Mixed landfill and pond coal combustion byproducts (CCBs) and related techniques

Abstract

Methods and systems for reclaiming materials from a mixed waste landfill containing coal combustion byproducts (CCBs) are disclosed. The methods and systems can be used to reclaim CCBs from ponds or dry landfills by obtaining mixed waste, crushing the mixed waste to form crushed mixed waste, drying the crushed mixed waste to form dried crushed mixed waste, and combining the dried crushed mixed waste with other compounds to form a blend. The blends can then be incorporated into a cement material, which may be used to form concrete.

Claims

1. A method of reclaiming additives for cement from a mixed waste landfill, the method comprising: obtaining mixed waste from a landfill, wherein the mixed waste comprises coal combustion byproducts (CCBs) from a coal-fired power plant; crushing the mixed waste to form crushed mixed waste; drying the crushed mixed waste to form dried crushed mixed waste; and combining the dried crushed mixed waste with other compounds to form a blend.

2. The method of claim 1, wherein the landfill is a pond or a dry landfill.

3. The method of claim 1, wherein the mixed waste contains at least one of fly ash, bottom ash, scrubber residue, pyrites, and coal.

4. The method of claim 1, wherein the mixed waste has a moisture content between 10% and 20%.

5. The method of claim 1, wherein the mixed waste is crushed to a size of 50-325 mesh.

6. The method of claim 1, wherein the crushed mixed waste is dried at a temperature of at least 350° F.

7. The method of claim 1, wherein the crushed mixed waste is dried until a moisture content of less than 2% is achieved.

8. The method of claim 1 further comprising storing the dried crushed mixed waste in a silo.

9. The method of claim 1, wherein the dried crushed mixed waste is combined with class C fly ash, a high-activity natural pozzolan, class F fly ash, and dried class C bottom ash ground to a mean particle size of 15-20 μm to form the blend.

10. The method of claim 1 further comprising adding calcium sulfate to form the blend.

11. The method of claim 1 further comprising incorporating the blend into a cement material.

12. The method of claim 1, wherein the blend includes at least one of calcium sulfate and calcium sulfite.

13. A method of reclaiming additives for cement from a mixed waste landfill, the method comprising: obtaining mixed waste from a landfill; crushing the mixed waste to form crushed mixed waste; drying the crushed mixed waste to form dried crushed mixed waste; exposing the crushed mixed waste to a desorber to capture compounds that are volatized during drying; and combining the dried crushed mixed waste with other compounds to form a blend.

14. The method of claim 13 further comprising incorporating the blend into a cement material.

15. The method of claim 13, wherein the blend includes at least one of calcium sulfate and calcium sulfite.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an exemplary method of reclaiming additives for cement from a CCB mixed waste landfill or coal-fired power station ash ponds, in accordance with some embodiments of the present disclosure.

(2) These and other features of the present embodiments will be understood better by reading the following detailed description, taken together with the figures herein described. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Furthermore, as will be appreciated in light of this disclosure, the accompanying drawings are not intended to be drawn to scale or to limit the described embodiments to the specific configurations shown.

DETAILED DESCRIPTION

(3) The present disclosure addresses issues relating to mining deposits of mixed coal combustion byproducts (fly ash), flue gas scrubber residue (FGD), bottom ash (DBFS), pyrites from coal crushing (mill rejects), and other co-mingled wastes. Moreover, the present disclosure includes sufficient processing techniques to make a consistent Grade 100 or 120 reactive pozzolan, which can be used as a 50% replacement of OPC material in cement and concrete making.

(4) FIG. 1 illustrates an example method 100 of reclaiming additives for cement from CCB mixed waste landfills or coal-fired power station ash ponds, in accordance with embodiments of the present disclosure. As discussed in detail below, method 100 advantageously allows the materials present in these landfills or ponds to be reclaimed and used at a reactivity level much higher than just ASTM C 618 fly ash.

(5) As shown in FIG. 1, method 100 includes obtaining mixed waste from a landfill (Block 102). In some embodiments, the mixed waste may obtained from a coal-fired power plant. The mixed waste may be obtained from a wet or dry landfill. For example, in some embodiments, the mixed waste is obtained from a pond or a dry landfill. In these and other embodiments, the mixed waste may contain fly ash, bottom ash, scrubber residue, pyrites, and/or coal. The mixed waste may, in some embodiments, have a moisture content of between 5% and 30%, such as between 10% and 20%, or approximately 12%, in some embodiments.

