Sludge stripping process and system

#1. Field of the Invention

#This invention relates generally to the processing of sludges, and more specifically to apparatuses and methods for removing VOCs from sludges.

#2. Description of the Prior Art

#FIG. 1A is a diagram showing the sludge processing system and the process for removing VOCs from the sludge as indicated by the flow arrows of the sludge through the system;

#FIG. 1B is a schematic section view of a steam stripper;

#FIG. 1C is a schematic section view of a distillation tower;

#As shown in FIG. 1 the sludge processing system 10 receives influent sludge 12 into mixing tanks 14 as shown by arrows. Water 18 may be added as needed in order to provide a more homogenous mixture having lower viscosity and greater flowability. Mixed sludge 23 leaves the mixing tanks 14 and enters sludge filters 27. Filtered sludge 32 leaves the filters 27 and enters the sludge stripper 36. Here the VOCs are removed in the form of VOC vapor 39. The devolatilized sludge 41 leaves the stripper 36 and either receives at least one chemical additive 43 or simply enters the sludge dewaterer 45. As shown, devolatilized solids 50 and liquids 52 leave the dewaterer. It is to be understood that the sludge 12, 23, 32, 41 is carried in conventional conduits 53 between the elements of the system.

#Prior to implementing the method, sludges are tested to determine whether and to what extent VOCs need to be removed there from. When the sludge 12 has been determined to have high levels of VOCs including the hazardous volatile compound, benzene, for example, the process of the instant invention may be utilized to remove the VOCs including benzene. As a first step of the process the sludge is placed in mixing tanks 14. A typical percentage of solid to liquid in the influent sludge 12 is approximately 50% solid and 50% liquid. In the mixing tank 14, the sludge is blended. Water may be added to provide a more homogenous and a lower viscosity sludge. Sludge 12 and water or another nonvolatile liquid are mixed or circulated for a short period of time. When the mixed sludge 23 is ready to leave the mixer tanks, the mixture may comprise 25% solids.

#The mixing step of the process serves several functions. Specifically, it causes the sludge mixture 23 to be more homogenous and flowable. As such, the mixture is more pumpable. Generally, the mixing process particalizes the solids, thus making them smaller for better contact with the stripping agent that they will encounter downstream.