Technology
Renex has been thoroughly researching ways to ensure that the amount of waste materials being disposed to landfill is reduced.
In order for this target to be met, we recognise that investment in advanced treatment technologies plays a vital role.
Our permanent plants are designed to treat thousands of tonnes of waste materials per annum.
In many cases, after treatment, the treated material can be used again without hazard to the environment and will become biologically active.
The purpose of our facilities is predominantly to clean hydrocarbons and other volatile contaminants from materials.
Plant designs are based on a safe and reliable thermal treatment.
The thermal treatment system typically consists of a dryer, pyrolysis kiln, and a central combustion chamber. The gas cleaning system is a five (5) stage system consisting of a spray dryer, fabric filter, activated carbon filter and two acid gas scrubbers.
A Renex plant is based on proven best available commercial reference plants that have been operating in many parts of the world for many years.
Sophisticated Pyrolysis system:
The proposed pyrolysis system is based on sophisticated European thermal desorption technology comprising of an indirectly heated rotary kiln.
The waste materials are mixed to provide sufficient energy to fuel the plant without the need for auxiliary fuel. This "Waste-To-Energy" principle ensures the sustainability of the plant's operation and minimises its greenhouse gas emissions.
The rotary kiln evaporates moisture in the feed material and decomposes and gasifies volatile organic matter (e.g. hydrocarbons) and inorganic substances (e.g. mercury and cyanides) through radiation and convection at a temperature of 600° The heating occurs in the absence of oxygen at relatively low temperatures and thus prevents the generation of dioxins.
Due to the gentle nature of the heating process and the relatively low temperatures within the kiln, the treated waste materials generally maintain their structure and properties. This allows the materials to be used again without hazard to the environment and allows them to remain biologically active. For example, tests have shown that treated soil can be easily planted after blending with compost. The soil is then suitable for reuse.
The thermal efficiency of the pyrolysis system is increased by the installation of a dryer which dries the feed soil prior to its entry into the rotary kiln. The heat necessary to dry the feed soil is obtained from the exit gases of the combustion chamber.
The volatised contaminants from the rotary kiln and a pre-dryer are fed into a combustion chamber where they are completely destroyed by combustion at a temperature of 1200° a residence time of 2 seconds. An oxygen surplus of more than 1.5 times is maintained in the combustion chamber to ensure sufficient combustion of contaminants.
"Best practice" Air pollution control system
Renex incorporates an expensive air pollution control system to ensure that emissions are well within EPA limits.
The air pollution control system consists of fabric filters, wet scrubbers and activated carbon filters that provide sufficient pollution control from the gases stemming from the thermal treatment system.
These unit operations have been used for this application for many years.
Wet chemical scrubbing is considered the best available control technology for acid gas control applications. The wet scrubbers offer higher removal efficiencies compared to dry scrubbers.