CN1221778A

CN1221778A - Coal gas purifier

Info

Publication number: CN1221778A
Application number: CN98116497A
Authority: CN
Inventors: 多谷淳; 洲崎诚; 香川晴治; 世良俊邦; 冲野进; 本城新太郎
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1997-08-29
Filing date: 1998-08-28
Publication date: 1999-07-07
Anticipated expiration: 2018-08-28
Also published as: JPH1180760A; CN1092228C; JP4227676B2

Abstract

A coal gas purifier is disclosed. The purifier includes: a desulfurizing tower 21 usable for bringing synthetic gas in contact with absorption solution to absorb and eliminate sulfureted hydrogen in synthetic gas; a scrubbing tower 7 usable for bringing synthetic gas in gas-and-liquid contact with washing solution to wash before synthetic gas is guided into the desulfurizing tower 21; a convertor on the upstream of the scrubbing tower 7 usable for converting carbonyl sulfide in the synthetic gas into sulfureted hydrogen.

Description

Gas purifying device

The present invention relates to a wet purification apparatus for synthetic gas used in a coal gasification process orthe like, and more particularly, to a gas generator capable of easily removing sulfur compounds and other impurities from gas and remarkably reducing the volume of a heat exchanger required for cooling and reheating the synthetic gas for the removal.

In recent years, due to depletion of petroleum resources and rising petroleum prices, there has been a high demand for diversification of fuels, and technologies for utilizing coal and heavy oil have been developed, and among these, technologies for gasifying coal or heavy oil and using the gasified coal or heavy oil as a power generation fuel or a synthetic raw material have been attracting attention. In addition, compared with conventional thermal power generation using coal or oil, power generation using coal gas obtained by coal gasification has advantages of high efficiency and effective use of limited resources, and thus has been receiving attention.

However, the synthesis gas obtained by coal gasification contains 100 to 1000ppm of sulfur compounds (mainly hydrogen sulfide). In order to prevent such a pollution caused by the coal gas obtained by coal gasification or to prevent corrosion thereof to downstream equipment (e.g., a gas turbine, etc.), these sulfur compounds must be removed. As a method for removing sulfur, for example, a wet gas purification technique is known in which gas and an absorbent are brought into gas-liquid contact with each other as described in JP-A-7-48584.

In addition, sulfur compounds contained in the coal gas produced by coal gasification, except for H₂S (hydrogen sulfide) contains COS (carbonyl sulfide) of about 100ppm, and it cannot be removed by the absorption liquid.

Therefore, in order to remove COS in the wet gas purification process, it is necessary to convert COS into H by hydrolysis reaction in advance in the upstream of the desulfurization tower in which the gas-liquid contact is performed between the absorption liquid and the gas₂And S. As a catalyst for such conversion, a catalyst obtained by adding an additive such as Li or Na to titanium oxide, as shown in, for example, Japanese patent publication No. 63-11053 and Japanese patent application laid-open No. 1-223197, has been known.

However, in the above-mentioned prior art gas purification technology, chlorine-containing compounds (HCl) and nitrogen-containing compounds (NH) contained in the synthesis gas are not specifically considered₃) And the like, and improvements in these techniques are desired.

That is, for example, 10 is generally contained in the formed coal gas obtained by a coal gasification process or the like0 to 1500ppm NH₃And about 100ppm HCl, these impurities must be removed for further purification.

Among these impurities, HCl, which is a chlorine-containing compound, is itself a strong acid and is corrosive even to stainless steel materials, and it is necessary to remove it as much as possible on the upstream side from the viewpoint of protecting the plant materials, and when the synthesis gas is burned in a plant such as a gas turbine, the chlorine-containing compound is discharged into the atmosphere as contained in the flue gas, and therefore, it is necessary to remove it in order to reduce the amount of the chlorine-containing compound discharged.

Further, ammonia as a nitrogen-containing compound is hardly removed in a gas-liquid contact treatment in a desulfurizing tower which generally uses an absorbing liquid (alkaline) composed of an amine compound, and thus becomes a harmful nitrogen oxide when burned in a gas turbine or the like. Such nitrogen oxides are generally removed in a denitration device provided downstream of a gas turbine or the like,which causes a problem of increasing the load on the device.

Therefore, the present applicant has proposed a technique for removing the above-mentioned impurities by washing a synthesis gas (hereinafter, sometimes referred to simply as a gas) by bringing the gas into gas-liquid contact with a washing liquid on the upstream side of a desulfurization tower, thereby removing the above-mentioned impurities. However, in this case, there are still problems of the positional relationship between the washing tower for performing the above washing process and the COS converter for performing the above COS conversion, and the equipment structure of the heat exchanger or the like for effectively utilizing the heat in the synthesis gas.

