Flash reactor
FR vessels facilitate a low gas and solid retention (and hence reactant contact time) for industrial applications which give rise to a high throughput, pure product and less than ideal thermal distribution when compared to other fluidized bed reactors.
These designs allow for a wide range of current and future applications, including water treatment sterilization, recovery and recycling of steel mill dust, pre-treatment and roasting of metals, chemical looping combustion as well as hydrogen production from biomass.
This configuration is designed to increase the fluid's velocity at the chamber's bottom, allowing for heavy feed particles to be in a continuous circulation that promotes a reaction site for separation processes.
Temperature of this stream is controlled by a coolant emitted by the vessel's spray nozzles D.[1] Whilst a variety of applications are available for a flash reactor, they follow a general set of operating parameters/heuristics that are similar.
This is achieved by the use of centrifugal forces, where it compresses the powder onto the plate's surface, allowing for direct contact between the particles and hot metal, which enables a higher heat transfer rate.
A pipeline flash reactor (PFR) is a relatively new device developed through the principles of a FR thus possessing most of its characteristics, functions and properties.
This eliminates the need for extra mixing tanks which saves space but as a trade-off, the actual reaction site will be dependent on the pipe specifications and velocity of the fluid.
Also, the reactants will leave the PFRs quicker due to a shorter retention time; it was found that effective dispersion of the side stream into the bulk fluid was accomplished in as short as 1 second.
[5] Nonetheless, research has shown a great potential for the use of the FR in recovering zinc from steel mill dust as it provides a strong oxidizing and reducing condition in the reaction vessel, with no waste materials produced.
[10] A typical RecoDust process will often require temperatures from 1600-1650 °C with a dry, pourable, and well-defined grain sized raw material input of approximately 300 kg/h.
Such settings have shown to produce a product output of 40 dm3/hr with a thermal treatment of less than 1.5 s.[6] Flash reactors have enormous potential for replacing or assisting existing primary ore oxidation, reduction or other pre-treatment conditioning processes (e.g. calcining) in metal refinery.
Preheating of crushed or fine ores can be carried out within a FR, utilising the short retention times to most quickly increase temperatures to reach conditions required in later processes.
In iron and ilmenite ores high FR throughputs allows for substantial overall reduction in operating energy consumption, as well as provide a mixing site with other reactants such as hydrogen for briquetting in the main refining process.
[11] The oxidation of crushed particulate ores and the removal of sulfide, arsenic or other contaminants is a crucial separation process in the purification of metals which can be carried out within a FR.
This results in the separation of oxidised ferric compounds from paramagnetic chromite components [13] within the ore at the reactor outlet where the product may be further refined to synthesize iron or rutile downstream.
[12] Hence, continual roasting and volatilisation of sulfur and arsenic allows for the coalescence of gold at the surface of mineral particles which can then be separated efficiently by downstream processes such as leaching.
The use of flash reactors in this scenario allows the use of lower-grade feed materials and a substantial increase in capacity as well as product purity compared to conventional processing.
Flash reactors in tandem with steam methane reforming and gasification, uses waste biomass such as a mixture of cellulose, lignin and other plant material organics to produce hydrogen gas.
