KR102271800B1 - Preparation method of glycerol-impregnated modified hybrid coal - Google Patents

Abstract

The present invention impregnates the low-grade coal with a mixed solution of glycerol and sulfuric acid generated as a by-product in the biodiesel process to prevent the glycerol impregnated in the coal from volatilizing even when the coal is torrefied at a temperature higher than the volatilization temperature of glycerol. It relates to a method for producing a modified hybrid coal impregnated with glycerol capable of producing an improved hybrid coal.
The present invention, preparing the coal (S10) and; Mixing the glycerol and sulfuric acid solution (S20) and; Impregnating the coal in the glycerol sulfuric acid mixture (S30) and; drying the coal impregnated with the glycerol-sulfuric acid mixture (S40); and torrefied the dried coal under nitrogen condition (S50).

Description

Method for producing glycerol-impregnated modified hybrid coal {Preparation method of glycerol-impregnated modified hybrid coal}

The present invention relates to hybrid coal and a method for producing the same, and more particularly, by impregnating a low-grade coal with a mixed solution of glycerol and sulfuric acid generated as a by-product in the biodiesel process, even if the torrefaction process of coal is performed above the volatilization temperature of glycerol. It relates to a method for producing a modified hybrid coal impregnated with glycerol, capable of producing hybrid coal with a further improved calorific value by preventing the glycerol impregnated in the coal from volatilizing.

Recently, interest in coal as an energy source is rising again due to reasons such as continuously rising oil prices and distrust in the stability of nuclear energy. However, coal produces the largest amount of carbon dioxide among fossil fuels, so it is a weak energy source considering global warming. Therefore, one of the current global issues as an energy source is the use and dissemination of new and renewable energy, which reduces carbon dioxide emissions compared to the existing fossil fuels such as petroleum and coal, so that it can respond to global warming and climate change. Because it is in the spotlight as an energy source. However, in the case of using renewable energy sources such as solar power or wind power for power generation or heating in Korea, epoch-making use and dissemination were limited due to the difference in power generation cost compared to fossil fuels.

In Korea, as well as the depletion of fossil fuels and the rise of greenhouse gas reduction in response to the international treaty on climate change, the mandatory quota system for renewable energy began to be discussed. Since 2012, the mandatory quota system for renewable energy [Renewable Portfolio Standard (RPS)] has been introduced. It is true that the introduction puts a burden on energy providers. Accordingly, power generation companies are attempting Integrated Gasification Combined Cycle (IGCC) and biomass co-firing as an effort to reduce carbon dioxide emissions from coal, but IGCC cannot use existing coal-fired power generation facilities. It requires a huge construction cost of about 1.3 trillion won per unit, and it is a technology that additionally needs to install a carbon capture and storage facility [Carbon Capture and Storage (CCS)] for carbon dioxide treatment, which is very economically burdensome. And in the case of biomass co-firing, there is a problem such as a decrease in power generation efficiency due to combustion of biomass having a relatively low calorific value compared to coal.

In addition, as the supply of high-grade coal such as bituminous coal has recently become unstable, power generation companies inevitably have no choice but to use low-grade coal. Due to the high moisture content of low-grade coal, co-firing low-grade coal results in impaired power generation performance. , there is a problem that the amount of CO2 generated increases by more than 20% compared to high-grade coal. Therefore, considering that such low-grade coal occupies about 50% of the total coal reserves, the high value-added of low-grade coal is a necessary technology for efficient use of low-grade coal.

Accordingly, research on low coal drying such as simple drying of low coal, high pressure drying using hot water, or drying using high temperature organic solvent is being actively conducted, but there is a problem that the process is complicated and moisture is re-adsorbed after drying to generate power. There is still the problem of low efficiency. In addition, there is a problem in that spontaneous ignition occurs as moisture is re-adsorbed to the dried coal, and thus stored coal is lost.

In addition, a technique for high-quality reforming of low-grade coal by a method of attaching tar in a biomass dry distillation product to coal is also known, but the re-adsorption of moisture has not been evaluated.

On the other hand, recently, attention has been focused on the technology of recycling glycerol obtained as a by-product in the biodiesel production process as a resource, but in order to recycle such glycerol and convert it into a high value-added resource, there is a difficulty in securing a high yield of the desired compound, There is a disadvantage in that the process cost is high because a high-pressure reaction condition is required. Therefore, an attempt has been made to recycle glycerol obtained as a by-product in the biodiesel production process that does not require high yield for specific compounds and does not require an expensive production process. An example of manufacturing a solid fuel by heating and drying is known, but this is formed by simply mixing and heating and drying organic sludge and waste glycerol, and only considers the calorific value according to the moisture content during drying. The hydrophobicity of the surface was also not evaluated.

