KR20140016840A

KR20140016840A - Method for removing sulphur component in pulverized coal combustion apparatus, and desulphurizing agent

Info

Publication number: KR20140016840A
Application number: KR1020130090071A
Authority: KR
Inventors: 시게요시 오노; 아키히로 호시노
Original assignee: 이데미쓰 고산 가부시키가이샤
Priority date: 2012-07-31
Filing date: 2013-07-30
Publication date: 2014-02-10

Abstract

The purpose of the present invention is to provide a desulphurizing agent capable of achieving a high utilization ratio as compared with a case of using limestone as a desulphurizing agent in a furnace and a method for removing a sulphur component using the same in a pulverized coal furnace. The method of removing a sulphur component from a pulverized coal furnace of the present invention is characterized by feeding a desulphurizing agent containing a lime cake in a pulverized coal furnace to remove a sulphur component of a gas produced in a pulverized coal furnace. [Reference numerals] (2) Experimental pulverized coal furnace; (23) Pulverized coal feeder; (31) Single burner; (32,33) Preheater; (34,35) Entrance for desulphurizing agent + carrier air, thermocouple insertion hole; (43) Combustion exit; (44) Continuous analyzer(NO_X CO_2, CO_2, CH_4,O_2,SO_2); (51) Bottom ash collector; (52) Cyclone(Fly ash sampling); (AA) Secondary air; (BB) Primary air

Description

METHODS FOR REMOVING SULPHUR COMPONENT IN PULVERIZED COAL COMBUSTION APPARATUS, AND DESULPHURIZING AGENT}

The present invention relates to a method for removing sulfur components and a desulfurization agent in a pulverized coal combustion apparatus.

Fuels used in pulverized coal combustion furnaces often contain sulfur components, and the combustion gases are discharged by removing harmful sulfur oxides (SO _x ) such as sulfurous acid gas and sulfuric acid gas generated by sulfur combustion to concentrations suitable for environmental standards. You must do it.

Conventionally, the desulfurization method used in a combustion furnace has the following two methods largely divided.

(1) Desulfurization in a furnace: A method of absorbing and removing sulfur oxides by introducing a desulfurization agent into a furnace.

Usually, limestone or dolomite is used as the desulfurization agent, and this method is mainly used in fluidized bed furnaces.

(2) Flue gas desulfurization method: Sulfur oxides in the exhaust gas are formed by neutralizing the sulfur oxides and the desulfurization agent by providing a contact layer (tower) of the desulfurization agent and the exhaust gas in a part of the furnace flue flue. How to remove it. In this method, gypsum can be effectively used because sulfur oxide and limestone, which is a desulfurization agent, are converted into gypsum by neutralization reaction.

In the furnace desulfurization method, the utilization rate of limestone or dolomite mainly composed of calcium used as the desulfurization agent is low, and when limestone having a particle size of about microns is used in a pulverized coal combustion furnace, the utilization rate of limestone is about 5 to 10%. In order to achieve a desulfurization rate of 40% when using 1.2% sulfur component coal, it is necessary to blow limestone at least 10% with respect to coal as fuel. The low utilization rate of the limestone is because in the limestone of the micron level, desulfurization reaction occurs only on the surface thereof and does not contribute to the reaction up to the inside of the particles, so that much calcium remains unused.

In order to solve such a problem, a method of using fine particles such as calcium oxide (CaO) or calcium hydroxide (Ca (OH) ₂ ) as a desulfurization agent having a smaller particle diameter and a larger ratio of available surface area and excellent reactivity is also studied. Has been.

However, in the above method, a large amount of energy is required to decalcify limestone to produce CaO or Ca (OH) ₂ , resulting in inferior economy.

Patent Literature 1 discloses a flue gas treatment method using calcined lime obtained by calcining a lime cake to obtain quicklime, digesting the quicklime with only water, and calcining quicklime with water at a predetermined mass ratio.

Patent Literature 2 discloses a sulfur component removal method in a fluidized bed apparatus comprising introducing a desulfurizing agent containing a lime cake adjusted to a particle diameter having a maximum particle diameter of 0.08 mm or more in a fluidized bed furnace.

