When using anionic polyacrylamide as a flocculant to flocculate the slime particles in the slime water, the time required for the flocculation process is very short. Therefore, the key to the problem is how to ensure that the aqueous solution of anionic polyacrylamide diffuses into the slime water quickly, so that the smaller volume of the flocculant solution can be fully mixed with the larger volume of slime water, so as to ensure full contact with the suspended slime particles in the coal seam injection water to improve the flocculation effect. Thus, in actual production, the flocculation effect is different due to the different dosing systems.
Most coal preparation plants use pipeline transportation and one-time injection dosing method when using flocculants. The advantage of this method is that due to one-time dosing, the medicament is more concentrated when adding, because the viscosity of anionic polyacrylamide is large, the diffusion speed is slow, and the mixing with coal slime water is insufficient in a short time. Therefore, it will inevitably cause the phenomenon that the local concentration is too low, so that the efficiency of the flocculant cannot be fully exerted. In order to ensure the full mixing of the agent and the slime water, and maximize the efficacy of the agent, the following methods can be used to improve the mixing effect of the slime water and the agent when the anionic polyacrylamide adopts the method of one-time dosing.
(1) Spray the flocculant aqueous solution into the pipeline or chute of the coal slime water with a caliper. Due to the spraying effect of the ejector, the added medicament changes from one point to dozens of points, disperses the flocculant aqueous solution, and improves the mixing effect.
(2) Add a baffle to the pipeline or chute. At a certain interval after the dosing point, the method of adding baffles in the conveying pipeline or the chute can make the conveyed coal slime water and the medicine fully mix under the action of turbulent flow, which can improve the mixing effect.
(3) Use pipes or chute to artificially create drop. After the dosing point, the drop of the pipeline or the chute is used to generate turbulent flow, so that the transported coal slime water and the chemical are fully mixed.
The so-called "stepped" dosing is multi-point dosing, that is, in the pipeline or retaining tank for conveying coal slime water, select more than two spaced positions, and divide the amount of drug that should be added into more than two parts and add them to the pipeline or chute. The agent added first is quickly mixed and diffused with water, and the agent added later is smaller than the amount added at one time, and the local concentration will not be too high, so it can also be fully mixed with the coal slime water as soon as possible, which improves the mixing effect. Under the condition of achieving the same flocculation effect, it saves chemicals compared with one-time injection.
Use the same amount of medicine. The step-by-step dosing of anionic polyacrylamide is faster than the one-time dosing in the same time. It shows that the flocculation effect of step-by-step dosing is better than that of one-time dosing. Analysis of the reason may be that in the step-by-step dosing process, after the first dosing, the polar group of the flocculant is in full contact with the suspended particles in the aqueous solution, attracting the counter ions on the surface of the suspended particles in the electric double layer, and at the same time. The surface of the suspended particles close to the polymer flocculant has excess negative charge, which in turn attracts the counter ions in the solution, and attracts more counter ions to gather on the surface of the suspended particles. Before the second dosing, the number of adsorbed counterions increases as time goes on, which further reduces the negative charge on the surface of the suspended particles. However, the dosage of flocculant has not reached enough dosage at this time, and large flocs cannot be produced. But at this time, the "preparation" for flocculation has been done. After the second dosing, the flocculation start is achieved, so that the partially neutralized negatively charged suspended particles can be quickly adsorbed and bridged to form larger flocs and precipitate rapidly.
Through the above discussion, we understand some properties of anionic polyacrylamide that are closely related to production and use. According to these properties, the method and dosing system of how to correctly prepare liquid polyacrylamide have been mastered, as well as the influence of flocculation effect, which has certain guiding significance for the correct use of anionic polyacrylamide in actual production.