KR100333184B1 - Preparing method of an absorbent for sulfur oxide in low temperature. - Google Patents

Abstract

The present invention relates to the preparation of a sulfur oxide adsorbent for dry low temperature desulfurization process that can effectively remove sulfur oxides in the low temperature region (120 ℃ or less).

15 to 80 parts by weight of at least one calcium compound selected from calcined lime, quicklime, or calcined dolomite (CaO.MgO), 5 to 30 parts by weight of activated carbon, and 5 to 20 parts by weight of clay, are mixed with KMnO ₄ , NaOH, KOH as a catalyst. 0.1 to 15 parts by weight of one or more selected from the mixture is kneaded in 50 to 200 parts by weight of water and dried to adjust the water content of the mixture to 10 to 30% for the dry low-temperature desulfurization process for extrusion molding in the form of pellets It relates to a method for producing a sulfur oxide adsorbent.

Description

Preparing method of an absorbent for sulfur oxide in low temperature.

The present invention is made of a highly reactive calcium compound such as slaked lime, quicklime, or calcined dolomite (CaO.MgO) as a main raw material, and activated carbon, clay and a small amount of catalyst are added to the exhaust gas containing sulfur oxides. A method for producing a dry, low temperature sulfur oxide adsorbent for adsorption and removal of sulfur oxides therein.

With the development of industrialization, the use of fossil fuels such as coal and petroleum increases, and the emissions of sulfur oxides (SO _X ) and nitrogen oxides (NO _X ) contained in these combustion gases are also increasing. As such, emission regulations for these are increasingly being tightened.

In addition, the issue of environmental protection is not only a domestic issue but also an international issue that discusses how to cope with international organizations in order to protect the global environment.

Current methods for reducing the amount of sulfur oxides emitted include low sulfur fuel, desulfurized fuel, or desulfurization after combustion.

The present invention relates to a method for producing an adsorbent for use in dry desulfurization of exhaust gases after combustion.

Conventionally, the sulfur oxide treatment method of the exhaust gas using lime and magnesium hydroxide is mainly used for non-regeneration wet process, but the above process generally depends on the adsorption device, so if the whole device is not changed, Not only is it difficult to introduce the process, but there are also secondary environmental pollution problems, such as the need for wastewater treatment facilities and the generation of waste products by-products of environmental pollution. In addition, the dry high temperature desulfurization process is used in some small boilers, but has problems in terms of economic efficiency and removal efficiency.

In the wet process, the slurry of limestone, slaked lime, magnesium hydroxide or quicklime as an absorbent is used to collect and recover SO ₂ in the exhaust gas with CaSO ₃ (calcium sulfite) or MgSO ₃ (magnesium sulfite) and oxidize it to gypsum. To produce as a by-product.

The SO ₂ removal process is according to the following scheme

CaCO ₃ + SO ₂ + H ₂ O → CaSO ₃ ㆍ 1 / 2H ₂ O + CO ₂ + 1 / 2H ₂ O

Or Ca (OH) ₂ + SO _2- > CaSO ₃ -1 / 2H ₂ O + 1 / 2H ₂ O

Or Mg (OH) ₂ + SO ₂ + 5H ₂ O → MgSO ₃ ㆍ 6H ₂ O

The oxidation process proceeds according to the following reaction formula.

CaSO ₃ ㆍ 1 / 2H ₂ O + 1 / 2O ₂ + 3 / 2H ₂ O → CaSO ₄ 2H ₂ O

Or MgSO ₃ + 1 / 2O ₂ → MgSO ₄

The rate of SO ₂ absorption by limestone slurry or lime slurry is faster as the pH and concentration of the sludge is higher and the particle size of the absorbent is finer. The less impurities contained in limestone and lime can be used for gypsum board and cement additives after filtration of gypsum generated as a by-product.

In the above scheme, since CaCO ₃ , Ca (OH) ₂ , Mg (OH) _2, and the like are dispersed in an aqueous solution, sludge and waste water are inevitably generated after filtration of the reaction product.

The above reaction is a wet reaction, which is a general wet process in which a gas-liquid-solid is present in the form of dissolving SO ₂ gas in water and then inducing a reaction on a slurry. It is an advantage in terms of mixing and contact time, but it is necessary to dehydrate and dispose of sludge produced after the reaction, and also to treat wastewater. Will be needed.

Dry-array desulfurization processes are relatively smaller in size compared to wet processes, reduce waste water treatment costs and lower investment costs, while lowering SO ₂ removal rates and operating costs associated with the use of expensive absorbents. Essentially, dry flue gas desulfurization is a gas-solid reaction, which limits the SO ₂ removal efficiency, so it is applied to the treatment of combustion gases such as low sulfur coal.

Common sulfur oxide absorbents used in the dry method include metal oxides such as CuO and ZnO, which are reacted according to the following reaction formulae.

CuO + SO ₂ + 1 / 2O ₂ → CuSO ₄

ZnO + SO ₂ + 1 / 2O ₂ → ZnSO ₄

In addition, activated carbon, which has good adsorption performance, may be directly used as an absorbent.

