JPH031051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a gas-liquid contact method using a gas phase as a continuous phase. More specifically, the present invention includes:
This invention relates to a gas-liquid contact method that can be used particularly advantageously when carrying out a wet desulfurization method that uses a continuous gas phase to remove sulfur oxides by bringing combustion exhaust gas containing sulfur oxides into contact with an absorbent liquid. It is.

[Background of the Invention] A gas-liquid contact method that uses a gas phase as a continuous phase, which involves bringing a gas into contact with a liquid sprayed from a spray device while moving the gas within a reaction tower, is used to perform various chemical reactions. It is also used to remove specific components from gas. Among these, the removal of specific components in gas involves purification of raw material gas (e.g., removal of CO ₂ , H ₂ S, organic sulfur compounds, etc. from synthesis gas; CO ₂ , H ₂ S, organic sulfur compounds, etc. from natural gas). Gas-liquid contact methods that use the gas phase as a continuous phase are common for purposes such as removal of active components in exhaust gas (e.g., removal of gases such as SO ₂ , NO ₂ It is used for.

For example, if we take the flue gas generated from combustion equipment such as boilers that use oil-based fuel or coal-based fuel, there is a fairly high concentration of sulfur oxides (SOx) in the flue gas, so it is necessary to recover or Various methods have been proposed for removal, some of which are already in use.

Typical examples include a method in which sulfur oxides are recovered as gypsum using milk of lime, and a method in which sulfur oxides are absorbed and neutralized with a sodium hydroxide solution and then discharged.

Wet desulfurization methods using magnesium compounds have also been studied, and various methods have already been proposed. Most of these methods utilize magnesium sulfite (MgSO ₃ ) obtained by reacting an aqueous magnesium hydroxide solution with sulfur dioxide as a sulfur dioxide absorbing compound. This sulfur dioxide absorption operation is carried out, for example, in a gas-liquid contact device by moving exhaust gas containing sulfur oxides such as sulfur dioxide and bringing it into contact with the absorption liquid sprayed from a spray device. By selectively absorbing sulfur oxides such as sulfur,
This is done by removing them.

The reactions involved in the above operations can be represented by the equation below.

MgSO ₃ + SO ₂ + H ₂ O→Mg(HSO ₃ ) ₂ () Mg(HSO ₃ ) ₂ + Mg(OH) ₂ →2MgSO ₃ +2H ₂ O () In other words, sulfur dioxide is absorbed into magnesium sulfite and Mg(HSO ₃ ) ₂ , then the Mg
A circulation reaction is used in which (HSO ₃ ) ₂ is returned to magnesium sulfite by contacting newly supplied magnesium hydroxide. Note that since the combustion exhaust gas also contains oxygen, a part of the magnesium sulfite is oxidized by the oxygen to become magnesium sulfate, which coexists in the circulating reaction liquid.

During this circulation system, a portion of each of magnesium sulfite and magnesium sulfate (approximately the same amount in magnesium terms as newly supplied magnesium hydroxide) is extracted from the circulation system and subjected to an oxidation reaction. . Through this oxidation reaction, magnesium sulfite is converted to harmless magnesium sulfate and discharged. Alternatively, a method has been proposed in which sulfur oxides are recovered as gypsum using lime or the like from extracted magnesium sulfite and magnesium sulfate.

Conventionally, the gas-liquid contact device used in the above-mentioned gas-liquid contact method is a device in which spray devices are installed in one or multiple stages in one contact tower. Contact was to be achieved.

[Structure of the Invention] An object of the present invention is to provide an improved method of gas-liquid contact, which involves bringing a gas into contact with a liquid sprayed from a spray device while moving the gas.

In particular, it is an object of the present invention to provide a gas-liquid contact method that can be advantageously used in a wet removal method that allows specific components in gas to be removed with high efficiency while preventing absorption liquid mist from being discharged. shall be.

In addition, the present invention is particularly applicable to the implementation of a wet desulfurization method in which sulfur oxides are removed by bringing combustion exhaust gas containing sulfur oxides into contact with a liquid such as an aqueous solution or an aqueous dispersion that absorbs sulfur oxides.
Another objective of the present invention is to provide a gas-liquid contact method suitable for a desulfurization method that makes it possible to remove sulfur oxides with high efficiency while preventing the emission of absorption liquid mist.
That purpose.