Japanese Patent Publication No. 2007-000721 Japanese Patent No. 4625265

An object of the present invention is to provide a desulfurization agent which can achieve a high desulfurization agent utilization rate in a pulverized coal combustion furnace, compared with the case of using limestone as a desulfurization agent, and a method for removing sulfur components in a pulverized coal combustion furnace using the same.

In order to achieve the above object, the present inventors earnestly study, and in a pulverized coal combustion furnace, the desulfurization agent containing a lime cake is put into a furnace, and the furnace is carried out by the oxidation reaction (combustion) which uses coal, biomass, etc. as a fuel. The present invention has been completed by discovering that the sulfur component in the gas generated at can be efficiently removed and that high desulfurization agent utilization can be achieved.

According to this invention, the sulfur component removal method and the desulfurization agent for pulverized coal combustion furnaces in the following pulverized coal combustion apparatus are provided.

1. A pulverized coal combustion apparatus comprising: a method for removing sulfur components in a gas generated in a pulverized coal combustion furnace,

A sulfur component removal method in a pulverized coal combustion apparatus, wherein a desulfurization agent including a lime cake is introduced into a pulverized coal combustion furnace.

2. Said desulfurization agent is lime cake, The sulfur component removal method in the pulverized coal combustion apparatus of 1 characterized by the above-mentioned.

3. The sulfur component removal method in the pulverized coal combustion apparatus as described in 1 or 2 whose Ca component of the said desulfurization agent is 1-8 (molar ratio) with respect to the sulfur component of a fuel.

4. The sulfur component removal method in the pulverized coal combustion apparatus according to any one of 1 to 3, wherein the desulfurization agent is added to a location in a temperature range of 800 to 1,200 ° C in the pulverized coal combustion furnace.

5. The sulfur component removal method in the pulverized coal combustion apparatus according to any one of 1 to 4, wherein the desulfurization agent is directly introduced into the pulverized coal combustion furnace by air flow conveyance.

6. Desulfurization furnace for pulverized coal combustion furnace including lime cake.

According to the present invention, a desulfurization agent capable of achieving a high desulfurization agent utilization rate compared with the case of using limestone as a desulfurization agent in a pulverized coal combustion furnace, and a method for removing sulfur components in a pulverized coal combustion furnace using the same can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the whole structure of the general pulverized coal combustion apparatus.
2 is a schematic diagram of an experimental pulverized coal combustion furnace used in Examples and Comparative Examples.
3 is a graph showing the desulfurization rate with respect to Ca / S (molar ratio) in the pulverized coal combustion experiments of Example 2 and Comparative Example 2. FIG.

The method for removing sulfur components in the pulverized coal combustion apparatus of the present invention (hereinafter referred to as the method of the present invention) is a method for removing sulfur components in a gas generated in a pulverized coal combustion furnace in a pulverized coal combustion apparatus. A desulfurization agent to be contained is introduced into a pulverized coal combustion furnace.

The present invention is characterized in that a lime cake is used as a dry desulfurization agent to be put into a pulverized coal combustion furnace (also called a pulverized coal boiler).

Moreover, especially when burning coal etc. which contain many sulfur components in a pulverized coal combustion furnace, the load on the wet flue gas desulfurization apparatus following this can be reduced.

Lime cake is a sugar factory by-product discharged by the process of removing impurities, such as an organic substance and a pigment contained in the sugar liquid eluted from the beet which is a raw material in the manufacturing process of sugar. In general, in this step, fine particles of CaO or Ca (OH) ₂ are mixed into the sugar liquid, and further, CO ₂ gas is mixed to attach and precipitate impurities to the particles to separate the high-purity sugar liquid and the precipitate. Dehydrated sediment from this process is lime cake. In other words, the lime cake is a mixture composed mainly of CaCO ₃ in particulate form and an organic substance.

Since the beet-derived organic matter contained in the lime cake acts as a binder to fix CaCO ₃ of the fine particles when the precipitate is dehydrated, the dehydrated lime cake is hardened into a clay shape and partially granulated by natural drying. (I) become The particle diameter of the lime cake depends on the proportion of organic matter and the dry state, but generally has a maximum particle diameter of 5 to 50 mm and a wide particle diameter distribution up to about 5 to 50 μm, which is the minimum particle diameter of the original CaCO ₃ . In addition, since the lime cake has a small primary particle diameter and a large specific surface area, Ca utilization is higher than that of limestone.

