KR100413379B1 - Regenerable manganese-based sorbents(MA) for removal of hydrogen sulfide and method for preparing the same - Google Patents

Abstract

The present invention relates to a desulfurization agent (MA) for removing hydrogen sulfide at a high temperature and a method for preparing the same.

Desulfurization agent for removing hydrogen sulfide of the present invention comprises 80% by weight of MnCO ₃ + 15 to ₁₈ % by weight of Al ₂ O ₃ + 5 to ₂ % by weight of bentonite, mixing each sample in a powder state; Adding an appropriate amount of deionized water to make a slurry; Drying until constant weight; Firing; Curing; And by pulverizing and sieving the cured desulfurization agent, the desulfurization agent of the present invention has excellent hydrogen sulfide removal effect at high temperature.

Description

Regenerable manganese-based sorbents (MA) for removal of hydrogen sulfide and method for preparing the same}

The present invention relates to an efficient desulfurization agent capable of removing hydrogen sulfide and regeneration and a method for producing the same.

Although coal has abundant reserves worldwide and favorable conditions in terms of supply stability and economic feasibility, it is difficult to continuously increase the use of current coal direct combustion method. Therefore, the development of clean use technology of coal called CCT (Clean coal Technology) The development of rational coal utilization technology is urgently needed.

The Integrated Gasification Combined Cycle (IGCC) technology is one of the best alternatives to pulverized coal-fired power generation in terms of environmental friendliness, fuel security and thermal efficiency. The business continues steadily, reaching the deepening stage.

The coal gasification combined cycle powers coal with oxygen in a gasifier of high temperature and high pressure (1200 ~ 1500 ℃, 25kg / ㎠) and gasifies it, and clean coal gas which removes dust and sulfur components from dust collector and desulfurization gas is gas turbine fuel. Used as. The thermal efficiency of the system has been evaluated to be more than 15% higher than the thermal efficiency by 45-50% (30-33%) of a conventional pulverized coal-fired power generation, in particular CO ₂ emissions regulations are increasingly enhanced CO ₂ emission is suppressed by more than 10% It is also very preferable from the viewpoint.

Fuel gases contaminated with ash, sulfur, nitrogen, alkali metals and various trace contaminants in coal are deposited or corroded in gas turbines, which shortens the durability of the system and causes environmental problems. Should be removed.

In the US, the METC (Morgantown Energy Technology Center) under the Department of Energy (DOE) has been involved in research and development of high-temperature dry desulfurizers and processes for about 20 years. have.

The metal oxide desulfurization agents studied so far are Zn, Fe, Cu, Ca, Mg, V, Mn, Ni, Co, Sn, Pb, Bi, Cd, Mo, W, Cr and so on. It has both advantages and disadvantages.

According to various experiments, Zn, Fe, Cu, Mn, Ce, etc. are the primary active ingredients that can reduce the concentration of hydrogen sulfide (H ₂ S) in coal gas below 20ppmv, and the additives include Cu, Fe, Mn , Cr, Ce, Co, Mo, Ni and the like, Al ₂ O _3, SiO _2, TiO _2, ZrO ₂ and the like is reported that can be used (Ryu Cheong-gal, Chemical Industry and Technology, 1998). In addition, in the preparation of the metal oxide in the preparation of the desulfurization agent, the sintering temperature, the sintering time, the cure temperature, the cure time and the type and content of the binder (binder) act as important variables. It is known that the type or additive of the binder acts as an important factor for improving the wear resistance of the desulfurization agent. The binder can be divided into an organic binder and an inorganic binder. In the case of the organic binder, the shape of the particles is determined during molding of the desulfurization agent. Inorganic binders are used to assist solid-solid bonding of the composite metal oxides. Therefore, there is a need for an appropriate selection and blending method of an organic binder and an inorganic binder according to the molding method of the particles.

Among the desulfurization agents developed so far, the commercialization stage is a mixed zinc desulfurization agent, and in recent years, much attention has been focused on the preparation and experimentation of manganese desulfurization agents in an attempt to overcome the disadvantages of the zinc desulfurization agent.

Westmoreland et al. (Environmental Science Technology, 22 (5), 1977) conducted a kinetic study to predict the stability of manganese oxides and desulfurization at temperatures above 1000 ° C. From these kinetic considerations, the relative magnitudes of the initial reaction rates between H ₂ S and MnO, CaO, ZnO and V ₂ O ₃ at 300 to 800 ° C were MnO>CaO>ZnO> V ₂ O ₃ . Therefore, in this study, the researchers concluded that MnO was most effective for high temperature desulfurization processes.

Turkdogan and Olsson et al. (Proceedings of the Third International Iron and Steel Congress ASM, pp. 277-288, 1979) have tested the availability of manganese oxides at high temperature desulfurization and mix Mn and alumina in a 3: 1 weight ratio. It has been found that sulfur can be removed from the H ₂ -H ₂ S gas mixture at 800 ° C. and regenerated with air.

