1、BRITISH STANDARD BS 3841-2: 1994 Determination of smoke emission from manufactured solid fuels for domestic use Part 2: Methods for measuring the smoke emission rateBS3841-2:1994 This British Standard, having been prepared under the directionof the Solid Mineral Fuels Standards Policy Committee, was
2、 published underthe authority of the Standards Board and comes intoeffect on 15May1994 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference SFC/11 Draft for comment 92/58575 DC ISBN 0 580 21836 8 Committees responsible for this British Standard The prepar
3、ation of this British Standard was entrusted by the Solid Mineral Fuels Standards Policy Committee (SFC/-) to Technical Committee SFC/11, upon which the following bodies were represented: Association of British Solid Fuel Appliances Manufacturers British Coal Corporation British Foundry Association
4、Department of Health Department of the Environment (Her Majestys Inspectorate of Pollution) Department of Trade and Industry (Warren Spring Laboratory) Low Temperature Coal Distillers Association of Great Britain Ltd. METCOM Solid Smokeless Fuels Federation Amendments issued since publication Amd. N
5、o. Date CommentsBS3841-2:1994 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii Introduction 1 1 Scope 1 2 References 1 3 Electrostatic precipitator method for smoke emission rate measurement 1 4 Dilution tunnel method for smoke emission rate measurement 9 Annex A (in
6、formative) Comparison of results obtained by the dilution tunnel and electrostatic precipitator methods 18 Annex B (informative) Calculation of in-stack concentration 19 Figure 1 General arrangement of electrostatic precipitator 3 Figure 2 Supporting frame of electrostatic precipitator 4 Figure 3 Se
7、ction through skirt of electrostatic precipitator (at bracket position) 5 Figure 4 Electrostatic precipitator positioned for smoke collection 6 Figure 5 Earthing tool for electrostatic precipitator 7 Figure 6 General arrangement of dilution tunnel and sampling train 10 Figure 7 Suggested arrangement
8、 of dilution tunnel filter housing 11 Figure 8 Design of sample nozzle 12 Figure 9 Section through dilution tunnel showing measurement positions for nine-point traverses 15 Table A.1 Comparison of results obtained with fuel A 18 Table A.2 Comparison of results obtained with fuel B 18 List of referen
9、ces Inside back coverBS3841-2:1994 ii BSI 09-1999 Foreword This Part of BS 3841 has been prepared under the direction of the Solid Mineral Fuels Standards Policy Committee. Together with BS 3841-1:1993 it supersedes BS 3841:1972 which is withdrawn. The Clean Air Act 1956 1, modified and extended by
10、the Clean Air Act 1968 2, was introduced to control air pollution in the United Kingdom. Under Section 11 of the 1956 Act, local authorities are empowered, subject to confirmation by the Minister, to set up smoke control areas in which it is an offence to emit smoke from a building. The only defence
11、s against prosecution under the Act are that the smoke is produced from an authorized fuel, that authorized fuels are not available or that the smoke is from an exempted appliance. An exempted appliance is defined by Section 11(4) of the 1956 Act as one which can be operated for burning a fuel other
12、 than an authorized fuel without producing any smoke or a substantial quantity of smoke. An authorized fuel is defined in Section 34(1) of the 1956 Act as a fuel declared by regulations of the Minister to be an authorized fuel for the purposes of this Act. In 1956 a number of classes of solid smokel
13、ess fuel, both manufactured and natural, which pre-dated the Act were declared to be authorized fuels. Subsequent development of other types of manufactured smokeless fuel for domestic purposes demonstrated the need for a standard procedure to establish their potential for smoke emission and to asse
14、ss whether such fuels were suitable for authorization within the terms of the 1956 Act. For this revision, BS 3841 has been divided into two Parts, Parts 1 covering the fuel combustion procedure and Part 2 describing the smoke measurement equipment and its use. The main technical changes form the pr
