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 using fly ash from municipal solid waste incineration (MSWFA). The solidification and stabilization of heavy metals in MSWFA is achieved by the chemical action of a sulfur-containing compound and a physical wrapping of a geopolymer. The large amount of chloride ions in MSWFA is also reused in the manufacture of magnesium oxychloride refractory brick, which requires a high chlorine environment. This method, with the inclusion of the geopolymer, also produces refractory brick exhibiting improved water resistance relative to traditional magnesium oxychloride refractory brick, thereby allowing the improved magnesium oxychloride refractory brick to be used in a wider range of applications.

Claims

1. A method of making waterproof magnesium oxychloride refractory brick using fly ash from municipal solid waste incineration comprising the steps of: (1) mixing a sulfur-containing compound and water with the fly ash to form a slurry and stirring the slurry to obtain a stabilized slurry in which heavy metals are stabilized and CaO is converted to Ca(OH).sub.2, wherein the sulfur-containing compound is selected from the group consisting of inorganic sulfides, organic sulfides, and mixtures thereof; (2) adding MgO and an aqueous solution of MgCl.sub.2 into the stabilized slurry and stirring to obtain a magnesium oxychloride slurry; (3) curing the magnesium oxychloride slurry to obtain a magnesium oxychloride gel; (4) crushing the magnesium oxychloride gel to obtain a magnesium oxychloride aggregate; (5) preparing a blended slurry by mixing a metastable material, an alkali metal hydroxide, Na.sub.2SiO.sub.3, water, and the magnesium oxychloride aggregate; (6) shaping and curing the blended slurry to obtain a waterproof magnesium oxychloride refractory brick.

2. The method according to claim 1, wherein the sulfur-containing compound is Na.sub.2S.

3. The method according to claim 1, wherein the added amount of the sulfur-containing compound is 6%˜9% of fly ash dry mass; and the added amount of the water is 40%-50% of fly ash dry mass.

4. The method according to claim 1, wherein in step (1) the mixing is conducted at a temperature of 40-50° C. and continued for a period of 15-30 minutes.

5. The method according to claim 1, wherein in step (2), the added amount of MgO is 35%-45% of fly ash dry mass; wherein the added amount of MgCl.sub.2 in the aqueous solution of the MgCl.sub.2 is 13%-16% of fly ash dry mass, and further wherein the added amount of water is 45%-55% of fly ash dry mass.

6. The method according to claim 1, wherein in step (2), the stirring is conducted at a temperature of 40-50° C.; and continued for a period of 5-10 minutes.

7. The method according to claim 1, wherein in step (3), the curing is conducted by placing the magnesium oxychloride slurry in a mold and maintaining the mold in a ventilated enclosure and protected from rain dry conditions, at a curing temperature of 20-25° C.

8. The method according to claim 7, wherein in step (3), 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.

9. The method according to claim 1, wherein in step (4), the magnesium oxychloride gel is crushed to a particle size of less than 4 mesh (particle size<4.75 mm).

10. The method according to claim 1, wherein in step (5), the mass ratio of the magnesium oxychloride aggregate, metastable material, alkali metal hydroxide, Na.sub.2SiO.sub.3, and the water is within a range of 100:(40-55):5:1.5:(25-35).

11. The method according to claim 1, wherein in step (5), the alkali metal hydroxides are selected from the group consisting of NaOH, KOH, and mixtures thereof; and the metastable material is selected from the group consisting of grade 1 fly ash, grade 2 fly ash, blast furnace slag, metakaolin, and mixtures thereof.

12. The method according to claim 1, wherein in step (5), the particle size of the metastable material is less than 75 μm; and a mixing duration is 5 to 10 minutes.

13. The method according to claim 1, wherein in step (6), 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; and the time of mold-opening curing is 6-8 days.

Description

DESCRIPTION OF DRAWINGS

(1) The FIGURE is a flowchart of the invention for making waterproof magnesium oxychloride refractory brick using fly ash from municipal solid waste incineration.