(6) Table 1 shown below identifies the contents of a particular example mixed waste site located in Texas. At this landfill, which is a coal fired power plant/mixed waste landfill, five core samples were obtained. The moisture content of each core was between 9%-18%, with an average of approximately 12% moisture. The contents of the core samples were analyzed to determine the compounds present and the detected compounds are listed below in Table 1.

(7) TABLE-US-00001 TABLE 1 Measured Contents of Core Landfill Samples Compound Mg Al.sub.2O.sub.3 SiO.sub.2 SO.sub.3 K.sub.2O CaO Fe.sub.2O.sub.3 Na.sub.2O LOI Total Sum Avg (%) 2.25 14.48 46.35 11.55 0.91 15.92 6.96 0.20 0.50 98.61 67.79

(8) Based on the analysis performed on the core samples, fly ash, bottom ash, scrubber, pyrites, and coal were believed to be present in the mixed waste landfill. It should be understood that the contents of this sample landfill can be processed according to method 100 shown in FIG. 1.

(9) Method 100 continues with crushing the obtained mixed waste (Block 104). If desired, two large roll-crushers may be used to crush the obtained mixed waste. Depending on the site location, remote crushers can be used and the resultant crushed materials can then be moved to a separate location. The mixed waste can be crushed to any desired size. For example, in some embodiments, the mixed waste can be crushed to a size of between 50 and 325 mesh.

(10) Method 100 continues with drying the crushed mixed waste (Block 106). Any suitable type of dryer may be used to dry the crushed mixed waste. For example, in some embodiments, the crushed mixed waste may be passively dried by ambient temperature whereas, in other embodiments, the crushed mixed waste may be dried by a commercial drying system, such as a Holo-Flite® dryer (HFD) (available from Metso, Joy Denver, or BCR Environmental Therma-Flite). If a commercial drying system is used, the crushed mixed waste may be dried at a temperature of at least 200° F., 250° F., 300° F., 350° F., or 400° F., in some embodiments. In these and other embodiments, the drying system may be set to a temperature at or below 400° F. Using a temperature of approximately 400° F. or less may allow the majority of the sulfite present to remain as sulfite and not be converted to gypsum, which can be preferable for the final product to avoid negative impacts on the resulting concrete. In some embodiments, the crushed mixed waste may be dried until a moisture content of less than 10%, less than 8%, less than 5%, less than 2%, or less than 1% is achieved.

(11) In select embodiments, a desorber system attachment may be used on the drying system to capture the heat given off from coal or other fuel that travels through the dryer. If present, a desorber system attachment can capture compounds that are volatized at or below 400° F. (i.e., the operating temperature of the HFD), thereby helping to reduce the demand on natural gas firing, which is commonly used to fire the HFD. As will be appreciated, using a desorber system attachment may allow the user to capture additional heat generated by the drying system to aid in drying the crushed mixed waste.

(12) Method 100 continues with optionally storing the dried and crushed mixed waste (Block 108). If storing is desired, a silo or other structure may be used to store the dried and crushed mixed waste in a stable and dry environment.

(13) Method 100 continues with combining the dried and crushed mixed waste with other components to form a blend (Block 110). In some embodiments, the dried and crushed mixed waste may be combined with class C fly ash, high-activity natural pozzolan (e.g., MicraSil® manufactured by Imerys), class F fly ash, and/or dried class C bottom ash ground to a mean particle size of 15-20 μm. For clarity, the chemistry of typical class C bottom ash is as shown in below in Table 2.

(14) TABLE-US-00002 TABLE 2 Composition of Typical Class C Bottom Ash Mg Al.sub.2O.sub.3 SiO.sub.2 SO.sub.3 K.sub.2O CaO Fe.sub.2O.sub.3 Total Sum LMS C BA (%) 3.61 24.72 31.22 1.11 0.31 16.49 5.73 83.19 61.67

(15) In some embodiments, either class F fly ash or high-activity natural pozzolan may be used to form the blend with the dried and crushed mixed waste, class C fly ash, and/or dried class C bottom ash ground to a mean particle size of 15-20 μm. Depending on the blending technique used, each of the components added to the blend may be stored in neighboring silos to facilitate processing.

