Method for preparing biochar

Abstract

A method for preparing biochar, including steps as follows: dosing: putting pre-crushed biomass into a reactor; charring conversion: heating the reactor to a certain temperature and pressure, and putting an active group-containing active agent containing 1% to 5% by mass of biomass and a catalyst containing 1% to 10% by mass of biomass (or putting the catalyst first and then putting the active agent) into the reactor to perform solid solution charring on the biomass; and cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar. Feedstocks are abundant and cheap, farmland biomass waste is reused, and the active group-containing active agent is added in biomass charring, which can effectively inhibit side reactions and coordinate with the catalyst to perform solid solution charring on the biomass, thereby improving a biochar conversion rate and making the charring process clean and environmentally friendly.

Claims

1. A method for preparing biochar comprising steps as follows: drying pre-crushed biomass at a temperature between 120° C.-150° C. and pre-charring the pre-crushed biomass at a temperature between 150° C.-220° C.; dosing a reactor with the pre-crushed biomass; heating the pre-crushed biomass disposed within the reactor to a pre-determined temperature and pressure and adding an active group-containing active agent in an amount between 1%-5% by mass of biomass and a catalyst in an amount between 1%-10% by mass of biomass into the reactor and solid charring the biomass; cooling the charred biomass to a temperature of less than or equal to 40° C. thereby obtaining the cooled biochar.

2. A method for preparing biochar; comprising steps as follows: drying pre-crushed biomass at a temperature between 120° C.-150° C. and pre-charring the pre-crushed biomass at a temperature between 150° C.-220° C.; mixing the pre-crushed biomass with a catalyst and then adding the mixture into a reactor, in which a mass ratio of the biomass to the catalyst is 90 to 99:10 to 1; heating the reactor to a pre-determined temperature and pressure, and adding an active group-containing active agent in an amount between 1%-5% by mass of biomass into the reactor and solid charring the biomass; cooling the charred biomass to a temperature of less than or equal to 40° C. thereby obtaining the biochar.

3. The method for preparing biochar according to claim 1 or 2, wherein an active group of the active group-containing active agent is at one selected from the group consisting of carboxyl, hydroxyl, carbonyl, and methoxy.

4. The method for preparing biochar according to claim 3, wherein the carboxyl content of active agent is between 10%-25%, the hydroxyl content of the active agent is between 4%-10%, the carbonyl content of the active agent is between 13%-25%, and the methoxy content of the active agent is between 5%-15%.

5. The method for preparing biochar according to claim 3, wherein the hydroxyl is contained in a carboxylic acid, propylene glycol methyl ether acetate, an acid radical, or a polycarboxylic acid.

6. The method for preparing biochar according to claim 1 or 2, wherein the catalyst is selected from a group consisting of a potassium salt, a calcium salt, a transition metal salt, a metal oxide, and a molecular sieve catalyst.

7. The method for preparing biochar according to claim 6, wherein the metal oxide is selected from a group consisting of Al.sub.2O.sub.3, MgO, or SiO.sub.2, and the molecular sieve catalyst is a Y, β, and ZSM-5 molecular sieve.

8. The method for preparing biochar according to claim 1 or 2, wherein the biomass charring is took place between 200° C.-800° C. for a charring duration between 10 min-120 min.

9. The method for preparing biochar according to claim 1 or 2, wherein the active agent is added to the reactor at a temperature between 220° C.-580° C. and a pressure between 0.01 MPa-10.0 MPa.

Description

EXAMPLE 1

(1) Dosing: putting pre-crushed corn stalks or granules into a reactor;

(2) charring conversion: heating the reactor to 220° C., and putting a carboxylic acid containing 1% by mass of biomass and a calcium salt containing 1% by mass of biomass into the reactor to perform solid solution charring on the biomass; and

(3) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

EXAMPLE 2

(4) Dosing: putting pre-crushed rice hulls or granules into a reactor;

(5) charring conversion: heating the reactor to 300° C., and putting carboxyl containing 5% by mass of biomass and a transition metal salt containing 10% by mass of biomass into the reactor to perform solid solution charring on the biomass; and

(6) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

EXAMPLE 3

(7) Dosing: putting pre-crushed wood bits or granules into a reactor;