Accordingly, in Korea Patent Registration No. 10-1210928, coal is impregnated with glycerol to produce hybrid coal with high calorific value. However, in order to increase the calorific value of low-grade coal, a torrefaction process is required, but the torrefaction process requires volatilization of glycerol. Because it was done above the temperature, there was no choice but to simply dry the glycerol.

The problem to be solved by the present invention is that the glycerol impregnated in the coal is volatilized even when the coal is torrefied at a temperature higher than the volatilization temperature of glycerol by impregnating the low-grade coal with a mixture of glycerol and sulfuric acid generated as a by-product in the biodiesel process An object of the present invention is to provide a method for producing a modified hybrid coal impregnated with glycerol capable of producing hybrid coal with a further improved calorific value by preventing it.

A method for producing a modified hybrid coal impregnated with glycerol according to the present invention, the step of preparing the coal (S10); Mixing the glycerol and sulfuric acid solution (S20) and; Impregnating the coal in the glycerol sulfuric acid mixture (S30) and; drying the coal impregnated with the glycerol-sulfuric acid mixture (S40); and torrefied the dried coal under nitrogen condition (S50).

Preferably, in the step of mixing, it is characterized in that glycerol is impregnated into a plurality of pores of the coal.

Preferably, the mixed solution of glycerol and sulfuric acid solution is characterized in that 5 to 80% by weight, respectively, based on coal.

Preferably, the mixing ratio of glycerol and sulfuric acid solution is characterized in that the weight ratio of 1:0.1 to 1:0.5.

Preferably, the drying step of the coal is characterized in that it is made at 80 ~ 120 ℃.

Preferably, the torrefaction step of coal is characterized in that it is made at 200 ~ 250 ℃.

Preferably, it characterized in that it further comprises a step (S60) of washing and drying torrefied coal.

According to the present invention, in order to increase the calorific value by sulfuric acid used together with glycerol in coal, there is an effect that can prevent glycerol from volatilizing even when the torrefaction process is performed above the volatilization temperature of glycerol.

In addition, the hybrid coal impregnated with carbonized glycerol has the advantage of emitting less unburned carbon because multi-stage combustion does not occur even if energy efficiency is increased due to the stable combustion characteristic of two-in-one fuel. have.

In addition, the hybrid coal according to the present invention can promote the utilization of the low-grade coal by replacing the high-grade coal by increasing the high calorific value of the low-grade coal.

In addition, since glycerol generated as a by-product in the biodiesel process is used, there is an improved effect of increasing energy efficiency while filling the mandatory renewable energy quota system.

1 is a flowchart for the manufacturing process of glycerol-impregnated reformed hybrid coal according to the present invention.
2 is a conceptual diagram of a reformed hybrid coal impregnated with glycerol according to the present invention.
Figure 3 is a graph of combustion characteristics of hybrid coal torrefied after impregnation with glycerol according to the present invention.
4 is an activation energy graph of Example 1 and Comparative Example according to the present invention.
5 is a UBC emission graph of Examples 1, 2, 3 and Comparative Example according to the present invention.
6 is a hydrogen sulfide emission graph of Examples 1, 2, 3 and Comparative Example according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Hereinafter, according to the present invention, by impregnating the hydrophilic pores and hydrophilic surface of raw coal or dry coal containing moisture with glycerol, a by-product of the biodiesel production process, and drying it to make it hydrophobic, re-adsorption of moisture is significantly suppressed even after drying. A method for producing a high calorific value hybrid coal and a technology for upgrading a low-grade coal from a high calorific value hybrid coal impregnated with glycerol produced thereby will be described in detail with the accompanying drawings.

1 and 2, the method for producing hybrid coal according to the present invention includes the steps of preparing coal (S10); Mixing the glycerol and sulfuric acid solution (S20) and; Impregnating the coal in the glycerol sulfuric acid mixture (S30) and; drying the coal impregnated with the glycerol-sulfuric acid mixture (S40); and torrefied the dried coal under nitrogen condition (S50). At this time, the step of washing and drying torrefied coal (S60) may be further included.

The coal of step S10 has a plurality of pores formed on the surface, and peat, lignite, sub-bituminous coal, bituminous coal or anthracite coal may be used, but is not limited thereto. In the present invention, it is preferable to use low-grade coal with a high moisture content, for example, 20 to 60% by weight, such as brown coal and sub-bituminous coal, but is not limited thereto. In this case, it is preferable to remove moisture from the coal in the preparation stage of the coal.

