Portela J R, López J, Nebot E, Martínez de la Ossa E
Department of Chemical Engineering, Food Technology and Environmental Technologies, Faculty of Sciences, University of Cádiz, 11510 Puerto Real, Cádiz, Spain.
J Hazard Mater. 2001 Nov 16;88(1):95-106. doi: 10.1016/s0304-3894(01)00295-3.
Cutting oils are emulsionable fluids widely used in metalworking processes. Their composition is normally oil, water, and additives (fatty acids, surfactants, biocides, etc.) generating a toxic waste after a long use. Generally, it is a waste too dilute to be incinerated and it is difficult to treat biologically. Other conventional treatment methods currently used are not satisfactory from the environmental point of view. Wet air oxidation (WAO) and supercritical water oxidation (SCWO) are two forms of hydrothermal oxidation that have been proved to be effective processes to treat a wide variety of industrial wastes, but hardly tested for oily wastes. In the case of refractory wastes, WAO process is not efficient enough due to the moderate temperatures used. SCWO is a more powerful process since operating temperatures are usually around 600 degrees C, but the use of severe conditions leads to major disadvantages in the commercialization of the technology. In order to enhance WAO and SCWO efficiency at mild conditions, the use of free radical promoters has been studied in this work. Both normal and promoted hydrothermal oxidation have been tested to treat cutting oil wastes in a continuous flow system operating at 300-500 degrees C. Hydrogen peroxide has been used both as a source of oxygen and as a source of free radicals by introducing it into the reactor with or without previous thermal decomposition, respectively. Organic material is easily oxidized in both cases, obtaining more than 90% TOC reduction in less than 10s at 500 degrees C. At lower temperatures, the use of promoters clearly enhances the oxidation process. Activation energies have been estimated for normal and promoted oxidation processes.
切削油是可乳化的流体，广泛应用于金属加工过程。其成分通常为油、水和添加剂（脂肪酸、表面活性剂、杀菌剂等），长期使用后会产生有毒废物。一般来说，这种废物过于稀释，无法焚烧，且难以进行生物处理。目前使用的其他传统处理方法从环境角度来看并不令人满意。湿式空气氧化（WAO）和超临界水氧化（SCWO）是两种水热氧化形式，已被证明是处理各种工业废物的有效方法，但很少用于处理含油废物。对于难处理的废物，由于使用的温度适中，WAO工艺效率不够高。SCWO是一种更强大的工艺，因为操作温度通常在600摄氏度左右，但使用苛刻条件导致该技术商业化存在重大弊端。为了在温和条件下提高WAO和SCWO的效率，本研究探讨了自由基促进剂的使用。在300 - 500摄氏度的连续流动系统中，对普通水热氧化和促进水热氧化处理切削油废物进行了测试。过氧化氢分别在有或没有预先热分解的情况下引入反应器，既作为氧气源又作为自由基源。在这两种情况下，有机物质都很容易被氧化，在500摄氏度下不到10秒内总有机碳（TOC）减少超过90%。在较低温度下，促进剂的使用明显增强了氧化过程。已估算出普通氧化和促进氧化过程的活化能。
