JP2002052311A - Additive for combustion exhaust gas, method for producing the same, and method for generating electricity by using the additive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an additive that can highly efficiently and safely remove sulfur oxides (SOX) by neutralization from an exhaust gas produced when a fossil fuel is combusted, more particularly, from an exhaust gas produced when a sulfur-containing fuel is combusted in, e.g. a boiler. SOLUTION: A combustion exhaust gas from a fossil fuel is neutralized by adding an additive comprising an aqueous solution of magnesium hydrogencarbonate or calcium hydrogencarbonate to the fuel, the combustion air, the flue downstream of the combustor, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an additive, a method for producing the additive, and a power generation method as one embodiment of a method for using the additive.

[0002]

2. Description of the Related Art In a thermal power plant, fossil fuels such as coal, crude oil, heavy oil, and tar are burned in a boiler together with air to obtain pressurized steam, and the steam is used to turn a turbine to generate electric power.

[0003] Since these fossil fuels usually contain sulfur, the exhaust gas contains sulfur oxides (SO _x ). Then, the exhaust gas containing the sulfur oxide is cooled, reaches the dew point, and generates sulfuric acid H ₂ SO ₄ . On the other hand, an air preheater is usually provided in the flue of exhaust gas, and when exhaust gas containing sulfuric acid passes through the air preheater, corrosion and blockage of the air preheater are caused. As a countermeasure, it is common to maintain the exhaust gas temperature below the dew point of SO ₃ .

[0004] Further, since fossil fuels contain a large amount of flame-retardant carbon such as residual carbon and fixed carbon, dust is likely to be generated in exhaust gas. Therefore, it is desired to promote the combustion of fossil fuels and suppress the flame-retardant carbon which is a main component of the dust.

Further, fossil fuels contain ash, particularly vanadium, sodium, etc., which cause problems such as boilers at high temperatures. It is desired to suppress such high-temperature damage of the ash.

[0006] Additives in which inorganic substances such as MgO, CaO and the like are made into an oil slurry are added to fuel oil to suppress the catalytic ability of vanadium, which is an SO ₃ generation catalyst contained in heavy oil and the like. A method for suppressing the generation of oxides is also known.
However, although the amount of SO ₃ generated is suppressed to about 50%, many SO 3
₃ remain.

By adding such an additive,
The unburned component, which is the main component of the dust, can also be reduced.
However, when a large amount of the additive is added, additional components are deposited on the heat transfer portion of the boiler, for example, on the wall of the heat exchanger, and the heat transfer balance is lost, so that the operation of the boiler becomes difficult.

Additives also include oil-soluble, colloidal, or calcium or magnesium acetates or nitrates. These additives are expensive and cannot be used in large quantities.

As a method of positively performing the neutralization in the middle of the flue, there is a method of injecting powder of calcium hydroxide, calcium carbonate, magnesium oxide, magnesium hydroxide, and water slurry. Many of the particle diameters of calcium hydroxide and the like in the water slurry are about 50 μm to 150 μm, and many particles of several hundred μm class are contained therein. Since the particle size is large, the reactivity is poor. In particular, when a large amount of additive is added, a large amount of the dust accumulates at the bottom of the flue at the injection point, and white dust falls. The addition is difficult. In addition, due to poor reactivity, the effect of reducing sulfuric acid mist fluttering observed as white smoke is hardly recognized.

As an active ingredient of the additive, ammonia is
Very good reactivity, increased dust collection efficiency of electric precipitator and SO ₃ and H
Widely used from corrosion by ₂ SO _4. But,
When ammonia is added, acidic ammonium sulfate and ammonium sulfite are generated. Ammonium sulfate and ammonium sulfite accumulate on the electrostatic precipitator and adhere to the discharge electrode. For this reason, the voltage value becomes high, a hunting phenomenon appears, and a failure of charging failure occurs, or the dust flows out of the chimney and becomes an acid fallen dust. In some cases, the operation is stopped and water is washed due to a relationship that the dust limit value for controlling dust causing air pollution is temporarily exceeded due to charging failure.

In addition, ammonia has many regulations and regulations and has many problems in handling, maintenance and inspection, and safety. For example, ammonia injection requires a storage and vaporization device for liquid ammonia and the like, and there are legal regulations such as high-pressure gas, toxic substances, occupational safety, and combustible gas.

Caustic soda and sodium carbonate aqueous solutions are also used as additives, and these aqueous solutions have a performance comparable to ammonia. However, since the molecular weight is larger than that of ammonia, the cost per mole is high. Also, if these aqueous solutions are added before the air heater, i.e., the air preheater, when exchanging heat between the combustion air and the exhaust gas, a large amount of sodium salts causing high-temperature obstacles will be mixed into the combustion air and enter the combustion chamber. Not so used.