The glycerol sulfuric acid mixture of steps S20 and S30 forms a paste while impregnating with coal. Glycerol is a liquid substance at room temperature that is generated as a by-product in the biodiesel process and is impregnated into hydrophilic pores and hydrophilic surfaces of coal. The hydrophilic surface of coal may be an ash surface of coal or a surface of fixed carbon and volatile matter of coal having -COOH (carboxyl group), -NH2 (amine group), -OH (hydroxyl group) functional groups. The glycerol is preferably glycerol obtained as a by-product in the production process of biomass, but glycerol obtained conventionally by a chemical or biological method may be used.

It is preferable to add 5 to 80 wt% of the glycerol sulfuric acid mixture based on the weight of the coal. At this time, if the amount of glycerol added is less than 5% by weight, the amount of glycerol penetrating into the hydrophilic pores and hydrophilic surface of coal is insignificant, so that the hydrophilic pores and hydrophilic surface of coal cannot be sufficiently impregnated. It is difficult to modify, and when it exceeds 80% by weight, it is difficult to obtain a paste property and the workability is deteriorated.

Sulfuric acid is used so that glycerol impregnated in coal is not volatilized in the torrefaction step above the volatilization temperature of glycerol. At this time, the mixing amount of sulfuric acid with respect to glycerol is characterized in that it is mixed in a weight ratio of 1:0.1 to 1:0.5. When the mixing ratio of sulfuric acid is less than 0.1 weight ratio, it becomes difficult to prevent volatilization of glycerol during carbonization, and when the weight ratio of the mixing amount is 5 or more, a large amount of sulfuric acid is used to generate contaminants.

When the coal is impregnated with the glycerol-sulfuric acid mixture in step S40, the glycerol-sulfuric acid mixture is dried below the volatilization temperature of glycerol so as to be coated on the hydrophilic pores and hydrophilic surface of the coal. The drying temperature is preferably 80 ~ 120 ℃. By the drying process, the glycerol-sulfuric acid mixture adheres to the hydrophilic pores and the hydrophilic surface to form a coating layer, thereby reducing the re-adsorption of moisture.

In step S50, if the glycerol-sulfuric acid mixture adheres to the hydrophilic pores and hydrophilic surface of the coal through the drying process of the coal, it is torrefied by heating at 200 to 250° C. in a nitrogen atmosphere. At this time, even if the torrefaction temperature by the sulfuric acid mixed with glycerol proceeds at 180-200° C., which is the volatilization temperature of glycerol, the glycerol does not volatilize and remains in the hydrophilic pores and hydrophilic surface of the coal. As shown in FIG. 2 , a new functional group (C=C) is generated in the hydrophilic pores of coal and glycerol adhered to the hydrophilic surface through this torrefaction process, and the hydrophilic functional groups are removed. Accordingly, it is possible to lower the reabsorption rate of moisture, thereby maintaining the calorific value of coal, reducing costs during transportation and storage, and preventing spontaneous combustion due to moisture.

On the other hand, through the process of washing and drying the torrefied coal in step S60, sulfuric acid remaining in the torrefied coal may be additionally removed to further reduce the generation of sulfur oxides.

After going through the torrefaction process of coal through step S50 or step S60, high calorific value hybrid coal is manufactured by molding it into pellets or the like.

The hybrid coal impregnated with glycerol and subjected to the torrefaction process prepared by the above manufacturing method exhibits stable combustion characteristics of a two-in-one fuel. For this reason, the hybrid coal according to the present invention has a high calorific value and can increase energy efficiency higher than about 1,100 kcal/kg compared to raw coal.

Accordingly, since the hybrid coal according to the present invention can be changed to high-grade coal by using low-grade coal, it is possible to promote the use of low-grade coal.

Hereinafter, specific examples will be described in detail.

(Examples 1-3, Comparative Examples 1-2)

100 g of dried sub-bituminous coal (BC) having a particle size of 75 μm or less was mixed with a mixed solution of 10 g of glycerol and 1 g of sulfuric acid, and 10% of glycerol was impregnated into the lignite. Then, after drying at 120° C. for 6 hours, the torrefaction process was performed at 250° C. for 1 hour under a nitrogen atmosphere to prepare the modified hybrid coal impregnated with glycerol of Example 1 (BC-10).

In Example 2, using a mixture of 20 g of glycerol and 2 g of sulfuric acid under the same conditions as in Example 1, lignite was impregnated with 20% of glycerol to prepare a modified hybrid coal impregnated with glycerol (BC-20), Example 3 was glycerol Using a mixture of 30 g and 3 g of sulfuric acid, lignite was impregnated with 30% glycerol to prepare glycerol-impregnated reformed hybrid coal (BC-30).

