Clean coal for combustion and preparation method thereof

Abstract

The present disclosure relates to a clean coal for combustion and a preparation method thereof. The preparation method includes the following steps: (1) dispersing starch in water, uniformly stirring, and fully gelatinizing; (2) adding a sulfur-fixing agent into the gelatinization solution, and centrifuging to obtain the starch gelatinized solution containing the sulfur-fixing agent; (3) crushing the coal for combustion to obtain coal particles; and (4) conveying the coal particles to a fluidized bed, spraying the starch gelatinized solution containing the sulfur-fixing agent on the coal particles in a suspension state, and drying to obtain coal particles adsorbed with the sulfur-fixing agent and gelatinized starch. According to the present disclosure, the starch gelatinized solution is used to dissolve the soluble sulfur-fixing agent, and then the starch solution is adsorbed in-situ into the coal particles, so that the soluble sulfur-fixing agent is uniformly adsorbed in the coal for combustion.

Claims

1. A preparation method of a clean coal for combustion, comprising the following steps: (1) dispersing starch in water and uniformly stirring to obtain a starch milk with a concentration of 5-20 g/L; and heating the starch milk to 70-100 C. and gelatinizing for 10-60 minutes to obtain a starch gelatinized solution; (2) adding a sulfur-fixing agent into the starch gelatinized solution under a condition of controlling a temperature of the starch gelatinized solution at 30-60 C., and centrifuging to remove insoluble substances to obtain the starch gelatinized solution containing the sulfur-fixing agent; (3) crushing a coal for combustion, and screening to obtain coal particles; and (4) conveying the coal particles to a fluidized bed, spraying the starch gelatinized solution containing the sulfur-fixing agent on the coal particles in a suspension state, and drying to obtain coal particles adsorbed with the sulfur-fixing agent and gelatinized starch; wherein the sulfur-fixing agent in the step (2) is a soluble sulfur-fixing agent; and the soluble sulfur-fixing agent is one or more selected from the group consisting of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2 and Mg(HCO.sub.3).sub.2; and in step (2), an amylase is further added, and an addition amount of the amylase is 3-6% of a mass of the starch.

2. The preparation method according to claim 1, wherein the soluble sulfur-fixing agent is a mixture of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2 and Mg(HCO.sub.3).sub.2.

3. The preparation method according to claim 2, wherein a mass ratio of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2 and Mg(HCO.sub.3).sub.2 is 1:2-5:1-3.

4. The preparation method according to claim 1, wherein a ratio of a mass of the soluble sulfur-fixing agent to a volume of the starch gelatinized solution in step (2) is 5-15:1 (g/L).

5. The preparation method according to claim 1, wherein the coal particles in step (3) have an average particle size of 5-200 m.

6. The preparation method according to claim 1, wherein in step (4), the starch gelatinized solution containing the sulfur-fixing agent is uniformly sprayed onto the coal particles at room temperature in a ratio of 3-5.

7. The preparation method according to claim 1, wherein in step (4), a drying temperature is above 80 C.

8. The preparation method according to claim 1, wherein the amylase is one or more selected from the group consisting of -amylase, -amylase, glucoamylase and isoamylase.

9. The preparation method according to claim 8, wherein the amylase is a mixture of -amylase and isoamylase at a mass ratio of 1:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The sole FIGURE is a Scanning Electron Microscope (SEM) image of a coal particle adsorbed with a sulfur-fixing agent and gelatinized starch prepared in Embodiment 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) In order to better explain the purpose, the technical solution and the advantages of the present disclosure, the present disclosure will be further described below with reference to specific embodiments. In the embodiment, the experimental methods used are conventional methods unless otherwise specified, and the materials and reagents used can be obtained from commercial sources unless otherwise specified.

Embodiment 1

(3) A Preparation Method of a Clean Coal for Combustion

(4) The preparation method for the clean coal for combustion, comprising the following steps: (1) dispersing starch in water and uniformly stirring to obtain a starch milk with a concentration of 5 g/L; and fully gelatinizing the starch milk at 70 C. to obtain starch gelatinized solution; (2) adding a sulfur-fixing agent into the starch gelatinized solution under a condition of controlling a temperature of the starch gelatinized solution at 30-60 C., where a mass-to-volume ratio of the soluble sulfur-fixing agent and the starch gelatinized solution is 5:1 (g/L), and centrifuging to remove insoluble substances to obtain a starch gelatinized solution containing the sulfur-fixing agent; and the sulfur-fixing agent is a mixture of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2 and Mg(HCO.sub.3).sub.2, with a mass ratio of 1:2:1; (3) crushing the coal for combustion, and screening to obtain coal particles, with an average particle size of the coal particles being 5 m; and (4) conveying the coal particles to a fluidized bed, uniformly spraying the starch gelatinized solution containing the sulfur-fixing agent on coal for combustion at room temperature in a suspension state according to a proportion of 5, and drying at 80 C. to obtain coal particles adsorbed with the sulfur-fixing agent and gelatinized starch, as shown in the sole FIGURE.

