Preparation method for binder-free, coal-based, briquetted activated carbon

Abstract

Disclosed herein is a method for preparing coal-based, briquetted activated carbon. The method includes subjecting raw coal to a briquetting process, pulverizing the briquettes into particles, and performing carbonization and activation to obtain activated carbon. The briquetting process includes pulverizing raw coal to produce a feed, feeding the feed into a feed bin for degassing, adjusting the temperature and the water content of the feed in the feed bin, and feeding the feed in the feed bin into a briquetting apparatus for briquetting to form coal briquettes. The raw coal briquetting process of the preparation method is suited to a wide variety of coal, including non-caking coal. The preparation method yields a coal briquette product with a strength greater than 89% without any binder, which is beneficial to improve the strength and the like of activated carbon.

Claims

1. A method for preparing coal-based, briquetted activated carbon, the method comprising: I. briquetting raw coal to obtain coal briquettes, wherein briquetting comprises: a. pulverizing the raw coal to obtain pulverized coal, wherein, the average particle size of the pulverized coal is at least 20 the content of the pulverized coal with a particle size of up to 80 m is at least 90 wt %, and the content of the pulverized coal with a particle size ranging between 40 m-80 m is at least 10 wt %; b. feeding the pulverized coal into a feed bin of a briquetting apparatus, and degassing the pulverized coal in the feed bin; c. adjusting the temperature of the pulverized coal in the feed bin to 50 C.100 C. and the water content to 2 wt %-8 wt %; d. feeding the pulverized coal in the feed bin into the briquetting apparatus for briquetting to obtain coal briquettes, and II. crushing and granulating the coal briquettes obtained in step I, and carbonizing and activating the crushed and granulated coal briquettes thereby obtaining activated carbon.

2. The method according to claim 1, wherein briquetting further comprises: e. crushing a portion of the coal briquettes to coal particles having particle sizes of up to 3 mm and feeding the coal particles into the feed bin, wherein the coal particles comprise from 10 wt % to 40 wt % of the mass of the pulverized coal.

3. The method according to claim 2, wherein the pulverized coal in the feed bin is fed into the briquetting apparatus through a screw forced feeder and the briquetting apparatus is a double roller briquetting apparatus.

4. The method according to claim 2, wherein briquetting further comprises: blending the raw coal before pulverizing, wherein the grindability index of the raw coal is at least 55%.

5. The method according to claim 2, wherein briquetting further comprises: feeding the pulverized coal into a stirring bin for stirring and pre-degassing before the pulverized coal is fed into the feed bin, wherein the density of the pulverized coal after pre-degassing is 0.6 kg/L-0.8 kg/L.

6. The method according to claim 2, wherein in the pulverized coal the content of the pulverized coal with a particle size of up to 80 m is at least 95 wt %, and the content of the pulverized coal with a particle size of up to 40 m is at least 70 wt %.

7. The method according to claim 1, wherein feeding the pulverized coal into the feed bin comprises using a screw forced feeder and the briquetting apparatus is a double roller briquetting apparatus.

8. The method according to claim 7, wherein briquetting further comprises: blending the raw coal before pulverizing, wherein the grindability index of the raw coal is at least 55%.

9. The method according to claim 7, wherein briquetting further comprises: feeding the pulverized coal into a stirring bin for stirring and pre-degassing before the pulverized coal is fed into the feed bin, wherein the density of the pulverized coal after pre-degassing is 0.6 kg/L-0.8 kg/L.

10. The method according to claim 7, wherein in the pulverized coal the content of the pulverized coal with a particle size of up to 80 m is at least 95 wt %, and the content of the pulverized coal with a particle size of up to 40 m is at least 70 wt %.

11. The method according to claim 1, wherein briquetting further comprises: a1. blending the raw coal before pulverizing, wherein the grindability index of the raw coal is at least 55%.

