invention relates to a method for continuously preparing a cationic bitumen emulsion having a droplet size of 0.2 µm to 10 µm, including the preparation in the static mixer or in a chain of static mixers of a concentrated bitumen emulsion, and the in-line dilution of the emulsion by adding a pressurised flow of aqueous phase to the pipe containing said emulsion in order to obtain a bitumen-in-water emulsion having a droplet size of 0.2 µm to 10 µm and a bitumen content of 50 to 75 wt%. The invention also relates to the preparation of a bimodal cationic bitumen emulsion by mixing a cationic bitumen emulsion prepared according to the invention that has a diameter of less than 2 µm and includes more than 4 kg of surfactants per tonne of emulsion, with an aqueous phase and a bituminous binder. The invention finally relates to a device which allows the preparation of bitumen emulsions, including one or more static mixers, the last static mixer being connected to a pipe, said pipe including means that allow an aqueous dilution phase to be injected under pressure.