Feasibility Study of Retrofitting Low Cost Traps to in-use ......feasibility study includes a trial program of testing 62 in-use diesel taxis, diesel light buses and diesel light goods

THE HONG KONGPOLYTECHNIC UNIVERSITY

Feasibility Study of Retrofitting Low Cost Traps to in-use Light DutyDiesel Vehicles Below 4-tonnes Gross Vehicle Weight

Final Report

July 2000

Table of Contents

Executive Summary

1. Introduction

2. Execution of the Feasibility Study

3. Trap Installation

4. Effect of Trap on Smoke Reduction

5. Effect of Trap on Particulate Reduction

6. Effect of Trap on Back Pressure

7. Lug-down Tests

8. Spontaneous Soot Regeneration (SSR)

9. Cleaning of Trap

10. Cost Implication

11. Drivers’ Opinion Survey Results

12 Conclusion

Figures and Tables

Tables 2.1 – 2.3Figures 3.1 – 3.6Figure 4.1Tables 4.1 – 4.7Figures 5.1 – 5.6Figures 8.1 – 8.2Figures 9.1 – 9.4Table 9.1Figure 9.5

Appendices

I Membership list and terms of reference of the Monitoring CommitteeII Wastewater analysisIII Survey Form and Survey Results

Executive Summary

A feasibility study of retrofitting low cost traps to in-use diesel vehicle below 4 tonnes grossvehicle weight (hereafter the Study) was commissioned in July 1999 by the EPD/HKSARGundertaken by The Hong Kong Polytechnic University (The PolyU).

The main objectives of the Study are to find out the effectiveness of the particulate trap onsmoke and particulate reduction as well as the acceptability of the trap to the concernedvehicle operators. At the same time, the adverse impacts of the trap on fuel consumption andback pressure of vehicles as well as other issues like spontaneous soot regeneration (SSR)and cleaning of the trap have to be investigated.

Sixty-two vehicles comprising 21 taxis, 22 light goods vehicles (LGVs) and 19 public lightbuses (PLBs) were recruited in the Study, which was commenced on 19 August andcompleted on 24 December 1999. The Study was extended for a cleaning trial at fuel fillingstations from March to May 2000.

A monitoring committee comprising members of the trade associations, vehicle owners,vehicle drivers, academics, Motor Traders Association (MTA), Environmental ProtectionDepartment (EPD) and Transport Department was formed to monitor the progress of theStudy and provide inputs to the Study. Four meetings were held up to the end of January2000. The monitoring committee contributed valuable opinion and help to the smoothprogressing of the Study.

The PolyU retrofitted the trap, measured the smoke level and weighed the trap regularly foreach participated vehicle. Special tests such as lug-down tests and back pressure tests onselected vehicles were performed. A questionnaire survey on drivers' opinion on the trap wasalso conducted.

The Study generated the following results, which have been endorsed by the MonitoringCommittee in a meeting held on 15 April 2000.

1. The average smoke level was reduced by 30% for the taxis, 35% for the LGVsand 21% for the PLBs.

2. Tests performed at the National Engine Combustion Laboratory of the TianjinUniversity found that there was a 30% reduction in smoke opacity at themaximum torque condition and a 30% reduction in particulate over the ECE-R49 13-mode test cycle.

3. The trap collected on average 12 grams of particulate per week for the LGVs.The trap collected about 23 grams per day for the PLBs and 6 grams per day forthe taxis.

4. The back pressure generated by the trap filled with particulate was 1.6 to 4.7kPa for the 3 selected taxis; 1.1 to 3 kPa for a selected LGV and 3.8 to 6 kPa forthe 2 selected PLBs. The MTA did not deem the back pressure to be an issue.

5. The power reduction caused by the trap was less than 3% for the 5 vehicles (3taxis, 1 LGV and 1 PLB) tested.

6. About one-third of the particulate in the filled traps could be released during thelug-down tests. If the trap is cleaned daily, the particulate released will begreatly reduced.

7. Spontaneous soot regeneration (SSR) could happen for poorly maintainedvehicles. With long period of high engine power operation, and a highparticulate quantity stored in the trap, SSR could occur.

8. For the taxis and LGVs, daily cleaning of the trap and reasonable maintenanceof the vehicle could avoid SSR. The design of the traps has been improved toprevent SSR from happening.

9. Cleaning with a cleaning machine or rinsing in a box containing water withdetergent, were effective to clean up the particulate in the trap. Both methodswere tried at selected fuel filling stations. The vehicle operators considered bothmethods acceptable. The quality of wastewater generated by both methodscould meet relevant discharge standards of the EPD.

10. The running and cleaning costs of the trap for the vehicle operators are minimal,being less than one dollar per cleaning, and should be affordable.

11. The drivers and operators of the vehicles agreed that the trap was effective inreducing black smoke emissions, there were little adverse impacts on fuel andlubrication oil consumption and 82% of the 28 questionnaire respondentssupported the suggestion that all small diesel vehicles should be fitted with thetrap.

It can be concluded that the particulate trap is effective in reducing smoke level andparticulate emitted from light duty diesel vehicles; the adverse impacts on the vehicles areminimal and acceptable to the trade. The trap is generally welcome by the vehicle drivers andoperators.

1. Introduction

Background of the project

1.1 The Hong Kong Polytechnic University (The PolyU) has been developing a lowcost particulate trap suitable for use on light duty diesel vehicles since 1996. Theproject was initially funded, HK$190,000, by the Taxi Dealers and OwnersAssociation Limited. Subsequently the PolyU funded another HK$1.3 million toimprove the design of the trap. The trap has been shown in the laboratory toremove about 20% particulate from the diesel vehicle exhaust and reduce smokelevel by 10% - 50%. The trap has been tested on two taxis and four public lightbuses for several months since November 1998. There was no adverse effectreported from the users.

1.2 The Environmental Protection Department (EPD) has been the adviser for thedevelopment program of this low cost particulate trap and saw the potentialapplication of the trap on the light duty diesel vehicles to reduce particulateemissions, which have been a main cause of air pollution in Hong Kong.

1.3 EDP commissioned a feasibility study of retrofitting low cost traps to in-use dieselvehicle below 4 tonnes gross vehicle weight to the PolyU in July 1999. Thefeasibility study includes a trial program of testing 62 in-use diesel taxis, diesellight buses and diesel light goods vehicles below 4 tonnes gross vehicle weight.

1.4 The feasibility study took five months to complete at the end of December 1999.The study was further extended for a cleaning trial at fuel filling stations fromMarch to May 2000. This Report gives the detailed results of the feasibility study.

Objectives of the Study

1.5 The objectives of the feasibility study are:

1.5.1 To determine the effectiveness of the trap in lowering smoke;1.5.2 To find out the impacts of the trap on the fuel consumption and powerof the vehicles;1.5.3 To ensure that the particulate stored in the trap is not released duringhigh load engine operation;1.5.4 To find out the total costs including operational cost for maintainingthe trap; and1.5.5 To find out the response of the operators of the test vehicles to theoperation, maintenance and acceptability of the trap.

2. Execution of the Feasibility Study

In conducting the feasibility study, the PolyU recruited and organized the test vehicles;retrofitted the traps and conducted mechanical and emission tests on the vehicles as wellas produced regular progress reports for the scrutiny of the EPD/HKSARG and themonitoring committee specifically formed for this Study.

