A Process of Preparing APT by Extraction Method with Zero Liquid Discharge

Currently, there are three industrial methods for purifying the Ammonium paratungstate (APT) solution from the sodium tungstate solution: chemical method, ion exchange method, and solvent extraction method. Wherein the classical chemical method consumes large energy and has low production, it has been less frequently used. Both ion exchange and solvent extraction have their own advantages and disadvantages.

Compared with the solvent extraction method, the ion exchange method has a short process flow and simple operation, but has the disadvantages of large water consumption and large discharge of wastewater. In addition, the crystallization mother liquor of the ion exchange method cannot directly return to the main process and requires an auxiliary recovery process. The advantage of solvent extraction under acidic conditions is that the water consumption of the process and the amount of wastewater discharged is small, which is advantageous for areas where water is limited and drainage is difficult. However, the purification and impurity removal for preparing ammonium paratungstate by solvent extraction method is difficult to meet the standards of zero liquid discharge and water recycling.

As the current environmental protection standards are getting higher and higher, it is imperative to upgrade the environmental protection and production capacity of the APT production line. According to this regulation, some scholars have modified the process of preparing ammonium paratungstate by extraction method, and established a zero liquid discharge and water recycling.

The process is as follows:

1) The tungsten trioxide and the caustic liquid containing more than 80% of tungsten are put into the pulping tank according to the ratio: 4:1, the particle size of the tungsten trioxide is 180-200 mesh, and silicon inhibitor (contains 1/15~ 1/20 of tungsten trioxide) is added and stirred for 30 minutes to homogenize it, and then pumped into an alkali leaching reactor.

2) Alkali leaching: The alkali leaching device comprises at least an alkali leaching reactor, a supporting pump, a slurry tank, a gas-liquid separation device and a connecting pipe, wherein the alkali leaching reactor has an inlet/discharge port, an emptying valve, a compressed air pipe, The temperature meter and the pressure gauge have a discharge port connected to the gas-liquid separation device, and the gas-liquid separation device is connected to the slurry tank.

3) Pressure filtration: The pressure filtration device includes at least a plate and frame filter press, a matching pump, a filtrate storage tank and a connecting pipe. The plate frame filter press has a liquid pan below the filter plate, and a slag discharge port is arranged below the liquid pan. The liquid pan can be flexibly pushed and pulled from the bottom of the plate filter press. The liquid discharge port on the liquid pan is connected with the filtrate storage tank, and the tungsten liquid peak feed pipe is also arranged above the filtrate storage tank.

4) Precision filtration: The precision filtration device includes at least a precision filter, a filtrate storage tank and a connecting pipe, and the precision filter feed port is connected with the bottom discharge port of the filtrate storage tank in step 3.

5) Extraction and stripping: The extraction and stripping system includes at least an extraction tank, a clarification tank, a stripping tank, a matching pump, a high-position tank, a low-position tank and a connecting pipe, wherein the extraction tank has an extractant inlet and a fine filtrate feed, respectively. The mouth, the extractant outlet, the raffinate outlet, the fine filtrate feed port are connected to the fine filtrate storage tank in the step 4 precision filtration, and the extract liquid circulation tank is connected to the raffinate outlet.

6) Desulfurization: The vulcanization and degreasing device comprises at least an activated carbon column, a vulcanization tank, a matching pump and a connecting pipe, wherein the activated carbon column comprises an upper feed port, an upper emptying port, and a bottom discharge port.

7) Molybdenum removal: The molybdenum removal apparatus includes at least a precision filter, a compact moving bed, a vulcanized bed, a resin conveyor, and a matching pump and a connecting pipe, wherein the bottom of the vulcanization tank in the 6 vulcanization degreasing port is connected with a precision filter. The feed port of the precision filter is connected to the lower feed port of the compact moving bed, the top of the compact moving bed is provided with a resin inlet, and the bottom is also provided with a resin outlet and a resin inlet connected to the resin conveyor. The resin conveyor is provided with a liquid inlet and a liquid outlet, wherein the liquid inlet and the precision filter are connected by a three-way, the liquid outlet is connected to the resin inlet of the vulcanization bed, and the fluidized bed is provided with compressed air.

8) Crystallization: The crystallization apparatus includes at least a crystallizer, a suction filter tray, a lifter, a leaching tower, and an exhaust fan, wherein the crystallizer has a feed port, an observation hole, a bottom discharge port, a vent hole, and a crystal solution from the crystal solution. The bottom discharge port is discharged and flows into the suction filter tray. The suction filter tray is connected to the vacuum lifter, and the liquid is sucked into the liquid lifter. The crystal is left in the suction filter tray, and the exhaust port and the rinse on the crystallizer are drained. The tower is connected, and the leaching tower is connected with the exhaust fan. When crystallization, the exhaust fan extracts part of the ammonia gas and water vapor in the kettle and absorbs it through the leaching tower.

9) Causticization: The causticizing device includes at least a raffinate circulating tank, a causticizing pulping tank, a causticizing slurry storage tank, a filter press, a matching pump and a connecting pipe, wherein the causticizing pulping tank is framed and stirred. The remaining liquid flows into the raffinate circulation tank through the raffinate outlet of the extraction tank in the 5 extraction reaction, and is pumped into the causticizing pulping tank for causticization, and the causticized slurry pump is allowed to stand in the caustic slurry storage tank. .

10) Molybdenum recovery: The molybdenum recovery unit includes a molybdenum reaction tank, a box filter press, an acid regulating liquid storage tank, a matching pump and a connecting pipe, wherein the bottom discharge port of the molybdenum reactor and the box filter press feed The port is connected by a pump, and there is a slag discharge port below the box filter press.

11) Tungsten recovery: The tungsten recovery device comprises at least an activated carbon column, a precision filter, an ion exchange column, a matched pump and a pipeline, wherein the 10 liquid molybdenum recovery tank is connected with the precision filter inlet port, and the The feed port is connected to the top feed port of the activated carbon column, and the bottom outlet of the activated carbon column is connected to the top feed port of the ion exchange column.

At this point, the useful metals such as tungsten and molybdenum in the tail liquid are recovered, which can avoid the loss of tungsten and increase the additional output value, thereby achieving the purpose of zero liquid discharge and improving economic efficiency.

• < Prev
• Next >