METHOD OF MAKING WATERPROOF MAGNESIUM OXYCHLORIDE REFRACTORY BRICK BY FLY ASH FROM MUNICIPAL SOLID WASTE INCINERATION

Abstract

The invention discloses a method of making waterproof magnesium oxychloride refractory brick by fly ash from municipal solid waste incineration. The method comprises the following steps: (1) sulfur-containing compound and water are mixed into the fly ash and stirred evenly to make stabilized slurry, the heavy metals are stabilized and CaO is turned to Ca(OH).sub.2 during this process. (2) The aqueous solution of MgO and MgCl.sub.2 is added into the stabilized slurry to make magnesium oxychloride slurry by being stirred evenly. (3) The magnesium oxychloride slurry is cured to make magnesium oxychloride gel, (4) and the magnesium oxychloride aggregate is prepared by crushing the magnesium oxychloride gel. (5) The blended slurry is prepared by mixing metastable material, alkali metal hydroxide, Na.sub.2SiO.sub.3, magnesium oxychloride aggregate and water, (6) after being stirred, molded and cured, the waterproof magnesium oxychloride refractory brick is obtained. The waterproof magnesium oxychloride refractory brick made by this invention combines two materials, the geopolymer gel and the magnesium oxychloride gel, which possess different properties of fire resistance and water resistance. It is confirmed that the coexistence of geopolymer gel and magnesium oxychloride gel achieves the multi-stage solidification and stabilization of heavy metals and improving the water resistance of magnesium oxychloride refractory brick.

Claims

1. A Method of making waterproof magnesium oxychloride refractory brick by fly ash from municipal solid waste incineration includes the following steps: (1) Sulfur-containing compound and water are mixed into the fly ash and stirred evenly to make stabilized slurry, the heavy metals are stabilized and CaO is turned to Ca(OH).sub.2 during this process; (2) The aqueous solution of MgO and MgCl.sub.2 is added into the stabilized slurry which is obtained in the step (1), after being stirred evenly, magnesium oxychloride slurry is prepared; (3) The magnesium oxychloride obtained in step (2) is cured to make magnesium oxychloride gel; (4) The magnesium oxychloride gel in the step (3) is crushed to obtain magnesium oxychloride aggregate; (5) The blended slurry is prepared by mixing metastable material, alkali metal hydroxide, Na.sub.2SiO.sub.3, water and magnesium oxychloride aggregate obtained in step (4); (6) The waterproof magnesium oxychloride refractory brick is obtained by curing and shaping the blended slurry obtained in step (5).

2. According to claim 1 in this method, the characteristics are that the sulfur-containing compound in claim 1 is inorganic sulfide or organic sulfide.

3. According to claim 2 in this method, the characteristics are that the inorganic sulfide is Na.sub.2S.

4. According to claim 1 in this method, the characteristics are that The dosage of the sulfur-containing compound is 6%9% of fly ash dry mass; The dosage of the water is 40%-50% of fly ash dry mass.

5. According to claim 1 in this method, the characteristics are that The temperature for stirring and homogenization is 40-50 C.; The time of stirring and homogenization is 15-30 minute.

6. According to claim 1 in this method, the characteristics of steps (2) are that the dosage of MgO is 35%-45% of fly ash dry mass; In the aqueous solution of the MgCl.sub.2, the dosage of MgCl.sub.2 is 13%-16% of fly ash dry mass, the dosage of water is 45%-55% of fly ash dry mass.

7. According to claim 1 in this method, the characteristics of steps (2) are that The temperature for stirring and homogenization is 40-50 C.; The time of stirring and homogenization is 5-10 minute.

8. According to claim 1 in this method, the characteristics of steps (3) are that the condition of curing is ventilated, rainproof and 20-25 C.

9. According to claim 8 in this method, the characteristics of steps (3) are that The time of curing in mold is 2-4 days, and the time of the mold-opening curing is 3-5 days after curing in mold.