Organization of the trial fleet

2.1 A letter dated 23 July 1999 was sent and faxed to about 70 organizationsinforming them about the project and inviting for participation. Twelveorganizations replied and indicated interest in participation in the project.

2.2 A briefing session was held on 12 August 1999 to introduce the trial programto the representatives from the potential participation organizations.

2.3 Altogether, 21 taxis, 22 light goods vehicles (LGVs) and 19 public light buses(PLBs) participated in the trial program. The particulars of the vehicles areshown in Tables 2.1, 2.2 and 2.3. Of the 21 taxis, 19 are pre-Euro vehicles and2 are Euro I vehicles. Of the 22 LGVs, 11 are pre-Euro vehicles, 2 are Euro Ivehicles and 9 are Euro-II vehicles. All PLBs are pre-Euro vehicles.

Operation of the trial

2.4 The trial period spanned from 19 August 1999, when the first vehicle wasretrofitted, to 24 December 1999, when the last trap was officially dismantled.The trial program lasted for more than four months.

2.5 PolyU carried out all retrofits. The taxis and the LGVs were retrofitted at theworkshop U004 in the PolyU campus while the PLBs were retrofitted on site.

2.6 During the trial period, each trap was weighed and cleaned regularly tomonitor the effectiveness of the trap in collecting particulate.

2.7 For the taxis and the LGVs, during the first week, each vehicle was requiredto return on a daily basis to the PolyU for weighing the quantity of particulatecollected. Starting from the second week, the vehicles were required to returntwice per week for three weeks. Commencing from the fifth week, thevehicles were required to return on a weekly basis. In the last week, thevehicles were asked to return three times in that week. In general, the trapswere cleaned on a weekly basis.

2.8 The PLBs, due to their mode of operation, did not return to the PolyU. Hence,they were visited daily on site. The traps were replaced as necessary ratherthan on a weekly basis. It was soon realized that, due to the large amount ofparticulate collected, the traps had to be cleaned daily.

The monitoring committee

2.9 In order to solicit the opinion of concerned parties on the feasibility ofretrofitting the trap to light duty diesel vehicles, a monitoring committee wasformed to monitor the progress of the trial program. The committee iscomprised of representatives of trade associations, vehicle owners, vehicledrivers, academics, Motor Traders Association, EPD and TransportDepartment.

2.10 The first monitoring committee meeting was held on 4 September 1999,during which the Committee was officially established. The membership listand the terms of reference of the Committee are shown in Appendix I. Thesecond, third and fourth meetings were held on 2 October 1999, 13 November1999 and 8 January 2000 respectively to receive the progress reportssubmitted by the PolyU and to discuss matters concerned. The final meetingwas held on 15 April 2000 to receive the final report.

3. Trap Installation

3.1 The particulate trap designed by the PolyU is essentially an axial flow fibrousfilter using rectangular stainless steel fibers as the filtering element. The basicconstruction is shown in Figure 3.1. It is comprised of a filter cartridge enclosedwith an outer casing. The average packing density of the stainless steel fiber is 1%,and the effective length of the filter cartridge is 150 mm. The diameter of the filtercartridge is 125 mm for taxis and LGVs, and 150 mm for PLBs, to match with thedifference in their engine capacities and hence exhaust gas volume flow rates.

3.2 The traps were fixed to the vehicles by a variety of methods to cater for the spacelimitations and the different exhaust pipe configurations.

3.3 For the taxis and LGVs, three types of trap connections were tried. The firstmethod is shown in Figure 3.2. The trap was hung underneath the chassis andconnected to the exhaust pipe by a stainless steel connector. In the second method,as shown in Figure 3.3, the rigid connector was replaced by a flexible fiberglasssleeve. In both cases, the exhaust pipe was cut by a few inches to allow for thelength of the filter. The third method is shown in Figure 3.4. The trap was securedat the end of the vehicle and connected to the exhaust pipe using a flexiblefiberglass sleeve. In this case, there was no need to cut the exhaust pipe. The firstmethod was used for most of the taxis; the second method was used for most ofthe LGVs. The third method was tried on a few taxis and was not welcomed bythe drivers.

3.4 For the PLBs, due to the availability of space for installation, the trap wasconnected directly to the exhaust pipe using the rigid connector, as shown inFigure 3.5. The older PLBs have their exhaust pipe located at the aft part of thebody while for the newer PLBs, the exhaust pipe is located between the wheels onthe right hand side. In this trial, only the older ones were retrofitted. There wasdifficulty in retrofitting the newer ones due to the location of the exhaust pipe.

3.5 Throughout the trial, the trap coupled with a rigid connector was found to be themost reliable combination. However, there could be difficulty in using thismethod of connection, for example, for some LGVs. The flexible connectors usedfor the LGVs proved to be flexible but less reliable. The prototype flexible sleevecould be damaged in a few weeks due to the rubbing action between the trapand/or the exhaust pipe with the fiber-glass sleeve.

3.6 Figure 3.6 shows an oval-shaped particulate trap, which was used on a fewvehicles in the trial from March to May 2000. The oval-shaped trap provides moreclearance space between the trap and the road and a larger surface area for heattransfer than the circular trap.

4. Effect of Trap on Smoke Reduction

4.1 After retrofitting the particulate trap, a custom made connector has to be used formeasuring the smoke opacity of the vehicle, as shown in Figure 4.1

4.2 Free acceleration smoke test was carried out for each vehicle before theinstallation of the trap as baseline information. Immediately after retrofitting thetrap, each vehicle was again tested for the smoke emission under free acceleration.The results for each category of vehicle are shown in Tables 4.1, 4.2 and 4.3.

4.3 For the taxis, the smoke reduction varied from 8.6% to 60.2% with an averagevalue of 29.7%. For the LGVs, the smoke reduction varied from 11.9% to 57.5%with an average value of 35.3%. For the PLBs, the smoke reduction varied from4.1% to 43.9% with an average of 21.1%

4.4 At the end of the trial, after dismantling the trap from a vehicle and repairing theexhaust pipe as necessary, the smoke emission under free acceleration was testedagain for each taxi and LGV. The results are shown in Table 4.4 for the taxis andTable 4.5 for the LGVs. In general, there is no evidence of increase in smokeemissions after a prolonged period of using the particulate trap.

4.5 For the taxis and LGVs, five vehicles were selected for similar tests at an intervalof one month. The results are shown in Tables 4.6 and 4.7.

4.6 Based on the results obtained, it can be concluded that the particulate trap iseffective in reducing smoke during the free acceleration smoke tests. The bigvariation in the percentage of smoke reduction can be attributed to (a) variation inquality of the trap and (b) variation of the engine acceleration during the tests.

4.7 An independent test conducted by the National Engine Combustion Laboratory ofthe Tianjin University on the particulate trap indicates that it could reduce thesmoke at rated conditions from 2.5 Bosch smoke unit to 1.6 Bosch smoke unit,which corresponds to a 36% reduction in smoke opacity. At the maximum torquecondition, the smoke was reduced from 2.3 Bosch smoke unit to 1.6 Bosch smokeunit, which corresponds to a 30% reduction in smoke opacity.

