摘要
药剂费用过高是阻碍磷酸铵镁结晶技术应用的难题之一,通过磷酸铵镁热解产物循环沉氨可降低药剂费用。但湿法热解会生成热稳定性更好的NH_4MgPO_4·H_2O,从而增加了磷酸铵镁热解的能耗。采用干法热解时,由于不引入额外的水分子,可以降低磷酸铵镁的热解温度。同时,在磷酸铵镁热解过程中加入NaOH碱促试剂,可有效促进磷酸铵镁释放N町,提高热解产物的沉氨效率,但同时上清液磷酸盐残留量也随NaOH添加量和热解温度提高而增加。热解温度为110℃时,直接热解产物沉氨效率为84%,而NaOH碱促热解产物沉氨率达到87%(NaOH与NH_4^+物质的量比为1:1),但此时上清液磷酸盐残留质量浓度达到2.3 mg/L,略高于GB 8978—1996《国家污水综合排放标准》的1.0mg/L,方便废水的后续处理。
This paper is aimed at a focus study on how to promote the removal of the ammonium via struvite pyrolysate with NaOH as a medium.As is known,magnesium and phosphate reagents cost high for the time being,which has been severely hindering the practical application of struvite.In the opinion of the present author,the problem can be solved by taking the advantage of struvite pyrolysate recycling technology,for it could be made easier to decompose the struvite into MgHPO4 when it is heated over the temperature of 60℃,and then the latter can be made to serve as an excellent reagent for ammoniua nitrogen removal.To be more exact,it would be possible to reduce the high cost of magnesium and phosphate reagent by using the struvite pyrolysate recycling technology.Nevertheless,people would say that the thermally less stable struvite can also be made decomposed into the crystalline of NH4MgPO4·H2O in the presence of excessive water content,though it may involve a more energy-consuming process,namely the so-called wet pyrolysis.To reduce the temperature of struvite pyrolysis and save the energy consumption,it is necessary to keep away any more external water content,if possible.Therefore,we suggest using NaOH powder to split the ammonia nitrogen in the process of drying pyrolysis of struvite in our study.The aim of drying pyrolysis is to reduce the energy consumption and pyrolysis temperature.Of course,the addition of NaOH medium can speed up the release of ammonia nitrogen being split,whereas the increase both of the temperature and NaOH molar ratio are likely to promote the rise of phosphate residue in the supernate.Furthermore,at the temperature of 110℃,the removal rate of ammonium nitrogen from struvite can reach 87%with the addition of NaOH medium（molar ratio of NaOH to NIL4~＋ is 1：1）,as compared to 84%of the direct pyrolysis case.In spite of this,the biggest weakness for the struvite pyrolysate recycling with NaOH medium pyrolysis is to leave phosphate residue in the supernate even over 2.3 mg/L（molar rat
出处
《安全与环境学报》
CAS
CSCD
北大核心
2015年第6期239-241,共3页
Journal of Safety and Environment
关键词
环境工程学
磷酸铵镁
热解产物
沉氨
NaOH碱促热解
environmental engineering
struvite
pyrolysate
ammonium removal
NaOH medium pyrolysis
