KR101118758B1 - The decomposition method of carbon-dioxide using paper mill sludge - Google Patents

Abstract

The present invention relates to a method for decomposing carbon dioxide using paper sludge, and more particularly, to a method for decomposing carbon dioxide including reacting paper sludge with carbon dioxide.

According to the present invention, it is possible to efficiently decompose carbon dioxide by recycling paper sludge generated after wastewater treatment in a paper mill. In addition, it is possible to prevent global warming by reducing the generation of carbon dioxide, and to ensure recyclability as a circulating resource that can decompose carbon dioxide by using paper sludge.

Paper sludge, global warming, carbon dioxide

Description

The decomposition method of carbon-dioxide using paper mill sludge}

The present invention relates to a method for decomposing carbon dioxide using paper sludge, and more particularly, to a method for decomposing carbon dioxide including reacting paper sludge with carbon dioxide.

In the 21st century, only environmentally friendly energy can survive global environmental regulations. In terms of energy and environment, greenhouse gases are the ones that have the greatest impact on global climate change. Recently, the problem of climate change and warming caused by greenhouse gases has attracted much attention in terms of environmental problems on a global scale, and is trying to solve the problem on a global level. Greenhouse gases include carbon dioxide (CO ₂ ), methane (CH ₄ ), nitrogen dioxide (N ₂ O), freon gases (CFCs), and sulfur hexafluoride (SF ₆ ). Among them, the biggest impact on global warming is carbon dioxide. Atmospheric concentration is about 370 ppm, which contributes more than 55% of global warming. In 2100, carbon dioxide concentration is about 570-970 ppm (carbon dioxide at 1750). Concentrations of 90 to 250% of the concentration of 280 ppm) (Hashimoto, et al., 1999; Choi, et al., 2005]. Korea's energy consumption is ranked 10th in the world, 4th in the world of oil imports, and 9th in carbon dioxide emissions. Although not included in the mandate of the Kyoto Protocol to reduce greenhouse gases to 1990 levels, it is difficult to avoid the reduction obligations during the second mandatory period (2013 to 2017), so a national crisis may be encountered if no countermeasures are taken. Therefore, technologies to reduce carbon dioxide using energy saving and alternative energy sources are being actively developed, reducing carbon dioxide emissions, separating and recovering carbon dioxide from fixed sources, converting to useful chemicals by catalytic chemical immobilization, and biological immobilization of carbon dioxide by microorganisms. In addition, studies on adsorptive separation and hydrogen reduction cracking, which are practically applicable to the source, are underway [Shin, et al., 2002; Kim, et al., 2005; Youssef, et al., 2009].

Although the London Convention on Marine Pollution Prevention was planned to come into effect at the end of 2004, the response period has been secured somewhat due to immaturity of domestic industrial conditions, but the paper, dyeing, leather and pharmaceutical industries, which are major waste management industries, It is in the sphere of influence and is considered a sensitive sector.

Paper sludge, which represents a relatively high amount of process sludge, generated about 1 million tons as of 2006, of which 64% was landfilled after incineration, 17% was discharged from the ocean and 16% was recycled. In the high oil price period, the amount of self-incineration is gradually decreasing due to economic reasons, and the amount of treatment by ocean discharge into the coastal sea where the treatment cost is the least is increasing. However, if ocean emissions are totally banned, existing heat treatment processes and managed landfills will be expensive, adding to the economic burden on related companies. In this situation, the recycling of paper sludge has been considered in various fields such as packaging metal powder additive, harmful gas adsorption aid, cement admixture and carbon dioxide decomposition using iron oxide [Ju, et al., 2003; Yutaka, et al., 1992; Shin, et al., 2003].

In particular, the study of carbon dioxide decomposition utilizing paper sludge has the advantage of recycling the wastes from which the total amount of ocean emissions are generated. In addition, in the case of paper sludge produced by being discharged as a sediment after wastewater treatment, various metal catalysts generally used for treating carbon dioxide are naturally added, and thus, it is highly valuable as a raw material for treating carbon dioxide. However, until now, research on utilization of paper sludge as a raw material for treating carbon dioxide has not been conducted.

