MAP (guano) crystal precipitating stuffing and preparation thereof

Abstract

The invention relates to a pre-filming MAP filler which can improve the crystallization sedimentation performance of MAP (struvite) and a preparation method. The pre-filming MAP filler and the preparation method are characterized in that porous particles such as waste zeolite, waste active carbon, coke, fly ashes, etc. are used as carriers, magnesium, phosphate and ammonia-nitrogen are used as raw materials, the mol ratio among N, P and Mg is 1:1:1.0 to 2.0, and an MAP film is formed on the surface of the carriers through fluidized reaction. The filler is put in ammonia-containing phosphorus wastewater, so the crystallization sedimentation performance of the MAP (struvite) on the surface of the pre-filming filler can be enhanced obviously; the test shows that the crystal nucleus growth velocity is increased about 20 percent compared with a common amorphous filler carriers. In addition, the carriers are pre-filmed, thereby being beneficial for the MAP film-forming and increasing the firmness of the film. The pre-filming MAP filler and the preparation method adopt external circulation fluidized reaction to prepare the pre-film, and the friction between the carriers is reduced, thereby being also beneficial for the film-forming on the carriers. Air is added before reaction for pressurizing, thereby being beneficial for the formation of the porous pre-filmed MAP carriers and increasing the porosity of the pre-filmed carriers obviously.

Description

technical field [0001] The invention relates to a pre-film MAP filler capable of improving the crystallization and precipitation performance of MAP (struvite) and a preparation method thereof. Background technique [0002] Struvite (MAP), molecular formula MgNH 4 PO 4 ·6H 2 O is a white crystal that is insoluble in water, and its solubility product in water at room temperature is 25×10 -13 . By adding chemical reagents such as magnesium chloride, magnesium oxide, magnesium hydroxide and other magnesium sources, the ammonium phosphorus in the wastewater can be formed into struvite crystals and precipitated to achieve the removal of nitrogen and phosphorus pollutants. The recovered struvite can be used as a slow release fertilizer. An important problem in the MAP crystallization precipitation method is that the growth of MAP crystals is slow and the crystal nucleation time is long, which makes the treatment efficiency of sewage treatment low, the residence time of treated...

AI Technical Summary

Problems solved by technology

However, on the whole, changing the pH value, the ratio of nitrogen, phosphorus, and magnesium, and adjusting the precipitation reaction conditions require a large degree of supersaturation, and the increase in by-products has no obvious effect on improving the MAP precipitation.

Therefore, in the prior art, non-MAP crystals are generally used. The nucleation selectivity of this non-mother crystal seed is poor, not only the space for crystal growth is small, but also the particle size and uniformity of crystal growth are difficult to control.

Secondly, because the wastewater contains various particulate matter, the supersaturation required for the nucleation process is lower than that under homogeneous conditions. If there are other particulate matter, a large amount of magnesium hydroxide or phosphoric acid may be formed before MAP is formed. Magnesium precipitates, the denitrification effect is reduced, the mother crystal is not easy to obtain, and the nucleation rate and the number of nucleation crystal nuclei are difficult to control

The above results in the formation of a large number of fine MAP particles, and the crystalline particles are not uniform, which is not only difficult to recycle, but also the quality of recovered MAP is poor