Modar process

Swallow, K.C. Killilea, W.R. Malinowski, K.C Staszak, C.N. The Modar process for the destruction of hazardous organic wastes—field test of a pilot-scale unit. Waste Manag. (Amsterdam, Netherlands) 1989, 9 (1), 19-26. 

The industrial research efforts on coffee decaffeination, spice extraction, and flavors concentration are, to a great extent, shrouded by the cloak of proprietary security, but the investigations of the use of supercritical fluids to treat various waste streams is reasonably well publicized. Most familiar, perhaps, is the supercritical waste water detoxification process developed by Modar Inc. This is potentially attractive for detoxifying refractory chemicals such as polychlorinated biphenyls, dioxin, and other toxic materials (Anon., 1982 Modell, 1982). In the Modar process, the toxic chemicals are homogeneously reacted with oxygen in supercritical water, the solvent for the organics and the oxygen. The main feature of the process is a chemical reaction discussed in more detail in chapter 11. 

In order to solve the problem caused by precipitates in reactors, a two-zone technique involving supercritical and subcritical chambers was exploited. A flow-chart of an SCWO process (MODAR process) featuring a two-zone reactor is shown in Fig. 21 [66]. In the upper zone, which is for sew at 600°C, the wastes are decomposed and the products are neutralized. In the lower zone (subcritical), in which the temperature of water is 200°C, the precipitates which formed in the upper zone are dissolved. 

Fig. 21. Flow diagram of SCWO process ( MODAR process ) featuring two-zone reactor [66].

Work on SCWO process development was performed in the early 1970s and in the 1980s, many of the developments were performed under private contract to industrial or federal agencies. The technology for waste treatment and generation of energy from waste or low grade materials was commercialized by Modar (Natick, Massachusetts). 

The demonstration unit was later transported to the CECOS faciHty at Niagara Falls, New York. In tests performed in 1985, approximately 3400 L of a mixed waste containing 2-chlorophenol [95-57-8] nitrobenzene [98-95-3] and 1,1,2-trichloroethane [79-00-5] were processed over 145 operating hours 2-propanol was used as a supplemental fuel the temperature was maintained at 615 to 635°C. Another 95-h test was conducted on a PCB containing transformer waste. Very high destmction efficiencies were achieved for all compounds studied (17). A later bench-scale study, conducted at Smith Kline and French Laboratories in conjunction with Modar (18), showed that simulated chemical and biological wastes, a fermentation broth, and extreme thermophilic bacteria were all completely destroyed within detection limits. 

SC WO [supercritical water oxidation] A generic name for processes which destroy organic wastes in water by oxidation under supercritical conditions. The first such process was MODAR, invented in 1980. Since then, several other companies have introduced competing processes. 

Thomson B, Hong GT, Swallow KC, Killilea WR. The MODAR supercritical oxidation process. In Freeman HM, ed. Innovative Hazardous Waste Treatment Technology Series, 1 31 42. 

Experiments in our tubular SCWO reactors are described in [1], A model for SCWO in a Modar vessel reactor was published recently [2]. This paper will describe our present work on a model for tubular flow SCWO reactors. Some numerical simulation results will demonstrate the use of the model to understand time dependent temperature instabilities. The paper also presents first results to derive process parameters from operational process data. 

Building on the results of these initial studies, Modell began adding oxygen in order to explore the effect of the supercritical water environment on oxidation reactions of organic species. In 1980, he started MODAR as the first company established to develop and commercialize the SCWO process. Many of the characteristic attributes that are commonly associated with SCWO were first discovered and described by personnel at MODAR, and they established an... 

Fig. 3.7. Process flow diagram of supercritical water oxidation process. (Modar, Inc., Houston, TX courtesy EPA.)...

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