SPECIFIC IMPLEMENTATION METHODS

(2) The experimental methods used in the following embodiments are conventional methods without special description.

(3) Materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special description.

(4) 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

(5) 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.

(6) 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

(7) According to the flow chart shown in the FIGURE, waterproof magnesia oxychloride refractory bricks are made from municipal solid waste incineration fly ash. The specific steps are as follows:

(8) (1) Heavy Metal Stabilization:

(9) 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.

(10) (2) Magnesium Oxychloride Pulping:

(11) 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.

(12) (3) Curing and Growth:

(13) 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.

(14) (4) Crushing:

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

(16) (5) The Metastable Materials is Mixed for Pulping:

(17) 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.

(18) (6) Curing and Molding

(19) 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.

(20) 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.

(21) 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

(22) Implementation of Example 2, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

(23) 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.

(24) 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

(25) The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in the FIGURE, the specific steps are as follows:

(26) (1) Heavy Metal Stabilization:

(27) 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.

(28) (2) Magnesium Oxychloride Pulping:

(29) 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° C., the magnesium oxychloride slurry is prepared.

(30) (3) Curing and Growth:

(31) 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.

(32) (4) Crushing:

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

(34) (5) The Metastable Materials is Mixed for Pulping:

(35) 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.

(36) (6) Curing and Molding

(37) 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.

(38) 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.

(39) 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

(40) Implementation of Example 3, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

(41) 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.

(42) 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

(43) The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in the FIGURE, the specific steps are as follows:

(44) (1) Heavy Metal Stabilization:

(45) 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.

(46) (2) Magnesium Oxychloride Pulping:

(47) 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.

(48) (3) Curing and Growth:

(49) 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.

(50) (4) Crushing:

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

(52) (5) The Metastable Materials is Mixed for Pulping:

(53) 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° C. 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.

(54) (6) Curing and Molding

(55) 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.

(56) 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.

(57) 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

(58) Implementation of Example 4, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

(59) 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.

(60) 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

(61) The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in the FIGURE, the specific steps are as follows:

(62) (1) Heavy Metal Stabilization:

(63) 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.

(64) (2) Magnesium Oxychloride Pulping:

(65) 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.

(66) (3) Curing and Growth:

(67) 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.

(68) (4) Crushing:

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

(70) (5) The Metastable Materials is Mixed for Pulping:

(71) 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.

(72) (6) Curing and Molding

(73) 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 7 days in the environment with 20% of RH at 55° C.

(74) 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.

(75) 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

(76) Implementation of Example 5, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

(77) 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.

(78) 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

(79) The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in the FIGURE, the specific steps are as follows:

(80) (1) Heavy Metal Stabilization:

(81) 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.

(82) (2) Magnesium Oxychloride Pulping:

(83) 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.

(84) (3) Curing and Growth:

(85) 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.

(86) (4) Crushing:

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

(88) (5) The Metastable Materials is Mixed for Pulping:

(89) 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.

(90) (6) Curing and Molding

(91) 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.

(92) 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.

(93) 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

(94) Implementation of Example 6, the waterproof magnesia oxychloride firebricks are made by municipal solid waste incineration fly ash.

(95) 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.

(96) 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

(97) The waterproof magnesium oxychloride firebricks are made with fly ash from domestic waste incineration according to the flow chart in the FIGURE, the specific steps are as follows:

(98) (1) Heavy Metal Stabilization:

(99) 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.

(100) (2) Magnesium Oxychloride Pulping:

(101) 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° C., the magnesium oxychloride slurry is prepared.

(102) (3) Curing and Growth:

(103) 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.

(104) (4) Crushing:

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

(106) (5) The Metastable Materials is Mixed for Pulping:

(107) 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.

(108) (6) Curing and Molding

(109) 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.

(110) 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.

(111) 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