JPH06146862A - Exhaust gas treatment method for internal combustion engine and device for the same - Google Patents

Abstract

PURPOSE:To neutralize and remove SOx, NOx, and other poisonous elements adhered to and absorbed in water by arranging a temperature lowering water adding part of exhaust gas for lowering a temperature of the exhaust gas, and sending the exhaust gas to a neutralizer which stores solid alkali. CONSTITUTION:Exhaust gas generated through combustion in an internal combustion engine is treated by a process including the steps of adding water, and making the water to be in contact with a solid alkali. SOx or NOx contained in the exhaust gas can be dissolved into water, so that capturing effect of the SOx, NOx is improved by atomizing water in the exhaust gas and increasing a contact ratio. The water absorbing SOx, NOx is stored in a neutralizer, for neutralizing through contact with the solid alkali stored in the neutralizer. Odor of the exhaust gas is eliminated accordingly, and causes for acid rain, corrosion of concrete, and photochemical smog are eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment method and apparatus for an internal combustion engine using city gas or liquefied petroleum gas (hereinafter referred to as LPG) as a fuel.

[0002]

2. Description of the Related Art In recent years, fossil fuels such as city gas or LPG have been widely used as fuels for small stationary internal combustion engines such as internal combustion engines for gas heat pumps (GHPs). As is well known, these city gases or LPGs are usually odorized by odorous components (often S-containing compounds) so that gas leaks can be easily detected and confirmed.

[0003]

The exhaust gas generated from an engine that uses fossil fuel as described above contains CO, CH, and NO.
x, SOx, etc. are included, which cause acid rain, corrosion of buildings, photochemical smog, etc., causing environmental damage and becoming a major social problem. Large-scale ships and thermal power plants that consume large-scale fossil fuels purify SOx and NOx contained in exhaust gas and release them into the atmosphere. Purification is mandatory.

Said GH using city gas or LPG
The internal combustion engine for P has the characteristic that it is a clean engine with a small amount of HC and CO in the exhaust gas, but because it mixes and burns the fuel gas and air, NOx is inevitably generated, and these fuel gases are also generated. Since this has a large hydrogen content, this exhaust gas also contains a large amount of H ₂ O (water). Furthermore, SOx generated from the combustion of odorants is also included, and these together form an acidic liquid. By the way, since the GHP system including the GHP internal combustion engine is a system that drives the compressor by the GHP internal combustion engine to perform cooling and heating, it is often installed near a house or on a rooftop of a building. For this reason, there is a problem that the acidic liquid generated from the GHP internal combustion engine causes corrosion of the metal or concrete structure constituting the house or building. For the treatment of NOx, a catalytic reduction method using ammonia gas is generally used when a fixed device is the source. In this case, platinum (Pt) or titanium oxide, vanadium oxide (TiO
_2- V ₂ O ₅ ) is used to reduce NOx to nitrogen by the following reaction.

4NO + 4NH ₃ ＋ O ₂ → 4N ₂ ＋ 6H ₂ O NO ＋ NO ₂ ＋ 2NH → 2N ₂ ＋ 3H ₂ O For a moving internal combustion engine such as an automobile, Pt ・ Rh ・ Pd
Often a three-way catalyst of the system is used. However, when ammonia gas is used, a reactor and an ammonia storage tank are required, which makes the device bulky, and it is necessary to worry that harmful ammonia gas leaks. Further, when the three-way catalyst used in the automobile is used, there is a problem that the range of use is limited. This is because in the case of fuel for automobiles, since the S content is removed by the desulfurization device at the fuel production stage, it is not possible to desulfurize exhaust gas of an internal combustion engine using S-containing fuel using the above-mentioned three-way catalyst. .

An object of the present invention is to solve the above problems in the prior art and to provide a processing method and apparatus for purifying exhaust gas of an internal combustion engine using small stationary city gas or LPG as a fuel.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies, and as a result, by cooling exhaust gas of an internal combustion engine, harmful components such as NOx and SOx are absorbed in water. ), And it came to complete the present invention. That is, according to the present invention, an exhaust gas outlet for an internal combustion engine that uses city gas or liquefied petroleum gas as a fuel is provided with a water addition unit for lowering the temperature of the exhaust gas to lower the exhaust gas to a predetermined temperature, and the temperature of the exhaust gas becomes low. The exhaust gas is passed through a neutralizer containing a solid alkali to neutralize and remove SOx, NOx and other harmful components adhering to and absorbed in water. It is a summary.