That is, according to the knowledge of the inventors, impurities such as halogen-containing compounds in the gas, represented by HCl, are known to convert COS to H₂The activity of a conventional catalyst for S is harmful, and therefore, in order to avoid such a decrease in activity, it is preferable to dispose the above-mentioned washing column upstream of the COS converter so as to wash out the above-mentioned impurities in advance.

However, the performance (conversion rate) of the COS converter tends to decrease with a decrease in temperature, and in this case, in order to achieve a practical level of the performance of the converter, it is necessary to reheat the gas cooled by contact with the scrubbing liquid in the scrubbing tower to a minimum of about 150 ℃. In addition, in order to secure the performance of the desulfurization tower, it is preferable to lower the temperature of the gas discharged from the COS converter and introduced into the desulfurization tower to about 40 ℃.

Further, in order to maintain the treated gas fed into a gas turbine or the like in a high temperature state to achieve high thermal efficiency, it is necessary to recover heat from the high temperature gas before being introduced into the scrubber and to heat the treated gas discharged from the desulfurizer.

Therefore, when the scrubber is disposed upstream of the COS converter, the equipment configuration becomes complicated as shown in FIG. 7, which leads to an increase in the size and cost of the equipment, which is a significant practical problem,

in the apparatus shown in fig. 7, reference numeral Q1 denotes a synthetic gas before purification treatment, which is obtained by recovering heat from a coal gasifier (not shown) in a steam heater (not shown) and then removing dust through a porous filter or the like (not shown), and has a temperature of about 420 ℃.

The synthesis gas Q1 is then first introduced into the heat exchanger 101, where the heat of the synthesis gas Q1 is used to heat the treated gas Q4, thus inversely reducing the temperature of the synthesis gas Q1 to about 177 ℃.

Next, the synthesis gas Q1 is introduced into the scrubber 102, and contacts with the scrubbing liquid to absorb and remove impurities such as hydrogen chloride and ammonia, and the synthesis gas itself is cooled to lower the temperature of the synthesis gas to the dew point temperature (about 40 ℃), which is referred to as gas Q2.

Next, the gas Q2 discharged from the scrubber 102 is introduced into the heat exchanger 103, which is heated to about 120 ℃ by the heat of the gas Q3 described below, and then introduced into the following heater 104, where it is further heated to about 150 ℃.

The gas Q2 is then removed from heater 104, to which steam QW is added to supplement cooling due to upflowThe water lost by condensation is then introduced into a COS converter 105 filled with the above catalyst to convert COS contained therein into H₂S, then it becomes gas Q3 containing almost no COS.

Next, the gas Q3 discharged from the COS converter 105 was cooled in a counter-current manner in the heat exchanger 103 from about 150 ℃ to about 72 ℃, further cooled in the cooler 106 by heat exchange with industrial water to about 40 ℃, and then introduced into the desulfurization tower 107.

Then, the gas is brought into gas-liquid contact with an absorbent containing an amine absorbent in the desulfurizing tower 107 to remove H in the gas Q3₂And S, finally discharging the gas as clean gas Q4 (with the temperature of about 42 ℃) almost free of sulfur or other impurities.

Subsequently, the gas Q4 discharged from the desulfurizing tower 107 is heated by the heat exchanger 101 to raise the temperature to about 300 ℃, and finally, the coal gasification gas Q5 is sent to a facility such as a gas turbine of a combined cycle power generation system as a clean and high-temperature purified coal gasification gas.

Thus, according to the configuration shown in fig. 7, the heat transfer areas of the two

heat exchangers

101 and 103 need to be 2262m each²And 2898m²In addition, the heat transfer areas of the heater 104 and the cooler 106 need to be 754m each²And 715m²So that the total heat transfer area of the heat exchangers reaches 6629m²。

In addition, the heater 104 requires thermal energy for heating and also requires the steam Qw and the coolant for the cooler 106, which makes the equipment cost and the running cost very high as the apparatus becomes larger.

In addition, this not only increases the size of the apparatus but also increases the cost. And the gas temperature in the COS converter, as described above, can only reach 150 c, so the conversion efficiency of COS cannotbe improved.

Therefore, an object of the present invention is to provide a gas purification apparatus capable of removing impurities such as chlorine-containing compounds and nitrogen-containing compounds while more completely absorbing sulfur-containing compounds in gas with a small equipment configuration and at low cost.