Embodiment 2

(5) A Preparation Method of a Clean Coal for Combustion

(6) The preparation method for the clean coal for combustion, comprising the following steps: (1) dispersing starch in water and uniformly stirring to obtain a starch milk with a concentration of 20 g/L; and fully gelatinizing the starch milk at 100 C. to obtain starch gelatinized solution; (2) adding a sulfur-fixing agent into the starch gelatinized solution under a condition of controlling a temperature of the starch gelatinized solution at 30-60 C., where a mass-to-volume ratio of the soluble sulfur-fixing agent and the starch gelatinized solution is 15:1 (g/L), and centrifuging to remove insoluble substances to obtain a starch gelatinized solution containing the sulfur-fixing agent; and the sulfur-fixing agent is a mixture of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2 and Mg(HCO.sub.3).sub.2, with a mass ratio of 1:5:3; (3) crushing the coal, and screening to obtain coal particles, with an average particle size of the coal particles being 50 m; and (4) conveying the coal particles to a fluidized bed, uniformly spraying the starch gelatinized solution containing the sulfur-fixing agent on coal for combustion at room temperature in a suspension state according to a proportion of 3, and drying at 100 C. to obtain coal particles adsorbed with the sulfur-fixing agent and gelatinized starch.

Embodiment 3

(7) A Preparation Method of a Clean Coal for Combustion

(8) The preparation method for the clean coal for combustion, comprising the following steps: (1) dissolving starch in water and uniformly stirring to obtain a starch milk with a concentration of 10 g/L; and fully gelatinizing the starch milk at 90 C. to obtain starch gelatinized solution; (2) adding a sulfur-fixing agent into the starch gelatinized solution under a condition of controlling a temperature of the starch gelatinized solution at 30-60 C., where a mass-to-volume ratio of the soluble sulfur-fixing agent and the starch gelatinized solution is 10:1 (g/L), and centrifuging to remove insoluble substances to obtain a starch gelatinized solution containing the sulfur-fixing agent; and the sulfur-fixing agent is a mixture of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2 and Mg(HCO.sub.3).sub.2, with a mass ratio of 1:4:2; (3) crushing the coal for combustion, and screening to obtain coal particles, with an average particle size of the coal particles being 200 m; and (4) conveying the coal particles to a fluidized bed, uniformly spraying the starch gelatinization solution containing the sulfur-fixing agent on coal for combustion at room temperature in a suspension state according to a proportion of 4, and drying at 100 C. to obtain coal particles adsorbed with the sulfur-fixing agent and gelatinized starch.

Embodiment 4

(9) The only difference from Embodiment 3 is that in step (2), an amylase is further added, an addition amount of the amylase is 5% of a mass of the starch, the amylase is -amylase and isoamylase in a mass ratio of 1:1, and the other steps and operations are the same as in Embodiment 3.

Embodiment 5

(10) The only difference from Embodiment 4 is that in step (2), an addition amount of the amylase is 3% of a mass of the starch, and the other steps and operations are the same as in Embodiment 4.

Embodiment 6

(11) The only difference from Embodiment 4 is that in step (2), an addition amount of the amylase is 6% of a mass of the starch, and the other steps and operations are the same as in Embodiment 4.

Comparative Embodiment 1

(12) The difference from Embodiment 3 is that the sulfur-fixing agent is a mixture of Ca(HCO.sub.3).sub.2 and Mg(HCO.sub.3).sub.2 in a mass ratio of 4:2, a total addition amount of the sulfur-fixing agent is the same as that in Embodiment 3, and the other steps and operations are the same as in Embodiment 3.

Comparative Embodiment 2

(13) The difference from Embodiment 3 is that the sulfur-fixing agent is a mixture of Ba(OH).sub.2 and Ca(HCO.sub.3).sub.2 in a mass ratio of 1:4, a total addition amount of the sulfur-fixing agent is the same as that in Embodiment 3, and the other steps and operations are the same as in Embodiment 3.

Comparative Embodiment 3

(14) The difference from Embodiment 3 is that the sulfur-fixing agent is a mixture of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2 and Ca(HCO.sub.3).sub.2 in a mass ratio of 8:1:1, a total addition amount of the sulfur-fixing agent is the same as that in Embodiment 3, and the other steps and operations are the same as in Embodiment 3.

Comparative Embodiment 4

(15) The difference from Embodiment 3 is that the sulfur-fixing agent is Ca(HCO.sub.3).sub.2, a total addition amount of the sulfur-fixing agent is the same as that in Embodiment 3, and the other steps and operations are the same as in Embodiment 3.

