DE4205793C2 - Method and device for sampling from exhaust gases - Google Patents

Description

The invention relates to a method for sampling and Preparation of samples from exhaust gases, the medium and low volatility substances especially polychlorinated Dibenzo (p) dioxins (PCDD) and polychlorinated Dibenzofurans (PCDF), in a gas or aerosol phase included, with the procedural steps according to the preamble of claim 1.

Such procedures are described in the preliminary draft of the VDI Guideline 3499, Sheet 2 [Title: Measuring poly chlorinated dibenzo (p) dioxins (PCDD) and dibenzofurans (PCDF) in exhaust gases from industrial plants and combustion plants lay].

As PCDD and PCDF, two groups of related chlo designated aromatic substances, which consists of 75 PCDD homologues and 135 PCDF homologues exist. The structures of these substances and the number of possible Lichen isomers of the homolog group contains the called VDI draft directive.

PCDD and PCDF can with a thermal load or when burning chlorine-containing, organic  Material and as unwanted by-products in the manufacture Provision or processing of organochlorine Chemicals are created. It is relatively stable le substances, however, in a furnace at high Temperatures are destructible. The occurrence and the Chemistry of the PCDD / PCDF as well as the toxicological and ecological risks have been described in detail (cf. presentations in the aforementioned VDI 3499).

To determine the content of PCDD and PCDF, stan standardized measuring methods are described. The measuring method should serve exhaust gases from different Anla gene to capture, with raw, pure or synthesis gases among other things to measure from the following exhaust gas generators are:

• - car or diesel engines
• - domestic stoves
• - Equipment for the production of cement
• - Fluidized bed combustion plants
• - shredder systems
• - landfill gas systems
• - Plants for the production and processing of Kera mic, metals, inorganic and organic chemicals lien
• - Melting plants for recycling special substances
• - sewage sludge incineration plants
• - Lignite and hard coal firing plants
• - wood firing systems
• - Oil and gas firing systems
• - waste incineration plants
• - pyrolysis plants

The sample gas temperatures can be between -30 ° and over 1000 ° C. The water content of the exhaust gases fluctuate very strong. This applies analogously to dust concentrations up to over 1 g / m³, as it is for. B. with raw gas before electrostatic precipitator tern occurs.  

According to VDI guideline 3499 (preliminary draft), sheet 2, be Known method works in such a way that a sample gas under isokinetic conditions over a quartz wool stuffed sleeve is sucked in as a particle filter. The Sample gas is then fed to a condensate separator leads, in which it is cooled to 3 to 20 ° C. Nachge there is a cartridge that switches with a Solid adsorbent is filled. All surfaces, with which the sample gas can come into contact of glass; only manifold and z. T. filter head exist made of titanium. At exhaust gas temperatures of over 120 ° C the suction pipe if necessary. cooled with air. The temperatures the particle filter is between 80 and 100 ° C or even significantly below.

After each sampling, all glass in contact with the gas must acidified surfaces under reflux with acetone or toluene get bert. The glass tube of the suction tube is in the Usually cut into 10 cm sections.

The following subsamples must be examined:

• - Glass tube of the suction tube
• - Dust-laden quartz wadding
• - condensate
• - solid adsorbent
• - Toluene / acetone rinsing solution with which the apparatus is cleaned after each sampling.

Accordingly, five partial samples are created, which are initially separated extracted or shaken or redissolved until the solutions thus obtained combined and together for the analysis can be further processed. After Analysis, the removal device is carefully again clean.  

The known sampling apparatus essentially consists from the dust filtration unit, a condensate separator the, the adsorption unit and a suction device with gas meter.

The condensate separator consists of a 2 l three-neck Piston with drain valve and two standard cuts. In the outer each grinding is an intensive cooler. The Sample gas flows from above through the first cooler (commercial usual intensive coolers), passes the condensate container, which is in a 2 l mushroom heating hood and flows then through a high-performance cooler (3000 cm² cooling surface che). A droplet is used to separate the droplets switched glass sleeve, which is filled with Raschig rings. The sample gas then passes into a glass cartridge, which is filled with 250 ml adsorber resin.