15、evious edition are as follwos: a) extension of the test procedure to cover brown coal, lignite, peat and wood fuels; b) widening of the permitted tolerance in the second radiation peak for valid tests; c) modification of the refuelling procedure for long briquettes; d) provision of a suitable aerato
16、r to enable the gas ignition burner to burn natural gas; e) inclusion of the form of test report required; f) specification of a sampling method in a dilution tunnel as an alternative means of smoke measurement to the electrostatic precipitator (see Annex A); g) change of organic solvent for cleanin
17、g the precipitator; h) change of procedure for conditioning the precipitator, utilizing a constant temperature room (hot room); i) inclusion of safety precautions relating to the use of high voltage and of organic solvent in the operation of the precipitator. A British Standard does not purport to i
18、nclude all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pa
19、ges i and ii, pages1 to 20, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS3841-2:1994 BSI 09-1999 1 0 Introduction BS3841-1describes the ge
20、neral procedure to be adopted for measuring the smoke emissions from solid smokeless fuels. This Part of BS3841 describes procedures for measuring the smoke emission rate (in g/h) under the combustion conditions specified in Part 1. The electrostatic precipitator method was developed for the purpose
21、 of collecting and measuring the smoke from domestic appliances burning solid fuel. The precipitator collects the particulate matter from the total volume of flue gas produced by the fire during the test period. The total mass of smoke emitted during the test period is determined by weighing the pre
22、cipitator at the beginning and end of the test. The dilution tunnel method involves sampling isokinetically from a duct above the test chimney. This technique is widely used internationally. Both methods have been shown to be capable of measuring in the range0.5g/h to30g/h. The two methods give resu
23、lts in close agreement (seeAnnex A). 1 Scope This Part of BS3841 describes an electrostatic precipitator method and a dilution tunnel method for measuring the smoke emission rate from a manufactured solid fuel tested in accordance with BS3841-1:1994. 2 References 2.1 Normative references This Part o
24、f BS3841 incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent ame
25、ndments to or revisions of the cited publication apply to this Part of BS3841 only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments. 2.2 Informative references This Part of BS3841 re
26、fers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Electrostatic precipitator method for smoke emission rate measurem
27、ent 3.1 Principle The instrument used is an electrostatic precipitator developed for the purpose of collecting and measuring the smoke from domestic appliances burning solid fuel. It is placed on top of the laboratory test chimney and removes the smoke from the whole of the flue gas with minimal res
28、istance to flow. The total mass of smoke emitted during a test period is determined by weighing the instrument at the beginning and the end of the test. NOTEThe precipitator has been shown to have the requisite efficiency of smoke collection for testing manufactured solid fuels in accordance with BS
29、3841-1and was used in the experimental work leading to the formulation of BS3841. 3.2 Apparatus 3.2.1 Electrostatic precipitator, comprising a single stage multi-tube unit, constructed as shown in Figure 1 to Figure 4. The main components of the assembly shall be as follows. a) Collecting electrodes
30、. The collecting electrodes(1) (seeFigure 1) shall be made of hexagonal tube of0.7mm thick aluminium alloy, having external dimensions of30mm across the flats, assembled in a honeycomb consisting of85passages, as shown in the plan view. By utilizing the outside of some of the tubes as collecting sur
31、faces, the assembly shall be made up of66individual tubes,457mm long. The ends of the tubes shall be argon-arc welded together and the tube assembly shall be welded to a356mm diameter base plate and330mm diameter top plate. Both end plates shall be flanged and shall be of1.6mm thick aluminium alloy.
