CN104931573A - Analysis method of light tar in biomass gas - Google Patents

Abstract

The invention relates to an analysis method for light tar in biomass gas, comprising five steps of light tar collection, tar desorption, mass spectrometry, standard curve preparation and quantitative analysis; the method is simple and efficient in sampling; the sample solvent replacement is assisted by ultrasound The desorption process by other means has high desorption efficiency; the analysis process is easy and sensitive to operate, and the separation effect is good; the recovery rate of light polycyclic aromatic hydrocarbon tar is high, the repeatability is good, and the detection limit is low, which provides reliable data for the tar separation process and the prevention and control of environmental pollution; The method of the invention can be popularized for sampling and rapid qualitative and quantitative analysis of medium and light volatile organic compounds.

Description

A kind of analysis method of light tar in biomass gas

technical field

The invention relates to a method for analyzing light tar in biomass gas, in particular to a method for sampling and GC-MS (gas chromatography-mass spectrometry) analysis of light tar in biomass gas, which belongs to the intersection of biomass thermochemical conversion and chemical analysis, etc. technology field.

Background technique

The biomass gasification process inevitably produces tar. During the subsequent use of gas, tar is easy to combine with impurities such as water, dust, and carbon particles, blocking gas pipes and valves, and corroding metals; it is difficult to burn completely, and particles such as carbon black are produced, which seriously damages internal combustion engines and gas turbine impellers; its energy generally accounts for 5-15% of the total energy of the gas is difficult to burn and utilize together with the gas, which reduces the gasification efficiency. Therefore, the tar in the gas must be deeply purified.

Biomass gas tar can be defined as a complex mixture of aromatic hydrocarbons and their derivatives produced during the thermochemical conversion of biomass. More than 100 kinds of components can be detected, among which there are about 7 kinds with a mass fraction greater than 5%, namely benzene, toluene, xylene, styrene, naphthalene, phenol and indene. Tar is gaseous above 300°C, and gradually condenses into liquid below 200°C.

The composition of tar is complex, and the analysis of its composition and structure can provide basic information for its separation and comprehensive utilization, solve the environmental problems and resource waste problems it brings, and further extract valuable chemical raw materials such as phenols or process them into various fuels oil or solvent. Therefore, the high value-added utilization of tar will directly affect the cost of the gas production process. In order to make better use of tar, GC-MS and HPLC-MS methods for total component analysis of tar were developed. However, this type of method is relatively complicated. The sampling is usually a semi-gelled tar obtained by condensation. The sample needs to be subjected to measures such as solvent extraction, acid-base separation of phenol, and chromatographic segmentation before it can be analyzed again; it is often necessary to assist infrared and element analysis. Only by analyzing can a more complete qualitative and quantitative analysis be carried out.

In order to ensure the safe use of biomass gas, it must be deeply decoked. After decoking, the tar content in the gas is generally lower than 200mg/Nm ³ (about 200ppm). At this time, the number of tar components in the gas is greatly reduced, mainly concentrated in light polycyclic aromatic hydrocarbon tars with less than 4 benzene rings. For the trace amount of tar in the purified gas, the above analysis method is too complicated and has poor versatility. Adsorption-thermal desorption chromatography is an important method for the analysis of such trace organic compounds. However, in this type of method, the thermal desorption temperature generally does not exceed 250° C. (the tar with 3 or 4 benzene rings is difficult to effectively desorb), the desorption time is long, the desorption efficiency is low, and the general recovery rate is lower than 90%. Japan Yoshikawa team (Son Y, Sato M, Namioka T, Yoshikawa KA study on measurement of light tar content in the fuel gas produced in small-scale gasification and power generation systems for solid wastes. J Environ Eng 2009,4:12-23.) A GC-FID (FID, hydrogen flame) method of gas tar adsorption-thermal desorption was established. The disadvantage is that the efficiency of thermal desorption is low. At the same time, pure chromatography also has limitations in the qualitative determination of tar components.

Contents of the invention

The purpose of the present invention is to provide a method for analyzing light tar in biomass gas in order to improve the deficiencies of the prior art.

The technical scheme of the present invention is: a kind of analysis method of light tar in biomass fuel gas, its concrete steps are as follows:

(1) Tar collection: Use a sampling tube equipped with an adsorbent to collect tar samples at room temperature (generally 0-25°C), and store them in a refrigerator after collection;

(2) Tar desorption: Utilize organic solvents, carry out displacement desorption under heating and ultrasonic measures, and centrifuge the adsorbent dust after desorption;

(3) Mass spectrometry qualitative: the tar obtained by desorption is qualitatively analyzed by mass spectrometry;

(4) standard curve preparation: utilize step (3) qualitative composition, configure the standard solution of different concentrations, carry out chromatographic analysis, and draw standard curve;

(5) Quantitative analysis, utilize the tar that step (2) desorbs to obtain to carry out chromatographic analysis, and compare with the standard curve that step (4) obtains, calculate and obtain the content of tar in the combustion gas.

Preferably, the flow rate of gas collection in step (1) is 10-1000ml/min, and the collection time is 1-10min.

The adsorbent described in the preferred step (1) is activated carbon or commercial Tenax TA (a porous polymer based on 2,6-diphenylfuran); the specific surface area of the adsorbent is preferably greater than 800m ² /g, and the pore distribution is Spans micropores, mesopores and macropores.

The organic solvent described in the preferred step (2) is at least one of methanol, acetone or chloroform;

The mass ratio of agent and adsorbent is 10-30:1.

The ultrasonic frequency of the preferred step (2) is 30-100kHz, and the ultrasonic time is 5-20min; the displacement desorption temperature is 30-50°C; 3~5min.

Preferably, the mass spectrometry qualitative conditions described in step (3) are: ion source temperature 230-300°C, transmission line temperature 250-300°C; scanning mode is electronic scanning, electron bombardment energy 60-80eV.

The chromatographic conditions described in the preferred step (4) are: adopt non-polar or medium polar capillary chromatographic column; 35～50 ℃ of column temperature keep 1min, 10 ℃/min heating rate rises to 150 ℃, keep 1min, then Raise the temperature to 250-320°C at a rate of 20°C/min, and keep for 2min; the temperature of the injection port is 230°C, the carrier gas is helium, the flow rate is 1ml/min, the pressure is 3kPa, and the split ratio is 10:1; The sample volume is 1 μL. Preferably, the capillary chromatographic column described in step (4) is DB-5, HP-5 or DB-17.

Beneficial effect:

(1) This method is easy to sample and has high sampling efficiency;

(2) The desorption efficiency is high during the desorption process by means of sample solvent replacement assisted by ultrasound;

(3) The analysis process is easy and sensitive to operate, and the separation effect is good;

(4) The recovery rate of light polycyclic aromatic hydrocarbon tar is high, the repeatability is good, and the detection limit is low, which provides reliable data for the separation process of tar and the prevention and control of environmental pollution;

(5) The method of the present invention can be popularized for sampling and rapid qualitative and quantitative analysis of medium and light volatile organic compounds.

Description of drawings

Fig. 1 is embodiment 1 sample chromatographic qualitative spectrogram.

Detailed ways

The present invention is effectively realized by the following examples, but the applicable scope of the present invention is not limited thereby.

Example 1

Step (1), using an adsorption tube equipped with 1g of activated carbon to collect tar in the gas, the collection time is 5min, the collection flow rate is 1000ml/min, and the collection temperature is 35°C; after the collection is completed, the two ends of the sampling pipe are characterized in that The tar samples were collected at room temperature using a sampling tube filled with adsorbent, and were stored in a refrigerator for 5 days after collection.

In step (2), the adsorption tube obtained by sampling is cut off, the activated carbon is transferred to the centrifuge tube, and 20ml of acetone is added; the centrifuge tube is ultrasonicated at 35°C and 40kHz for 10min; after ultrasonication, the tar adsorbed by the activated carbon is transferred into the acetone, However, the activated carbon was also partially broken, and the dust entered into the acetone, so the centrifuge tube was centrifuged at 5000 rpm for 3 minutes to separate the dust from the solution.

In step (3), 1ml of the above solution was taken and sent to GC-MS for scanning. The qualitative conditions of mass spectrometry were: ion source temperature 250°C, transmission line temperature 270°C; scanning mode was electronic scanning, and electron bombardment energy was 70eV. The range of ion fragments was determined by full scan, and the samples were qualitatively classified as benzene, toluene, xylene, styrene, phenol, pyridine, indene, naphthalene, phenanthrene, anthracene, and pyrene (see attached table 1 for qualitative results), all of which contained four benzene A tar molecule within a ring molecule. After the qualitative analysis, the characteristic ion scanning is carried out. The scanning results are shown in Figure 1, and each component has been effectively separated and qualified.

Step (4), use the qualitative components of step (3), configure standard solutions of different concentrations, and carry out chromatographic analysis, and the chromatographic conditions for qualitative coordination with the above-mentioned mass spectrometry are: the chromatographic column adopts a DB-5 capillary chromatographic column; the column temperature is maintained at 50 ° C 1min, 10°C/min heating rate to 150°C, hold for 1min, then rise to 280°C at a heating rate of 20°C/min, hold for 2min; the temperature of the injection port is 230°C, the carrier gas is helium, and the flow rate is 1ml /min, the pressure is 3kPa, the split ratio is 10:1; the injection volume is 1μL. According to the peak area or peak height, draw a standard curve, see Table 1-1.