Comparative Embodiment 5

(16) The difference from Embodiment 4 is that a mass ratio of -amylase and isoamylase is 3:1, their addition amount is the same as that in Embodiment 4, and the other steps and operations are the same as in Embodiment 4.

Comparative Embodiment 6

(17) The difference from Embodiment 4 is that a mass ratio of -amylase and isoamylase is 1:3, their addition amount is the same as that in Embodiment 4, and the other steps and operations are the same as in Embodiment 4.

Comparative Embodiment 7

(18) The difference from Embodiment 4 is that only -amylase is used, its addition amount is the same as that in Embodiment 4, and the other steps and operations are the same as in Embodiment 4.

Comparative Embodiment 8

(19) The difference from Embodiment 4 is that a particle size of the coal particles in step (3) is different, specifically: (3) crushing the coal for combustion, and screening to obtain coal particles, with an average particle size of the coal particles being 4 mm; and the other steps and operations are the same as in Embodiment 4.

(20) Effect Detection:

(21) Detection of Combustible Content and Sulfur Content in the Ash Obtained After Complete Combustion of Coal

(22) Blank sample (raw coal): The coal is crushed to a particle size range of 5-200 m, without adsorption treatment.

(23) Detection Method: The combustible content is determined according to DNL567.6-2016 using a drying oven+muffle furnace method, and the sulfur content is measured using the coulometric titration method as specified in DL/T567.7-2007. The detection results are shown in Table 1 below.

(24) TABLE-US-00001 TABLE 1 Combustible Combustible Sulfur Sulfur content in content in content in content in fly ash slag fly ash slag Blank sample 7.54% 3.82% 0.80% 0.36% Embodiment 1 1.52% 0.95% 1.08% 0.72% Embodiment 2 1.57% 0.90% 1.12% 0.75% Embodiment 3 1.35% 0.88% 1.10% 0.73% Comparative 1.36% 0.90% 0.95% 0.52% embodiment 1 Comparative 1.37% 0.92% 0.92% 0.61% embodiment 2 Comparative 1.35% 0.90% 0.94% 0.58% embodiment 3 Comparative 2.82% 1.25% 0.88% 0.46% embodiment 4 Embodiment 4 1.03% 0.71% 1.31% 0.92% Embodiment 5 1.05% 0.73% 1.28% 0.86% Embodiment 6 1.08% 0.75% 1.26% 0.90% Comparative 1.30% 0.84% 1.24% 0.86% embodiment 5 Comparative 1.32% 0.83% 1.22% 0.88% embodiment 6 Comparative 1.34% 0.86% 1.18% 0.84% embodiment 7 Comparative 1.82% 1.10% 0.75% 0.62% embodiment 8

(25) After coal combustion, in addition to gaseous combustion products, it generally also includes small particles of fly ash and large particles of slag. The higher the combustible content of fly ash and slag, the less complete the coal combustion is; the higher the sulfur content of fly ash and slag, the better the sulfur fixation effect is.

(26) According to the test data in Table 1 above, in Embodiments 1-3 of the present disclosure, a mixture of Ba(OH).sub.2, Ca(HCO.sub.3).sub.2, and Mg(HCO.sub.3).sub.2 is used as a sulfur-fixing agent, which is dissolved in starch gelatinized solution. This starch solution is then adsorbed in situ onto coal particles, allowing the soluble sulfur-fixing agent to be uniformly adsorbed into the coal during combustion, thus significantly improving the combustion efficiency and sulfur fixation effect of the coal. In Embodiments 4-6, -amylase and isoamylase with a mass ratio of 1:1 are added into the starch gelatinized solution, which enables better dispersion of the sulfur-fixing agent components in the starch gelatinized solution and increases its fluidity, further enhancing the combustion efficiency and sulfur fixation effect of the coal. In Comparative Embodiments 1-3, changing the ratio or type of sulfur-fixing agent has little impact on the combustion efficiency of coal but significantly affects the sulfur fixation effect. In Comparative Embodiment 4, replacing the sulfur-fixing agent with Ca(OH).sub.2 significantly affects the sulfur fixation effect of coal combustion. In Comparative Embodiments 5-7, altering the ratio or type of -amylase and isoamylase affects the fluidity of the starch gelatinized solution, significantly impacting both the combustion efficiency and sulfur fixation effect of coal. In Comparative Embodiment 8, changing the particle size of coal particles significantly affects the adsorption efficiency of the sulfur-fixing agent by coal and the combustion efficiency, resulting in a weakened sulfur fixation effect.

(27) The above embodiments are only used to illustrate the technical solutions of the present disclosure but not to limit them. Although the present disclosure has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still make modifications or equivalent substitutions to the specific embodiments of the present disclosure. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present disclosure are within the scope of the claims of the present disclosure.