KR20240076237A - Functionalized biochar with sulfur for adsorbing gaseous mercury and Manufacturing method thereof - Google Patents

Abstract

The present invention relates to a sulfur-functionalized biochar for adsorption and removal of gaseous mercury and a method for manufacturing the same. More specifically, the sulfur-functionalized biochar and a method for manufacturing the same improve the adsorption capacity of gaseous mercury by functionalizing the surface of the biochar with sulfur. It's about.
The method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury according to the present invention includes a raw material filling step (S100) of filling the inside of the reactor with biochar and elemental sulfur as raw materials; and filling the inside of the reactor filled with the raw materials with an inert gas. It includes a purging step (S200) of purging; and an activation step (S300) of preventing air inflow into the purged reactor and activating the raw materials by heat treatment.

Description

Functionalized biochar with sulfur for adsorbing gaseous mercury and manufacturing method thereof}

The present invention relates to a sulfur-functionalized biochar for adsorption and removal of gaseous mercury and a method for manufacturing the same. More specifically, the sulfur-functionalized biochar and a method for manufacturing the same improve the adsorption capacity of gaseous mercury by functionalizing the surface of the biochar with sulfur. It's about.

Various types of highly volatile heavy metals are emitted from fossil fuel power plants, and it is estimated that approximately 60-70% of mercury emissions worldwide are emitted from combustion facilities such as coal-fired power plants.

Mercury is mainly emitted into the atmosphere in the form of elemental mercury (Hg ⁰ ), and mercury discharged into the atmosphere accumulates in the human body through the natural circulation process and food chain, causing fatal diseases such as central nervous system abnormalities, kidney abnormalities, and speech disorders. Removal is required because it acts as a harmful substance that causes

Conventionally, existing air pollutant control devices such as particulate matter control device, sulfur dioxide control device, and nitric oxide control device have been used to remove elemental mercury in the air, but elemental mercury has high volatility, chemical inertness, and does not dissolve in water. It is not effective due to its characteristics.

Other known methods include an adsorption method using a solid adsorbent such as activated carbon, and a method using an oxidizing agent to remove oxidizing agents such as chlorides and sulfides by injecting them into the exhaust gas in a liquid or solid state.

As a patent document related to the adsorption method using a solid adsorbent such as activated carbon, Domestic Patent No. 10-0599185 proposes a method and production device for sulfur-impregnated activated carbon for removing gaseous mercury, and sulfur-impregnated activated carbon made therefrom. Registered Patent No. 10-0622797 proposes an adsorbent and its manufacturing method for removing trace amounts of harmful air pollutants from combustion exhaust gases, and Domestic Registered Patent No. 10-1229680, which is a patent document related to a mercury removal method using an oxidizing agent, provides A gas treatment system and method for removing mercury from exhaust gas are presented.

The mercury removal method is not economical because it uses expensive catalysts and activated carbon, and the mercury removal efficiency is low compared to the input cost. When an oxidizing agent is used, additional equipment is required to supply the oxidizing agent, and the oxidizing agent causes corrosion in the downstream process. There were limitations that made repairs difficult.

Meanwhile, biochar is a material made through pyrolysis of biomass generated in forests and livestock industries, and has traditionally been used to reduce nutrient runoff in the soil, increase carbon, improve soil, and increase soil cultivability. In addition to benefits, it is known to have effects such as carbon sequestration, reduction of N ₂ O emissions, reduction of methane gas emissions, and reduction of odor. Recently, research results on the adsorption and removal of heavy metals contained in water and soil have been reported.

The present inventor attempted to manufacture a mercury adsorbent using biochar as a replacement for expensive activated carbon, and attempted to modify the surface with sulfur to improve mercury adsorption capacity, minimize sulfur loss during reaction, and maximize process efficiency. The present invention was developed by developing a method for producing functionalized biochar.

