KR20210106076A - Fluidized-bed boiler interior and tube surface slagging or fouling combustion additives using lime and biomass as fuel - Google Patents

Abstract

According to the present invention, a combustion additive to protect the inside fluidized bed boiler that uses coal and biomass as a fuel and the tube surface thereof from slagging or fouling is an anti-slagging or anti-fouling combustion additive to prevent slag formed on the inside of the boiler, heating surface, and a tube surface thereof, comprising pretreated halloysite powder, which is manufactured by immersing kaolin raw ore having a halloysite crystal structure in an aqueous solution of sodium alginate to which methacryloyl propyltrimethoxysilane is added, and then drying and pulverizing the same.

Description

Fluidized-bed boiler interior and tube surface slagging or fouling combustion additives using lime and biomass as fuel }

In the case of a fluidized bed boiler using coal and biomass as fuel, the ASH of inorganic components generated as oxides during fuel combustion in a semi-liquid state is prevented from adhering to the inside of the boiler and the tube surface. It relates to a slagging or fouling suppressing combustion additive based on structured kaolin.

As the need for reduction has emerged as a social issue due to the deterioration of ecological environmental conditions due to the increase in fine dust and carbon dioxide emissions, the structure of generating electricity with coal is gradually shifting from the structure of generating electricity with renewable energy and biomass. Social phenomena are natural.

In this case, the same applies to the case of using coal as a raw material, but in particular, in the case of thermal power plants using biomass fuels such as wood pellets and bio-SRF as main fuels, potassium (K) or Components such as sodium (Na) react with chlorine (Cl), phosphorus (P), and sulfur trioxide (So3) in the high-temperature combustion process to produce alkali metal compounds such as KCl, K2SO4, and Na2SO4. It attaches to the convection part and the tube surface and causes slagging or fouling to form a sedimentary layer. by forming

1) Do not corrode the tube;

2) By lowering the temperature of the super heater, the thermal efficiency is reduced,

3) By increasing the temperature of draft loss and stack, it affects the overall performance of the plant.

4) A semi-liquid-state sedimentary layer is formed on the Primary Superheater and the Economizer, creating space between the tubes and causing fouling and plugging,

5) GAS with a low melting point is diffused into the fireproof burner throat, and cracks repeatedly occur in the throat area due to the different expansion rates of slag deposits and refractory materials, which can cause damage to the throat. happens

Due to the above reasons, continuous power generation of the power plant is impossible, and the economic loss increases by increasing the maintenance cost and shortening the life of the equipment.

In the present invention, as described above, components such as _{Fe 2} O ₃ , K ₂ O, and NaO contained in coal and biomass fuel are combined with _{SO 3 to be converted to Na 2} SO ₄ , K ₂ SO ₄ , and chlorine (Cl ) component is converted to hydrochloric acid during combustion and reacts with the iron tube in the heat exchanger. It is converted into iron chloride and reacts with oxygen in the combustion furnace to convert iron chloride to iron oxide It is the main cause of slagging or fouling on the tube surface.

_{To solve this problem, it absorbs KCl, K 2} SO ₄ , Na ₂ SO ₄ , chlorine (Cl), which are low-melting alkali metal compounds, which are the causative substances of slagging or fouling, and forms a powder at high temperature. It is an object of the present invention to develop a solid raw material additive for adsorbing porous organic and inorganic compounds with a high melting point maintained at

The combustion additive for suppressing slagging or fouling on the inside and tube surface of a fluidized bed boiler using coal and biomass as fuel according to the present invention for achieving the above object, the inside of the boiler, the heat transfer surface, and the tube surface Sodium alginate with methacryloylpropylttrimethoxysilane added to kaolin ore having a halloysite crystal structure as a combustion additive for suppressing slagging or fouling to prevent slag from occurring It contains pre-treated halloysite powder, which is prepared by immersing in an aqueous solution and then drying and pulverizing.

According to one embodiment of the present invention, additives used in thermal power plants using biomass as the main fuel have a high melting point of 1580 ° C. or higher and have a high degree of fire resistance, and the shape is a powder with a particle size of 325 mesh. It can be injected directly into the furnace.

In the case of thermal power plants that use biomass, components such as potassium (K), chlorine (CL), and phosphorus (P), which are contained in a larger amount in biomass fuel than coal, combine with oil and inorganic components in a gas state during combustion to ASH It forms a sediment layer by covering the part where convection takes place in the boiler and the surface of the tube, and these components are especially low in melting temperature, so they combine with oil and inorganic components in a molten state to form a clench inside the tube or boiler.

