JP2013049756A - Method of desulfurizing coke oven gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of desulfurizing a coke oven gas, capable of quickly acquiring the concentration of picric acid-reduced product in a desulfurization system.SOLUTION: The method of desulfurizing a coke oven gas with an alkaline aqueous solution containing a picric acid-reduced product includes: a step Y of repeating a set of a step X-1, a step of X-2, a step of X-3 and a step of X-4 several times to thereby acquire a correlation between the amount of picric acid added to the desulfurization system and the amount of the picric acid-reduced product extracted out of the desulfurization system; and a step Z of determining the concentration of the picric acid-reduced product in the desulfurization system, based on the correlation acquired in the step Y, the amount of picric acid added to the desulfurization system and the amount of the picric acid-reduced product extracted out of the desulfurization system.

Description

  The present invention relates to a method for desulfurizing coke oven gas.

  Conventionally, coke oven gas is generated in the process of producing coke by dry distillation of coal. Since this coke oven gas contains hydrogen sulfide derived from sulfur contained in coal, if used as fuel, sulfur oxide (SOx) derived from hydrogen sulfide is generated, which affects the environment. It becomes. For this reason, in order to use coke oven gas as fuel, it is necessary to remove hydrogen sulfide before combustion.

As the above desulfurization method, NH ₄ OH as an absorbent and an alkaline aqueous solution (hereinafter also referred to as “absorption liquid”) containing picric acid as a desulfurization catalyst are brought into contact with a coke oven gas, and hydrogen sulfide is converted into ammonium hydrogen sulfide. A method of absorbing as NH ₄ SH and oxidizing this ammonium hydrogen sulfide with picric acid to convert it to sulfur is widely used.

  In the above desulfurization method, part of the generated sulfur and picric acid is deposited as sludge on the filler in the desulfurization tower. For this reason, the pressure loss in the desulfurization tower rises, and an excessive load is applied to the blower that sends the coke oven gas to the desulfurization tower, or the coke oven gas drifts in the desulfurization tower, which may reduce the desulfurization efficiency. .

  In order to suppress the accumulation of sulfur and picric acid in the desulfurization tower, the concentration of sulfur and picric acid in the absorbent may be lowered. For that purpose, the excessive addition of picric acid may be suppressed. On the other hand, if the picric acid concentration in the absorbing solution is lowered more than necessary, the desulfurization efficiency is lowered. Therefore, it is required to always maintain the picric acid concentration in the absorbing solution at an appropriate value.

  Conventionally, the amount of picric acid added to the absorbent has been adjusted by the concentration of hydrogen sulfide at the exit of the desulfurization tower and the result of component analysis of coal charged into the coke oven. However, since the absorbing solution is extracted outside the desulfurization system, for example, when separating and recovering sulfur deposited in the regeneration tower, the above-described method of adding picric acid has an appropriate value for the picric acid concentration in the absorbing solution. There is a high risk of disengagement.

  Conventionally, there exists a coke oven gas desulfurization method in which an alkaline aqueous solution having an average droplet diameter of 5 mm or more is sprayed at the top of the desulfurization tower based on the pressure loss measurement result of the coke oven gas in the desulfurization tower (for example, Patent Documents). 1).

  The coke oven gas desulfurization method described in Patent Document 1 reduces the contact efficiency between the absorption liquid and the coke oven gas by increasing the spray droplet diameter of the absorption liquid, and the sulfur in the packed bed at the top of the desulfurization tower. In addition, it is intended to prevent the accumulation of local sulfur sludge in the packed bed at the top of the desulfurization tower by the effect of cleaning the packed bed with large-diameter absorbing liquid droplets.

Japanese Patent Laid-Open No. 2001-271074

  However, in the coke oven gas desulfurization method described in Patent Document 1, since the spray droplet diameter is adjusted based on the pressure loss measurement result of the coke oven gas in the desulfurization tower, a certain amount of sulfur is deposited, The spray droplet diameter is adjusted after the loss starts to increase. Therefore, there is a problem that the operation is continued with the pressure loss increased until the pressure loss becomes an appropriate value after the spray droplet diameter is adjusted. Moreover, since the pressure loss generally increases at an accelerated rate, even if the spray droplet diameter is adjusted after the pressure loss starts to increase, the suppression of sulfur generation and the effect of cleaning the packed bed cannot be caught up. There's a problem.

  The concentration of picric acid itself can generally be measured using an ultraviolet-visible absorptiometer. However, even if the concentration of picric acid in the absorbing solution used for desulfurization of coke oven gas is measured with an ultraviolet-visible absorptiometer, only a trace amount is observed. This is because most of picric acid is present as a reduction product in the absorbing solution. In order to efficiently perform the desulfurization of the coke oven gas, it is desirable to quickly know the concentration of the picric acid reduction product in the desulfurization system. Therefore, development of a method capable of quickly obtaining the concentration of the picric acid reduction product in the desulfurization system has been eagerly desired.

  This invention is made | formed in view of the subject mentioned above, The objective is to provide the desulfurization method of the coke oven gas which can acquire the density | concentration of the picric acid reduction product in a desulfurization system quickly. is there.

In order to achieve the above object, the present invention provides the following.
A coke oven gas desulfurization method for desulfurizing a coke oven gas with an alkaline aqueous solution containing a picric acid reduction product,
Step X-1 for extracting the absorbing liquid out of the desulfurization system,
Step X-2 for determining the concentration of the picric acid reduction product in the absorption liquid extracted outside the desulfurization system in Step X-1.
Step X-3 for determining the amount of the picric acid reduction product extracted out of the desulfurization system based on the concentration of the picric acid reduction product determined in Step X-2 and the amount of the extracted absorbent.
Step X-4 of adding an amount of picric acid based on a rule of thumb into the desulfurization system,
Correlation between the amount of picric acid added in the desulfurization system and the amount of picric acid reduction product extracted out of the desulfurization system is expressed as the step X-1, the step X-2, the step X-3, and the Step Y obtained by repeating Step X-4 as a set multiple times, and
A step of determining the concentration of the picric acid reduction product in the desulfurization system based on the correlation obtained in the step Y, the amount of picric acid added to the desulfurization system, and the amount of the absorption liquid extracted outside the desulfurization system. A method for desulfurizing coke oven gas, comprising Z.

  The present inventors have found that the amount of picric acid added in the desulfurization system correlates with the amount of picric acid reduction product extracted out of the desulfurization system. If this correlation is used, the concentration of the picric acid reduction product in the desulfurization system can be obtained (estimated) from the amount of picric acid added to the desulfurization system and the amount of absorption liquid withdrawn outside the desulfurization system. I came up with what I can do.

  According to the above-described configuration, the correlation between the amount of picric acid added into the desulfurization system and the amount of the picric acid reduction product extracted out of the desulfurization system is expressed as the step X-1, the step X-2, and the step X. -3 and if the process X-4 is obtained by repeating a plurality of times as a set (if the process Y is performed), the correlation obtained by the process Y is added to the desulfurization system. The concentration of the picric acid reduction product in the desulfurization system can be determined (step Z) based on the amount of picric acid to be removed and the amount of the absorption liquid extracted outside the desulfurization system. That is, according to the above configuration, it is possible to know the concentration of the picric acid reduction product in the desulfurization system without actually sampling the absorption liquid in the desulfurization system and measuring the concentration of the picric acid reduction product. . As a result, the concentration of the picric acid reduction product in the desulfurization system can be acquired quickly.

In the above configuration, the step X-2 includes
A process of extracting organic matter from the extracted absorbent,
A process of performing elemental analysis on the extract,
Performing infrared spectroscopic analysis on the extract; and
It is preferable to include a step of obtaining a picric acid reduction product concentration in the absorbing solution based on the result of the elemental analysis and the result of the infrared spectroscopic analysis.

  As described above, most of picric acid is present as a reduction product in the absorbing solution. However, there is currently no known method for measuring the concentration of picric acid reduction product.

  The absorption liquid used for desulfurization of coke oven gas includes picric acid reduction products (including a very small amount of picric acid itself), tar-derived aliphatic hydrocarbons contained in coke oven gas, and tar-derived aromatic carbonization. Hydrogen, ammonium thiocyanate, elemental sulfur, and water-soluble substances are included.

  According to the above configuration, a substance containing an organic substance as a main component (hereinafter simply referred to as “organic substance” unless otherwise specified) is extracted from the absorption liquid, and elemental analysis is performed on the extract. Infrared spectroscopic analysis is performed, and the concentration of the picric acid reduction product (including a very small amount of picric acid itself) can be obtained based on the result of elemental analysis and the result of infrared spectroscopic analysis. For example, (a) the concentration of the whole organic matter in the absorbing solution is specified from the weight of the organic matter extracted from the absorbing solution, (b) the concentration of free sulfur is specified by elemental analysis, and (c) the free concentration is determined by infrared spectroscopic analysis. The concentration of substances other than sulfur and picric acid is specified, and (d) the concentration of free sulfur and the concentration of substances other than picric acid are subtracted from the concentration of the whole organic matter, thereby reducing the picric acid reduction product (very Concentration) (including a small amount of picric acid itself).

In the above configuration, the step X-2 includes
Step A for performing ultraviolet absorption analysis on the extracted absorption liquid,
Step B for extracting organic substances from the absorption liquid after performing ultraviolet absorption analysis,
Step C for performing ultraviolet absorption analysis on the absorbing solution after extracting the organic matter,
Process D for performing elemental analysis on the extract,
Step E for performing infrared spectroscopic analysis on the extract,
Step F for obtaining the extraction rate of the picric acid reduction product in the organic substance based on the result of the ultraviolet absorption analysis in the step A and the result of the ultraviolet absorption analysis in the step C,
Based on the result of the elemental analysis in the step D and the result of the infrared spectroscopic analysis in the step E, the step G of obtaining the picric acid reduction product concentration before conversion of the extraction rate, and
It is preferable to include the step H of obtaining the picric acid reduction product concentration from the picric acid reduction product concentration before conversion of the extraction rate obtained in the step G and the extraction rate obtained in the step F.

  When the inventors of the present invention observe the spectrum of the absorbing solution with an ultraviolet-visible absorptiometer, the spectrum of picric acid itself is not observed, but a spectrum having a peak around 475 nm is observed, and the absorbance at 475 nm is reduced by picric acid reduction. It was found to correlate with the concentration of product.

According to the above configuration, ultraviolet absorption analysis is performed on the extracted absorption liquid (step A), organic substances are extracted from the absorption liquid after the ultraviolet absorption analysis is performed (process B), and absorption after the organic substances are extracted. The solution is subjected to ultraviolet absorption analysis (Step C).
Utilizing the fact that the absorbance at 475 nm of the absorbing solution correlates with the concentration of the picric acid reduction product, based on the result of the ultraviolet absorption analysis in the step A and the result of the ultraviolet absorption analysis in the step C, picrine in the organic matter The extraction rate of the acid reduction product is obtained (Step F).
In addition, the elemental analysis is performed on the extract (step D), the infrared spectroscopic analysis is performed on the extract (step E), and based on the results of the elemental analysis and the infrared spectroscopic analysis, The picric acid reduction product concentration before conversion based on the extraction rate is obtained (step G). For example, (a) the concentration of the whole organic matter in the absorbing solution is specified from the weight of the organic matter extracted from the absorbing solution, (b) the concentration of free sulfur is specified by elemental analysis, and (c) the free concentration is determined by infrared spectroscopic analysis. Identify the concentration of substances other than sulfur and picric acid reduction products, and (d) extract by subtracting the concentration of free sulfur and the concentration of substances other than picric acid reduction products from the concentration of the entire organic matter. The concentration of the picric acid reduction product before conversion by rate is determined.
Then, the picric acid reduction product concentration obtained in the step G and before the extraction rate conversion and the extraction rate obtained in the step F are obtained (step H).
Thus, according to the said structure, the more exact picric-acid reduction product density | concentration which considered the picric-acid reduction product which was not extracted in the process of extracting organic substance (remaining in the water phase) can be obtained. .

  In the said structure, it is preferable to include the process of adjusting the addition amount of picric acid based on the picric acid reduction product density | concentration in the desulfurization system calculated | required by the said process Z. FIG.

  According to the said structure, based on the picric acid reduction product density | concentration in the desulfurization system calculated | required by the said process Z, the addition amount of picric acid is adjusted. Therefore, it is possible to reduce the time lag from when the absorbing solution is extracted outside the desulfurization system until the concentration of the picric acid reduction product is obtained. As a result, the concentration of the picric acid reduction product in the absorption liquid can be adjusted within a desired fixed range. Thereby, the sulfur production | generation in a desulfurization tower can be suppressed and it can contribute to the stable driving | operation of a desulfurization tower.

  According to the present invention, the concentration of the picric acid reduction product in the desulfurization system can be obtained quickly.

It is a distribution diagram showing typically an example of the coke oven gas desulfurization equipment concerning this embodiment. It is a flowchart which shows the procedure which extracts the organic substance in an absorption liquid. It is a flowchart which shows the fixed_quantity | quantitative_assay procedure of an aliphatic hydrocarbon. It is a flowchart which shows the fixed_quantity | quantitative_assay procedure of ammonium thiocyanate. It is a figure which shows an example of the absorption spectrum obtained in the ultraviolet absorption analysis before a solid-phase extraction, and the absorption spectrum obtained in the ultraviolet absorption analysis after a solid-phase extraction. It is a figure which shows the infrared absorption spectrum of the extract which added octadecane. It is a calibration curve for quantifying aliphatic hydrocarbons. It is a figure which shows the infrared absorption spectrum of the extract which added ammonium thiocyanate. It is a calibration curve for quantifying ammonium thiocyanate. It is a figure which shows the graph of the relationship between the picric acid reduction product density | concentration (picric acid reduction product density | concentration after extraction rate conversion) measured in Examples 1-9, and the amount of added picric acid. It is a figure which shows the graph of the relationship between the picric acid reduction product density | concentration before the extraction rate conversion in Examples 1-9, and the amount of added picric acid. It is a figure which shows the graph obtained by plotting about 1-9 the amount of picric acid extracted outside the desulfurization system as the x-axis and the amount of picric acid added into the desulfurization system as the y-axis.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system diagram schematically showing an example of a coke oven gas desulfurization facility according to the present embodiment. The coke oven gas desulfurization facility 10 includes a desulfurization tower 12, a regeneration tower 14, and a desulfurization waste liquid treatment apparatus 18. In the coke oven gas desulfurization facility 10, an alkaline aqueous solution containing NH ₄ OH as an absorbent and a picric acid reduction product (including a small amount of picric acid itself) as a desulfurization catalyst is used as an absorbent. The

In the desulfurization tower 12, the absorbing liquid is sprayed from the top of the desulfurization tower 12. When the coke oven gas COG 1 is introduced from below the desulfurization tower 12, the surface of the filler 22 filled in the desulfurization tower 12 is Hydrogen sulfide and hydrogen cyanide in the coke oven gas COG1 are absorbed and removed by the absorption liquid, and discharged from the upper part to the next process as desulfurized coke oven gas COG2. At this time, hydrogen sulfide is absorbed as ammonium hydrosulfide (NH ₄ SH), and hydrogen cyanide is absorbed as ammonium thiocyanate (NH ₄ SCN). Further, picric acid as a catalyst is reduced, and a nitro group (—NO ₂ ) is converted into a nitroso group (—NO) or a hydroxylamino group (—NHOH).

  The absorbing liquid that absorbs hydrogen sulfide and hydrogen cyanide and contains the picric acid reduction product is recovered from the bottom of the desulfurization tower 12 and sent to the regeneration tower 14 via the pipe 13.

  A sampling pipe S <b> 1 is connected to the pipe 13, and the absorption liquid recovered from the bottom of the desulfurization tower 12 can be sampled.

  In the regeneration tower 14, air A is introduced from the bottom of the tower, and hydrogen sulfide absorbed in the absorbing liquid is precipitated as free sulfur in the liquid. Also, the picric acid reduction product is oxidized by contacting with the air A introduced from the bottom of the column, and the alkali is regenerated and sent again to the desulfurization column 12 through the pipe 16. Thereby, both the catalyst and the alkali are reused.

  A sampling pipe S3 is connected to the pipe 16, and the absorbing liquid sent from the regeneration tower 14 to the desulfurization tower 12 can be sampled. Further, the pipe 16 is connected with a catalyst addition pipe S2, and picric acid Pi can be added to the absorbing solution.

  Further, a pipe 17 is connected to the regeneration tower 14, and in order to prevent the deposits from accumulating in the regeneration tower 14, the absorption liquid is extracted from the top together with the precipitates such as free sulfur and ammonium thiocyanate. After the free sulfur and the like are separated, they are sent to the desulfurization waste liquid treatment device 18.

In the desulfurization method of the present embodiment, as described above, a part of the absorbing liquid is extracted out of the desulfurization system. Further, when picric acid as a catalyst is reduced, a nitro group (—NO ₂ ) is converted into a nitroso group (—NO) or a hydroxylamino group (—NHOH), but is further reduced to an amino group (— When converted to NH ₂ ), it becomes difficult to regenerate and the catalytic action is lost. In order to compensate for this, a part of the absorption liquid circulating in the desulfurization system is periodically extracted and replenished with new absorption liquid. As a result, the concentration of picric acid in the absorbent in the desulfurization system changes.

  In the desulfurization method according to the present embodiment, picric acid Pi is added in the middle of the pipe 16 that feeds the absorbing liquid from the regeneration tower 14 to the desulfurization tower 12. At this time, the addition amount of picric acid Pi is determined based on an empirical rule until a correlation between the amount of picric acid added into the desulfurization system and the amount of picric acid reduction product extracted out of the desulfurization system is obtained. (Step X-4). After the correlation between the amount of picric acid added in the desulfurization system and the amount of the picric acid reduction product extracted outside the desulfurization system is obtained, the obtained correlation and the picrin added in the desulfurization system are obtained. Based on the amount of acid and the amount of absorption liquid extracted outside the desulfurization system, the concentration of the picric acid reduction product in the desulfurization system is determined (step Z), and the reduction of picric acid in the desulfurization system determined in the step Z is performed. It is determined based on the object concentration. Even after the correlation between the amount of picric acid added into the desulfurization system and the amount of the picric acid reduction product extracted outside the desulfurization system was obtained, the addition amount of picric acid Pi was determined based on empirical rules. May be. Even in this case, since the concentration of the reduction product of picric acid in the desulfurization system is required, for example, the amount of the picric acid reduction product in the absorption liquid is adjusted by adjusting the amount of the absorption liquid drawn out of the desulfurization system. This is because the substance concentration can be adjusted within a desired fixed range.

  Hereinafter, first, a method for obtaining a correlation between the amount of picric acid added into the desulfurization system and the amount of picric acid reduction product extracted out of the desulfurization system will be described. The correlation can be obtained while performing the operation (desulfurization of coke oven gas).

  First, the absorbent is extracted out of the desulfurization system (step X-1). This process X-1 is performed from the piping 17. Note that the absorbing liquid may be extracted outside the desulfurization system using two or more of the pipe 17, the sampling pipe S1, and the sampling pipe S3.

  Next, the concentration of the picric acid reduction product in the absorbent extracted from the desulfurization system in step X-1 is determined (step X-2). The concentration of the picric acid reduction product in the absorption liquid extracted outside the desulfurization system in step X-1 may be the concentration in the absorption liquid extracted from the pipe 17, and may be the sampling pipe S1 or the sampling pipe. You may employ | adopt the density | concentration in the absorption liquid sampled by S3. However, since the form (oxidation degree) of the compound differs depending on the sampling location, there may be a difference in the concentration of the picric acid reduction product. Therefore, it is preferable to fix the sampling location at one location. The method for obtaining the concentration of the picric acid reduction product in the absorbent extracted outside the desulfurization system will be described in detail later.

Next, the amount of the picric acid reduction product extracted out of the desulfurization system is determined based on the concentration of the picric acid reduction product determined in the step X-2 and the amount of the absorbed liquid extracted (step X-3). ). Specifically, the amount of the picric acid reduction product extracted out of the desulfurization system is determined by the following formula.
(Amount of picric acid reduction product extracted out of desulfurization system) = (concentration of picric acid reduction product determined in step X-2) × (amount of extracted absorption liquid)

  On the other hand, an amount of picric acid based on an empirical rule is added to the desulfurization system (step X-4). The amount of picric acid added in the step X-4 is determined empirically from values such as charging coal properties (hydrogen sulfide concentration), desulfurization efficiency, oxidation-reduction potential of the absorbent, and the like.

  Next, the amount of picric acid added to the desulfurization system and desulfurization are repeated by repeating the step X-1, the step X-2, the step X-3, and the step X-4 multiple times as one set. A correlation with the amount of picric acid reduction product extracted out of the system is obtained (step Y). The process X-1, the process X-2, the process X-3, and the process X-4 can be repeated, for example, in January as one cycle. For example, a correlation equation can be obtained from data obtained by repeating this multiple times.

Next, a specific example of the method for measuring the concentration of the picric acid reduction product in the absorbing solution (specific example of the step X-2) will be described.
The absorption liquid used for desulfurization of coke oven gas (hereinafter also referred to as desulfurization liquid) includes picric acid reduction product (hereinafter also referred to as picric acid reduction product F), and fat derived from tar contained in coke oven gas. Aromatic hydrocarbon (hereinafter also referred to as aliphatic hydrocarbon D), aromatic hydrocarbon derived from the tar (hereinafter also referred to as aromatic hydrocarbon E), ammonium thiocyanate (hereinafter also referred to as ammonium thiocyanate C), simple substance Sulfur (hereinafter also referred to as simple sulfur B) and water-soluble substances are included. That is, the desulfurization liquid contains B to F and a water-soluble substance.

  In the method for measuring the concentration of the picric acid reduction product in the absorption liquid, first, ultraviolet absorption analysis is performed on the sampled absorption liquid (step A). Next, only the organic substance is recovered using the solid phase extraction cartridge (step B). Thereby, a water-soluble substance is removed among said B-F and a water-soluble substance. Next, this is vacuum-dried to obtain an extract (hereinafter also referred to as extract A). At this time, the aromatic hydrocarbon E derived from tar having a low boiling point and high volatility is removed. Therefore, the extract A includes the BD and the F. However, among the picric acid reduction product F, the picric acid reduction product that has been reduced further has a higher hydrophilicity, and therefore a part thereof has not been extracted (move to the aqueous phase).

  Next, ultraviolet absorption analysis is performed with respect to the absorption liquid after extracting organic substance (process C). Absorbance at 475 nm correlates with the concentration of picric acid reduction product. Therefore, the result of the ultraviolet absorption analysis in the step A (that is, the absorbance based on the total picric acid reduction product in the sample) and the result of the ultraviolet absorption analysis in the step C (that is, the sample was not extracted by the step B). The extraction rate of the picric acid reduction product in the organic substance is obtained based on the absorbance based on the picric acid reduction product (step F).

Next, the concentration of the picric acid reduction product F before conversion based on the extraction rate is determined by the following method.
(I) The extract A is weighed, and the concentration (mg / L) of the extract A in the desulfurization liquid is determined from the amount of the desulfurization liquid passed through the solid-phase extraction cartridge and the weight of the extract A.
(Ii) Elemental analysis of the extract A is performed using an elemental analyzer, and the concentration (mg / L) of elemental sulfur B is obtained (step D).
(Iii) A tablet containing the extract A is prepared, and the concentration (mg / L) of the aliphatic hydrocarbon D contained in the extract A is determined from the infrared absorption spectrum by FT-IR (Fourier transform infrared spectrophotometer). Obtain (Step E).
(Iv) A tablet containing the extract A is prepared, and the concentration (mg / L) of ammonium thiocyanate C contained in the extract A is determined from the infrared absorption spectrum by FT-IR (Fourier transform infrared spectrophotometer). (Process E).
(V) Based on the results obtained in the above (i) to (iv), the concentration of the picric acid reduction product F before conversion by the extraction rate is obtained by the following calculation formula (step G).
(Concentration of picric acid reduction product F before conversion by extraction rate) = (concentration of extract A) − (concentration of elemental sulfur B) − (concentration of aliphatic hydrocarbon D) − (concentration of ammonium thiocyanate C) )

Finally, the picric acid reduction product concentration is obtained from the concentration of the picric acid reduction product F before conversion at the extraction rate obtained in the step G and the extraction rate obtained in the step F (step H).
This makes it possible to obtain a more accurate picric acid reduction product concentration in consideration of the picric acid reduction product that has not been extracted (remaining in the aqueous phase) in the step of extracting the organic substance (step B).

Hereinafter, the measurement method will be described in detail.
FIG. 2 is a flowchart showing a procedure for extracting an organic substance in the absorbing solution.
First, in step S11, the desulfurization liquid is sampled from the sampling pipe S3. Next, in step S12, 150 ml of desulfurization liquid is diluted 20 times with pure water to prepare a sample.

  Next, in step S13, the sample is subjected to ultraviolet absorption analysis (step A). This gives an absorbance at 475 nm.

  Next, in step S14, the sample is passed through the solid phase extraction cartridge to adsorb the organic matter. At this time, the sample that has passed through the solid-phase extraction cartridge is collected. A conventionally known cartridge can be used as the solid phase extraction cartridge. The filler used in the solid phase extraction cartridge is not particularly limited as long as it can adsorb organic substances in the desulfurization liquid, and examples thereof include polystyrene resins.

  Next, in step S15, pure water is poured into the solid phase extraction cartridge and washed with water to remove the water-soluble substance from the solid phase extraction cartridge.

  Next, in step S16, the sample once passed through the solid-phase extraction cartridge is passed again, and the organic matter that has not been adsorbed in the first passage is adsorbed.

  Next, in step S17, ultraviolet absorption analysis is performed on the sample after passing through the solid-phase extraction cartridge (step C). This gives an absorbance at 475 nm.

  Next, in step S18, 150 ml of methanol is passed through the solid-phase extraction cartridge, and the adsorbed organic matter is desorbed by elution.

  Next, the desorbed liquid is concentrated with a rotary evaporator (step S19), and then the concentrate is dried with a vacuum dryer at 70 ° C. for 48 hours (step S20). Thereby, the extract A is obtained.

  Here, the amount of the extract A obtained by the above extraction procedure is weighed, and the concentration of the extract A is calculated. Then, the elemental analysis of the extract A is performed using an elemental analyzer, and the concentration (mg / L) of elemental sulfur B is obtained. In addition, the quantification of the aliphatic hydrocarbon and the quantification of ammonium thiocyanate are performed according to the following procedure (see FIGS. 3 and 4).

FIG. 3 is a flowchart showing a procedure for quantifying aliphatic hydrocarbons.
First, 10 g of potassium bromide (KBr) and 2.12 mg of potassium hexacyanoferrate (II) (K ₄ [Fe (CN) ₆ ]) as an internal standard are dissolved in 300 ml of deionized water (step S21). ).

  Next, it is concentrated by an evaporator and further dried by a vacuum dryer (at 60 ° C. for 24 hours) to remove moisture (step S22).

  Next, KBr with internal standard prepared in steps S21 and S22: 1 g, extract A extracted in the above extraction procedure: 10 mg, and a predetermined amount of octadecane dissolved in acetone are mixed in an agate mortar (step S23).

  Next, the mixture is dried in a vacuum dryer (at 60 ° C. for 24 hours) to remove acetone (step S24), and is formed into a tablet (step S25).

  Next, FT-IR measurement is performed using the molded tablet (step S26). At this time, the area ratio ((CH bond area) / (CN triple bond area)) between the absorption spectrum derived from the CH bond of aliphatic hydrocarbon D and the absorption spectrum derived from the CN triple bond of the internal standard substance. Ask for.

  Next, the compounding quantity of octadecane is changed, a tablet is shape | molded similarly to the above, and FT-IR measurement is performed (step S27). At this time, similarly to step S26, the area ratio between the absorption spectrum derived from the CH bond of the aliphatic hydrocarbon D and the absorption spectrum derived from the CN triple bond of the internal standard substance is obtained. In addition, it is preferable to perform step S27 several times, changing the compounding quantity of octadecane from a viewpoint of the accuracy of the calibration curve produced in the following step S28.

  Next, a calibration curve is created with the added amount of octadecane as the x-axis and the area ratio as the y-axis (step S28).

  Next, the ratio of the aliphatic hydrocarbon D in the extract A is obtained from the created calibration curve, and the concentration of the aliphatic hydrocarbon D in the desulfurization liquid is calculated from this ratio (step S29). Detailed calculation methods will be described in the examples.

FIG. 4 is a flowchart showing a procedure for quantifying ammonium thiocyanate.
In the ammonium thiocyanate quantitative procedure described below, an aliphatic thiocyanate was used in place of the octadecane (see step S23) mixed in the aliphatic hydrocarbon quantitative procedure (see FIG. 3). The concentration of ammonium thiocyanate C is calculated in the same procedure as the hydrocarbon determination procedure.

First, 10 g of KBr and 2.12 mg of K ₄ [Fe (CN) ₆ ] as an internal standard are dissolved in 300 ml of deionized water (step S31).

  Next, it is concentrated by an evaporator and further dried by a vacuum dryer (at 60 ° C. for 24 hours) to remove moisture (step S32).

  Next, KBr with an internal standard prepared in steps S31 and S32: 1 g, 10 mg of extract A extracted in the above extraction procedure, and ammonium thiocyanate dissolved in a predetermined amount in acetone are mixed in an agate mortar ( Step S33).

  Next, the mixture is dried in a vacuum dryer (at 60 ° C. for 24 hours) to remove acetone (step S34), and is formed into a tablet (step S35).

  Next, FT-IR measurement is performed using the molded tablet (step S36). At this time, the area ratio between the absorption spectrum derived from the CN double bond of ammonium thiocyanate C and the absorption spectrum derived from the CN triple bond of the internal standard substance ((area of CN double bond) / (CN triple bond Area)).

  Next, the amount of ammonium thiocyanate is changed, and tablets are formed in the same manner as described above, and FT-IR measurement is performed (step S37). At this time, similarly to step S36, the area ratio between the absorption spectrum derived from the CN double bond of ammonium thiocyanate C and the absorption spectrum derived from the CN triple bond of the internal standard substance is obtained. In addition, it is preferable to perform step S37 several times, changing the compounding quantity of ammonium thiocyanate from a viewpoint of the accuracy of the calibration curve produced in the following step S38.

  Next, a calibration curve is created with the addition amount of ammonium thiocyanate as the x-axis and the area ratio as the y-axis (step S38).

  Next, the ratio of ammonium thiocyanate C in the extract A is obtained from the prepared calibration curve, and the concentration of ammonium thiocyanate C in the desulfurization solution is calculated from this ratio (step S39). Detailed calculation methods will be described in the examples.

Based on the concentration of the obtained extract A, the concentration of elemental sulfur B, the concentration of aliphatic hydrocarbon D, and the concentration of ammonium thiocyanate C, the concentration of the picric acid reduction product F before conversion by the extraction rate is determined. It calculates | requires with the following formula (process G).
(Concentration of picric acid reduction product F before conversion by extraction rate) = (concentration of extract A) − (concentration of elemental sulfur B) − (concentration of aliphatic hydrocarbon D) − (concentration of ammonium thiocyanate C) )

On the other hand, based on the result of the ultraviolet absorption analysis in the step A (step S13) and the result of the ultraviolet absorption analysis in the step C (step S17), the extraction rate of the picric acid reduction product in the organic matter is obtained (step F). ).
Specifically, the extraction rate of the picric acid reduction product in the organic substance is obtained by the following formula.
(Extraction rate (%)) = (1 − ((absorbance after extraction) / (absorbance before extraction))) × 100

Finally, the picric acid reduction product concentration is obtained from the concentration of the picric acid reduction product F before conversion at the extraction rate obtained in the step G and the extraction rate obtained in the step F (step H).
(Picric acid reduction product concentration) = (Concentration of picric acid reduction product F before extraction rate conversion) × (100 / (extraction rate (%)))

FIG. 5 shows the absorption spectrum obtained in the ultraviolet absorption analysis before the solid phase extraction (step A, step S13) and the absorption spectrum obtained in the ultraviolet absorption analysis after the solid phase extraction (step C, step S17). It is a figure which shows an example. As shown in FIG. 5, the present inventors have found that the absorbance having a peak near 475 nm correlates with the concentration of the picric acid reduction product. As shown in FIG. 5, a peak remains at 475 nm even after solid phase extraction. This is because part of the picric acid reduction product remains in the aqueous phase in the solid phase extraction.
As described above, according to the method for measuring the concentration of picric acid in the absorption liquid according to the present embodiment, extraction rate conversion is performed and extraction is not performed in the process of extracting organic matter (process B, steps S14 to S16) ( A more accurate picric acid reduction product concentration can be obtained, taking into account the picric acid reduction product (remaining in the aqueous phase).

Then, the amount of picric acid added from the catalyst addition tube S2 (see FIG. 1) is adjusted based on the picric acid reduction product concentration measured by the picric acid concentration measurement method. Specifically, for example, the amount of picric acid added is determined based on the following formula.
(Picric acid addition amount) = (Measured picric acid reduction product concentration) × (Amount of desulfurized liquid extracted)

  As described above, in the desulfurization method according to the present embodiment, the addition amount is adjusted using the picric acid reduction product concentration itself. Therefore, in the coke oven gas desulfurization facility 10, picric acid is excessively added or added. The amount can be prevented from decreasing, and the concentration of the picric acid reduction product in the absorbing solution can be adjusted within a desired fixed range. As a result, sulfur generation in the desulfurization tower 12 can be suppressed, which can contribute to stable operation of the desulfurization tower.

In the embodiment described above, the step A of performing ultraviolet absorption analysis on the extracted absorption liquid and the step C of performing ultraviolet absorption analysis on the absorption liquid after extracting the organic matter are performed to reduce picric acid in the organic matter. The case where the extraction rate of the product was obtained (Step F) and the concentration of the picric acid reduction product in consideration of this extraction rate has been described. However, the present invention is not limited to this example. For example, Step A, Step C, and Step F are not performed, and based on the results of elemental analysis and infrared spectroscopic analysis, picric acid in the absorbing solution is used. The reduction product concentration may be obtained.
In this method, the concentration of the picric acid reduction product before conversion to the extraction rate is estimated as the concentration of the picric acid reduction product in the desulfurization system.

  In the above-described embodiment, the case where the extraction rate is obtained using the absorbance at 475 nm has been described. However, in the step F of the present invention, the reduction of the picric acid reduction product in the organic matter is based on the result of the ultraviolet absorption analysis (step A) before the organic matter extraction and the result of the ultraviolet absorption analysis after the organic matter extraction (step C). If an extraction rate is obtained, it will not be limited to this example. As Step F of the present invention, for example, the extraction rate may be calculated using an integrated value of absorbance within a certain range including 475 nm (for example, 400 to 500 nm). This is because even the absorbance within a certain range including 475 nm correlates with the concentration of the picric acid reduction product. Specifically, ultraviolet absorption analysis was performed on the sampled absorption liquid, an integrated value of absorbance within a certain range including 475 nm (for example, 400 to 500 nm) was obtained (step A), and organic matter was extracted. An ultraviolet absorption analysis is performed on the subsequent absorbing solution to obtain an integrated value of absorbance within a certain range including 475 nm (for example, 400 to 500 nm) (step C), and the integrated value in the step A and the step Based on the integrated value in C, the extraction rate of the picric acid reduction product in the organic substance can be obtained (step F).

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to a following example, unless the summary is exceeded.

  First, the method for measuring the concentration of the picric acid reduction product before conversion of the extraction rate will be described using the following Reference Example 1.

(Reference Example 1)
The absorption liquid (desulfurization liquid) regenerated in the regeneration tower 14 shown in FIG. 1 is sampled from the sampling pipe S3 provided in the pipe 16 sent to the desulfurization tower 12, and the extract A is obtained by the extraction procedure shown in FIG. It was. The product name “Sep-Pak Plus CSP 800 (filler: polystyrene resin, particle size: 75 to 150 μm)” manufactured by Nippon Waters Co., Ltd. was used for the solid phase extraction cartridge. Extract A was weighed to determine the concentration of Extract A in the desulfurization solution. The results are shown in the column “F-1 (inlet)” in Table 1.

<Quantification of aliphatic hydrocarbon D concentration (mg / L)>
Using a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation, product name “FT / IR410”), an infrared absorption spectrum was obtained based on the determination procedure of the aliphatic hydrocarbon shown in FIG. The infrared absorption spectrum was performed four times while changing the amount of octadecane added. The amount of octadecane added in each measurement is 0.00017 mmol, 0.00051 mmol, 0.00085 mmol, and 0.0017 mmol, respectively. The results are shown in FIG.

FIG. 6 is a diagram showing an infrared absorption spectrum of an extract to which octadecane has been added.
As shown in FIG. 6, two large absorption spectra were observed from the extract to which octadecane was added. One is an absorption spectrum derived from a CH bond of an aliphatic hydrocarbon D having two peaks in the vicinity of a wave number of 2900 cm ⁻¹ . The other is observed near the wave number of 2050 cm ⁻¹ and is derived from the absorption spectrum derived from the CN double bond of ammonium thiocyanate (hereinafter also referred to as “CN double bond spectrum”) and from the CN triple bond of the internal standard substance. Absorption spectrum (hereinafter also referred to as “CN triple bond spectrum”). Here, as a result of intensive studies, the present inventors have determined that the spectrum area of the region where the wave number is smaller than the valley position formed between the CN double bond spectrum and the CN triple bond spectrum is the CN triple bond. Assuming that the area of the spectrum of the bond is an area, this area (also referred to as “the area of the virtual CN triple bond spectrum”) has been found to significantly approximate the area of the spectrum of the actual CN triple bond alone. In this example, the area of the virtual CN triple bond spectrum is used, and the area ratio of the absorption spectrum derived from the CH bond of the aliphatic hydrocarbon D and the absorption spectrum derived from the CN triple bond of the internal standard substance ((CH Bond area) / (CN triple bond area)). A calibration curve was prepared by linear approximation using the least square method, with the addition amount of octadecane as the x-axis (horizontal axis) and the obtained area ratio as the y-axis (vertical axis). The prepared calibration curve is shown in FIG.

FIG. 7 is a calibration curve for quantifying aliphatic hydrocarbons.
From the calibration curve, a relational expression y = 1990x + 7.48 was obtained. When y = 0 was substituted in this relational expression, the amount of aliphatic hydrocarbon D was 0.00376 mmol / g-KBr from this absolute value. Here, since the tablet used for the FT-IR measurement is prepared by mixing Extract A: 10 mg and KBr: 1 g, the amount of aliphatic hydrocarbon D in Extract A is 0.376 mmol. / G-extract. Since the molecular weight of octadecane is 254.49, the amount of aliphatic hydrocarbon D in the extract A is 0.0957 g / g-extract. Since the amount of the extract A is 327 mg / L, the amount of the aliphatic hydrocarbon D in the desulfurization liquid is 327 × 0.0957 = 31 mg / L. From the above, the concentration of the aliphatic hydrocarbon D in the desulfurization liquid was obtained.

<Quantification of ammonium thiocyanate C concentration (mg / L)>
Using a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation, product name “FT / IR410”), an infrared absorption spectrum was obtained based on the ammonium thiocyanate quantitative procedure shown in FIG. The infrared absorption spectrum was performed four times while changing the amount of ammonium thiocyanate added. The amount of ammonium thiocyanate added in each measurement is 0.00034 mmol, 0.0010 mmol, 0.0017 mmol, and 0.0034 mmol, respectively. The results are shown in FIG.

FIG. 8 is an infrared absorption spectrum of an extract to which ammonium thiocyanate is added.
From the extract to which ammonium thiocyanate was added, two large absorption spectra were observed as in the extract to which octadecane was added as shown in FIG. In FIG. 8, only the peak in the vicinity of a wave number of 2050 cm ⁻¹ is enlarged and shown.

As shown in FIG. 8, the absorption spectrum observed in the vicinity of a wave number of 2050 cm ⁻¹ has three peaks, the spectrum of the CN double bond of ammonium thiocyanate and the spectrum of the CN triple bond of the internal standard substance. And are overlapping spectra. Here, as a result of intensive studies, the present inventors have determined the spectrum area of the region having a larger wave number than the valley formed between the peak on the higher wave number side and the middle peak among the three peaks. The area of the spectrum of the CN double bond is regarded as the area of the spectrum of the CN triple bond, and the area of the spectrum of the region having a smaller wave number than the valley formed between the middle peak and the peak of the smaller wave number is regarded as the area of the CN triple bond spectrum. For example, it was found that the ratio of both areas remarkably approximates the area ratio between the actual absorption spectrum of only CN double bonds and the actual absorption spectrum of only CN triple bonds. In this example, the area ratio between the absorption spectrum of the CN double bond and the absorption spectrum of the CN triple bond was determined by this method. A calibration curve was prepared by linear approximation using the least square method, with the addition amount of ammonium thiocyanate on the x-axis (horizontal axis) and the obtained area ratio on the y-axis (vertical axis). The created calibration curve is shown in FIG.

FIG. 9 is a calibration curve for quantifying ammonium thiocyanate.
From the calibration curve, a relational expression y = 124x + 0.394 was obtained. When y = 0 was substituted in this relational expression, the amount of ammonium thiocyanate C was 0.00318 mmol / g-KBr from this absolute value. Here, since the tablet used for the FT-IR measurement is prepared by mixing 10 mg of Extract A and 1 g of KBr, the amount of ammonium thiocyanate C in Extract A is 0.318 mmol / g-extract. It becomes. Since the molecular weight of ammonium thiocyanate is 76.12, the amount of ammonium thiocyanate C in the extract A is 0.0242 g / g-extract. Since the amount of the extract A is 327 mg / L, the concentration of ammonium thiocyanate C in the desulfurization solution is 327 × 0.0242 = 8 mg. From the above, the concentration of ammonium thiocyanate C in the desulfurization solution was obtained.

<Elemental analysis>
The elemental analysis of the extract A was performed using an elemental analyzer (product name “Perkin Elmer 2400 Series II CHNS / O Analyzer”, manufactured by PerkinElmer Japan Co., Ltd.). The results are shown in the column “F-1 (inlet)” in Table 2.

As a result of elemental analysis, the content of sulfur as an element was 14.3% by weight. Here, sulfur as an element is included not only as elemental sulfur but also as part of the structure of ammonium thiocyanate. Therefore, the concentration of elemental sulfur was determined by the following formula.
(Concentration of elemental sulfur) = (Concentration of extract) × (wt% of S by elemental analysis) − (Concentration of sulfur in ammonium thiocyanate)

Where (concentration of sulfur in ammonium thiocyanate) is
(Concentration of ammonium thiocyanate) x ((molecular weight of sulfur) / (molecular weight of ammonium thiocyanate))
Is required.

Since the concentration of ammonium thiocyanate has already been determined and is 8 mg / L,
(Concentration of sulfur in ammonium thiocyanate) = 8 (mg / L) × 0.42
Therefore, it becomes 3.36 mg / L.
Therefore,
(Concentration of simple sulfur) = 327 (mg / L) × 14.3% −3.36 (mg / L)
Accordingly, the concentration of elemental sulfur is 43 mg.

And based on the concentration of the obtained extract A, the concentration of elemental sulfur B, the concentration of aliphatic hydrocarbon D, and the concentration of ammonium thiocyanate C, the concentration of picric acid reduction product F was determined by the following calculation formula. .
(Concentration of picric acid reduction product F) = (concentration of extract A)-(concentration of elemental sulfur B)-(concentration of aliphatic hydrocarbon D)-(concentration of ammonium thiocyanate C)

  The concentration of each component obtained as described above is summarized as shown in the column “F-1 (inlet)” in Table 3 below.

Example 1
The absorption liquid was sampled from the sampling tube S3 by changing the date and time, and the concentration of the picric acid reduction product before extraction rate conversion was measured by the same method as in Reference Example 1. The results are shown in Table 4. Table 4 shows the measurement results of the absorbance at 475 nm of the sample before the organic substance extraction and the absorbance at 475 nm of the sample after the organic substance extraction. U-2900 (ultraviolet visible spectrophotometer) manufactured by Hitachi High-Technologies Corporation was used for the measurement. Table 4 also shows the extraction rate (%). The extraction rate (%) is obtained by the following formula.
(Extraction rate (%)) = (1 − ((absorbance after extraction) / (absorbance before extraction))) × 100
Table 4 also shows the concentration of the picric acid reduction product after conversion to the extraction rate. The concentration of the picric acid reduction product after extraction rate conversion is obtained by the following formula.
(Picric acid reduction product concentration) = (Concentration of picric acid reduction product F before extraction rate conversion) × (100 / (extraction rate (%)))

(Examples 2-9)
By changing the date and time, the concentration of the picric acid reduction product before conversion of the extraction rate was measured by the same method as in Example 1. The results are shown in Table 4. Table 4 shows the measurement results of the absorbance at 475 nm of the sample before the organic substance extraction and the absorbance at 475 nm of the sample after the organic substance extraction. Table 4 also shows the extraction rate (%) and the concentration of the picric acid reduction product after conversion to the extraction rate. The extraction rate (%) and the concentration of the picric acid reduction product after conversion to the extraction rate were determined in the same manner as in Example 1.

FIG. 10 is a graph showing a relationship between the picric acid reduction product concentration measured in Examples 1 to 9 (picric acid reduction product concentration after extraction rate conversion) and the amount of added picric acid.
FIG. 11 is a graph showing a relationship between the concentration of a picric acid reduction product before conversion of the extraction rate in Examples 1 to 9 and the amount of added picric acid.
The correlation between the picric acid reduction product concentration converted to the extraction rate and the added picric acid (see FIG. 10) is from the correlation between the picric acid reduction product concentration before the extraction rate conversion and the added picric acid (see FIG. 11). It was confirmed that there was a good correlation. From this, it can be seen that the picric acid reduction product concentration in terms of extraction rate has less variation in measurement results.

For Examples 1 to 9, the amount of picric acid added to the desulfurization system at that time, the amount of the desulfurization liquid extracted outside the desulfurization system, and the amount of picric acid extracted outside the desulfurization system were extracted. Table 5 below shows the picric acid reduction product concentration after conversion.
The amount of picric acid extracted out of the desulfurization system is obtained by the following formula.
(Amount of picric acid extracted outside desulfurization system (kg / day)) = ((concentration of picric acid reduction product after conversion of extraction rate (mg / L)) / 1000) × ((desulfurization extracted outside desulfurization system) Amount of liquid (m ³ / hour)) × 24)

FIG. 12 is a graph showing plots of Examples 1 to 9 obtained by plotting the amount of picric acid extracted outside the desulfurization system as the x axis and the amount of picric acid added into the desulfurization system as the y axis.
About Examples 1-9, the amount of picric acid extracted out of the desulfurization system is plotted on the x-axis, the amount of picric acid added in the desulfurization system is plotted on the y-axis, and the approximate straight line shown in FIG. (Y = 13.061x-156.29) was obtained. Here, x, that is, the amount of picric acid extracted outside the desulfurization system is represented by the following formula as described above.
(Amount of picric acid extracted outside desulfurization system (kg / day)) = ((concentration of picric acid reduction product after conversion of extraction rate (mg / L)) / 1000) × ((desulfurization extracted outside desulfurization system) Amount of liquid (m ³ / hour)) × 24)
Y is the amount of picric acid added to the desulfurization system.
Therefore, when the obtained approximate straight line is substituted for x and y and deformed, the result is as follows.
(Concentration of picric acid reduction product after conversion to extraction rate (mg / L))) = [((amount of picric acid added to desulfurization system (kg / day)) + 156.29) × 1000] / (13. 061 × (amount of desulfurization liquid extracted outside the desulfurization system (m ³ / hour)) × 24)
Therefore, the amount of picric acid added into the desulfurization system and the amount of the desulfurization liquid extracted outside the desulfurization system are substituted without actually measuring the concentration of the picric acid reduction product after conversion to the extraction rate. Thus, the concentration of the picric acid reduction product after conversion to the extraction rate can be obtained.
As a result, an estimated value of the concentration in the desulfurization system can be obtained almost in real time, and an amount of picric acid corresponding to the concentration can be added.

  As mentioned above, although embodiment and the Example of this invention were described, this invention is not limited to the example mentioned above, In the range which satisfies the structure of this invention, it can change a design suitably. Is possible.

DESCRIPTION OF SYMBOLS 10 Coke oven gas desulfurization equipment 12 Desulfurization tower 13 Piping 14 Regeneration tower 16 Piping 17 Piping 18 Desulfurization waste liquid processing equipment 22 Filler S1 Sampling pipe S2 Catalyst addition pipe S3 Sampling pipe Pi Picric acid COG1 Coke oven gas COG2 Desulfurization coke oven gas A air

Claims (4)

A coke oven gas desulfurization method for desulfurizing a coke oven gas with an alkaline aqueous solution containing a picric acid reduction product,
Step X-1 for extracting the absorbing liquid out of the desulfurization system,
Step X-2 for determining the concentration of the picric acid reduction product in the absorption liquid extracted outside the desulfurization system in Step X-1.
Step X-3 for determining the amount of the picric acid reduction product extracted out of the desulfurization system based on the concentration of the picric acid reduction product determined in Step X-2 and the amount of the extracted absorbent.
Step X-4 of adding an amount of picric acid based on a rule of thumb into the desulfurization system,
Correlation between the amount of picric acid added in the desulfurization system and the amount of picric acid reduction product extracted out of the desulfurization system is expressed as the step X-1, the step X-2, the step X-3, and the Step Y obtained by repeating Step X-4 as a set multiple times, and
A step of determining the concentration of the picric acid reduction product in the desulfurization system based on the correlation obtained in the step Y, the amount of picric acid added to the desulfurization system, and the amount of the absorption liquid extracted outside the desulfurization system. A method for desulfurizing coke oven gas, comprising Z. Step X-2 includes
A process of extracting organic matter from the extracted absorbent,
A process of performing elemental analysis on the extract,
Performing infrared spectroscopic analysis on the extract; and
The desulfurization of coke oven gas according to claim 1, further comprising a step of determining a concentration of a picric acid reduction product in the absorption liquid based on a result of the elemental analysis and a result of the infrared spectroscopic analysis. Method. Step X-2 includes
Step A for performing ultraviolet absorption analysis on the extracted absorption liquid,
Step B for extracting organic substances from the absorption liquid after performing ultraviolet absorption analysis,
Step C for performing ultraviolet absorption analysis on the absorbing solution after extracting the organic matter,
Process D for performing elemental analysis on the extract,
Step E for performing infrared spectroscopic analysis on the extract,
Step F for obtaining the extraction rate of the picric acid reduction product in the organic substance based on the result of the ultraviolet absorption analysis in the step A and the result of the ultraviolet absorption analysis in the step C,
Based on the result of the elemental analysis in the step D and the result of the infrared spectroscopic analysis in the step E, the step G of obtaining the picric acid reduction product concentration before conversion of the extraction rate, and
The process H for obtaining a picric acid reduction product concentration from the picric acid reduction product concentration before the extraction rate conversion obtained in the step G and the extraction rate obtained in the step F are included. Coke oven gas desulfurization method as described.   The coke oven according to any one of claims 1 to 3, further comprising a step of adjusting an addition amount of picric acid based on a concentration of a picric acid reduction product in the desulfurization system obtained by the step Z. Gas desulfurization method.

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