Energy Usage Optimization And Process Design Of The Phenols-ammonia Wastewater Treatment Processes

Fixed-bed gasification process and lignite upgrading process are known as the typical sources of high-concentration phenols-ammonia wastewater. The complicated components within those water make biochemical treatment extremely difficult. To get rid of the wastes and to make the biochemical treatment viable, the phenols-ammonia wastewater treatment processes(APWT) are widely implemented technology. Albeit the APWTs can be more economical with the funds from the recovered ammonia and phenols, the considerable utilities consumptions drive its variable cost stayed in a high level. In this article, heat exchanger networks analysis and heat integration of columns have been applied to invent low energy consumption processes(LECP) based on the APWT of South China University of Technology.First thing first, based on former researches, a full process modeling and flowsheet of the current-applied APWT from SCUT is completed via Aspen Plus, which becomes the foundation of further energy analysis and new process development. The result revealed by the energy network analysis notes that the current process is not optimized and can costs 22.9% less. To save more, the conceptual design of two LECPs are accomplished with the application of heat integration of columns within solvent recovery system. The LECPs, pressure-adjusted process(PA) and pressure-reduced process(PR), can achieve 22% less energy cost. Furthermore, the implement of low temperature exhaust heat brings a 40% heat recovery on two LECPs based new processes, HRPA and HRPR.To exemplify the advantages of the process, techno-economic analysis is used. Compare with current process, both LECPs have economical advantage and the PR has the lowest total annual cost of those three processes, as 27.3 million CNY/a. Meanwhile, in the scenario of process modification, the 0.93 years of pay-back period of PR is also less than that of PA which is 1.53 years. Although PR has a lower pay-back period, it is not acceptable considering the availability of the columns of current process. Thus PA is recommended in process modification. Last but not least, the techno-economic analysis of low temperature exhaust heat recovery processes is calculated based on Organic Rankine Cycle(ORC). As an example, HRPR with ORC can save 1.52 million CNY/a and has a total annual cost of 26.63 million CNY/a. The techno-economic analysis indicates that the pressure-reduced processes, PR and HRPR, cost much less than current process and can be considered while new factory design.