10. According to claim 1 in this method, the characteristics of steps (4) is that the magnesium oxychloride gel is crushed to less than 4 meshes (particle size<4.75 mm).

11. According to claim 1 in this method, the characteristics of steps (5) is that the mass ratio of the magnesium oxychloride aggregate, metastable material, alkali metal hydroxide, Na.sub.2SiO.sub.3 and the water is 100:(40-55):5:1.5:(25-35).

12. According to claim 1 in this method, the characteristics of steps (5) is that The alkali metal hydroxides are NaOH or KOH; The metastable material is fly ash, blast furnace slag or metakaolin.

13. According to claim 1 in this method, the characteristics of steps (5) is that The particle size of the metastable material is less than 75 m; The time of stirring and homogenization is 5 to 10 minutes.

14. According to claim 1 in this method, the characteristics of steps (6) are that the curing in mold is in the condition of 70-80 C. and <20% relative humidity; The time of curing in mold is 1 day; The mold-opening curing is in the condition of 50-60 C. and <20% relative humidity; The time of mold-opening curing is 6-8 day.

15. The waterproof magnesium oxychloride refractory brick, which is made by the method said in claim 1.

16. According to claim 15, the characteristics are that the mechanical strength of waterproof magnesium oxychloride refractory brick is not lower than 18 MPa; The fire resistance temperature is higher than 1450-1550 C.; The water-resistance softening coefficient is not lower than 0.80.

17. The waterproof magnesium oxychloride refractory brick said in the claim 15 can be utilized as following 1)-6) 1) Waterproof brick; 2) Refractory bricks; 3) Thermal insulation interior wall construction; 4) Thermal insulation walls for outdoor or hydraulic structures; 5) Interior firewalls construction; 6) Firewalls for outdoor or hydraulic structures.

Description

DESCRIPTION OF DRAWINGS

[0056] FIG. 1 is a flowchart of the invention for making waterproof magnesium oxychloride refractory brick by fly ash from municipal solid waste incineration.

SPECIFIC IMPLEMENTATION METHODS

[0057] The experimental methods used in the following embodiments are conventional methods without special description.

[0058] Materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special description.

[0059] The mechanical strength of waterproof magnesia oxychloride refractory bricks prepared in the following embodiments is determined by the method disclosed in the reference standard No. GB2542. The softening coefficient is an expression parameter of water resistance, and the expression is K=f/F. K: the softening coefficient of materials; f: the unconfined compressive strength of materials under water saturation, MPa; F: the unconfined compressive strength of materials under dry condition, MPa.

Embodiment 1. Making Waterproof Magnesia Oxychloride Refractory Bricks from Municipal Solid Waste Incineration Fly Ash

[0060] The fly ash samples were collected from a municipal solid waste incineration plant in Daxing District, Beijing. The contents of heavy metals in the samples and the leaching amount are shown in Table 1. The leaching method refers to Level Oscillation Method for Toxicity Leaching of Solid Waste (HJ557-2010), and the limit standard refers to Surface Water Environmental Quality Standard (GB3838-2002) V water body standard. Table 1 shows that the leaching amount of Pb is seriously over the standard.

TABLE-US-00001 TABLE 1 Heavy Metals Content and Leaching Amount in Fly Ash of a Waste Incineration Plant in Daxing, Beijing Heavy metal Zn Pb Cu Cr Cd Ni Hg As Content/mg/kg 1070.56 491.13 173.1 62.25 30.11 19.45 76.87 4.85 Leaching 1.26 5.68 0.07 0.04 0.001 0.02 0.005 0.01 quantity/mg/L Water standard 2 0.1 1 0.1 0.01 0.001 0.1 of class V

[0061] According to the flow chart shown in FIG. 1, waterproof magnesia oxychloride refractory bricks are made from municipal solid waste incineration fly ash. The specific steps are as follows:

[0062] (1) Heavy Metal Stabilization:

[0063] The Na.sub.2S equal to 6% of the fly ash (dry ash) mass and 40% reclaimed water heated to 45 C. are added into fly ash and stirred for 20 minutes at 45 C. for heavy metal stabilization and CaO turning to Ca(OH).sub.2, to obtain the stabilized slurry.