In Example 4, the modified hybrid coal (BC-10) impregnated with glycerol of Example 1 was washed in water and dried at 120° C. for 6 hours ((BC-10-washing).

In Comparative Example 1, dried lignite was used (BC-D).

(Examples 5-7, Comparative Example 2)

In Examples 4-7, glycerol-impregnated reformed hybrid coal was prepared using lignite (KC) under the same conditions as Examples 1-3 (KC-10, KC-20, KC-30).

In Comparative Example 2, dried sub-bituminous coal was used as it was (KC-D)

<Confirmation of combustion characteristics of glycerol>

After the glycerol of Examples 1 to 7 and Comparative Examples 1 to 2 was impregnated, the combustion temperature of the torrefied hybrid coal and the combustion characteristics of the fabric were measured and shown in FIG. 3 .

As shown in Figure 3, glycerol is volatilized at 200 ℃, but after glycerol is impregnated in hybrid coal torrefied, the combustion pattern of glycerol disappears and it can be confirmed that it is similar to the combustion pattern of conventional coal.

<Confirmation of pore characteristics>

It is a graph showing the pore size distribution of the torrefied hybrid coal and the simple dry raw coal of Comparative Example 1 after being impregnated with glycerol of Examples 1 to 3.

BET specific surface area
(m ² /g) pore area
(m ² /g) pore surface area
(m ² /g) gun skin
(cm ³ /g) pore volume
(cm ³ /g) Comparative Example 1
(BC-D) 12.04 1.84 10.2 0.0214 0.000694 Example 1
(BC-10) 0.68 0.55 0.95 0.0032 0.000212 Example 2
(BC-20) 0.61 0.33 0.34 0.0027 0.000124 Example 3
(BC-30) 0.49 0.21 0.27 0.0018 0.000089

As shown in Table 1, in the hybrid coal torrefied after impregnation with glycerol of Examples 1 to 3, glycerol was impregnated into the pores of the coal, so that the specific surface area, pore area, etc. were significantly reduced compared to the raw coal of Comparative Example 2 It can be confirmed that the activation energy has been changed. <Confirmation of activation energy>

After the glycerol of Example 1 was impregnated, the activation energy of the torrefied hybrid coal and the raw coal of Comparative Example 1 was confirmed and shown in FIG. 4 .

As shown in Figure 4, although the activation energy of the raw coal of Comparative Example 1 was 9.68 Kcal/mol, it can be confirmed that the torrefied hybrid coal after impregnation with glycerol of Example 1 was lowered to 7.44 Kcal/mol. Fast ignition is achieved by such low activation energy, and this rapid ignition can reduce UBC (Unburned Carbon).

<Check UBC emission>

After the glycerol of Examples 1, 2, and 3 was impregnated, the torrefied hybrid coal and the raw coal of Comparative Example 1 were burned to confirm the emission of Unburned Carbon (UBC), which is shown in the graph of FIG. 5 .

As shown in FIG. 5 , the UBC emitted during combustion was 37.87% in the raw coal of Comparative Example 1, but 27.44% 29.99%, 24.61% in the hybrid coal that was torrefied after the glycerol of Examples 1, 2, and 3 was impregnated, respectively. It can be seen that the lowered This low UBC (Unburned Carbon) was found to be due to the two-in-one fuel combustion characteristics of the torrefied hybrid coal after impregnation with glycerol and the rapid ignition. In addition, it was confirmed that the more the amount of glycerol impregnated, the lower the UBC emission.

<Check moisture re-adsorption rate>

After the glycerol of Examples 1, 2, and 3 was impregnated, the torrefied hybrid coal and raw coal were soaked in excess water and stirred for 10 minutes to allow water to be adsorbed into the pores, then filtered for 20 minutes to remove external moisture and weighed. measure The coal from which external moisture has been removed is dried again in an oven at 105° C. for 12 hours to remove moisture in the pores. The moisture resorption rate was calculated as follows and shown in Table 2.

Moisture resorption rate (wt%) = (Cwet - Cdry)/Cwet * 100 [Cwet is the weight of coal after filtration, Cdry is the weight of coal after oven drying]

Comparative Example 1
(BC-D) Example 1
(BC-10) Example 2
(BC-20) Example 3
(BC-30) water reabsorption rate 53.89% 12.86% 10.31% 8.55%

As shown in Table 2, in the raw coal of Comparative Example 1, the moisture reabsorption rate was 53.89%, but in the hybrid coal torrefied after impregnation with glycerol of Examples 1, 2, and 3, the moisture reabsorption rate was 12.86%, 10.31% , it was confirmed that it was lowered to 8.55%, respectively. This characteristic can be confirmed that the torrefaction process interferes with the moisture adsorption of coal due to the creation of new functional groups (C = C) in glycerol and the removal of hydrophilic functional groups. <Confirmation of Sulfur Oxide Generation>

After being impregnated with glycerol of Example 1, the torrefied hybrid coal (BC-10), the washed hybrid coal of Example 4 (BC-10-washing) and the raw coal of Comparative Example 1 (BC-D) were burned to sulfuric acid The discharge of the cargo was confirmed and shown in the graph of FIG. 6 .