Hepworth et al. (Energy Fuels, 7 (6), 1993) reported that, from a thermodynamic perspective, to evaluate the behavior of single or complex metal desulfurization agents to remove sulfur from hot fuel gases, manganese, iron, nickel, magnesium, copper, sodium, Studies on linked metals have shown that manganese oxide is the best metal with low reducibility and can be used over a wide temperature range.

The first challenge to commercialize high-temperature dry desulfurization technology, which is the core technology of IGCC power generation, is to develop a renewable desulfurization agent with good physical and chemical properties.

Manganese-based desulfurization agents can be operated at high temperatures because they have a high reduction resistance to elemental manganese and a melting temperature of 1,232 ℃ even when applied to all fuel gases generated in the actual gasifier.

In addition, there is an advantage that the reaction rate is much faster than the zinc-based desulfurization agent.

Accordingly, the present invention provides a manganese-based desulfurization agent capable of adsorbing and removing hydrogen sulfide generated from coal gasification combined cycle power generation at a high temperature, and a method of manufacturing the same.

Desulfurization agent composition of the present invention for achieving the above object is to prepare a desulfurization agent in 80% by weight of MnCO ₃ and 15 to ₁₈ % by weight of Al ₂ O ₃ and 5 to ₂ % by weight of bentonite, the method for producing a desulfurizing agent of the present invention is powder Mixing each sample of; Adding an appropriate amount of deionized water to make a slurry; Drying until constant weight; Firing; Curing; And pulverizing and sieving the cured desulfurization agent.

1 is a process diagram schematically showing a desulfurization agent manufacturing process of the present invention

2 is a graph showing a breakthrough curve of hydrogen sulfide removal using the composition of the present invention.

Looking at the present invention in more detail as follows.

Mechanisms of hydrogen sulfide removal by manganese oxides and iron oxides that are reactive with hydrogen sulfide can be divided into reduction and sulfidation stages. First, M _a O _b → M _c O _d (where b / a> d / c, M is manganese or iron) and M _c O _d reacts with H ₂ S to sulfide into MS.

In addition, since MnO has a very small equilibrium constant of the reduction reaction by hydrogen, reduction to manganese rarely occurs, whereas Fe ₂ O ₃ has a high reducibility and is easily reduced by hydrogen or carbon monoxide.

Most regeneration of metal oxide desulfurization agents uses air / steam mixture gas including steam as air or oxygen-deficient air and diluent, and physical durability and reactivity of desulfurization agent by adjusting regeneration conditions such as temperature, oxygen concentration and regeneration gas characteristics. It is necessary to maintain.

Excessive temperature rise in regeneration leads to sintering of the desulfurization agent, which leads to loss of porosity and decrease in reactivity. Regeneration at low temperature leads to the formation of sulphate, which is difficult to decompose once produced and acts as a diffusion barrier for oxygen. Not desirable

Therefore, it is important to find the optimal operating conditions to minimize sulfate formation and sintering effect by preventing hot spots through temperature control and oxygen concentration control in regenerative reaction.

Reaction mechanisms for reduction, sulfidation and regeneration of manganese desulfurization agents are as follows

Scheme 1

(MnO _2, Mn ₂ O, Mn ₃ O ₄ ) + H ₂ (or CO) → MnO + H ₂ O

Scheme 1 shows a process in which manganese oxide is reduced by reacting with a reducing gas.

Scheme 2

MnO + H ₂ S → MnS + H ₂ O

Scheme 2 shows a process in which manganese oxide removes hydrogen sulfide by reacting with hydrogen sulfide after reduction.

Scheme 3

2MnS + 7 / 2O ₂ → Mn ₂ O ₃ + 2SO ₂

Scheme 3 shows a process in which manganese oxide is regenerated by oxygen after sulfidation.

Production Example

Looking at the desulfurization agent manufacturing process of Figure 1, the material used to prepare the manganese-based desulfurization agent is 80% by weight of MnCO ₃ , 15 to ₁₈ % by weight of Al ₂ O ₃ , 5 to ₂ % by weight of bentonite.

The above reagent was used to prepare a desulfurization agent of MA (MnCO ₃ , Al ₂ O ₃ , bentonite) whose primary active ingredient is manganese, and the name of the desulfurization agent of MA is named for convenience of the applicant. Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO _2, etc. are used for the desulfurization agent. In the present invention, Al ₂ O ₃ is used as the support, and Al ₂ O ₃ is inexpensive and has a higher performance than other supports. The role of Al ₂ O _{3 in} the desulfurization agent without falling down compared to other supports is to maintain the porosity in the desulfurization agent to induce a smooth diffusion of hydrogen sulfide, a reaction gas, to improve the reactivity. The binder used was a colloidal mineral having a very large specific surface area and bentonite, a clay material having a high content of montmorillonite, a cationic trapping agent, was used. Clay having a tendency to coagulate naturally and is a relatively strong coagulant and a binder. Bentonite, such a clay binder, is characterized in that the bond is not broken even at a high temperature and the particles maintain a strong bond. Was used.