Step (5), the tar sample that desorption obtains carries out chromatographic analysis, and chromatographic condition is consistent with step (4), according to the peak area or peak height of sample,

Compared with the standard curve, the tar content in the gas is calculated, and the content results are shown in Table 1-2.

Example 2

Step (1), use the adsorption tube equipped with 1.5g adsorbent Tenax TA to collect the tar in the gas, the collection time is 10min, the collection flow rate is 10ml/min, and the collection temperature is 35°C; , is characterized in that utilizes the sampling tube that adsorbent is housed to carry out tar sample collection at room temperature, after collecting, put refrigerator to refrigerate and store for 10 days.

Step (2), cut off the adsorption tube obtained by sampling, transfer the activated carbon to the centrifuge tube, add 10ml of methanol; ultrasonicate the centrifuge tube for 18min at 30°C and 30kHz; after ultrasonication, the tar adsorbed by Tenax is transferred into the methanol, However, Tenax was also partially broken, and the dust entered methanol, so the centrifuge tube was centrifuged at 3000 rpm for 4 minutes to separate the dust from the solution.

In step (3), 1ml of the above solution was taken and sent to GC-MS for scanning. The qualitative conditions of mass spectrometry were: ion source temperature 230°C, transmission line temperature 250°C; scanning mode was electronic scanning, and electron bombardment energy was 60eV. The full scan determined the range of ion fragments, and the samples were characterized as benzene, toluene, xylene, styrene, phenol, pyridine, naphthalene, and phenanthrene, all of which were tar molecules containing less than 4 benzene ring molecules. After the qualitative analysis, the characteristic ion scanning was carried out, and each component was effectively separated and qualified.

Step (4), using the qualitative components of step (3), configure standard solutions of different concentrations, and carry out chromatographic analysis, and the chromatographic conditions for qualitative coordination with the above-mentioned mass spectrometry are: the chromatographic column adopts HP-5 capillary chromatographic column; the column temperature is maintained at 40°C 1min, 10°C/min heating rate to 150°C, hold for 1min, then rise to 250°C at a heating rate of 20°C/min, hold for 2min; the temperature of the injection port is 230°C, the carrier gas is helium, and the flow rate is 1ml /min, the pressure is 3kPa, the split ratio is 10:1; the injection volume is 1μL. According to the peak area or peak height, draw a standard curve, see Table 2-1.

In step (5), the tar sample obtained by desorption is subjected to chromatographic analysis, and the chromatographic conditions are consistent with step (4). According to the peak area or peak height of the sample, compare with the standard curve, calculate the tar content in the gas, and the content results are shown in the table 2-2 shown.

Example 3

Step (1), using an adsorption tube equipped with 2g of activated carbon to collect the tar in the gas, the collection time is 1min, the collection flow rate is 500ml/min, and the collection temperature is 25°C; after the collection is completed, the two ends of the sampling tube are characterized in that The tar samples were collected at room temperature using sampling tubes filled with adsorbents, and qualitative and quantitative analyzes were performed directly after collection.

Step (2), cut off the adsorption tube obtained by sampling, transfer the activated carbon to the centrifuge tube, add 30ml of chloroform; ultrasonicate the centrifuge tube for 4min at 48°C and 95kHz; after ultrasonication, the tar adsorbed by the activated carbon is transferred into the chloroform, However, the activated carbon was also partially broken, and the dust entered into the chloroform, so the centrifuge tube was centrifuged at 8000 rpm for 5 min to separate the dust from the solution.

In step (3), 1ml of the above solution was taken and sent to GC-MS for scanning. The qualitative conditions of mass spectrometry were: ion source temperature 290°C, transmission line temperature 295°C; scanning mode was electronic scanning, electron bombardment energy 80eV. The range of ion fragments was determined by the full scan, and the samples were characterized as benzene, toluene, xylene, styrene, phenol, pyridine and naphthalene, all of which were tar molecules containing less than 4 benzene ring molecules. After the qualitative analysis, the characteristic ion scanning was carried out, and each component was effectively separated and qualified.