The present invention provides a gas-liquid contact method that involves bringing the gas into contact with a liquid sprayed from a spray device while moving the gas. The gas-liquid contact speed (gas linear velocity) between the liquid and gas sprayed from the spray device that contacts the
The method is characterized in that the gas-liquid contact velocity (gas linear velocity) between the liquid and gas sprayed from the subsequent spray device is at least twice as high.

In particular, the above-mentioned gas-liquid contact method of the present invention brings the gas into contact with the liquid sprayed from the spray device while moving the gas, thereby removing the gas components that are selectively absorbed or adsorbed by the liquid into the liquid. It can be advantageously used in a wet removal method of a specific component in a gas, which involves absorption or adsorption of a specific component in a gas.

Further, in the gas-liquid contact method of the present invention, the gas is a combustion exhaust gas containing sulfur oxides, and the liquid sprayed from the spray device is a sulfur oxide-absorbing aqueous solution or an aqueous dispersion (for example, an aqueous solution containing magnesium sulfite). or an aqueous dispersion, or aqueous ammonia), and can be particularly advantageously used in a desulfurization method in which sulfur oxides are removed by contact with the liquid.

Next, we will explain the gas-liquid contact method of the present invention by using a desulfurization method in which sulfur oxides are removed from combustion exhaust gas using an aqueous solution or dispersion containing magnesium sulfite as an example. This will be explained in more detail with reference to an example.

FIG. 1 is a schematic diagram showing a system of a wet desulfurization apparatus that can be used to carry out a wet desulfurization method that is one embodiment of the present invention. This equipment is equipped with a pre-desulfurization section equipped with a pre-spray device, and the diameter of the pre-desulfurization section is changed to increase the gas linear velocity in the pre-desulfurization section. The wet desulfurization method of the present invention will not be described in any way because it is not essentially different from the desulfurization equipment used in conventional wet desulfurization methods that remove sulfur oxides by contacting them with an aqueous solution or dispersion containing sulfur oxides. Describe as much as necessary.

The wet desulfurization apparatus shown in FIG. 1 consists of a preliminary desulfurization section 11 and a desulfurization section 12. Combustion exhaust gas sent from a boiler or the like is introduced from the top of the preliminary desulfurization section 11, where it first comes into contact with the absorption liquid sprayed from the spray device 16, and is subjected to dust removal cooling treatment and preliminary desulfurization treatment. The contact speed (linear gas velocity) of the gas with respect to the absorption liquid sprayed from this spray device 16 is much higher than the linear gas velocity of 1 to 4 m/sec used in a normal gas-liquid contact system. The gas linear velocity is set to, for example, about 8 to 15 m/sec.

The combustion exhaust gas subjected to the above preliminary desulfurization treatment is then introduced into the desulfurization section 12, where it is further desulfurized and discharged from the top.

A spray device 13 is disposed above the desulfurization section 12. An absorption liquid (an aqueous solution or an aqueous dispersion containing magnesium sulfite) is sprayed from the spray device 13 and comes into contact with the pre-desulfurized combustion exhaust gas at a gas linear velocity of about 1 to 4 m/sec. Through this contact, most of the remaining sulfur oxides in the combustion exhaust gas are absorbed into the absorption liquid. The combustion exhaust gas subjected to this absorption treatment is then discharged to the outside.

The above-mentioned absorption liquid is collected in a liquid reservoir 14 provided at the lower part of the desulfurization section 12, and is temporarily stored there. Next, the recovered liquid in the liquid reservoir 14 is transferred to the circulation pump 15.
is returned to the spray device 13, 16 by
Used repeatedly to absorb sulfur oxides. Incidentally, magnesium hydroxide (or oxide) is added to the recycled recovered liquid during the circulation, thereby reinforcing the sulfur oxide absorption capacity.

Further, a part of the recovered liquid is taken out to the outside, subjected to necessary oxidation treatment, etc., and then discharged by means such as discharge. The concentration of the magnesium compound in the recovered liquid is detected by a concentration detection device 17 attached to the circulation system, and if necessary, industrial water is supplied to the industrial water replenishment spray 18 installed above the spray device 13 of the desulfurization section 12. The collected liquid is replenished via the

As described above, in the present invention, in addition to the normal desulfurization section 12, the spray device 16 for the sulfur oxide absorption liquid is disposed at a position in front of the gas movement path in the serial direction (preliminary desulfurization section 11). , the contact speed (gas linear velocity) between the absorption liquid sprayed from this spray device 16 and the gas is the contact speed (gas linear velocity) between the absorption liquid sprayed from the absorption liquid spray device 13 of the subsequent desulfurization section 12 and the gas. The desulfurization operation is characterized by performing the desulfurization operation at a rate of at least twice, preferably at least four times, the speed. The spraying operation of the absorption liquid in this preliminary desulfurization section not only performs preliminary desulfurization from the combustion exhaust gas, but also performs the function of removing dust from the combustion exhaust gas and cooling it.