12. The method according to claim 11, wherein briquetting further comprises: feeding the pulverized coal into a stirring bin for stirring and pre-degassing before the pulverized coal is fed into the feed bin, wherein the density of the pulverized coal after pre-degassing is 0.6 kg/L-0.8 kg/L.

13. The method according to claim 1, wherein briquetting further comprises b1. feeding the pulverized coal into a stirring bin for stirring and pre-degassing before the pulverized coal is fed into the feed bin, wherein the density of the pulverized coal after pre-degassing is 0.6 kg/L-0.8 kg/L.

14. The method according to claim 13, wherein the pulverized coal in the stirring bin is fed into the feed bin by a twin screw feeder or a star valve.

15. The method according to claim 1, wherein in the pulverized coal the content of the pulverized coal with a particle size of up to 80 m is at least 95 wt %, and the content of the pulverized coal with a particle size of up to 40 m is at least 70 wt %.

16. The method according to claim 1, wherein the pressure in the feed bin is a negative pressure, and the negative pressure is 1 kPa-3 kPa.

17. The method according to claim 1, wherein the temperature of the pulverized coal in the feed bin is 70 C.-85 C. and the moisture content of the pulverized coal is 2 wt %-6 wt %.

18. The method according to claim 1, wherein the crushed and granulated coal briquettes are subjected to an oxidation treatment prior to carbonization, wherein the oxidation treatment comprises: using a mixture of nitrogen and air as the oxidant which has an oxygen content of 8 vol %-15 vol % and oxidizing the pulverized coal at 200 C.-250 C. for 1.5 hours-4 hours.

19. The method according to claim 1, wherein carbonizing comprises: the temperature is 300 C.-500 C., the oxygen content of the carbonization atmosphere is up to 5 vol %, and the carbonization time of 1.5 hours-4 hours.

20. The method according to claim 1 wherein activating comprises: using water vapour as an activation medium and carrying out the activation reaction at 850 C.-950 C. for a reaction time of 3 hours-8 hours.

Description

EMBODIMENTS

(1) The present invention will be described in details below with the combination of examples, but the invention is not limited thereto.

(2) In the following examples/comparative examples, the characterization methods of the relevant parameters are described as follows:

(3) Average particle size-GB/T 19077.1-2008 particle size analysis laser diffractometry

(4) Grindability index-GB/T 2565-2014 method for determining the grindability index of coal (i.e. Had Grove method)

(5) Drum strength-measured according to GB/T7702.3-2008.

(6) The characterization methods of the relevant parameters of activated carbon are described as follows:

(7) Iodine adsorption value-measured according to GB/T7702.3-2008;

(8) Methylene blue adsorption value-measured according to GB/T7702.6-2008;

(9) Specific surface area-calculated by the BET method;

(10) Strength-measured according to GB/T7072.3-2008.

(11) The remaining parameters are characterized by national standard or conventional characterization in the field.

(12) In the following examples/comparative examples, raw coal is selected from one or more of the following coal types:

(13) Xinjiang Hami coal, from Xinjiang Baoli coal mine, its indicators are: moisture is 5.17 wt %, air drying based ash is 1.31 wt %, dry ashless based volatiles is 35.54 wt %, caking index is 2, belongs to non-caking coal, characteristic of coal cinder is 3, grindability index is 55%;

(14) Long flame coal of Heishan mining area, from Toksun Heishan coal mine in Xinjiang, its indicators are: moisture is 3.43 wt %, air drying based ash is 3.52 wt %, dry ashless based volatiles is 37.16 wt %, caking index is 0, belongs to non-adhesive coal, characteristic of coal cinder is 3, grindability index is 68%.

(15) In the following examples/comparative examples, the briquetting apparatus is a double roller briquetting apparatus, manufacturer: BEPEX; model: MS150.