It looks at the manufacturing method of the desulfurization agent of the present invention.

80% by weight of powdered MnCO ₃ , 15-18% by weight of Al ₂ O ₃ and 5-2% by weight of bentonite were mixed according to the weight ratio, and then deionized water was added to make a slurry, followed by drying oven. ) Was dried until it became a constant (110 ° C.), and calcined at 400 ° C. for 5 hours to decompose manganese carbonate.

After firing, the mixture was transferred to a high temperature furnace preheated to 400 ° C., heated to a curing temperature (1000 to 1200 ° C.), and cured for 2 to 4 hours under an air atmosphere (about 1 L / min).

The final product was pulverized and sieved by particle diameter, 20/40 mesh was used for sulfiding and regeneration experiments, and fine particles of 60 mesh or less were used for the physical property analysis of the desulfurization agent. Since the characteristics and reactivity of this desulfurization agent have a decisive influence, let's take a look at an example. [Table 1] is a chart comparing the effect of curing temperature and time on the strength of desulfurization agent. This experimental condition is based on the desulfurization agent prepared by using 80% by weight of MnCO ₃ , 15% by weight of Al ₂ O ₃ and 5% by weight of bentonite while changing the curing temperature to 1000 ~ 1200 ℃. The Al (%) used in [Table 1] is a three-jet hole attrition tester to check the strength of the desulfurization agent. After 5 hours of fluidization using the attrition loss (attrition loss) is shown in weight percent, the smaller the value means the desulfurization agent having a higher strength due to less wear of the desulfurization agent. As shown in [Table 1] curing time This increase was found to have a negligible effect on the strength of the desulfurizer (approximately 2-3% increase), but was significantly affected by temperature. If the production of the desulfurizing agent used, increasing the cure temperature it is determined to be able to manufacture a custom desulfurizing agent having a desired strength. [Table 1] Effect of curing temperature and time on strength of desulfurization agent [Table 2] is a chart comparing the effect of curing temperature and bentonite content on the strength of the desulfurization agent. Experimental conditions were fixed to 80% by weight of MnCO ₃ and the desulfurization agent prepared by curing for 2 hours while varying the content of Al ₂ O ₃ (15-18% by weight) and bentonite (5-2% by weight) of the desulfurization agent according to the curing temperature The Al (%) used in this table is shown in [Table 1]. As can be seen from [Table 2], the strength of the desulfurization agent was significantly influenced by the content of bentonite (12.7 ~ 19.2%). ). Therefore, when the desulfurization agent to be used in a reactor with high desulfurization wear, such as a fluidized bed, a moving bed reactor, increasing the content of bentonite can produce a desulfurization agent having a desired strength. [Table 2] Effect of Bentonite Content on the Desulfurization Strength

Example

Figure 2 shows the concentration of the exhaust hydrogen sulfide according to the normalized sulfide time t / t ^* at temperature 700, 800 ℃.

Since the equilibrium constant is a function of temperature only, the sulfidation reaction was carried out with a flow rate of 0.75% H ₂ S-20% H ₂ -79% N ₂ and a mixed gas at a flow rate of 200 ml / min. As can be seen in Figure 2, it can be seen that the sulfidation reaction of the manganese-based desulfurization agent is a reversible reaction, and the exhaust hydrogen sulfide concentration before the breakthrough time can be regarded as the equilibrium hydrogen sulfide concentration.

The equilibrium concentration at the temperature of 700 ℃ was 30ppmv for the MA desulfurization agent, and the partial conversion rate was 0.82. Got good results.

The equilibrium concentration at 800 ℃ was 90ppmv for the MA desulfurizer and showed a similar tendency to that of 700 ℃, and the partial conversion was 0.92.

The present invention relates to a manganese-based desulfurization agent that adsorbs and removes hydrogen sulfide at a high temperature, and a method of manufacturing the same. The present invention has a high reduction resistance as elemental manganese even when applied to all fuel gases, and can operate at high temperatures. There is this.

Claims (2)

In the desulfurization agent for removing hydrogen sulfide mainly containing manganese oxide from coal fuel gas, the desulfurization agent is composed of 80% by weight of MnCO ₃ , 15-18% by weight of support Al ₂ O ₃ , and 5-2% by weight of binder bentonite. Desulfurization agent for hydrogen sulfide removal which removes hydrogen sulfide at 550-800 degreeC. A desulfurization agent having 80% by weight of MnCO ₃ , 15-18% by weight of Al ₂ O ₃ , and 5-2% by weight of bentonite as a raw material; Adding deionized water to make slurry; Drying the sample at 110 ° C. until it reaches a constant weight; Firing the dried sample at 400 ° C .; A curing step of curing the fired sample at 1000 to 1200 ° C; Method for producing a desulfurization agent for removing hydrogen sulfide, characterized in that it comprises a pulverizing step of pulverizing and sieving the cured desulfurization agent.