Further, it is also a gist of the present invention to deodorize the exhaust gas by adding ozone before adding water to the exhaust gas. Furthermore, the present invention is an exhaust gas treatment device for an internal combustion engine that uses city gas or liquefied petroleum gas as a fuel, in which an exhaust gas temperature lowering water addition section and a neutralizer containing solid alkali are sequentially arranged in the exhaust gas passage. An exhaust gas treatment device for an internal combustion engine, which is characterized in that

[0009]

The structure and operation of the present invention will be described. The method of the present invention comprises a step of treating the exhaust gas burned in the internal combustion engine with a combination of the step of adding water and the step of bringing the water into contact with a solid alkali.

SOx or NOx contained in exhaust gas
Is soluble in water and its aqueous solution exhibits acidity. However, when such a gas dissolves in water, the lower the temperature of the liquid, the more the gas dissolves. In addition, the larger the surface area of water in contact with the gas, the more easily it is dissolved or absorbed. Therefore, by spraying water into the exhaust gas, the temperature of the exhaust gas is lowered and the surface area of the water is increased to increase the contact ratio with SOx and NOx and enhance the collection effect. The amount of water added is such that the exhaust gas temperature is kept below 98 ° C. Preferably
70 ° C or lower is more effective. At temperatures above 98 ° C,
SOx and NOx are volatilized again from the aqueous solution, and the absorption effect does not increase. The total amount of water added to the exhaust gas depends on the amount of harmful components in the exhaust gas. The amount of water expected from the temperature of the exhaust gas varies depending on the structure of the treatment equipment, but it is 150
40 to 20 liters per hour at ℃, the amount of harmful components is 400 to 1500 m
In g / m ³ , 4 to 20 liters / hour is a preferable amount of water added. Addition of a large amount of water is uneconomical and the function of the neutralizer is significantly deteriorated. If water is insufficient, sufficient removal of harmful components cannot be achieved.

As described above, SOx and NO which are harmful components
The water that has absorbed x comes into contact with the solid alkali contained in the neutralizer and is neutralized. As the solid alkali, salts such as calcium carbonate, potassium carbonate and sodium carbonate, calcium hydroxide and the like can be used. The use of water-insoluble calcium carbonate or sparingly soluble calcium hydroxide is advantageous because the treated water tends to be neutral (pH 7).

When the exhaust gas is simply passed through the neutralizer without using water, almost no harmful components are removed. The pH of the water containing the harmful components is preferably about 5 to 6. The reaction of harmful components with water by adding water is as follows. 1. NO + NO ₂ + H ₂ O → 2HNO ₂ 2.3NO ₂ + H ₂ O → 2HNO ₃ + NO 3.4NO ₂ + 2H ₂ O + O ₂ → 4HNO _{3 In} addition, these aqueous solutions and the neutralizing agent react as follows. CaCO ₃ + 2HNO ₂ → Ca (NO ₂ ) ₂ + H ₂ CO ₃ Ca (OH) ₂ + 2HNO ₃ → Ca (NO ₃ ) ₂ + H ₂ O Ca (OH) ₂ + 2HNO ₃ → Ca (NO ₂ ) ₂ + H ₂ O The following is the case when SO ₂ based on the odorant enters the fuel gas. 1.2NO + SO ₂ + H ₂ O → N ₂ O + H ₂ SO ₄ 2. H ₂ O + SO ₃ → H ₂ SO ₄ 3. NO + NO ₂ + H ₂ O → 2HNO ₂ 4.3NO ₂ + H ₂ O → 2HNO ₃ + NO 5.4NO ₂ + 2H ₂ O + O ₂ → 4HNO ₃ The neutralization reaction of the above aqueous solution is as follows.

[0013] The above-mentioned reaction with water is carried out in the water addition section shown in FIGS. 1, 2 and 3, and the neutralization reaction is carried out in the neutralizer.

When O ₃ is added to the exhaust gas by the ozone generator, the following reaction is considered. NOx: 1. NO + O ₃ → NO ₂ ＋ O ₂ └ → 4NO ₂ ＋ 2H ₂ O ＋ O ₂ → 4HNO ₃ 2HNO ₃ ＋ CaCO ₃ → Ca (NO ₃ ) ₂ ＋ H ₂ O ＋ CO ₂ Odorant: CH ₃ −SH + O ₃ → CH ₃ − _{OH + SO 2 3CH 3 -S-} CH 3 + 4O 3 → 6CH 3 OH + 3SO 2 SO 2 + H 2 O + 1/2 O 2 → H 2 SO 4 H 2 SO 4 + CaCO 3 → CaSO 4 + H 2 O + CO 2 4 the reaction It is a schematic diagram of an apparatus for performing. Also,
FIG. 5 shows a schematic sectional view of an apparatus for carrying out the present invention.