In order to achieve the above object, a gas purifying apparatus according to the present invention is a gas purifying apparatus for purifying a synthetic gas obtained by gasifying coal or heavy oil, the gas purifying apparatus including:

a desulfurizing tower for bringing the synthesis gas into gas-liquid contact with an absorbing liquid to absorb and remove at least hydrogen sulfide contained in the synthesis gas,

a washing tower for washing the synthetic gas by contacting the synthetic gas with a washing liquid in a gas-liquid manner before the synthetic gas is introduced into the desulfurization tower,

a converter disposed upstream of said scrubber for converting carbonyl sulfide in said synthesis gas to hydrogen sulfide.

In the gas purification apparatus of the present invention, it is preferable that the catalyst filled in the converter for promoting the reaction of converting carbonyl sulfide into hydrogen sulfide is a catalyst made of titanium oxide and containing no additive having a strong affinity for impurities in the synthetic gas.

In addition, the gas purification apparatus according to the present invention is configured such that heat required for heating the synthesis gas treated in the desulfurization tower is recovered from the synthesis gas on the downstream side of the converter, not from the synthesis gas on the upstream side of the converter.

In the gas purification apparatus, the heat required for heating the synthesis gas treated in the desulfurization tower is recovered from the synthesis gas on both the downstream and upstream sides of the converter.

Fig. 1 shows the configuration of a pretreatment section of a main part of a purification apparatus according to example 1 of the present invention.

Fig. 2 shows the configuration of the desulfurization unit and the gypsum recovery unit in the same purification apparatus.

Fig. 3 shows the configuration of a pretreatment section of a main part of a purification apparatus according to example 2 of the present invention.

Fig. 4 shows the configuration of a pretreatment section of a main part of a purification apparatus according to example 3 of the present invention.

Fig. 5 shows the configuration of the main part of each example of the present invention.

Fig. 6 is a graph showing COS conversion data when temperature conditions are used as parameters.

Fig. 7 shows the constitution of the main part of the purification apparatus in which the COS converter is disposed downstream of the scrubber.

Embodiments of the present invention are explained below with reference to the drawings.

Example 1

Example 1 is explained first. Fig. 1 shows the constitution of a pretreatment section of a main part in the gas purification apparatus of the present example; fig. 2 shows the configuration of the desulfurization section and the gypsum recovery section in the same apparatus.

First, the configuration of the preprocessing section and its basic functions will be explained. As shown in fig. 1, in the coal gasification furnace 1, coal is gasified using, for example, air as a gasifying agent, and a synthetic gas a containing carbon monoxide and hydrogen as main components is produced.

The synthetic gas A produced by using coal as a raw material and air as a gasifying agent usually contains about 1000 to 1500ppm of H₂S (sulfur-containing compound) and about 100ppm of COS (sulfur-containing compound), and further contains about 100-1500 ppm of NH₃(nitrogen-containing compounds) and about 100ppm HCl (chlorine-containing compounds).

The temperature of the synthesis gas a immediately at the furnace outlet is usually 1000 to 1300 ℃, but the synthesis gas a is cooled to, for example, about 420 ℃ by recovering heat therefrom using a steam heater (not shown) provided on the outlet side of the synthesis furnace, and the pressure thereof is, for example, about 26 atmospheres.

The synthesis gas A is introduced into a cyclone 2 and a porous filter 3 in this order, thereby separating and removing the larger particle size dust and the fine dust, respectively.

Arranged downstream of the porous filter 3A converter 5 containing a catalyst for converting COS to H₂The catalyst for S, COS in the synthesis gas Al, is almost completely converted into H₂S。

In this case, as the catalyst of the converter 5, a catalyst formed of a titanium oxide simple substance can be used, but it is preferable to use at least a catalyst containing no additive (Li, Na, K, Cs, Mg, Ca, Ba, Zn, Cd, Sn, Pb) described in japanese patent publication No. 63-11053.

The reason for this is as follows, and according to the studies of the inventors, it was found that when a catalyst containing no such additive is used, the activity of the catalyst is not impaired even if impurities such as a halide are present in the gas. It is also believed that these additives have a strong affinity for impurities such as halides, and thus, when these impurities are present in the gas, the catalyst capacity is rather reduced. For example, an alkali metal hydroxide (e.g., KOH) in the catalyst can react with hydrogen chloride to become a halide (e.g., KCl), thereby changing the chemical properties as a catalyst, thereby reducing its catalytic ability.

Further, a heat exchanger 6 is provided downstream of the converter 5, and the purified gas a4 is heated by the heat of the gas a2 from the converter 5. The gas a2 is deprived of heat in countercurrent by the heat exchanger 6, in this case cooled to around 177 ℃.

