China is one the world’s largest manufacturers of electronics and the largest consumer of semiconductor products, accounting for about 40% of global consumption. In 2014, sales in the integrated circuit industry grew by an estimated 18%, with the industry generating more than 250 billion Yuan.
But dealing with wastewater from the production process can be potentially hazardous. The source of wastewater can be divided into three categories — manufacturing wastewater, drainage from ultrapure water-based manufacturing and washing exhaust. When classified by type of contaminants, it can be divided into acid-alkali wastewater, wastewater containing fluoride, cyanide wastewater, grinding wastewater and heavy metal wastewater.
Chemical precipitation
The most widely adopted method in wastewater treatment is chemical precipitation which uses chemicals to react with dissolved ions to produce indissoluble sediments. The treatment of wastewater containing fluorine involves calcium ions reacting with fluoride ions, creating calcium fluoride precipitate which is then removed.
In order to reduce the residual concentration of fluorine ion, calcium concentration can be increased to achieve the expected treatment effect.
The Verderflex VF range of industrial hose pumps are widely used in this application for dosing lime, calcium chloride and other similar agents.
The abrasive nature of lime creates continual wear problems for progressing cavity pumps leading to ongoing high stator replacement costs and frequent maintenance downtime. Lime is also usually too viscous for diaphragm pumps, causing them to clog up resulting in continual maintenance requirements.
Verderflex dosing pumps have a linear flow-speed characteristic, ideal for feedback control systems, allowing precise control of the chemicals being dosed, minimising chemical usage.
The application uses a number of VF80 hose pumps to dose 10% lime media at a flow rate of 17.6m³/h and working pressures of 2 bar. The pumps have a smooth liquid passage, there are no opportunities for product to settle and the peristaltic action keeps product in suspension.
