Hydrodynamic mixers for superb slurry quality
The core component of the Circumix Dense Slurry technology is the Circumix Mixer. The role of the Circumix Dense Slurry mixer is to receive the fly ash, mix it with the necessary make-up water to produce homogenous dense slurry with 0.8:1…1.2:1 water-to-solid ratio on weight basis to be discharged to the ash disposal area by the dense slurry transport pumps. In addition to fly ash (FA) other solid residuals may be mixed in the slurry such as coarse ash (CA) from the economizer and air heaters, bottom or bed ash (BA) from the furnace with particle size of 15-25 mm (3/4”-1”), or gypsum from the FGD scrubber . Waste waters can also be utilised as make-up water in the system (certain limitations apply).
Each Circumix Dense Slurry mixer consists of
- a pre-mixer head, which receives dry FA and other optional dry input material streams to produce premix slurry by mixing these with the recirculated slurry from the retention tank and with the necessary make-up water;
- a retention tank or mixing tank, which receives the wet input material1 (BA, CA and gypsum slurry) streams and mixes them with the premix slurry from the pre-mixer head; it also provides ample residence time for homogenization;
- two recirculation lines with pumps (head and mixer tank slurry recirculation), which ensure the hydrodynamic agitation and thus the proper mixing and homogenization of the slurry to produce dense slurry of the required quality;
- auxiliary equipment that are necessary for the proper dosing, feeding and discharge of the input and output material streams in order to achieve proper control of dense slurry quality.
1 All these input materials are optional.
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The quantity and quality of the dense slurry is checked and controlled by metering the slurry density. For this reason a proper continuous slurry density metering system is installed. Based on the metered slurry density, the input stream of FA is controlled via rotary dosing feeders on the input lines, in order to maintain an adequate and constant density of the discharged dense slurry stream.
The level of slurry within the mixer retention tank is also monitored and maintained by adjusting the make-up water flow. The set point of the output flow of the DS line can be adjusted by the operators, taking into consideration boiler load, ash generation, silo level, fly ash sold out prospective, and other parameters.
The entire DS mixer system is equipped with adequate flushing devices and drains that prevent the formation of deposits in the system during system down times.