The device is extremely complicated to handle and requires appropriately qualified specialist staff. The Rinsing and working with acetone and toluene required careful handling of these flammable substances, which also don't get into the atmosphere should. The subsequent cleaning work is flat if very cumbersome and each require a time effort of at least an hour.

Accordingly, the task arises of a sampling procedure for measuring PCDD and PCDF to be specified by the same detection limits as the known method simp cher feasible, the required Trial devices are also easier to transport.

Surprisingly, it was found that sampling and processing dispenses with condensate collection can be. An adsorbent must be selected that the organic substances from all sorts Physical states of the "original exhaust gas" quantitative  adsorbed.

The solution to the above problem is by a Ver drive to sampling, that makes it possible is characterized in that the partial flow of the exhaust gas an inert dust filter area and then through an area filled with an adsorbent that medium and low volatility organic substances too is adsorbed quantitatively from the condensate and then those in the dust filter area and on Absorbent adsorbed organic substances analyzed become.

The procedure is basically applicable for the sample taking gaseous and / or dust-bound medium and semi-volatile organic substances in gas or Ae pink phases, e.g. B. Exhaust gases from combustion plants. Ver searches show that the method, in particular for Ana preparation of lyses for polyhalogenated aromatics, such as

polychlorinated benzenes (PCBz)
polychlorinated phenols (PCPh)
polychlorinated biphenyls (PCB)
polychlorinated dibenzo (p) dioxins (PCDD)
polychlorinated dibenzofurans (PCDF)
polybrominated dibenzo (p) dioxins (PBDD)
polybrominated dibenzofurans (PBDF)
polybrominated and chlorinated dibenzo (p) dioxins (PBSDD)
polybrominated and chlorinated dibenzofurans (PBCDF)
polycyclic aromatic hydrocarbons (PAH), is applicable.

Using the example of analysis on PCDD and PCDF, procedures are described ren and device described below.

An apparatus for performing the method is  characterized by a temperature-resistant probe with a receiving opening and cool if necessary ed gas line, one that can be connected to the gas line Cartridge with two departments and one exit opening from which the department first passed with an inert, insoluble filter material, e.g. B. quartz wat te, is filled, and in which the second department with an adsorber, e.g. B. Adsorber resin with multireticular Structure is filled. Closes at the exit opening a line with a connected suction pump.

Process and device are characterized by that, unlike the prior art method, which also uses an adsorbent, this is used in the present process without one Condensate excretion through cumbersome cooling processes all components containing PCDD and PCDF to adsorb, it has been found that also the adsorbent is very moist or aqueous is effective and, according to the results so far, even the PCDF and PCDD adsorbs better and more completely than with the conventional method.

In the two departments of the cartridge can be 99% of the dioxins and furans adsorb and fix, see above that the analysis following the sampling is based on the Limit the content of the two cartridge departments can. The two cartridges are then, if necessary. also a compartment to clean or dispose of as they are only made of Glass exist.

Known synthetic, insoluble have been found as adsorbents Liche polystyrene polymers and / or acrylates Amberlite® XAD-2, xAD-4, XAD-7 and XAD-8.  

These are products from E. Merck, Darmstadt. As inexpensive and easy to use Amberlite® in particular has become a manageable product XAD-2 proved.

The filter area is preferably stuffed with Quartz wadding or glass fibers, glass fiber flat filters or other dust-collecting matrices.

An embodiment of the invention is based on the Drawing described. The drawing shows in schematic Scher view the structure of a sampling device.