1) Do not corrode the tube;

2) By lowering the temperature of the super heater, the thermal efficiency is reduced,

3) By increasing the temperature of draft loss and stack, it affects the overall performance of the plant.

4) A semi-liquid-state sedimentary layer is formed on the Primary Superheater and the Economizer, creating space between the tubes and causing fouling and plugging,

5) GAS with a low melting point is diffused into the fireproof burner throat, and cracks repeatedly occur in the throat area due to the different expansion rates of slag deposits and refractory materials, which can cause damage to the throat. happens

Additives developed organic and inorganic compounds of components such as potassium (K), chlorine (CL) and phosphorus (P) contained in biomass fuel, which are the causative substances of these problems, are adsorbed to reduce the amount of slag and clanking This can reduce the corrosion rate of the boiler, increase the thermal efficiency and operation rate, and reduce the boiler maintenance cost.

1 is an additive injection position and embodiment according to the present invention.
2 is an economizer, a primary superheater tube corrosion photograph according to the present invention.
3 is a view showing that slag and clan are accumulated in the economizer and the primary superheater tube of the thermal power plant using the Bon Biomes according to the present invention.
4 is a view showing the slag and clank removed from the economizer and the primary superheater tube when the additive according to the present invention is added.

Hereinafter, the present invention will be described in detail.

1 is an additive injection position and an embodiment according to the present invention. 2 is an economizer, a primary superheater tube corrosion photograph according to the present invention. 3 is a view showing that the slag and the clan are accumulated in the economizer and the primary superheater tube of the thermal power plant using the Bon Biomes according to the present invention. 4 is a view showing the slag and clank removed from the economizer and the primary superheater tube when the additive according to the present invention is added.

The combustion additive for suppressing slagging or fouling on the inside and tube surface of a fluidized bed boiler using coal and biomass as fuel according to the present invention prevents slag generated on the inside of the boiler, the heat transfer surface, and the tube surface As a combustion additive for suppressing slagging or fouling for It includes a pre-treated halloysite powder prepared by drying and pulverizing.

It is prepared by mixing the pre-treated halloysite powder with 10 to 15% by weight of borax powder, 5 to 10% by weight of aluminum oxide powder and 10 to 15% by weight of potassium silicate powder.

The kaolin ore is, based on the total weight of the kaolin ore, SiO ₂ 45 to 55 wt%, Al ₂ O ₃ 30 to 35 wt%, Fe ₂ O ₃ 0.5 to 1.5 wt%, CaO 2 to 3 wt%, MgO 0.1 to 0.5 wt%, TiO ₂ 0.05 to 0.3 wt%, NaO ₂ 0.5 to 0.2 wt%, and K ₂ O 0.1 to 0.7 wt%.

The combustion additive for suppressing slagging or fouling on the inside and tube surface of a fluidized bed boiler using coal and biomass as fuel according to an embodiment of the present invention is slag generated on the inside of the boiler, the heat transfer surface, and the tube surface (fouling phenomenon), kaolin ore having a haloshite crystal structure, a tube-shaped crystal structure, is immersed in an aqueous sodium alginate solution to which methacryloylpropylttrimethoxysilane is added, dried and then pulverized The pre-treated kaolin powder with a halloysite crystal structure is the main ingredient.

In detail, the pre-treated kaolin holloysite powder refers to a powder in which sodium alginate is inserted into the kaolin kaolin crystal structure of Holloysite having a tube crystal structure.

According to an embodiment of the present invention, the pre-treated kaolin holloysite powder manufacturing method is methacryloylpropyltrimethoxysilane in an aqueous sodium alginate solution in which distilled water and sodium alginate are dissolved in a weight ratio of 7:3. It is made by immersing the kaolin ore in a state in which 1.5 to 2.5 times the weight of the kaolin ore is added, and then drying and pulverizing the kaolin ore.

The sodium alginate has hygroscopicity as a natural polymer flocculant that is an anionic organic polymer electrolyte, and in particular, it reacts with calcium chloride, barium chloride, aluminum sulfate, zinc sulfate, copper sulfate, silver nitrate, ferric chloride, lead acetate, etc. to be removed while coagulating into a metal salt.

Therefore, metal salts such as calcium chloride, barium chloride, aluminum sulfate, zinc sulfate, copper sulfate, silver nitrate, ferric chloride, and lead acetate generated inside the boiler during combustion are removed by impregnating the kaolin ore having a halloysite crystal structure with the sodium alginate.

In addition, the methacryloylpropyltrimethoxysilane was added to increase the bonding force between sodium alginate and kaolin halloysite as a fusing agent for fusion activation.

