The solidification process involves adding portland cement, fly ash, lime, and other solidifying reagents to the waste. There are two solidification processing trains, each providing



Figure 10

Process flow diagram.

Ui •fei. vi one-half of the total processing capacity. The sequence of activities in the solidification process is described below.

1. Reagent and Solids Feed

Solidification reagents are conducted from elevated hoppers and combined with waste solids in proportions to ensure appropriate blends. The combination is mixed to achieve a homogeneous, dry batch, then held awaiting addition of liquid waste.

2. Liquid-Solids Mixing

In the liquid-solids mixer, the liquid wastes are combined with the dry solids and mixed as necessary for the cement/pozzolanic reactions to occur. The liquid-solids mixers are sized for 50% void space to provide thorough mixing and initial solidification.

3. Curing Reaction

The curing reaction occurs in curing processors. Feed is introduced into the curing processor from the liquid-solids mixer by a screw conveyor; additives may be used to supplement the reactions.

The processor provides for agitation of the reactants during the curing and assists in the discharge of the solidified mass when the cure is complete. The curing processor discharges by a screw conveyor located at its base that subsequently feeds the lump breaker. The 10 curing processors are each sized to hold a batch that represents approximately 16 hr of normal processing flow. The design allows for up to 72 hr of curing time in the processor for each batch at normal production capacity.

4. Post-Solidification Drying

The solidified material that exits the curing processor is a relatively dry solid with a free moisture content of approximately 5-10% by weight. To further dry the solid to a sufficiently low free moisture content for pneumatic conveyance, the product is fed into a rotary dryer, if needed. The solid material passes through a lump breaker to provide a free-flowing and reduced particle size mixture before entering the two separate rotary dryers. The two rotary dryers are consistent with the dual trains used elsewhere throughout the process. The solid material flows through the rotary dryer to bring the free moisture content of the dried solid to within the desired range needed for pneumatic conveyance. The drying occurs in a nitrogen-enriched atmosphere.

5. Final Sizing

The dry solid that exits the rotary dryer passes through a final size-reduction lump breaker to provide a finely divided, free-flowing material that can be conveyed efficiently in a pneumatic conveyance system. The waste product has reached its final form and is conveyed to the solidified material storage building.

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