In an exhaust gas duct 1 , which for example carries the exhaust gas from a waste incineration plant, an exhaust gas is passed through in the direction of the arrow. The exhaust duct 1 is delimited by a duct wall 4 . In the Kanalwan extension 4 , an opening 4 'is present, on which a guide sleeve 5 is placed. The opening 4 'can also be closed if necessary by a (not shown) closing sleeve. In the opening 4 'or the insertion 5 , a probe 3 is inserted. The probe is designed as an elongated jacket tube. Depending on the task, sample gas conditions and arrangement of the measuring point, the probe can be designed differently. Possible materials include: glass, quartz, PTFE plastics, titanium or stainless steel. As a rule, highly resistant glass (DURAN) or quartz glass is used. Such probes are known per se. Depending on the type of installation in the measuring cross-section, the length and the mechanical stress on the probe, it can also be guided in a support tube. If sampling is to be carried out isokinetically, a probe opening 2 must be provided, which is to be installed in accordance with VDI guideline 2066. This guideline must also be observed when designing the probe cross-section.

Extraordinarily high dust contents in the sample gas can Upstream of a pre-separator, such as. B. cyclone, Require filter head with quartz wadding. A such pre-separator is in the embodiment not shown.

To condition the sample gas, it can be heated or, usually, cooled. For this purpose, the probe is provided with a cooling jacket 7 , which can be charged with cooling water via a cooling water inlet and outlet 6 . Inside the cylindrical probe 3 is a glass inner tube 8 , which ends in the front area at the curved probe opening 2 , is guided through the cooled area and is guided to the outside of the channel wall 7 end of the probe at 9 . There is an exhaust and transition manifold 9 . With a corresponding geometric design, this can also be omitted. Between the exhaust and transition manifold 9 and the following units, if necessary, a shut-off valve 14 can be installed. To avoid deposits, the inner glass tube should be as short as possible.

The one drawn off by the probe or the inner glass tube Partial stream can include organic components in the following Contain physical states or included in matrices ten:

• - solid, as a particle
• - adsorbed on particles (solid; liquid; gaseous <
• - liquid, as droplets
• - dissolved in the condensate
• - suspended or emulsified in the condensate (as parti kel;

adsorbed on particles; liquid; solved)

• - gaseous.

The partial flow with the loads mentioned passes through the outlet and transition manifold 9 in a Kartu cal 10 , which is preferably made of glass. The Kartu cal can contain a partition 10 ', preferably a perforated glass plate. In the first section 11 of the cartridge 10 there is a filter for dust separation, in the present example stuffed quartz wadding.

The cartridge 10 is out as an elongated glass cylinder leads. However, this shape and choice of material is only to be understood as an example; for example, spherical, cuboid, etc. cartridge shapes are also possible. Instead of glass, other materials, for example titanium, can also be used. Instead of quartz wool fillings, glass fibers or other materials can be used that are insoluble and are inert towards the substances to be separated.

The second section of the cartridge 10 is filled with a synthetic adsorber resin with a multireticular structure. For this purpose, for example, porous polymers, such as products under the brand name Amberlite® XAD, Carbopak®-C or Tenax®-GC, which are available from various manufacturers, are suitable. However, it should not exclude polyurethane foams, silica gel or other adsorbents that are able to adsorb and desorb organic components quantitatively without the adsorbed substances changing.

When selecting and arranging filter and adsorber materials are u. a. their flow resistance and Temperature dependence of the adsorption performance consider. By cooling the adsorbent  the adsorption performance can be increased. Is limits the volume-related capacity, so the Extension of the sampling time by changing the Filter adsorber unit are made possible. This can e.g. B. by manual replacement or by time timer-controlled changeover to additional filter / ad sorber units (cartridges) with the help of reusable veins tilsystemen happen like this in itself from the adsor ber technology is known.

Filling the first section with quartz cotton has proven to be optimal, with 10-50 g quartz cotton being stuffed per 100 cm³ volume of the first section. The second section was completely filled with the adsorbent Amberlite® XAD-2 from E. Merck, Darmstadt. The unit was operated at a temperature between 25 ° C and 150 ° C. An outlet opening 13 adjoins the cartridge 10 and opens into the base of a cooler 15 .

The residual gas flows through the cooler 15 . The condensate and water that separate out are collected in the condensate column ben 16 . The liberated gas flows through line 17 to pump 19 , which line can also be interrupted by a shut-off valve 20 .