Patent Literature 1 uses calcined lime obtained by treating lime cake as a desulfurization agent instead of limestone which has conventionally been used, and does not use lime cake itself as a desulfurization agent. In addition, a process for producing slaked lime from a lime cake is required, and even if a sugar factory by-product is used, economical efficiency is not so improved.

Patent Literature 2 is a prior patent of the present applicant, and in a fluidized bed combustion furnace in which fuel and / or raw materials are combusted by fluidized bed combustion, a method for removing sulfur components in a gas generated in a furnace, and a desulfurization agent including a lime cake. Although the sulfur component removal method characterized by putting into a furnace is disclosed, it does not disclose using the desulfurization agent containing a lime cake in a pulverized coal combustion apparatus.

The pulverized coal combustion apparatus in this invention is also used for the power-generation installation which used coal also the fluidized bed combustion apparatus of patent document 2 is used.

In a fluidized bed combustion apparatus, granular coal (particle diameter of 10 mm or less) is injected into a bed of dry desulfurization agents such as limestone suspended and fluidized by airflow, and burned. This system is used for small to medium scale self-generating equipment because the heat transfer in the fluidized bed is good and the boiler (fluidized bed combustion furnace) can be made small. Moreover, since combustion is performed while circulating, it can burn at relatively low temperature. In a fluidized bed combustion furnace, the combustion reaction proceeds over time while circulating coal as fuel and limestone as desulfurization agent in the furnace, so that the temperature in the furnace becomes almost uniform. In the furnace, thinner particles gather with the top of the furnace with time, and the utilization rate decreases when the particle diameter of the desulfurizing agent is small. Therefore, in the method of patent document 2, the lime cake which is a desulfurization agent which adjusted the largest particle diameter to 0.08 mm or more is used.

On the other hand, in the pulverized coal combustion apparatus, pulverized coal is blown out with air by a burner and combusted. In this system, in general, since coal having a small particle size is used and combusted at a relatively high temperature, combustibility is high. This method is used in large-scale power plants because it can be enlarged. On the other hand, the pulverized coal combustion furnace, unlike the fluidized bed combustion furnace, does not circulate the coal and the desulfurizing agent in the furnace, so that a temperature distribution occurs in the furnace. In the pulverized coal combustion furnace, the smaller the particle diameter of the lime cake, the larger the available surface area can be expected to improve the calcium utilization rate.

The schematic diagram of the whole structure of the general pulverized coal combustion apparatus 1 is shown in FIG.

The pulverized coal combustion apparatus 1 includes a low coal installation 10 for storing coal as a fuel, a crushing facility 20 for pulverizing coal particles into fine coal of 200 mesh (75 μm) or less, and pulverized coal with air. in pulverized coal combustion for combusting the blown with (boiler) 30, a flue gas treatment system 40, and the combustion process associated with the generated times to remove from the gas into the combustion of a NO _x or SO _x caused by combustion of fuel ( (Iii) a ash processing facility 50 for recovering the wastewater is provided.

Next, operation | movement of this pulverized coal combustion apparatus 1 is demonstrated.

After the coal supplied to the hopper 12 from the silo 11 of the storage facility 10 is crushed by the grinder 21, the pulverized coal combustion furnace 30 from the burner center part with primary air for conveyance from the feeder 22 is carried out. The pulverized coal introduced into) is combusted in the pulverized coal combustion furnace 30. At this time, the sulfur component in the fuel becomes sulfur oxide (SO _x ). On the other hand, the desulfurization agent is introduced into the pulverized coal combustion furnace 30 from the desulfurization hopper (not shown), and sulfur oxides (SO _x ) are adsorbed and removed in the pulverized coal combustion furnace 30 by the calcium component in the desulfurization agent.

As for the flue gas after sulfur oxide (SO _x ) is adsorbed and removed by the desulfurization agent, the nitrogen oxide (NO _x ) is removed by the denitration apparatus 41 of the flue gas treatment plant 40, and the (wet) desulfurization apparatus After further removing sulfur oxide (SO _x ) at 42, it is exhausted from the chimney 47. Ash 54 and gypsum 55 collected in the ash processing facility 50 are disposed of or effectively used.

