AU2007207277A1

AU2007207277A1 - A high efficiency purifying method for recycling coal slurry water

Info

Publication number: AU2007207277A1
Application number: AU2007207277A
Authority: AU
Inventors: Jiongtian Liu; Mingqing Zhang
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2006-01-20
Filing date: 2007-01-22
Publication date: 2007-07-26
Anticipated expiration: 2027-01-22
Also published as: WO2007082492A1; CN1803653A; CN100429156C; AU2007207277B2

Description

IN THE MATTER OF an Application for an Australian Patent Application in the name of CHINA UNIVERSITY OF MINING AND TECHNOLOGY filed under International Patent Application No. PCTICN2007/000236 and IN THE MATTER OF an Application for an Australian Patent. I, Han Bingq of Room 2201, Building A1, PhoenixTown, Shuouanqxili A5, Chaoyang District, Beijing, China 2 translator, do solemnly and sincerely declare that I am conversant with the Chinese and English languages and am a competent translator thereof, and that the following is, to the best of my knowledge and belief, a true and correct translation of International Application No. PCTICN2007/000236. Signature: , q Name: Han Bing 4 Please print Date: .uwi , 2 Translators name STranslators name Translators signature STranslators name A High Efficiency Purifying Method for Recycling Coal Slurry Water Field of the Invention The present invention relates to a high-efficiency clarifying purifying method for recycling coal slurry water, which is especially applicable to recycling coal slurry water that is difficult to purify, and is also applicable to treatment of industrial waste water that consists of substances similar to coal slurry water. Background of the Invention The recycling coal slurry water in coal washery is difficult to purify due to the following reasons: 1) the recycling coal slurry water has high content of clay minerals, which tend to sludge into fine particles with negative charges and thereby cause the recycling coal slurry water to enter into a strongly dispersed state; 2) the charge particles adsorb positive ions in water severely that degrades the water quality and aggravate settlement stability of the fine particles in water; 3) the recycling coal slurry water has low hardness and high clay content, and causes the fine particles to circulate and aggregate in water. At present, polymeric flocculants are usually used to flocculate and settle coal slurry water. Though polymeric flocculants can realize the coal slurry water settlement theoretically, the technique has the following drawbacks in actual applications: 1) it is hard to clarify the coal slurry water coal. The coal slurry water contains a great deal of fine particles. If a small amount of flocculating agent is used, some fine particles will be left and can't be captured during the flocculation process; if a large amount of flocculating agent is used, it will be infeasible in economic aspect, though the coal slurry water can be purified; therefore, the flocculation result is not ideal; 2) the flocculating agent is consumed heavily and steady operation of the system can't be ensured. The coal slurry water in coal washery is usually heavy in volume and circulates at a high rate; therefore, a great deal of flocculating agent has to be added for purifying the coal slurry water thoroughly. Due to the fact that the fluctuations in volume of coal slurry water and content of solid particles are heavy, the technique can't ensure stable content of the recycling coal slurry water and thereby will have influence on stable operation of the system; 3) the cost of coal slurry water treatment is high. A great deal of flocculating agent aggregates with the coal slurry and then is discharged along with the coal slurry, and is not recovered and reused; therefore, the cost of flocculating agent in coal slurry water treatment is very high; 4) the monomers in flocculating agent have some toxicity and will cause secondary contamination. The working principle of polymeric flocculant technique is adsorption and bridging. The present invention utilizes a cheap material and implements purification of coal slurry water by water quality adjustment and control, and therefore has high economical efficiency and applicability. 1 Summary of the Invention In view of the drawbacks in the prior art, the present invention provides a high efficiency purifying method for recycling coal slunrry water, which has strong purification effect, consumes less agent, doesn't cause secondary contamination, and low in cost. To attain the object, the present invention employs the following technical scheme: adding adjustment reagent of water quality into the coal slurry water, wherein, the adjustment reagent of water quality can be a sort of mineral flocculant or compound powder of industrial soluble calcium salts or magnesium salts, or waste water in high hardness and low turbidity can be used. The adding quantity of the adjustment reagent of water quality is determined by detecting the hardness of the recycling coal slurry water; when the detection result of water hardness is lower than the critical value, the adjustment reagent of water quality is added or added further; the critical value of water hardness is the critical water hardness for settlement of the coal slurry water, and is obtained by measurement during operation of the coal slurry water system; the mineral flocculant or the compound powder of industrial soluble calcium salts or magnesium salts is added at a location where the water flow is rapid and favorable for dissolution of the power agent. The adding quantity of the mineral flocculant or the compound powder of industrial soluble calcium salts or magnesium salts can be calculated with the following formula: m g/L = (C 3 td-C) mmol/L + 3 mmol/g, wherein, Ctd is the critical water hardness, C is the hardness of the recycling coal slurry water, and 0 is the content of soluble calcium ions or magnesium ions in the adjustment reagent of water quality. The adding quantity of the waste water in high hardness and low turbidity can be calculated with the following formula: V L/L (Csd - C) mmol/L + (C' - Cstd) mrnol/L, wherein, C