However, if the methacryloylpropyltrimethoxysilane is added in excess of 2.5 parts by weight, it may inhibit the impregnation of sodium alginate during immersion, and if it is added in less than 1.5 parts by weight, it weakens the binding force according to the impregnation, so methacryloyl It is preferable to add 1.5 to 2.5 parts by weight of propyltrimethoxysilane based on 100 parts by weight of the kaolin ore.

On the other hand, the kaolin ore used as the subject of this additive has a halloysite crystal structure and is filled with _{H 2 O in the middle.}

As a specific and non-limiting example, the kaolin ore having the halloysite crystal structure is in the form of needle-shaped nanotubes, and thus has a large specific surface area (30 ~ 1000 m ² /g), and low hardness (Mohs hardness tester 1). ~ 2), it is a rather rare aluminum silicate clay mineral with high fire resistance (melting point 1580℃).

The term "haloysite crystal structure" used in the present invention is a cylindrical structure of a silicon circular body and several layers of aluminum oxide in a cylindrical shape, and has a structure separated from an adjacent layer. In addition, since potassium (K) cations are interposed in the space between adjacent layers, the reactivity is much higher than that of the kaolinite structure in which only the outer surface of the crystal can participate in the reaction and absorption. That is, the halloysite crystal structure includes two hydroxyl groups. One of the hydroxyl groups is inside the circular body and the multiple layers of the circular body, and the other is on the tube surface. is the structure

In addition, the kaolin ore used in the present invention is an aluminum silicate clay mineral, and the specific composition is SiO ₂ 45 to 55% by weight, Al ₂ O ₃ 30 to 38% by weight, Fe ₂ O ₃ 1.0 to based on the total weight of the kaolin ore. 3.0 wt%, CaO 2 to 3 wt%, MgO 0.1 to 0.5 wt%, TiO ₂ 0.05 to 0.3 wt%, NaO ₂ 0.5 to 0.2 wt%, and K ₂ O 0.1 to 0.7 wt% may be included. At this time, if the weight ratio of _{the SiO 2} and Al ₂ O _{3 (SiO 2} /Al ₂ O ₃ ) is 1.6 or more or 1.6 to 1.8, it is good to achieve the object of the present invention, but the present invention is not necessarily limited thereto. .

On the other hand, the anticorrosion additive of the biomass fuel type boiler according to an embodiment of the present invention is mixed with the pre-treated halloysite powder with borax powder, aluminum oxide powder and potassium silicate powder can be manufactured.

In detail, the anticorrosion additive of the biomass fuel type boiler is 5 to 10% by weight of Borax powder, 3 to 5% by weight of Aluminum Oxide powder, 10 to 15% by weight of Potassium Silicate powder and the remainder may be made of pre-treated halloysite powder.

In addition, the anti-corrosion additive of the biomass fuel type boiler may be added in an amount of 2 to 4 wt % based on the total weight of the biomass fuel used, but the present invention is not limited thereto. Here, "biomass fuel" may include LNG, wood, bark mixture, waste vinyl, and the like.

Hereinafter, the reason for limiting the component and composition range of the additive of the biomass fuel type boiler according to the present invention will be described.

Borax powder: 5 to 10 wt%

The borax is a white crystalline inorganic mineral, which is added to effectively remove soot and clinker in the boiler to increase thermal conductivity and prevent corrosion of the inner surface. However, if the borax is used in excess of 15% by weight, emulsification properties may appear, and when it is added in an amount of less than 10% by weight, corrosion prevention and the effect of removing soot and clinker are deteriorated, so the range of 5 to 10% by weight is preferable. .

Aluminum Oxide powder: 3 to 5 wt%

The aluminum oxide functions as a dehydration catalyst, and has strong reactivity and high adsorption properties, thereby suppressing the formation of fusions and contributing to reducing the generation of solids. However, when the furnace temperature exceeds 950° C., it is preferable to add it in the range of 5 to 10 wt % because it can form a film while melting.

Potassium Silicate powder: 10 to 15 wt%

The potassium silicate is added to activate alkali to enhance cleaning power. Therefore, when a mixture of alkali metals (Na, K) and alkaline earth metals (Ca, Mg) is contained in the ash, it is dissolved in a low viscosity state, and thus large agglomeration can be suppressed. However, when the potassium silicate exceeds 15% by weight, it must be added below that because it absorbs alkali metals to make an alkali compound with a high melting point, and when it is added in an amount of less than 10% by weight, the alkali activation effect is lowered. It is preferable to add it in weight %.

Hereinafter, the present invention will be described in detail with reference to the following examples for a detailed description of the present invention, but the present invention is not limited to the following examples.