Example 1

(16) (1) Xinjiang Hami coal was pulverized to pulverized coal having an average particle size of 29 m and sieved, wherein the content of the pulverized coal with a particle size larger than 80 m was 2.5 wt %; the content of the pulverized coal with a particle size larger than 40 m was 28 wt %;

(17) (2) the pulverized coal obtained in step (1) was fed into the feed bin of the briquetting apparatus, and the material in the feed bin was degassed to maintain the negative pressure in the feed bin at 2.5 kPa-3 kPa;

(18) (3) the temperature of the material in the feed bin was maintained at 50 C.-55 C., and the moisture content of the material in the feed bin was adjusted to 7 wt %-8 wt %;

(19) (4) the material in the feed bin was fed into the briquetting apparatus for briquetting, and the line pressure between the rollers was about 11 t/cm-12 t/cm during briquetting to obtain briquetted material (coal briquette).

(20) The strength of the coal briquette was tested, and the drum strength thereof was 89.2%.

Example 2

(21) The difference between example 1 and example 2 lies in that the mixture of Xinjiang Hami coal and Changyan coal of Heishan mining area in a mass ratio of 1:1 was used as the raw coal in example 2.

(22) The strength of the coal briquette was tested, and the drum strength thereof was 91.4%.

Example 3

(23) (1) Xinjiang Hami coal and long flame coal of Heishan mining area were mixed evenly according to a mass ratio of 1:1, and the mixture was pulverized to pulverized coal having an average particle size of 35 m and sieved, wherein the content of the pulverized coal with a particle size larger than 80 m was 8.2 wt %; the content of the pulverized coal with a particle size larger than 40 m was 22 wt %;

(24) (2) the pulverized coal obtained in step (1) was fed into a stirring bin for stirring and degassing, the top of the stirring bin was provided with a pipeline for pumping out gas, so that the density of the pulverized coal after stirring reached 0.60 kg/L-0.65 kg/L, and then the pulverized coal in the stirring bin was fed into the feed bin of the briquetting apparatus through a star valve;

(25) (3) the material in the feed bin was degassed to maintain the negative pressure in the feed bin at 2.5 kPa-3 kPa;

(26) (4) the temperature of the material in the feed bin was maintained at 80 C.-85 C., and the moisture content of the material in the feed bin was adjusted to 2 wt %-3 wt %;

(27) (5) the material in the feed bin was fed into the briquetting apparatus through a screw forced feeder for briquetting, the line pressure between the rollers was about 11 t/cm-12 t/cm when briquetting, to obtain briquetted material.

(28) The strength of the coal briquette was tested, and the drum strength thereof was 91.8%.

Example 4

(29) (1) Xinjiang Hami coal was pulverized to pulverized coal having an average particle size of 22 m and sieved, wherein the content of the pulverized coal with a particle size larger than 80 m was 2 wt %; the content of the pulverized coal with a particle size larger than 40 m was 15 wt %;

(30) (2) the pulverized coal obtained in step (1) was fed into a feed bin of the briquetting apparatus, and the coal briquette prepared in example 1 was crushed to coal particles having a particle size of 1 mm-3 mm, and the coal particles accounting for 25 wt % of the mass of the pulverized coal in the feed bin were fed into the feed bin;

(31) (3) the material in the feed bin was degassed to maintain the negative pressure in the feed bin at 2 kPa-2.5 kPa;

(32) (4) the temperature of the material in the feed bin was maintained at 50 C.-55 C., the moisture content of the material in the feed bin was adjusted to 5 wt %-6 wt %;

(33) (5) the material in the feed bin was fed into the briquetting apparatus through a screw forced feeder for briquetting, the line pressure between the rollers was about 11 t/cm-12 t/cm when briquetting, to obtain briquetted material.

(34) The strength of the coal briquette was tested, and the drum strength thereof was 92.6%.