5. Effect of Trap on Particulate Reduction

5.1 The taxis and the LGVs returned daily to the PolyU for measuring the increase inthe weight of the trap during the first week. The daily amount of particulatecollected in the first week could be assessed. Figures 5.1, 5.2, 5.3 and 5.4 showthe amount of particulate collected as a function of day and mileage.

5.2 The amount of particulate collected varied from vehicle to vehicle, and from dayto day for the same vehicle. On the whole, the particulate collected per daydecreased exponentially. The amount of particulate collected during the first twodays was about the same as that collected during the last five days. The trends forthe LGVs were the same.

5.3 The trend lines for the particulate collected by the taxis indicate that 20 grams ofparticulate were collected during the first week, while the trap was saturated after2,000 km.

5.4 The trend lines for the particulate collected by the LGVs indicate that the trapcould collect 12 grams of particulate during the first week and was saturated after1,300 km.

5.5 Some taxis were requested to return to the PolyU more frequently to allowassessment of the effectiveness of the trap in collecting particulate as a function oftime. The particulate collected in one day, two days, three days, four days and fivedays were compared. The result is shown below:

One day: 5.4 gram/dayTwo days: 5.9 gram/dayThree days: 4.3 gram/dayFour days: 4.1 gram/dayFive days: 3.1 gram/day

Obviously, the trap is more effective in collecting particulate during the first twodays of operation, after each cleaning.

5.6 Figure 5.5 shows the collection of particulate for the different weeks during thetrial period for the taxis. Basically, there is no significant difference in the amountof particulate collected each week throughout the trial period. The same isobserved for the LGVs.

5.7 Due to their mode of operation, the PLBs did not return to the PolyU. They werevisited daily on site. The traps were replaced on a daily basis due to the largeramount of particulate collected per day. The PLBs retrofitted include 14 greenPLBs and five red PLBs. Each green PLB collected about 23 gram/day with amileage of over 300 km/day. Each red PLB collected about 11.5 gram/day, whichis equivalent to about 28 gram/day when the mileage is converted to 300 km/day.

5.8 Figure 5.6 compares the amount of particulate collected by the traps installed oneach category of vehicle, as a function of the mileage. It is obvious that the trapson PLBs collected much more than those of the taxis and LGVs for the same

mileage covered. This can be explained in part by the larger engine capacity andin part by the difference of the mode of operation of the vehicles. The PLBs runon fixed routes, which involve a number of stops from one terminal to another.Moreover, the PLBs, especially the green ones, are in continuous operation duringtheir business hours with only short breaks or idling operations. The taxis, despitehaving longer operating hours than the PLBs, except due to traffic jams or trafficcontrol, have basically no stop when traveling from one destination to another.They are generally in cruising or idling operations when there is no business. Forthe LGVs, the vehicles are basically not in operation except when running fromone destination to another for business.

5.9 Another reason for the difference in the particulate collected from each categoryof vehicle is due to the age and state of technology of the vehicles concerned. AllPLBs participating in the trial program are pre-Euro vehicles of which 9 aremanufactured before year 1990, while 9 of the 22 LGVs are Euro-II vehicles.

5.10 The independent test conducted by the National Engine Combustion Laboratory ofthe Tianjin University on the particulate trap indicates that it could reduceparticulate emission, under the ECE-R49 13 mode test cycle, by 30%.

6 Effect of Trap on Back Pressure

6.1 The increase in back pressure of the exhaust gas due to the fitting of theparticulate trap is a concern to all parties. The back pressure for a taxi, a LGV anda PLB were measured on-road while the back pressure for three taxis, a LGV anda PLB were measured during the lug-down tests. The on-road back pressure testswere conducted on roads with slopes.

Taxis

6.2 A taxi carrying a trap containing 18 grams of particulate was arranged for a backpressure test on 2 September 1999. The back pressure was measured at the inlet ofthe particulate trap. The taxi was driven from the PolyU to Clearwater Bay and toKowloon Bay. The maximum back pressure was about 4 kPa while the maximumexhaust gas temperature was about 270oC.

6.3 The same taxi was then put on the chassis dynamometer and lug-down tests wereconducted first with the trap and then without the trap. The maximum backpressure, with the trap, was about 4.7 kPa.

6.4 Two taxis were arranged for test on the chassis dynamometer on 18 December1999. The first taxi was carrying a trap with 8 grams of particulate. The maximumback pressure was 2.7 kPa. Another taxi was carrying a trap with 11 grams ofparticulate. The maximum back pressure was 1.6 kPa.

LGV

6.5 A LGV carrying a trap containing 14 grams of particulate was arranged for a backpressure test on 24 September 1999. The LGV was driven from Wong Chuk Hang,via Aberdeen, to Pokfulam. The test was repeated again without the particulatetrap. In both cases, the back pressure was measured at the engine exhaust outlet.The maximum back pressure was about 11.5 kPa with the trap and about 8.5 kPawithout the trap.

6.6 The same LGV ran up the Aberdeen Reservoir Road for a series of tests on 9October 1999, with a trap containing 11 grams of particulate and without the trap.The back pressure was measured at the engine exhaust outlet. The maximum backpressure was about 16 kPa.

6.7 The same LGV was arranged for a back pressure test on 12 October 1999 from theCotton Tree Drive to Peak Road. The test was carried out first without a trap andthen with a trap containing 12 grams of particulate. The back pressure wasmeasured at the engine exhaust outlet. The difference in back pressure was 2 kPa.

6.8 The same LGV was arranged for a test on the chassis dynamometer on 18December 1999. A lug-down test was carried out first with a trap containing 10grams of particulate and then repeated with a clean trap. In these cases, the back

pressure was measured at the inlet to the particulate trap. The maximum backpressure was about 1.1 kPa for the dirty trap and 0.8 kPa for the clean trap.

PLB

6.9 A PLB with a trap containing 46 grams of particulate was arranged for a backpressure test on 7 September 1999 from Aberdeen to Pokfulam Road. Themaximum back pressure, which was measured at the inlet of the trap, was slightlyhigher than 6 kPa.

6.10 The back pressure of another PLB was measured during the lug-down testsconducted on 18 December 1999. The maximum back pressure was about 3.8 kPa.The trap contained about 20 grams of particulate.

Comments

6.11 Based on the measured back pressure results, the following conclusions can bemade. Firstly, there is an increase in back pressure due to the installation of theparticulate trap and the particulate collected in the trap. Results measured on threetaxis, one LGV and two PLBs indicate that the maximum increase was a few kPa.Secondly, based on the results measured on the LGV, the maximum back pressurewas still very small and should be well within the manufacturer’s allowable limit.

6.12 The Motor Traders Association was consulted and did not deem the back pressureto be an issue. MTA did not have specific comments that the trap would affect thevehicle performance negatively.

6.13 The users of traps should be properly instructed to clean the trap regularly to avoidthe building up of the particulate, and hence back pressure, in the trap.

7. Lug-down Tests

7.1 Lug-down tests were carried out on a number of vehicles both with and withoutthe particulate trap for assessing (a) the loss of power due to the trap, and (b) theamount of particulate blown out from a trap during the lug-down test. The keyresults are shown below.

Taxis

7.2 Three taxis were arranged for the lug-down tests. Taxi A carrying a trap wasarranged for a lug-down test on 2 September 1999. The smoke opacity was notmeasured. The trap contained 18 grams of particulate before the test. The amountof particulate remained in the trap was 13 grams at the end of the test. Hence therewas a reduction of 5 grams of particulate during the test. The maximum enginepowers of the lug-down tests with and without the trap are shown in Table 7.1

Table 7.1: Summary of Lug-down Test Results of Taxi A

Smoke (HSU)Maximum power

kW

Enginespeed at

maximumpowerRPM

100%speed

90%speed

80%speed

Without trap 33.83 3389 - - -With trap 33.02 3449 - - -

7.3 Taxis B and C were arranged for lug-down tests on 18 December 1999. Taxi Bwas carrying a trap containing 8 grams of particulate. There was a reduction of 2grams after the test. Taxi C was carrying a trap containing 11 grams of particulate.There was a reduction of 4 grams after the test. The maximum engine powers andthe smoke opacities for these two taxis are shown in Tables 7.2 and 7.3.

Table 7.2: Summary of Lug-down Test Results of Taxi B

Smoke (HSU)Maximum

powerkW

Enginespeed at

maximumpowerRPM

100%speed

90%speed

80%speed

Without trap 25.03 3605 33.2 25.9 31.8With trap 24.59 3576 40.4 50.9 55.28

Table 7.3: Summary of Lug-down Test Results of Taxi C

Smoke (HSU)Maximum

powerkW

Enginespeed at

maximumpowerRPM

100%speed

90%speed

80%speed


LGV

7.4 A LGV was arranged for two lug-down tests, one on 29 October 1999 and theother on 18 December 1999. The maximum engine powers and the smokeopacities are shown in Tables 7.4 and 7.5. In the first test, the soot burnedspontaneously upon completion of the test and hence the amount of particulateafter the test could not be measured. In the second test, the trap contained 10grams of particulate before the test and 6 grams after the test. In this latter case,the vehicle was also tested with a clean trap attached. Due to the already very lowsmoke intensity of the vehicle and the limitation of the resolution of theequipment, the latter did not give meaningful result.

Table 7.4: Summary of Lug-down Test of LGV (29/10/99)

Smoke (HSU)MaximumpowerkW

Engine speedat maximum

powerRPM

100%speed

90%speed

80%speed


Table 7.5: Summary of Lug-down Test of LGV (18/12/99)

Smoke (HSU)MaximumpowerkW

Engine speedat maximum

powerRPM

100%speed

90%speed

80%speed

Without trap 31.77 2782 6.64 7.62 7.96Dirty trap 31.46 2817 15.9 14.1 11.9Clean trap 30.58 2777 7.3 6.1 6.8

PLB

7.5 A PLB was arranged for a lug-down test on 18 December 1999. The trapcontained 18 grams of particulate before the test and 12 grams after the test. Themaximum engine powers and smoke opacities are shown in Table 7.6.

Table 7.6: Summary of Lug-down Test Results of PLB

Smoke (HSU)Maximum

powerkW

Enginespeed at

maximumpowerRPM

100%speed

90%speed

80%speed


Comments

7.6 The results indicate that there is in general a marginal reduction in engine powerdue to the trap and the particulate trapped. Moreover, during the lug-down tests,part of the trapped particulate, about one-third, will be blown out from the trap.These lug-down tests were carried out mainly with heavily loaded traps. If aparticulate trap is cleaned as frequent as daily, it would be less heavily loaded andthe blown out would be much less.

8. Spontaneous Soot Regeneration (SSR)

8.1 Spontaneous soot regeneration (SSR) was found to occur in a number of occasions.In all cases, the particulate and some of the stainless steel fibers were burned,while the casings remained intact. Typical burned filter cartridges are shown inFigures 8.1 and 8.2.

Taxis

8.2 When the taxis were programmed to return to the PolyU for cleaning on a weeklybasis, three taxis were identified to have recurrent SSR problem. It occurred twiceon one taxi and five times on two other taxis. By shortening the cleaning period tothree days, the burning problem was under control. SSR was also found once onthree other taxis.

LGV

8.3 Two SSR cases occurred on one LGV. The LGV was found to emit a significantquantity of white smoke due to a fuel pump problem. It caused unburned fuel todeposit on the fibers of the trap. After repairing the fuel pump, SSR did nothappen to the LGV again.

PLB

8.4 When the trap was first used on the PLBs, they were of the four-layer type with atotal thickness of 200 mm of fiber. This is different from those used on taxis andLGVs, in which the trap contains three layers of fibers with a total fiber thicknessof 150 mm. After using traps of the three-layer design, and since all traps of PLBswere replaced on a daily basis, severe SSR did not occur. However, due to thelarge amount of particulate collected in one day and the high exhaust gastemperature induced by poor engine conditions of some PLBs, minor SSR couldoccur even the trap was cleaned on a daily basis. This happened once on fivePLBs.

Analysis and solution

8.5 For the taxis, SSR occurred on vehicles, which had accumulated particulate for afew days, when they were operating at high engine loads, usually running up aslope or running at high speed.

8.6 The trap collects particulate that can burn under certain conditions. SSR isassociated with (a) the accumulation of a significant amount of particulate in thetrap and (b) an abnormally high exhaust gas temperature which ignites theparticulate in the trap.

8.7 The exhaust gas temperature of some vehicles can be higher than that of othersdue to poor engine or cooling conditions. The exhaust gas temperature before thetrap was measured for four taxis while they were driven on the Shing Mun Tunnel

Road at 80 km/hr, carrying four passengers each. Taxis A and B have recurrenttrap burning record while taxis C and D have not experienced any trap burningproblem. The maximum temperature was 380oC for taxi A and 390oC for taxi B.The maximum temperature was 300oC for taxi C and 333oC for taxi D. The formervehicles had exhaust gas 20% hotter. The higher exhaust gas temperature wasconsidered the main reason for the recurrent SSR problem.

8.8 Some taxis, which had no SSR problem throughout the trial period, collected asignificant amount of particulate on a weekly basis. This is strong evidence thatthe accumulation of particulate itself would not lead to SSR. The deposition of asignificant amount of combustible material such as the fuel and the lubricant dueto poor engine condition could be a major cause. By increasing the frequency oftrap cleaning, the accumulation of combustible material in the trap can be reducedand hence controlled to a safe level. For the three taxis identified to have recurrentSSR problem, two of them were enrolled into a daily cleaning programme. NoSSR was observed during the daily cleaning period. A well maintained enginecoupled with a good cleaning program would prevent SSR from happening.

8.9 It can be concluded that if properly maintained, a LGV is free from SSR problemwhile a taxi is free from SSR problem if in addition the trap is cleaned at leasttwice per week.

8.10 For the PLBs, minor SSR could happen even when the trap was cleaned on a dailybasis. This is attributed to the larger amount of particulate trapped per day, thehigher exhaust gas temperature of the vehicles concerned, and the smaller surfacearea to volume ratio of the larger traps for the PLBs. The smaller surface area tovolume ratio causes a poorer heat loss from the trap to the surrounding and hencea larger chance of SSR.

Improvement of Particulate Trap

8.11 Three design features have been identified for improvement for the particulatetrap. Firstly, a perforated plate is inserted at the inlet end of the filter cartridge todisperse the exhaust gas more evenly in the filter. This helps to avoid localoverheating in the trap. Secondly, the trap is changed into an oval shapeconstruction to increase the surface area to volume ratio and hence helps toenhance heat transfer from the trap to the surrounding. These two design featureshelp to prevent SSR from happening. Thirdly, in case SSR does occur, a firescreen can be inserted at the exhaust end of the particulate trap to prevent sparkfrom being dispersed into the surrounding area. This design will be applied to thePLBs. Coupled with an improvement of trap design, and if cleaned daily andproperly maintained, PLBs can be free from SSR problem.

8.12 Vehicle operators need to be reminded that proper engine maintenance and propercleaning of the trap is required to avoid SSR.

9. Cleaning of Trap

The Cleaning Methods

9.1 During the particulate trap trial program, four cleaning methods had been tried. Inall methods, the filter cartridge has to be withdrawn from the filter casing forcleaning.

9.2 In the first method (Figure 9.1), the filter cartridge was first placed in a boxcontaining water with detergent. The box was then placed into the boot or anyconvenient location of the vehicle. To avoid spillage of the liquid, a second boxcan be used to house the first box. When the vehicle was driven, the movement ofthe water would help rinse and clean the filter cartridge. After rinsing on thevehicle, the filter cartridge was then removed from the box and rinsed in cleanwater for further use.

9.3 In the second method (Figure 9.2), the filter cartridge was first rinsed in a bucketof water containing detergent. It was then rinsed in clean water for further use.

9.4 In the third method (Figure 9.3), the filter cartridge was held by a robot arm andthen shaken in a bucket of water containing detergent. It was then rinsed in cleanwater for further use.

9.5 In the fourth method (Figure 9.4), the filter cartridge was placed into the cleaningchamber of a cleaning machine. A pump was used to circulate water to flush thefilter cartridge. After flushing, the filter cartridge was ready for further use.

9.6 The overall cleaning period, including dismantling and reinstallation of the trap,was about 3 – 5 minutes.

Cleaning Frequency

9.7 The original idea was to clean the traps once a week. It was soon reflected by thedrivers that the trap needed to be cleaned twice a week in order to reduce theincrease in back pressure and avoid reduction in trap effectiveness in collectingparticulate.

9.8 Towards the end of the trial period, it was decided to enroll a number of vehiclesfor conducting cleaning on a daily basis.

Effectiveness of Cleaning Methods

9.9 Six taxis were enrolled for the daily cleaning exercise. Three cleaning methodswere tested: manual cleaning, machine flushing and machine shaking. Table 9.1shows the change of weights of the traps after a period of 14 to 25 days. Thegeneral difference is around 2 grams, which indicates that all the cleaningmethods are effective in removing the particulate in the trap.

9.10 Figure 9.5 shows the amount of particulate collected by the trap before eachcleaning. In general, more than six grams of particulate could be collected per day.There is no steady increase in the weight of collected particulate, indicating thatthere is no accumulation of residue in the trap.

9.11 In the manual cleaning method, the trap was rinsed in water containing 2%detergent and then rinsed in clean water before re-installation. This cleaningprocess can be conducted essentially anywhere conveniently.

9.12 In the machine flushing method, the trap was flushed with water alone and theflushing water could be recirculated for cleaning about 25 traps beforereplacement. This cleaning process can be conducted only at centralized locations,which have space to house the flushing machine.

9.13 In the machine shaking method, the trap was shaken violently in water containing1% detergent and then rinsed in water before re-installation. This machine canoperate electrically or pneumatically. Again, this cleaning process can beconducted only at centralized locations equipped with the shaking machine.

Comments

9.14 The central cleaning method using a cleaning machine is considered to be the bestcleaning method because no detergent is required and the water consumption isthe least. However, there is worry from the vehicle operators that it is notconvenient for them.

9.15 In order to provide flexibility for the vehicle operators, an alternative is to allowthem to clean the trap when convenient, such as using the first method mentionedabove. A wastewater collecting tank shall be provided at suitable locations (suchas at fuel filling stations) for them to dispose the waste water.

Cleaning Trial at Fuel Filling Stations

9.16 The two cleaning methods as described in sections 9.14 and 9.15 were put on trialfrom March 2000 to May 2000, involving 17 diesel vehicles, comprising of 11taxis and 6 light diesel goods vehicles.

9.17 The vehicle operators were required to clean the traps at a selected fuel fillingstation using the cleaning machine. Alternatively, they might rinse the trap inwater with detergent and then dispose the wastewater into a wastewater filteringtank installed also at the selected fuel filling stations.

9.18 Feedback from the vehicle owners is that both methods are acceptable if thecleaning machines and the filtering tanks are widely available.

9.19 Wastewater samples were collected and analyzed by the PolyU and the HongKong Productivity Council. Results are shown in Appendix II. All parameters arewell within the required limits. Hence, the quality of wastewater generated byboth cleaning methods can meet relevant EPD discharge standards.

9.20 Assuming 200 cleanings per day, the wastewater generated per day would beabout 1 cubic meter for the cleaning machine and 2 cubic meter for the wastewaterfiltering tank.

10. Cost Implication

10.1. The cost of the particulate trap depends on business factors, which cannot beassessed during this trial program. Despite that, a rough indication is that, if massproduced, the direct cost is around HK$300 per trap. However, the impact onoperating cost can be assessed. This includes effect on fuel consumption, thewastage of the trap and the cleaning cost.

Fuel consumption test

10.2. A LGV was tested on a chassis dynamometer at Apleichau on 24 September 1999.The LGV was operated on the dynamometer at second gear at a vehicle speed of31 km/hr carrying a load of 22 kW. The fuel consumption was measured at 5minutes intervals for 30 minutes. There was a 1.4% increase in fuel consumptionwith the trap, carrying 14 grams of particulate.

10.3. The same LGV was arranged for another fuel consumption test on 9 October 1999.The LGV was driven up the Aberdeen Reservoir Road at a speed of 40 km/hr for alength of about 0.5 km. The fuel consumption was measured with a fuel metershowing the fuel consumed on a per second basis. The test was repeated twicewith a trap containing 12 grams of particulate and then without the trap. Therewas an increase in fuel consumption of 1.5% when the LGV was carrying aloaded trap, which is within the equipment’s order of accuracy.

10.4. The independent test conducted by the National Engine Combustion Laboratory ofthe Tianjin University shows that there is no increase in fuel consumption due tothe trap under the ECE-R49 13 mode test cycle.

The replacement cost of the trap

10.5. The trap is essentially comprised of three components: the connector, the casingand the filter cartridge. Throughout the test period, there were a few cases ofdamage to the connector and the casing due to crush against rams. Otherwise,there was no damage to the connector and the casing. The filter cartridge mightalso be crushed for the same reason. The filter cartridge could deform due tofrequent washing. It is estimated that the connector and the casing can have a lifespan of over one year, while it might be advisable to replace the filter cartridgeonce every six months.

Cleaning cost

10.6. If the traps were cleaned at fuel filling stations using a central cleaning unitwithout the use of detergent, the cost can be very low. If the cleaning unit, theelectricity and the water consumption are sponsored, the cleaning cost on the usersis essentially zero.

10.7. On the other hand, if cleaning is done by individual users using water withdetergent, the cost would be less than HK$1 per cleaning.