(Example)

A kaolin ore having a weight ratio of _{SiO 2} and Al ₂ O _{3 (SiO 2} /Al ₂ O ₃ ) of 1.6 or more and a halloysite crystal structure was prepared.

In addition, methacryloylpropyltrimethoxysilane was added to an aqueous sodium alginate solution in which sodium alginate was dissolved at 30% by weight, and then the kaolin ore was immersed. The methacryloylpropyltrimethoxysilane was added in 1.5 to 2.5 parts by weight based on 100 parts by weight of the kaolin ore.

Thereafter, the impregnated kaolin ore was dried in a drying furnace and then pulverized to prepare a pre-treated halloysite powder having an average size of 0.02 to 0.04 mm.

Next, by mixing the pre-treated halloysite powder with borax powder, aluminum oxide powder and potassium silicate powder through a mixer, an additive for a biomass fuel type boiler according to the present invention was prepared. .

The composition of the additives of the biomass fuel type boiler is listed in Table 1 below.

borax aluminum oxide potassium silicate Pre-treated halloysite 10 to 15% by weight 5 to 10% by weight 10 to 15% by weight Remainder

(Test example)

a. Experimental conditions

The additive of the biomass fuel type boiler manufactured in the above embodiment is injected while the boiler is being burned or after combustion is finished. As for the injection method, the additive of the biomass fuel type boiler was injected in units of 2 to 4% of the total fuel used through the spray injection nozzle installed at the top when light coal was burned in the coal coal boiler.

In order to evaluate the influence of the additives of the biomass fuel type boiler, the measurement method used as the test method is the thermal efficiency Ψz ratio in the reference case and the test situation. In the present invention, the thermal efficiency Ψz ratio is calculated by the following Equation 1.

In Equation 1, cmP is the contaminant factor measured in ash when the additive of the biomass fuel type boiler according to the present invention is used, and cmW is the contaminant factor measured in the ash when the additive of the biomass fuel type boiler according to the present invention is not used. , cmP and cmW are calculated from Equation 2 below.

Another indicator of the tendency of ash to slag is the SR ratio, which is considered to be very high when the mineral content in the fuel is less than 65.

The slag viscosity can also be known by looking at the SR ratio, and if the SR ratio is large, the slag viscosity is high, and thus the tendency to generate slag is lowered. SR is calculated from Equation 3 below.

b. Test result

A) Fuel characteristics

The properties of the fuel used in the test are listed in Table 2 below.

B) Change of Ash after using the additive in the biomass fuel type boiler according to the above embodiment

The cause of deposits during combustion is that the fuel contains chlorine. A part of chlorine is released in gaseous form such as volatile potassium chloride (KCl) or hydrogen chloride (HCl) during combustion, and the remaining part is sintered. In addition, when the temperature is lowered due to excessive supply of air, the salts present in the fly ash are formed in a semi-liquid state, and the deposits on the heat transfer surface of the boiler increase accordingly.

The comparative analysis of the chemical composition of Ash is compared with the Ash (W) sample of coal corresponding to the increase in the flow (and melting) temperature in the case of the Ash (P) sample collected while injecting the additive of the biomass fuel type boiler according to the above example. When compared, it can be seen that the chlorine content is decreasing.

This can be explained by the fact that potassium (K) is captured in LSW100 and hydrogen chloride is almost released as flue gas.

In Table 3 below, the components of Ash (P) collected when the additives of the biomass fuel-type boiler according to the embodiment are added, and when only the fuel (coal) is input without the additives of the biomass fuel-type boiler The chemical composition of one Ash(W) is listed.

Referring to Table 3, look at the input result of the additive of the biomass fuel type boiler according to the embodiment. The precipitate generated when the additive is injected in the biomass fuel-type boiler according to the embodiment has a higher content of aluminum silicate composed _{of Al 2} O ₃ and SiO _{2 .}

In addition, the higher the silicon dioxide content in the ash sediment with a low iron oxide content, the higher the viscosity of the ash, and thus the possibility of slag generation decreases.

Meanwhile, another important variable that determines the slag potential of ash is iron oxide. When iron content increases Ash tends to decrease in viscosity and increase sediment. For example, when Fe ₂ O ₃ is less than 6%, the rate at which slag is generated from Ash is lowered.

That is, when the additive of the biomass fuel type boiler according to the above embodiment is supplied to the boiler based on the iron oxide content of the Ash sample, the ash produced when burning coal without an additive has a small _{Fe 2} O _{3 component.} It can be seen that the possibility of slag generation is reduced compared to Ash.