Accordingly, the present inventors have made intensive studies to overcome the problems of the prior art, and when the reaction of paper sludge and carbon dioxide to perform carbon dioxide decomposition, it was confirmed that the carbon dioxide is effectively decomposed, and completed the present invention.

Therefore, the main object of the present invention is to provide a method for efficiently decomposing carbon dioxide using paper sludge.

According to an aspect of the present invention, the present invention provides a method for decomposing carbon dioxide comprising reacting paper mill sludge (PMS) with carbon dioxide (CO ₂ ).

In the method of the present invention, the paper sludge is characterized in that the paper sludge generated in the wastewater treatment including the fenton oxidation treatment process of the paper mill. Fenton oxidation is a method that has been used for a long time in the treatment of industrial wastewater to decompose organic matter. The fenton oxidation process is a process of completely oxidizing landfill leachate, organic acid cleaning chemicals, and hardly decomposable organic substances and converting them into final products such as carbon dioxide and water through the process of generating organic acids such as acetic acid, an intermediate product. Fenton oxidation process is applied to oxidize the organic matter contained in the wastewater generated in the paper mill. Fenton treatment sludge generated in this process contains a large amount of iron (Fe).

Paper sludge used in the present invention is the final sludge of the dewatered cake generated after the third wastewater treatment of the paper company located in Banwol-Sihwa Industrial Complex.

In the method of the present invention, the papermaking sludge is a spinel magnetite (Spinel phase magnetite) containing a transition metal such as manganese, chromium, nickel, copper in the iron component. Fe ₃ O ₄ combined with transition metals such as Mn and Cu was synthesized by Masahiro (1993) and Yang (2000) to decompose carbon dioxide decomposition behavior of oxygen-deficient Mn-ferrites and metal-added magnetite. Reported high resolution. The term "oxygen deficiency" is meant to denote a void where oxygen is partially missing. Therefore, since the paper sludge of the present invention contains various transition metals as the spinel-type magnetite, it is determined that sufficient recyclability can be secured for carbon dioxide decomposition.

In the method of the present invention, the method comprises the following steps.

a) drying the paper sludge;

b) filling the dried papermaking sludge into a reactor;

c) injecting hydrogen into the reactor to perform hydrogen reduction;

d) blocking hydrogen injection and injecting carbon dioxide;

e) reacting the paper sludge with carbon dioxide.

In the method of the present invention, the hydrogen injection in step c) is characterized in that the injection for 1 to 5 hours at 100 ~ 300 cc / min. In addition, hydrogen reduction was performed while flowing the hydrogen, and the hydrogen reduction was confirmed by the presence of condensate generated in the water trap apparatus of FIG. 2. When the hydrogen injection is 300 cc / min or more, the flow rate of hydrogen in the reactor is so fast that hydrogen flows only to one side of the reactor, so that hydrogen reduction may not be performed well for the entire sample (paper sludge). In addition, even if the amount of hydrogen is too small compared to the sample amount, the hydrogen reduction reaction may not be properly performed.

In the method of the present invention, the hydrogen reduction conditions of step c) is characterized in that carried out in a temperature range of 250 ~ 450 ℃. When hydrogen reduction is performed under conditions outside the temperature range, hydrogen may not flow smoothly in the reactor, and hydrogen reduction may not be performed properly.

In the method of the present invention, the carbon dioxide injection in step d) is characterized in that the injection until the pressure inside the reactor is 10 ~ 20 psi (pound / inch ² ). When carbon dioxide is injected such that the pressure inside the reactor is within the above range, oxygen is filled in the oxygen-deficient part while carbon dioxide is decomposed, and carbon is adsorbed on the surface. On the other hand, when injecting carbon dioxide such that the pressure inside the reactor is less than 10 psi or more than 20 psi, the reaction between the paper sludge and carbon dioxide may not be smoothly performed.