11. Drivers' Opinion Survey

Background

11.1. A questionnaire survey was conducted in the trial period of the particulate trap onsmall diesel vehicles. The purpose of the survey is to solicit the drivers' view onthe particulate trap, in particular, the impact of the trap on black smoke emission,fuel consumption and lubrication oil consumption. The questionnaire is enclosedin Appendix III. Totally 62 vehicles participated in the trial program and all thedrivers were given the questionnaire to fill in and returned on a voluntary basis.

A total of 28 completed questionnaires were received.

Results

11.2. The statistical results of the questionnaire answers are also enclosed in AppendixIII.

11.3. 93% of respondents reckoned that the trap was effective in reducing black smoke(Figure 11.1) and 68% observed the change within the first week of trapinstallation.

11.4. 41% of respondents reckoned that there was a slight increase in fuel consumptionwith the trap while 48% did not feel any difference in fuel consumption (Figure11.2). And, 56% felt the change within the first week of trap installation.

11.5. 85% of respondents reckoned that there was only a slight or no decrease ofhorsepower of the vehicles with the trap (Figure 11.3). And, 79% felt the changewithin the first week of trap installation.

11.6. 74% did not feel any change in lubrication oil consumption (Figure 11.4). 3drivers (10%) observed colour change in lubrication oil (probably dirty).

11.7. 53% agreed the filter of the trap should be cleaned every day (Figure 11.5). 8drivers (29%) objected to this suggestion simply because they reckoned that therewas no need to clean the trap filter every day. It could last longer.

11.8. There was no objection to the suggestion that all small vehicles should be fittedwith the particulate trap. 82% supported the suggestion and the rest had no viewon it (Figure 11.6).

Findings

11.9. Absolutely majority of respondents reckoned that the trap was effective inreducing the black smoke emissions.

11.10. The impacts of the trap on fuel and lubricating oil consumption as well as vehiclehorsepower were minimal.

11.11. Absolutely majority of respondents supported the requirements of the particulatetrap on small diesel vehicles and most drivers did not mind to clean the trap filtereveryday.

12. Conclusion

12.1. A feasibility study of retrofitting low cost traps to in-use diesel vehicles wereconducted from July to December 1999. Sixty-two vehicles were retrofitted withthe particulate trap. The effect of the trap on smoke reduction, particulatereduction, back pressure and power loss were evaluated. The problem concerningparticulate release at high engine load, spontaneous soot regeneration and trapcleaning were investigated. Finally, the cost implication and the opinions ofvehicle owners and drivers on the retrofitting of the trap were assessed.

12.2. The trap was found effective in reducing the smoke by about 30%. It was alsoeffective in trapping particulate emissions. The amount of particulate trappeddepended on the kind of vehicle concerned, being higher for the PLBs and lowerfor LGVs.

12.3. The particulate trap and the particulate trapped therein were found to increase theback pressure by a maximum of a few kPa. The average increase per trip shouldbe much lower. Hence, the increase in back pressure should not be a concern.

12.4. Lug-down test conducted on the chassis dynamometer indicated a marginalreduction on the power of the vehicles. During the lug-down tests, it was foundthat about one-third of the particulate trapped could be released. The lug-downtests were carried out mainly with heavily loaded traps. If a particulate trap iscleaned as frequent as daily, it would be less heavily loaded and the particulatereleased would be much less.

12.5. The problem of spontaneous soot regeneration (SSR) is a concern. However, noSSR occurred on LGVs in normal conditions. For the taxis, it was found that thosewith SSR problem could have higher exhaust gas temperature. If the engineconditions were poor, coupling with a high engine power operation and a highparticulate quantity stored in the trap, SSR could occur. However, if the traps werecleaned daily or twice per week, SSR was found to be under control. For the PLBs,by improving the design of the trap, SSR can also be controlled.

12.6. Several cleaning methods had been tried and found to be able to produce goodcleaning effect and the wastewater to be discharged might meet wastewaterdischarge requirements. Two methods have been selected for trial at fuel fillingstations from March 2000 to May 2000. Feedback from vehicle operators is thatboth methods are acceptable. The wastewater generated can also meet relevantstandards governing disposal of wastewater into foul sewers.

12.7. Three tests had been conducted to evaluate the potential increase in fuelconsumption due to the installation of the trap. The percentage increase wasaround 1% at high engine loads. At lower loads, the increase should be lower.Hence the fuel penalty is considered to be negligible.

12.8. Survey results indicated an absolutely majority of respondents reckoned that thetrap was effective in reducing the black smoke emissions. The impacts of the trap

on fuel and lubricating oil consumption as well as vehicle horsepower wereminimal. Absolutely majority of respondents supported the requirements of theparticulate trap on small diesel vehicles and most drivers did not mind to clean thetrap filter everyday.

12.9. In order to avoid build up of excessive back pressure and also to avoid SSR, thetrap users should be properly instructed to clean the trap regularly. For taxis andPLBs, daily cleaning is required. For LGVs, cleaning per refuelling isrecommended.

12.10. It should also be pointed out that the results of specific tests conducted in thisStudy are pertained to the specific test conditions as described in this report.

Table 2.1: Particulars of Taxis

VehicleNumber Manufacturer Model

EngineSize (c.c.)

Year ofManufacture

FirstRegistration

Date

T1 Toyota Crown LS130R 2446 1992 29/07/92T2 Toyota Crown LS130R 2446 1991 30/07/91T3 Toyota Crown LS130 2446 1988 24/08/88T4 Toyota Crown LS130R 2446 1993 28/04/93T5 Toyota Crown LS130R 2446 1992 23/06/92T6 Toyota Crown LS130R 2446 1993 21/06/93T7 Toyota Crown LS130R 2446 1990 26/09/90T8 Toyota Crown LS130 2446 1990 09/12/90T9 Toyota Crown LS130 2446 1990 30/10/90T10 Toyota Crown LS130 2446 1990 19/11/90T11 Toyota Crown LS130 2446 1990 12/12/90T12 Toyota Crown LS130R 2446 1991 28/03/91T13 Toyota Crown LS130 2446 1991 27/09/91T14 Toyota Crown LS130 2446 1992 12/02/92T15 Toyota Crown LS130 2446 1993 02/04/93T16 Toyota Crown LS130 2446 1993 02/04/93T17 Toyota Crown LS130R 2446 1993 26/05/93T18 Toyota Crown LS130 2446 1994 13/05/94T19 Toyota Crown LS130R 2446 1992 27/04/92T20 Toyota Crown LXS10R 2446 1996 01/04/96T21 Toyota Crown LXS10R 2446 1996 01/06/97

Table 2.2: Particulars of Light Goods Vehicles


EngineSize (c.c.)

