FLOTATION PROCESS FOR TREATING COAL SLIME BY USING SALT-CONTAINING WASTE WATER

Abstract

A flotation process for treating coal slime in which coal slime, a collecting agent and a frothing agent are fed into an ore slurry pretreater, and salt-containing waste water of coal chemical industry discharged from a coal chemical enterprise is fed as dilution water into the ore slurry pretreater and mixed together to complete mineralization; the mineralized ore slurry is subjected to a rough separation operation, the products obtained in the rough separation operation are subjected to a fine separation operation, and the ash content of the fine separation tailings is tested with an ash analyzer; the tailings are returned into the ore slurry pretreater for separation again if the ash content of the fine separation tailings is greater than 20%; otherwise the tailings are discharged as fine separation tailing products if the ash content of the fine separation tailings is smaller than 20%; the fine separation tailing products discharged through a pipeline enter into a pressure filter for dehydration, and filter cakes are discharged as a finally accepted concentrate product after the dehydration in the pressure filter.

Claims

1. A flotation process for treating coal slime by using salt-containing waste water, comprising the following steps: feeding floating coal slime into an ore slurry pretreater from the bottom of the ore slurry pretreater through a first pipeline, and feeding a collecting agent and a frothing agent into the ore slurry pretreater through a second pipeline to form mixed ore slurry; feeding salt-containing waste water of coal chemical industry discharged from a coal chemical enterprise into an agitating vessel and agitating it to a homogeneous state at 30,000 mg/L salt water concentration; feeding the salt water as dilution water with a circulating pump into the ore slurry pretreater through a third pipeline, the salt concentration of the mixed liquid in the ore slurry pretreater is increased as wherein the salt-containing waste water of coal chemical industry is continuously fed into the ore slurry pretreater, and thus the consumption of the agents in the flotation process can be effectively reduced by virtue of the improved salt concentration, while the inorganic salt ions and residual organic substances in the salt-containing waste water of coal chemical industry are absorbed on the surface of the floating coal slime; driving the mixed ore slurry in the ore slurry pretreater to circulate by driving an impeller in the ore slurry pretreater to rotate, and completing preliminary mineralization with the participation of the collecting agent and the frothing agent, and feeding the preliminarily mineralized mixed ore slurry with a slurry pump through a fourth pipeline into a rough separation flotator for rough separation operation; discharging the rough separation tailings in the rough separation flotator directly as roughly separated tail coal products through a tailings port at the bottom of the flotator after the rough separation operation of the mixed ore slurry, and feeding the overflow liquid separated by the rough separation flotator through a fifth pipeline into a sedimentation filtering centrifugal dehydrator for dehydration operation; feeding the filtrate obtained in the dehydration operation of the overflow liquid with a slurry pump through a sixth pipeline into an agitating vessel, discharging the filter residue obtained in the filtering operation as a rougher concentrate product through a seventh pipeline, while supplementing the collecting agent and the frothing agent in quantity of 10% of consumed agents in the rough separation operation into the agitating vessel; after the filtrate is completely mineralized in the agitating vessel, feeding the completely mineralized filtrate with a slurry pump through an eighth pipeline into a fine separation flotation column for fine separation operation, whereupon the flotation concentrate in the completely mineralized filtrate floats upward, flows over an overflow weir at the top of the fine separation flotation column and flows out of the fine separation flotation column through a ninth pipeline, while the flotation tailings in the completely mineralized filtrate settle down in the fine separation flotation column and are discharged via an underflow port through a tenth pipeline; testing the ash content of the fine separation tailings flowing out through the tenth pipeline with an ash analyzer; returning fine separation tailings through the coal slime feeding first pipeline into the ore slurry pretreater for separation again if the ash content of the fine separation tailings is greater than 20%; otherwise discharging fine separation tailings directly as fine separation tailing products if the ash content of the fine separation tailings is smaller than 20%; feeding the flotation concentrate discharged out of the ninth pipeline into a pressure filter for dehydration, whereupon salt water is formed by the filtrate produced in the dehydration process because the salt concentration of the filtrate is decreased as a result of adsorption of a part of metal salt ions in the filtrate on the mineral surface; directly transporting the salt water as make-up water for fine separation operation to the agitating vessel of the fine separation flotation column; discharging filter cakes formed in the dehydration process in the pressure filter as a finally accepted concentrate product from the bottom of the pressure filter; and repeating the above process, until the entire flotation process is completed.

2. The flotation process for treating coal slime by using salt-containing waste water according to claim 1, wherein the salt water is also directly conveyed through an eleventh pipeline to an industrial waste water treatment plant for recycling treatment, and the salts produced in the waste water treatment plant through concentration and evaporation are used as make-up salts for rough separation operation and fine separation operation, depending on whether the concentrations of the feeding salts meet corresponding criteria.

