EP2986977A1 - A gas analysis apparatus and method for testing gas emissions from a manufactured product - Google Patents
A gas analysis apparatus and method for testing gas emissions from a manufactured productInfo
- Publication number
- EP2986977A1 EP2986977A1 EP14785767.6A EP14785767A EP2986977A1 EP 2986977 A1 EP2986977 A1 EP 2986977A1 EP 14785767 A EP14785767 A EP 14785767A EP 2986977 A1 EP2986977 A1 EP 2986977A1
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- European Patent Office
- Prior art keywords
- gas
- sample
- chamber
- electro
- temperature
- Prior art date
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—Specially adapted to detect a particular component
- G01N33/0047—Specially adapted to detect a particular component for organic compounds
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
- G01N1/2214—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling by sorption
- G01N2001/2217—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling by sorption using a liquid
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2226—Sampling from a closed space, e.g. food package, head space
- G01N2001/2241—Sampling from a closed space, e.g. food package, head space purpose-built sampling enclosure for emissions
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Food Science & Technology (AREA)
- Combustion & Propulsion (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
A gas analysis apparatus for testing gas emissions from a manufactured product, comprises or is arranged to be connected to, a chamber arranged to contain and/or receive gas emitted from a sample of the manufactured product to be tested, an electro-chemical cell, and a transmission conduit arranged to transmit a sample of gas emitted from the product from the chamber to the electro-chemical cell. The electro-chemical cell is arranged to generate a signal indicative of the concentration of a particular gas in the gas sample. The apparatus further comprises, or is arranged to be in communication with, an electronic controller which processes the signal and generates an output indicative of the amount of gas emitted from the product over a predetermined time. The apparatus may be used for testing formaldehyde emissions from wooden, wood based or fibre based products.
Description
A GAS ANALYSIS APPARATUS AND METHOD FOR TESTING GAS EMISSIONS FROM A MANUFACTURED PRODUCT
Field of the Invention
This invention relates to a gas analysis apparatus and method for testing gas emissions from a manufactured product. In one example, the invention relates, to an apparatus and method for testing formaldehyde emissions from processed wood based products such as fibreboard, particle board and plywood.
Background
The emission of gases from products, such as those used within buildings is becoming increasingly controlled.
While scientists and legislators are examining other gases, formaldehyde has been regulated for over 20 years and has been implicated in "Toxic house syndrome". Formaldehyde is also listed by the WHO as a "known carcinogen".
Many materials emit formaldehyde - both man made and natural products emit formaldehyde however, the focus of formaldehyde emission legislation in the wood industry has been on materials traditionally made using formaldehyde based glues. These products include but are not limited to, MDF, particleboard, plywood, laminated veneer lumber, glued lumber; finger jointed solid wood, and wood flooring.
Formaldehyde based glues have traditionally been the main glues used in the manufacture of these products because they are relatively cheap and provide the required product characteristics.
An issue for the wood based materials industry is that formaldehyde is emitted from products made from formaldehyde based glues for the lifetime of the product. The emission of formaldehyde follows a decay curve and so is highest close to time of production, decaying continuously over the entire product life. However, some materials will always exceed international limits while others will always meet the most stringent standards. Some may start life exceeding a given limit and formaldehyde emission will decay such that the product then meets the standard some time after production.
It is a desire of the various wood materials and other industries to find testing systems sufficiently fast and accurate that testing can be conducted close to production time and using known decay curves to predict point of sale values. More rapid testing will enable more timely response to test results and will enable quicker corrective action in the case of non-conforming product and also a more precise production control. This will reduce production costs and reduce glue usage and save fossil fuel.
The present test methods used to test emission of formaldehyde fall into two main groups:
A) Reference methods: usually small chambers, normally around 1 m3, in which samples are placed in controlled humidity, temperature, pressure, air turnover, and controlled velocity of air passing over the sample surface. The air in these chambers is sampled at intervals and the emission value is determined when a particular steady state is reached; and
B) Secondary production methods: these relate, by correlation, to the reference methods and are used within production facilitates to monitor either incoming materials in, for example, a furniture manufacturing facility, or the actual production of the base products at, for example, an MDF factory.
Most of the present test methods incorporate processes of analysing formaldehyde dissolved into water. The formaldehyde can be either emitted formaldehyde or, in the case of tests conducted to European standard EN120, formaldehyde is extracted using solvents and then dissolved into water. In the case of En120 the toluene used during the extraction process has documented health and safety issues and its use must be carefully controlled such that the technicians are protected from contact with the toluene in liquid or vapour phase. The steps of the processes for all these standards can be summarised as follows:
A. Dissolve formaldehyde into water
B. Dilute to fixed volume
C. Mix with standard chemicals
D. Carry out chemical reaction for a fixed time and a fixed temperature - (normally about 15 minutes).
E. Allow the chemical reaction to complete for a fixed time as cooling to room temperature occurs ( normally about 1 hour)
F. Test the resulting reaction products by colour spectro-photometer
G. Determine the concentration from the spectro-photometer based on calibrations previously conducted on the particular instrument.