[0015]

EXAMPLES The present invention will be specifically described by way of examples, which should not be construed as limiting the invention. (Example 1) A device for generating, adding, and decomposing ozone by using a device for adding water at a rate of 4 L / H by combining exhaust gas with NOx amount of 700 ppm as shown in Fig. 5 [Ozone generator: Nippon Special Ceramic Industry Co., Ltd. OU-65A, Ozone decomposition catalyst: Sakai Chemical Industry Co., Ltd.
SCH-120] and 2 kg of calcium carbonate [Shiraishi Industry Co., Ltd.] were used to obtain the following effects.

[0016]

[Table 1]

(Example 2) Using an apparatus for adding water at a rate of 6 L / H in combination with exhaust gas having an NOx amount of 1300 ppm in the same manner as in Example 1, and using 3 kg of calcium carbonate [Shiraishi Industry Co., Ltd.] As a result of using the neutralizing device, the following effects were obtained.

[0018]

[Table 2]

(Example 3) An apparatus for adding water at a rate of 1 L / H in combination with exhaust gas having NOx amount of 1100 ppm in the same manner as in Example 1 was used, and 2 kg of calcium carbonate [Shiraishi Industry Co., Ltd.] was used. As a result of using the neutralizing device, the following effects were obtained.

[0020]

[Table 3]

(Embodiment 4) An apparatus for generating, adding and decomposing ozone by using an apparatus for adding 1100 ppm of NOx to the exhaust gas in the same manner as in Example 1 and adding water at a rate of 1 L / H [Ozone generation Machine: Nippon Special Ceramics Co., Ltd. OU-65A, ozone decomposition catalyst: Sakai Chemical Industry Co., Ltd. SCH-120] and calcium carbonate 2 kg
The following effects were obtained as a result of using the neutralization device using [Shiraishi Industry Co., Ltd.].

[0022]

[Table 4]

(Example 5) Using an external cooler for circulating water by combining exhaust gas with NOx amount of 1100 ppm as shown in FIG. 4 and a device for adding water at a rate of 4 L / H, 2 kg of calcium carbonate [Shiraishi] The following effects were obtained as a result of using a neutralization device using Industrial Co., Ltd.].

[0024]

[Table 5]

(Example 6) Exhaust gas containing odorous component dimethyl sulfide (DMS): H ₃ C-S-CH ₃ 10 ppm was combined in the same manner as in Example 1, and an apparatus for generating, adding and decomposing ozone was used. did. Ozone generator [Nippon Special Ceramics Co., Ltd. OU-
65A, ozone decomposition catalyst: SCH-120 of Sakai Chemical Industry Co., Ltd.] and equipment for adding water at a rate of 4 L / H and calcium carbonate 3 kg
The following effects were obtained as a result of using the neutralization device using [Shiraishi Industry Co., Ltd.].

[0026]

[Table 6]

[0027]

Since the present invention is constructed as described above, the temperature of the exhaust gas is lowered by the water spray, so SOx and NOx contained in the exhaust gas are easily trapped,
Neutralization reaction can be performed reliably, and odor components can be decomposed by addition of ozone, and exhaust gas can be deodorized.Therefore, the cause of acid rain, corrosion on concrete and other structures, and photochemical smog can be ensured. Removed and extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a configuration diagram in which the present invention is partially improved.

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of the present invention having a deodorizer.

FIG. 5 is a schematic sectional view of an apparatus for carrying out the present invention.

Claims (2)

[Claims] 1. An exhaust gas outlet for an internal combustion engine that uses city gas or liquefied petroleum gas as a fuel is provided with a water addition unit for lowering the temperature of the exhaust gas to lower the exhaust gas to a predetermined temperature.
The exhaust gas, which has become low in temperature, continues to be sent to a neutralizer containing solid alkali, and SOx and NO adsorbed and absorbed in water.
x An exhaust gas treatment method for an internal combustion engine, characterized by neutralizing and removing other harmful components. 2. In an exhaust gas treatment device for an internal combustion engine using city gas or liquefied petroleum gas as a fuel, an exhaust gas temperature lowering water addition section and a neutralizer containing solid alkali are sequentially arranged in an exhaust gas passage. An exhaust gas treatment device for an internal combustion engine, comprising: