JP2000290668A - Purification of gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas purifying method capable of completely treating the whole amount of recovered ammonia in a gas purification facility without discharging excess gas to the outside of the system, in a gas purifying method for carrying out wet removing treatment of impurities containing a sulfur compound and ammonia in gasified gas. SOLUTION: Ammonia C6 recovered from a cleaning solution is distributed and poured to gas inlet side and gas outlet side of a combustion furnace 41 of a regenerated gas H1 and further, as necessary, an oxygen-containing gas J1 for combustion is poured to the gas inlet side and the ammonia is burned together with a sulfur compound in the combustion furnace to carry out oxidative decomposition of ammonia and a discharge gas H2 into which the ammonia is poured on the gas outlet side of the combustion furnace is introduced into an ammonia catalytic reduction type NOx removal equipment 42 in high temperature state to carry out denitration treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a product gas such as a coal gasification process, and more particularly, to a gas purification method for wet-removing impurities including sulfur compounds and ammonia in a product gas. The present invention relates to a gas purification method that completely removes and recovers ammonia in a gas purification facility and does not generate excess ammonia.

[0002]

2. Description of the Related Art In recent years, fuel resources have been depleted and soaring prices have led to a demand for diversification of fuels. Coal and heavy oil utilization technologies have been developed. One of them is coal and heavy oil. The technology of gasifying methane into a power generation fuel or a synthetic raw material has attracted attention. In addition, power generation using gasified gas is more efficient than conventional thermal power generation using coal or oil, and thus has attracted attention in terms of effective use of limited resources. However, this gasification product gas contains several hundreds to several thousand ppm of sulfur compounds (hydrogen sulfide and the like), which are used to prevent pollution or to prevent corrosion of downstream equipment (such as gas turbines). Need to be removed. As a removal method, for example, a wet gas purification method in which a gas is brought into gas-liquid contact with an absorbing solution as disclosed in Japanese Patent Application Laid-Open No. 7-48584 is known.

[0003]

However, in the conventional gas purification method, hydrogen chloride (HC)
No particular consideration is given to impurities such as 1) and ammonia (NH ₃ ), and improvements have been desired. That is, generally, for example, 100
About 1500 ppm of ammonia and, for example, 100 p
Since about pm of hydrogen chloride is contained, it is necessary to remove them for further cleaning.

[0004] Of these, hydrogen chloride is a strong acid and corrosive to stainless steel, and it is necessary to remove it as much as possible on the upstream side from the viewpoint of protecting equipment materials. In order to reduce the amount of chlorine compounds discharged into the atmosphere in the form of smoke contained in flue gas burned by a turbine or the like, it is necessary to remove them. Also,
Ammonia is generally hardly removed by gas-liquid contact treatment in a desulfurization tower using an absorption liquid (alkali) composed of an amine compound, and is burnt in a gas turbine or the like to become harmful nitrogen oxides, and is downstream of a gas turbine or the like. This is problematic because it increases the load on a denitration apparatus generally provided in the conventional art.

[0005] As a method for removing these impurities, a method is employed in which the produced gas is brought into gas-liquid contact with the cleaning liquid in a cleaning tower separate from the desulfurization tower to perform cleaning, and these harmful substances are dissolved in the cleaning liquid to absorb and remove them. Can be considered. However, in this case, in order to prevent the accumulation of the impurities, it is necessary to drain a part of the cleaning liquid, and the subsequent processing becomes a problem. That is, since the wastewater from the washing tower contains trace amounts of various harmful substances such as heavy metals, hydrogen sulfide, and carbonyl sulfide (COS) in addition to hydrogen chloride and ammonia, the wastewater is discharged by a conventional general wastewater treatment. Since the method requires a large equipment cost, improvement in this respect has been desired.

Accordingly, the applicant has filed Japanese Patent Application No. 9-169545.
And Japanese Patent Application No. 10-164429 propose a method of treating wastewater from the washing tower without discharging it. This involves extracting a part of the washing solution in the washing tower and adjusting the pH to near neutrality,
A part of the cleaning liquid having undergone the H adjustment step is evaporated in an evaporator, and the evaporative gas discharged from the evaporator is condensed to recover ammonia in the produced gas as ammonia water or an ammonia-containing gas (off-gas). ,
An evaporating step of discharging impurities in the product gas remaining in the evaporator as solids. In this method, the recovered ammonia (aqueous ammonia or ammonia-containing gas) is supplied to a sulfur dioxide gas absorption tower in an appropriate amount in order to improve the sulfur dioxide gas absorption rate, or the ammonia is supplied to the downstream of the gas turbine or the combustion furnace of the regeneration gas. For the denitration treatment of the nitrogen oxides originally present in the flue gas in the stream, the necessary amount required for the denitration treatment is appropriately supplied or reused.

However, in an actual coal gasification power plant or the like, the amount of ammonia that can be supplied to a sulfurous acid gas absorption tower and reused as an absorption aid or reused for denitration treatment is removed from the generated gas. There is a problem that a small amount of ammonia having a low purity, which is less than the amount of ammonia collected and recovered, and which is difficult to sell as a product, is generated in a considerable amount. The applicant filed the above application (Japanese Patent Application No.
No. 4429) proposes returning excess ammonia that cannot be reused to the gasification furnace for treatment, but this method has caused a demand to treat all ammonia in a gas purification facility. There is a problem that can not respond to the case.

Accordingly, the present invention is a gas purification method for wet-removing impurities including sulfur compounds and ammonia in a gas produced by gasification, wherein the entire amount of removed and recovered ammonia can be completely treated in a gas purification facility. And a gas purification method that does not require the discharge of excess ammonia out of the system.

[0009]

According to a first aspect of the present invention, there is provided a gas purification method comprising the steps of bringing a produced gas obtained by gasification of a carbon-containing fuel into gas-liquid contact with a cleaning liquid, and After absorbing and removing impurities including ammonia, the product gas is brought into gas-liquid contact with a sulfur compound absorbing solution to absorb and remove the sulfur compound contained in the product gas, while the sulfur compound is absorbed in the absorbing solution. Regeneration by applying heat, the regeneration gas containing sulfur compounds generated in this regeneration is burned in a combustion furnace to convert it into exhaust gas containing sulfur oxides, and further, an exhaust gas purification process for removing sulfur oxides in the exhaust gas In the gas purification method, the ammonia recovered from the cleaning liquid is distributed and injected into a gas inlet side and a gas outlet side of the combustion furnace, and further into the gas inlet side of the combustion furnace. If necessary, an oxygen-containing gas for combustion is also injected, and the ammonia injected into the gas inlet side of the combustion furnace is burned and oxidatively decomposed together with the sulfur compound in the combustion furnace, and the gas outlet side of the combustion furnace. In the exhaust gas into which the ammonia is injected,
Before the exhaust gas purification treatment, to be introduced into an ammonia catalytic reduction type denitration device while being in a high temperature state so as to perform denitration treatment,
Distributing and injecting amounts of the ammonia into the gas inlet side and the gas outlet side of the combustion furnace are set such that the ammonia concentration and the nitrogen oxide concentration in the exhaust gas after the exhaust gas purification process are within an allowable range. And

The gas purification method according to claim 2, wherein the ammonia concentration in the exhaust gas after the denitration treatment is equal to or higher than the reaction equivalent to the sulfur trioxide concentration in the exhaust gas after the denitration treatment. The distribution injection amount of the ammonia to the gas inlet side and the gas outlet side of the furnace is set.