Next, the effect on slag generation when the additive of the biomass fuel type boiler according to the above embodiment is used will be examined.

Table 4 below shows the contaminant indicators of Ash.

As shown in Table 4, when the additive of the biomass fuel type boiler according to the above embodiment was injected into the boiler, the mp value became larger and the tendency to generate slag decreased.

The index indicating the tendency of ash slag generation is SR, and if the SR value is less than 65 in inorganic fuels, it is considered that a lot of slag is generated. It can be seen that when the additive of the biomass fuel type boiler according to the embodiment is injected, the SR value is increased compared to the case where the additive is not injected.

In addition, it was found that when the additive of the biomass fuel type boiler according to the above embodiment is used as a boiler additive during combustion, the boiler efficiency is improved. In detail, the heat exchange efficiency during the injection of the additive of the biomass fuel type boiler according to the above embodiment was improved by 6 to 12% more than when only light coal was used.

In summary, the effect of using the additive of the biomass fuel type boiler according to the above embodiment is as follows.

1) Since the melting point of the additive of the biomass fuel type boiler according to the above embodiment is about 1900 ° C. or higher, it is not sintered at the gas temperature in the furnace, and it can be supplied as 325 mesh powder, so that it can be injected into the combustion furnace.

2) By using the additive of the biomass fuel type boiler according to the above embodiment, it has an effect of reducing slag and pollutants. As a result of analyzing the slag generation indicators (cm, SR), slag generated during coal combustion and generation are suppressed.

3) By using the additive of the biomass fuel type boiler according to the above embodiment, it is possible to reduce the generation of slag from the fly ash and improve the heat transfer efficiency by 6 to 12%.

4) By using the additive of the biomass fuel type boiler according to the above embodiment, slag in a semi-liquid state is not generated during combustion, so the flow of ash is increased, but environmental pollutants generated during combustion (SO ₃ , CO ₂ , Acid-smutemd, etc.) is adsorbed to reduce emissions, so it has the effect of preventing environmental pollution.

5) Effect of increasing production efficiency: It is _{combined with V 2} 0 ₅ , a vanadium compound produced by combustion, with nickel, sulfur, iron, etc. to form a semi-liquid state through Throat, Tube, Air Blower, Since fouling and plugs are generated on the walls of the furnace, there are some differences depending on coal, biomass, and vinyl-based materials to remove them, but periodically (1 month to 1 year) fouling is performed. It is possible to solve the problem that continuous production cannot be done because the plug and the plug must be removed.

6) Anti-corrosion effect of equipment: Vanadium (V205) in semi-liquid state causes fouling and V205 compound on boiler burner throat, tube, air blower, combustion furnace wall, etc. It is stacked in a plug state, and SO3 reacts with moisture to condense into sulfuric acid vapor, which accelerates corrosion. By using the additive of the biomass fuel type boiler according to the above embodiment, the properties of ash are changed, so that it can be used as a material such as cement using ash. In particular, if the additive of the biomass fuel type boiler according to the above embodiment is added, it is possible to prevent the occurrence of mycotoxins, which is a part to be careful when handling biomass storage.

The embodiments described in this specification and the accompanying drawings are merely illustrative of some of the technical ideas included in the present invention. Therefore, since the embodiments disclosed in the present specification are for explanation rather than limitation of the technical spirit of the present invention, it is obvious that the scope of the technical spirit of the present invention is not limited by these embodiments. Modifications and specific embodiments that can be easily inferred by a person of ordinary skill in the art within the scope of the technical idea included in the specification and drawings of the present invention are included in the scope of the present invention. will have to be interpreted.

Claims (3)

A combustion additive for suppressing slagging or fouling to prevent slag generated on the inside of the boiler, on the heating surface, and on the tube surface,
Slagging or A combustion additive for suppressing fouling. The method of claim 1,
The pre-treated halloysite powder
Slagging or fouling prepared by mixing 10 to 15% by weight of Borax powder, 5 to 10% by weight of Aluminum Oxide powder and 10 to 15% by weight of Potassium Silicate powder ( Fouling) combustion additive for suppression. The method of claim 1,
The kaolin ore is, based on the total weight of the kaolin ore, SiO ₂ 45 to 55 wt%, Al ₂ O ₃ 30 to 35 wt%, Fe ₂ O ₃ 0.5 to 1.5 wt%, CaO 2 to 3 wt%, MgO 0.1 to 0.5% by weight, TiO ₂ 0.05 to 0.3% by weight, NaO ₂ 0.5 to 0.2% by weight, and K ₂ O A combustion additive for suppressing slagging or fouling, comprising 0.1 to 0.7% by weight.

Images