Several mineral and metallurgical processes require gas-liquid or gas-slurry mass transfer for chemical reactions to occur.

For example:

• Gold leaching using aerated cyanide solutions
• Oxidation of sulphide minerals
• Ferric generation
• Chemical decontamination and soil remediation
• Alkaline sulphidisation
• Waste water and effluent oxidation

In general, mass transfer at the gas-liquid interface is rate controlling. Since 1997 Maelgwyn Mineral Services have been improving the design and operation of the Aachen Reactor and today many of the reactors are installed world-wide in a range of applications. MMS lease the Aachen Reactors to clients on maintenance and support service agreement.

Development

The concept for mineral slurry reactors originated in Germany, and was developed in the 1970's for flotation. The Aachen Reactor is designed to improve gas-liquid mass transfer using energy provided in pipeline flow. The fundamental principle is the use either of a slot aerator or a micro-fine gas diffuser made from high-tech, non-blinding materials in a high velocity flowstream. Additionally, a secondary chamber provides regeneration of bubble surfaces using various hydrodynamic effects.

The objective is to increase utilisation of the gas phase, thus reducing overall energy and reagent costs. The reactor contains no moving parts, and is designed to withstand erosive effects of mineral slurries. Materials of construction can be selected according to application.

General information

The Aachen Reactor is designed to facilitate mass transfer by increasing the dispersion of gas in a process fluid or slurry. This results in improved gas utilisation and efficiencies. This is particularly appropriate, for example, in the leaching of gold ores with cyanide and in chemical and waste water treatment processes where large amounts of gases are required to be dissolved in fluids. The reactor is especially efficient for high rate oxidation of sulphides. The reactor accelerates the slurry or solution stream at the gas addition point and increases shear rates in the subsequent flow mixing zone.  The reactor has been designed to maximise the phase interface surface area at this point in the mixing zone by means of a proprietary gas diffusion system which generates extremely fine gas bubbles. The total pressure, under which the unit operates, can be selected according to the requirements of the process.

The Aachen Reactors consist of two sections:

1. A novel bubble generation system made from advanced materials
2. The pressure/ after mixing/ cavitation chambers

The pulp enters the unit on the reactor’s side and exits through the pressure chambers. gas is injected into the reactor section perpendicular to the pulp flow. The reactor, which is manufactured from advanced materials, is designed to generate very fine bubbles. These fine bubbles then pass through the pressure chambers where pressure, excellent mixing characteristics and cavitation are employed to ensure that the bubbles do not coalesce or flash off, so forcing the micro bubbles into solution.

The Aachen Technology sets itself apart from spargers and other in-line reactors in the following ways:

1. It has a unique mode of injection into the pulp.
2. The novel ceramic reactor generates micro bubbles that do not coalesce or flash off.
3. Moderate back-pressures of around 2.5 bar are employed which minimises energy costs and pump maintenance.
4. Custom units for specific applications can be built.
5. Pulp flow rates of up to 1000m3/h can be accommodated.
6. Maintenance requirements are minimal.