[0064] (2) Magnesium Oxychloride Pulping:

[0065] 85# lightly burnt magnesia is added into the stabilized slurry from step (1), and the amount of MgO is increased to 40% of the fly ash mass (dry material), the mixture is stirred until homogeneous. 15% industrial grade magnesium chloride of fly ash (dry material) mass and the 45% reclaimed water are used for MgCl.sub.2 solution preparation, after adding the MgO, the MgCl.sub.2 solution is added into the stabilized slurry, after 5 min mixing at 45 C., the magnesium oxychloride slurry is prepared.

[0066] (3) Curing and Growth:

[0067] The magnesium oxychloride paste from step (2) is put in mold and cured for 3 days in rainproof and well ventilated environment at 22 C. outdoor temperature. Then the mold is opened and followed with a four-day maintenance to get the magnesium oxychloride gelatin. The compressive strength of magnesium oxychloride gel is 42.2 MPa, 45.7 MPa and 58.5 MPa.

[0068] (4) Crushing:

[0069] The magnesium oxychloride gel in step (3) is crushed below to 4 mesh (particle size <4.75 mm) to obtain magnesium oxychloride aggregate.

[0070] (5) The Metastable Materials is Mixed for Pulping:

[0071] The I grade fly ash, NaOH, Na.sub.2SiO.sub.3, magnesium oxychloride aggregate from step (4) and the reclaimed water are mixed under 25 C. for pulping, the quality ratio of magnesium oxychloride aggregate:fly ash:NaOH:Na.sub.2SiO.sub.3:reclaimed water=100:45:5:1.5:30. The mixture is stirred for 5 min to prepare the mixed slurry, and then poured into the mold immediately for curing.

[0072] (6) Curing and Molding

[0073] The mixed slurry from step (5) is cured for 1 day in the environment with 20% of RH at 75 C., then open the mold and the bricks are cured for 6 days in the environment with 20% of RH at 55 C.

[0074] After the molding, the strength of firebrick generally can reach 18.5 MPa, 22.6 MPa and 24.5 MPa, the tolerance temperature can reach 1450 C., softening coefficient of water resistance can reach 0.81, 0.82 and 0.85, and the heavy metal leaching quantity can meet III grade water quality requirements (Table 2). The firebrick can be used for the construction of insulation wall, fire wall, fire partition wall of outdoor or hydraulic structure, etc.

TABLE-US-00002 TABLE 2 Heavy metal leaching amount of fly ash resource- based brick products in Daxing, Beijing Heavy metal Zn Pb Cu Cr Cd Ni Hg As Leaching 0.25 0.041 0.446 0.04 0.004 0.008 N.D. N.D. quantity/mg/L Water standard 1 0.05 1 0.05 0.005 0.0001 0.05 of class III

[0075] Implementation of Example 2, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

[0076] Fly ash samples are from a waste incinerator in Xingtai, Heibei province, and the heavy metal content and heavy metal leaching amount of samples are shown in Table 3. Leaching method refers to the Horizontal Oscillation Method for Solid Waste Toxicity Leaching (HJ557-2010), the limited standards refers to V class standard in the Standard of Surface Water Environmental Quality (GB3838-2002). Table 7 shows that the leaching amount of Pb and Zn exceed the standard.