Example 5

(35) (1) The pulverized coal obtained in step (1) of example 4 was fed into a stirring bin for stirring and degassing, the top of the stirring bin was provided with a pipeline for pumping out gas, so that the density of the pulverized coal after stirring reached 0.75 kg/L-0.80 kg/L;

(36) (2) the pulverized coal in the stirring bin was fed into the feed bin of the briquetting apparatus through a twin screw feeder, and the coal briquettes prepared in example 3 was crushed to coal particles having a particle size of 1 mm-3 mm, and the coal particles accounting for 35 wt % of the mass of the pulverized coal in the feed bin were fed into the feed bin;

(37) (3) the material in the feed bin was degassed to maintain the negative pressure in the feed bin at 2.5 kPa-3 kPa;

(38) (4) the temperature of the material in the feed bin was maintained at 70 C.-75 C., and the moisture content of the material in the feed bin was adjusted to 2 wt %-3 wt %;

(39) (5) the material in the feed bin was fed into the briquetting apparatus through a screw forced feeder for briquetting, the line pressure between the rollers was about 11 t/cm-12 t/cm when briquetting, to obtain briquetted material.

(40) The strength of the coal briquettes was tested, and the drum strength thereof was 94.3%.

Comparative Example 1

(41) Water was sprayed to Xinjiang Hami coal to adjust its water content to 12 wt %, and then Xinjiang Hami coal was pulverized to material having an average particle size of 8.1 m to obtain pulverized coal. The obtained pulverized coal was fed into the briquetting apparatus for briquetting, and the line pressure between the rollers was about 11 t/cm-12 t/cm when briquetting, to obtain briquetted material.

(42) The strength of briquetted material was tested, and the drum strength thereof was 90.4%.

Comparative Example 2

(43) Xinjiang Hami coal was crushed to particles below 10 mm, the coal pitch accounting for 10 wt % of the particles was added, and the mixture was pulverized and sieved to prepare pulverized coal having a particle size of 64 m-80 m. The obtained pulverized coal was fed into the briquetting apparatus for briquetting, and the line pressure between the rollers was about 11 t/cm-12 t/cm when briquetting, to obtain briquetted material.

(44) The strength of briquetted material was tested, and the drum strength thereof was 85%

Comparative Example 3

(45) Xinjiang Hami coal was pulverized and sieved to prepare pulverized coal having a particle size of 64 m-80 m, and the coal tar accounting for 30 wt % of the pulverized coal was added. After stirring evenly in a blender, the mixture was fed into a plodder to prepare coal briquettes with standard size. The coal briquettes was air-dried at 20 C. for 48 hours and then stoved at 200 C. for 2 hours.

(46) The strength of the coal briquettes was tested, and the drum strength thereof was 91.8%.

Example 6-10

(47) The coal briquettes prepared in examples 1-5 were subjected to granulation, oxidation, carbonization and activation respectively, wherein granules having a particle size of 6.7 mm-8 mm were obtained by the granulation of the coal briquettes.

(48) The oxidizing conditions of the granules were as follows: a mixed gas of nitrogen and oxygen was introduced into an external-heating rotary kiln heated by electric, the oxygen content was controlled to be about 8 vol %, and the reaction was carried out at 220 C. for 4 hours. The carbonization conditions were as follows: the granules were calcined in the external-heating rotary kiln heated by electric with flowing nitrogen at 500 C. for 4 hours to be carbonized. The activation conditions were as follows: in the presence of an activator, i.e. flowing steam having a flow rate of 1.5 kg of the steam per kilogram of carbonized particles per hour, the carbonized particles in the rotary kiln were activated at 900 C. for 4 hours to obtain activated carbon products.

(49) The above activated carbon products were characterized separately, as shown in Table 1.

(50) TABLE-US-00001 TABLE 1 Item Example 6 Example 7 Example 8 Example 9 Example 10 Iodine adsorption value 1090 1069 1100 1063 1093 mg/g Methylene blue 212 198 219 201 219 adsorption value mg/g Specific surface area 957 947 998 937 1001 m.sup.2/g Strength % 96.4 96.7 96.2 97.1 95.4 Yield 27 27 25 26 25 wt %