n is the critical water hardness, C is the hardness of the recycling coal slurry water, and C' is the hardness of the waste water in high hardness and low turbidity The high efficiency purifying method for recycling coal slurry water provided in the present invention has the following beneficial efficacies: 1) It provides a good water quality environment, which improves settling characteristics of the particles. By increasing water hardness through water quality modification, most of the fine particles agglomerate and settle. Compared to macromolecular flocculi, the agglomerates are in high density and settle quickly, so that the coal slurry water is purified completely, and the system can operate stably; 2) It consumes less adjustment reagent of water quality and ensures stable operation of the system. As the coal slurry water circulates, the water hardness fluctuations are very low; therefore, after the water quality is stabilized, the consumption of the adjustment reagent of water quality is very low. The stable water quality ensures clear coal slurry water circulation and thereby keeps the system operating stably; 2 3) It consumes less agent and is low in cost. Natural mineral substances, soluble salts, and waste water in low turbidity are low in cost; in addition, after the system is stabilized, little agents is added; therefore, the cost is very low. 4) It will not cause secondary contamination and ensures a "green" coal slurry water treatment process. The adjustment reagent of water quality adjusts the settlement environment with calcium ions and magnesium ions, and therefore will not cause secondary contamination. Detailed Description of the Embodiments The high efficiency purifying method for recycling coal slurry water provided in the present invention is to add adjustment reagent of water quality into the coal slurry water. The adding quantity of the adjustment reagent of water quality is determined by detecting the hardness of the coal slurry water; when the detection result is lower than the critical value, add the adjustment reagent of water quality which can be mineral flocculant or industrial soluble calcium salts or magnesium salts, wherein the mineral flocculant can be natural plaster; alternatively, waste water in high hardness and low turbidity can be used as adjustment reagent of water quality. The powder agent can be added at a location where the water flow is rapid and favorable for dissolution of the powder agent in the coal slurry water system, such as the overflow weir of the concentrating equipment. An embodiment is as follows: If the adjustment reagent of water quality is mineral flocculant or compound power of industrial soluble calcium salts or magnesium salts: 1. First, ascertain the water quality of the coal slurry water. Suppose the critical hardness for coal slurry water purification is 10.0 mmol/L and the actual hardness of the recycling coal slurry water is measured as 2.Ommol/L with a hardometer when the system operates stably, the measured hardness is lower than the critical value, and adjustment reagent of water quality should be added; 2. Determine the adding quantity of the adjustment reagent of water quality. Suppose the content of soluble calcium ions and magnesium ions in the adjustment reagent of water quality is measured as 20.0mmol/g with a hardometer, the adding quantity of the adjustment reagent of water quality can be calculated with the following formula: m g/L = (Csd - C) mmol/L + 3 mmol/g, wherein, C Atd is critical water hardness, C is hardness of the recycling coal slurry water, and (3 is the content of soluble calcium ions and mroagnesium ions in the adjustment reagent of water quality. In this embodiment, it is (10.0 - 2.0) mmol/L * 20.0 mmol/g - 0.4 g/L. The adjustment reagent of water quality can be added according to the calculation result. If the adjustment reagent of water quality is waste water in high hardness and low turbidity: 3 1. First, ascertain the water quality of the coal slurry water. Suppose the critical hardness for coal slurry water purification is 10.0 mmol/L and the actual hardness of the recycling coal slurry water is measured as 2.0mmol/L with a hardometer when the system operates stably, the measured hardness is lower than the critical value, and adjustment reagent of water quality should be added; 2. Determine the adding quantity of the adjustment reagent of water quality. Suppose the hardness of the waste water is measured as 20.0mmol/L with a hardometer, the adding quantity of the adjustment reagent of water quality can be calculated with the following formula: V L/L -(Ctd - C) mmol/L + (C' - Cld) mmol/L, wherein, Cstd is the critical water hardness, C is the hardness of the recycling coal slurry water, and C' is the hardness of the waste water in high hardness and low turbidity. In this embodiment, it is (10.0 - 2.0) mmol/L -(20.0 - 10.0) mmol/L = 0.8 L/L. The waste water can be added according to the calculation result. The working principle is as follows: the substances that are difficult to settle in coal slurry water are mainly clay minerals and coal, both of which carry strong negative charges and are repulsive mutually, and thereby increase stability of the water system. The powder-form adjustment reagent of water quality is dissolved in the coal slurry water and releases calcium ions and magnesium ions. A great deal of calcium ions and magnesium ions are dissolved in high-hardness waste water itself, The attachment of calcium ions and magnesium ions to the surfaces of coal and clay particles compresses the double charged layers on the particle surfaces and reduces the Zeta potential of the particles, and thereby increases the efficiency of collision adhesion among the particles and facilitates formation of agglomerates in high density. The agglomerates settle quickly. In that way, the object of purifying coal slurry water is attained. The two types of ions are not affected by external factors severely and can exist stably, and function as the water recycles. Therefore, after the water quality is stabilized, little adjustment reagent of water quality is consumed. 4