TABLE-US-00003 TABLE 3 Heavy metals content and heavy metal leaching amount in fly ash of a waste incineration plant in Xingtai, Heibei province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Content/mg/kg 1588.54 423.13 175.1 100.45 15.11 27.05 24.57 1.85 Leaching 2.16 2.68 0.04 0.04 0.001 0.001 N.D. 0.011 quantity/mg/L Water standard 2 0.1 1 0.1 0.01 0.001 0.1 of class V

[0077] The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in FIG. 1, the specific steps are as follows:

[0078] (1) Heavy Metal Stabilization:

[0079] The Na.sub.2S equal to 9% of the fly ash (dry ash) mass and 40% reclaimed water heated to 45 C. are added into fly ash and stirred for 20 minutes at 45 C. for heavy metal stabilization and CaO turning to Ca(OH).sub.2, to obtain the stabilized slurry.

[0080] (2) Magnesium Oxychloride Pulping:

[0081] 85# lightly burnt magnesia is added into the stabilized slurry from step (1), and the amount of MgO is increased to 40% of the fly ash mass (dry material), the mixture is stirred until homogeneous. 13% industrial grade magnesium chloride of fly ash (dry material) mass and the 45% reclaimed water are used for MgCl.sub.2 solution preparation, after adding the MgO, the MgCl.sub.2 solution is added into the stabilized slurry, after 5 min mixing at 45 , the magnesium oxychloride slurry is prepared.

[0082] (3) Curing and Growth:

[0083] The magnesium oxychloride paste from step (2) is put in mold and cured for 3 days in rainproof and well ventilated environment at 20 C. outdoor temperature. Then the mold is opened and followed with a four-day maintenance to get the magnesium oxychloride gelatin. The compressive strength of magnesium oxychloride gel is 56.2 MPa, 41.3 MPa and 45.5 MPa.

[0084] (4) Crushing:

[0085] The magnesium oxychloride gel in step (3) is crushed below to 4 mesh (particle size <4.75 mm) to obtain magnesium oxychloride aggregate.

[0086] (5) The Metastable Materials is Mixed for Pulping:

[0087] The II grade fly ash, NaOH, Na.sub.2SiO.sub.3, magnesium oxychloride aggregate from step (4) and the reclaimed water are mixed under 25 C. for pulping, the quality ratio of magnesium oxychloride aggregate:fly ash:NaOH:Na.sub.2SiO.sub.3:reclaimed water=100:45:5:1.5:30. The mixture is stirred for 5 min to prepare the mixed slurry, and then poured into the mold immediately for curing.

[0088] (6) Curing and Molding

[0089] The mixed slurry from step (5) is cured for 1 day in the environment with 20% of RH at 75 C., then open the mold and the bricks are cured for 6 days in the environment with 20% of RH at 60 C.

[0090] After the molding, the strength of firebrick generally can reach 19.6 MPa, 26.6 MPa and 27.5 MPa, the tolerance temperature can reach 1450 C., softening coefficient of water resistance can reach 0.80, 0.83 and 0.84, and the heavy metal leaching quantity can meet III grade water quality requirements (Table 4). The firebrick can be used for the construction of insulation wall, fire wall, fire partition wall of outdoor or hydraulic structure, etc.

TABLE-US-00004 TABLE 4 Heavy metal leaching amount of fly ash resource- based brick products in Xingtai, Hebei Province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Leaching 0.51 0.045 0.345 0.04 0.003 N.D. N.D. N.D. quantity/mg/L Water standard 1 0.05 1 0.05 0.005 0.0001 0.05 of class III

[0091] Implementation of Example 3, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

[0092] Fly ash samples are from a waste incinerator in Linqu, Shandong province, and the heavy metal content and heavy metal leaching amount of samples are shown in Table 5. Leaching method refers to the Horizontal Oscillation Method for Solid Waste Toxicity Leaching (HJ557-2010), the limited standards refers to V class standard in the Standard of Surface Water Environmental Quality (GB3838-2002). Table 5 shows that the leaching amount of Pb and Zn exceed the standard.