Domestic registered patent No. 10-0599185 (Sulfur-impregnated activated carbon manufacturing method and manufacturing device for removing gaseous mercury, and sulfur-impregnated activated carbon made therefrom) Domestic Patent No. 10-0622797 (Adsorbent for removing trace amounts of harmful air pollutants from combustion exhaust gases and its manufacturing method) Domestic Patent No. 10-1229680 (Exhaust gas treatment system and method for removing mercury in exhaust gas)

The purpose of the present invention to solve the above problems is to functionalize the surface of biochar with sulfur, thereby minimizing sulfur loss by inducing re-adsorption of gaseous sulfur removed from the reactant and improving the adsorption capacity of gaseous mercury. To provide biochar and its manufacturing method.

In order to solve the above problems, the method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury of the present invention includes a raw material filling step (S100) of filling biochar and elemental sulfur as raw materials into the reactor; and a reactor filled with raw materials. It includes a purging step (S200) of purging the interior with an inert gas; and an activation step (S300) of preventing air inflow into the purged reactor and activating the raw materials by heat treatment.

In the raw material filling step (S100), elemental sulfur is filled in an amount of 1 to 10% by weight.

The activation step (S300) is characterized in that the gaseous sulfur desorbed from the reactants during the activation reaction is re-adsorbed to functionalize the biochar with sulfur.

In the activation step (S300), the temperature is increased from room temperature to 250 to 400°C at a rate of 5 to 15°C/min and maintained for 3 to 6 hours.

In order to solve the above problems, the sulfur-functionalized biochar for adsorption and removal of gaseous mercury of the present invention is characterized in that it is manufactured by the method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury.

As described above, according to the sulfur-functionalized biochar for adsorption and removal of gaseous mercury and its manufacturing method according to the present invention, in functionalizing the surface of biochar with sulfur, re-adsorption of gaseous sulfur removed from the reactant is induced. It has the effect of minimizing the loss of sulfur and improving the adsorption capacity of gaseous mercury.

Figure 1 is a flow chart showing a method for producing sulfur-functionalized biochar with improved adsorption capacity of gaseous mercury according to the present invention.
Figure 2 is a schematic diagram showing the configuration of a reactor used in the method for producing sulfur-functionalized biochar with improved adsorption capacity of gaseous mercury according to the present invention.
Figure 3 is an actual photograph of the reactor used in the method for producing sulfur-functionalized biochar with improved adsorption capacity of gaseous mercury according to the present invention.
Figure 4 is a schematic diagram of a laboratory-scale system for testing the mercury adsorption performance of sulfur-functionalized biochar with improved adsorption capacity of gaseous mercury according to the present invention.
Figure 5 is a mercury adsorption curve of sulfur-functionalized biochar with improved gaseous mercury adsorption capacity according to the present invention.

Specific features and advantages of the present invention will be described in detail below with reference to the accompanying drawings. Prior to this, if it is determined that a detailed description of the functions and configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Figure 1 is a flow chart showing a method for producing sulfur-functionalized biochar with improved adsorption capacity for gaseous mercury according to the present invention, and Figure 2 is a flow chart showing the method for producing sulfur-functionalized biochar with improved adsorption capacity for gaseous mercury according to the present invention. It is a schematic diagram showing the configuration of the reactor, and Figure 3 is an actual photograph of the reactor used in the manufacturing method of sulfur-functionalized biochar with improved adsorption capacity of gaseous mercury according to the present invention, and Figure 4 is a photo showing the improved adsorption capacity of gaseous mercury according to the present invention. This is a schematic diagram of a laboratory-scale system for testing the mercury adsorption performance of the sulfur-functionalized biochar, and Figure 5 is a mercury adsorption curve of the sulfur-functionalized biochar with improved gaseous mercury adsorption capacity according to the present invention.

The present invention relates to a sulfur-functionalized biochar for adsorption and removal of gaseous mercury and a method for manufacturing the same. More specifically, the sulfur-functionalized biochar and a method for manufacturing the same improve the adsorption capacity of gaseous mercury by functionalizing the surface of the biochar with sulfur. It's about.

Figure 1 is a flowchart showing a method for producing sulfur-functionalized biochar with improved adsorption capacity of gaseous mercury according to the present invention.