Then, a scrubber 7 is provided downstream of the heat exchanger 6 so that the gas a2 is brought into gas-liquid contact with the scrubbing liquid B before being introduced into the desulfurizing tower 21 described below.

In the case where the washing column 7 is a so-called packed gas-liquid contact column, the washing liquid B containing water as a main component stored in the bottom of the column is sucked upward by the circulation pump 8, and then is discharged through the spray pipe 9 in the upper part of the column, and flows downward through the packing 10 while being in gas-liquid contact with the gas a2, and returns to the bottom of the column again, thereby forming a circulation.

In addition, in the case where the scrubbing tower 7 is a so-called countercurrent scrubbing tower, the gas A2 introduced from the lower part of the tower rises in the tower against the scrubbing liquid B flowing downward,in the removal of HCl or NH₃After that, the gas A3 is discharged from the top of the column as a washed gas.

That is, in the scrubber 7, the synthesis gas a2 before being introduced into the desulfurizer 21 is brought into gas-liquid contact with the scrubbing liquid B mainly composed of water, and therefore, NH having a high solubility is contained in the gas a2₃Or HCl, is absorbed into the washing liquid B in a considerable amount even without performing pH adjustment exclusively on the washing liquid B, and is finally discharged to the outside of the system as drain water C. Thus, the gas A5, in which there is a considerable amount of NH, is finally obtained₃And HCl withSame as H₂S is removed altogether, thereby becoming an unprecedented cleaning product.

Further, NH usually contained in the gas A2₃More HCl was present, so that if the pH was not adjusted, Wash B also showed alkalinity. When the washing liquid B becomes alkaline, it only reduces its NH pair₃While the weakly acidic H contained in the gas A2₂S is also absorbed into the washing liquid B in a considerable amount and is consequently contained in the drain water C. In this case, the wastewater treatment of the wastewater C becomes a problem of large scale and high cost because the discharge regulation has strict restrictions on the sulfur compounds and it is difficult to achieve the harmless treatment.

In order to solve the above problem, the present example is to adjust the pH of the washing liquid B of the washing tower 7 by appropriately supplying an acid E such as sulfuric acid to the washing liquid B, for example, to keep the pH of the washing liquid B at weak acidity or less. This can suppress H contained in the drainage C₂S, thereby avoiding troublesome drainage treatment. In this case, since HCl is a strong acid, HCl can be sufficiently absorbed by a washing solution in a weak acid range.

However, NH is removed for more complete absorption₃It is preferred to reduce the pH considerably, for example to the strongly acidic range, but in this case the absorption of HCl is reduced, so that HCl and NH are removed more completely₃Both, preferably in a two-tower configuration, i.e. with a primary NH absorption unit₃And a washing towerA scrubber column mainly used for absorbing HCl.

Further, since the gas a3 is cooled when it comes into contact with the scrubbing liquid B, it can be made to have a temperature (about 40 ℃) suitable for introduction into the desulfurizing tower 21 without providing a special cooler.

Further, a part of the washing liquid B is drawn out through a branch pipe on the outlet side of the circulation pump 8 and discharged to the outside of the system as drain water C. In addition, make-up water D may be suitably supplied at any position in the circulation path of the scrubbing liquid B to make up for the water lost as drainage C or entrained in the gas. Further, a mist eliminator 11 for separating and removing mist droplets in the gas is provided in the upper part of the scrubber 7, so that the amount of so-called entrained mist droplets flowing out from the downstream side can be suppressed to a low level.

The constitution of the desulfurization section and its operation are explained below with reference to FIG. 2. The desulfurization section is mainly composed of a desulfurization tower 21 and a regeneration tower 22.

The desulfurization tower 21 is a gas-liquid contact tower similar to the washing tower 7, and the hydrogen sulfide absorbent F stored at the bottom of the regeneration tower 22 is pumped upward by the circulation pump 23, cooled in the absorbent heat exchanger 24, and then discharged through the spray pipe 25 at the top of the tower, and flows downward through the packing 26 while being in gas-liquid contact with the gas a 3.

H is removed by gas-liquid contact with the absorbent F₂The S gas a4 (having a temperature of about 42 ℃) is discharged from the top of the desulfurizing tower 21 after entrained droplets are removed by the droplet removing device 21, and then heated by the heat exchanger 6 in fig. 1 to become purified gas a 5.

In addition, the pressure of the coal gas A5 became about 25.5 atmospheric pressure, the temperature became about 300 ℃, and the sulfur content (H) thereof was about₂The concentration of S and COS) to less than 10 ppm.

