Physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal and method of preparing and using same

Abstract

Disclosed is a physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal, and methods of preparing and using the same. The composite inhibitor consists of a chelate and attapulgite, the chelate is generated by chelation of proanthocyanidin with calcium chloride. The composite inhibitor has moisture-absorbing and moisture-retaining effect, and can reduce water dissipation at low temperature. A stable oxide insulating layer such as MgO and Al.sub.2O.sub.3 insulating layer can be formed at high temperature, which can block a coal body from contacting with oxygen. In addition, the composite inhibitor can capture hydroxyl free radicals generated during the chain-cycle reaction and destroy peroxide free radicals, and can also interact with an active moiety in coal to form a stable structure such as ether linkage and hydrogen bonding, thereby achieving permanent inhibition of low-rank coal.

Claims

1. A physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal, consisting of: a chelate; and an attapulgite, wherein the chelate is generated by chelation of proanthocyanidin with calcium chloride.

2. The physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal according to claim 1, wherein a mass ratio of proanthocyanidin to calcium chloride is between 1:6 and 1:8.

3. The physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal according to claim 2, wherein the mass ratio of proanthocyanidin to calcium chloride is 1:7.

4. The physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal according to claim 1, wherein a mass ratio of the chelate to the attapulgite is between 1:4 and 1:6.

5. The physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal according to claim 4, wherein a mass ratio of the chelate to the attapulgite is 1:5.

6. A method for preparing a physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal, the composite inhibitor consisting of a chelate and an attapulgite, wherein the method comprises: dissolving and dispersing proanthocyanidin and calcium chloride in solvent water to form a first mixture; stirring the first mixture for between 10 and 20 minutes to prepare a chelate solution; adding attapulgite to the chelate solution to form a second mixture; and stirring the second mixture for between 10 and 20 minutes to prepare a composite inhibitor solution.

7. A method for using a physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal, the composite inhibitor consisting of a chelate and an attapulgite, the chelate generated by chelation of proanthocyanidin with calcium chloride, wherein the method comprises: spraying a solution of the composite inhibitor to a residual coal region in an underground mined-out area to control spontaneous combustion of coal.

Description

DETAILED DESCRIPTION

(1) Embodiments of the present invention are further described in detail below. It should be noted that specific examples described herein are given solely for the purpose of illustration and are not to be construed as limitations of the present invention.

(2) An embodiment of the present invention provides a physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal, which consists of a chelate and attapulgite in a mass ratio of 1:4 to 1:6, the chelate is generated by chelation of proanthocyanidin with calcium chloride in a mass ratio of 1:6 to 1:8.

(3) The mass ratios of the components both are suitable ratio ranges, and the ratios may be adjusted according to practical situations. The mass ratios achieving an optimal effect are: a mass ratio of 1:7 of proanthocyanidin to calcium chloride; and a mass ratio of 1:5 of chelate to attapulgite.

(4) Aspects of the present invention are further described below by way of specific examples.

Example 1

(5) For a composite inhibitor having a mass concentration of 10%, proanthocyanidin and calcium chloride were weighted in a mass ratio of 1:6, added to 1 mL water, and stirred for 10 to 20 min, to obtain a chelate solution; attapulgite was weighted in a mass ratio of 1:4 of chelate to attapulgite, added to the chelate solution, and stirred for 10 to 20 min, to obtain a composite inhibitor solution. 1 g of a sample of low-rank coal was weighted and the grade of spontaneous combustion tendency of low-rank coal should be spontaneously flammable, thoroughly stirred and mixed with the prepared composite inhibitor solution, then allowed to stand in air to dry for 24 h, and placed into an exsiccator for use.

(6) (1) 10 mg of the coal sample was taken. A spontaneous combustion process of coal was simulated by a SDT-Q600 thermal analyzer with programmed temperature raising. The measured initial heat emission temperature of the coal sample after treatment with the inhibitor solution is 33 C. higher than that of the coal sample without the treatment. Also, the exotherm from the initial heat emission temperature to 100 C. and the exotherm from the initial heat emission temperature to 200 C. were significantly lower than those of the original coal.

(7) (2) The inhibition rate was determined to be up to 80% by an inhibition rate determination method for the exotherm from the initial heat emission temperature to 100 C.

(8) (3) The changes of methyl and methylene in coal with temperature before and after inhibition were tested by in situ IR spectroscopy. It was found that there is very little changes in methyl and methylene in the inhibited coal while there is significant changes in methyl and methylene in the original coal, indicating that the inhibitor can reduce oxidation of methyl and methylene in coal; and hydroxyl in the inhibited coal is significantly less than hydroxyl in the original coal, indicating that the inhibitor can reduce the presence of hydroxyl, thereby improving the property of spontaneous combustion of coal bodies.

Example 2

(9) For a composite inhibitor having the same mass concentration as that in example 1, proanthocyanidin and calcium chloride were weighted in a mass ratio of 1:7, added to 1 mL water, and stirred for 10 to 20 min, to obtain a chelate solution; attapulgite was weighted in a mass ratio of 1:5 of chelate to attapulgite, added to the chelate solution, and stirred for 10 to 20 min, to obtain a composite inhibitor solution. 1 g of a sample of low-rank coal was weighted and the grade of spontaneous combustion tendency of low-rank coal should be spontaneously flammable, thoroughly stirred and mixed with the prepared composite inhibitor solution, then allowed to stand in air to dry for 24 h, and placed into an exsiccator for use.

(10) (1) 10 mg of the coal sample was taken. A spontaneous combustion process of coal was simulated by a SDT-Q600 thermal analyzer with programmed temperature raising. The measured initial heat emission temperature of the coal sample after treatment with the inhibitor solution is 40 C. higher than that of the coal sample without the treatment. Also, the exotherm from the initial heat emission temperature to 100 C. and the exotherm from the initial heat emission temperature to 200 C. were significantly lower than those of the original coal.

(11) (2) The inhibition rate was determined to be up to 86% by an inhibition rate determination method for the exotherm from the initial heat emission temperature to 100 C.

(12) The resting conditions were the same as those in Example 1.

Example 3

(13) For a composite inhibitor having a mass concentration of 10%, proanthocyanidin and calcium chloride were weighted in a mass ratio of 1:8, added to 1 mL water, and stirred for 10 to 20 min, to obtain a chelate solution; attapulgite was weighted in a mass ratio of 1:6 of chelate to attapulgite, added to the chelate solution, and stirred for 10 to 20 min, to obtain a composite inhibitor solution. 1 g of a sample of low-rank coal was weighted and the grade of spontaneous combustion tendency of the low-rank coal should be spontaneously flammable, thoroughly stirred and mixed with the prepared composite inhibitor solution, then allowed to stand in air to dry for 24 h, and placed into an exsiccator for use.

(14) (1) 10 mg of the coal sample was taken. A spontaneous combustion process of coal was simulated by a SDT-Q600 thermal analyzer with programmed temperature raising. The measured initial heat emission temperature of the coal sample after treatment with the inhibitor solution is 36 C. higher than that of the coal sample without the treatment. Also, the exotherm from the initial heat emission temperature to 100 C. and the exotherm from the initial heat emission temperature to 200 C. were significantly lower than those of the original coal.

(15) (2) The inhibition rate was determined to be up to 84% by an inhibition rate determination method for the exotherm from the initial heat emission temperature to 100 C.

(16) The resting conditions were the same as those in Example 1.

(17) The description above describes particularly advantageous embodiments of the present invention. It should be noted that several modifications and variations can be made by those of ordinary skill in the art without departing from the principles of the invention, and these modifications and variations should be considered within the scope of the present invention.

(18) In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.