[0013]

DISCLOSURE OF THE INVENTION The present invention relates to a fossil fuel exhaust gas, for example, a sulfur oxide (S) contained in an exhaust gas generated by burning a sulfur-containing fuel in a boiler or the like.
O _x), and an object thereof is particularly removed efficiently and safely neutralized the SO _3.

Further, an air preheater installed in the flue of the combustion exhaust gas, the electrostatic precipitator, in the flue side wall or the like, the exhaust gas is cooled, prevents the H ₂ SO ₄ reaches the dew point, H ₂ The purpose is to suppress corrosion and obstruction caused by SO ₄ .

It is another object of the present invention to prevent dust accumulated in a flue or the like from being discharged as a lump containing a large amount of sulfuric acid having a low pH due to load fluctuation or the like, and to suppress the generation of acid fallen dust which causes environmental degradation. And

It is another object of the present invention to suppress the failure of charging of the electrostatic precipitator and to reduce the addition of ammonia.

It is another object of the present invention to efficiently suppress high-temperature corrosion caused by vanadium and sodium contained in fuel.

It is another object of the present invention to promote the combustion of unburned carbon components and suppress the generation of dust.

Still another object of the present invention is to positively lower the exhaust gas temperature and increase the efficiency of the boiler.

Still another object of the present invention is to increase the operating rate and efficiency of a boiler or the like and to enable stable operation for a long period of time.

[0021]

Means for Solving the Problems The present inventors have studied to achieve the above object, and as a result, mixed carbon dioxide or a gas containing carbon dioxide into an aqueous liquid containing a magnesium compound or a calcium compound and water. It was found that an inexpensive additive that can efficiently and safely neutralize SO ₃ can be obtained by pressurizing and then heating this aqueous liquid.

Further, it has been found that the active ingredient is contained as extremely fine particles in the above-mentioned additive, and that it has an extremely excellent function as an additive.

In addition, in obtaining the above additive, it has been found that fossil fuel combustion exhaust gas can be used as a gas containing carbon dioxide.

Further, in thermal power generation, the above-mentioned additive is produced by using the combustion exhaust gas, and the obtained additive is used as an additive for the combustion exhaust gas of a combustion device, whereby high efficiency and carbon dioxide can be obtained. It has been found that it is possible to provide an environmentally friendly power generation method by reducing the emission of sulfur and sulfur oxides and the emission of dust.

According to a first aspect of the present invention, there is provided an additive comprising an aqueous solution of magnesium hydrogen carbonate or calcium hydrogen carbonate, wherein the concentration of the magnesium component in the additive is:
0.1 to 30% by weight in terms of MgO,
Alternatively, there is provided a combustion gas additive for a combustion apparatus, wherein the concentration of a calcium component in the additive is 0.1% by weight to 30% by weight in terms of CaO.

In a first aspect of the present invention, the additive comprises:
At least a part of magnesium hydrogen carbonate or calcium hydrogen carbonate may be dissolved in the aqueous solution, and at least a part of magnesium hydroxycarbonate or calcium hydroxycarbonate may be suspended in the aqueous solution as fine crystals. In this case, 90
It is preferable that the content by weight or more be 1 μm or less in particle size.

In a second embodiment of the present invention, a step of introducing fossil fuel exhaust gas into an aqueous liquid containing a magnesium compound or a calcium compound and water, and a step of pressurizing the aqueous liquid into which the exhaust gas has been introduced, A step of gelling carbon dioxide in an aqueous liquid, and a step of heating the aqueous liquid to a temperature equal to or higher than the gelation step and equal to or lower than the boiling point of the aqueous liquid in order to volatilize and remove the carbon dioxide gel. A method for producing an additive comprising magnesium hydrogencarbonate or calcium hydrogencarbonate, magnesium hydroxycarbonate or calcium hydroxycarbonate, and water.

In the second aspect of the present invention, the magnesium compound or the calcium compound is preferably an inorganic substance. When the aqueous liquid is pressurized, 9.8
It is preferable to apply a pressure of × 10 ⁴ Pa (1 kgf / cm ² ) or more.

In a third aspect of the present invention, a step of burning fossil fuel together with air in a combustion device to obtain steam, a step of rotating a turbine with the steam to generate electric power,
The additive according to the first aspect, or the additive obtained by the production method according to the second aspect, is used in the fossil fuel, the air, the inside of the combustion device, the combustion device and the combustion device. A connection to a downstream flue or a step of adding to the flue.

[0030] In the third aspect of the present invention, the additive may be added near an outlet of an echo section in the combustion device or near an outlet of an air preheater in the flue.

In a fourth aspect of the present invention, fossil fuel is burned together with air in a combustion device to obtain steam,
A step of obtaining exhaust gas, a step of rotating a turbine with the steam to generate electric power, a step of introducing at least a part of the exhaust gas into an aqueous liquid containing a magnesium compound or a calcium compound and water, and the step of introducing the exhaust gas. Pressurized aqueous liquid, a step of gelling carbon dioxide in the exhaust gas in the aqueous liquid, and to evaporate and remove the carbon dioxide gel, the temperature of the aqueous liquid gelling step or more, the Heating the aqueous liquid to a boiling point or lower to obtain an additive containing magnesium hydrogencarbonate or calcium hydrogencarbonate, magnesium hydroxycarbonate or calcium hydroxycarbonate, and water, and adding the additive to the fossil fuel; In air, inside the combustion device, at the connection between the combustion device and the flue downstream of the combustion device, or adding to the flue. Generator wherein is provided.