Further, in the gas refining method according to a third aspect of the present invention, the product gas obtained by gasification of the carbon-containing fuel is brought into gas-liquid contact with a cleaning liquid to absorb and remove impurities including ammonia in the product gas. While the produced gas is brought into gas-liquid contact with an absorbing solution of a sulfur compound to absorb and remove the sulfur compound contained in the produced gas, heat is applied to the absorbing solution having absorbed the sulfur compound to regenerate the gas, and the generated gas is generated in the regeneration. In a gas purification method in which a regeneration gas containing a sulfur compound to be burned is converted into exhaust gas containing sulfur oxides by burning in a combustion furnace, and further, an exhaust gas purification treatment for removing sulfur oxides in the exhaust gas is performed. A heat exchanger that heats and discharges gas with heat, and a heated gas that is loaded with an ammonia decomposition catalyst that decomposes ammonia into nitrogen and nitrogen oxides and is discharged from the heat exchanger And the ammonia decomposition apparatus to be introduced,
A denitration apparatus in which a catalyst for ammonia catalytic reduction type denitration is loaded and gas discharged from the ammonia decomposition apparatus is introduced in a high-temperature state; and a denitration apparatus separate from a first gas line through which the regeneration gas and the exhaust gas flow. 2 installed on the gas line, the ammonia recovered from the cleaning solution is distributed and injected into the gas inlet side of the heat exchanger and the gas outlet side of the ammonia decomposer on the second gas line, If necessary, an oxygen-containing gas for combustion is also injected into the gas inlet side of the heat exchanger, and the ammonia injected into the gas inlet side of the heat exchanger is burned by the heat of the combustion furnace. The gas introduced into the decomposer and oxidatively decomposed, and the gas discharged from the ammonia decomposer and into which the ammonia was injected was introduced into the denitration device in a high temperature state. The denitration treatment is performed, and the ammonia concentration and the nitrogen oxide concentration in the gas after the denitration treatment are within an allowable range. It is characterized in that the distribution injection amount of ammonia is set.

Further, in the gas refining method according to claim 4, the ammonia is distributed and injected also to the gas outlet side of the combustion furnace in the first gas line, and the exhaust gas is provided to the gas outlet side of the combustion furnace. The distribution injection amount of the ammonia to the gas outlet side of the combustion furnace is set such that the ammonia concentration in the exhaust gas is equal to or higher than the reaction equivalent to the sulfur trioxide concentration in the exhaust gas.

According to a fifth aspect of the present invention, in the gas refining method, a regenerative heat exchange combustion furnace is used as the combustion furnace, and nitrogen (N ₂ ) in the gas introduced into the combustion furnace is oxidized. The regeneration gas is burned in a low temperature range where oxides are not generated.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (First Example) FIG. 1 is a view mainly showing a configuration of a gas cleaning section and a desulfurization section in an apparatus for carrying out an example of a gas purification method of the present invention, and FIG. FIG. 3 is a diagram showing a configuration of a cleaning liquid drainage processing unit in the same apparatus, and FIGS. 4 and 5 illustrate a combustion furnace for burning a regeneration gas. FIG.

First, the configuration and operation of the gas cleaning section and desulfurization section will be described with reference to FIG. In a gasification furnace not shown, for example, coal is gasified using air as a gasifying agent, and a product gas mainly composed of carbon monoxide and hydrogen is generated. As described above, the generated gas using coal as a raw material and air as a gasifying agent usually contains about 1000 to 1500 ppm of hydrogen sulfide (sulfur compound) and 1000 to 1500 p.
It contains about pm of ammonia and about 100 ppm of hydrogen chloride. Immediately after the furnace outlet, the generated gas A1 is usually at 1000 ° C. to 2000 ° C., but is usually recovered by a steam heater (not shown) provided at the furnace outlet side and cooled to, for example, about 350 ° C. Is, for example, about 26 ata.

The produced gas is first introduced into a dust removing means (not shown) composed of a cyclone, a porous filter or the like to separate and remove dust, and then introduced into the heat exchanger 4 as a produced gas A1. In this heat exchanger 4, gas A1
The purified gas A4 is heated by the heat of
Is deprived of heat and cooled, and in this case, is led out as gas A2. Note that, for example, a downstream side of the heat exchanger 4 may be provided with a converter loaded with a catalyst for converting carbonyl sulfide slightly contained in the product gas into hydrogen sulfide.
When installing the converter, a heat exchanger is also provided downstream of the converter to optimize the temperature of the converter, and the converter is purified by the heat of the product gas derived from the converter. A configuration in which the subsequent gas A4 is heated before the heat exchanger 4 may be employed.

Next, the generated gas A is provided downstream of the heat exchanger 4.
Before introducing 2 into a desulfurization tower 21 to be described later, a washing tower 7 for bringing the cleaning liquid B into gas-liquid contact is provided. In this case, the washing tower 7 is a so-called packed gas-liquid contact tower, in which a washing liquid B mainly containing water stored at the bottom of the tower is sucked up by a circulation pump 8 and injected from a spray pipe 9 at the top of the tower. Then, the gas A2 flows down through the filler 10 while being in gas-liquid contact with the gas A2, and returns to the bottom of the column and circulates again.
In this case, the washing tower 7 is of a so-called counter-current type, in which gas A2 introduced from the lower part of the tower rises in the tower in opposition to the washing liquid B flowing down, and is chlorinated by gas-liquid contact with the washing liquid B. After removing impurities such as hydrogen and ammonia, the gas is discharged from the tower top as gas A3 after washing.

In this case, a part of the cleaning liquid B is withdrawn from the discharge side of the circulation pump 8 through a flow path.
The wastewater is discharged as wastewater C. Further, to any one of the circulation paths of the cleaning liquid B, a sufficient amount of make-up water D can be supplied as waste water C or in a gas to compensate for the amount carried away. Also, at the top of the washing tower 7,
Mist eliminator 11 for separating and removing mist in gas
Is provided, so that the amount of so-called accompanying mist flowing out to the downstream side is suppressed to a low level. And the washing tower 7
A desulfurization tower 21 is provided downstream of the gas, and hydrogen sulfide, which accounts for most of the sulfur compounds in the produced gas, is supplied to the gas A3 after cleaning.
The absorption liquid that has absorbed the hydrogen sulfide is successively regenerated in the regenerator 22 and recycled.

The desulfurization tower 21 is a gas-liquid contact tower similar to the washing tower 7 described above, and a hydrogen sulfide absorption liquid F (usually an amine absorption liquid) stored at the bottom of the regeneration tower 22 is circulated by a circulation pump. After being sucked up by 23 and cooled by the absorption liquid heat exchanger 24, it is injected from the spray pipe 25 at the top of the tower, and flows down through the filler 26 while being in gas-liquid contact with the gas A3. I have. The gas A3 from which hydrogen sulfide has been removed by gas-liquid contact with the absorbing solution F is supplied to the mist eliminator 27.
After the entrained mist is removed, the gas A4 is discharged from the top of the desulfurization tower 21 as a gas A4, and is heated by the heat exchanger 4 to become a purified product gas A5. The pressure of the product gas A5 after purification is, for example, about 25.5 ata, the temperature is about 300 ° C., and the sulfur concentration is 10 ppm or less.

On the other hand, in the regeneration tower 22, after the absorption liquid F stored in the bottom of the desulfurization tower 21 is sucked up by the circulation pump 28 and heated by the absorption liquid heat exchanger 24, the spray pipe at the top of the tower The filler 3 is injected from the fuel tank 29 and comes into contact with the vapor or absorbing component (off gas) of the absorbing liquid F rising in the tower.
It flows down through 0. This regeneration tower 2
The absorption liquid F at the bottom of the second column is heated by the steam G in the reboiler 31, whereby hydrogen sulfide as an absorption component is released to the gas side in the regeneration tower 22. After the mist is removed in the mist eliminator 32, the off-gas (regeneration gas) containing hydrogen sulfide passes through a reflux section (not shown) provided at the top of the regeneration tower 22 and contains hydrogen sulfide at a higher concentration. Offgas H1
Is sent to a regenerated gas combustion section described later.

The product gas A5 after the product gas A1 has been purified by the present gas refining apparatus is sent to, for example, a gas turbine 12, where it is used as a turbine fuel for an integrated coal gasification combined cycle. ing. In addition,
In FIG. 1, what is indicated by reference numeral 13 is a gas turbine 12.
A denitration apparatus provided as necessary for decomposing nitrogen oxides in the exhaust gas A6 produced by burning the product gas A5.
3 is a waste heat boiler disposed before and after 3 for recovering heat from the exhaust gas A6 and generating or heating steam to be supplied to a steam turbine (not shown) for combined power generation.