The method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury according to the present invention includes a raw material filling step (S100) of filling the inside of the reactor with biochar and elemental sulfur as raw materials, and purging the inside of the reactor filled with the raw materials with an inert gas. It includes a purging step (S200) and an activation step (S300) of preventing air inflow into the purged reactor and activating the raw materials by heat treatment.

In the raw material filling step (S100), biochar and elemental sulfur, which are raw materials, are filled inside the reactor.

Figure 2 shows an example of a reactor used in the method of producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury according to the present invention.

The reactor 1 uses a batch reactor, and the material of the reactor can be stainless steel, which has strong heat resistance and chemical resistance.

In detail, the reactor (1) includes a housing (10) in the form of a hollow column, a heating means (20) for supplying heat to the housing, a raw material receiving portion (11) formed in the housing, and both ends of the housing. It is formed and includes an on-off valve 12 to control the inflow of air.

In addition, a gas injection unit 30 for supplying inert gas and fluid is formed on one side of the reactor, and the inflow of the inert gas and fluid passing through the gas injection unit is controlled by opening and closing the on-off valve of the reactor. .

The housing 10 may be provided in the shape of either a cylinder or a polygonal column. Preferably, a cylinder may be used to ensure uniform heat transfer and fluid flow.

The raw material receiving portion 11 is a raw material receiving space that accommodates and fixes the raw material, and the raw material receiving portion is formed by being partitioned by quartz wool provided at both ends.

The elemental sulfur is solid alpha-sulfur (alpha-S) having a purity of 98% or more, preferably 99% or more, and combines with biochar to improve mercury adsorption capacity. At this time, the elemental sulfur may have an average particle size of 1 to 500 ㎛.

In the raw material filling step (S100), elemental sulfur is charged at 1 to 10% by weight based on 100% of the total weight of the sulfur-functionalized biochar, preferably, elemental sulfur is charged at 3 to 7% by weight, and more preferably, Filled with 4 to 6% by weight.

If the elemental sulfur is added in less than 1% by weight, it is difficult to expect improvement in the mercury adsorption characteristics, and if the elemental sulfur is added in excess of 10% by weight, the increase in mercury adsorption compared to the amount added is small and the specific surface area of the biochar becomes small. It is desirable not to exceed the weight range.

In the raw material filling step (S100), prior to filling the raw materials in the reactor, biochar and elemental sulfur can be measured, mixed uniformly using a mixing means, and then introduced into the raw material receiving part of the reactor.

The biochar is a solid produced by carbonizing biomass at 400 to 700° C. under limited oxygen conditions, and the biochar contains carbon (C) as its main component.

The biomass may include at least one of rice husk, grain stalks, wood chips, mushroom waste medium, and fruit- and vegetable-derived waste. Specifically, the grain stalks include at least any one of rice straw, red pepper stalks, bean stalks, and perilla stalks. It may include one, and the waste derived from fruits and vegetables may include at least one of pear trimmings and apple trimmings.

The biochar has an average particle diameter of 1 to 800 ㎛, an average pore size of 1 to 50 nm, a porosity of 40 to 70%, a cation exchange capacity (CEC) of 30 to 100 cmol/kg, and a pH of 8 to 11. You can use something that has .

In the purging step (S200), the inside of the reactor filled with raw materials is purged with an inert gas to prevent the generation of functional groups unnecessary for the reaction in the activation step, which is a post-process.

There are various types of surface functional groups such as carbonyl, phenol, carboxyl, and quinone groups on the surface of biochar. The presence of these surface functional groups is not only a sulfide functional group that is advantageous for the adsorption of elemental mercury, but also a sulfide functional group that is advantageous for the adsorption of elemental mercury. Functional groups are also created at the same time, which ultimately affects the mercury adsorption capacity.

Accordingly, by purging under an inert gas before functionalizing the surface of biochar with elemental sulfur, it is possible to suppress the generation of functional groups other than the sulphide functional group, which is advantageous for the adsorption of mercury.

By continuously flowing an inert gas to stabilize the surface-modified activated carbon and sufficiently mixing it with elemental sulfur to react at high temperature, the functional groups present on the surface can be selectively functionalized in the form of -S functional groups.