(16) In select embodiments, calcium sulfate may also be incorporated into the blend. Incorporating calcium sulfate may be desirable in situations where calcium sulfite in the mixed waste is lower than preferred. Any suitable ratios of components may be used to form the blend. For example, the following blend samples (Blends A-D) were created and tested.

(17) TABLE-US-00003 TABLE 3 Composition of Blend A Sum % in % Material MgO Al.sub.2O.sub.3 SiO.sub.2 SO.sub.3 K.sub.2O CaO Fe2O.sub.3 Total (Al/Si/Fe) Mix Sum Landfill 2.05 14.51 48.24 10.77 0.87 14.16 7.47 98.07 70.22 42.0 29.5 Micrasil 0.5 13.7 71 0.6 1.2 0.7 1 88.7 85.7 58.0 49.7 Final Chem 1.15 14.04 61.44 4.87 1.06 6.35 3.72 92.6 79.2 100.0 79.2

(18) Blend A was created by mixing the quantities of “Micrasil” and “Landfill” illustrated in Table 3, each having the chemical composition shown. Blend A was subjected to ASTM C989 Slag Testing (with 50% control cement and 50% slag, 172 mL of water, and cube flow of 106) and exhibited the results shown below in Table 4.

(19) TABLE-US-00004 TABLE 4 Compressive Strength Testing of Blend A Compressive Strength (PSI) 1 Day 7 Days 28 Days 56 Days 2240 6080 7620 10380

(20) TABLE-US-00005 TABLE 5 Composition of Blend B Sum % in % Material MgO Al.sub.2O.sub.3 SiO.sub.2 SO.sub.3 K.sub.2O CaO Fe.sub.2O.sub.3 Total (Al/Si/Fe) Mix Sum Landfill 2.05 14.51 48.24 10.77 0.87 14.16 7.47 98.07 70.22 42.0 29.5 F Ash 2.32 16.31 59.28 0.62 1.28 7.04 9.26 96.11 84.85 58.0 49.2 Final Chem 2.21 15.55 54.64 4.88 1.11 10.03 8.51 96.9 78.7 100.0 78.7

(21) Blend B was created by mixing the quantities of “F Ash” and “Landfill” shown in Table 5, each having the chemical composition shown. Blend B was subjected to ASTM C989 Slag Testing (with 50% control cement and 50% slag, 178 mL of water, and cube flow of 107) and exhibited the results shown below in Table 6.

(22) TABLE-US-00006 TABLE 6 Compressive Strength Testing of Blend B Compressive Strength (PSI) 1 Day 3 Days 7 Days 14 Days 28 Days 56 Days 1810 3880 5260 5570 6610 8640

(23) TABLE-US-00007 TABLE 7 Composition of Blend C Sum % in % Material MgO Al.sub.2O.sub.3 SiO.sub.2 SO.sub.3 K.sub.2O CaO Fe.sub.2O.sub.3 Total (Al/Si/Fe) Mix Sum Landfill 2.05 14.51 48.24 10.77 0.87 14.16 7.47 98.07 70.22 40 28.1 F Ash 2.32 16.31 59.28 0.62 1.28 7.04 9.26 96.11 84.85 40 33.9 Class C Ash 5.92 16.55 35.49 2.06 0.49 27.13 6.17 93.81 58.21 20 11.6 Final Chem 2.93 15.64 50.11 4.97 0.96 13.91 7.93 96.4 73.7 100.0 73.7

(24) Blend C was created by mixing the quantities of “F Ash,” “Class C Ash,” and “Landfill” shown in Table 7, each having the chemical composition shown. Blend C was subjected to ASTM C989 Slag Testing (with 50% control cement and 50% slag, 178 mL of water, and cube flow of 1119901) and exhibited the results shown below in Table 8.