TABLE-US-00005 TABLE 5 Heavy metals content and heavy metal leaching amount in fly ash of a waste incineration plant in Linqu, Shandong Province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Content/mg/kg 879.06 691.13 103.17 97.25 55.01 9.08 1.57 2.56 Leaching 1.06 6.01 0.02 0.14 0.001 0.01 N.D. 0.01 quantity/mg/L Water standard 2 0.1 1 0.1 0.01 0.001 0.1 of class V

[0093] The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in FIG. 1, the specific steps are as follows:

[0094] (1) Heavy Metal Stabilization:

[0095] The Na.sub.2S equal to 7% of the fly ash (dry ash) mass and 50% reclaimed water heated to 45 C. are added into fly ash and stirred for 20 minutes at 45 C. for heavy metal stabilization and CaO turning to Ca(OH).sub.2, to obtain the stabilized slurry.

[0096] (2) Magnesium Oxychloride Pulping:

[0097] 85# lightly burnt magnesia is added into the stabilized slurry from step (1), and the amount of MgO is increased to 40% of the fly ash mass (dry material), the mixture is stirred until homogeneous. 15% industrial grade magnesium chloride of fly ash (dry material) mass and the 55% reclaimed water are used for MgCl.sub.2 solution preparation, after adding the MgO, the MgCl.sub.2 solution is added into the stabilized slurry, after 5 min mixing at 45 C., the magnesium oxychloride slurry is prepared.

[0098] (3) Curing and Growth:

[0099] The magnesium oxychloride paste from step (2) is put in mold and cured for 3 days in rainproof and well ventilated environment at 25 C. outdoor temperature. Then the mold is opened and followed with a four-day maintenance to get the magnesium oxychloride gelatin. The compressive strength of magnesium oxychloride gel is 37.6 MPa, 52.4 MPa and 49.5 MPa.

[0100] (4) Crushing:

[0101] The magnesium oxychloride gel in step (3) is crushed below to 4 mesh (particle size <4.75 mm) to obtain magnesium oxychloride aggregate.

[0102] (5) The Metastable Materials is Mixed for Pulping:

[0103] The crushing blast furnace slag (under 200 mesh sieve), NaOH, Na.sub.2SiO.sub.3, magnesium oxychloride aggregate from step (4) and the reclaimed water are mixed under 25 for pulping, the quality ratio of magnesium oxychloride aggregate:crushing blast furnace slag:NaOH:Na.sub.2SiO.sub.3:reclaimed water=100:45:5:1.5:25. The mixture is stirred for 5 min to prepare the mixed slurry, and then poured into the mold immediately for curing.

[0104] (6) Curing and Molding

[0105] The mixed slurry from step (5) is cured for 1 day in the environment with 20% of RH at 70 C., then open the mold and the bricks are cured for 6 days in the environment with 20% of RH at 60 C.

[0106] After the molding, the strength of firebrick generally can reach 18.9 MPa, 26.5 MPa and 24.2 MPa, the tolerance temperature can reach 1500 C., softening coefficient of water resistance can reach 0.80, 0.81 and 0.83, and the heavy metal leaching quantity can meet III grade water quality requirements (Table 6). The firebrick can be used for the construction of insulation wall, fire wall, fire partition wall of outdoor or hydraulic structure, etc.

TABLE-US-00006 TABLE 6 Heavy metal leaching amount of fly ash resource- based brick products in Xingtai, Hebei Province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Leaching 0.21 0.015 0.657 N.D. 0.003 0.001 N.D. N.D. quantity/mg/L Water standard 1 0.05 1 0.05 0.005 0.0001 0.05 of class III

[0107] Implementation of Example 4, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

[0108] Fly ash samples are from a waste incinerator in Dehui, Jiling, and the heavy metal content and heavy metal leaching amount of samples are shown in Table 7. Leaching method refers to the Horizontal Oscillation Method for Solid Waste Toxicity Leaching (HJ557-2010), the limited standards refers to V class standard in the Standard of Surface Water Environmental Quality (GB3838-2002). Table 7 shows that the leaching amount of Pb, Zn and Cr exceed the standard.