Current methods of SO ₂ removal include dry method and wet method. The disadvantages of dry method are low SO ₂ removal rate while using expensive absorbents such as CuO and ZnO activated carbon, and the disadvantage of wet method is excessive equipment cost, NaOH, Ca (OH ₂ ), Mg (OH) ₂ and the like, there is a difficulty in treating the corrosion, wastewater and sludge of the device. The present invention is to improve the shortcomings of the dry and wet method, the SO ₂ gas is collected and sent to the adsorption tower filled with the adsorbent adsorption is inexpensive, the adsorbent used is low cost, no waste water generated, adsorption This SO ₂ adsorbent must be landfilled in a non-regenerated manner. Lime (quick lime, hydrated lime) or calcined dolomite, which is the main part of the adsorbent, can stabilize the land and stabilize heavy metals from landfills, preventing environmental pollution from leachate. Can play a role.

The present invention relates to a method for producing an adsorbent for a dry desulfurization process that can effectively remove sulfur oxides in a low temperature region (120 ℃ or less). The desulfurization process using the adsorbent of the present invention is a method of adsorbing and removing sulfur oxides by introducing a sulfur oxide-containing gas into an adsorption tower filled with an adsorbent. It has a feature that can be removed.

Hereinafter, the sulfur oxide adsorbent manufacturing method of the present invention will be described in detail.

15 to 80 parts by weight of at least one selected from calcined lime Ca (OH ₂ ), quicklime (CaO) or calcined dolomite (CaO.MgO), 5 to 30 parts by weight of activated carbon, 5 to 20 parts by weight of clay, and KMnO ₄ as a catalyst. , At least one selected from NaOH and KOH, and 0.1 to 15 parts by weight of the mixture is added and dispersed in 50 to 200 parts by weight of water. The slurry thus obtained is dried at a temperature of 90 to 150 ° C. to adjust the water content of the mixture to 10 to 30%, and then pelletized sulfur oxide adsorbent is prepared under extrusion.

Lime and calcined dolomite used in the sulfur oxide adsorbent are low in price and can be easily purchased. In addition, the moldability is good and the porosity and specific surface area can be improved depending on the treatment method, so that sulfur oxide can be more easily adsorbed. .

When the adsorbent of the present invention is used and landfilled, hydrated lime reacts with the heavy metal to form a hydroxide, so that the heavy metal is not leached in the aqueous solution, thereby effectively removing the heavy metal in the leachate. Quicklime reacts with moisture to lower the moisture content and kills pathogens present in the landfill, thus helping to stabilize the landfill and strengthen the ground.

Activated carbon is divided into granular and powdered activated carbon. Its specific surface area is 700-1600 m2 / g, and it is excellent in deodorizing performance of organic materials and neutral compounds and is widely used to remove heavy metals in wastewater treatment. In the present invention, powdered activated carbon having a relatively low price and a high adsorption rate was used.

White clay is commonly used as a decolorizing and deodorizing agent. When it is added in molding powder, it can improve the molding strength even at low pressure, which helps to prevent the pressure drop during the filling of the adsorbent.

KMnO _{4, which} is used as a catalyst, is generally used as an oxidizing agent, and the sulfur oxide SO ₂ is oxidized to SO _{3 in} adsorption to increase the reactivity of the adsorbent gas, thereby increasing the removal efficiency of the sulfur oxide.

On the other hand, NaOH, KOH can improve the adsorption performance by the neutralization reaction with sulfur oxides.

KOH and NaOH are absorbent and chemically similar compounds and react with SO ₂ according to the following reaction formula.

2NaOH + SO ₂ → Na ₂ SO ₃ + H ₂ O

2KOH + SO ₂ → K ₂ SO ₃ + H ₂ O

Na ₂ SO ₃ + SO ₂ + H ₂ O → ₂ NaHSO ₃

K ₂ SO ₃ + SO ₂ + H ₂ O → ₂ KHSO ₃

The generated NaHSO ₃ and KHSO ₃ are recovered or discarded.

As in the above reaction, NaOH and KOH react with So ₂ so that the final product is NaHSO ₃ and KHSO _{3 as} a result of neutralization. Therefore, the adsorption capacity is improved because SO ₂ is adsorbed and removed.

KMnO _{4, which} is used as a catalyst, is generally used as an oxidizing agent. Upon adsorption, sulfur oxides SO ₂ are rapidly oxidized in the form of SO ₃ to increase the reactivity of adsorption gas and increase the reaction rate, thereby increasing the efficiency of removing sulfur oxides. Can be.

Activated carbon and clay are currently the most widely used adsorbents and have a large specific surface area, which is used as a concept of physical adsorption. In addition, since the lime and the like in the raw material has excellent water absorption ability, the strength of the pellet molded body which absorbed moisture is weakened, so that it is easily broken during filling of the filling tower. In order to compensate this problem, it was used for the purpose of improving the strength after molding.

Example 1

60 parts by weight of slaked lime, 15 parts by weight of quicklime, 10 parts by weight of activated carbon, and 10 parts by weight of clay are mixed uniformly. To this, 4 parts by weight of KOH and 1 part by weight of KMnO ₄ are added and mixed to obtain a mixture.

