밀폐형 암모니아 스트리퍼/스크러버 시스템의 최적운전인자 도출

Abstract

요지

국내의 질소 폐수 처리기술은 주로 생물학적 질산화/탈질에 초점을 맞추어 개발되어 왔지만, 이는 고농도 암모니아성 질소를 처리하는데 있어 경제성⦁처리 안정성 등의 문제를 가지고 있다. 선진국의 경우는 고농도 암모니아성 질소 폐수를 처리하는데 있어 물리⦁화학적 처리방법들을 연구하며 적용하고 있다. 현재 가장 많이 적용되고 있는 물리⦁화학적 방식은 암모니아 스트리핑이다. 또한, 스트리핑 기술뿐만 아니라 탈기된 암모니아 가스를 처리하는 후단공정에 대해서도 지속적으로 연구되고 있다. 하지만 국내에서 암모니아 스트리핑 기술은 운전미숙과 과도한 유지관리비 문제로 성공적으로 운전되지 못하였다. 따라서, 본 연구에서는 이와 같은 문제점을 극복하기 위하여 고농도 암모니아성 질소 폐수를 발생시키는 J업체에 밀폐형 암모니아 스트리퍼/스크러버 시스템을 설치하여 질소 폐수처리(제거목표: 85%)와 액상비료로서 적합한 인산암모늄 생성(N:P2O5=5%:10%)에 알맞은 최적운전인자를 도출하였고, 설비의 경제성을 분석하였다. 암모니아 스트리퍼/스크러버는 하나의 단일 공정으로 pH조정조, 암모니아 탈기탑, 암모니아 흡수탑, 액비저장조로 구성되어있다. pH조정조에서 고농도 암모니아성 질소 폐수의 pH를 높여 free ammonia의 분율을 높인 후, 암모니아 탈기탑에서 공기와 접촉시킴으로서 암모니아를 탈기시켜 폐수를 처리하고, 탈기된 암모니아 가스는 암모니아 흡수탑에서 인산과 접촉해 액상비료로서 적합한 인산암모늄을 생산하는 공정이다. 암모니아 탈기탑에서 질소폐수 제거목표에 적합한 최적운전조건은 pH 10.5~11, 송풍량 14 Nm3/min이며, 암모니아 흡수탑에서는 pH를 6 이하로 유지해야함을 알 수 있었다. 또한, 설비 운영 시 경제성을 분석하기 위해 처리용량(10, 100, 300, 500, 1000 m3/d)에 따라 생성되는 인산암모늄(액상비료)을 전량 판매할 경우 순현가법(경제성 분석방법)을 통해 경제성을 분석하였다. 그 결과 액상비료의 가격을 1,000 원/L으로 판매할 시, 처리용량이 100 m3/d 이상인 설비에 대해 NPV값이 모두 0보다 크므로 경제성이 있는 것으로 분석되었다. 또한, 암모니아 탈기 공정에서 사용한 알칼리로 인한 알칼리 보충효과와 탈기를 거친 후 개선된 수질로 인해 후단공정인 생물학적 처리조에 사용되는 약품비를 감소시켜주는 효과가 있을 것으로 여겨 이익을 산정하였고, 이에 따른 경제성을 분석하여 적합한 처리용량을 도출하였다. 그 결과 500 m3/d의 설비일 때, 별도의 알칼리 보충이 필요 없었다. 반면에 1000 m3/d 용량. 즉, 암모니아 스트리퍼/스크러버 설비를 통해 폐수를 전량 처리할 경우, 처리과정에서 높아진 pH를 다시 낮춰야하는 별도의 노력이 필요하므로 경제성이 떨어지는 것으로 판단되었다. 따라서 경제성을 고려한 적절한 암모니아 스트리퍼/스크러버 설비의 처리용량은 500 m3/d인 것으로 판단되었다. 본 연구를 통해 암모니아 스트리퍼/스크러버 시스템의 최적운전조건은 암모니아 탈기탑에서 pH 10.5~11, 암모니아 흡수탑에서는 pH 6 이하유지, 송풍량은 14 Nm3/min이다. 그리고 경제성을 고려하여 설비를 운전하기 위해서는 처리용량이 100 m3/d 이상인 설비에서 생성되는 액상비료를 1,000 원/L 이상으로 판매해야하며, 후단 공정인 생물학적 처리조의 약품비를 고려한 결과 가장 적합한 설비의 처리용량은 500 m3/d 이었다.| ABSTRACT Optimal operation factors and economic evaluation of stripper/scrubber system for ammonia recovery

Park, pyung hwa Department of Civil Engineering The Graduate School Hanyang University, 2012