In the above, a desulfurization method using an aqueous solution or aqueous dispersion containing magnesium sulfite from combustion exhaust gas has been explained, but similar desulfurization can be performed using, for example, ammonia water, sodium hydroxide aqueous solution, milk of lime, etc. It is also possible. Further, the specific component to be absorbed or adsorbed is not limited to sulfur oxides, and, for example, halogenated compounds in combustion exhaust gas can be used as the specific component to be absorbed or adsorbed. That is, a method of removing a specific component in a gas by absorbing or adsorbing the component into the liquid using contact in the gas phase with a liquid (water, aqueous solution, aqueous dispersion) that selectively absorbs or adsorbs the component. If so, the present invention can be used in either method.

Furthermore, since the effects of the present invention are due to the contact efficiency between gas and liquid, it is not only possible to remove specific components from the gas, but also to spray from a spray device while moving the gas within the reaction tower. ) The present invention can also be advantageously used to carry out various chemical reactions using a gas-liquid contact method in which a gas phase is made into a continuous phase by bringing a gas into contact with a liquid to be treated.

[Effects of the Invention] According to the present invention, when carrying out a gas-liquid contact method using a gas phase as a continuous phase, a separate spray device is placed in front of a normal liquid spray device, and the gas linear velocity at the front position is adjusted. By performing gas-liquid contact in a combination such that the gas linear velocity is at least twice the gas linear velocity at the rear position, highly efficient gas-liquid contact can be achieved in the entire gas-liquid contact system.

In particular, in accordance with the present invention, in absorbing (or adsorbing) removing specific components in a gas, at a position in front of a conventional absorption (or adsorption) liquid spray device,
A method of arranging a spray device that sprays an absorption (or adsorption) liquid and absorbing (or adsorbing) specific components in a combination such that the gas linear velocity at the front position is more than twice the gas linear velocity at the rear position. By using this method, specific components in the gas can be absorbed (or adsorbed) and removed with high efficiency while preventing the mist of the absorption (or adsorption) liquid from being discharged along with the treated gas. becomes possible.

For example, the method of the present invention may be used to increase the gas linear velocity in a spray device that contacts the gas first by 8.
~15 m/sec, and when specific components are removed from the gas under conditions such that the gas linear velocity in the subsequent spray device is 1 to 40 m/sec, the gas linear velocity is only about 1 to 4 m/sec, which is the conventional rate. It has been confirmed that the absorption performance is approximately 5 to 20 times higher than when using

Furthermore, in the method of the present invention, particularly highly efficient gas-liquid contact is achieved in the vicinity of the spray device installed in the front position, so it can be used when absorbing highly corrosive gases (for example, desulfurization operations in gas). In this method, highly corrosion-resistant materials are used only for the reaction system around the spray equipment in the front position, and ordinary materials can be used for the ordinary spray equipment in the latter stage, which is extremely useful in the construction of actual equipment. advantageous to

Next, in order to explain the present invention, Examples and Comparative Examples will be shown taking desulfurization treatment of exhaust gas as an example.

Example 1 The following desulfurization test was conducted using a wet desulfurization apparatus (combustion exhaust gas treatment capacity: 1000Nm ³ /hour) having the configuration shown in FIG.

Combustion exhaust gas: Exhaust gas from a furnace using petocoke as fuel, temperature 180-210℃, sulfur dioxide concentration
650ppm, oxygen content 14-17% by volume.

Preliminary desulfurization section absorption liquid spray: A hollow cone type spray nozzle 16 was installed upward in the preliminary desulfurization section (pipe diameter: 200 mm) 11, and the absorption liquid (circulated recovery liquid) was sprayed.

Liquid/gas ratio: 1.0 (/Nm ³ ) Gas flow rate: 1104Nm ³ /hour Gas linear velocity: 9.8 m/sec Desulfurization section absorption liquid spray: A hollow cone type spray nozzle 13 is installed in the desulfurization section 12 (pipe diameter: 500 mm). Install it facing downwards,
Absorption liquid (circulated recovery liquid) was sprayed.