Here, the denitration apparatus 13 performs a denitration treatment by decomposing nitrogen oxides by an ammonia catalytic reduction method using a titanium oxide-based catalyst containing, for example, vanadium, tungsten or molybdenum as an active component. Conventionally, in the denitration apparatus 13 or its upstream, an amount of ammonia corresponding to the denitration equivalent has been supplied from outside the system and injected into the flue gas. In this example, however, the ammonia water collected in the system is described later. C6 is supplied. For this reason, there is no need to purchase ammonia for the denitration treatment, and the operating cost can be reduced accordingly. The amount of ammonia corresponding to the denitration equivalent is theoretically an equimolar amount to nitrogen oxides, but in order to perform a sufficient denitration treatment, it is actually necessary to add a little excessive amount. .

Since the generated gas A5 contains almost no ammonia due to the absorption and removal in the washing tower 7, the nitrogen oxide (so-called fuel knock) generated by the combustion of the ammonia in the fuel in the gas turbine 12 is used. ), And the nitrogen oxides in the exhaust gas A6 are mostly nitrogen oxides (so-called thermal knock) generated by oxidation of nitrogen (N ₂ ) contained in the combustion air supplied to the gas turbine 12. . Therefore, in this example, the total amount of nitrogen oxides is smaller than before, and at least the capacity of the denitration device 13 can be reduced. Depending on the case where the generation of thermal knock is suppressed due to the improvement of the combustion state of the gas turbine 12 or the like, or the required nitrogen oxide emission concentration,
The denitration device 13 can be deleted. The reason why the denitration device 13 is sandwiched between the waste heat boilers 14 is to set the temperature of the exhaust gas in the denitration device 13 to a temperature suitable for the denitration process.

Next, the regeneration gas combustion section (ammonia processing section) and the exhaust gas purification processing section will be described with reference to FIG. The regenerative gas combustion section of the present example includes a combustion furnace 41 for introducing and burning off gas H1 (regeneration gas) together with air J1.
And a denitration device 42 into which exhaust gas H2 (combustion gas) discharged from the combustion furnace 41 is introduced. And here, the collected ammonia (ammonia water C6 described later,
Alternatively, the surplus of the off-gases C4 and C7 described later is supplied to the gas inlet side of the combustion furnace 41 and the gas outlet side of the combustion furnace 41 (that is, the gas outlet side).
(The gas inlet side of the denitration device 42). In order to inject the ammonia water C6, the ammonia water C6
A nozzle or the like for spraying and dispersing is required, but is not shown here. Further, the water constituting the ammonia water C6 injected into the gas evaporates instantaneously due to the heat of the gas itself and the combustion heat of the combustion furnace 41, so that the state of the gas after injection and the state of the gas after injection are as follows. Almost the same.

Here, the denitration apparatus 42 is similar to the above-described denitration apparatus 13, and is an apparatus for decomposing nitrogen oxides into nitrogen and water by an ammonia catalytic reduction method. In this case, as the combustion furnace 41, a regenerative heat exchange combustion furnace is used. That is, as shown in FIG. 4, the combustion furnace 41 is composed of a furnace main body 70 and its accompanying equipment and piping lines. Furnace body 70
Comprises a combustion chamber 71, and three heat exchange channels 73a, 73b, 73c which are connected to the combustion chamber 71 in a parallel state and each of which is loaded with a ceramic heat storage body 72.
A burner 74 is provided on the upper part of the unit 1. Here, the burner 74 is supplied with the auxiliary fuel N (for example, LPG) and the air J2 for burning the auxiliary fuel N at the time of starting, and the combustion chamber 71 only at the time of starting.
The auxiliary fuel N is burned in the inside. As the furnace main body 70, specifically, for example, a combustion furnace of an RTO regenerative deodorizer (model RI-3) manufactured by Chugai Furnace Industry Co., Ltd. can be used.

As ancillary equipment and piping lines, a mixer 81 for mixing the regeneration gas H1, the air J1, and ammonia (aqueous ammonia C6, etc.), and a processing gas P mixed by the mixer 81 are sent by a fan 82. An introduction line 83, a purge line 84 into which the purge gas Q is sent, and an exhaust line 85 for exhausting the exhaust gas H2 after combustion are provided. Further, the introduction line 83, the purge line 84, the exhaust line 85, and each heat exchange flow path 7
3a, 73b, 73c, open / close valves 91a-
91c, 92a to 92c and 93a to 93c are provided, respectively. In this case, the purge line 84 includes
A part of the exhaust gas H2 is sent by a fan (not shown), and a part of the exhaust gas H2 is used as a purge gas Q.

Each of the open / close valves 91a to 91c, 9
2a to 92c and 93a to 93c are controlled by a controller (not shown) according to a predetermined sequence or program, and operate so as to execute the operation as shown in FIG. In FIG. 5, among the open / close valves, the closed valve is shown in black and the open valve is shown in white. That is, in the combustion furnace 41, the operating states shown in FIGS. 5A, 5B, and 5C are changed by switching the operating states of the respective on-off valves.
For example, it is sequentially repeated at intervals of, for example, 60 to 70 seconds.
Then, only during the time from the start-up until the temperature in the combustion chamber 71 reaches the set temperature of 1000 ° C. and stabilizes, a mixed gas of LPG and air is blown from the burner 74 into the upper part of the combustion chamber 71, and the flame 74a is discharged. It is formed. Thereby, any one of the three heat storage bodies 72 is provided.
The operation of heating the processing gas P by contacting the pre-combustion processing gas P with another heat storage element 72 while heating the specific heat storage element 72 by contacting the exhaust gas H2
Are switched and the heat storage element 72 is eventually switched.
The processing gas P is continuously heated by the heat recovered from the flue gas H2 using the medium as a medium, and the combustion at about 1000 ° C. of the hydrogen sulfide and ammonia contained in the processing gas P can be continued in the combustion chamber 71.

To further explain, for example, a so-called heat-exchange combustion furnace having a simple heat exchanger for heating the processing gas by the heat of the combustion exhaust gas is considered, but the heat exchange material (tube, tube sheet, etc.) is the combustion exhaust gas. Since it is cooled by the processing gas while being heated, it requires a high-grade material that can withstand a large difference between a high temperature and a low temperature from about 1000 ° C. to room temperature, and there is no practical material. On the other hand, in a combustion furnace having such a heat storage type heat exchange function, heating and cooling (heat recovery) of the heat storage medium as the heat medium are performed independently, so that the heat storage medium as the heat medium is slightly cooled. In the temperature variation range of about 100 ° C. to 150 ° C., the temperature difference between the gas inlet (before heating) and the outlet (after heating) can be significantly increased to about 700 ° C.
For this reason, the thermal efficiency is remarkably increased, and in the steady state, combustion at an appropriate temperature of about 1000 ° C. can be continuously realized without supplying the auxiliary fuel N such as LPG and the air J2 therefor.

A line for extracting a part of the exhaust gas from the combustion chamber 71 and mixing it with the exhaust gas H2, and a waste heat boiler provided in the middle of this line for recovering heat from a part of the exhaust gas and heating the boiler feed water ( A heat exchanger) may be provided to effectively use excess heat energy and stably adjust the combustion temperature of the combustion chamber 71 to an optimum value.
That is, in a steady state in which the supply of the auxiliary fuel N is stopped, the combustion temperature in the combustion chamber 71 fluctuates due to fluctuations in the flow rate of the regenerating gas H1 if no operation is performed. Combustion temperature of at least 10
The temperature is set to 00 ° C., and when the temperature exceeds 1000 ° C., the amount of heat recovered by the waste heat boiler is increased by, for example, controlling the flow rate of flue gas, thereby heating the heat storage body. What is necessary is just to keep the temperature around 1000 ° C. by suppressing the increase in temperature. In this way, the condition of the combustion temperature of about 1000 ° C. can be stably maintained.