The method of the present invention is characterized by using a desulfurization agent containing a lime cake during the combustion treatment in the pulverized coal combustion furnace (boiler) 30.

In the method of the present invention, a desulfurization agent containing a lime cake is used. This desulfurization agent may be comprised only by a lime cake, and may contain a lime cake in one part.

Examples of the components other than the lime cake contained in the desulfurization agent include fresh concrete sludge containing limestone, dolomite, calcium oxide, calcium, and the like.

The proportion of the lime cake contained in the desulfurization agent is not particularly limited and can be appropriately adjusted according to the type of fuel, raw material, or the like.

The lime cake used by this invention can be used after dehydrating the thing obtained by the manufacturing process of sugar, grind | pulverizing the naturally dried thing with a sieve or as needed, and adjusting the range of a particle diameter.

In the present invention, the lime cake can be used as a desulfurization agent as it is, but can be used as a desulfurization agent by mixing with the other components described above. When mixing other components, the particle diameters of other components are adjusted, clay minerals, such as kaolin and montmorillonite, are kneaded and dried as a binder, and the particle diameter is adjusted by a sieve and manufactured.

In the present invention, the particle diameter of the lime cake is not particularly limited, but the maximum particle diameter of the lime cake is preferably less than 0.08 mm, more preferably 0.075 mm or less.

In the method of the present invention, the desulfurization agent is usually added in the pulverized coal combustion furnace so that the Ca component of the desulfurization agent is 1 to 8 (Ca / S molar ratio) with respect to the sulfur component in the fuel and / or raw material, and desulfurization in the furnace is performed. desirable. When this molar ratio is lower than 1, sufficient reaction may not be obtained. On the other hand, when it is higher than 8, although a high reaction rate is obtained, the amount of residues generated may increase and the ash throughput may increase. Therefore, it is preferable to introduce | pour so that it may become 1-5 (molar ratio), More preferably, it becomes 1-3 (molar ratio).

In the method of this invention, it is preferable to add the desulfurization agent containing a lime cake to the location of the temperature range of 800-1,200 degreeC in a pulverized coal combustion furnace, and it is more preferable to add to the location of the temperature area of 800-1,100 degreeC. .

Although the desulfurization rate is higher when the reaction is carried out at a higher temperature, the lime cake particles are melted at too high temperature, the surface of the lime cake particles melts, and Ca inside the lime cake particles is not used, so the desulfurization rate is lowered. Found.

This problem did not occur in a fluidized bed combustor in which the reaction proceeds over time while circulating the furnace at a relatively low temperature of generally 1,000 ° C. or less. In a fluidized bed combustion furnace, the temperature in the furnace becomes almost uniform because coal and the desulfurization agent circulate in the furnace. Therefore, even if a desulfurizing agent containing a lime cake is introduced at a position in the fluidized bed combustion furnace, even if the fuel and the desulfurizing agent are mixed together and introduced into the furnace, there is no problem that the surface of the desulfurizing agent melts.

In the pulverized coal combustion furnace, the furnace temperature becomes a high temperature close to 1,500 ° C, and, unlike the fluidized bed combustion furnace, the reaction proceeds in a short time and a temperature distribution occurs in the furnace. Therefore, desulfurization efficiency is not remarkably improved even when using a desulfurization agent containing a lime cake as in the case of a fluidized bed combustion furnace.

Therefore, when the desulfurization agent containing the lime cake is introduced into the pulverized coal combustion furnace, melting of the desulfurization agent containing the lime cake can be suppressed by adding the desulfurization agent including the lime cake to a location in a temperature range of 800 to 1,200 ° C in the furnace, thereby providing high desulfurization. The inventors found that a rate was obtained.

Therefore, as in the case of the fluidized bed combustion furnace of Patent Literature 2, when a desulfurization agent including a fuel and a lime cake is mixed and introduced into the pulverized coal combustion furnace, the desulfurization agent is easily melted at a high temperature. It is not preferable to mix and add.

The location within the said temperature range in which the desulfurization agent containing a lime cake is thrown in can be determined by referencing the furnace temperature measurement data.

In the method of this invention, it is preferable to add a desulfurization agent directly into a pulverized coal combustion furnace by airflow conveyance. By introducing a desulfurization agent by airflow conveyance, the advantage that a desulfurization agent does not pass the high temperature part which melt | dissolves is acquired.