As shown in FIG. 6 , in the hybrid coal torrefied after impregnation with glycerol of Example 1, SOX emissions did not significantly increase despite the addition of sulfuric acid during the manufacturing process, and when washed as in Example 4, Comparative Example It was confirmed that the same level of sulfur oxides as the raw coal of No. 1 was emitted.

<Check the calorific value>

The industrial analysis results and calorific value of the hybrid coals impregnated with glycerol of Examples 1 to 7 and the raw coal of Comparative Examples 1 to 4 are shown in Table 3 below.

　 Industry analysis (wt%) factorial
calorific value
(kcal/kg) true calorific value
(kcal/kg) moisture volatile matter ash fixed carbon Comparative Example 1
(BC-D) 18.99 36.35 5.69 38.97 5,023 4,679 Example 1
(BC-10) 2.01 44.64 7.54 45.81 6,095 5,868 Example 2
(BC-20) 1.77 44.44 7.9 45.89 6,208 6,000 Example 3
(BC-30) 0.93 42.82 7.93 48.32 6,281 6,084 Example 4
(BC-10-washing) 6,035 5,803 Comparative Example 2
(KC-D) 31.12 30.18 5.18 33.52 3,754 3,419 Example 5
(KC-10) 0.54 45.32 8.17 45.97 5,520 5,319 Example 6
(KC-20) 0.41 45.21 8.31 46.07 5,617 5,446 Example 7
(KC-30) 0.35 43.49 9.24 46.92 5,710 5,547

As shown in Table 3 above, glycerol-impregnated and torrefied hybrid coals (KC-10, KC-20, KC-30) prepared using the lignite of Examples 1 to 3 of the present invention were mixed with the raw coal of Comparative Example 1. Compared to that, the true calorific value (when the latent heat of evaporation of intrinsic moisture is considered) was about 1,766 ~ 1,956 kcal/kg higher, and it was confirmed that about 1,900 ~ 2,128 kcal/kg was higher in the case of the takeover type calorific value generally used in power plants. . Also, the hybrid coals impregnated with glycerol and torrefied by using the sub-bituminous coals of Examples 4 to 6 (BC-10, BC-20, BC-30) also had a true calorific value of about 1,072 compared to the raw coal of Comparative Example 2 ~ 1258 kcal/kg was higher, and in the case of takeover calorific value commonly used in power plants, it was confirmed that it was about 1,189 ~ 1,124 kcal/kg higher. In addition, it was confirmed that the hybrid coal impregnated with glycerol and washed as in Example 7 ((BC-10-washing) also had a higher calorific value of 1,012 kcal/kg and a higher calorific value of 1,124 kcal/kg. Hybrid coal impregnated with glycerol and torrefied of glycerol has improved calorific value much higher than that of raw coal, and thus can be used with low-grade coal as well as high-grade coal. can be kept remarkably low, and volatile matter and fixed carbon were found to be high.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those of ordinary skill in the art to which the present invention pertains Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

Claims (7)

Preparing coal (S10) and;
Mixing the glycerol and sulfuric acid solution (S20) and;
Impregnating the coal in the glycerol sulfuric acid mixture (S30) and;
drying the coal impregnated with the glycerol-sulfuric acid mixture (S40);
A method for producing a modified hybrid coal impregnated with glycerol, comprising a; torrefoiling the dried coal under nitrogen condition (S50). The method according to claim 1, wherein in the impregnation step, glycerol is impregnated into a plurality of pores of the coal. The method according to claim 1, wherein the mixed solution of glycerol and sulfuric acid solution is in an amount of 5 to 80 wt%, respectively, based on the coal. The method according to claim 3, wherein the mixing ratio of the glycerol and the sulfuric acid solution is 1:0.1 to 1:0.5 by weight. The method according to claim 1, wherein the drying step of the coal is performed at 80 ~ 120 ℃ glycerol-impregnated hybrid coal manufacturing method. The method according to claim 1, wherein the torrefaction of coal is performed at 200-250°C. The method according to claim 1, further comprising the step of washing and drying the torrefied coal (S60).

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