TABLE-US-00007 TABLE 7 Heavy metals content and heavy metal leaching amount in fly ash of a waste incineration plant in Dehui, Jilin. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Content/mg/kg 1170.56 293.12 167.1 38.25 55.11 19.55 15.54 7.55 Leaching 2.26 2.48 0.04 0.02 0.011 0.01 N.D. 0.03 quantity/mg/L Water standard 2 0.1 1 0.1 0.01 0.001 0.1 of class V

[0109] The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in FIG. 1, the specific steps are as follows:

[0110] (1) Heavy Metal Stabilization:

[0111] The Na.sub.2S equal to 8% of the fly ash (dry ash) mass and 40% reclaimed water heated to 50 C. are added into fly ash and stirred for 20 minutes at 50 C. for heavy metal stabilization and CaO turning to Ca(OH).sub.2, to obtain the stabilized slurry.

[0112] (2) Magnesium Oxychloride Pulping:

[0113] 85# lightly burnt magnesia is added into the stabilized slurry from step (1), and the amount of MgO is increased to 40% of the fly ash mass (dry material), the mixture is stirred until homogeneous. 13% industrial grade magnesium chloride of fly ash (dry material) mass and the 45% reclaimed water are used for MgCl.sub.2 solution preparation, after adding the MgO, the MgCl.sub.2 solution is added into the stabilized slurry, after 5 min mixing at 50 C., the magnesium oxychloride slurry is prepared.

[0114] (3) Curing and Growth:

[0115] The magnesium oxychloride paste from step (2) is put in mold and cured for 3 days in rainproof and well ventilated environment at 22 C. outdoor temperature. Then the mold is opened and followed with a four-day maintenance to get the magnesium oxychloride gelatin. The compressive strength of magnesium oxychloride gel is 45.6 MPa, 41.2 MPa and 54.2 MPa.

[0116] (4) Crushing:

[0117] The magnesium oxychloride gel in step (3) is crushed below to 4 mesh (particle size <4.75 mm) to obtain magnesium oxychloride aggregate.

[0118] (5) The Metastable Materials is Mixed for Pulping:

[0119] The I grade fly ash, NaOH, Na.sub.2SiO.sub.3, magnesium oxychloride aggregate from step (4) and the reclaimed water are mixed under 25 C. for pulping, the quality ratio of magnesium oxychloride aggregate:fly ash:NaOH:Na.sub.2SiO.sub.3:reclaimed water=100:45:5:1.5:35. The mixture is stirred for 5 min to prepare the mixed slurry, and then poured into the mold immediately for curing.

[0120] (6) Curing and Molding

[0121] The mixed slurry from step (5) is cured for 1 day in the environment with 20% of RH at 75, then open the mold and the bricks are cured for 7 days in the environment with 20% of RH at 55.

[0122] After the molding, the strength of firebrick generally can reach 19.9 MPa, 25.5 MPa and 23.5 MPa, the tolerance temperature can reach 1450 C., softening coefficient of water resistance can reach 0.81, 0.81 and 0.82, and the heavy metal leaching quantity can meet III grade water quality requirements (Table 8). The firebrick can be used for the construction of insulation wall, fire wall, fire partition wall of outdoor or hydraulic structure, etc.

TABLE-US-00008 TABLE 8 Heavy metal leaching amount of fly ash resource- based brick products in Dehui, Jilin. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Leaching 0.57 0.045 0.25 0.004 0.002 N.D. N.D. 0.009 quantity/mg/L Water standard 1 0.05 1 0.05 0.005 0.0001 0.05 of class III

[0123] Implementation of Example 5, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

[0124] Fly ash samples are from a waste incinerator in Kaixian, Chongqing province, and the heavy metal content and heavy metal leaching amount of samples are shown in Table 9. Leaching method refers to the Horizontal Oscillation Method for Solid Waste Toxicity Leaching (HJ557-2010), the limited standards refers to V class standard in the Standard of Surface Water Environmental Quality (GB3838-2002). Table 7 shows that the leaching amount of Pb, Zn, Cd and Cr exceed the standard.