The drying can be intensified by removing the residual moisture with the aid of a desiccant, e.g. B. silica gel, in a drying tower 21st The dimensioning of the cooler and drying tower is based on the expected sample gas conditions, including the temperature and the water content of the partial gas stream.

Depending on the specified suction conditions (total volume, Volume flow depending on the Detection limits and the sample gas conditions as well as Randbe conditions of the measurement task, e.g. B. Compliance with isokinetics)  are gas delivery systems with volume flow control in a range of approx. 0.1 to 10 m³ / hour - below Standard conditions - applicable. From the suction device For example:

• - vacuum membrane pump,
• - dry-running or oil-vacuum rotary vane pumps,
• - ejector pumps,
• - Side channel blower

The volume flow can be regulated manually by the shut-off valve 20 with the aid of a pressure meter 18 .

In addition, an automatic valve control on the suction nozzle of the pump 19 depending on a previously set volume flow, for. B. a differential pressure measurement on a measuring orifice, hot wire anemometer, flow meter with electromagnetic Schaltkontak th or the like possible. The volume flow control can also be computer-aided, the dependence on changing differential pressure in the channel being able to be recorded as a parameter via a corresponding anemometer or pitot tube.

The determination of the suction volume taking into account the air throughput and the temperature at the gas meter 22 is carried out with an additional Lich switched temperature meter 23rd Such Meßin instruments are known per se and are also used in the devices according to the prior art. It should be noted that the individual parts 13 to 23 are known per se and can also be varied depending on the measuring task.

Depending on the measurement task, the sample gas volume is on a be agreed pressure, water content and a certain temp  standardized. The reference to 1013 is very common hPa, 0 ° C, dry, selected. With most volume moods is a subsequent standardization of the measurement gas volume necessary. Therefore, with previous Drying the sample gas, the sample gas temperature and the Pressure against which the volume determination system works tet, can be determined in parallel. Accordingly, the water content of the sample gas to be known.

Sampling is carried out by inserting a fresh glass inner tube 8 into the probe 3 . Attention is paid to 100% tightness against the intake of false air. Depending on the sample gas temperature, gland packing with mineral fiber or Teflon cord can be used as a seal; Flat pinch seals or oil seals are also used.

The probe 3 is positioned at the measuring point by moving within half of the insertion 5 . The stopcock 14 is placed directly on the probe tube, which remains closed until the start of the measurement. After all the other parts of the device have been installed, the tightness of the equipment is checked, at a vacuum of about 500 mbar. This must not go up for a minute.

During the now following sampling, suction volum flow rate and sample gas temperature at the volume determination system system registered at regular intervals.

After sampling is completed, the pump 19 is switched off and the shut-off valve 14 on the probe tube is closed. Aspirated and possibly supplied diluent gas volumes are registered. Accumulated condensate in the condensate flask 16 can be pumped out and discarded.

The cartridge 10 is separated from the system, the glass is closed and protected against exposure to light. The filter and adsorbent contained in the two departments of the cartridge is processed by known further processing, usually estraction, digestion, cleaning, gas chromatographic analysis in a laboratory. Comparative measurements have shown that practically no relevant amounts of adsorbate remained in the remaining parts of the apparatus, as far as the amounts of PCDD and PCDF to be analyzed are concerned.

The measuring apparatus is therefore ready for use again as soon as a new cartridge is inserted and the glass inner tube 8 has been replaced. It turns out that the interior of the cartridge is quite damp, since it is kept at a temperature below the dew point of the water. However, this moisture does not affect the measurement result negatively, but positively. The amount of gas flowing over many hours then forms a balance of residual moisture within the adsorbent inside the cartridge.

It should be noted that with very negligible or very low dust content, on which the volatile Can bind substances during filtering Dust filter can also be omitted. Sampling mesonde can with appropriate conditions at the Tapping point can also be omitted. Is too possible to choose the order: cartridge, probe, Trigger devices.