In the combustion in the combustion furnace 41, maintaining the combustion temperature at about 1000 ° C.
The temperature is maintained in a low temperature range in which so-called thermal knock is hardly generated, and most of the nitrogen oxides generated in the combustion and contained in the exhaust gas H2 are converted into nitrogen oxides generated by burning the injected ammonia. Become. On the other hand, maintaining the combustion temperature at about 1000 ° C.
This also maintains the high temperature range in which the generation of sulfur trioxide (SO ₃ ) due to the combustion of hydrogen sulfide is suppressed to an almost minimum amount. That is, according to the study of the inventors, the decrease in the amount of generated sulfur trioxide is leveled off as the combustion temperature is increased.
Above 00 ° C, there is almost no change. This tendency is the same regardless of changes in the concentration of hydrogen sulfide and the like.
Sulfur trioxide, if left as it is, combines with the ammonia slightly remaining in the gas to become scaled and highly corrosive acidic ammonium sulfate (NH ₄ HSO ₄ ), or the characteristic of sulfuric acid dew point. Accordingly, the sulfuric acid mist which is also highly corrosive and causes scale generation by the cooling of the heat exchanger 46 and the like which will be described later. Further, since the sulfuric acid mist formed by condensation of sulfur trioxide is usually submicron particles, it cannot be collected by a desulfurization device (reactor 43) described later, and is contained in exhaust gas H4 and released to the atmosphere. .

Therefore, in this example, in addition to the amount required for the denitration treatment in the denitration device 42, the sulfur trioxide in the combustion gas H2 is neutralized to harmlessly collect ammonium sulphate ((NH ₄ ) ₂ SO ₄ ). ) Is injected into the combustion gas H2, and the ammonia is, for example, aqueous ammonia C6 recovered in the system as shown in FIG. It is configured to be distributed and supplied. The ammonia may be injected into the gas in the denitration device 42. Further, in this case, since the ammonium sulfate generated in the gas is a relatively large particle, the absorption liquid K in a desulfurization apparatus (reactor 43) described later together with other impurities.
Most of them are collected in gypsum and treated by being contained, for example, in gypsum by-produced, but even in this case, the amount of ammonium sulfate is small compared to the gypsum content, so in most cases gypsum quality It doesn't matter.

Next, the exhaust gas purifying section includes a denitration device 42.
It consists of a desulfurization unit of the wet lime-gypsum method, which absorbs and removes sulfurous acid gas (SO ₂ ) from the exhaust gas H3 derived from the exhaust gas and discharges it as harmless exhaust gas H4, and produces gypsum as a by-product. The desulfurization apparatus includes a reactor 43 for discharging exhaust gas H3 containing a high concentration of sulfurous acid gas produced by burning hydrogen sulfide in gas-liquid contact with an absorbing solution K (slurry containing calcium compound) supplied therein, An air supply means (not shown) for blowing the oxidizing air L into the slurry in the reactor 43 as a number of fine bubbles, and a slurry M extracted from the reactor 43
A solid-liquid separation unit 44 such as a centrifuge for solid-liquid separation of the (gypsum slurry), and a solid content M1 (gypsum cake of gypsum dihydrate) obtained by the solid-liquid separation unit 44 are heated to 120 ° C to 150 ° C.
Gypsum heating device 45 such as a combustion furnace which is heated to a degree to form hemihydrate gypsum M2.

In FIG. 2, reference numeral 46 denotes a heat exchanger for recovering heat from the combustion gas H3 (for example, a heat recovery section of a gas gas heater). The exhaust gas H4 is heated by a heater (for example, a reheating unit of a gas gas heater) to a temperature suitable for atmospheric release. Separated water M3 generated by solid-liquid separation in the solid-liquid separation means 44 is directly returned to the reactor 43 in this case as water constituting the slurry in the reactor 43. Here, the reactor 43 specifically has, for example, a filling tank in which a slurry in the oxidizing air L is blown at the bottom of the tower and a slurry in the slurry tank is injected into the top of the tower through which the exhaust gas H3 flows. It can be constituted by a so-called absorption tower of a slurry circulation type having a gas-liquid contact portion such as a spray type or a liquid column type. Alternatively, the reactor 43 may be of a so-called bubbling type in which both the oxidizing air L and the exhaust gas H3 are blown into the slurry in the tank, and the absorption and oxidation of the sulfurous acid gas are all performed in the tank. In any case, in the reactor 43, a well-known reaction proceeds, and sulfur dioxide is absorbed to produce gypsum.

The absorption liquid K supplied to the reactor 43
Is a slurry tank in which a calcium compound such as limestone (CaCO ₃ ) is stirred and mixed with industrial water or the like or ammonia water C6 to be described later in a slurry tank not shown. It goes without saying that it may be supplied directly to the reactor 43 as it is. Further, the gypsum heating device 45 can be omitted, and the solid content M1 of gypsum dihydrate obtained by the solid-liquid separation means 44 can be used as a by-product as it is.

Further, the water constituting the slurry in the reactor 43 usually decreases if it is carried away by the exhaust gas H4 and the solid content M1 and left to stand, so that it is necessary to replenish the water. The water for this replenishment may be indirectly replenished, for example, as the water of the absorbent K, or may be directly supplied to the reactor 43. In this example, ammonia water C6 described later is used as a part or the whole of the makeup water. In the case of FIG. 2, the ammonia water C6 is directly supplied to the reactor 43. It has been found that when the concentration of ammonium ions in the absorbing solution K of the desulfurization apparatus increases due to the injection of ammonia in this way, the removal rate of sulfurous acid gas is significantly improved. However, excessive injection of ammonia deteriorates the quality of gypsum as a by-product, so it is necessary to inject gypsum within a range that can maintain the desired quality of gypsum.

Next, the cleaning liquid drainage processing section will be described with reference to FIG. Wastewater C discharged from the aforementioned washing tower 7
First, if necessary, a pH adjuster R made of an acid (for example, sulfuric acid) or an alkali (for example, sodium hydroxide) is added in a pH treatment tank 51, and the pH is adjusted to, for example, a neutral or weakly alkaline region. , And is introduced into the circulation system of the evaporator 53 by the pump 52 as the drainage C1. The evaporator 53 evaporates the wastewater C1 to separate it into a concentrated liquid C2 and a vapor C3 containing ammonia.
In this case, the concentrated liquid C2 in the liquid pool at the bottom is
4 and is heated by the heater 55 together with the newly introduced wastewater C1 and then jetted from the upper spray pipe 56. The heater 55 is
For example, the heat exchanger heats the circulating fluid to a temperature at which ammonia is diffused as a gas by high-temperature and high-pressure steam extracted from a part of a steam cycle in a power generation system. Then, the concentrated liquid C2 extracted from the circulation system of the evaporator 53
Is introduced into the evaporator 57 and is separated into off-gas C4 and sludge C5 by a further evaporating process. The evaporator 57 heats the concentrated liquid C2 introduced into the liquid reservoir at the bottom by a heating means such as an electric heater (not shown) and performs an evaporation process. In this case, the evaporator 57 is arranged so that the lower portion is immersed in the liquid reservoir. The drum 58 is configured to rotate in a state of being rotated, and the solid content in the liquid pool adhering to the peripheral surface of the drum 58 is continuously sent out and discharged as sludge C5.

The steam C3 containing ammonia led out from the top of the evaporator 53 is cooled to a condensing temperature by the cooler 59, and then introduced into the condensate tank 60, where condensed water containing ammonia (ie, ammonia Water C6) and off-gas C7. And the condensate tank 60
The ammonia water C6 collected at the bottom of the reactor is drawn out by the pump 61 and sent to the reactor 43 as described above as a liquid constituting the slurry of the reactor 43. Supplied to the upstream
It is configured to be used for the aforementioned denitration process. Also,
The remaining ammonia water C6 and the off-gases C4 and C7 are distributed and injected before and after the combustion furnace 41, as described above, and are oxidatively decomposed or used for the subsequent neutralization of sulfur trioxide.