Step (4), using the qualitative components of step (3), configure standard solutions of different concentrations, and carry out chromatographic analysis, and the chromatographic conditions for qualitative coordination with the above-mentioned mass spectrometry are: the chromatographic column adopts a DB-17 capillary chromatographic column; the column temperature is maintained at 35°C 1min, 10℃/min heating rate to 150℃, hold for 1min, then increase temperature at 20℃/min to 320℃, keep for 2min; inlet temperature is 230℃, carrier gas is helium, flow rate is 1ml /min, the pressure is 3kPa, the split ratio is 10:1; the injection volume is 1μL. According to the peak area or peak height, draw a standard curve, see Table 3-1.

In step (5), the tar sample obtained by desorption is subjected to chromatographic analysis, and the chromatographic conditions are consistent with step (4). According to the peak area or peak height of the sample, compare with the standard curve, calculate the tar content in the gas, and the content results are shown in the table 3-2 shown.

Table 1-1 Sample standard curve

Table 1-2 Sample quantification table

Table 2-1 Sample Standard Curve

Table 2-2 Sample quantification table

name Characteristic ion Content, mg/Nm ³ Spike recovery, % benzene 78,77,51 12.26 92.43 pyridine 79,52,39 9.21 94.49 toluene 91,92,65,51 7.17 98.66 Xylene 91,106,77,51 6.40 91.20 Styrene 104,103,78,51 12.05 100.66 phenol 94,66,39,55 14.88 100.11 naphthalene 128,102,64,51 1.67 97.02 Philippines 178,152,76,89 9.64 90.56

Table 3-1 Sample standard curve

Table 3-2 Sample quantification table

name Characteristic ion Content, mg/Nm ³ Spike recovery, % benzene 78,77,51 0.76 95.90 pyridine 79,52,39 2.37 92.02 Toluene 91,92,65,51 4.71 90.11 Xylene 91,106,77,51 0.95 101.96 Styrene 104,103,78,51 2.16 91.70 phenol 94,66,39,55 3.93 90.73 naphthalene 128,102,64,51 4.77 101.92

Claims (8)

1. the analytical approach of light tar in biological fuel gas, its concrete steps are as follows:

(1) tar collection: utilize the stopple coupon that adsorbent is housed at room temperature to carry out tar sample collection, collects rearmounted refrigerator cold-storage and stores;

(2) tar desorb: utilize organic solvent, carries out displacement desorption, centrifuging adsorbent dust after desorb under heating and ultrasonic measure;

(3) mass spectrometry: the tar that desorb obtains, utilizes mass spectrum to carry out qualitative analysis;

(4) typical curve prepares: utilize step (3) composition qualitatively, and the standard solution of configuration variable concentrations, carries out stratographic analysis, and drawing standard curve;

(5) quantitative test, the tar utilizing step (2) desorb to obtain carries out stratographic analysis, and compares with the typical curve that step (4) obtains, and calculates the content obtaining tar in combustion gas.

2. analytical approach according to claim 1, it is characterized in that the gas recovery flow described in step (1) is 10 ~ 1000ml/min, acquisition time is 1 ~ 10min.

3. analytical approach according to claim 1, is characterized in that the adsorbent described in step (1) is activated charcoal or commercial Tenax TA.

4. analytical approach according to claim 1, the organic solvent that it is characterized in that described in step (2) is at least one in methyl alcohol, acetone or chloroform; Organic solvent and adsorbent mass ratio are 10 ~ 30 ﹕ 1.

5. analytical approach according to claim 1, it is characterized in that the ultrasonic frequency of step (2) is 30 ~ 100kHz, ultrasonic time is 5 ~ 20min; Displacement desorption temperature is 30 ~ 50 DEG C; Described centrifuging condition is: centrifugal rotational speed is 3000 ~ 8000 turns/s, and centrifugation time is 3 ~ 5min.

6. analytical approach according to claim 1, it is characterized in that the mass spectrometry condition described in step (3) is: ion source temperature 230 ~ 300 DEG C, transmission line temperature is 250 ~ 300 DEG C; Scan pattern is electron scanning, electronics bombarding energy 60 ~ 80eV.

7. analytical approach according to claim 1, is characterized in that the chromatographic condition described in step (4) is: the capillary chromatographic column adopting nonpolar or medium note polarity; 35 ~ 50 DEG C of column temperatures keep 1min, 10 DEG C/min heating rate to rise to 150 DEG C, keep 1min, then rise to 250 ~ 320 DEG C with the heating rate of 20 DEG C/min, keep 2min; Injector temperature is 230 DEG C, and carrier gas is helium, and flow is 1ml/min, and pressure is 3kPa, and split ratio is 10 ﹕ 1; Sample size is 1 μ L.

8. analytical approach according to claim 7, is characterized in that the capillary chromatographic column described in step (4) is DB-5, HP-5 or DB-17.