There may be residual physically adsorbed impurities and gas components inside the reactor and raw materials, and by purging the inside of the reactor with an inert gas to remove gas components and impurities unnecessary for the reaction, reaction efficiency can be improved in the activation step, which is a post-process. It becomes possible.

The inert gas is a chemically inert or low-reactivity gas, and may be one or more selected from the group consisting of nitrogen (N ₂ ), argon (Ar), helium (He), and neon (Ne).

In the purging step (S200), inert gas may be supplied for 30 to 240 minutes, preferably 45 to 90 minutes.

In the activation step (S300), the inflow of air into the purged reactor is prevented and the raw materials are activated by heat treatment.

In the activation step (S300), after purging, the valves provided at both ends of the reactor are turned off and both ends are blocked to block the inflow of external impurities and gases, thereby preventing the generation of unwanted functional groups during the reaction.

In the activation step (S300), the temperature is raised from room temperature (20 to 25°C) to 250 to 400°C at a rate of 5 to 15°C/min and maintained for 3 to 6 hours. Through this process, sulfur is removed from the surface of biochar. Functionalization occurs and the adsorption capacity of mercury improves.

Meanwhile, in the activation step (S300), biochar and elemental sulfur react to form sulfur-functionalized biochar, and at the same time, gaseous sulfur compounds (SO ₂ , H ₂ S) are removed from the sulfur-functionalized biochar under a high temperature process. This may occur.

In the activation step (S300) according to the present invention, since the reactor is formed in a batch manner, the gaseous sulfur compounds removed from the sulfur-functionalized biochar, which is a reactant, are present in the reactor and are repeatedly re-adsorbed into the sulfur-functionalized biochar, making sulfur functionalization more efficient. Biochar can be formed.

As another example of the activation step (S300), there may be a rest period in which heat supply is temporarily stopped to induce re-adsorption of gaseous sulfur compounds removed from the sulfur-functionalized biochar, which is a reactant. By stopping the heat supply, gaseous sulfur compounds can be further induced to re-adsorb to the reactants.

The rest period may be performed 1 to 3 times in a section of 50 to 80% of the total activation process time, and the heat supply may be stopped, but the rest period may be performed within a range that does not fall below 80% of the maximum temperature. Within the resting period and temperature range, the ability to form reactants and induce re-adsorption of gaseous sulfur compounds is excellent.

Specifically, if the activation step is performed for a total of 5 hours, the rest period can be held 1 to 3 times at 2.5 to 4 hours after heating, and if the maximum set temperature is 300 ℃, the temperature inside the reactor does not fall below 240 ℃. A resting period is performed within the temperature range, and the temperature is heated again to the maximum set temperature of 300°C at a temperature increase rate of 5 to 15°C/min.

The method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury according to the present invention includes an oxygen loading step of forming surface functional groups on biochar by supplying oxygen after the purging step (S200) and before performing the activation step (S300). (S250) may be further included.

In the oxygen loading step (S250), oxygen is supplied to increase the specific surface area of biochar, thereby improving the introduction of sulfur functional groups in the subsequent activation step (S300).

In the oxygen loading step (S250), oxygen can be supplied at 1 to 10% by weight, preferably at 3 to 7% by weight, based on 100% of the total weight of the sulfur-functionalized biochar.

Since the reactor is formed in a batch manner, the content of oxygen loaded into the biochar can be controlled by supplying oxygen and turning off the valve, considering the reactor volume and oxygen concentration.

Hereinafter, the sulfur-functionalized biochar for adsorption and removal of gaseous mercury according to the present invention will be described. The sulfur-functionalized biochar for adsorption and removal of gaseous mercury according to the present invention is manufactured by the method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury described above.

Sulfur-functionalized biochar for adsorption and removal of gaseous mercury improves the adsorption performance for mercury by modifying the surface of the biochar with sulfur, and minimizes sulfur loss by inducing re-adsorption of sulfur removed from the reactant during the activation process to about 65 to 60%. A yield of 83% can be obtained, which is more efficient than the conventional sulfur functionalization method.

Hereinafter, the present invention will be described in detail below with reference to a preferred embodiment. However, the following examples are intended to specifically illustrate the present invention and are not limited thereto.

