不同氢氧化钙投加条件下两段式氨吹脱处理餐厨垃圾沼液

Performance of Two-stage Ammonia Stripping for Treating Kitchen Waste Digestate under Different Calcium Hydroxide Dosing Conditions

摘要:

为改善氨吹脱技术处理餐厨垃圾沼液时碱剂利用率低、气液接触效果差和氨吸收率低等问题，提高餐厨垃圾沼液氨回收效率和工艺经济性，提出两段式沼液氨吹脱处理工艺，探究了不同氢氧化钙添加量和气流量对餐厨垃圾沼液氨吹脱效果的影响;研究了不同预吹脱（进液速度、预吹脱时间、曝气速度）和氨吹脱条件（投碱量、气液比）对两段式氨吹脱工艺运行效果的影响;并进行了餐厨垃圾沼液氨吹脱工艺经济性评价。结果表明，当氢氧化钙添加量为4.0、8.2、8.7 g/L时，沼液氨氮去除率提升显著（P≤0.05），氨氮去除率分别为85.00%、87.64%、91.79%;当气流量为1、2、3 L/min时总氮去除率分别为 81.80%、82.45%、83.46%（P>0.05）;通过氨吹脱装置试验确定两段式氨吹脱工艺处理餐厨垃圾沼液最适条件为第1段预吹脱8 h（进气速度20 L/min），第2段投碱吹脱12 h （Ca(OH)2投加量8.7 g/L、进气速度40 L/min），最终氨氮去除率为86.61%，总磷去除率为22.21%;对两段式氨吹脱处理餐厨垃圾沼液工艺运行进行评价，投碱氨吹脱条件下处理每立方米沼液成本为7.584元、每千克NH+4-N成本为2.68元。研究结果为两段式氨吹脱工艺处理餐厨垃圾沼液应用提供了参考。

Abstract:

In order to improve the problems of low alkali utilization, poor gas-liquid contact and low ammonia absorption rate in the treatment of kitchen waste digestate by ammonia blow-off technology，and improve the ammonia recovery efficiency of kitchen waste digestate and the economy of the process, a two-stage digestate ammonia blow-off process was proposed, and the effects of different calcium hydroxide additions and gas flow rates on the effect of ammonia blow-off of kitchen waste digestate were investigated;the effects of different pre-blowing conditions （liquid inlet speed, preblowing time, aeration speed） and ammonia blow-off conditions （soda injection volume, gas-liquid ratio） on the operating effect of the two-stage ammonia blow-off process were also evaluated;and the economic evaluation of the process was carried out. The effects of different pre-blowing （feed rate，pre-blowing time, aeration rate） and ammonia blowing conditions （alkali dosage, gas-liquid ratio） on the operation of the two-stage ammonia blowing process were investigated, and the economic evaluation of the ammonia blowing process of kitchen waste digestate was carried out. The results showed that the ammonia nitrogen removal rate of the digestate was increased significantly （P≤0.05）when calcium hydroxide was added at 4 g/L，8.2 g/L and 8.7 g/L, with the ammonia nitrogen removal rates of 85.00%，87.64% and 91.79%, respectively. The total nitrogen removal rate was 81.80%，82.45% and 83.46% （P>0.05） when the gas flow rate was 1L/min，2 L/min and 3 L/min， respectively;the optimal conditions for the two-stage ammonia blow-off process for kitchen waste digestate were determined by the ammonia blow-off device experiment as the first pre-blow-off for 8 h （air intake rate 20 L/min）, and the second alkali blow-off for 12h（Ca（OH）2 dosage of 8.7 g/L and air intake rate of 40 L/min）. The final ammonia nitrogen removal rate was 86.61%, and the total phosphorus removal rates was 22.21%. The two-stage ammonia stripping process was evaluated, and the cost of treating each cubic meter of digestate under alkaline ammonia stripping conditions was 7.584 yuan, and the cost of treating each kilogram of NH+4-N was 2.68 yuan. The results can provide a reference for the application of the two-stage ammonia blow-off process for treating kitchen waste digestate.