Year ofManufacture

FirstRegistration

Date

LGV 1 Toyota LH113R 2779 1992 18/02/93LGV 2 Toyota LH113R 2779 1992 22/09/92LGV 3 Toyota LH113R 2779 1990 26/02/90LGV 4 Toyota LH113R 2779 1990 06/03/90LGV 5 Toyota LH113R 2779 1990 01/10/90LGV 6 Toyota LH113R 2779 1991 16/08/91LGV 7 Toyota LH113R 2779 1998 17/07/98LGV 8 Ford ST (2184 c.c.) 2184 1992 27/05/92LGV 9 Ford ST (2184 c.c.) 2184 1993 11/02/93

LGV 10 Toyota LH113R 2779 1993 01/03/93LGV 11 Toyota LH113R 2779 1995 22/11/95LGV 12 Toyota LH113R 2779 1996 19/06/96LGV 13 Toyota LH113R 2779 1997 23/04/97LGV 14 Toyota LH113R 2779 1997 14/05/97LGV 15 Toyota LH172R 2986 1999 11/05/99LGV 16 Ford ST (2500 c.c.) 2500 1997 12/06/97LGV 17 Toyota LH113R 2779 1998 16/07/98LGV 18 Toyota LH113R 2779 1998 17/07/98LGV 19 Toyota LH172R 2986 1998 15/09/98LGV 20 Toyota LH172R 2986 1998 11/09/90LGV 21 Mazda SR 2184 1995 31/03/95LGV 22 Ford ST (2500 c.c.) 2500 1999 14/04/99

Table 2.3: Particulars of Public Light Buses


EngineSize (c.c.)

Year ofManufacture

FirstRegistration

Date

PLB 1 Toyota 14B 3660 1990 01/06/90PLB 2 Toyota 14B 3660 1992 17/08/92PLB 3 Toyota 13B 3431 1986 05/01/87PLB 4 Toyota 13B 3431 1988 16/09/88PLB 5 Toyota 14B 3660 1989 31/03/89PLB 6 Toyota 14B 3660 1989 29/05/89PLB 7 Toyota 14B 3660 1989 21/06/89PLB 8 Toyota 14B 3660 1989 28/09/89PLB 9 Toyota 14B 3660 1989 12/09/89PLB 10 Toyota 14B 3660 1989 06/10/99PLB 11 Toyota 14B 3660 1989 21/12/89PLB 12 Toyota 14B 3660 1990 21/05/90PLB 13 Toyota 14B 3660 1990 31/05/90PLB 14 Toyota 14B 3660 1990 05/07/90PLB 15 Toyota 14B 3660 1990 12/03/91PLB 16 Toyota 14B 3660 1991 29/08/91PLB 17 Toyota 14B 3660 1991 12/02/92PLB 18 Toyota 14B 3660 1992 10/01/92PLB 19 Toyota 14B 3660 1992 13/10/92

Figure 3.1: Basic construction of the particulate trap

Figure 3.2: Taxi with trap in-line with exhaust pipe

Fig 3.3: Light goods vehicle with flexible sleeve

Fig 3.4: Taxi with trap perpendicular to exhaust pipe

Figure 3.5: Particulate trap on a public light bus

Figure 3.6: A taxi with an oval-shaped particulate trap

Figure 4.1: Custom made connector for measuring smoke opacity

Table 4.1: Smoke Opacity of Taxis(Before and after Installation of Particulate Trap)

Smoke Opacity (HSU)VehicleNumber Before

InstallationAfter

InstallationPercentageChange (%)

T 1 45.7 32.4 29.1%T 2 42.3 25.8 38.9%T 3 27.6 21.2 23.2%T 4 22.1 18.0 18.4%T 5 38.8 30.1 22.5%T 6 32.0 22.0 31.4%T 7 40.5 26.8 33.8%T 8 53.0 46.5 12.3%T 9 29.2 16.8 42.4%

T 10 43.8 33.4 23.7%T 11 45.5 38.2 16.1%T 12 31.6 14.3 54.7%T 13 54.4 36.2 33.5%T 14 41.6 23.8 42.8%T 15 25.9 23.7 8.6%T 16 57.3 41.7 27.1%T 17 35.0 13.9 60.2%T 18 47.0 24.3 48.2%T 19 37.4 28.0 25.2%T 20 42.4 36.6 13.6%T 21 48.3 39.8 17.5%

Maximum 57.3 46.5 60.2%

Minimum 22.1 13.9 8.6%

Average 40.1 28.3 29.7%

Table 4.2: Smoke Opacity of Light Goods Vehicles(Before and after Installation of Particulate Trap)


InstallationAfter


LGV 1 32.8 15.4 53.0%LGV 2 24.9 11.8 52.5%LGV 3 23.7 12.6 47.1%LGV 4 47.6 20.5 57.0%LGV 5 51.0 42.6 16.4%LGV 6 28.8 13.6 52.9%LGV 7 31.7 25.3 20.1%LGV 8 42.0 32.0 23.9%LGV 9 76.1 58.0 23.7%

LGV 10 51.9 31.8 38.8%LGV 11 53.0 46.7 11.9%LGV 12 43.1 26.5 38.6%LGV 13 52.1 31.4 39.7%LGV 14 32.6 25.1 22.9%LGV 15 45.1 19.2 57.5%LGV 16 51.8 29.7 42.6%LGV 17 37.0 26.2 29.3%LGV 18 24.7 15.6 36.9%LGV 19 38.3 26.0 32.0%LGV 20 37.5 27.3 27.3%LGV 21 40.9 35.2 14.0%LGV 22 30.2 18.5 38.7%

Maximum 76.1 58.0 57.5%

Minimum 23.7 11.8 11.9%

Average 40.8 26.9 35.3%

Table 4.3: Smoke Opacity of Public Light Buses(Before and after Installation of Particulate Trap)


InstallationAfter


PBL 1 38.3 32.5 15.1%PBL 2 39.8 23.8 40.2%PBL 3 40.5 33.0 18.6%PBL 4 72.8 67.4 7.5%PBL 5 12.1 11.6 4.1%PBL 6 55.9 42.5 24.0%PBL 7 56.9 35.8 37.1%PBL 8 52.0 45.7 12.1%PBL 9 48.8 27.4 43.9%PBL 10 20.0 15.4 23.1%PBL 11 52.4 39.7 24.2%PBL 12 49.7 44.2 11.2%PBL 13 41.1 32.2 21.7%PBL 14 59.8 51.9 13.2%PBL 15 65.8 60.6 7.8%PBL 16 44.5 34.7 22.1%PBL 17 21.5 16.5 23.3%PBL 18 26.4 17.0 35.5%PBL 19 28.4 23.9 15.9%

Maximum 72.8 67.4 43.9%

Minimum 12.1 11.6 4.1%

Average 43.5 34.5 21.1%

Table 4.4: Smoke Opacity of Taxis(Before Installation and after Removing the Trap)

Smoke Opacity (HSU)VehicleNumber Before Test After Test

T 1 45.7 40.7T 2 42.3 17.8T 3 27.6 18.5T 4 22.1 23.8T 5 38.8 27.4T 6 32.0 21.2T 7 40.5 28.0T 8 53.0 41.5T 9 29.2 28.2

T 10 43.8 -T 11 45.5 37.1T 12 31.6 33.0T 13 54.4 64.2T 14 41.6 33.7T 15 25.9 24.8T 16 57.3 29.8T 17 35.0 27.3T 18 47.0 32.4T 19 37.4 46.3T 20 42.4 50.7T 21 48.3 39.7

Maximum 57.3 64.2

Minimum 22.1 17.8

Average 40.1 33.3

Table 4.5: Smoke Opacity of Light Goods Vehicles(Before Installation and after Removing the Trap)

Smoke Opacity (HSU)VehicleNumber Before Test After Test

LGV 1 32.8 8.0LGV 2 24.9 19.4LGV 3 23.7 5.2LGV 4 47.6 26.9LGV 5 51.0 30.4LGV 6 28.8 21.9LGV 7 31.7 16.8LGV 8 42.0 65.8LGV 9 76.1 56.7