1. Preparation of raw materials

Rice husk was prepared with biochar. The prepared rice husk was washed three times with distilled water, the moisture was removed, and it was dried at 60°C for 72 hours using a drying oven. The dried rice husk was placed in an electric furnace and carbonized under limited oxygen conditions. Biochar was produced by heating the rice husk from 20°C to a maximum temperature of 400-500°C at 10°C per minute and carbonizing it for 2 hours at the maximum temperature. Afterwards, it was stored in a desiccator for 36 hours and left to cool. Afterwards, it was crushed and sieved to obtain biochar particles with an average particle size of 550 ㎛, which were used in the experiment.

Elemental sulfur was used from Aldrich with a purity of 99.998%.

2. Reaction device

The reaction device was configured as shown in Figure 3. A batch reactor was used to prevent loss of gaseous sulfur compounds (SO ₂ , H ₂ S) and induce re-adsorption. The material of the reactor was stainless steel, which does not deform even at high temperatures and has strong chemical resistance, and a cylindrical reactor was prepared for uniform heat transfer.

Since unwanted functional groups may be generated due to the inflow of atmospheric air, valves were installed on both sides of the reactor to block the gas flow. At this time, the LOK type fitting was used to make it easy to fasten and withstand high pressure. A gas inlet is provided on one side to supply gas during nitrogen purging and oxygen supply.

3. Experimental method

Elemental sulfur (not added, 1 wt%, 3 wt%, 5 wt%) and biochar were mixed and then charged into the reactor.

To prevent the formation of unnecessary functional groups, it was purged with N ₂ gas for 1 hour. After purging, the gas flow was blocked using valves located on both sides of the reactor to prevent the inflow of unwanted gas components into the atmosphere.

The mixture of biochar and elemental sulfur was surface modified for 5 hours by raising the temperature from 20°C at room temperature to 300°C at 10°C per minute.

6 wt% of oxygen was supplied to check the amount of mercury adsorption, component analysis, and specific surface area according to the oxygen loading of the mixture of biochar and elemental sulfur. Afterwards, activation was performed under the same conditions as the sample without oxygen loading.

In addition, in order to check the re-adsorption characteristics of gaseous sulfur compounds depending on the presence or absence of a rest period during the activation process, the heat supply was briefly stopped 3 hours after heating, and when the internal temperature of the reactor reached 260°C, the temperature was increased at 10°C/min. It was heated to 300°C at a temperature increase rate of . At this time, the amount of mercury adsorption and sulfur content were confirmed with and without oxygen supply (not supplied, 6 wt%) using a sample with elemental sulfur content (5 wt%).

4. System design and test results for mercury adsorption performance testing

As shown in Figure 4, a laboratory-scale system was constructed to test mercury adsorption performance, and the mercury adsorption amount, component analysis, and specific surface area of the sulfur-functionalized biochar were confirmed.

The experimental conditions for measuring the amount of mercury adsorption are as follows.

*Total flow rate: 100 ㎤/min

*Mercury supply: 362 ug/㎥

*Adsorption temperature: 80℃

*Mercury species: Hg ⁰

*Experiment ends after C/C ₀ reaches 80%

Table 1 below shows the results of component analysis and specific surface area measurement of the produced sulfur-functionalized biochar.

Oxygen loading
_O2 -wt% Elemental sulfur content
(S-wt%) Composition (wt%) specific surface area
S _BET ( ^m2 /g) C H N S O 0 0 55.84 1.948 3.06 0.072 1.138 4.979 One 55.13 1.924 3.04 0.647 0.784 3.284 3 54.49 1.873 3.08 1.978 1.458 2.763 5 53 1.831 3.02 4.152 2.114 2.549 6 5 53.41 1.723 3.01 5.716 3.5 3.861

As the sulfur content of sulfur-functionalized biochar increased, the specific surface area tended to decrease, but under the same sulfur content conditions, the specific surface area of the oxygen loading group increased by about 34% compared to the untreated group. Through this, it was expected that oxygen treatment could improve the specific surface area of sulfur-functionalized biochar and ultimately control the amount of mercury adsorption.