Next, a description will be given of the main part of the gas purification method implemented in the gas purification apparatus configured as described above, and the operation and effect thereof. In this example, the ammonia collected as described above is effectively used in each part as ammonia water C6. That is, it is injected for the denitration treatment in the downstream of the gas turbine 12 and injected into the reactor 43 of the desulfurization device as a sulfur dioxide absorption aid, or the combustion furnace 41
Injected for neutralization of sulfur trioxide in the wake. However, since the generated gas generated by gasification of coal or the like usually contains ammonia in an amount exceeding such an effective use amount, surplus ammonia is necessarily generated. This uses a combustion furnace 41 having a specification that generates nitrogen oxides (thermal knock),
Denitration treatment is necessary downstream of the combustion furnace 41, and this is the case even when ammonia injection is required here. Also,
For example, off-gas C4, C7 containing a small amount of ammonia
Is used as a part of the air to be injected into the combustion furnace 41,
As a result, even if nitrogen oxides (fuel nox) are generated and the denitration load in the downstream of the combustion furnace 41 is slightly increased, the ammonia water C6 still cannot be effectively used.

Therefore, in this method, the remaining ammonia (in this case, ammonia water) is injected into the reactor 43 of the desulfurization device as a sulfur dioxide absorption aid, and then injected into the reactor 43 of the desulfurizer. All of C6 and off-gases C4 and C7) are distributed and injected to the inlet side and the outlet side of the combustion furnace 41 as shown in FIG. The distribution amount is adjusted, and the capacity of the denitration device 42 and the air J1 are adjusted.
The amount of ammonia and nitrogen oxide remaining in the final exhaust gas H3 or H4 is suppressed to an allowable range by setting the input amount to a sufficient amount. That is,
When ammonia is introduced into the combustion furnace 41 and burned, most of it becomes water and nitrogen, but a small amount of nitrogen oxide (fuel knock) is generated in accordance with the amount of injected ammonia, and the above-described regenerative heat is used. Even if a combustion furnace such as an exchange combustion furnace is used to maintain the combustion temperature at an appropriate temperature (about 1000 ° C.) to prevent the generation of nitrogen oxides (thermal nox), the denitration treatment in the downstream of the combustion furnace can be performed. Required (that is,
Ammonia injection is also required on the outlet side of the furnace according to the amount injected on the inlet side of the furnace.) However, if excessive ammonia is injected into the outlet of the combustion furnace for this denitration treatment, the concentration of ammonia remaining in the exhaust gases H3 and H4 after the denitration device 42 exceeds the allowable value. The preferred amount of ammonia to be determined ultimately can be almost uniquely determined according to the amount to be injected into the inlet side of the combustion furnace.
Thus, in the present method, an optimal distribution ratio is assumed in advance based on such a concept, and the remaining amount of ammonia is distributed to the inlet side and the outlet side of the combustion furnace 41.

In this embodiment, when determining the optimum distribution ratio, the neutralized amount of sulfur trioxide present in the exhaust gas H2 after the combustion furnace 41 is also taken into consideration. That is, the amount of ammonia in excess of the amount of ammonia required for the denitration treatment downstream of the combustion furnace by the neutralization amount of sulfur trioxide is supplied to the denitration device 42.
The above distribution ratio is set so as to be contained in the exhaust gas H2 at the inlet of. In addition, the following Table 1 shows an example (specific example in the case of coal gasification) of a change in concentration of gas components and a gas temperature condition in a gas line composed of the combustion furnace 41 and the denitration device 42. Is specifically described with reference to figures.

[0041]

[Table 1]

In the case of Table 1, all of the remaining ammonia water C6 and the like were mixed so that the ammonia concentration in the gas at the combustion furnace inlet became 30000 ppm and the ammonia concentration in the gas at the combustion furnace outlet became 340 ppm. It is distributed and injected into the inlet and outlet. And ammonia injected into the combustion furnace inlet side (in this case, 30000 ppm)
Is mostly decomposed into nitrogen and water by combustion, but a small amount is converted into nitrogen oxides, so that at the denitrator inlet (ie, the combustion furnace outlet), 240 ppm
Of nitrogen oxides are generated. Note that the equivalent of ammonia for decomposing this amount of nitrogen oxides (that is, for denitration treatment) is theoretically 240 ppm (equimolar). However, in this example, the neutralized amount of sulfur trioxide is intentionally left in excess, so that the ammonia concentration in the gas at the outlet of the combustion furnace including that amount is 340 ppm.
The distribution amount of the ammonia injection is set so that
That is, at the inlet of the denitration apparatus, the combustion of hydrogen sulfide causes 32
A large amount of sulfur dioxide gas of 000 ppm is generated, and a small amount of sulfur trioxide is generated as small as 50 ppm.
Then, to neutralize sulfur trioxide, stoichiometric 2
Twice the mole of ammonia is required, in this case 10
About 0 ppm is required. Therefore, the ammonia concentration at the combustion furnace outlet side is set to 340 (= 240 + 100) pp in this case.
m.

Thus, in the case of Table 1, the denitration device 42
In this method, a sufficient amount of ammonia for the denitration treatment is present in the gas, and the gas temperature is kept high after the combustion (in this case, 300 ° C.). (In this case, 230 ppm) effectively reacts with ammonia to form nitrogen and water by the catalytic action, and nitrogen oxides remaining in the exhaust gas H3, H4 after the denitration device 42 are within an allowable range of 10 ppm. In this case, the ammonia in the gas is reduced by the reaction with the nitrogen oxides, and becomes 110 ppm in the exhaust gas H3 on the outlet side of the denitration device 42. Then, after that, when the gas temperature decreases due to cooling of the heat exchanger 46 or contact with the absorbing solution in the reactor 43 (desulfurization device), the remaining ammonia reacts with sulfur trioxide in the gas to become ammonium sulfate.
The ammonia concentration in the final exhaust gas H4 (exhaust gas at the outlet of the desulfurization device) is 10 (= 1100-100) ppm.
Is also a low value within the allowable range. Further, most of sulfur trioxide is converted into ammonium sulfate by the reaction with ammonia to have a final concentration of almost zero, and sulfur dioxide gas becomes 13 ppm by absorption in a desulfurizer.

Therefore, according to the gas purification method of the present embodiment, all of the harmful substances (hydrogen sulfide, ammonia, nitrogen oxides, sulfur dioxide, sulfur trioxide) in the exhaust gas H4 released to the atmosphere are within the allowable range. This is a low value, and an excellent effect is obtained in which all of the remaining ammonia is internally treated in the gas purification device while a part of the recovered ammonia is effectively used. In addition, if there is another use of ammonia in another adjacent facility, etc., the remaining ammonia may be supplied to the facility and used effectively, but if there is no such use, the conventional method may be used. For example, there is no other choice but to decompose ammonia by a complicated treatment using microorganisms. However, if ammonia is distributed and injected before and after the combustion furnace as in this example, even if a large amount of ammonia remains, it can be easily treated internally.

(Second Example) Next, a second example of the present invention will be described with reference to FIG. The description of the same components as in the first example is omitted. In this example, as shown in FIG.
The regeneration gas combustion unit (ammonia treatment unit) is configured as follows. That is, a heat exchanger 61 that heats and discharges the processing gas S1 (a mixed gas of ammonia and air J1 described later) by the heat of the combustion furnace 41 and an ammonia decomposition catalyst that decomposes ammonia into nitrogen and nitrogen oxides are loaded. The ammonia decomposition device 62 into which the heated gas S2 discharged from the heat exchanger 61 is introduced and the gas S3 discharged from the ammonia decomposition device 62 loaded with a catalyst for ammonia catalytic reduction type denitration are kept in a high temperature state. The denitration device 63 to be introduced is provided as a second gas line T2 separate from the first gas line T1 through which the regeneration gas H1 and the exhaust gases H2 and H3 flow.

Here, from the viewpoint of reducing the denitration load, the ammonia decomposition catalyst loaded into the ammonia decomposition apparatus 62 is preferably one having a low nitrogen oxide generation amount (high nitrogen selectivity). JP-A-8-3885
No. 6 can be used. That is, a predetermined crystalline silicate as a carrier, platinum as an active metal,
One of palladium, ruthenium, and indium
Catalysts containing more than one species (nitrogen selectivity 70% or more) can be used. Further, as the heat exchanger 61, for example, as shown by a dashed line in FIG. 4, a heat transfer tube 61a disposed in a combustion chamber 71 of a combustion furnace main body 70, and air J1 and ammonia water C6 are provided in the heat transfer tube 61a. Mixer 6 for mixing and introducing
1b can be used.