[0032] In the fourth embodiment of the present invention, the concentration of the magnesium component in the additive is 0.1% in terms of MgO.
It is preferable that the content is 1% by weight to 30% by weight, or the concentration of the calcium component in the additive is 0.1% by weight to 30% by weight in terms of CaO.

Further, in the additive, at least a part of magnesium hydrogencarbonate or calcium hydrogencarbonate is dissolved in the aqueous liquid, and at least a part of the magnesium hydroxycarbonate or calcium hydroxycarbonate is fine crystals in the aqueous liquid. It may be floating on the surface. In this case, it is preferable that 90% by weight or more of the fine crystals have a particle size of 1 μm or less.

[0034]

DETAILED DESCRIPTION OF THE INVENTION In a first aspect of the present invention, there is provided a fuel gas additive for a fuel system comprising an aqueous solution of magnesium bicarbonate or calcium bicarbonate.

When the additive according to this embodiment is composed of an aqueous solution of magnesium hydrogen carbonate, the concentration of the magnesium component in the additive is 0.1% by weight to 30% by weight in terms of MgO. When the additive comprises an aqueous solution of calcium hydrogen carbonate, the concentration of the calcium component in the additive is 0.1% by weight to 30% by weight in terms of CaO.

When the amount of the active ingredient in the additive is within the above range, a large amount of the additive is required, and as a result, there is little problem that the equipment such as a tank and a transfer pump becomes too large and the equipment cost increases. ,preferable. Further, when the content is within the above range, the active ingredient can be stably dissolved even at a low temperature in winter, so that it is preferable. On the other hand, if the amount of water in the additive is too large, it will affect the temperature and efficiency of the exhaust gas when added to the exhaust gas, and there is evidence that water will accumulate at the point of addition. It is not preferable because it causes rust in the flue and flue.

Further, in the additive according to the present embodiment, at least a part of magnesium hydrogen carbonate or calcium hydrogen carbonate may be dissolved in the aqueous solution, and at least a part of the magnesium hydroxycarbonate or calcium hydroxycarbonate may be in the form of fine crystals. It may be suspended in the aqueous solution.

It is to be noted that 90% by weight or more of the fine crystals is
The particle size is preferably 1 μm or less, more preferably 0.1 μm or less. This is because the smaller the particle size is, the larger the surface area is, so that the effect as an additive is improved.

The additive according to the present embodiment may contain, in addition to the above components, other components such as impurities, for example, silica and the like.

According to a second aspect of the present invention, there is provided a method for producing an additive comprising magnesium or calcium hydrogencarbonate, magnesium or calcium hydroxycarbonate, and water.

The production method according to the present embodiment includes a step of introducing fossil fuel exhaust gas into an aqueous liquid containing a magnesium compound or a calcium compound and water, and a step of pressurizing the aqueous liquid into which the exhaust gas has been introduced, and A step of gelling carbon dioxide in an aqueous liquid, and at least the temperature of the gelling step of the aqueous liquid to volatilize and remove the carbon dioxide gel,
Heating to below the boiling point of the aqueous liquid.

Preferred examples of the magnesium compound include inorganic magnesium compounds. Examples of the inorganic magnesium compound include, for example, MgO, Mg (OH) ₂ , MgCO
₃ , MgO, Mg (OH) ₂ , and MgCO ₃ , preferably MgO.

The calcium compound is preferably an inorganic calcium compound. As the inorganic calcium compound, for example, CaO, Ca (OH) ₂ , CaCO
₃ and preferably CaO.

As fossil fuels, fossil fuels containing carbon can be used without particular limitation. For example, petroleum, crude oil,
Naphtha, light oil, kerosene, heavy oil, asphalt, orinoco tar, orimulsion, oil shell, oil sand,
Oil coke, blast furnace gas, liquefied natural gas (LNG),
Liquefied petroleum gas (LPG) and the like can be mentioned. In particular, the present invention can be suitably applied to fossil fuels having a relatively high sulfur content.

In the method for producing an additive according to the present invention, fossil fuel exhaust gas is introduced into an aqueous liquid containing a magnesium compound or a calcium compound and water, and then the aqueous liquid is pressurized. Pressurizing the aqueous liquid causes the carbon dioxide in the exhaust gas to gel with the aqueous liquid. At this time, the magnesium compound or the calcium compound in the aqueous liquid becomes magnesium hydrogen carbonate or calcium hydrogen carbonate, and is considered to be dissolved in the aqueous liquid.