Claims

1. A high efficiency purifying method for recycling coal slurry water, which comprises: adding adjustment reagent of water quality to the coal slurry water.

2. The high efficiency purifying method for recycling coal slurry water according to claim 1, wherein, the adjustment reagent of water quality is mineral flocculant or compound powder of industrial soluble calcium salts or magnesium salts.

3. The high efficiency purifying method for recycling coal slurry water according to claim 1, wherein, the adjustment reagent of water quality is waste water in high hardness and low turbidity.

4. The high efficiency purifying method for recycling coal slurry water according to claim 1, 2, or 3, wherein, the adding quantity of the adjustment reagent of water quality is determined by detecting the hardness of the recycling coal slurry water; when the detected water hardness is lower than the critical value, the adjustment reagent of water quality is added or further added.

5. The high efficiency purifying method for recycling coal slurry water according to claim 4, wherein, the critical value of water hardness is the critical hardness for settlement of coal slurry water, and is measured actually when the coal slurry water system operates.

6. The high efficiency purifying method for recycling coal slurry water according to claim 1 or 2, wherein, the adjustment reagent of water quality is added at a location where the water flow is rapid and favorable for dissolution of the power agent in the coal slurry water system.

7. The high efficiency purifying method for recycling coal slurry water according to claim 1 or 2, wherein, the adding quantity of the mineral flocculant or the compound powder of industrial soluble calcium salts or magnesium salts can be calculated with the following formula: m g/L=(C,14d-C) mmol/L - 3 mmol/g, wherein, Ctd is the critical water hardness, C is the hardness of the recycling coal slurry water, and P is the content of soluble calcium ions or magnesium ions in the adjustment reagent of water quality.

8. The high efficiency purifying method for recycling coal slurry water according to claim I or 3, wherein, the adding quantity of the waste water in high hardness and low turbidity can be calculated with the following formula: V L/L (Cta - C) mmol/L - (C' - C.td) mmol/L, wherein, Ctd is the critical water hardness, C is the hardness of the recycling coal slurry water, and C' is the hardness of the waste water in high hardness and low turbidity.