In addition, in the composition analysis results, 0.072 wt% of sulfur measured in the group without elemental sulfur (0 wt%) was due to a trace amount of sulfur present in biochar, and the sulfur content measured in the group with 5 wt% elemental sulfur was 4.152 wt. It was confirmed as %, and the result shows more than 4% even considering the trace amount of sulfur (0.072wt%) present in the biochar itself. This means that the loss of elemental sulfur is only less than 1wt%, which means that the loss of elemental sulfur is minimized while biochar is used. It has been shown that it is possible to introduce sulfur-based technology into tea.

This was believed to be due to the fact that sulfur loss can be minimized because the sulfur removed from the biochar undergoing sulfur functionalization is repeatedly re-adsorbed into the biochar in the batch reactor.

Table 2 below shows the mercury adsorption amount (C/C ₀ ) of the produced sulfur-functionalized biochar until it reaches 80%. Figure 5 shows the mercury adsorption curve of the produced sulfur-functionalized biochar.

Oxygen loading (O ₂ -wt%) Elemental sulfur content
(S-wt%) Concentration
(ug/g) 0 0 0.424 One 3.708 3 28.374 5 168.436 6 5 75.472

The results showed that the amount of mercury adsorption increased as the content of elemental sulfur increased, and the amount of mercury adsorption was higher in the untreated group than in the oxygen loading group.

The decrease in mercury adsorption in the oxygen loading group was determined to be due to the formation of functional groups (phenol, carboxyl, etc.) on the surface of biochar that are unfavorable to mercury adsorption due to oxygen. In this way, oxygen loading may slightly reduce the amount of mercury adsorption, but as shown in Table 1, it was judged that an appropriate amount of oxygen loading would be required because it could increase the specific surface area and the introduction characteristics of sulfur functional groups.

In addition, the re-adsorption characteristics of gaseous sulfur compounds depending on the presence or absence of a rest period during the activation process are shown in Table 3 below.

Oxygen loading
_O2 -wt% Elemental sulfur addition amount (S-wt%) Presence or absence of resting period S component (wt%) Concentration
(ug/g) 0 5 doesn't exist. 4.152 168.436 0 5 has exist. 4.254 172.123 6 5 doesn't exist. 5.716 75.472 6 5 has exist. 5.806 81.664

As a result, it was confirmed that more sulfur content was detected in the dormant group in the activation stage, and the amount of mercury adsorption was also superior. This was judged to be due to the fact that the resting period can further induce re-adsorption of gaseous sulfur compounds.

As described above, the present invention has been described with a focus on preferred embodiments with reference to the accompanying drawings, but within the scope of those skilled in the art in the technical field to which the present invention pertains without departing from the technical spirit and scope described in the claims of the present invention. The present invention can be implemented with various modifications or modifications. Accordingly, the scope of the present invention should be construed by the appended claims to include examples of many such modifications.

1: reactor
10: housing
20: Heating means
11: Raw material receiving part
12: on-off valve
30: gas injection part

Claims (5)

A raw material filling step (S100) in which biochar and elemental sulfur, which are raw materials, are filled inside the reactor;
A purging step (S200) of purging the inside of the reactor filled with raw materials with an inert gas;
An activation step (S300) of preventing air inflow into the purged reactor and activating the raw materials by heat treatment.
Method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury.
According to clause 1,
In the raw material filling step (S100),
Characterized by filling 1 to 10% by weight of elemental sulfur
Method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury.
According to clause 1,
In the activation step (S300),
Characterized in that the gaseous sulfur desorbed from the reactants during the activation reaction is re-adsorbed to functionalize the biochar with sulfur.
Method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury.
According to clause 1,
In the activation step (S300),
Characterized by raising the temperature from room temperature to 250 to 400 ° C. at a temperature increase rate of 5 to 15 ° C./min and maintaining it for 3 to 6 hours.
Method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury.
Sulfur-functionalized biochar for adsorption and removal of gaseous mercury produced by the method for producing sulfur-functionalized biochar for adsorption and removal of gaseous mercury according to any one of claims 1 to 4.