In this example, ammonia containing all surplus is injected into the second gas line T2 as follows. That is, the recovered ammonia (ammonia water C6
Etc.) are distributed and injected into the gas inlet side of the heat exchanger 61 and the gas outlet side of the ammonia decomposing device 62 on the second gas line T2. Accordingly, the air J1 (oxygen-containing gas) for ammonia combustion is also injected, and the ammonia injected into the gas inlet side of the heat exchanger 61 is burned by the heat of the combustion furnace 41, and further introduced into the ammonia decomposition device 62 to oxidize. Decompose,
The gas S3 into which ammonia has been injected at the gas outlet side of the ammonia decomposition device 62 is introduced into the denitration device 63 in a high-temperature state so as to be subjected to the denitration process, and the ammonia concentration and the nitrogen oxides in the gas S4 after the denitration process are increased. The distribution injection amount of ammonia to the gas inlet side of the heat exchanger 61 and the gas outlet side of the ammonia decomposing device 62 is set so that the concentration falls within the allowable range.

Further, in this embodiment, part of the ammonia is also distributed and injected into the gas outlet side of the combustion furnace 41 in the first gas line T1, and the ammonia in the exhaust gas H2, H3 at the gas outlet side of the combustion furnace 41 is injected. The distribution amount of ammonia is set so that the concentration becomes equal to or higher than the reaction equivalent to the sulfur trioxide concentration in the exhaust gas. In addition, the following Table 2 shows an example of a gas component concentration change and a gas temperature condition in the second gas line T2 including the heat exchanger 61, the ammonia decomposition device 62, and the denitration device 63 (a specific example in the case of coal gasification).
This is for specifically explaining the above with numerical values.

[0049]

[Table 2]

In the case of Table 2, the ammonia concentration in the gas S1 on the inlet side of the heat exchanger 61 is 30,000 ppm, and the ammonia concentration in the gas S3 on the outlet side of the ammonia cracker 62 is 250 ppm. All of the remaining ammonia water C6 and the like are distributed and injected into the inlet side of the heat exchanger 61 and the outlet side of the ammonia decomposing device 62. Most of the ammonia (30,000 ppm in this case) injected into the inlet side of the heat exchanger 61 is decomposed into nitrogen and water by combustion and oxidative decomposition by the ammonia decomposer 62, but a small amount is oxidized by nitrogen. In this case, 250 ppm of nitrogen oxides are generated at the inlet of the denitration apparatus (that is, at the outlet of the ammonia decomposition apparatus). The equivalent of ammonia for decomposing this amount of nitrogen oxides (that is, for denitration treatment) is 25.
0 ppm (equimolar), and therefore, the distribution amount of the ammonia injection is set so that the ammonia concentration at the outlet side of the ammonia decomposition device 62 becomes 250 ppm.
If importance is attached to the denitration efficiency, the ammonia concentration may be increased with some margin. Further, although not shown in Table 2, since sulfur trioxide is present at about 50 ppm on the outlet side of the combustion furnace 41 in the first gas line T1, as described above, the first example (Table 1) Similarly, the amount of distribution of ammonia to the outlet side of the combustion furnace 41 is set such that the ammonia concentration at the outlet side of the combustion furnace is such that the sulfur trioxide can be neutralized (for example, 110 ppm).

By setting such a distribution amount, in the case of Table 2, in the denitration device 63, a necessary amount of ammonia for the denitration treatment is present in the gas, and the gas temperature remains high after combustion ( In this case, the temperature is set to 300 ° C., so that most of the nitrogen oxides in the gas (in this case, 240 p
pm) effectively reacts with ammonia by the catalytic action to form nitrogen and water, and the nitrogen oxides remaining in the exhaust gas S4 after the denitration device 63 are within an allowable range of 10 ppm.
Further, in this case, the ammonia in the gas S3 on the outlet side of the ammonia decomposition apparatus (the inlet side of the denitration apparatus) is reduced by that amount by the reaction with the nitrogen oxides, and becomes 10 ppm in the exhaust gas S4 on the outlet side of the denitration apparatus 63. , Again, a low value within the allowable range.

Therefore, even in the gas purification method of this embodiment, all of the harmful substances (hydrogen sulfide, ammonia, nitrogen oxides, sulfur dioxide, sulfur trioxide) in the exhaust gas H4 and S4 released to the atmosphere are within the allowable range. This is a low value, and an excellent effect is obtained in which all of the remaining ammonia is internally treated in the gas purification device while a part of the recovered ammonia is effectively used. Moreover, in the case of this example, the surplus ammonia is decomposed in a line (second gas line T2) separate from the line (first gas line T1) of the regeneration gas H1 containing sulfur. Therefore, it is easy to set and control the above-described distribution rate of the ammonia injection amount and the like, and it is possible to more reliably maintain the concentrations of nitrogen oxides and ammonia released to the atmosphere within an allowable range. This is because, for example, in the configuration of the first example, since ammonia is combusted with hydrogen sulfide, the combustion situation of ammonia becomes complicated in relation to the combustion of hydrogen sulfide, and the combustion conditions are also conditions for sufficiently combusting hydrogen sulfide. Is given priority, the amount of nitrogen oxides generated by the combustion of ammonia is relatively unstable, and it may be difficult to determine the optimal amount of ammonia to be distributed. May fluctuate under the influence of other parameters. However, in the case of this example, since ammonia is separately burned, there is no such problem. Also,
DeNOx catalysts and ammonia decomposition catalysts are generally susceptible to sulfur such as sulfur trioxide, and have problems such as deterioration and shortened life due to the presence of such impurities. Since the gas line for treating nitrogen and the gas line for treating nitrogen are separated as described above, there is a feature that such a problem does not occur at all.

The present invention is not limited to the above-described embodiment, but may have various aspects. For example, it is not always necessary to handle the recovered ammonia separately from the aqueous ammonia and the off-gas (ammonia-containing gas) as in the above-described embodiment (FIG. 3). For example, the cooler 59 and the condensate tank 60 in FIG. 3 are deleted, and the effective use of ammonia in the state of all the off-gas C3 or C4 (ammonia-containing gas),
The decomposition treatment of ammonia by the distribution injection of the present invention may be performed. Further, only the amount necessary for denitration treatment downstream of the gas turbine and effective use in the desulfurization device downstream of the combustion furnace is condensed and used as ammonia water C6.
Alternatively, all of C4 may be dispensed and injected by the method of the present invention for decomposition treatment. Further, the off-gas generated in the step of separating ammonia and other impurities (solid content) from the drainage of the cleaning liquid does not necessarily need to be decomposed as ammonia, which is the object of the present invention, as long as the ammonia concentration is within an allowable range. Alternatively, there may be a mode in which the waste gas is discharged to the atmosphere and discarded. For example, the off-gas C4 in FIG.
If the ammonia concentration or other harmful substance concentration is within the allowable range, it may be released to the atmosphere as it is.

Further, an acid or the like may be added to the cleaning liquid in the cleaning processing of the generated gas in the cleaning tower, if necessary, to adjust the pH to a value preferable for absorption of ammonia or hydrogen chloride. Alternatively, a plurality of washing towers for performing the washing process may be provided, and for example, the first washing tower may absorb mainly hydrogen chloride and the second washing tower may mainly absorb ammonia. Further, a cooler for cooling the cleaning liquid may be provided, and the operating temperature thereof may be actively controlled to a value suitable for absorbing ammonia or hydrogen chloride. Further, the combustion furnace is not limited to the regenerative heat exchange combustion furnace described above. However, if the combustion temperature is maintained at an appropriate temperature (for example, about 1000 ° C.) using the regenerative heat exchange combustion furnace as described above, excess nitrogen oxide (thermal knock) caused by oxidation of nitrogen (N ₂ ) in the gas is used. ) Is prevented, so that the load on the denitration apparatus can be reduced by that amount, and the setting and control of the above-described distribution and injection amount of ammonia can be more easily performed.