In the method of the present invention, the carbon dioxide decomposition conditions of step e) is characterized in that carried out at a temperature range of 250 ~ 450 ℃. The temperature range is the same as the temperature condition at the time of hydrogen reduction. In addition, the temperature range is confirmed that before the carbon dioxide decomposition using papermaking sludge, carbon dioxide decomposition occurs first with iron oxide (Fe ₃ O ₄ ) occurs at about 400 ℃, and other metals (Cu , Zn, etc.) was added, and after confirming that carbon dioxide decomposition occurred at about 350 ℃, it was set based on this. Therefore, in the present invention, the experiment was performed by setting the temperature range of 250 ~ 450 ℃ based on 350 ℃.

More preferably, it is carried out at 50 ℃ interval in the above temperature range. Carbon dioxide decomposition conditions of the present invention are shown in Table 1 below.

[Table 1. Carbon Dioxide Decomposition Conditions]

Hereinafter, the present invention will be described in more detail with reference to Examples. These embodiments are only for illustrating the present invention, and thus the scope of the present invention is not construed as being limited by these embodiments.

Example 1 Drying and Storage of Paper Sludge (PMS)

Paper mill sludge (PMS) used in the present invention is the final sludge of the dewatered cake produced after the third wastewater treatment of the paper company located in Banwol-Sihwa Industrial Complex. After drying the final sludge for 24 hours at 105 ℃ in a hot air dryer, was prepared in a fine powder state using a bowl of agate mortar was used to store in a desiccator.

Example 2 Analysis of Physical Properties of Paper Sludge (PMS)

2-1. Particle size analysis

To investigate the physicochemical properties of paper sludge, the average particle size and particle size distribution of paper sludge were measured using a particle size analyzer (SALD-2001, Shimadzu, Japan). The measurement results are shown in FIG. 1.

As shown in Figure 1, the average particle size of the papermaking sludge used for the decomposition of carbon dioxide of the present invention was confirmed to be about 8 μm.

2-2. Analysis of three components (water (WC), ash (Ash), volatile solids (VS)) and organic matter content (OMC)

Most sludge contains organic matter and causes secondary environmental pollution such as bad smell when dried and stored. In order to recycle the paper sludge used in the present invention, three components and organic matter contents were analyzed using a waste process test method. The component may be divided into a value considering the physical composition of only the combustible component and a value considering the physical composition including the non-flammable component. The organic matter content was calculated by using the following formula 1 by ignition loss of paper sludge. The measurement results are shown in Table 2.

&Quot; (1) "

Ma: PMS weight (10 hours at 105 ℃)

Mb: Ash (3 hours at 650 ° C.)

[Table 2. Three Component and Organic Content]

As shown in Table 2, the water (WC), ash (Ash) and flammable (Volatile Solids; VS) contents of the paper sludge were 70.72%, 19.76%, and 9.52%, respectively, and the organic matter content was about 32.52. The percentage of minerals was measured in%. Paper sludge is generally regarded as organic sludge, but final sludge from wastewater treatment including Fenton's oxidation process in paper mills should be separated into inorganic sludge.

2-3. Crystal structure analysis

X-ray diffraction analysis (XRD, Rigaku, D / Max-2000, Japan) was performed to analyze the crystal structure of paper sludge. The diffraction of the incident line and the reflecting surface are both on the same plane, and the angle of diffraction and the incident line is 2θ. Θ is obtained by Bragg's law of the following equation.

<Equation 2>

Where n is the reflection order, λ is the wavelength, and d is the interplanar distance of various planes in the crystal.

The crystal structure of paper sludge was analyzed by comparing the data file of the standard material and the powder diffraction file (Alphabetical Indexes Inorganic Phase Sets 1-45) using the Joint Committee on Powder Diffraction Standards (JCPDS) card. The analysis results are shown in FIG. 2.

As shown in FIG. 2, the XRD results of the paper sludge were compared with those of the JCPDS card to form a main peak of Fe ₃ O ₄ (magnetite) at 29.4 °, 35.4 °, 47.7 °, and 62.5 °. by the Fenton oxidation, it is expected to contain a variety of iron oxides such as α-Fe ₂ O ₃ (hematite (hematite)), α-Fe (α-iron).