On the other hand, in the regeneration tower 22, the absorption liquid F stored in the bottom of the desulfurization tower 21 is pumped upward by the circulation pump 28, heated in the absorption liquid heat exchanger 24, and then sprayed out through the spray pipe 29 in the upper part of the tower, and flows downward through the packing 30 while contacting with the vapor of the absorption liquid F and the absorption component (off gas) rising along the tower.

The absorption liquid F at the bottom of the regeneration column 22 is heated by the steam G in the reboiler 31, thereby causing H as an absorption component₂S is volatilized to the gas side in the regeneration tower 22. This then contains H₂The exhaust gas H containing S is treated to remove mist in the mist eliminator 32, and then passes through a reflux part provided at the top of the regeneration tower 22 as a gas containing H at a higher concentration₂Exhaust gas H1 of S (CO as a main component)₂) Is sent to a gypsum recovery unit described below.

In the reflux unit provided at the top of the regeneration tower 22, the condensate I of the exhaust gas H generated by cooling the exhaust gas H by the cooler 33 and stored in the storage tank 34 is pumped by the pump 35 and sprayed from the spray pipe 36, so that the vapor in the exhaust gas H is largely liquefied, and the H as the absorbing component in the liquid is liquefied₂S is more volatile, so that a high concentration H of, for example, about 20% by volume is obtained₂Exhaust H1 of S.

The constitution of the gypsum recovery section and its operation are explained below. The gypsum recovery section of this example is composed of a combination of a combustion furnace 41 and a wet limestone-gypsum-process desulfurization apparatus, and the combustion furnace 41 is used to react H contained in the exhaust gas H1 with air J₂S is burned, the waste gas H1 is burned in the combustion furnace 41 to become combustion waste gas H2, and the desulfurization device is used for absorbing and removing SO from the combustion waste gas H2₂Sulfur oxides such as (sulfurous acid gas) and the like are discharged as a harmless exhaust gas H3.

The desulfurization apparatus comprises a reactor 42, an air supply device (not shown) and a solid-liquid separation device 44 such as a centrifuge, and the reactor 42 functions to contain H at a high concentration₂SO formed by combustion of S₂With a combustion exhaust gas H2 fed into the interior of the reactor and with a slurry K containing a calcium compoundGas-liquid contact is carried out, and then the waste gas is discharged; the air supply means functions to blow the oxidizing air L into the slurry in the reactor 42 as a plurality of fine bubbles; the solid-liquid separator 44 serves to separate solid and liquid of the slurry M (gypsum slurry) drawn out of the reactor 42。

Also shown at 46 in FIG. 2 is a cooler which functions to cool the combustion exhaust H2 to a temperature suitable for absorbing SO therein₂Etc. of the substance. The separated water M3 produced by the solid-liquid separation in the solid-liquid separator 44 is returned as water constituting the slurry in the reactor 42 as it is to the reactor 42 in this case.

The reactor 42 may be constituted by a so-called slurry circulation type absorption tower, specifically, for example, a slurry tank for blowing the oxidizing air L thereinto may be provided at the bottom of the tower, and a gas-liquid contact portion in the form of a packed type, a spray type, a liquid column type or the like for spraying the slurry in the slurry tank may be provided at the upper portion of the tower through which the combustion gas H2 flows. Alternatively, the reactor 42 may be a SO-called bubbling type apparatus in which both the air L for oxidation and the combustion exhaust gas H2 are simultaneously blown into the slurry in the tank, SO₂Etc. are all carried out in the slurry tank.

In summary, the reactions shown, for example, in the following reaction formulae (1) to (3) are carried out in the reactor 42, mainly for the absorption of SO₂And forming dihydrate gypsum.

(1)

(2)

The slurry K supplied to the reactor 42 may be, for example, limestone (CaCO)₃) The calcium-containing compound is mixed with industrial water or the like in a slurry tank (not shown). Of course, the calcium-containing compound may be directly fed into the reactor 42 in a finely divided solid state to be reacted. Further, a gypsum heating apparatus 45 (gypsum heating step) is provided, and the solid matter M1 (gypsum cake of dihydrate gypsum) obtained by the solid-liquid separation apparatus 44 is heated therein to 120 to 150 ℃ to obtain hemihydrate gypsum M2.

The amount of the calcium-containing compound to be supplied can be basically determined according to the amount of the sulfurous acid gas to be absorbed. In actual operation, the supply amount may be finely adjusted by, for example, detecting the pH of the slurry in the reactor 42 or the concentration of unreacted limestone so as to maintain the pH at a value optimum for the absorption reaction or the like.