(8) charring conversion: heating the reactor to 350° C., and putting carbonyl containing 3% by mass of biomass and a Y molecular sieve containing 5% by mass of biomass into the reactor to perform solid solution charring on the biomass; and

(9) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

EXAMPLE 4

(10) Dosing: mixing pre-crushed corn stalks or granules with a 1% calcium salt and then putting the mixture into a reactor;

(11) charring conversion: heating the reactor to 220° C., and putting a carboxylic acid containing 1% by mass of biomass into the reactor to perform solid solution charring on the biomass; and

(12) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

EXAMPLE 5

(13) Dosing: mixing pre-crushed rice hulls or granules with a 10% transition metal salt and then putting the mixture into a reactor;

(14) charring conversion: heating the reactor to 300° C., and putting a carboxyl containing 5% by mass of biomass into the reactor to perform solid solution charring on the biomass; and

(15) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

EXAMPLE 6

(16) Dosing: mixing pre-crushed wood bits or granules with a 5% Y molecular sieve and then putting the mixture into a reactor;

(17) charring conversion: heating the reactor to 350° C., and putting carbonyl containing 3% by mass of biomass into the reactor to perform solid solution charring on the biomass; and

(18) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

EXAMPLE 7

(19) Dosing: putting pre-crushed corn stalks or granules into a reactor;

(20) charring conversion: heating the reactor to 220° C., and putting a carboxylic acid containing 1% by mass of biomass, 2% acetic acid, 2% formaldehyde, and a calcium salt containing 1% by mass of biomass into the reactor to perform solid solution charring on the biomass; and

(21) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

(22) Time required to catalyze the reaction by adding the catalyst at different charring temperatures is different, and the lower the temperature at which the catalyst is added, the longer the time required to catalyze the reaction. A process temperature of the charring conversion step according to the present invention is 200° C. to 800° C., and charring time thereof is 10 min to 120 min.

COMPARATIVE EXAMPLE 1

(23) Dosing: putting pre-crushed corn stalks into a reactor;

(24) charring conversion: heating the reactor to 220° C., and putting a calcium salt containing 1% by mass of biomass into the reactor to perform charring on the biomass; and

(25) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

COMPARATIVE EXAMPLE 2

(26) Dosing: mixing pre-crushed rice hulls with a 10% transition metal salt and then putting the mixture into a reactor;

(27) charring conversion: heating the reactor to perform charring on the biomass; and

(28) cooling: after the charring conversion is completed, cooling the reactor to 40° C. or lower to obtain the biochar.

(29) Experimental data of coal conversion rates of Examples 1 to 7 and Comparative Examples 1 and 2 described above were as follows:

(30) TABLE-US-00001 Biomass Active group Catalyst Reaction Coal conversion type type type temperature rate % Comparative corn 1% calcium 220° C. 40% Example 1 stalks salt Comparative rice 10% transition 300° C. 41% Example 2 hulls metal salt Example 1 corn 1% carboxylic 1% calcium 220° C. 60% stalks acid salt Example 2 rice 5% carboxyl 10% transition 300° C. 63% hulls metal salt Example 3 wood 3% carbonyl 5% Y molecular 350° C. 62% bits sieve Example 4 corn 1% carboxylic 1% calcium 220° C. 61% stalks acid salt Example 5 rice 1% carboxylic 10% transition 300° C. 63% hulls acid metal salt Example 6 wood 3% carbonyl 5% Y molecular 350° C. 62% bits sieve Example 7 corn 1% carboxylic 1% calcium 220° C. 64% stalks acid, 2% acetic salt acid, 2% formaldehyde

(31) It can be seen from the experimental data that by coordinating the active group-containing active agent with the catalyst, the present invention can inhibit side reactions effectively and perform solid solution charring on the biomass, thereby improving a coal conversion rate and making the charring process clean and environmentally friendly.

(32) The above-described embodiments merely describe preferred embodiments of the present invention and are not intended to limit the scope of the invention, and various modifications and improvements of the technical solutions of the invention made by those skilled in the art all fall within the scope of the invention defined by the claims without departing from the spirit of the invention.