In Europe, a standard test has been developed called EN717-2, which also utilises the above method to determine the emission from the test sample over a four hour period. The method can be summarised:
a. A heated chamber or chambers of about four litres each at 60 °C.
b. Air passes through the chamber at 60 L/hour.
c. Air pressure is maintained between 1000 and 1200 Pa in the chamber. d. Wood based material samples of 0.04m2 surface area are each placed in each chambers for four hours and the air exiting from the chambers is bubbled through four pairs of water containers (impingers). Valves switch from one pair of containers to the next giving four one-hour samples of formaldehyde dissolved in water.
e. Chemical solutions are mixed with sub samples of this water and the resulting reaction with the formaldehyde produces a yellow colour, the depth of which can be determined using a spectrophotometer. Higher formaldehyde concentrations give a deeper colour.
f. The concentration of the solution and the total volume of the solution are used to mathematically determine the total formaldehyde emitted from the sample over each hour. Object of the Invention
It is therefore an object of the invention to provide an apparatus and method for testing gas emissions from manufactured products which overcomes or at least ameliorates one or more disadvantages of the prior art, or alternatively to at least provide the public with a useful choice.
Further objects of the invention will become apparent from the following description. Summary of Invention
Accordingly in one aspect the invention may broadly be said to consist in a gas analysis apparatus for testing gas emissions from a manufactured product, the
apparatus comprising, or arranged to be connected to, a chamber arranged to contain and/or receive gas emitted from a sample of the manufactured product to be tested, an electro-chemical cell, and a transmission conduit arranged to transmit a sample of gas emitted from the product from the chamber to the electro-chemical cell, the electro-chemical cell being arranged to generate a signal indicative of the concentration of a particular gas in the gas sample, the apparatus further comprising, or being arranged to be in communication with, an electronic controller arranged to process the signal and to generate an output indicative of the amount of the gas emitted from the product over a predetermined time.
Preferably the apparatus is operative to transmit multiple gas samples through the electro-chemical cell over a predetermined time period, such that the cell generates a plurality of gas concentration signals, the electronic controller being operative according to an algorithm which processes the plurality of gas concentration signals to determine the total volume (or weight) of gas emitted from the product sample over the predetermined time period. Preferably the algorithm is operative to integrate the plurality of gas concentration signals to determine the total gas emitted from the product sample over a predetermined period of time. In one example, the chamber comprises a testing chamber arranged to receive gas from a sample of the manufactured product remote from the apparatus. In another example, the chamber comprises a testing container in which the sample of the manufactured product is contained in use. In a yet further example, the chamber comprises a sample chamber in communication with a testing chamber remote from the apparatus. This latter example enables the apparatus to receive gas from a sample of the manufactured product contained in a remote apparatus. Thus, the apparatus in accordance with the invention may comprise a modification or add-on to an existing apparatus. Preferably at least part of the transmission conduit is temperature controlled so as, in use, to be at a temperature at which no condensation occurs in the transmission conduit. Preferably a conduit heater line is provided arranged to control the temperature in the transmission conduit. This may be particularly beneficial where the apparatus comprises or is in communication with a remote sample chamber linked to the testing chamber via the transmission conduit.
Preferably the sample of the manufactured product is arranged to be at a temperature equal to or above 50 °C and in one example, equal to above 60 Ό. Testing at temperatures substantially above room temperature results in more gas being emitted with the cell therefore likely to produce more accurate results.
Preferably the apparatus comprises, or is arranged to be in communication with, a source of pressurised gas arranged to force the gas sample through the electrochemical cell.
A pump may be provided to pump the gas sample through the electro-chemical cell.
Preferably a mass flow controller is provided to control the flow rate of gas through the sample chamber. Preferably the mass flow controller produces an output signal indicative of the gas flow rate through the mass flow controller. In the case of an analogue output signal, the signal may be converted into a digital signal prior to or within the electronic controller.
Preferably at least the testing chamber and the electro-chemical cell are contained within a temperature and/or humidity controlled housing. The housing may be provided for this purpose with a temperature and/or humidity sensor, a heater and a fan. The temperature and/or humidity inside the housing may be controlled to be above the normal dew point for the gas flowing through the housing. Preferably the testing chamber is provided with a relative humidity sensor arranged to provide a relative humidity signal to the electronic controller, the electronic controller being operative to generate a warning signal if the relative humidity the testing chamber is too high or too low. The electronic controller may be operative to terminate the gas emissions test if the relative humidity exceeds or falls below predetermined thresholds.
Preferably at least part of the transmission conduit is contained within the temperature controlled housing.