(25) TABLE-US-00008 TABLE 8 Compressive Strength Testing of Blend C Compressive Strength (PSI) 1 Day 3 Days 7 Days 14 Days 28 Days 56 Days 1810 3920 4405 5405 6265 8007

(26) TABLE-US-00009 TABLE 9 Composition of Blend D Sum % in % Material MgO Al.sub.2O.sub.3 SiO.sub.2 SO.sub.3 K.sub.2O CaO Fe.sub.2O.sub.3 Total (Al/Si/Fe) Mix Sum Landfill 2.05 14.51 48.24 10.77 0.87 14.16 7.47 98.07 70.22 40 28.1 Micrasil 0.5 13.7 71 0.6 1.2 0.7 1 88.7 85.7 40 34.3 Class C Ash 5.92 16.55 35.49 2.06 0.49 27.13 6.17 93.81 58.21 20 11.6 Final Chem 2.93 15.64 50.11 4.97 0.96 13.91 7.93 96.4 73.7 100.0 74.0

(27) Blend D was created by mixing the quantities of “Class C Ash,” “Micrasil,” and “Landfill” illustrated in Table 9, each having the chemical composition shown. Blend D was subjected to ASTM C989 Slag Testing (with 50% control cement and 50% slag, 195 mL of water, and cube flow of 108) and exhibited the results shown below in Table 10.

(28) TABLE-US-00010 TABLE 10 Compressive Strength Testing of Blend D Compressive Strength (PSI) 1 Day 7 Days 28 Days 56 Days 870 2980 6620 8540

(29) Each of Blends A-D produced a Grade 100 to 120 reactive slag material, as tested using ASTM C 989 testing protocol.

(30) Upon consideration of the subject disclosure, one skilled in the art will appreciate that using about 50 wt % of the roller mill-processed/landfill material, which has no organics in it but may have up to 15-20 wt % sulfur products, the feed rate can be adjusted to mix these materials to obtain a product that has around 5 wt % sulfur oxide (e.g., usually sulfite). It was discovered that the sulfite helped the reactivity of the blended pozzolans reactivity.

(31) In some embodiments, the contents of the blend can be monitored, for example, by x-ray diffraction (XRD) analysis. Example XRD analysis systems that may be used include those produced by Bruker, Panalytical, and Fisons. Monitoring the blend's components (specifically its non-carbon components) can allow for adjustments to be made. For example, in some embodiments, monitoring of the components may prompt the addition of other ingredients from silos that have been ground-down already. In these and other embodiments an electrical tie-in to a controller may be used, as needed, to make a pozzolan that meets all the desired chemical requirements for high-performance concrete.

(32) In a particular example embodiment, a reclamation site may be configured as follows: A first silo containing Class C fly ash from any source; A second silo containing landfill material crushed with roll crusher, then dried (ignited coal) with Holo-Flite® auger; A third silo containing class C bottom ash (e.g., from limestone—obtained from a power station—or other source) crushed to 50-300 mesh with roll crusher; A fourth silo containing raw class F fly ash, MicraSil® high-activity natural pozzolan, or other High Sum material (i.e., material high in silica, iron, or alumina content, for example, Class F fly ash or microsilica), dried and crushed to 50-200 mesh; and A fifth silo containing gypsum (as a fine powder, as purchased).

(33) In an example embodiment, the materials from the reclamation site may be batched and weighted into a mill for processing. In particular, the materials may be batched by weight based on their chemistry and then interground together in reactors. In some embodiments, variable flow feeders can be used at the bottom of each silo to control each mineral feed instantaneously based on the processed/landfill material chemistry. The resulting blend may be a superior pozzolan. An exemplary blend was created containing the compounds identified below in Table 11.

(34) TABLE-US-00011 TABLE 11 Compounds of Exemplary Blend Sum % in % Material MgO Al.sub.2O.sub.3 SiO.sub.2 SO.sub.3 K.sub.2O CaO Fe.sub.2O.sub.3 Total (Al/Si/Fe) Mix Sum Landfill 2.05 14.51 48.24 10.77 0.87 14.16 7.47 98.07 70.22 34.0 23.9 F Ash 2.32 16.31 59.28 0.62 1.28 7.04 9.26 96.11 84.85 32.0 27.2 C Bottom Ash 3.61 24.72 31.22 1.11 0.31 16.49 5.73 83.19 61.67 8.0 4.9 C Fly Ash 5.92 16.55 35.49 2.06 0.49 27.13 6.17 93.81 58.21 25.0 14.6 Micrasil/Perlite Ore 0.5 13.7 71 0.6 1.2 0.7 1 88.7 85.7 0.0 0.0 Gypsum/FDG Sluge 0.2 0.62 0.88 44.6 0.2 31.5 0.2 78.2 1.7 1.0 0.0 Final Chem 3.21 16.27 46.75 4.91 0.85 51.51 7.51 95.0 70.5 100.0

(35) The exemplary blend shown in Table 11 was incorporated into concrete and tested. Comparative data for cement containing the exemplary blend and control cement are shown below in Tables 11 and 12.