In addition, the XRD pattern according to the decomposition reaction temperature was confirmed by proceeding together. In the low temperature PMS01 at 250 ℃ and PMS02 at 300 ℃ showed little change in the peak, the phase transition from the main peak Fe ₃ O ₄ to α-Fe ₂ O ₃ occurs in PMS05 at 450 ℃ the highest temperature there was.

2-4. Chemical element composition ratio analysis

X-ray Fluorescence (XRF) (PW2404, Philips, Netherlands) analysis was performed to determine the chemical element composition of the paper sludge. The analysis results are shown in Table 3.

[Table 3. Composition of Chemical Elements in Paper Sludge]

As shown in Table 3, it can be seen that Fe is very high as 82.6%. It is determined that a large amount of iron oxide is detected by the Fenton oxidation treatment in the papermaking wastewater treatment process. In addition, it was relatively high as Ca 8.11%, Al 3.68%, transition metals such as Mn, Cr, Ni and Cu were detected as 0.39%, 0.39%, 0.22%, 0.13%, respectively.

Example 3. Carbon Dioxide (CO ₂ ) Decomposition reaction and degradation rate measurement.

The experimental apparatus for decomposing carbon dioxide (CO ₂ ) was configured as shown in FIG. 3.

2 g of the papermaking sludge dried in Example 1 was filled in a cylindrical reactor having an inner diameter of 1.5 cm and a length of 6 cm made of stainless steel, and then mounted in a cylindrical electric furnace. Hydrogen reduction was carried out while flowing hydrogen into the reactor at 200 cc / min for 3 hours. Hydrogen reduction was confirmed by the presence of condensate in the water trap of FIG. Subsequently, carbon dioxide was injected into the reactor until the pressure was about 14.7 psi while the hydrogen was blocked and the pressure in the reactor was maintained at 0 psi (vacuum state) with the suction pump. At this time, the carbon dioxide decomposition conditions are shown in Table 1 above, and the samples (PMS01 to PMS05) were carried out at 50 ° C. intervals in the temperature range of 250 to 450 ° C. in the same manner as the temperature of hydrogen reduction [Tamura and Nishizawa, 1992; Kato, 1994]. Carbon dioxide decomposition rate was confirmed that the pressure drop in the reactor by the decomposition reaction changes with time, measured until the pressure in the reactor is constant. The measurement results are shown in FIG. 4.

When the sample inside the reactor is reduced with hydrogen, oxygen may be expressed in a form that is defective, such as M _x Fe _3-x O _4-δ of Chemical Formula 1, and M represents a transition metal (Yang, et al., 2000). ). The hydrogen reduction of the sample was confirmed that the condensed water flows outside the reactor during hydrogen reduction.

<Formula 1>

M _x Fe _3-x O ₄ + _δ H ₂ → M _x Fe _3-x O _4-δ + δH ₂ O

Carbon dioxide is a hydrogen when in contact with an oxygen-defect _{M x Fe 3-x O 4} -δ upon reduction, to the oxygen of the _{M x Fe 3-x O 4} -δ is oxygen by the decomposition of carbon dioxide labile compound such as formula (2) Filled in the vacancy (δ) to form a magnetite of a stable state structure to reduce the pressure inside the reactor.

<Formula 2>

M _x Fe _3-x O _4-δ + 1/2 _δ CO ₂ → M _x Fe _3-x O ₄ + 1/2 δC

In addition, the decomposition of carbon dioxide is made by the pressure change in the reactor, it is possible to calculate the decomposition efficiency by the following equation (3).

&Quot; (3) &quot;