Preferably said part of the transmission conduit within the temperature controlled housing is arranged to enable gas in the transmission conduit to reach, or be maintained at, the temperature inside the housing. Preferably the electro-chemical cell assembly comprises an electrochemical cell, an electronic cell controller (which may comprise at least one of a signal amplifier, computer and display) and an additional circuit to allow the electronic cell controller to communicate with the electronic controller. If required, the additional circuit may comprise an analogue to digital converter to convert the output from the electro- chemical cell into a digital output.
The electro-chemical cell assembly may comprise temperature compensation means, for example in its software, to compensate for a temperature differential between the gas sample and the ambient temperature within the housing. Preferably however, the temperature and/or humidity of the temperature controlled housing is controlled such that there are no, or negligible, temperature and/or humidity differences between the components of the apparatus. Thus in normal usage, the temperature compensation means would not be used or required, or, if used only compensates for relatively small temperature differences from the normal test temperature.
Preferably the apparatus comprises an in-situ calibration system arranged to calibrate the apparatus when in a calibration mode.
Preferably the calibration system is mounted on or in the temperature controlled housing.
The calibration system may comprise a calibration chamber arranged to contain a predetermined volume and concentration of the gas to be tested, or contain a material which will generate a specific concentration of the gas at a certain temperature, and to be in communication with the electro-chemical cell a valve being provided to isolate the calibration chamber from the electro-chemical cell during normal use of the apparatus, and to isolate the sample chamber from the electro-chemical cell during the calibration mode, the electro-chemical cell being arranged to generate a signal indicative of the measured concentration of gas emitted from the calibration chamber during the calibration mode, the electronic controller being arranged to compare the
measured concentration with the known concentration of the gas to be monitored in the calibration sample and to generate a compensation factor signal indicative of any difference between the measured and the known concentrations. Preferably the temperature controlled housing comprises two sub housings, one of which contains at least the testing chamber and the electro-chemical cell, the other of which contains at least the calibration chamber. Preferably the sub housings are isolated from one another such that if one sub-housing is accessed, this does not substantially affect the temperature and/or humidity inside the other housing.
An optional gas filter may be provided in the transmission conduit prior to the electrochemical cell to filter a gas or gases other than the gas to be tested. The gas filter, in one example, may be a selective VOC filter. Preferably the gas filter is provided between the testing chamber and the electro-chemical cell.
According to a further aspect, the invention may broadly be said to consist in a method of testing gas emissions from a manufactured product, the method comprising providing a chamber arranged to contain and/or receive gas emitted from a sample of the manufactured product to be tested, transmitting the gas from the chamber to an electro-chemical cell via a transmission conduit, controlling the electro-chemical cell to generate a signal indicative of the concentration of a particular gas in the gas sample, and using an electronic controller to process the signal and to generate an output indicative of the amount of the gas emitted from the product over a predetermined time.
According to another aspect, the invention may broadly be said to consist io-a-of gas analysis apparatus for testing gas emissions from a manufactured product, comprising a sample chamber in which a sample of the product to be tested is placed in use, and a temperature controlled housing in which a testing chamber and an electro-chemical cell are located, the sample chamber being in fluid communication with the test chamber via at least one temperature controlled transmission conduit such that the test chamber receives temperature controlled gas from the sample chamber, the apparatus further comprising an electro-chemical cell system in the housing and being in fluid communication with the testing chamber so as to receive a gas sample from the testing chamber and to generate an electrical signal indicative of the concentration
of at least one gas in the gas sample, the apparatus further comprising, or being arranged to be in communication with an electronic controller operative to receive the electrical signal and generate an output indicative of the total gas emitted from the product over a predetermined time.
According to a further aspect, the invention may broadly be said to consist in a formaldehyde gas analysis apparatus for analysing formaldehyde gas emissions from a wooden, wood based, or fibre based product, the apparatus comprising, or being arranged to be in communication with, a sample chamber arranged to contain a sample of the product to be tested, and an electro-chemical cell in communication with the sample chamber via a transmission conduit, the apparatus comprising, or being connected to, means to generate a gas flow to transmit a sample of gas emitted from the product to be tested from the sample chamber to the electro-chemical cell the cell being operative to generate a signal indicative of the concentration of formaldehyde in the sample of gas, the apparatus further comprising, or being arranged to be in communication with, an electronic controller which receives the signal, and processes the signal according to an algorithm to generate an output indicative of the total amount of formaldehyde emitted from the product to be tested, over a predetermined test period.
Further aspects of the invention, which should be considered in all its novel aspects, will become apparent from the following description.
Drawing Description
A number of embodiments of the invention will now be described by way of example with reference to the drawing which is a schematic of an apparatus for testing gas emissions from a manufactured product, in accordance with the invention.
Detailed Description of the Drawings
Throughout the description like reference numerals will be used to refer to like features in different embodiments.
A gas analysis apparatus 1 for testing gas emissions from a manufactured product broadly comprises or is arranged to be connected to, a sampling system 3 comprising at least one sample chamber 5 arranged to contain a sample of the manufactured product. The sample chamber(s) 5 is connected to a testing chamber 7 via at least
one transmission conduit 9 such that gas emitted from the sample in the sample chamber 5 passes via the gas conduit 9 to the testing chamber 7. An electrochemical cell system 1 1 is in fluid communication with the sampling system 3, and in particular the testing chamber 7, and is arranged to receive a sample of the gas from the testing chamber 7 and to generate an electrical signal indicative of the concentration of at least one gas in the gas sample. An electronic controller is provided and is operative to receive and process the electrical signal and generate an output indicative of the amount of the gas emitted from the product over a predetermined time.
In one example, the apparatus 1 is arranged to receive a gas sample from a sample chamber of an existing gas emission testing apparatus 12. An example of such an apparatus 12 is marketed under the name TimberTest GA5000 or Grecon GA5000 and typically comprises a housing containing two sample chambers 5A, 5B in which samples of the product to be tested are placed. The apparatus 12 is connected to, or comprises, a source of pressurised gas, usually air, which is pumped to the sample chambers 5A, 5B through air lines 15 by pumps 17. One way valves 19 may be provided in the airlines 15 as required. A mass flow controller 21 is provided in each air line 15 to be able to control and measure the flow rate of air to each sample chamber 5A, 5B. Apparatus 12 further comprises an electronic controller 14 which may comprise a personal computer or the like to control the functioning of apparatus. Such an apparatus has been previously used for conducting a gas emissions test as per the Standard EN717-2 Test. The apparatus 1 is arranged, in this example, to extract gas from the sample chambers 5A, 5B of the existing testing apparatus 12, and to transmit the extracted gas to a testing system of the apparatus 1.
Each sample chamber 5A, 5B of the apparatus 12 is therefore connected to the testing chamber 7 of the apparatus 1 by a respective temperature controlled transmission conduit 23, each of which is provided with a manifold and five valves 25, a subsequent valve 27, and a pressure sensor 29. The transmission conduits 23 connect the sample chambers 5A, 5B to the testing chamber 7 such that gas extracted from each sample chamber 5A, 5B is received in the testing chamber 7 of the apparatus 1.
The apparatus 1 comprises a temperature and/or humidity controlled housing 31 inside which the testing chamber 7 is mounted. The temperature and/or humidity in the housing 31 is controlled via a temperature and/or humidity sensor 33, heater 35 and a fan 37.
The electro-chemical cell system 11 located in the temperature controlled housing 31 comprises an electro chemical cell 39 and an associated cell controller, which may include a printed circuit board and electronic data processor, and is arranged to receive a sample of gas from the testing chamber 7 via a transmission conduit 41. The transmission conduit 41 is provided with a three way valve 43 and a VOC gas filter 45 to filter the sample of gas for certain chemicals, prior to the gas reaching the electro-chemical cell 39. The cell system is protected with a transmitter 42 arranged to provide relative humidity and/or temperature values in or at the cell 39 to the electronic controller 41.
The electro-chemical cell system 11 is arranged to generate a signal indicative of the concentration of a particular gas in parts per million or mg/m3 of air. This signal is transmitted to the electronic controller 14 which processes the signal and converts it into an output indicative of the total gas emitted by the sample for a predetermined time period. The signal may alternatively be an analog signal such as voltage or mA, for example.
All of the active components of the apparatus 1 , 12 may be controlled by the electronic controller 14, including the mass flow controllers 21 , valves 25, 27, 43 the temperature and humidity in the temperature controlled housing 31 , and the electrochemical cell system 11. The controller 14 can therefore control the flow rate, flow initiation and flow termination of gas from either sample chamber 5A, 5B to the testing chamber 7, and from the testing chamber 7 to the cell system 1 1.
The apparatus 1 may further comprise an in-situ calibration system comprising a calibration chamber 47 connected to three way valve 43 via a calibration conduit 49. The calibration chamber 47 is mounted in the temperature controlled housing 31 and is arranged to contain a predetermined known volume and concentration of the gas to be tested (or contain a material that generates a known concentration of
formaldehyde gas). In a calibration mode, the electronic controller 14 controls three way valve 43 to prevent flow from the testing chamber 7, and to allow flow of gas from the calibration chamber 47 to the electro-chemical cell system II. The cell system II provides a signal indicative of the concentration of the gas from the calibration chamber 47 which can be processed by the electronic controller 4 and compared to the known concentration. This comparison can be used by the electronic controller 14 to determine the accuracy of the output of the cell system II, and to apply a compensation factor as required. This calibration step can be conducted regularly, under manual or automatic control of the controller 14. It is envisaged that the apparatus 1 may enter a calibration mode at least once per hour for example.
The apparatus 1 therefore broadly comprises the following:
A) Sample System
A gas conduits 23 stream is taken from the existing apparatus 12 and passed via heated transmission into the temperature controlled housing 31. The standard EN717-2 (used by existing apparatus 12) prescribes an overpressure of 1000 to 1200Pa above ambient. Apparatus 1 utilises this overpressure by opening one or more valves allowing a small sample of gas from one or more of the sample chambers 5A, 5B to pass to the temperature controlled housing 31 . The transmission lines 23 are heated to the point where they pass into the temperature controlled housing 31 such that no condensation occurs in the transmission conduits 23. The transmission conduits 23, 41 within the temperature controlled housing 31 allow the gas sample to reach the operating temperature within the temperature controlled housing 31 . The gas passes into the testing chamber 7 which may comprise, in one example, a glass vial of about 20iml_. A sub-sample of this gas is pumped into the electro-chemical cell system II. B) Electro-chemical Cell System
The temperature controlled housing 31 also contains the electro-chemical cell system 1 1 , which preferably comprises three parts:
a) the electro-chemical cell 39
b) a signal amplifier, electronic controller and display for programming existing apparatus 12
c) Optionally an additional circuit board allowing communication with the electronic controller 14 of apparatus 12. This additional circuit board may convert an analogue output signal to a digital signal.
C) Temperature Controlled Housing
The housing 31 is temperature controlled and may comprise an access panel or door with a stop switch. This allows temperature control at a given temperature, which must be above the normal dew-point for the air stream, but within the operational range of the electro-chemical cell. The temperature control also allows relatively precise measurements since, while the electro-chemical cell system II has temperature compensation built into the software, more precise results are produced when calibration and testing is carried out at one temperature and when there are only relatively small temperature differences between components.
D) Calibration System The apparatus 1 incorporates a calibration chamber 47 which may be a calibration tube for example, for calibration during the normal test of the material sample.
Additionally, a primary calibration can be carried out by placing a known volume and concentration of, for example, formaldehyde in the sample chamber 5A or 5B, rather than a test sample, and carrying out a normal test. The primary calibration will allow the test to be incorporated into national test standards, which would require calibration against primary standards.
E) Filtering system
The filtering system may include a VOC filter for removing, or reducing, the concentration of high VOC in the gas stream, prior to reaching the cell system II. These high VOCs may interfere with the cell 39 and produce an unreliable output from the cell 39.
In one example, the electro-chemical cell system II comprises an on-board computer integrated into a circuit board, which reports results in parts per million or mg/m3 of air. However, the EN717-2 test requires the result to be in terms of the total formaldehyde emitted for each hour for the four hours of the existing test.
The electronic controller 14 is thus operative according to an algorithm which integrates the results so in effect simulating the gathering of the formaldehyde into the water by the standard method of the existing test. The integration is the area under the curve for the graph of formaldehyde concentration in air on the y-axis and the volume of air which has passed through the testing chambers 5A and/or 5B during the interval on the x axis. The equation for this for steady state would be: Total formaldehyde emitted = Flow rate * time * concentration.
However since the emission is not steady state and the interval is not always the same, because the cell 39 takes longer to clear for large emission results, integration is used to calculate the total emitted formaldehyde. Since the results for the EN717-2 test are presented for each hour, integration is determined for each hour taking into account that the air concentration determination does not fall exactly on the hour.
These calculations are carried out, for example, within the electronic controller 14.
The calculation of total formaldehyde emitted from the sample requires temperature, and pressure corrected gas flow readings as digital data. The mass flow controllers 21 provide this data. These instruments produce analog outputs and can be controlled with analog inputs. The analog output signals are converted using standard industrial automation products into digital values via a conversion system. This enabled calibrated airflow values as needed by the integration algorithm.
Communication between the electro-chemical cell computer and the electronic controller 14 requires a digital value from the cell system II to input the data into the
electronic controller 14. This is enabled via an interface board between the cell computer and the electronic controller 14.
The apparatus 1 can be calibrated by "primary methods", utilising formaldehyde solutions of known concentration and volume. During primary calibration a formaldehyde solution is placed inside one of the sample chambers 5A, 5B and a normal test sequence is conducted. The output from the apparatus 1 is compared with the known amount of formaldehyde put into the sample chamber 5A, 5B. From these two numbers a calibration factor is derived. However, the formaldehyde electro- chemical cell 39 ideally requires regular calibration over the duration of the test and this primary calibration process is time consuming, requiring trained technical staff and is not suitable for daily use.
The apparatus 1 advantageously provides an in-situ calibration system comprising a calibration tube 47 containing a formaldehyde emitting material. The tube 47 gives a certain value of formaldehyde concentration at given temperatures when a fixed volume of gas is taken from the tube 47.
This tube 47 is incorporated into the apparatus 1 such that the electro-chemical cell 39 samples gas either from the testing chamber 7 or the calibration tube 47 depending on a control signal from the electronic controller 14. In one example this calibration is conducted every hour.
The electrochemical cell 39 may produce a signal in response to gases other than the one being tested. The cell software and hardware reduces this effect, though large concentrations of other gases may still produce an over reading.
To reduce or negate this effect the apparatus 1 may incorporate filter 45 to reduce the interference gases.
This filter 45 may only be needed on material sampled close to production date, as most interfering gases decay rapidly after production.
The filter 45 may also reduce the formaldehyde value. However this effect is accounted for by reference to the calibration system 47.
Formaldehyde is highly soluble in water, and if condensation occurs in the transmission lines 23, the formaldehyde may be retained in the moisture. This can reduce the result in the hour of the test during which condensation occurs, and may increase in subsequent hours if the dew point in the air stream reduces.
To prevent this occurring, the apparatus 1 at least uses heated transmission lines 23 leading to the temperature controlled housing 31 , the housing 31 being maintained at a temperature which is above the dew point, but within the operating range of the cell 39.
An RH sensor inside the testing chamber 7 allows the electronic controller 14 to stop the test if high or low RH occurs. Although the electro-chemical cell system 11 has temperature compensation built into the software, more accuracy is obtained if all parts are at the same temperature. Also the calibration tube 47 should be at this same known temperature so that the reference value can be determined. The temperature controlled housing 31 is designed such that the temperature in the inner chamber housing does not alter during filter 45 or calibration tube 47 replacement.
The temperature controlled housing 31 therefore comprises two chambers with air circulating around them via the fan. When the outer chamber, which houses the calibration tube 47, is opened, a magnetic switch stops the fan and heater preventing over-heating or cold air entering the inner chamber in which the electro-chemical cell 39 and testing chamber 7 are housed. The two chambers are maintained at a desired temperature using a thermometer §4- 33 with a transmitter, which feeds a signal to the electronic controller 14. A small DC heater is controlled using a PID feedback loop from the thermometer temperature information. The temperature may be selectable via menus operated from electronic controller 14.
In another example, the apparatus 1 may be a standalone testing apparatus, that is, an apparatus not designed to piggyback onto an existing testing apparatus 12. The existing testing apparatus 12 is currently widely used, and it may be advantageous to have an apparatus 1 that can be used with existing apparatus 12. However, it is also possible to provide the apparatus 1 with all the components necessary for the apparatus 1 to be autonomous. For example, the sampling chamber(s) 5A, 5B, the air supply pump(s) and control valve(s), and the mass flow controller(s) may all be provided on the apparatus 1 , either in the temperature controlled housing 31 , or in a separate housing. Likewise, the electronic controller 14 may be provided as part of the apparatus 1. The electronic controller 14 may also be remote from the apparatus, with data being transmitted between the apparatus 1 and the electronic controller 14 via a wired or wireless link.
Whilst the above has been described in relation to testing Formaldehyde emissions, it is envisaged that apparatus and methods in accordance with the invention can be used to test emissions of any desired gas. For example, the wood industry is now affected by the legislation which limits the emission levels of other gases, many of which gases can also be measured by an electro-chemical cell. The above has also been described in relation to testing emissions from wooden or wooden particle based materials such as particleboard, plywood and fibreboard (MDF). However, many other industries are or may be affected by the increasing VOC and Formaldehyde emission legislation. Apparatus and methods in accordance with the invention can therefore also be used to test any other desired material including for example, automotive materials, fabrics, carpet, and cardboard such as food containers for fast food providers for example.
The apparatus 1 and methods in accordance with the invention have been described in relation to testing according to the EN717-2 standard but may have applications in other methods used for testing wood products (not just an EN717-2 type test).
Apparatus and methods in accordance with the invention have a number of advantages over prior art arrangements. These include that:
• Testing is faster - the test sample needs to be placed in the sample chamber 5A, 5B and no further time input is required. In contrast, the prior art process takes about 1 .5 hours to complete after the formaldehyde is collected into water and about 30 minutes of technical time per duplicate test.
· The photo-spectrometry method of testing also requires a degree of technical skill and can only be carried out by relatively precise and trained staff. Testing using the invention requires minimal technical skill. This could therefore extend the use of the existing testing apparatus 12 to allow testing throughout a nightshift when skilled laboratory staff are not normally available.
· The apparatus 1 may be an addition to the existing apparatus 12 and so it is expected that the full length standard testing procedure can also be conducted on the same machine. It is common that factories carry out two levels of test: production control and certification testing. So in the short term at least while the certification process might not allow testing using apparatus 1 , it would be possible to use apparatus 1 for supplemental production control testing. This might add value and allow more precise monitoring of the production by untrained night staff for example. More precise monitoring would allow more precision in the resin use, and the plant operation, resulting in glue savings and less reject product.
· The equipment and materials used have minimal health and safety risks, and those risks that exist are easily managed. This has significant advantage over tests such as the EN120 test which utilises heated toluene to extract free formaldehyde and therefore poses fire, explosion and health risks associated with human contact.
Unless the context clearly requires otherwise, throughout the description, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".
Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention. The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or
collectively, in any or all combinations of two or more of said parts, elements or features. Furthermore, where reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
Claims
1 . A gas analysis apparatus for testing gas emissions from a manufactured product, the apparatus comprising, or arranged to be connected to, a chamber arranged to contain and/or receive gas emitted from a sample of the manufactured product to be tested, an electro-chemical cell, and a transmission conduit arranged to transmit a sample of gas emitted from the product from the chamber to the electrochemical cell, the electro-chemical cell being arranged to generate a signal indicative of the concentration of a particular gas in the gas sample, the apparatus further comprising, or being arranged to be in communication with, an electronic controller arranged to process the signal and to generate an output indicative of the amount of the gas emitted from the product over a predetermined time.
2. The apparatus of claim 1 wherein the apparatus is operative to transmit multiple gas samples through the electro-chemical cell over a predetermined time period, such that the cell generates a plurality of gas concentration signals, the electronic controller being operative according to an algorithm which processes the plurality of gas concentration signals to determine the total volume (or weight) of gas emitted from the product sample over the predetermined time period.
3. The apparatus of claim 2 wherein the algorithm is operative to integrate the plurality of gas concentration signals to determine the total gas emitted from the product sample over a predetermined period of time.
4. The apparatus of any one of claims 1 to 3 wherein the chamber comprises a testing chamber arranged to receive gas from a sample of the manufactured product remote from the apparatus.
5. The apparatus of any one of claims 1 to 3 wherein the chamber comprises a testing container in which the sample of the manufactured product is contained in use.
6. The apparatus of any one of claims 1 to 3 wherein the chamber comprises a sample chamber in communication with a testing chamber remote from the apparatus.
7. The apparatus of claim 6 wherein the apparatus is arranged to receive gas from a sample of the manufactured product contained in a remote apparatus.
8. The apparatus of any one of the preceding claims wherein at least part of the transmission conduit is temperature controlled so as, in use, to be at a temperature at which no condensation occurs in the transmission conduit.
9. The apparatus of claim 8 wherein a conduit heater line is provided arranged to control the temperature in the transmission conduit.
10. The apparatus of claim 8 or claim 9 wherein the sample of the manufactured product is arranged to be at a temperature equal to or above 50 °C and in one example, equal to above 60 °C.
1 1. The apparatus of any one of the preceding claims comprising, or arranged to be in communication with, a source of pressurised gas arranged to force the gas sample through the electro-chemical cell.
12. The apparatus of claim 1 1 wherein a pump is provided to pump the gas sample through the electro-chemical cell.
13. The apparatus of any one of the preceding claims wherein a mass flow controller is provided to control the flow rate of gas through the sample chamber.
14. The apparatus of claim 13 wherein the mass flow controller produces an output signal indicative of the gas flow rate through the mass flow controller.
15. The apparatus of any one of the preceding claims wherein at least the testing chamber and the electro-chemical cell are contained within a temperature and/or humidity controlled housing.
16. The apparatus of claim 15 wherein the housing is provided for this purpose with a temperature and/or humidity sensor, a heater and a fan.
17. The apparatus of claim 15 or 16 wherein the temperature and/or humidity inside the housing is controlled to be above the normal dew point for the gas flowing through the housing.
18. The apparatus of any one of the preceding claims wherein the testing chamber is provided with a relative humidity sensor arranged to provide a relative humidity signal to the electronic controller, the electronic controller being operative to generate a warning signal if the relative humidity the testing chamber is too high or too low.
19. The apparatus of claim 18 wherein the electronic controller is operative to terminate the gas emissions test if the relative humidity exceeds or falls below predetermined thresholds.
20. The apparatus of claim 15 wherein at least part of the transmission conduit is contained within the temperature controlled housing.
21. The apparatus of claim 20 wherein said part of the transmission conduit within the temperature controlled housing is arranged to enable gas in the transmission conduit to reach, or be maintained at, the temperature inside the housing.
22. The apparatus of any one of the preceding claims wherein the electrochemical cell assembly comprises an electrochemical cell, an electronic cell controller (which may comprise at least one of a signal amplifier, computer and display) and an additional circuit to allow the electronic cell controller to communicate with the electronic controller.
23. The apparatus of any one of claims 15 to 22 wherein the electro-chemical cell assembly may comprise temperature compensation means, for example in its software, to compensate for a temperature differential between the gas sample and the ambient temperature within the housing.
24. The apparatus of claim 23 wherein the temperature and/or humidity of the temperature controlled housing is controlled such that there are no, or negligible, temperature and/or humidity differences between the components of the apparatus.
25. The apparatus of any one of the preceding claims comprising an in-situ calibration system arranged to calibrate the apparatus when in a calibration mode.
26. The apparatus of claim 25, when dependent on claim 15, wherein the calibration system is mounted on or in the temperature controlled housing.
27. The apparatus of claim 25 or 26 wherein the calibration system comprises a calibration chamber arranged to contain a predetermined volume and concentration of the gas to be tested, or contain a material which will generate a specific concentration of the gas at a certain temperature, and to be in communication with the electrochemical cell a valve being provided to isolate the calibration chamber from the electro-chemical cell during normal use of the apparatus, and to isolate the sample chamber from the electro-chemical cell during the calibration mode, the electrochemical cell being arranged to generate a signal indicative of the measured concentration of gas emitted from the calibration chamber during the calibration mode, the electronic controller being arranged to compare the measured concentration with the known concentration of the gas to be monitored in the calibration sample and to generate a compensation factor signal indicative of any difference between the measured and the known concentrations.
28. The apparatus of claim 15 wherein the temperature controlled housing comprises two sub housings, one of which contains at least the testing chamber and the electro-chemical cell, the other of which contains at least the calibration chamber.
29. The apparatus of claim 28 wherein the sub housings are isolated from one another such that if one sub-housing is accessed, this does not substantially affect the temperature and/or humidity inside the other housing.
30. The apparatus of any one of the preceding claims wherein a gas filter is provided in the transmission conduit prior to the electro-chemical cell to filter a gas or gases other than the gas to be tested.
31. The apparatus of claim 30 wherein the gas filter is a selective VOC filter.
32. The apparatus of claim 30 or claim 31 wherein the gas filter is provided between the testing chamber and the electro-chemical cell.
33. A method of testing gas emissions from a manufactured product, the method comprising providing a chamber arranged to contain and/or receive gas emitted from a sample of the manufactured product to be tested, transmitting the gas from the chamber to an electro-chemical cell via a transmission conduit, controlling the electrochemical cell to generate a signal indicative of the concentration of a particular gas in the gas sample, and using an electronic controller to process the signal and to generate an output indicative of the amount of the gas emitted from the product over a predetermined time.
34. A gas analysis apparatus for testing gas emissions from a manufactured product, comprising a sample chamber in which a sample of the product to be tested is placed in use, and a temperature controlled housing in which a testing chamber and an electro-chemical cell are located, the sample chamber being in fluid communication with the test chamber via at least one temperature controlled transmission conduit such that the test chamber receives temperature controlled gas from the sample chamber, the apparatus further comprising an electro-chemical cell system in the housing and being in fluid communication with the testing chamber so as to receive a gas sample from the testing chamber and to generate an electrical signal indicative of the concentration of at least one gas in the gas sample, the apparatus further comprising, or being arranged to be in communication with an electronic controller operative to receive the electrical signal and generate an output indicative of the total gas emitted from the product over a predetermined time.
35. A formaldehyde gas analysis apparatus for analysing formaldehyde gas emissions from a wooden, wood based, or fibre based product, the apparatus comprising, or being arranged to be in communication with, a sample chamber arranged to contain a sample of the product to be tested, and an electro-chemical cell in communication with the sample chamber via a transmission conduit, the apparatus comprising, or being connected to, means to generate a gas flow to transmit a sample of gas emitted from the product to be tested from the sample chamber to the electrochemical cell the cell being operative to generate a signal indicative of the concentration of formaldehyde in the sample of gas, the apparatus further comprising,
or being arranged to be in communication with, an electronic controller which receives the signal, and processes the signal according to an algorithm to generate an output indicative of the total amount of formaldehyde emitted from the product to be tested, over a predetermined test period.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NZ60955513 | 2013-04-17 | ||
| PCT/NZ2014/000067 WO2014171841A1 (en) | 2013-04-17 | 2014-04-16 | A gas analysis apparatus and method for testing gas emissions from a manufactured product |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP2986977A1 true EP2986977A1 (en) | 2016-02-24 |
| EP2986977A4 EP2986977A4 (en) | 2016-12-28 |
Family
ID=51731654
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP14785767.6A Withdrawn EP2986977A4 (en) | 2013-04-17 | 2014-04-16 | A gas analysis apparatus and method for testing gas emissions from a manufactured product |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP2986977A4 (en) |
| WO (1) | WO2014171841A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104777202B (en) * | 2015-04-17 | 2018-04-03 | 苏州科技学院 | The quick formaldehyde testing equipment of low-power consumption |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5286363A (en) * | 1990-10-18 | 1994-02-15 | Georgia-Pacific Resins, Inc. | Dynamic microchamber for measuring formaldehyde emissions |
-
2014
- 2014-04-16 EP EP14785767.6A patent/EP2986977A4/en not_active Withdrawn
- 2014-04-16 WO PCT/NZ2014/000067 patent/WO2014171841A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| EP2986977A4 (en) | 2016-12-28 |
| WO2014171841A1 (en) | 2014-10-23 |
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