TABLE-US-00009 TABLE 9 Heavy metals content and heavy metal leaching amount in fly ash of a waste incineration plant in Kaixian, Chongqing Province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Content/mg/kg 951.25 490.16 203.1 24.25 12.11 11.45 6.87 N.D. Leaching 2.11 2.68 0.27 0.11 0.015 0.01 N.D. N.D. quantity/mg/L Water standard 2 0.1 1 0.1 0.01 0.001 0.1 of class V

[0125] The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in FIG. 1, the specific steps are as follows:

[0126] (1) Heavy Metal Stabilization:

[0127] The Na.sub.2S equal to 8% of the fly ash (dry ash) mass and 40% reclaimed water heated to 50 C. are added into fly ash and stirred for 20 minutes at 50 C. for heavy metal stabilization and CaO turning to Ca(OH).sub.2, to obtain the stabilized slurry.

[0128] (2) Magnesium Oxychloride Pulping:

[0129] 85# lightly burnt magnesia is added into the stabilized slurry from step (1), and the amount of MgO is increased to 40% of the fly ash mass (dry material), the mixture is stirred until homogeneous. 15% industrial grade magnesium chloride of fly ash (dry material) mass and the 55% reclaimed water are used for MgCl.sub.2 solution preparation, after adding the MgO, the MgCl.sub.2 solution is added into the stabilized slurry, after 5 min mixing at 50 C., the magnesium oxychloride slurry is prepared.

[0130] (3) Curing and Growth:

[0131] The magnesium oxychloride paste from step (2) is put in mold and cured for 3 days in rainproof and well ventilated environment at 20 C. outdoor temperature. Then the mold is opened and followed with a four-day maintenance to get the magnesium oxychloride gelatin. The compressive strength of magnesium oxychloride gel is 56.5 MPa, 42.2 MPa and 60.2 MPa.

[0132] (4) Crushing:

[0133] Break the magnesium oxychloride gel in step (3) below to 4 mesh (particle size <4.75 mm) to obtain magnesium oxychloride aggregate.

[0134] (5) The Metastable Materials is Mixed for Pulping:

[0135] The class II fly ash, NaOH, Na.sub.2SiO.sub.3, magnesium oxychloride aggregate from step (4) and the reclaimed water are mixed under 25 C. for pulping, the quality ratio of magnesium oxychloride aggregate:fly ash:NaOH:Na.sub.2SiO.sub.3:reclaimed water=100: 45:5:1.5:25. The mixture is stirred for 5 min to prepare the mixed slurry, and then poured into the mold immediately for curing.

[0136] (6) Curing and Molding

[0137] The mixed slurry from step (5) is cured for 1 day in the environment with 20% of RH at 75 C., then open the mold and the bricks are cured for 6 days in the environment with 20% of RH at 50 C.

[0138] After the molding, the strength of firebrick generally can reach 18.9 MPa, 19.5 MPa and 18.6 MPa, the tolerance temperature can reach 1450 C., softening coefficient of water resistance can reach 0.82, 0.82 and 0.83, and the heavy metal leaching quantity can meet III grade water quality requirements (Table 10). The firebrick can be used for the construction of insulation wall, fire wall, fire partition wall of outdoor or hydraulic structure, etc.

TABLE-US-00010 TABLE 10 Heavy metal leaching amount of fly ash resource-based brick products in Kaixian, Chongqing Province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Leaching 0.45 0.015 0.65 0.002 0.004 N.D. N.D. 0.015 quantity/mg/L Water standard 1 0.05 1 0.05 0.005 0.0001 0.05 of class III

[0139] Implementation of Example 6, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

[0140] Fly ash samples are from a waste incinerator in Dezhou, Shandong province, and the heavy metal content and heavy metal leaching amount of samples are shown in Table 11. Leaching method refers to the Horizontal Oscillation Method for Solid Waste Toxicity Leaching (HJ557-2010), the limited standards refers to V class standard in the Standard of Surface Water Environmental Quality (GB3838-2002). Table 11 shows that the leaching amount of Pb, Zn and Cd exceed the standard.

