Method to improve the characteristics of ash from municipal solid waste combustors
In a combustion facility, a portion of the bottom ash (BA) is mixed with substantially all of the fly ash (FA) as necessary to obtain a stabilized material that prevents toxic metals solubility and achieves a desired TCLP extraction pH value, preferably in the range of 8-11. The actual quantities of BA to be mixed with FA will vary depending upon various factors, so embodiments of the present invention include testing the ash to determine the desired distribution to achieve sufficient alkalinity to prevent the leaching of toxic metals in landfills. Because the resulting ash has a desired alkalinity by design, minimal additional alkali reagent amendment is necessary for safe disposal of the waste ash. The remaining BA may be recycled or deposited in a landfill without additional processing. Valuable materials in the waste ash may also be more easily recovered and reused.
1. A method for processing waste from municipal solid combustion for disposal, the waste comprising bottom ash and fly ash, the method comprising the steps of:
separately collecting the BA and the FA;
evaluating the bottom ash and the FA to determine a portion of the bottom ash to be added to the fly ash to produce a combined ash having a set characteristic;
combining the FA and the desired portion of the BA to form the CA.
2. The method of claim 1 further comprising a step of testing the combined ash, wherein the testing is performed using a toxicity characteristic leachate procedure (TCLP).
3. The method of claim 2 , further comprising a step of treating the combined ash depending on results from the step of testing the combined ash.
4. The method of claim 1 wherein the set characteristic is a TCLP extraction pH substantially in a range of 8 to 11.
5. The method of claim 4 wherein the step of evaluating the bottom ash and fly ash comprises the steps of forming a bottom ash titration curve, forming a fly ash titration curve, and analyzing the bottom ash and fly ash titration curves to identify the portion of the bottom ash to produce the CA the set characteristic.
6. The method of claim 1 further comprising a step of disposing a remaining portion of the bottom ash representing an amount of the bottom ash remaining after combining of the desired portion of the bottom ash in the combined ash.
7. The method of claim 1 further comprising a step of recycling a remaining portion of the bottom ash representing an amount of the bottom ash remaining after combining of the desired portion of the bottom ash in the combined ash.
8. The method of claim 1 further comprising the step of separating sifting from the bottom ash prior to the step of combining the bottom ash with the desired portion of the bottom ash.
9. The method of claim 1 , wherein the portion is substantially a third of the bottom ash.
10. The method of claim 1 , wherein the fly ash comprises flue ash and boiler fly ash.
11. The method of claim 1 , wherein the fly ash comprises flue ash and the bottom ash comprises boiler fly ash.
12. The method of claim 1 , further comprising the steps of repeating the step of evaluating the bottom ash and fly ash, and updating the portion of the bottom ash.
13. A method according to claim 1 , wherein the step of combining the fly ash and the portion of the bottom ash to form the combined ash is done on a batch basis.
14. The method of claim 1 , wherein the bottom ash is split into a portion and the remaining portion by a mechanical splitter and conveyor which can be operated continuously.
15. A solid waste disposal method comprising the steps of:
combusting the solid waste;
collecting fly ash and bottom ash produced during the step of combusting the solid waste;
evaluating the bottom ash and the fly ash to determine a desired portion of the bottom ash to be added to the fly ash to produce a combined ash having a set characteristic;
combining the fly ash and the desired portion of the bottom ash to form the combined ash; and
disposing of the combined ash.
16. The method of claim 15 further comprising a step of disposing a remaining portion of the bottom ash representing an amount of the bottom ash remaining after combining of the portion of the bottom ash in the combined ash.
17. The method of claim 15 further comprising the step of separating sifting from the bottom ash prior to the step of combining the fly ash with the portion of the bottom ash.
18. The method of claim 15 wherein the set characteristic is a pH substantially in a range of 8 to 11.