In the method of the present invention, the fuel species or raw material which is burned or gasified, thermally decomposed, and partially oxidized includes sulfur components which generate sulfurous acid gas, sulfuric acid gas, and other sulfur oxides (SO _x ). It is useful in terms of solid fuels such as coal, petroleum coke, oil sands, biomass, solid fuels, similar fluid fuels in which coal is mixed with water or oil, liquid fuels such as heavy oil, kerosene, alcohol mixtures, LPG, LNG, plant Gas fuels such as exhaust gas, wastes such as garbage, mud, plastics, sludge, tires, or at least two kinds of mixtures selected from them are used.

Example

Although an Example is given to the following and this invention is demonstrated to it further more concretely, this invention is not limited at all by an Example.

material:

(1) desulfurization agent

After drying a lime cake of Hokkaido (Northern Hokkaido) which has the property shown in following Table 1, it was prepared so that maximum particle diameter might be 75 micrometers or less, and it was set as the desulfurization agent.

(2) coal (fuel)

The properties of coal 1 and coal 2 used in Examples and Comparative Examples are shown in Table 2 below.

Combustion test in pulverized coal combustion furnace

Example 1

Coal 1 (pulverized coal) having the properties shown in Table 2 was blown into the furnace together with primary air from a single burner 31 of the experimental pulverized coal combustion furnace 2 shown in FIG. 2. Herein, the desulfurization agent consisting of only the lime cake prepared in the above (1) is used in the furnace from the desulfurization agent inlet 34 at the position of about 1,200 ° C, and the Ca component of the lime cake with respect to the sulfur component in the coal is 0 and 1.3 ( Ca / S; molar ratio) was charged into the furnace together with the secondary air.

On the other hand, the position where the furnace temperature was about 1,200 ° C was determined by measuring the temperature from the temperature measuring hole in the furnace using the thermocouple 35.

Analyzing the SO _x concentration in the combustion outlet 43, the desulfurization efficiency was determined by the calculation method described below. The results are shown in Table 3.

Desulfurization rate (%) = (a / b) × 100

a = [SO _x emission concentration under no desulfurizer input (Ca / S = 0)]-(SO _x emission concentration)

b = SO _x emission concentration under no desulfurization (Ca / S = 0) conditions

On the other hand, the combustion conditions of the test were the highest combustion temperature: 1,420 ℃, combustion pressure: 100mmH ₂ O, fuel (pulverized coal) injection rate: 6kg / hour.

Comparative Example 1

A combustion experiment was conducted in the same manner as in Example 1 except that limestone (chichisan) prepared with a maximum particle diameter of 75 µm or less was used as a desulfurization agent, and the Ca / S molar ratio was set to 2.9. analysis of the SO _x concentration, the desulfurization efficiency was determined by the calculation method described above. The results are shown in Table 3.

From the results in Table 3, it can be seen that in order to obtain almost the same desulfurization rate, limestone needs to be at least twice the Ca / S (molar ratio) of the lime cake. That is, when a lime cake is used as a desulfurization agent used in a pulverized coal combustion furnace, the desulfurization rate of 2 times or more is obtained compared with the conventional limestone.

This high desulphurization rate is the same as the maximum particle diameter of the lime cake used in the Example and the limestone used in the comparative example is 75 μm or less, but when the particle size distribution in the particles of both limestone and lime cake is compared to 75 μm or less, It is thought that the lime cake side is due to many grains. Since most of the reaction between the sulfur component and the desulfurization agent occurs on the surface of the desulfurization agent, it is considered that the surface of the lime cake containing a lot of fine particles increases the surface area and thus high desulfurization efficiency.

Example 2

Coal 2 (pulverized coal) having properties shown in Table 2 was blown into the furnace together with primary air from the single burner 31 of the experimental pulverized coal combustion furnace 2 shown in FIG. 2. Here, in the desulfurization agent consisting only of the lime cake prepared in the above (1), the Ca component in the lime cake is 0.9 and 2.9 (Ca / S; molar ratio) with respect to the sulfur component in the coal at a position where the temperature in the furnace is 1,110 ° C. In the furnace with secondary air under conditions. In the same manner as in Example 1, the desulfurization rate was obtained. The results are shown in Table 4 and FIG. 3.