TABLE-US-00011 TABLE 11 Heavy metals content and heavy metal leaching amount in fly ash of a waste incineration plant in Dezhou, Shandong province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Content/mg/kg 980.56 501.51 203.15 18.54 24.11 11.45 14.37 10.53 Leaching 2.01 1.12 0.05 0.01 0.011 0.02 N.D. N.D. quantity/mg/L Water standard 2 0.1 1 0.1 0.01 0.001 0.1 of class V

[0141] The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in FIG. 1, the specific steps are as follows:

[0142] (1) Heavy Metal Stabilization:

[0143] The Na.sub.2S equal to 9% of the fly ash (dry ash) mass and 50% reclaimed water heated to 50 C. are added into fly ash and stirred for 20 minutes at 50 C. for heavy metal stabilization and CaO turning to Ca(OH).sub.2, to obtain the stabilized slurry.

[0144] (2) Magnesium Oxychloride Pulping:

[0145] 85# lightly burnt magnesia is added into the stabilized slurry from step (1), and the amount of MgO is increased to 40% of the fly ash mass (dry material), the mixture is stirred until homogeneous. 13% industrial grade magnesium chloride of fly ash (dry material) mass and the 50% reclaimed water are used for MgCl.sub.2 solution preparation, after adding the MgO, the MgCl.sub.2 solution is added into the stabilized slurry, after 5 min mixing at 50 , the magnesium oxychloride slurry is prepared.

[0146] (3) Curing and Growth:

[0147] The magnesium oxychloride paste from step (2) is put in mold and cured for 3 days in rainproof and well ventilated environment at 25 C. outdoor temperature. Then the mold is opened and followed with a four-day maintenance to get the magnesium oxychloride gelatin. The compressive strength of magnesium oxychloride gel is 45.6 MPa, 49.5 MPa and 45.6 MPa.

[0148] (4) Crushing:

[0149] Break the magnesium oxychloride gel in step (3) below to 4 mesh (particle size <4.75 mm) to obtain magnesium oxychloride aggregate.

[0150] (5) The Metastable Materials is Mixed for Pulping:

[0151] The class II fly ash, NaOH, Na.sub.2SiO.sub.3, magnesium oxychloride aggregate from step (4) and the reclaimed water are mixed under 25 C. for pulping, the quality ratio of magnesium oxychloride aggregate:fly ash:NaOH:Na.sub.2SiO.sub.3:reclaimed water=100:45:5:1.5:30. The mixture is stirred for 5 min to prepare the mixed slurry, and then poured into the mold immediately for curing.

[0152] (6) Curing and Molding

[0153] The mixed slurry from step (5) is cured for 1 day in the environment with 20% of RH at 70 C., then open the mold and the bricks are cured for 7 days in the environment with 20% of RH at 50 C.

[0154] After the molding, the strength of firebrick generally can reach 18.8 MPa, 19.6 MPa and 20.5 MP, the tolerance temperature can reach 1450 C., softening coefficient of water resistance can reach 0.82, 0.82 and 0.85, and the heavy metal leaching quantity can meet III grade water quality requirements (Table 12). The firebrick can be used for the construction of insulation wall, fire wall, fire partition wall of outdoor or hydraulic structure, etc.

TABLE-US-00012 TABLE 12 Heavy metal leaching amount of fly ash resource-based brick products in Dezhou, Shandong Province. Heavy metal Zn Pb Cu Cr Cd Ni Hg As Leaching 0.84 0.046 0.48 0.002 0.004 0.006 N.D. N.D. quantity/mg/L Water standard 1 0.05 1 0.05 0.005 0.0001 0.05 of class III