32、 A102mm high aluminium alloy skirt (2) of diameter360mm shall be bolted to the flange on the base plate. The skirt shall contain two 6 mm swages approximately51mm apart, the lower one being29mm from the base of the skirt. b) Charged electrodes. The charged electrodes(10) (seeFigure 1) shall be made
33、of hard-drawn stainless steel wire of0.15mm diameter, and shall pass along the vertical axis of each tube. They shall be spring loaded and shall be attached to suspension hooks (8) on a supporting framework at each end of the tube assembly.BS3841-2:1994 2 BSI 09-1999 c) Supporting frames. The suppor
34、ting frames (4) and (5) shall be as shown in Figure 1 and Figure 2. Each frame shall be made up of22aluminium alloy strips of width13mm and thickness1.6mm. The strips shall be slotted together into a lattice (seeFigure 2) resulting in85junctions at which the suspension hooks (8) clip on. The frames
35、shall be strengthened by12mm 12mm aluminium angle of thickness3mm formed into a ring, butt welded and then welded round the periphery of the lattice. The top frame shall be attached to the main frame by13mm 13mm insulators, for example of compressed mica-filled phenolformaldehyde (3). For the lower
36、supporting frame, the insulators shall be held at an angle of45 to the vertical by mounting brackets made from1.6mm thick aluminium (6) and (7), the insulators passing through32mm diameter holes in the skirt. NOTEDetails of the method of fixing are shown in Figure 3. The precipitator shall be positi
37、oned for smoke collection as shown in Figure 4. A610mm 610mm mild steel sealing plate shall be attached to the top of the square section test chimney to form the base of a safety cage. In the centre of this plate a hole shall be cut,330mm in diameter. A locating ring of internal diameter370mm shall
38、be made up from25mm 3mm mild steel strip, located centrally on the base plate and fastened by a suitable means such as tack welding. When in position for smoke collection, the precipitator shall stand inside the locating ring. A collecting hood shall be positioned above the precipitator and connecte
39、d by ducting to a fan discharging to outside air. A damper shall be provided in the extraction ducting to enable the suction exerted by the fan to be varied. 3.2.2 Extra-high tension (EHT) power unit, capable of providing a continuously variable output voltage of0kV to12kV at50mA continuous rating.
40、The output shall be d.c. negative to earth, with a ripple content of not more than1%. Meters shall be provided for reading the output voltage and the current on a meter scale of approximately125mm. The meters shall be at the final stage of the output of the circuit in order that internal tracking cu
41、rrent, which increases with the usage of the equipment, is not measured. An overload protection device shall be incorporated to safeguard the components of the unit against short-circuiting at the output terminals. This device shall be so designed as to switch off the mains power supply to the unit
42、and to provide an audible warning signal; an interlock shall be provided to ensure that the overload protection device cannot be reset until the voltage control has been returned to zero. The leads from the power unit shall be connected to the electrostatic precipitator by means of suitably sized cr
43、ocodile clips, the negative conductor being attached to the top supporting frame see3.2.1 c) and the positive conductor, which is at earth potential, to the top plate see3.2.1 a). WARNING. It is essential that adequate precautions be taken to prevent personnel who are operating the equipment from co
44、ming into contact with the high voltage. Suitable equipment consists of an earthed metal cage with a gate, surrounding the precipitator when in position for smoke collection. With this method a safety lock should be attached to the gate in the cage, with an interlocking arrangement to the EHT unit w
45、hich ensures that the unit can be turned on only when the gate is closed. A reliable independent earth should be provided for the collecting hood in the flue gas extraction system (see3.2.1) and for the safety cage described above. The EHT unit itself should be built into a totally enclosed cabinet
46、which is also earthed. 3.2.3 Means for discharging the precipitator NOTEThis should preferably be an automatic shorting device, e.g. linked to the mechanism for opening the gate on the safety cage. Alternatively the precipitator may be discharged manually, a suitable design of earthing tool being sh
47、own in Figure 5. 3.2.4 Electrically heated, thermostatically controlled oven, for drying the precipitator and evaporating any residual solvent after cleaning (see3.3.1). The oven shall be fitted with a control dial that indicates the set oven temperature within a range of at least20 C to120 C, with
48、an accuracy of 2K. NOTE 1Essential safety precautions for the design and use of the oven are given in 3.4.1. NOTE 2The most suitable size of oven depends on the number of test chimneys and the frequency of testing. It is recommended that the oven should be able to hold two precipitators per test chi
49、mney. 3.2.5 Temperature-controlled room (hot room), for conditioning the electrostatic precipitator before use (see3.3.2). The room shall be heated by tubular electric convector heaters and shall be thermostatically controlled at an average temperature between32 C and35 C with a fluctuation of less than 3K about the mean temperature. The room shall have enough floor space for the balance specified in 3.2.6 and sufficient storage space for all the precipitators in regular use in the test laboratory. 3.2.6 Balance, for weighing the preci
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