3. The flotation process for treating coal slime by using salt-containing waste water according to claim 1, wherein the salt water concentration of the mixed ore slurry under the mixing conditions in the rough separation operation is controlled to be 11,700 mg/L to 35,100 mg/L, and appropriate salts must be supplemented according to the actual requirement in the rough separation operation to ensure stable salt water concentration in the rough separation operation; and the salt water concentration of the mixed ore slurry in the fine separation operation is controlled to be 1,170 mg/L to 3,510 mg/L.

4. The flotation process for treating coal slime by using salt-containing waste water according to claim 1, wherein after the filtrate formed through the dehydration operation is fed with the slurry pump through the pipeline into the agitating vessel, some salts must be supplemented into the agitating vessel according to the actual demand of production for salt water concentration adjustment while the collecting agent and the frothing agent in quantity of 10% of consumed agents in the rough separation operation are supplemented into the agitating vessel to ensure stable salt water concentration required for the fine separation operation, wherein the collecting agent is diesel oil, and the frothing agent is sec-octyl alcohol.

5. The flotation process for treating coal slime by using salt-containing waste water according to claim 1, wherein components of the salt in the salt-containing waste water of coal chemical industry are NaCl, Na.sub.2SO.sub.4, CaCl.sub.2 and CaSO.sub.4.

6. The flotation process for treating coal slime by using salt-containing waste water according to claim 1, wherein when the mixed ore slurry is separated in the rough separation flotator, metal salt ions are extensively dissolved in the flotation solution in the rough separation flotator after the mixed ore slurry is mineralized by the ore slurry pretreater; when an air filler valve of the rough separation flotator is opened, the metal salt ions compress the double electron layers of froths, decrease the liquid drainage rate of the liquid phase among the froths, prevent the froths from merging with each other, and thereby increase the frothing rate of the froths in the floatation tank of the rough separation flotator and stabilize the thickness of the flotation froth layer; a scraper valve is opened for separation operation after the froth layer is stabilized.

7. The flotation process for treating coal slime by using salt-containing waste water according to claim 1, wherein after the filtrate is completely mineralized in the agitating vessel, the filtrate enters into the fine separation flotation column for fine separation operation; the gangue particles included among froth channels are washed away by the flushing water at the top of the fine separation flotation column, and finally the gangue particles are directly discharged along with the flotation tailings; the flotation concentrate floats upward, flows over the overflow weir at the top of the fine separation flotation column, and flows out of the fine separation flotation column through the ninth pipeline, while the flotation tailings settle down in the fine separation flotation column and are discharged via the underflow port of the fine separation flotation column through the tenth pipeline.

8. The flotation process for treating coal slime by using salt-containing waste water according to claim 3, wherein components of the salt in the salt-containing waste water of coal chemical industry are NaCl, Na.sub.2SO.sub.4, CaCl.sub.2 and CaSO.sub.4.

9. The flotation process for treating coal slime by using salt-containing waste water according to claim 4, wherein components of the salt in the salt-containing waste water of coal chemical industry are NaCl, Na.sub.2SO.sub.4, CaCl.sub.2 and CaSO.sub.4.

Description

DESCRIPTION OF DRAWINGS

[0025] FIG. 1 is a schematic flow chart of the separation process in the present invention;

[0026] FIG. 2 is a schematic structural diagram of the separation apparatus in the present invention.

[0027] In the figures: 1-agitating vessel; 2-circulating pump; 3-ore slurry pretreater; 4-slurry pump; 5-rough separation flotator; 6-sedimentation filtering centrifugal dehydrator; 7-slurry pump; 8-agitating vessel; 9-slurry pump; 10-fine separation flotation column; 11-pressure filter; 12-ash analyzer.

EMBODIMETS

[0028] Hereunder the present invention will be further detailed in an embodiment with reference to the accompanying drawings:

[0029] As shown in FIGS. 1 and 2, the flotation process for treating coal slime by using salt-containing waste water provided by the present invention includes the following steps:

[0030] Floating coal slime is fed into an ore slurry pretreater 3 from the bottom of the ore slurry pretreater 3 through a pipeline b, and a collecting agent and a frothing agent are fed into the ore slurry pretreater 3 through a pipeline c, so as to form mixed ore slurry;

[0031] Salt-containing waste water of coal chemical industry discharged from a coal chemical enterprise is fed into an agitating vessel 1 and agitated to a homogeneous state at 30,000 mg/L salt water concentration, wherein the components of the salt are NaCl, Na.sub.2SO.sub.4, CaCl.sub.2 and CaSO.sub.4; the salt water is fed as dilution water with a circulating pump 2 into the ore slurry pretreater 3 through a pipeline a, the salt concentration of the mixed liquid in the ore slurry pretreater 3 is increased as the salt-containing waste water of coal chemical industry is continuously fed into the ore slurry pretreater 3, thus the consumption of the agents in the flotation process can be effectively reduced by virtue of the improved salt concentration, while the inorganic salt ions and residual organic substances in the salt-containing waste water of coal chemical industry are absorbed on the surface of the floating coal slime;