This mixture is charged and dispersed in 100 parts by weight of water to obtain a slurry. The slurry was hot air dried at a temperature of 100 ° C. to adjust the yield to 20%, and then extruded with an extruder to prepare a sulfur oxide adsorbent molded into pellets.

600 g of the above-mentioned adsorbent was packed into a column, and the adsorption-removal experiment was carried out at the inlet sulfur oxide concentration of 10,000 ppm (diluent gas: N ₂ ), the space velocity 200hr ^-1 , and the temperature at room temperature, 70 ° C, and 120 ° C, respectively. The results are shown in the following Table 1, Example 1-1. The sulfur oxide adsorption capacity was expressed as the adsorption duration until 1 ppm of sulfur oxide was detected in the outlet gas.

In Table 1, Examples 1-2, 1-3, and 1-4 show sulfur oxide adsorption capacity of the sulfur oxide adsorbent prepared by the method of Example 1, except that only a partial composition ratio of the raw material was changed.

Table 1 shows the raw material cost and the sulfur oxide adsorption removal results of the sulfur oxide adsorbent prepared in this example.

In particular, the adsorbent of the present invention exhibited excellent adsorption and removal performance at room temperature to 120 ° C, as shown in the following Tables 1, 2 and 3.

Table 2 compares the sulfur oxide adsorption and removal capacity of activated carbon as a comparative agent and an adsorbent of the present invention prepared by the method of Example 1 of the present invention.

Example 2

As shown in Table 3 among the raw materials used in Example 1, the results of adsorption removal of the sulfur oxide adsorbent prepared in the same manner as in Example 1 by replacing calcined lime with calcined dolomite (CaO.MgO) are shown in Table 3. In Table 3, Examples 2-1, 2-2, 2-3, and 2-4 show the adsorption capacity of the sulfur oxide adsorbent prepared by changing only the composition ratio of the raw materials to the ratios shown in Table 3.

Example 3

The calcined lime was calcined at 600 ° C. for 1 hour before the quicklime and various other additives were mixed. The sulfur oxide adsorbent was prepared in the same manner as in Example 1 using the quicklime lime obtained by reacting with the water and the rehydrated limestone as a main raw material. Table 3 shows the raw material cost and sulfur oxide adsorption removal results of the adsorbent prepared in this example. According to Table 3, the adsorbents using slaked lime treated by the above method showed higher removal rate of sulfur oxides than the adsorbents using untreated slaked lime, which showed fine grain size and uniform particle size distribution during firing and rehydration. It is presumably due to the improved reactivity with sulfur oxides.

As a comparative agent, granule-type activated carbon prepared from palm husk was used. The sample amount was 600 g as in Example 1-1 and the temperature was performed at 70 ° C.

The present invention relates to a method for producing a sulfur oxide adsorbent for a dry desulfurization process mainly containing calcium compounds such as slaked lime, quicklime and calcined dolomite.

Problems because it shuts off the path as the adsorbent prepared only of the calcium compound in the particles of the CaSO ₄ and 2H ₂ O which is formed after the SO ₂ and the reaction brought into close contact with each other SO ₂ is introduced to the inside adsorbent is SO ₂ absorption efficiency drops Follows.

In the present invention, activated carbon is used to provide a path through which SO ₂ can be introduced into the adsorbent. As the addition ratio of activated carbon is increased, the adsorption performance is improved, but the moldability is deteriorated. If it exceeds 30 parts by weight based on the total weight of the adsorbent, the moldability is poor and the strength after molding is not suitable.

The amount of NaOH or KOH added was also proportionally improved at 15 parts by weight or less relative to the total weight of the adsorbent.

KMnO ₄ is a catalyst that oxidizes SO ₂ to SO ₃ to increase the reactivity of the adsorbed gas, thereby limiting its composition range in terms of economy.

The clay is excellent in formability, and when 5 to 20 parts by weight of the total weight of the adsorbent is added, the molding strength of the adsorbent is improved, but the adsorbing ability decreases as the amount added increases.

The desulfurization process using the adsorbent of the present invention is simpler than the conventional wet treatment process, but does not generate sludge or waste water, and it is possible to manufacture the adsorbent using low cost raw materials and have high SO ₂ removal efficiency than the dry treatment process. Has an advantage. In addition, when the landfill treatment is used, it reacts with heavy metals and forms hydroxides, which effectively removes heavy metals in leachate and lowers water content by reacting with moisture, thereby helping to stabilize the landfill and strengthen the ground of the landfill. There is this.

Claims (2)

In the method for producing a sulfur oxide adsorbent, 15 to 80 parts by weight of calcium compound, 5 to 30 parts by weight of activated carbon, 5 to 20 parts by weight of clay, are mixed, and 0.1 to 15 parts by weight of at least one selected from KMnO ₄ , NaOH, and KOH. The added mixture was kneaded in 50 to 200 parts by weight of water to obtain a slurry. The slurry was dried to adjust the water content to 10 to 30%, and then extruded into pellets to form a sulfur oxide adsorbent for low temperature. Manufacturing method. The method of claim 1, wherein the calcium compound is selected from hydrated lime, quicklime or calcined dolomite (CaO.MgO).