P _IN : Initial pressure

P _OUT : release pressure with reaction time

As a result of calculation according to the above equation, as shown in FIG. 4, the decomposition efficiency of carbon dioxide increased rapidly within the initial 10 minutes at all temperatures, and after 20 minutes, the rate of increase of the decomposition efficiency tended to decrease slowly. . As a result of measuring the decomposition efficiency of carbon dioxide for about 60 minutes, the decomposition rate of carbon dioxide increases with increasing temperature in the temperature range of 250 ~ 400 ℃, about 41% in PMS01, about 50% in PMS02, about 62% in PMS03, and about PMS04 The decomposition rate was high at 73%. However, in PMS05 having a hydrogen reduction temperature of 450 ° C., the decomposition efficiency was found to drop significantly to about 35%. It was confirmed in FIG. 3 that the Fe ₃ O ₄ phase was changed to α-Fe ₂ O ₃ or α-Fe form as the hydrogen reduction temperature was increased. This is similar to the report that Fe ₃ O ₄ phase reported by Zhang et al. (2000) reported that the phase transition occurred as the hydrogen reduction temperature increased, resulting in lower decomposition efficiency. Therefore, in order to increase the decomposition rate of carbon dioxide, the hydrogen reduction temperature should be increased, but it was confirmed that the decomposition rate was lowered as the phase change was relatively large at 450 ° C. or higher. In addition, as the decomposition reaction proceeded in the reactor, after 70 minutes, PMS04 showed about 80% and PMS03 showed about 84% decomposition efficiency.

The decomposition reaction rate of carbon dioxide is closely related to the mobility of oxygen ions [Tamura and Nishizawa, 1992], and the mobility of oxygen ions to oxygen-deficient sites due to the decomposition of carbon dioxide is the highest in the metal catalyst at 350 ℃. It is believed to be due to the fast.

Carbon generated during the carbon dioxide decomposition reaction is adsorbed on the surface of the paper sludge, and the carbon at this time has excellent activity, and when removed from the reactor, it was confirmed that the reaction with oxygen in the air gave a strong flame.

Example 4 Carbon Dioxide (CO) ₂ ) Observation of microstructure before and after decomposition reaction.

In order to observe the microstructure of the paper sludge before and after the carbon dioxide decomposition reaction, PMS04 samples (400 ℃) was analyzed by SEM (Scanning Electron Microscope, JSM-6300, JEOL, Japan). SEM images are shown in FIG. 5.

As shown in FIG. 5, as the carbon dioxide decomposition reaction proceeds at a high temperature, the crystal phase of the paper sludge is changed to a bulk state due to particle growth and carbon adsorption, and thus Fe ₃ O _{4, which} is the main crystal state of paper sludge, is Fe ₂ O _3. It is thought that the phase transition is formed by FeO or the like.

As described above, according to the present invention, carbon dioxide can be efficiently decomposed by recycling the paper sludge generated after the wastewater treatment in the paper mill. Therefore, the generation of carbon dioxide, which is the biggest cause of global warming, can be significantly lowered, and recyclability can be secured as a circulating resource capable of decomposing carbon dioxide using paper sludge.

Figure 1 shows the particle distribution of the papermaking sludge.

2 shows an XRD pattern of paper sludge.

3 is a schematic diagram of an experimental apparatus for carbon dioxide decomposition.

Figure 4 shows the results of measuring the decomposition efficiency of carbon dioxide.

5 shows an SEM image of PMS04 before (A) and after (B) carbon dioxide decomposition reactions.

Claims (8)

Paper Mill Sludge (PMS) and carbon dioxide (CO ₂ ) comprising the reaction, the paper sludge produced from the wastewater treatment including the Fenton oxidation process of the paper mill as a manganese, nickel A method of decomposing carbon dioxide, comprising a spinel magnetite containing transition metals of chromium and chromium. delete delete The method of claim 1 comprising the following steps: a) drying the paper sludge; b) filling the dried papermaking sludge into a reactor; c) injecting hydrogen into the reactor to perform hydrogen reduction; d) blocking hydrogen injection and injecting carbon dioxide; e) reacting the paper sludge with carbon dioxide. 5. The method of claim 4, wherein the hydrogen injection in step c) is injected at 100 to 300 cc / min for 1 to 5 hours. The method of claim 4, wherein the hydrogen reduction condition of step c) is performed at a temperature in the range of 250 to 450 ° C. The method of claim 4, wherein the carbon dioxide injection in step d) is injected until the pressure inside the reactor is 10 ~ 20 psi. The method of claim 4, wherein the carbon dioxide decomposition conditions of step e) is carried out at a temperature range of 250 ~ 450 ℃.

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