Sludge streams

The reaction is mn for several hours at temperatures typically below 100°C under a pressure of carbon monoxide to minimise formamide decomposition (73). Conversions of a-hydroxyisobutyramide are near 65% with selectivities to methyl a-hydroxyisobutyrate and formamide in excess of 99%. It is this step that is responsible for the elimination of the acid sludge stream characteristic of the conventional H2SO4—ACH processes. Because methyl formate, and not methanol, is used as the methylating agent, formamide is the co-product instead of ammonium sulfate. Formamide can be dehydrated to recover HCN for recycle to ACH generation. 

In a DAF thickening process, air is added at pressures in excess of atmospheric pressure (2.1 to 4.9 kg/cm1 2 3 4 30 to 70psig) either to the incoming sludge stream or to a separate liquid stream. When the pressure is reduced and turbulence is created, air in excess of that required for saturation at atmospheric pressure leaves the solution as very small bubbles of 50 to 100 pm in diameter. The bubbles adhere to the suspended particles or become enmeshed in the solids matrix. As the average density of the solids-air aggregate is less than that of water, the agglomerate floats to the surface. The floated solids build to a depth of several inches at the water surface. Skimmers continuously remove the float.58... 

Separation process of liquid tank waste and production of supernatant and sludge streams. 

The process no longer produces this sludge stream. 

Counter-current flow in which the feed and sludge streams move in opposite directions. 

Cross-current flow in which the direction of the feed stream is perpendicular to the sludge stream... 

The oil and gas industry produces much waste material, such as scrap metal, human waste, unspent chemicals, oily sludges and radiation. All of the incoming streams to a facility such as a production platform end up somewhere, and only few of the outgoing streams are useful product. It is one of the responsibilities of the engineer to try to limit the amount of incoming material which will finally become waste material. 

PermeOx is also used to improve the bioremediation of soils contaminated with creosote or kerosene (see Bioremediation (Supplement)), to deodori2e sewage sludges and wastewater (see Odormodification), and to dechloriaate wastewater and effluents. A special formulation of calcium peroxide, made by FMC and sold ia the United States under the trademark Trap2ene, is used for removing metal ions from acidic waste streams such as coal ash leachate and acid mine drainage (see Wastes, industrial). 

Process water streams from vinyl chloride manufacture are typically steam-stripped to remove volatile organics, neutralized, and then treated in an activated sludge system to remove any nonvolatile organics. If fluidized-bed oxychlorination is used, the process wastewater may also contain suspended catalyst fines and dissolved metals. The former can easily be removed by sedimentation, and the latter by precipitation. Depending on the specific catalyst formulation and outfall limitations, tertiary treatment may be needed to reduce dissolved metals to acceptable levels. 

Dissolved Air Flotation. Dissolved air flotation (DAF) is used to separate suspended soflds and oil and grease from aqueous streams and to concentrate or thicken sludges. Air bubbles carry or float these materials to the surface where they can be removed. The air bubbles are formed by pressurizing either the influent wastewater or a portion of the effluent in the presence of air. When the pressurized stream enters the flotation tank which is at atmospheric pressure, the dissolved air comes out of solution as tiny, microscopic bubbles. Dissolved air flotation is used in many wastewater treatment systems, but in the United States it is perhaps best known with respect to hazardous waste because it is associated with the Hsted waste, K048, DAF flotation soflds from petroleum refining wastewaters. Of course, the process itself is not what is hazardous, but the materials it helps to remove from refining wastewaters. 

In addition to many varied apphcations in the chemical industiy, the reactotherm is widelv used to process waste sludges which must be dried in order to lanc fill the sohd components. In many of these cases, the solvents are valuable components of the waste stream and can be recovered and recycled. 

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