The advantages of the method and the Vorrich used to carry out the procedure can be summarized as follows:

• (a) The process is almost independent of the  Exhaust gas temperature (0 to 1000 ° C), from the water content (up to over 300 g / m₃) and dust content (up to 1 g / m₃) of the exhaust gas.
• (b) The sampling apparatus is easy to handle.
• (c) The effort is comparable to that of dust measurement The time expenditure on site is reduced and with it the sampling costs. The analyzes Costs also decrease because of the extracts only from one or a maximum of two collection phases have to be manufactured.
• (d) For replacing the glass probe tube and glass car ink with dust filter and adsorber resin for one subsequent measurements are only required a few Minutes; this eliminates the need for time-consuming cleaning the equipment on site z. B. with flammable solution average after a sample has been taken.
• (e) Since the surfaces of the sampling heap in contact with the exhaust gas only on the glass probe tube and limited the glass cartridges, the possibility becomes secondary contamination or the blank value the apparatus minimized.
• (f) Instead of up to five different collecting matrices traditional methods (probe tube, dust filter, condensate, adsorber, rinsing solution) is here only one collection matrix (cartridge with dust filter and Adsorberharz) and if necessary. the probe tube for the Ana to consider.
• (g) The glass cartridge with dust filter and adsorbent can e.g. B. in ¹³C-PCDF / D standards spiked form of Analytical laboratory to be sent; a spiking of the Ap On-site repair is no longer necessary.  
• (h) The cost of the sampling equipment is e.g. T. um many times lower than the previous ones known methods.

Claims (9)

1. A method for sampling and processing samples from exhaust gases containing medium and low volatility substances, in particular polychlorinated dibenzo (p) dioxins (PCDD) and polychlorinated dibenzofurans (PCDF), in a gas or aerosol phase, with the following process steps

• (a) withdrawing a partial flow and introducing it into a separation area in which the substances to be examined are subjected to a separation process and fixed in a dust-bound form or in the condensate,
• (b) after the end of sampling, extracting the separated substances and introducing them into an analysis device, characterized in that the partial flow through an inert dust filter area and then through an area filled with an absorbent, the medium and low volatility organic substances also is quantitatively adsorbed from the condensate, conducted and then the organic substances adsorbed in the dust filter area and on the absorbent are analyzed.

2. The method according to claim 1, characterized in that that before entering the filter area of the Partial gas flow cooled to a temperature T <200 ° C. becomes.   3. Device for performing the method according to claim 1 or 2 with a temperature-resistant sampling probe ( 3 ), which has a receiving opening ( 2 ) and a gas line ( 8 ), characterized by
a cartridge ( 10 ) which can be connected to the gas line ( 8 ) and has two compartments ( 11 , 12 ) and an outlet opening, from which the compartment ( 11 ) which has passed first is filled with an inert, insoluble filter material
and in which the second section ( 12 ) is filled with a synthetic adsorber resin which also adsorbs medium and low volatile organic substances quantitatively from the condensate,
and through a line connecting to the outlet opening with a connected suction pump ( 19 ). 4. The device according to claim 3, characterized in that the gas line ( 8 ) can be cooled. 5. The device according to claim 3, characterized in that the sampling probe ( 3 ) is combined with a separating device (cartridge 10 ). 6. The device according to claim 3 or 5, characterized characterized in that synthetic adsorbents, insoluble polystyrene polymers and / or acrylates be used. 7. The device according to claim 6, characterized in that that as Adsorberharz® a styrene-divinylbenzene copoly Amberlite® XAD-2 or Amberlite® XAD-4 is used. 8. The device according to claim 6, characterized in that as an adsorbent resin, an acrylic acid ester of the type Amberlite® XAD-7 or Amberlite® XAD-8  is used. 9. Device according to one of the preceding claims 3 to 8, characterized in that the inert filter area ( 11 ) is filled with stuffed quartz wadding, glass fibers, glass fiber flat filters or membrane filters.