[0032] The mixed ore slurry in the ore slurry pretreater 3 is driven to circulate by driving an impeller in the ore slurry pretreater 3 to rotate, and preliminary mineralization is completed with the participation of the collecting agent and the frothing agent, and the preliminarily mineralized mixed ore slurry is fed with a slurry pump 4 through a pipeline d into a rough separation flotator 5 for rough separation operation; when the mixed ore slurry is separated in the rough separation flotator 5, metal salt ions are extensively dissolved in the flotation solution in the rough separation flotator 5 after the mixed ore slurry is mineralized by the ore slurry pretreater; when an air filler valve of the rough separation flotator 5 is opened, the metal salt ions compress the double electron layers of the froths, decrease the liquid drainage rate of the liquid phase among the froths, prevent the froths from merging with each other, and thereby increase the frothing rate of the froths in the floatation tank of the rough separation flotator 5 and stabilize the thickness of the flotation froth layer; a scraper valve is opened for separation operation after the froth layer is stabilized; the coarse-particle filter residue in the rough separation flotator 5 is discharged directly as roughly separated tail coal products through a pipeline after the rough separation operation of the mixed ore slurry, and the overflow liquid separated by the rough separation flotator 5 is fed into a sedimentation filtering centrifugal dehydrator 6 for dehydration operation; the salt water concentration of the mixed ore slurry under the mixing conditions in the rough separation operation is controlled to be 11,700 mg/L-35,100 mg/L, and appropriate salts must be supplemented according to the actual requirement in the rough separation operation to ensure stable salt water concentration in the rough separation operation;

[0033] The filtrate obtained through dehydration of the overflow liquid is fed with a slurry pump 7 through a pipeline g to agitating vessel 8, while the filter residue h is discharged as a rougher concentrate product through a pipeline; at the same time, the collecting agent and the frothing agent in quantity of 10% of the consumed agents in the rough separation operation are supplemented into the agitating vessel 8, so that the filtrate is completely mineralized in the agitating vessel 8; the completely mineralized filtrate is fed with a slurry pump 9 through a pipeline into the fine separation flotation column 10 for fine separation, the salt water concentration of the mixed ore slurry is at 1,170 mg/L to 3,510 mg/L in the fine separation operation; the flotation concentrate in the completely mineralized filtrate floats upward and flows over an overflow weir at the top of the fine separation flotation column 10, and flows out of the fine separation flotation column 10 through a pipeline k, while the flotation tailings in the completely mineralized filtrate settle down in the fine separation flotation column 10 and is discharged via a underflow port through a pipeline j; after the filtrate formed through the dehydration operation is fed with the slurry pump 7 through the pipeline g into the agitating vessel 8, some salts must be supplemented into the agitating vessel 8 according to the actual demand of production for salt water concentration adjustment while the collecting agent and the frothing agent in quantity of 10% of consumed agents in the rough separation operation are supplemented into the agitating vessel 8, so as to ensure stable salt water concentration required for the fine separation operation, wherein the collecting agent is diesel oil, and the frothing agent is sec-octyl alcohol;

[0034] The ash content of the fine separation tailings flowing out through the pipeline j is tested with an ash analyzer 12; fine separation tailings o is returned through the coal slime feeding pipeline b into the ore slurry pretreater 3 for separation again if the ash content of the fine separation tailings is greater than 20%; otherwise fine separation tailings p is discharged directly as fine separation tailing products if the ash content of the fine separation tailings is smaller than 20%;

[0035] The flotation concentrate discharged out of the pipeline k is fed into a pressure filter 11 for dehydration, so that salt water n is formed by the filtrate produced in the dehydration process because the salt concentration of the filtrate is decreased as a result of adsorption of a part of metal salt ions in the filtrate on the mineral surface; the salt water n is directly transported as make-up water for fine separation operation to the agitating vessel 8; filter cakes m formed in the dehydration process in the pressure filter 11 are discharged as a finally accepted concentrate product; the salt water n is also directly conveyed through a pipeline to an industrial waste water treatment plant for recycling treatment, and the salts produced in the waste water treatment plant through concentration and evaporation are used as make-up salts for rough separation and fine separation, depending on whether the concentrations of the feeding salts meet corresponding criteria; after the filtrate is completely mineralized in the agitating vessel 8, the filtrate enters into the fine separation flotation column 10 for fine separation operation; the gangue particles included among the froth channels are washed away by the flushing water/at the top of the fine separation flotation column 10, and finally the gangue particles are directly discharged along with the flotation tailings; the flotation concentrate floats upward, flows over the overflow weir at the top of the fine separation flotation column 10, and flows out of the fine separation flotation column 10 through the pipeline k, while the flotation tailings settle down in the fine separation flotation column 10 and are discharged via the underflow port of the fine separation flotation column 10 through the pipeline j;

[0036] The above process is repeated, till the entire flotation process is completed.