Most domestic Nitrogen Waste Water Treatment had been focused on Nitrification/Denitrification. However, Nitrification/Denitrification process includes some problems in terms of cost and treatment stability. Some developed countries are implementing physical/chemical methods when treating Nitrogen Waste Water. The most common method of physical/chemical treatment is Ammonia Stripping. But the method has not been implemented in domestic researches due to operational difficulties and high cost. Therefore, this study will find the optimum operational factors and economical efficiency by installing the Stripper/Scrubber System at ‘J Company‘, which generates dense Nitrogen Waste Water. An Ammonia Stripper/Scrubber is a one-step process that contains pH control tank, Ammonia striper, Ammonia scrubbing, liquid-fertilizer storage. The optimum operational acidity for Ammonia Stripper and Scrubber are pH 10.5~11, and pH lower than 6, respectively. Additionally, the optimum air flow rate for Ammonia Stripper is 14 Nm3/min. Moreover, in order to analyze the economical efficiency during operation, NPV method was used according to treatment capacities (10, 100, 300, 500, 1000 m3/d). As a result, the NPV was above 0, meaning that the Stripper/Scrubber System is efficient enough for operation when selling the fertilizer at 1000 \/L, and operation capacity is higher than 100 m3/d. Additionally, an analysis was conducted to find out the most economically efficient operation capacity, since it was likely that the Alkali Supplementation and the biological treatment process will save chemical expense. According to the analysis, additional Alkali was not necessary until the operation capacity reached 500 m3/d. Exceptionally when the operation capacity is at 1000 m3/d, economic efficiency turned out to be low, due to the neccesary process of lowering acidity, which increases during the treatment process. Therefore, the most economically efficient operation capacity of the Ammonia Stripper/Scrubber is 500 m3/d. This thesis concludes the research with the optimum operation acidity of pH 10.5~11 for Ammonia Stripper, pH under 6 for Ammonia Scrubber and an air flow rate of 14 Nm3/min. Moreover, the liquid-fertilizer produced from Ammonia Stripper/Scrubber System of capacity greater than 100 m3/d must sell higher than 1000 \/L, and considering the chemical expense, the most optimum capacity of the Ammonia Stripper/Scrubber System is 500 m3/d.; ABSTRACT Optimal operation factors and economic evaluation of stripper/scrubber system for ammonia recovery

Park, pyung hwa Department of Civil Engineering The Graduate School Hanyang University, 2012

Most domestic Nitrogen Waste Water Treatment had been focused on Nitrification/Denitrification. However, Nitrification/Denitrification process includes some problems in terms of cost and treatment stability. Some developed countries are implementing physical/chemical methods when treating Nitrogen Waste Water. The most common method of physical/chemical treatment is Ammonia Stripping. But the method has not been implemented in domestic researches due to operational difficulties and high cost. Therefore, this study will find the optimum operational factors and economical efficiency by installing the Stripper/Scrubber System at ‘J Company‘, which generates dense Nitrogen Waste Water. An Ammonia Stripper/Scrubber is a one-step process that contains pH control tank, Ammonia striper, Ammonia scrubbing, liquid-fertilizer storage. The optimum operational acidity for Ammonia Stripper and Scrubber are pH 10.5~11, and pH lower than 6, respectively. Additionally, the optimum air flow rate for Ammonia Stripper is 14 Nm3/min. Moreover, in order to analyze the economical efficiency during operation, NPV method was used according to treatment capacities (10, 100, 300, 500, 1000 m3/d). As a result, the NPV was above 0, meaning that the Stripper/Scrubber System is efficient enough for operation when selling the fertilizer at 1000 \/L, and operation capacity is higher than 100 m3/d. Additionally, an analysis was conducted to find out the most economically efficient operation capacity, since it was likely that the Alkali Supplementation and the biological treatment process will save chemical expense. According to the analysis, additional Alkali was not necessary until the operation capacity reached 500 m3/d. Exceptionally when the operation capacity is at 1000 m3/d, economic efficiency turned out to be low, due to the neccesary process of lowering acidity, which increases during the treatment process. Therefore, the most economically efficient operation capacity of the Ammonia Stripper/Scrubber is 500 m3/d. This thesis concludes the research with the optimum operation acidity of pH 10.5~11 for Ammonia Stripper, pH under 6 for Ammonia Scrubber and an air flow rate of 14 Nm3/min. Moreover, the liquid-fertilizer produced from Ammonia Stripper/Scrubber System of capacity greater than 100 m3/d must sell higher than 1000 \/L, and considering the chemical expense, the most optimum capacity of the Ammonia Stripper/Scrubber System is 500 m3/d.