The oxidizing air L is preferably supplied in a minimum amount necessary by, for example, detecting the oxidation-reduction potential of the slurry in the reactor 42.

With the gas cleaning apparatus according to the above configuration, the COS converter 5 and the gas a3 discharged from the scrubber 7 are directly introduced into the desulfurization tower 21 at its current temperature by disposing the same on the upstream side (high temperature side) of the scrubber 7, and therefore, all of the devices corresponding to the heat exchanger 103, the heater 104 and the cooler 106 shown in fig. 7 may be unnecessary, and the heat energy necessary in the heater 104 and the coolant necessary in the cooler 106 may also be unnecessary.

That is, if the main part of the present example is configured as shown in the same drawing as fig. 7, the apparatus is configured as shown in fig. 5(a), and in this case, the heat engine can be operated by a very simple facility only by providing the heat exchanger 6, and therefore, the running cost is low. In this case, the temperature conditions of the gas inlet and outlet in the heat exchanger 6 are the same as those of the heat exchanger 101 shown in FIG. 7, and the heat transfer area of the heat exchanger 6 may be 2262m²Thus, in the case of the present example, the total heat transfer area of the heat engine is 2262m²This area is much smaller than the total heat transfer area formed by fig. 7.

In addition, the gas a1 introduced into the COS converter 5 in this example contains more moisture than the gas Q2 introduced into the COS converter 105 in fig. 7, and thus it is not necessary to exclusively supply the steam QW as shown in fig. 7.

Therefore, according to the present example, the apparatus can be significantly miniaturized and the running cost can be significantly reduced.

Moreover, the operating conditions of the scrubbing tower and the desulfurizing tower were not changed, and therefore, the performance as a purification apparatus (removal rate of sulfur compounds and other impurities) was equivalent to or higher than that of the constitution shown in FIG. 7.

Particularly, the gas temperature in the COS converter 5 is high, reaching around 420 ℃, so that the conversion rate of COS is high, with the result that the removal rate of COS is significantly higher than that obtained by the configuration shown in fig. 7.

For example, in the case of using the above-described simple substance titanium oxide as the catalyst of the COS converter 5, with respect to the relationship between the conversion rate of COS and the temperature condition, the experimental results as shown by the solid line and the black dots of the graph in fig. 6 were obtained, and a very high conversion rate as high as about 95% was obtained in the case of 420 ℃.

In addition, in the case of a general COS converter as disclosed in, for example, japanese patent publication No. 63-11053, experimental results shown by triangular symbols in fig. 6 were obtained, and particularly, the performance thereof was remarkably lowered with a decrease in temperature. Therefore, from the viewpoint of improvement in the COS conversion rate, the temperature condition of the COS converter 5 can obtain a high conversion rate regardless of the catalyst used, and it can be seen that the constitution of the present example is effective.

In addition, although the graph in fig. 6 shows data when impurities such as halides harmful to the activity of the COS conversion catalyst are not present in the gas, as described above, for example, in the case of using a simple titanium oxide (solid lines and black circles in fig. 6), the performance thereof can be maintained even if such impurities are present. Example 2

Example 2 is explained below. Fig. 3 shows the configuration of the main pretreatment unit of the gas purification apparatus of this example. The main part of the structure of this example is also shown in fig. 7, which is shown in fig. 5 (b). The same elements as in example 1 are denoted by the same reference numerals, and redundant description thereof is omitted.

In this example, a heat exchanger 4 is provided on the upstream side of the COS converter 5 (the downstream side of the porous filter) on the basis of the constitution of example 1, so as to recover heat from the gas on the downstream side and the upstream side of the COS converter 5 and heat the gas a4 treated in the desulfurizing tower 21 with the heat.

That is, the heat exchanger 4 heats the gas a4 after the purification treatment by the heat of the gas a1 taken out from the porous filter 3, and the heat exchanger 6 similarly heats the gas a4 by the heat of the gas a2 on the downstream side of the COS converter 5, so that the gas a4 can be finally heated to a temperature (about 300 ℃) suitable for feeding to the above-mentioned gas turbine or the like by combining the heat exchanger 4 and the heat exchanger 6.

In this case, the gas a1 is deprived of heat in the heat exchanger 4, thereby cooling it to, for example, about 250 ℃, and therefore the temperature condition of the COS converter 5 is also reduced to about 250 ℃.However, according to the configuration of fig. 7, the temperature condition of the COS converter 5 is about 150 ℃, and a heater and the like are additionally provided in order to realize the temperature condition, so that the present example can achieve the miniaturization of the apparatus and the reduction of the running cost, and also can improve the conversion rate of COS, as compared with the configuration of fig. 7.

In this case, since the gas temperature at the outlet of the heat exchanger 4 reaches a high temperature of about 250 ℃, solid particles of ammonium chloride generated by the reaction between ammonia and hydrogen chloride can be suppressed, and the solid particles can be reliably prevented from adhering to the catalyst of the COS converter 5.

In this case, for example, when a catalyst composed of the simple substance titanium oxide is used as the COS conversion catalyst, it is understood from fig. 6 that a high conversion rate of about 90% can be achieved.

In this case, the heat transfer area required for the heat exchanger 4 was 1626m²The heat transfer area required for the heat exchanger 6 was 636m²The total heat transfer area of the heat engine is still 2262m²And therefore much smaller than the total heat transfer area constituted by fig. 7.

Example 3

Example 3 is explained below. Fig. 4 shows the configuration of the main pretreatment unit in the gas purification apparatus of this example. The main structure of this example is also shown in fig. 7, and the case is shown in fig. 5 (c). The same elements as in examples 1 and 2 are denoted by the same reference numerals, and redundant description thereof is omitted.

The present example omits the heat exchanger 6 at the downstream side of the COS converter 5, and the heat exchanger 4 is provided at the upstream side of the COS converter 5, and only heat is recovered from the gas at the upstream side of the COS converter 5 and used to heat the gas a4 treated in the desulfurization tower 21.

That is, the heat exchanger 4 in this case heats the gas a4 after the purification treatment by using the heat of the gas a1 extracted from the porous filter 3, thereby heating the gas a4 to a temperature (about 300 ℃) suitable for feeding into the above-mentioned gas turbine or the like.

In this case, the gas a1 is deprived of heat in the heat exchanger 4 and is cooled to about 177 ℃, so that the temperature condition of the COS converter 5 is also reduced to about 177 ℃. However, according to the configuration of fig. 7, the temperature condition of the COS converter 5 is about 150 ℃, and a heater and the like are additionally provided in order to realize the temperature condition, so that the present example can achieve the miniaturization of the apparatus and the reduction of the running cost, and also can improve the conversion rate of COS, as compared with the configuration of fig. 7.

In this case, for example, when a catalyst composed of the above simple substance titanium oxide is used as the COS conversion catalyst, it is understood from fig. 6 that a high conversion rate of about 85% can be achieved.

In this case, the heat transfer area required for the heat exchanger 4 was 2262m²The total heat transfer area of the heat engine is still 2262m²And therefore much smaller than the total heat transfer area constituted by fig. 7.

In addition, this example is particularly effective in the case where the amount of solid particles of ammonium chloride generated by the reaction of ammonia and hydrogen chloride is small, but even in the case where the amount of solid particles of ammoniumchloride is large, the catalyst of the COS converter 5 is formed into, for example, a honeycomb shape to have a structure that is difficult to be clogged by the adhesion of solid particles, and thus the problem of the adhesion of solid particles can be coped with.

In addition, the present invention is not limited to the above-described exemplary embodiments, and various embodiments are possible. For example, a cooler for cooling the washing liquid of the washing tower may be provided as necessary to significantly lower the temperature of the gas, and a dust removing device such as a porous filter or the like may be provided on the downstream side of the washing tower to remove ammonium chloride fumes (ultra fine solid particles) generated as the synthesis gas is cooled by the dust removing device.

Further, it is difficult to remove ammonium chloride fumes by gas-liquid contact in a scrubber or absorption treatment in a desulfurizer, and once ammonium chloride fumes pass, it not only causes a problem of corrosion of the material of a gas turbine, but also it is thermally decomposed by combustion and discharged into the atmosphere as harmful substances (nitrogen-containing compounds, chlorine-containing compounds, and the like), and therefore, it is also preferable to remove impurities such as hydrogen chloride and ammonia at the upstream side.

In the present invention, it is needless to say that the desulfurization treatment (recovery of gypsum from the removed hydrogen sulfide) is not performed by the limestone-gypsum method, but the elemental sulfur may be recovered from the sulfur-containing component (hydrogen sulfide) absorbed in the desulfurization tower.

The gas purification device of the invention comprises a washing tower and a converter, wherein the washing tower is used for washing the synthetic gas by contacting the synthetic gas with a washing liquid in a gas-liquid manner before the synthetic gas is introduced into a rubber sulfur tower, and the converter is used for converting carbonyl sulfide in the synthetic gas into hydrogen sulfide at the upstream of the washing tower.

Therefore, the finally obtained gas is a clean gas which could not be achieved in the past because a considerable amount of impurities such as chlorine-containing compounds are absorbed and removed together with sulfur-containing compounds including carbonyl sulfide and hydrogen sulfide, and the problem that impurities such as sulfur-containing compounds and chlorine-containing compounds remain in the gas is solved.

Further, in the present invention, the converter for carbonyl sulfide is disposed on the upstream side (high temperature side) of the scrubber, and therefore, the gas discharged from the scrubber can be directly introduced into the desulfurization tower at its current temperature, as compared with the case of being disposed on the downstream side of the scrubber, so that all the devices corresponding to the heat exchanger 103, the heater 104 and the cooler 106 shown in fig. 7 may be unnecessary, and the heat energy necessary in the heater 104 and the coolant (industrial water or the like) in the cooler 106 may also be unnecessary.

That is, if the main part in this example is constituted as followsIn the same view as fig. 7, for example, the apparatus is configured as shown in fig. 5(a), (b), and (c), and in this case, the heat engine can be operated by an extremely simple facility by providing only the heat exchanger 6 or the heat exchanger 4, and the operating cost is low. In this case, assuming that the temperature conditions of the gas inlet and outlet of the scrubbing or desulfurization tower are the same as those shown in FIG. 7, the total heat transfer area of the heat exchanger is 2262m in each case²This area is larger than that in the constitution of FIG. 7 (total heat transfer area 6629 m)²) Much smaller.

In addition, the gas a1 introduced into the COS converter of the present invention contains much moisture compared to the gas Q2 introduced into the COS converter 105 of fig. 7, and thus, it is not necessary to exclusively supply the steam QW as shown in fig. 7.

Thus, according to the present invention, the apparatus used can be made small and the running cost can be significantly reduced.

Moreover, since the operating conditions of both the scrubbing tower and the desulfurizing tower were unchanged, the performance as a purification apparatus (removal rate of sulfur compounds or other impurities) was equivalent to or higher than that of the constitution shown in FIG. 7.

Particularly, in the case where the heat required for heating the synthesis gas after being treated by the desulfurization tower is recovered from the synthesis gas on the downstream side of the COS converter instead of the synthesis gas on the upstream side of the COS converter (as in the case of the scheme shown in fig. 5 (a)), the temperature of the gas in the COS converter is the temperature of the gas before the treatment, for example, as high as about 420 ℃. In this case, since the temperature of the gas introduced into the COS converter reaches a high temperature of about 420 ℃, the ammonium chloride generated by the reaction of ammonia and hydrogen chloride is prevented from becoming solid particles, and the solid particles can be reliably prevented from adhering to the catalyst in the COS converter.

In addition, in the case where the heat required for heating the synthesis gas after being treated by the desulfurization tower is recovered from the synthesis gas at both the downstream side and the upstream side of the COS converter (as in the case of the scheme shown in fig. 5 (b)), the gas temperature in the COS converter is slightly lower than the gas temperature before the treatment, but is still as high as about 250 ℃, so that the conversion rate of COS is still sufficiently high, and as a result, the removal rate of COS is still significantly higher than that obtained by the configuration shown in fig. 7. In this case, since the temperature of the gas introduced into the COS converter reaches a high temperature of about 250 ℃, the ammonium chloride generated by the reaction of ammonia and hydrogen chloride is prevented from becoming solid particles, and the solid particles can be reliably prevented from adhering to the catalyst in the COS converter.

In addition, in the gas purification apparatus, as the catalyst of the COS converter, a catalyst composed of titanium oxide in which an additive having a strong affinity for impurities in the synthesis gas is not contained may be used.

Therefore, the problem that the activity of the catalyst is damaged by impurities in the synthesis gas is solved, and the catalyst function can be efficiently performed for a long time even if the COS converter is disposed in front of the washing tower for removing the impurities, thereby further improving the practicability.

Claims

1. Gas purification device for purifying a synthesis gas obtained from the gasification of coal or heavy oil, the device having:

2. The gas cleaning device according to claim 1, wherein a catalyst made of titanium oxide containing no additive having a strong affinity for impurities in said synthesis gas is used as the catalyst filled in said converter for promoting the reaction of said carbonyl sulfide to hydrogen sulfide.

3. The gas cleaning device according to claim 1 or 2, wherein the heat required for heating the synthesis gas treated by the desulfurizing tower is recovered from the synthesis gas on the downstream side of the converter, not from the synthesis gas on the upstream side of the converter.

4. The gas cleaning device according to any one of claims 1 to 3, wherein the heat required for heating the synthesis gas treated in the desulfurizing tower is recovered from the synthesis gas on both downstream and upstream sides of the converter.