The pressure to be applied is 9.8 × 10 ⁴ Pa (1 k
gf / cm ² ) or more, preferably 49 × 10 ⁴ Pa
(5 kgf / cm ² ) or more.

Next, this aqueous liquid is heated to a temperature higher than the temperature of the gelling step and lower than the boiling point of the aqueous liquid to volatilize and remove the carbon dioxide gel. Through the above steps, fine crystals of magnesium hydroxycarbonate or calcium hydroxycarbonate can float in the aqueous liquid. As described above, an active ingredient such as magnesium hydrogencarbonate or calcium hydrogencarbonate, magnesium hydroxycarbonate or calcium hydroxycarbonate can be obtained as extremely fine particles. Since the superiority and the inferiority of the performance of the additive are determined by the particle diameter, a very excellent additive can be obtained by the above method.

It also increases the stability of the additives,
From the viewpoint of improving the dispersibility of the additive in the additive, an oil, an emulsifier, and the like can be further added to the additive.

According to a third aspect of the present invention, there is provided a power generation method which is an application example of the additive according to the first aspect and the additive obtained by the production method according to the second aspect.

In the power generation method according to this aspect, the step of burning the fossil fuel together with the air in the combustion device to obtain steam, the step of rotating the turbine with the steam to generate power, and the step of adding the additive to the fossil fuel Medium, in the air, inside the combustion device, a connection between the combustion device and a flue downstream of the combustion device, or adding to the flue.

The position where the additive is added will be described with reference to FIG. FIG. 1 is a schematic diagram of a boiler and a flue in a power generator. The boiler has a furnace 1, a heater 3 for heating the furnace 1, and an echo unit 2. A fuel pipe for adding fuel and a pipe for introducing combustion air are connected to the boiler, and an oil heater for previously heating the fuel is arranged in the fuel pipe,
A burner for preheating the air is disposed in the fuel air introduction pipe. In addition, a denitration device (not shown) for removing nitrogen oxides may be installed near the outlet of the boiler.

A flue is formed between the exhaust gas outlet of the boiler and the chimney 7. In the flue, air preheater 4,
An electrostatic precipitator 5 for removing dust in exhaust gas, and
A wet desulfurization device 6 for spraying a desulfurizing agent is arranged in this order from upstream to downstream. Although the desulfurization device 6 and the denitration device are installed for the purpose of improving air pollution, they are also particularly effective in preventing adhesion of acidic ammonium sulfate and the like to the air preheater 4 in the denitration device.

In this specification, a flue means a flow path of exhaust gas in a combustion device such as a boiler, and also includes a flow path inside a chimney.

In the present invention, the locations where the additives are injected include fuel, combustion air, the inside of a combustion device such as a boiler, the connection between the combustion device and the flue downstream of the combustion device, and the flue. Can be mentioned. For example, as shown in FIG. 1, it may be added to a fuel pipe, an intake pipe for combustion air, the inside of a boiler, and the like. Further, the flue downstream of the boiler, that is, near the outlet of the boiler, in front of the air preheater 4, between the air preheater 4 and the electric precipitator 5, between the electric precipitator 5 and the desulfurizer 6, It may be added to the flue between the desulfurization device 6 and the chimney 7, the flue inside the chimney 7, and the like. The addition site is appropriately selected according to the purpose as described later.

According to a fourth aspect of the present invention, in a power generation method for generating electric power by burning fossil fuel, an additive is produced using exhaust gas generated by combustion of fossil fuel, while the additive is produced. A power generation method for performing the addition is provided.

The power generation method according to this aspect includes a step of burning fossil fuel with air in a combustion device to obtain steam and obtaining exhaust gas, a step of rotating a turbine with the steam to generate electric power, and a step of generating electric power. A step of introducing at least a part into an aqueous liquid containing a magnesium compound or a calcium compound and water, and a step of pressurizing the aqueous liquid into which the exhaust gas has been introduced and gelling carbon dioxide in the exhaust gas in the aqueous liquid. And, in order to volatilize and remove the carbon dioxide gel, the aqueous liquid is heated to a temperature equal to or higher than the temperature of the gelling step and equal to or lower than the boiling point of the aqueous liquid, and magnesium hydrogen carbonate or calcium hydrogen carbonate, and magnesium hydroxycarbonate or Obtaining an additive comprising calcium hydroxycarbonate and water; and adding the additive in the fossil fuel, the air, the fuel, Internal device, the connection portion of the downstream flue of the combustion apparatus and the combustion apparatus, or a step of adding to the flue.

The description of the fossil fuel, various compounds, the combustion device, the flue, and the like is as described in the preceding embodiment.

Next, the amount and location of the additive according to the present invention will be described for each purpose.

In order to prevent clogging and corrosion of the air preheater by SO ₃ , the above additive is added to MgO or Ca per mole of SO _3.
In terms of O, the added amount is 0.01 mol to 5 mol,
It is preferable to inject into the exhaust gas channel between the combustion device and the air preheater.

To suppress the acid deposition, the above additives are used.
It is preferable to inject from the boiler outlet to the flue between the chimneys at an addition amount of 1% by weight to 20% by weight based on the amount of dust.

To suppress charging failure of the electrostatic precipitator and to reduce ammonia, the above additive is added in an amount of 1% by weight to 2% by weight based on the amount of dust.
It is preferable to inject from the boiler outlet to the flue between the electric precipitator and the addition amount so as to be 0% by weight.

When the injection of ammonia into the electrostatic precipitator is replaced with the injection of the above-mentioned additive, the above-mentioned additive is used in an amount of 1 to 20 mol per ₃ mol of SO from the boiler outlet to the electric precipitator. Preferably, it is injected into the flue.

For suppressing fluttering of white smoke in a flue gas desulfurization apparatus or the like, the above additive is added in an amount of 0.1 to 20 mol with respect to sulfuric acid (converted to 1 mol of SO ₃ ). Preferably, the fuel is injected from a boiler outlet to a flue downstream.

When treating the combustion exhaust gas of a fossil fuel containing vanadium, sodium, or sulfur, the above additive is used to suppress high-temperature corrosion typified by so-called vanadium attack and high-temperature sulfide corrosion = sulfur attack. 0.1ppm to 1000ppm in terms of MgO or CaO for fuel
In addition amount, also, Mg or Ca / V, Mg or Ca / N
It is desirable that a or Mg or Ca / S be added to fuel or combustion air such that the weight ratio becomes 0.1 to 3.

In order to suppress the generation of SO ₃ , the above additive is added to the fossil fuel at 0.1 ppm to 1000 pp in terms of MgO or CaO.
m, Mg or Ca / V, Mg or Ca /
It is desirable to add Na or Mg or Ca / S to the fuel or combustion air such that the weight ratio is 0.1 to 3.

In order to suppress the dust which is the main component of unburned carbon, the above additive is added to fossil fuel in the amount of 0.1 p in terms of MgO or CaO.
pm to 1000 ppm, in addition, Mg or Ca /
V, Mg or Ca / Na, or Mg or Ca / S, in a weight ratio of 0.
It is desirable to add to fuel or combustion air so as to be 1 to 3.

The relative amount of the additive depends on the flow rate of the smoke in the flue. In general, when the flow rate is high, the amount of the additive tends to increase. Also, by increasing the amount of the additive, the temperature of the exhaust gas can be reduced, and the boiler efficiency is improved.

The characteristics of the use of the additive according to the present invention will be described below. 1. When the additive is spouted into a high-temperature exhaust gas and injected finely, fine particles are obtained as compared with a solid such as a powder. Furthermore, SO ₃ is condensed as H ₂ SO _{4 due} to the latent heat of evaporation of water. Before the water droplets evaporate, the temperature of the water droplet surface is low and sulfur oxides, particularly SO _3, are easily adsorbed and dissolved, so that very quick neutralization is performed. As a result, harmless MgSO ₄ and CaSO ₄ are generated. 2. The use of an additive as a neutralizing agent allows safe handling because there is no regulation of high-pressure gas and noxious poisons as compared with ammonia. 3. Since it is a water liquid, it can be injected more accurately than powder, and stable and accurate neutralization can be performed. 4. Even when the temperature of the exhaust gas is lowered, the flue is not clogged, so that the boiler efficiency is improved.

[0069]

Embodiment 1

As the MgCO ₃ , a commercially available magnesite (purity 95%) in northeastern China, especially in the vicinity of Haicheng City was used without purification. Magnesite powder of 100 mesh or less was added to industrial water so as to be 10% by weight in terms of MgO, and then stirred to obtain a suspension of MgCO ₃ . The suspension was stirred while introducing exhaust gas into the suspension from a boiler burning heavy oil. Table 1 shows the specifications and exhaust gas composition of this boiler. In the examples, kg
f / cm ² refers to 9.8 × 10 ⁴ Pa.

[0071]

[Table 1] Then, the suspension was cooled to 5 kgf / cm ² at room temperature with a compression pump.
Pressure was applied to the suspension to obtain a translucent solution. Magnesium bicarbonate is produced. Subsequently, the mixture was heated to about 60 ° C. or higher to obtain an additive aqueous solution.

The aqueous solution of the additive thus obtained is
Using the addition amount shown in Table 2 as the converted amount of MgO with respect to SO ₃ , the number of times of water washing required by clogging of the air preheater with SO ₃ and the amount of corrosion by the test piece were measured. While the additive solution has a pressure of 5 kgf / cm ^2,
The fuel was injected into the flue between the boiler and the air preheater. The boiler and the flue shown in FIG. 1 were used as the boiler and the flue. The boiler has a furnace 1, a heater 3 for heating the furnace 1, and an echo unit 2. A flue is formed between the exhaust gas outlet of the boiler and the chimney 7. In the stack, an air preheater 4, an electric precipitator 5 for removing dust in exhaust gas, and a wet desulfurizer 6 for spraying additives are arranged in this order from upstream to downstream. The test piece used was plain steel and had an original weight of 11.5 g. Table 2 shows the test results.

[0073]

[Table 2] As can be seen from Table 2, the addition of the additive aqueous solution containing 1 mole of magnesium component to SO ₃ ensures that the air preheater does not become clogged during one year of operation and does not require a single water wash. I understand. In addition, it was found that the addition of the additive aqueous solution reduced the corrosion amount by the test piece by nearly 93%, and it is expected that the operation rate will be improved and the life of the air preheater will be extended. By adding an additive aqueous solution containing only 0.01 mol of a magnesium component to SO ₃ , water was washed about once every three months before the addition, but the number of times of water washing was 2 to 3 times throughout the year. It can be seen that the improvement has been made to the extent necessary, and the corrosion amount due to the test piece has been reduced by nearly 70%.

Further, in Example 1 in which the aqueous solution of the additive was added to the flue, even when the temperature of the exhaust gas discharged from the air preheater was reduced from 160 ° C. to 70 ° C., an increase in the differential pressure due to clogging was observed. Was not done. Thus, the boiler efficiency was improved from 89% to 92% by lowering the exhaust gas temperature, and energy was saved. In highly technical fields such as boilers, the improvement of thermal efficiency by improving the boiler itself is almost at its limit, and a 3.0% increase is a remarkable effect. Also, when the amount of the additive aqueous solution is large, the temperature of the exhaust gas can be further reduced, and the energy can be further saved.

[0075] molar concentration of the additive solution, MgO, relative terms there is no difference in but saw changes basically be used in the range of 0.1 wt% to 20 wt% in concentration, SO ₃ additive solution of CaO It has been found that the ratio has a greater effect.

Embodiment 2

The same procedure as in Example 1 was carried out except that the location of the additive aqueous solution obtained in Example 1 was in the flue between the air preheater 4 and the electrostatic precipitator 5. Was injected into the flue, and a test was conducted to examine the effect of the ash on the electric precipitator on the pH and the acid deposition dust. However, the addition amount of the additive aqueous solution with respect to the dust amount is as shown in Table 3. The boiler specifications and the exhaust gas composition at the time of the test are the same as in Example 1. Table 3 shows the test results.

[0078]

[Table 3] From Table 3, it can be seen that the addition of the additive aqueous solution has a great effect on the pH of the precipitator ash and the acid deposition dust, and it is recognized that the effect is sufficiently achieved.

In Example 2, it was confirmed that the addition of the additive aqueous solution had a remarkable effect on preventing the charging failure of the electrostatic precipitator. The aqueous additive solution obtained in Example 1 was mixed with SO ₃
To the flue between the air preheater 4 and the electrostatic precipitator 5 at the amount shown in Table 4 in terms of MgO conversion, the addition of the additive aqueous solution, and the driving state of the electric precipitator The relationship between the injection amount of ammonia, the pH of the ash of the electrostatic precipitator, and the state of charge of the electric precipitator was examined. Measurement of the charging status of the electric dust collector
The current value was measured at the time of driving the boiler and one month after driving. The results are shown in Table 4.

[0080]

[Table 4] Since the aqueous solution of the additive according to the present invention is an alkaline substance, it is possible to increase the electric resistivity of the dust and simultaneously increase the pH of the ash of the electrostatic precipitator to convert the acidic ammonium sulfate to normal ammonium sulfate. For this reason, the hygroscopicity of the electric dust collector ash is reduced, and the fluidity is improved. As a result, as can be seen from Table 4, clogging of the electric precipitator is improved. Also, since the pH increased, 50% of the injection amount of ammonia
The above can be reduced.

The concentration of the additive aqueous solution was changed in the range of 0.1% by weight to 20% by weight in terms of the concentration of MgO and CaO, and MgO and CaO were added to 1 mole of SO _{3 in} the exhaust gas. When the aqueous solution of the additive was added to the flue between the air preheater 4 and the electrostatic precipitator 5 in the range of 1 mol to 20 mol as a converted component, the pH became close to 7, and even if the ammonia injection was stopped, pH5
Since it was changed in the range of ~ 6, it was proved to be a substitute for ammonia. This phenomenon is due to the fact that Mg and Ca salts form sulfate, but acidic sulfate is hardly produced at pH 4 or higher.

The aqueous solution of the additive according to the present invention can be obtained by using a magnesium compound or a calcium compound which is inexpensive as compared with ammonia. It is easier to handle and store than ammonia. Therefore, the economic improvement is of great value.

Embodiment 3

There is a phenomenon in which white smoke discharged from the wet desulfurization apparatus flutters for a long time, which is a kind of pollution.

Shortening of white smoke during the test in Table 4 above
Was observed. The main cause of white smoke is SO _ThreeIn the desulfurization unit
Sulfuric acid mist is formed by rapid cooling in the process of contacting with sulfuric water.
It is. The additive aqueous solution according to the present invention
SO_ThreeBy dew condensation absorption and concentration, SO_ThreeThe magnesium sulfate,
Calcium sulfate promotes moisture evaporation of white smoke.

Therefore, the same procedure as in Example 1 was carried out except that the addition position of the aqueous solution of the additive obtained in Example 1 was in the flue between the electrostatic precipitator 5 and the desulfurizer 6. Was injected into the flue, and the relationship between the addition of the aqueous additive solution and white smoke was examined. Table 5 shows the results. However, the additive aqueous solution is SO ₃
The amount of MgO was used as the conversion amount of MgO in the amount shown in Table 5.

[0087]

[Table 5] Table 5 shows values obtained by visually observing the fluttering of white smoke.
It can be seen that the flutter is clearly shortened by the slight addition of the additive aqueous solution.

Embodiment 4

The aqueous solution of the additive obtained in Example 1 was injected into combustion air and into a fuel pipe, and the amount of dust and the amount of reduction in SO ₃ were examined. Table 6 shows the specifications and fuel properties of the boiler used.

[0090]

[Table 6] In the practical boiler, the ratio greatly changes due to co-firing of C heavy oil and asphalt, and in some cases, it may be close to asphalt-only firing. Using the boiler shown in Table 6, the additive aqueous solution was added such that the weight ratio (Mg / V) between the magnesium component in the additive aqueous solution and the vanadium component in the fuel became the weight ratio shown in Table 7. The amount of the additive aqueous solution was adjusted to the amount shown in Table 7 with respect to the fuel. In order to investigate whether the effect differs depending on the position of addition of the additive aqueous solution, the additive aqueous solution was added to two locations in the fuel pipe and the combustion air, and the effect was examined. The addition to the fuel pipe was performed by injecting the additive aqueous solution into the fuel pipe line downstream of the oil heater with a proportional injection pump. Further, the addition to the combustion air was performed by adding to the upstream side of the burner with a sprayer. The measurement of the amount of dust was carried out by the constant-pressure suction silica wool cylindrical filter paper method (JIS-
Z-8808), and SO ₃ was measured by a condensation method. Table 7 shows the results.

[0091]

[Table 7] From Table 7, it can be seen that the additive aqueous solution has a great effect on the reduction of the amount of dust and the reduction of the amount of SO _3, which is a main factor that adversely affects the boiler. Particularly, Mg / V (weight ratio) is about 3.
0, also when the addition amount of the additive solution is about 1000ppm with respect to the fuel, up to the reducing effect of the dust amount and SO ₃ amount greater than or equal to about 50%, the additive solution is, conventional heavy oil additives It can be seen that an effect equal to or higher than that of the agent was obtained. Also, from Table 7, it can be seen that the same effect can be obtained regardless of the difference in the addition position such as in the fuel pipe or in the combustion air.

Embodiment 5

Using the additive aqueous solution obtained in Example 1, a high-temperature corrosion test of a heater was performed. Table 8 shows the specifications and fuel properties of the boiler used.

[0094]

[Table 8] Using the boiler shown in Table 8, the weight ratio of the magnesium component in the additive aqueous solution to the vanadium component in the fuel (Mg /
V) was added to be 0.1. To improve the dispersibility of the additive in heavy oil, add 20% by weight of the additive aqueous solution.
An emulsifier was added to the contained gas oil to form an emulsion. The emulsion thus obtained was added to a fuel pipe at 100 ppm in terms of MgO with respect to the fuel. The addition to the fuel pipe was performed by injecting the additive emulsion into the fuel pipe line downstream of the oil heater with a proportional injection pump. The high-temperature corrosion test of the heater was performed by using the boiler for about one year while adding the additives, and measuring the wall thinning of the water tube of the heater at the time of periodic repair of the boiler about one year later. Table 9 shows the measurement results.

[0095]

[Table 9] From Table 9, it was confirmed that when the additive was not added, the wall loss of the water tube tube was reduced to about 0.48 mm per year. .

[0096]

According to the additive of the present invention, sulfur oxides in fossil fuel combustion exhaust gas can be efficiently and safely neutralized and removed, and various problems associated with the generation of sulfur oxides can be achieved. For example, the generation of acidic dustfall that causes environmental degradation,
Air preheater installed in the flue of fossil fuel combustion exhaust gas,
Corrosion of the electric precipitator and the flue side wall, obstruction obstruction, fluttering of white smoke, poor charging of the electric precipitator and the like can be suppressed.

Further, high temperature corrosion due to vanadium and sodium contained in the fuel can be efficiently suppressed.

Further, the generation of dust can be suppressed.

According to the power generation method of the present invention, since the additive having the above characteristics is used, in addition to the above effects, the temperature of the exhaust gas can be positively lowered, and the efficiency of a combustion device such as a boiler can be increased. Can be done. Further, the operating rate and efficiency of a combustion device such as a boiler can be increased, and stable operation can be performed for a long period of time.

According to the power generation method of the present invention,
While the additive having the above characteristics is produced using the exhaust gas, the additive thus obtained is added. Therefore, in addition to the above-described effects, an environment-friendly and energy-saving power generation method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a boiler and a flue in a power generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace 2 Echo part 3 Heater 4 Air preheater 5 Electric precipitator 6 Desulfurizer 7 Chimney

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10L 1/12 B01D 53/34 124Z 4H015 10/04 ZAB F23J 15/00 F23J 15/00 Z F23K 5/08 F-term (reference) 3K068 AA01 AA11 AB05 EA01 3K070 DA03 DA04 DA07 DA11 DA38 DA81 DA83 4D002 AA02 AC01 BA03 CA11 DA05 DA06 DA12 DA16 EA06 GA01 GB08 GB12 GB20 4G076 AA16 AB02 AB06 AB09 BA34 BA42 BD04 CA14 CA26 DA23 DA29 4A BB11

Claims (12)

[Claims] An additive comprising an aqueous solution of magnesium hydrogen carbonate or calcium hydrogen carbonate, wherein the concentration of a magnesium component in the additive is 0.1% in terms of MgO.
% To 30% by weight, or the concentration of the calcium component in the additive is 0.1% by weight in terms of CaO.
An additive for a combustion exhaust gas of a combustion device, wherein the additive amount is up to 30% by weight. 2. At least a part of magnesium hydrogen carbonate or calcium hydrogen carbonate is dissolved in said aqueous solution,
The additive according to claim 1, wherein at least a part of the magnesium hydroxycarbonate or the calcium hydroxycarbonate is suspended in the aqueous solution as fine crystals. 3. The additive according to claim 2, wherein 90% by weight or more of the fine crystals have a particle size of 1 μm or less. 4. A step of introducing fossil fuel exhaust gas into an aqueous liquid containing a magnesium compound or a calcium compound and water; and pressurizing the aqueous liquid into which the exhaust gas has been introduced, and converting carbon dioxide in the exhaust gas into the aqueous liquid. And a step of heating the aqueous liquid to a temperature equal to or higher than the temperature of the gelling step and equal to or lower than the boiling point of the aqueous liquid in order to volatilize and remove the carbon dioxide gel. A method for producing an additive comprising calcium hydrogen, magnesium hydroxycarbonate or calcium hydroxycarbonate, and water. 5. The method for producing an additive according to claim 4, wherein the magnesium compound or the calcium compound is an inorganic substance. 6. When the aqueous liquid is pressurized, 9.8 × 1
0 ⁴ manufacturing method of additive according to claim 4 or 5 applies pressure over Pa. 7. The additive according to any one of claims 1 to 3, wherein a step of burning the fossil fuel with air in a combustion device to obtain steam, a step of rotating a turbine with the steam to generate electric power, Or claim 4
The additive obtained by any one of the manufacturing methods of (1) to (6), in the fossil fuel, in the air, inside the combustion device, a connection between the combustion device and a flue downstream of the combustion device, or Adding to the flue. 8. The power generation method according to claim 7, wherein the additive is added near an outlet of an echo unit in the combustion device or near an outlet of an air preheater in the flue. 9. A step of burning fossil fuel with air in a combustion device to obtain steam and obtaining exhaust gas, a step of rotating a turbine with the steam to generate electric power, and converting at least a part of the exhaust gas into magnesium. A step of introducing a compound or a calcium compound and water into an aqueous liquid, pressurizing the aqueous liquid into which the exhaust gas has been introduced, and gelling carbon dioxide in the exhaust gas in the aqueous liquid; and In order to volatilize and remove, the aqueous liquid is heated to a temperature equal to or higher than the temperature of the gelling step and equal to or lower than the boiling point of the aqueous liquid, and magnesium hydrogen carbonate or calcium hydrogen carbonate, magnesium hydroxycarbonate or calcium hydroxycarbonate, and water Obtaining an additive comprising: adding the additive in the fossil fuel, in the air, in the combustion device, in the combustion; Connection of the downstream flue location and the combustion apparatus, or the power generation method characterized by comprising the a step of adding to the flue. 10. The concentration of the magnesium component in the additive is 0.1% by weight to 30% by weight in terms of MgO, or the concentration of the calcium component in the additive is
The power generation method according to claim 9, wherein the amount is 0.1% by weight to 30% by weight in terms of CaO. 11. At least a part of magnesium hydrogencarbonate or calcium hydrogencarbonate is dissolved in said aqueous liquid, and at least part of magnesium hydroxycarbonate or calcium hydroxycarbonate is suspended in said aqueous liquid as fine crystals. The power generation method according to claim 9. 12. The power generation method according to claim 9, wherein 90% by weight or more of the fine crystals have a particle size of 1 μm or less.