Abstract
The efficiency of solid phase retention and dehydration of finely dispersed products of a coal processing plant and a metallurgical enterprise on the module for cleaning and dewatering sludge is investigated. A technique for selecting the operating parameters of equipment based on the determination of the strength criterion of flocs is proposed. A methodology for technological tests has been developed to control the flocculation process and optimize the flow of flocculant depending on the concentration of the solid phase. Industrial tests on the module for wastewater treatment and sludge dewatering using flocculants proved the effectiveness of the developed methodology. It is shown that the conditions for conducting tests on flocculation should correspond to the operating conditions of the circuit apparatus for cleaning and dewatering sludge. These conditions include sludge performance, sludge flow rate in the cross section of pipes and apparatuses, and the flow time from the flocculator to the centrifuge. During the testing of the Module, the solids retention efficiency of 97–99 % was achieved with the strength criteria of flocs in front of a centrifuge of 2–2.5 mm/s. The conditions for the high efficiency of the apparatus chain are the optimization of the aggregation process itself. It is revealed that for the formation of strong flocs it is necessary to regulate the concentration of the solid phase. For coal sludge, the concentration of the solid phase before the flocculant is fed must be maintained no higher than 50–60 g/l, and for gas treatment sludge – no higher than 20–25 g/l. Correction of the concentration of sludge before the flocculator is possible by diluting it with clarified water to the optimum concentration for aggregation. It is found that the moisture content of the sediment and the efficiency of the retention of the solid phase depend on the strength criterion of the flocs. Therefore, the optimization of the flocculant flow rate is possible by controlling and the residual floccule deposition rate after mechanical action in front of the dewatering equipment. The flocculant flow rate must be adjusted depending on the concentration of the solid phase in the sludge to achieve the desired criterion for the strength of the flocs
Highlights
The modern water-sludge scheme of water circulation cycles of many enterprises is heavily overloaded with liquid waste
The efficiency of removing the solid phase in the centrifuge in the sediment and the moisture content of the sediment depend on the strength of the flocs, which can be estimated by the residual deposition rate before the centrifuge
The tests of the Module for wastewater treatment and dewatering of fine sludge confirm the satisfactory operation of the apparatus in a production environment
Summary
The modern water-sludge scheme of water circulation cycles of many enterprises (metallurgical enterprises, coal processing plants, etc.) is heavily overloaded with liquid waste. – properties of sludge: type of dispersed phase and medium, their density; – design parameters of equipment (filters, centrifuges) and their operation mode; – production conditions: solids content in food, separation factor indicator (for centrifuges), sizes of dehydration zones, duration of dehydration, specific equipment throughput, and others; – ways to intensify the dehydration process: the use of flocculants, regulation of the concentration or dispersion of the solid phase in the nutrition of the dehydration equipment, optimization of aggregation conditions, etc. In order to increase the efficiency of cleaning and dehydration of fine liquid waste, a smallsized module for wastewater treatment and waste dehydration is tested on the basis of a thin-layer sedimentation tank, modernized sedimentation centrifuges using flocculants The use of such a module will allow unloading radial thickeners and filter presses of the water cycle of enterprises by cleaning and subsequent dewatering of industrial sludge.
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