Comparative Example 2

Combustion was carried out in the same manner as in Example 2 except that the desulfurization agent was changed to the same limestone (chichibutane) as in Comparative Example 1, and the Ca component in the limestone was 1.0 and 2.5 (Ca / S; molar ratio) with respect to the sulfur component in coal 2. An experiment was conducted to determine the desulfurization rate. The results are shown in Table 4 and FIG. 3.

Table 4 and FIG. 3 show that in Example 2 using a lime cake as a desulfurization agent, a high desulfurization rate is obtained despite Ca / S (molar ratio) being smaller than that of Comparative Example 2 using limestone.

Example 3

The desulfurization agent which consists only of the lime cake prepared by said (1) was blown in at the position of 1,000 degreeC in a pulverized coal combustion furnace. The input amount of the desulfurizing agent was 3.0 (Ca / S; molar ratio) of the Ca component in limestone with respect to the sulfur component in coal 2. Test conditions and the desulfurization rate were calculated in the same manner as in Example 1. The results are shown in Table 5.

Comparative Example 3

The same limestone as in Comparative Example 1 was mixed with a Ca component in limestone to a sulfur component in coal 2 at a ratio of 3.9 (Ca / S; molar ratio) and burned in a pulverized coal combustion test furnace. The desulfurization rate was calculated in the same manner as in Example 1. The results are shown in Table 5.

Compared with Comparative Example 3 in which limestone and coal, which are a desulfurizing agent, were mixed and introduced into a combustion furnace, it can be seen that in Examples 2 and 3, a high desulfurization rate is obtained at low Ca / S (molar ratio). When the lime cake is used as the desulfurization agent, it can be seen that a high desulfurization agent utilization can be achieved as compared with the case of using a conventional limestone.

The sulfur component removal method of the pulverized coal combustion apparatus of the present invention is suitable in the energy field and waste treatment field using incineration, gasification, thermal decomposition of fossil fuels such as coal and heavy oil, waste, biomass and the like, and the generated exhaust gas. Do.

The desulfurization agent for the pulverized coal combustion furnace of the present invention and the sulfur component removal method in the pulverized coal combustion apparatus are particularly useful in large-scale power plants and the like.

Moreover, according to this invention, the lime cake which is a sugar factory byproduct can be utilized effectively.

1: pulverized coal combustion apparatus 2: experimental pulverized coal combustion furnace (boiler)
10: low coal plant 11: silo
12: hopper 20: grinding equipment
21: grinder 22: feeder
23: pulverized coal feeder 30: pulverized coal combustion furnace (boiler)
31: single burner 32, 33: preheater
34: desulfurization agent and return air inlet 35: thermocouple insertion port
36: air heater 37: indentation ventilator
40: flue gas treatment plant 41: denitration apparatus
42: (wet) desulfurization apparatus 43: combustion outlet
44: continuous analyzer 45: gas gas heater
46: manned ventilator 47: chimney
50: ash processing equipment 51: bottom ash tray (bottom ash collection)
52: cyclone (fly ash collection) 53: electric dust collector
54: Time 55: Gypsum
60: drainage treatment

Claims

In a pulverized coal combustion apparatus, as a method of removing the sulfur component in the gas which arises in a pulverized coal combustion furnace,
A sulfur component removal method in a pulverized coal combustion apparatus, wherein a desulfurization agent including a lime cake is introduced into a pulverized coal combustion furnace.

The method of claim 1,
A sulfur component removal method in a pulverized coal combustion apparatus, characterized in that the desulfurization agent is a lime cake.

3. The method according to claim 1 or 2,
A sulfur component removal method in a pulverized coal combustion apparatus, wherein the Ca component of the desulfurization agent is 1 to 8 (molar ratio) with respect to the sulfur component of the fuel.

3. The method according to claim 1 or 2,
A sulfur component removal method in a pulverized coal combustion apparatus, wherein the desulfurization agent is introduced at a location in a temperature range of 800 to 1,200 ° C in a pulverized coal combustion furnace.

3. The method according to claim 1 or 2,
A sulfur component removal method in a pulverized coal combustion apparatus, wherein the desulfurization agent is directly introduced into a pulverized coal combustion furnace by airflow conveyance.

Desulfurizer for pulverized coal combustion furnace containing lime cake.