Wet oxidation unit

Maintenance and operation of single-stage continuous powdered activated carbon system, 10 gal/min wet-oxidation unit, solid disposal, groundwater pumping, neutralization, and effluent discharge. 

In the construction of the wet oxidation unit, several areas of safety were considered. Of utmost importance was that of personal safety. Since this type of operation demands the use of high pressures and temperatures, operator contact with the high pressure vessels had to be limited. To accommodate this criterion, a barrier was constructed to shield the operator from any unforeseen releases from the reactor. This barrier was constructed from 1/4 inch steel and is desig ied in a manner that will fully contain any releases. This barrier is also equipped with two explosion vents to direct the force of any explosions away from the main walls and into a safe area. To further maximize personnel safety, all operator assisted controls are mounted on the outside of the unit. 

Zimpro. (ZimproPassavantEnvironmen-Ud Systems] Wet oxidation unit high pressure pump. 

Pipe-in-pipe heat exchangers made of four different alloys were tested in a wet oxidation unit for sewage sludge over a period of 1600 h under the following operating conditions. 

Nickel-based alloys of the Hastelloy group (alloy C-4, NiMol6Crl6Ti, 2.4610, alloy C-276, NiMol6Crl5W, 2.4819) and Incond 625 (NiCr22Mo9Nb, 2.4856) have proven resistant to chloride concentrations of approx. 1000 mg/1 and temperatures of approx. 573 K (300 C) in wet oxidation units for sewage sludge and waste water. 

In the U.S., the Takahax process has been used in combination with a wet oxidation Hiro-hax unit (Type A), where the thiosulfate and thiocyanate ammonium salts dissolved in the bleed stream are oxidized to fertilizer grade ammonium sulfate at high temperature (480°-535 F), and pressure (1,000-1,280 psig). In Japan, both wet oxidation units (Type A), and sulfur production units (Type D), are frequently selected, the choice depending primarily on the feed gas composition. 

Of the methods in common use, the two wet oxidation methods offer the best possibilities for further development. The photo-oxidation method in particular is well suited to automatic analysis. In the version of the total organic carbon method published by Collins and Williams [30] the effluent from the quartz photolysis coil could as easily be diverted to the nitrate analysis unit if inorganic nitrogen were also measured, organic nitrogen could become a routine automatic method. 

The capital costs associated with wet oxidation depend on several factors such as capacity of the system, oxygen demand of the wastewater, the properties of the waste to be treated, and the materials of construction of the system. Operating costs of the system are a function of the capacity of the unit, and the external energy requirements. (D16657Y, p. 8.88). 

There is not too much argument about analysis methods of the collected particulate material. While a few workers continue to use wet oxidation methods, it is acknowledged that these methods are neither as sensitive nor as accurate as the various dry combustion methods. Most of the more recent work has been done with one or another of the commercially available carbon analyzers (2). However, a few laboratories still use units assembled before the advent of suitable commercial xmits (3). All of these units, commercial or home-built, oxidize the organic carbon to carbon dioxide at high temperatures and measure this carbon dioxide usually by nondispersive infrared gas analysis (4) or by thermal conductivity. The results of the various methods seem completely comparable (5). 

If none of the disposal options above can be practiced, then wet or dry incineration are the only alternatives. Wet oxidation with air under pressure at 300-350°C, the Zimmerman process, yields liquid effluent containing a much reduced volume of easily settled ash [62]. Dry incineration in multiple hearth units uses much of the heat generated by combustion to complete the... 

As an example, I will use the determinations of DOC and DON, partly because the discussions are very recent and partly because they are very familiar to me. The question of the accuracy of measurements of DOC in seawater has been disputed at least since the publications of Putter [62] and Krogh [63] the early work has been reviewed at length in an earher pubhcation [64]. While a variety of wet oxidation methods [65] were proposed for marine samples, the use of persulfate [35] provided the first real approach to a standard method. Persulfate oxidation, however, hke all purely chemical oxidations, was a batch process, and not easily automated. A number of workers proposed photo oxidation using ultraviolet (UV) hght [66-70], and automated analytical systems which produced data almost in real time were soon constructed [71-73]. Commercial units soon appeared, but many of the units in the field were jerry-built, constructed out of parts scavenged from discarded autoanalyzers formerly used for nutrient analysis. 

The takeout zone where the product is moved out of the oil by a conveyor. The product is still hot in that zone and continues to cook. Its surface is covered with oil and has a wet appearance. As the product cools, the residual water vapor condenses, creating a pressure difference that pulls the oil from the surface into the pores and leaves the surface almost dry. Handling of the product at the takeout zone influences its moisture, texture, flavor, color, and especially oil content. To increase oil uptake, additional oil can be sprayed on the hot product, to be absorbed as the product cools. On the contrary, if low oil content is desired the product has to be maintained at temperature as it leaves the oil bath and the surface oil can be removed by a stream of hot gas. Some of the early commercial processes utilized a stream of hot air to reduce surface oil, but caused rapid oxidation and decrease of product shelf life. To avoid oxidation, units developed later use dry steam in conjunction with an oxygen-free chamber [3]. Centrifugal force is also used in some operations to reduce oil content of the products. 

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