Liquid/gas ratio: 1.0 (/Nm ³ ) Gas flow rate: 1104Nm ³ /hour Gas linear velocity: 1.6 m/s Adjustment of PH and density of absorption liquid (recovery liquid): Drainage volume, industrial water supply amount, magnesium hydroxide supply The amount was adjusted and maintained constant by automatically adjusting the amount.

Absorption liquid composition: Density 1100Kg/m ³ PH5.7 In this test, in order to examine the performance of the absorption tower, the capacity coefficient (K) was calculated according to the following formula.

K=Gm/Z・π×N However, [K=capacity coefficient (Kg-mol/m ³・hr・atm) Z=absorption section height (m) Gm=gas molar flow rate (Kg-mol/m ³・hr ) π = Gas pressure (atm) N = Total number of transfer units based on gas phase (-)] The capacity coefficient (K) of the preliminary desulfurization section in this Example 1 is 576 (Kg-mol/m ³ hr atm). It was hot.

Comparative Example 1 A desulfurization test was conducted in the same manner as in Example 1, except that an apparatus was used in which the gas linear velocity in the preliminary desulfurization section was the same as the gas linear velocity (1.5 m/sec) in the desulfurization section.

The capacity coefficient (K) of the preliminary desulfurization section in Comparative Example 1 was 77 (Kg-mol/m ³ ·hr·atm), which was about 1/7.5 of that in Example 1.

Example 2 A desulfurization test similar to Example 1 was conducted using aqueous ammonia (concentration: 25% by weight) as the absorption liquid. However, the gas to be desulfurized is acid gas combustion furnace exhaust gas (SO ₂ concentration: 66971 ppm, SO ₃ concentration:
1367ppm) and the inlet gas flow rate to 18650N.
m ³ /hour.

The capacity coefficient (K) of the preliminary desulfurization section in this Example 2 was 517 (Kg-mol/m ³ ·hr·atm).

Comparative Example 2 A desulfurization test was conducted in the same manner as in Example 2, except that an apparatus was used in which the gas linear velocity in the preliminary desulfurization section was the same as the gas linear velocity (1.7 m/sec) in the desulfurization section.

The capacity coefficient (K) of the preliminary desulfurization section in Comparative Example 2 was 63 (Kg-mol/m ³ ·hr·atm), which was about 1/8.2 of that in Example 2.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating a system of an example of an apparatus that can be used to carry out the wet removal method of a specific component in a gas of the present invention. 11: Preliminary desulfurization section, 12: Desulfurization section, 13: Spray device, 14: Liquid reservoir, 15: Circulation pump, 1
6: Spray device, 17: Concentration detection device, 18:
Industrial water refill spray.

Claims (1)

[Claims] 1. A gas-liquid contact method that involves bringing the gas into contact with a liquid sprayed from a spray device while moving the gas, wherein at least two spray devices are installed in series in a gas movement path, Of these, the gas-liquid contact velocity (gas linear velocity) between the liquid sprayed from the spray device that comes into contact with the gas first and the gas is calculated as the gas-liquid contact velocity (gas linear velocity) between the liquid and gas sprayed from the subsequent spray device. A method characterized by increasing the speed by more than twice the speed (speed). 2. The gas-liquid contact method according to claim 1, characterized in that the gas linear velocity in the spray device that contacts the gas first is four times or more the gas linear velocity in the subsequent spray device. 3 The gas linear velocity in the spray device that comes into contact with the gas first is 8 to 15 m/sec, and the gas linear velocity in the subsequent spray device is 1 to 4 m/sec. The gas-liquid contact method according to item 2. 4. The gas-liquid contact method involves moving a gas and bringing it into contact with a liquid sprayed from a spray device, thereby absorbing or adsorbing gas components selectively into the liquid, thereby forming a gas. 2. The gas-liquid contact method according to claim 1, which is a method for wet removal of a specific component in the liquid. 5. The gas is a combustion exhaust gas containing sulfur oxides, the liquid sprayed from the spray device is a sulfur oxide-absorbing aqueous solution or aqueous dispersion, and the sulfur oxides are removed by contact with the liquid. A gas-liquid contact method according to claim 4, characterized in that: 6. The gas is a combustion exhaust gas containing sulfur oxides, the liquid sprayed from the spray device is an aqueous solution or aqueous dispersion containing magnesium sulfite, and the sulfur oxides are removed by contact with the liquid. A gas-liquid contact method according to claim 4, characterized in that: