JPS612039A - Method for analyzing quantity of phosphoric acid in exhaust gas of fuel battery - Google Patents

Abstract

PURPOSE:To improve the collecting efficiency of phosphoric acid mist or vapor in exhaust gas and to attain rapid quantitative analysis by heating a conduit coupled with the outlet side of exhaust gas so that the temperature of the exhaust gas is kept at a temperature near the working temperature of a fuel battery. CONSTITUTION:Exhaust gas 20 including phosphoric acid mist exhaused from the exhaust gas outlet 5 of the fuel battery 1 and formed water vapor is carried from a conduit part 6 to a condenser 8. The conduit part 6 is kept at its temperature by a ribbon heater and an insulating material so that the exhaust gas 20 is kept at a temperature close to the working temperature (about 180-210 deg.C) of the fuel battery 1 and its inwall is prevented from the adhesion of phosphorous mist or vapor. The condenser 8 is stored in a cooler 9 so that the exhaust gas 20 is cooled to condense and liquefy the formed vapor and the phosphoric acid mist is dissolved in the condensed solution to collect the mist as a phosphoric acid solution 11. The collected solution 11 is sent to an analyzer 15 such as an ion chromatography to find out the quantity of phosphoric ion in the delivered solution and convert the ion quantity into the quantity of phosphoric acid. Since the required volume of the solution may be 1ml or less, a time required for the collection can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for collecting and quantitatively analyzing phosphoric acid mist in fuel cell exhaust gas.

[Prior art and its problems]

Recently, phosphoric acid fuel cells have been used to generate electricity, and during power generation, phosphoric acid, which is heated to an operating temperature of around 200°C, is dispersed in the form of a mist from the porous electrode part into the oxidizer exhaust gas. , a small amount is discharged to the outside of the battery together with the water vapor produced by the electrochemical reaction. Therefore, when investigating the characteristics of fuel cells and detoxifying exhaust gas,
There is a need to quantitatively understand the amount of phosphoric acid in exhaust gas.

In general, as a method of collecting exhaust gas, J-Ko S-K 00
95-1979 A method is known in which an absorption bottle or a collection bottle with an exhaust gas sampling force of 1 is used. However, this method originally targets only gaseous components and does not collect mist or dust, and because it collects the exhaust gas itself, it requires a large amount of exhaust gas to collect the phosphoric acid mist required for analysis. The phosphoric acid mist will adhere to the walls of the conduit and collection equipment, so if you want to analyze the adhered phosphoric acid, wash it out with distilled water and collect the aqueous solution. There are many problems such as the need to analyze the phosphoric acid mist and the collection work of phosphoric acid mist is complicated and takes a long time.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is a method for collecting and analyzing phosphoric acid in exhaust gas, which has high efficiency in collecting phosphoric acid mist and water vapor in exhaust gas, and provides quantitative analysis results in a short time. The purpose is to provide

[Key points of the invention]

The method of the present invention focuses on the fact that the amount of reaction product water precipitated in the oxidizer exhaust gas of a phosphoric acid fuel cell is precisely proportional to the output current and time of the fuel cell based on Faraday's law. Water vapor in the exhaust gas, which consists of a conduit section connected to the oxidizer exhaust gas outlet side of the cell and equipped with a holding means for keeping the exhaust gas temperature close to the operating temperature of the fuel cell, and a condenser connected to the other end of this conduit section. In addition, the phosphoric acid mist collecting means collects the phosphoric acid mist in the exhaust gas as a phosphoric acid aqueous solution by dissolving it in contact with the condensed water condensed in the condenser without adhering to the conduit part, and collecting it as a phosphoric acid aqueous solution. Analyze the amount of phosphoric acid with an analyzer such as ion chromatography to determine the amount of phosphoric acid released per unit time, and if necessary, calculate the amount of phosphoric acid released per unit time from the flow rate of the oxidant gas per unit time and the amount of phosphoric acid released. This method is designed to determine the concentration of phosphoric acid in exhaust gas.

[Embodiments of the invention]

The present invention will be explained below based on examples.

FIG. 1 is a fundamental block diagram of a collection means and an analysis device for explaining the present invention in detail. In the figure, 1 is a phosphoric acid fuel cell, 2 is an inlet for fuel gas such as hydrogen gas, 3 is an outlet for fuel exhaust gas, 4 is an inlet for oxidizing gas such as air, and 5 is oxidizing exhaust gas. This is the exit part of the 6
is a conduit portion whose one end communicates with the outlet portion 5 of the oxidizer exhaust gas;
7 is a heat insulating means formed to surround the conduit section 6; 8 is a condenser connected to the conduit section 6 at one end; 9 is a cooler housing the condenser 8; 1o
is stored. Reference numeral 15 denotes an analysis device such as an ion chromatography device, and a switching valve 14. The phosphoric acid aqueous solution 11 collected at the bottom of the condenser 8 is communicated with the bottom of the condenser 8 through a thin tube 13 etc.
By periodically introducing aqueous solution (μm), it is possible to quantitatively analyze the amount of phosphate ions in the aqueous solution.

In a phosphoric acid fuel cell, water is generally produced on the air electrode side by an electrochemical reaction based on Faraday's law expressed as 3A 09 + 2H+ 2 e→H,Ote, and the water produced is at the operating temperature of the fuel cell. (180℃～
When water vapor (equivalent) at a temperature close to 210° C. (approx.

Therefore, a small amount of phosphoric acid mist is ejected into the exhaust gas on the oxidizing gas (air) side along with the generated water vapor that is ejected from the surface of the porous air electrode into the exhaust gas, and is carried along with the flow of the exhaust gas to the exhaust gas outlet 5. Conduit section 6. It passes through a path called a condenser 8 and is discharged to the outside of the fuel cell from an exhaust port 12 of the condenser 8. However, since the amount of reaction product water discharged from the fuel cell per unit time can be theoretically determined from the above equation, if the phosphoric acid concentration in the phosphoric acid aqueous solution is determined, the amount of phosphoric acid mist generated per unit time can be determined theoretically. The amount of emissions can be determined.

In addition, both the phosphoric acid and the vapor to be quantified are condensable, and the exhaust gas that has been rendered harmless after passing through the condenser can be released into the atmosphere. The collection means can be made compact.

The method of the present invention was made based on the above-mentioned idea, and the exhaust gas 20 containing phosphoric acid mist and generated water vapor flowing into the conduit section 6 from the exhaust port 5 of the fuel cell 1 is transferred to a pipe provided in the conduit section. For example, the exhaust gas 20 is kept at a temperature close to the operating temperature of the fuel cell by a heat insulating means such as a ribbon heater, a heat insulating material, etc., and the exhaust gas 20 is transferred to the condenser 8 while preventing phosphoric acid mist and water vapor from condensing and adhering to the inner wall of the conduit section 6. A condenser 8 housed in a cooler 9 containing a cooling medium 10 such as ice cools the exhaust gas 20 and condenses and liquefies the generated water vapor, and dissolves the phosphoric acid mist into the condensed liquid. In this case, it can be collected as an aqueous silicic acid solution 11. The phosphoric acid aqueous solution 11 collected in this way is
．． The phosphate ions (po
s-) is determined and converted to the amount of phosphoric acid (HsPOn). This analysis method can quickly quantify phosphate ions using a minute amount of aqueous solution of about 100 μm.
The amount of phosphoric acid aqueous solution 11 to be collected may be less than 1 ml, and the time required for collection is short.

FIG. 2 is a schematic diagram of the collection means and analysis device used to verify the performance of the above-mentioned example. In order to improve the collection performance of phosphoric acid mist, three sets of condensers 8A and 8 are installed.
B, f3C are connected in series to each other via conduit portions 6A, 6B, 6C, and thin tubes 13A, 13B
, 13C in condensers 8A, 8B, and 8C, respectively, and quantitatively analyzed by ion chromatography separately.

The following describes the results of an experiment in which the apparatus shown in FIG. 2 was used to collect and analyze phosphoric acid mist and generated water in fuel cell exhaust gas.

Experimental conditions (a) Fuel cell operating conditions Operating temperature: 180°C Electrode area: 30c1n" Current density: 100A2 Gas flow rate: 260cm"7m1n (b) Collection means condenser ...Height: 150 m, 8-stage condenser with spiral tube section ...Water-filled siduwa bottle (c)) Determination method of phosphoric acid Ion chromatography Phosphate ion (PO4')
) Determination of the amount of phosphoric acid (1spoi) is calculated from the amount of phosphate ions Using the apparatus shown in Figure 2, operate the fuel cell for 6 hours under the conditions of (a) to (c) above to collect the phosphoric acid mist. At the same time, the amount w(t) of the obtained condensed water and the amount X(1) of phosphoric acid were determined, and the results are shown in Table 1.

If the theoretical amount of produced water W is calculated using the above-mentioned equation under the operating conditions of the fuel cell, then W=1p per hour, and approximately 62 volumes of produced water are produced in 6 hours of operation.

On the other hand, the measurement results of condensed water in Table 1 show that 5 and 8 f, which is 97% of the theoretical amount of water produced, is collected, and the condenser 8A can collect most of the water produced. I understand. On the other hand, phosphoric acid was detected in the condensate of condensers 8A and 8B, and the total detected amount in condenser 8A was 097, 8%K.
1.05x1o'P has been detected. From these results, it can be seen that the collection means of the present invention has extremely excellent collection performance for phosphoric acid and reaction product water. Furthermore, from the above experimental results, it is clear that at least the condenser 8C among the three condensers can be omitted.
It is estimated that more than 9% of produced water and phosphoric acid mist can be collected. According to the method of the present invention, as described above, 1 ton of phosphoric acid aqueous solution can be collected per hour from one fuel cell single cell with an electrode area of 30 cWLI using a simple collection means, and large-sized fuel When applied to battery stacked cells, it is thought that it is possible to reduce the time required to collect the analysis sample to about a few minutes, and therefore, even including the time required to quantify phosphoric acid, analytical results can be obtained in about a few minutes. be able to.

Also, from the above experimental results, the amount of condensed water per unit time is 0.0
167 f/min, the phosphoric acid concentration in the exhaust gas per unit time can be easily determined.

〔Effect of the invention〕

As described above, the present invention utilizes a conduit connected to an exhaust gas outlet and equipped with heat insulating means to collect phosphoric acid mist ejected from the oxidizer-side electrode of a phosphoric acid fuel cell into exhaust gas as reaction product water vapor is generated. The phosphoric acid mist and generated water vapor are collected in the form of a phosphoric acid aqueous solution, and the phosphate ions (PO4) in the collected aqueous solution are quantitatively analyzed using ion chromatography. The result was converted into phosphoric acid (HsPOn), and the amount of phosphoric acid generated per unit time was determined from the amount of water produced by the reaction determined based on Faraday's law. As a result, the conventional problem of phosphoric acid mist and water vapor adhering to the inner wall of the collection device due to the conduit section equipped with heat retention means is eliminated, and the condenser prevents phosphoric acid mist and reaction product water vapor from adhering to the inner wall of the collection device. can be collected quickly and with high collection efficiency in the form of an aqueous phosphoric acid solution, and the amount of phosphoric acid can be quickly and accurately quantified using a small amount of an aqueous phosphoric acid solution using ion chromatography. A method for analyzing the amount of phosphoric acid can be provided. Note that the method of the present invention can be easily applied to constant monitoring of the phosphoric acid concentration in exhaust gas by automating the apparatus.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the collection means and analysis device for explaining an embodiment of the method of the present invention, and Fig. 2 is a schematic diagram of the collection means and analysis device used to verify the performance of the method of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Phosphoric acid fuel cell, 4... Oxidizing gas (air) inlet part, 5... Oxidizing exhaust gas outlet part, 6, 6A
. 6B, 6C... Conduit part, 7... Heat retention means, 8,
8A. 8B, 8C... Condenser, 9... Cooler, 1o...
Cooling medium, 11... Condensate (phosphoric acid aqueous solution), 12.
・Exhaust gas outlet, 13, 13A, 13B, 13C...
Thin tube, 14... switching valve, 15... analyzer (ion chromatography), 20... exhaust gas (contains phosphoric acid mist, generated water vapor). 2゜Figure 1

Claims (1)

[Scope of Claims] 1) A conduit section connected to an exhaust gas outlet from an oxygen electrode side gas chamber of a phosphoric acid fuel cell and equipped with a heat insulating means for keeping the exhaust gas temperature close to the operating temperature of the fuel cell, and this conduit section. a condenser connected to the other end of the exhaust gas, and an analyzer for quantifying the amount of phosphoric acid dissolved in the phosphoric acid aqueous solution collected by the condenser. A method for analyzing the amount of phosphoric acid in exhaust gas from a fuel cell, comprising: determining the concentration of phosphoric acid in the exhaust gas based on a predetermined formula from the amount of phosphoric acid dissolved in the aqueous solution and the amount of exhaust gas. 2) A method for analyzing the amount of phosphoric acid in fuel cell exhaust gas, characterized in that the analysis device is an ion chromatography device. 3) The method according to claim 1, wherein the heat retaining means comprises a band heater attached to the outer periphery of the liquid guide pipe and a heat insulating layer surrounding the outer periphery of the band heater. Method for analyzing phosphoric acid content. 4) A method for analyzing the amount of phosphoric acid in fuel cell exhaust gas according to claim 1, characterized in that the condenser is housed in a cooler maintained at a temperature close to 0°C.