Further, the exhaust gas purification treatment for removing sulfur oxides (mainly sulfur dioxide) is not limited to the lime-gypsum method described above. For example, a so-called water using a magnesium compound as an absorbent for sulfur dioxide is used. It goes without saying that the mug method may be employed. Further, it goes without saying that the desulfurization treatment by the lime-gypsum method may not be adopted, and the elemental sulfur may be recovered from the sulfur content (mainly sulfur dioxide) absorbed from the exhaust gas. Also, the type of absorption tower of the desulfurization apparatus is not limited to the liquid column type absorption tower, and it goes without saying that various types such as a spray tower, a grid packed tower, and a gas dispersion type absorption tower can be adopted.

The gasification method may be, for example, a method using oxygen as a gasifying agent. Further, a denitration treatment of exhaust gas from the gas turbine and a denitration device therefor are not necessarily required. For example, when the concentration of nitrogen oxides contained in the exhaust gas is extremely low due to the properties of coal or the like, or the type of gasification furnace or gas turbine, the above-described denitration treatment is not necessary. In addition, raw materials to be gasified (carbon-containing fuel)
Is not limited to coal or petroleum, and may be, for example, wood, organic (bio) fuel, or waste plastic. Further, the gasification equipment to which the present invention is applied is not limited to equipment using a gas turbine for power generation (that is, gasification power generation equipment), and equipment using the gas turbine for driving or for use such as a compressor. It may be.

[0057]

According to the gas purification method of the present invention, a sulfur compound and other impurities (such as ammonia and hydrogen chloride) are separately absorbed and removed from a gas produced by gasification by a wet method.
The sulfur compound-containing gas (regenerated gas) generated when the absorbing solution for sulfur compound absorption is regenerated is burned in a combustion furnace to be converted into a sulfur oxide-containing gas (exhaust gas), and the sulfur oxide-containing gas is converted into a sulfur oxide-containing gas. In the gas purification method of performing an exhaust gas purification treatment for removing substances, the ammonia recovered from the cleaning liquid for removing impurities is distributed and injected into a gas inlet side and a gas outlet side of the combustion furnace, and further, the gas of the combustion furnace is further removed. If necessary, oxygen-containing gas for combustion is also injected into the inlet side, and the ammonia injected into the gas inlet side of the combustion furnace is burned together with sulfur compounds in the combustion furnace to oxidize and decompose,
Exhaust gas into which ammonia has been injected at the gas outlet side of the combustion furnace is introduced into an ammonia catalytic reduction type denitration apparatus in a high-temperature state before exhaust gas purification processing to perform denitration processing. The distribution injection amount of ammonia to the gas inlet side and the gas outlet side of the combustion furnace is set so that the ammonia concentration and the nitrogen oxide concentration fall within the allowable ranges. As a result, all of the various harmful substances (sulfur compounds, ammonia, nitrogen oxides, sulfur oxides) in the exhaust gas finally released to the atmosphere have low values, and all of the recovered ammonia is discharged in the gas purification device. An excellent effect that internal processing can be performed is obtained.

That is, all of the recovered ammonia is
For example, even if excess ammonia is not effectively used as an absorption aid in exhaust gas purification processing (mainly sulfur dioxide gas absorption processing) and excess ammonia is generated, as in the present invention, ammonia is distributed and injected before and after the combustion furnace and combustion is performed. If the denitrification treatment is performed downstream of the furnace, the amount of the distributed injection is increased as a whole and the capacity of the denitration device is made sufficient to decompose all the excess ammonia, and At the same time, since nitrogen oxides generated in the combustion furnace can be removed, there is no need to discharge the recovered ammonia to the outside while maintaining clean exhaust gas discharged to the atmosphere. By the way,
In a configuration in which all excess ammonia is simply introduced into the combustion furnace to decompose, a part of the introduced ammonia is oxidized in the exhaust gas downstream of the combustion furnace to produce nitrogen oxides. Depending on the amount of nitrogen introduced, nitrogen oxides in the exhaust gas downstream of the combustion furnace may exceed an allowable range. However, in the present invention, ammonia is injected into the downstream side of the combustion furnace according to the amount to be injected into the inlet side of the combustion furnace, without excess or deficiency. Is effectively decomposed and removed by a catalytic reaction with the ammonia injected into the gas, and the ammonia remaining in the gas thereafter hardly remains. In addition, if there is another use of ammonia in other facilities adjacent to the gasification facility, for example,
The remaining ammonia may be supplied to the facility and used effectively, but if there is no such use, conventionally, for example, the only option is to decompose and treat the ammonia with a complicated treatment using microorganisms . However, if ammonia is distributed and injected before and after the combustion furnace and denitration is performed downstream of the combustion furnace as in the present invention, even if a large amount of ammonia remains, it can be easily processed internally.

Further, as in the gas refining method according to claim 2, the ammonia concentration in the exhaust gas after the denitration treatment is equal to or higher than the reaction equivalent to the sulfur trioxide concentration in the exhaust gas after the denitration treatment. When the distribution injection amount is set, a small amount of sulfur oxide (that is, sulfur trioxide), which is difficult to remove in a general exhaust gas purification process (for example, a lime gypsum method wet desulfurization process) for removing a sulfur oxide, is set. Has the advantage that the exhaust gas discharged to the atmosphere can be further cleaned. That is, if ammonia equivalent to the sulfur trioxide concentration or more remains in the exhaust gas after the denitration treatment downstream of the combustion furnace, most of the sulfur trioxide in the exhaust gas is cooled by the subsequent cooling. This is because it reacts with the residual ammonia to be neutralized and becomes harmless ammonium sulfate, which can be easily removed in the exhaust gas purification treatment.

Next, in the gas refining method according to the third aspect, the sulfur compound and other impurities (ammonia, hydrogen chloride, etc.) are separately absorbed and removed from the gas produced by gasification by a wet method, and the absorption for sulfur compound absorption is performed. Exhaust gas purification in which a sulfur compound-containing gas (regenerated gas) generated when a liquid is regenerated is burned in a combustion furnace to convert it into a sulfur oxide-containing gas (exhaust gas), and sulfur oxide is removed from the sulfur oxide-containing gas. In a gas purification method for performing a treatment, a heat exchanger that heats and discharges a gas with heat from a combustion furnace, an ammonia decomposition device into which the heated gas discharged from the heat exchanger is introduced, and an ammonia decomposition device And a denitration apparatus into which the gas discharged from the furnace is introduced in a high-temperature state, on a second gas line separate from the first gas line through which the regeneration gas and the exhaust gas flow. Ammonia recovered from the cleaning solution for use is distributed and injected into the gas inlet side of the heat exchanger and the gas outlet side of the ammonia decomposer on the second gas line, and is further required at the gas inlet side of the heat exchanger. The oxygen-containing gas for combustion is also injected according to the above, the ammonia injected into the gas inlet side of the heat exchanger is burned by the heat of the combustion furnace, and further introduced into the ammonia decomposer to oxidize and decompose. The gas into which the ammonia has been injected and which has been injected is introduced into a denitration apparatus in a high-temperature state to perform denitration processing, and the ammonia concentration and the nitrogen oxide concentration in the gas after the denitration treatment on the second gas line are reduced. The distribution injection amount of ammonia to the gas inlet side of the heat exchanger and the gas outlet side of the ammonia decomposer is set so as to be within the allowable range. Therefore, various harmful substances (sulfur compounds, ammonia, nitrogen oxides,
(Sulfur oxide) has a low value, and furthermore, all the recovered ammonia can be internally treated in the gas purification apparatus.

Further, in the case of the present invention, the surplus ammonia is decomposed in a separate line (second gas line) from the regeneration gas line (first gas line). It is advantageous in that the setting and control of the distribution injection amount and the like can be easily performed, and the concentration of nitrogen oxides and ammonia released to the atmosphere can be more reliably maintained within an allowable range. This is because, for example, in the configuration of claim 1, ammonia is combusted with hydrogen sulfide, so that the combustion state of ammonia becomes complicated in relation to the combustion of hydrogen sulfide, and the combustion conditions are such that hydrogen sulfide is sufficiently combusted. Since the conditions are prioritized, the amount of nitrogen oxides generated by the combustion of ammonia is relatively unstable, and it may be difficult to determine the optimal amount of ammonia to be distributed. Etc., may fluctuate under the influence of other parameters. However, in the case of the present invention, such a problem does not exist because ammonia is separately oxidized and decomposed. Further, the denitration catalyst and the ammonia decomposition catalyst are generally vulnerable to sulfur such as sulfur trioxide, and have a problem that the life is shortened due to deterioration due to the presence of such impurities, but in the case of the present invention, Since the gas line for processing the sulfur content and the gas line for processing the nitrogen content are separated as described above, there is a feature that such a problem does not occur at all.