(36) The Exemplary Cement and Control Cement were subjected to ASTM C989 Slag Testing (with 50% control cement and 50% slag). The Exemplary (landfill) Blend was tested with 178 mL of water and cube flow of 107 and the Control Cement was tested with 232 mL of water and cube flow of 108. The compressive strength testing results of the Exemplary Blend and the Control Cement are shown in Tables 12 and 13.

(37) TABLE-US-00012 TABLE 12 Testing Data for Control Cement 1 Day 7 Days 28 Days 56 Days Compressive Strength (PSI) 2250 3590 4740 5460

(38) TABLE-US-00013 TABLE 13 Testing Data for Concrete with Exemplary Blend 1 Day 3 Days 7 Days 14 Days 28 Days 56 Days Compressive Strength (PSI) 1809 3877 5255 5567 6612 8637 Strength Activity Index % of Control 80% 146% 139% 158%

(39) As shown in Tables 12 and 13, the cement containing the exemplary blend of reclaimed CCB material exhibited greater compressive strength than the control cement. The testing data suggest that the CCB materials reclaimed according to the presently disclosed methods may improve cement properties when used as an additive.

(40) As will be appreciated, the blends produced according to the disclosed methods can be incorporated into cement using any standard technique. For example, the blends may be incorporated into ready-mix or other types of cement. In these and other embodiments, the disclosed blends may be used with cement to make concrete, as typically manufactured by ready-mix companies, architectural concrete companies (e.g., Oldcastle), and pre-cast companies (e.g., Forterra).

(41) The performance of the finished pozzolan (i.e., blend formed from reclaimed CCBs) may, in some embodiments, be capable of attaining much higher strengths than just the raw fly ash (if it could be separated) or any ground-down bottom ash ever could accomplish by itself, while also balancing the sulfur content to allow the material to meet ASTM requirements.

(42) Without wishing to be bound by theory, it is believed that once crushed/processed in the proprietary mill, any pyrites present in the CCB s are not yet fully oxidized, therefore, there are no issues with pyrite staining in the concrete. If desired, further processing according to known techniques may be used to increase the reactivity of the pozzolan blend.

(43) The presently disclosed methods may offer numerous advantages over previous approaches. For example, any organics (e.g., wood, plastics, etc.) present in the landfill may be combusted in the drying process. Thus, the reclaimed landfill material can be “sterilized” from components that would keep the finished pozzolan from being used to make a high-performance concrete.

(44) Additionally, the disclosed methods may also allow for the removal of all contaminants through a novel drying/coal burnout application and a subsequent novel addition of certain mineral additives based on the landfill/ash pond chemistry driving their addition rate. This can produce an environmentally friendly, high-performing pozzolanic material that allows all landfills and/or ash ponds in the U.S. (and elsewhere) to be processed economically, as well as provide an environmentally safe end-use (e.g., concrete) for these materials.

(45) The present disclosure importantly provides reclamation techniques to utilize coal combustion byproducts (CCBs), which remain after massive amounts of coal were burned to make the electricity required to move the U.S. to become a world leader in energy production. Specifically, the present disclosure provides safe and economical ways to reverse a huge environmental issue derived from the residue of burning the different coals (sub bituminous, bituminous, and/or lignite) that all produced large volumes of waste ash byproducts (fly ash, bottom ash) and gas cleaning residues (scrubber wastes) as well as other wastes that ended up in landfills. The materials reclaimed by the disclosed techniques can be mixed in with ash byproducts to produce a superior pozzolan for cementitious materials.

(46) The foregoing description of example embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise forms disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the present disclosure be limited not by this detailed description. Future-filed applications claiming priority to this application may claim the disclosed subject matter in a different manner and generally may include any set of one or more limitations as variously disclosed or otherwise demonstrated herein.