Further, as in the gas refining method according to the fourth aspect, ammonia is also distributed and injected to the gas outlet side of the combustion furnace in the first gas line, and the ammonia in the exhaust gas at the gas outlet side of the combustion furnace is injected. When the distribution injection amount of ammonia to the gas outlet side of the combustion furnace is set so that the concentration is equal to or higher than the reaction equivalent to the sulfur trioxide concentration in the exhaust gas, similar to the invention of claim 2, There is an advantage that even trace amounts of sulfur oxides (that is, sulfur trioxide) which are difficult to remove can be effectively removed from the exhaust gas on the first gas line, and the exhaust gas discharged to the atmosphere can be further cleaned.

Further, in the gas refining method according to the fifth aspect, a regenerative heat exchange combustion furnace is employed as a combustion furnace, and nitrogen oxide (N ₂ ) in a gas introduced into the combustion furnace is oxidized. The regeneration gas is burned in a low temperature range where (thermal knock) does not occur. For this reason, the load of the denitration device downstream of the combustion furnace can be reduced by that much, and the setting and control of the above-mentioned distribution injection amount of ammonia can be more easily performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cleaning unit and a desulfurization unit of a gas purification device that implements an example of the present invention.

FIG. 2 is a diagram showing a regeneration gas combustion section (ammonia processing section) and an exhaust gas purification processing section in the same apparatus.

FIG. 3 is a diagram showing a configuration of a cleaning liquid drainage treatment section in the same apparatus.

FIG. 4 is a diagram showing a combustion furnace in the apparatus.

FIG. 5 is a view for explaining the operation of the combustion furnace in the apparatus.

FIG. 6 is a diagram showing a regeneration gas combustion unit (ammonia processing unit) and an exhaust gas purification processing unit of a gas purification device that implements another example of the present invention.

[Explanation of symbols]

7 Cleaning tower 21 Desulfurization tower 22 Regeneration tower 41 Combustion furnace 42, 63 Denitration device 61 Heat exchanger 62 Ammonia decomposition device A1 to A5 Product gas B Cleaning solution C Drainage C6 Ammonia water C4, C7 Offgas (ammonia-containing gas) F Absorption solution ( H1 Regeneration gas (gas on the first gas line) H2, H2, H4 Exhaust gas (gas on the first gas line) J1 Air (oxygen-containing gas) K Absorbent (for sulfurous acid gas absorption) S1, S2, S3, S4 gas (gas on the second gas line) T1 first gas line T2 second gas line

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B01D 53/77 B01D 53/34 ZAB 53/86 125E C10J 3/46 53/36 E C10K 1/14 (72) Inventor Susumu Okino 4-62 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Inside Mitsubishi Heavy Industries, Ltd.Hiroshima Research Center F-term (reference) 4D002 AA02 AC10 BA02 CA01 CA07 CA13 DA05 DA07 DA16 EA06 EA07 EA12 FA03 FA06 GA01 GA02 GA03 GB02 GB03 GB06 HA04 HA08 4D020 AA04 AA10 BB03 BC01 CB08 CC01 CC05 CC21 CD03 CD10 DA01 DA02 DB02 DB03 AB03A04 BA23X BA26X BA27X BA30X BA31X BA32X BA33X BA41X CA04 CC38 4H060 AA01 BB04 BB23 CC18 DD12 DD13 DD21 FF04 FF13 GG01

Claims (5)

[Claims] 1. A gas produced by gasification of a carbon-containing fuel is brought into gas-liquid contact with a cleaning liquid to absorb and remove impurities including ammonia in the produced gas. While the sulfur compound contained in the product gas is absorbed and removed by liquid contact, heat is applied to the absorbing solution that has absorbed the sulfur compound to regenerate, and a regeneration gas containing the sulfur compound generated in the regeneration is burned in a combustion furnace. To convert it to exhaust gas containing sulfur oxides,
In the gas purification method of performing an exhaust gas purification process for removing sulfur oxides in the exhaust gas, the ammonia recovered from the cleaning liquid is distributed and injected into a gas inlet side and a gas outlet side of the combustion furnace, and Oxygen-containing gas for combustion is also injected into the gas inlet side of the combustion furnace as necessary, and the ammonia injected into the gas inlet side of the combustion furnace is burned with the sulfur compound in the combustion furnace to oxidize and decompose. The exhaust gas into which the ammonia has been injected at the gas outlet side of the combustion furnace is introduced into an ammonia catalytic reduction type denitration apparatus while being kept in a high temperature state before the exhaust gas purification processing to perform the denitration processing. The aforesaid gas is fed to the gas inlet and gas outlet of the combustion furnace so that the ammonia concentration and the nitrogen oxide concentration in the exhaust gas after the treatment fall within the allowable ranges. Gas purification method characterized by setting the distribution amount of injected pneumoniae. 2. A gas inlet side and a gas outlet side of the combustion furnace so that the ammonia concentration in the exhaust gas after the denitration treatment is equal to or more than the reaction equivalent to the sulfur trioxide concentration in the exhaust gas after the denitration treatment. 2. The gas purification method according to claim 1, wherein a distribution injection amount of the ammonia is set. 3. A gas produced by gasification of a carbon-containing fuel is brought into gas-liquid contact with a cleaning liquid to absorb and remove impurities including ammonia in the produced gas. While the sulfur compound contained in the product gas is absorbed and removed by liquid contact, heat is applied to the absorbing solution that has absorbed the sulfur compound to regenerate, and a regeneration gas containing the sulfur compound generated in the regeneration is burned in a combustion furnace. To convert it to exhaust gas containing sulfur oxides,
In a gas purification method for performing an exhaust gas purification treatment for removing sulfur oxides in the exhaust gas, a heat exchanger that heats and discharges gas with heat of the combustion furnace;
An ammonia decomposition apparatus into which an ammonia decomposition catalyst for decomposing ammonia into nitrogen and nitrogen oxides is loaded and into which the heated gas discharged from the heat exchanger is introduced; and an ammonia catalytic reduction type denitration catalyst A denitration device in which the gas discharged from the decomposition device is introduced in a high-temperature state;
It is installed on a second gas line separate from the gas line, and the ammonia recovered from the cleaning liquid is supplied to the gas inlet side of the heat exchanger and the gas outlet side of the ammonia decomposer on the second gas line. Distribute and inject, and further, if necessary, inject oxygen-containing gas for combustion into the gas inlet side of the heat exchanger, and feed the ammonia injected into the gas inlet side of the heat exchanger into the heat of the combustion furnace. In addition, while introducing the ammonia into the ammonia decomposition apparatus to oxidize and decompose, the gas discharged from the ammonia decomposition apparatus and into which the ammonia is injected is introduced into the denitration apparatus in a high temperature state to perform the denitration processing. The gas inlet side of the heat exchanger and the gas of the ammonia decomposer so that the ammonia concentration and the nitrogen oxide concentration in the gas after the denitration treatment fall within the allowable range. Gas purification method characterized by setting the distribution injection amount of the ammonia to the outlet side. 4. The ammonia is also distributed and injected into the first gas line at a gas outlet side of the combustion furnace,
The distribution injection amount of the ammonia to the gas outlet side of the combustion furnace is set such that the ammonia concentration in the exhaust gas at the gas outlet side of the combustion furnace is equal to or higher than the reaction equivalent to the sulfur trioxide concentration in the exhaust gas. The gas purification method according to claim 3, wherein the gas purification is performed. 5. A regenerative heat exchange combustion furnace is adopted as the combustion furnace, and nitrogen (N ₂ ) in a gas introduced into the combustion furnace is oxidized in a low temperature range where nitrogen oxides are not generated.
5. The gas purification method according to claim 1, wherein the regeneration gas is burned.