LGV 10 51.9 18.4LGV 11 53.0 44.8LGV 12 43.1 14.7LGV 13 52.1 15.6LGV 14 32.6 69.4LGV 15 45.1 17.0LGV 16 51.8 14.9LGV 17 37.0 31.7LGV 18 24.7 14.6LGV 19 38.3 50.1LGV 20 37.5 30.1LGV 21 40.9 82.5LGV 22 30.2 54.8

Maximum 76.1 82.5

Minimum 23.7 5.2

Average 40.8 32.3

Table 4.6: Monthly FAS Test of Taxis

At the End of First Month At the End of Second MonthVehicleNumber Date

Without Trap(HSU)

With Trap(HSU)

PercentageChange (%) Date

Without Trap(HSU)

With Trap(HSU)

PercentageChange (%)

T6 29/09/99 47.3 39.7 16.1% 20/10/99 22.1 19.2 13.4%

T 7 28/09/99 52.0 41.0 21.2% 26/10/99 46.4 38.4 17.2%

T 11 29/09/99 68.3 56.3 17.6% 20/10/99 43.1 41.9 2.8%

T 13 27/09/99 94.3 80.5 14.6% 18/10/99 56.3 42.5 24.6%

T 14 27/09/99 53.5 39.7 25.8% 18/10/99 38.3 31.2 18.7%

Table 4.7: Monthly FAS Test of Light Goods Vehicles

At the End of First Month At the End of Second MonthVehicleNumber Date

Without Trap(HSU)

With Trap(HSU)

PercentageChange (%) Date

Without Trap(HSU)

With Trap(HSU)

PercentageChange (%)

LGV 3 27/09/99 42.2 13.9 67.1% 25/10/99 39.2 24.8 36.6%

LGV 4 28/09/99 57.2 44.3 22.5% 01/11/99 41.6 25.6 38.4%

LGV 7 27/09/99 49.2 33.3 32.2% 25/10/99 23.2 13.1 43.8%

LGV 10 12/10/99 42.9 24.1 43.9% 09/11/99 39.6 27.4 30.7%

LGV 18 04/10/99 30.8 23.5 23.8% 08/11/99 25.3 15.3 39.5%

Figure 5.1: Particulate Collected During First Week of Trial (Taxis)

Figure 5.2: Particulate Collected During First Week of Trial (Taxis)

Figure 5.3: Particulate Collected During the First Week of Trial (LGVs)

Figure 5.4: Particulate Collected during the First Week of Trial (LGVs)

Figure 5.5: Weekly Particulate Collection Trend of Taxis

0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500 3000 3500 4000

Mileage

Par

ticul

ate

(g)

Week 18

Week 9

Week 17

Week 2

Week 11

Week 12

Week 7

Week 3

Week 4

Week 8

Week 5Week 13

Week 16

Week 1

Week 6

Week 14

Week 10

Week 15

Figure 5.6: General Particulate Collection Trends of Different Categories of Vehicles

Figure 8.1: Two typical filter cartridges after spontaneous regeneration of soot

Figure 8.2: A filter cartridge with minor spontaneous regeneration of soot

Figure 9.1: Filter cartridge immersed in water

Figure 9.2: Filter cartridge shaken in a bucket of water, manually

Figure 9.3: Filter cartridge shaken in a bucket of water, pneumatically

Figure 9.4 Cleaning a filter cartridge with a water-flushing machine

Table 9.1: Effectiveness of Various Cleaning Methods

VehicleNumber

Cleaning MethodStarting

DateTermination

DateNumberof Days

Number ofCleanings

WeightDuring

Installation (g)

WeightAfter Last

Cleaning (g)

WeightDifference

(g)

T 14 Hand Shaking 29/11/1999 24/12/1999 25 19 824 825 1T 15 Hand Shaking 30/11/1999 14/12/1999 14 11 643 642 -1T 16 Mechanic Spouting and Spinning 29/11/1999 13/12/1999 14 12 846 849 3T 18 Mechanic Spouting and Spinning 29/11/1999 24/12/1999 25 20 662 664 2T 20 Mechanic Shaking 03/12/1999 24/12/1999 21 16 850 851 1T 21 Mechanic Shaking 03/12/1999 24/12/1999 21 16 859 864 5

Figure 9.5: Particulate Collected before Each Cleaning (6 Vehicles)

Appendix I小型柴油車微粒過濾器試驗計劃

監察委員會

環保署﹝主席﹞ 莫偉全

理工大學﹝秘書﹞ 熊永達理工大學張鎮順﹑盧覺強﹑陳瑞齡﹑全鎮華

環保署夏港﹑孔憲榮

運輸署源浩昌﹑鄧北海﹑莫少堅﹑

狄荔義(D.T. Deacon)

汽車商會聯會,MTA Mike Rushworth汽車商會聯會崔慶銓﹑劉啟成﹑何世洪﹑譚偉

良﹑區紹禧﹑崔永生

九龍的士車主聯會任太平﹑溫卓明

香港客貨車業員職工會葉滿林

聯友的士同業聯會歐陽根﹑劉錫禧的士、小巴、貨車、學童車大聯盟吳國雄

交通事業從業員協會宋景鴻

薄扶林專線小巴公司陳智勤

綠色專線小巴總商會黃潤輝

的士權益協會陳劍峰﹑黃濤

的士同業聯會有限公司梁平寬城市的士車主司機聯會覃友忠﹑梁錦泉

香港九龍的士貨車商會鄭漢桂﹑譚盈滿

西頁的士工商聯會劉克溪

香港九龍新界公共專線小型巴士聯合總商會梁雄﹑譚俊達

屯門小型巴士商會許兆強香港專線小巴持牌人協會陳文俊

褓姆車司機協會吳王家榮﹑黃麗華

香港的士小巴總商會譚寶玉﹑葉慶華

港九電召的士車主聯會黃禧平

運輸界千禧年環保行動籌備委員會召集人劉健儀議員

職權範圍

1. 監察由理工大學推行的小型柴油車微粒過濾器試驗計劃的實施。2. 審閱與試驗計劃有關的資料和報告。

3. 就試驗計劃的安排提供意見及協助。

4. 反映業內人士對試驗計劃的意見。

Appendix II

Summarized Result of Quality of Wastewater Samples Collected on May 20, 2000 atKowloon Bay Mobil Fuel Filling Station

(Sample analyzed by the Environmental Management Division Laboratory of the HongKong Productivity Council)

Parameters Analyzed Results Limits specified in TMPH 7.3 6 – 10Total Suspended Solids 100 mg / L 1200Settleable Solids 11 mg / L 100BOD 120 mg / L 1200COD 390 mg / L 3000Oil & Grease < 10 mg / L 100Iron 5.2 mg / L 30Boron 0.2 mg / L 8Barium < 1 mg / L 8Mercury < 0.5 µg / L 0.2 mg / LCadmium < 0.02 mg / L 0.2Copper < 0.1 mg / L 4Nickel < 0.1 mg / L 4Chromium < 0.1 mg / L 2Zinc 1.8 mg / L 5Silver < 0.1 mg / L 4Other Toxic Metals @ 2.5 mg / L

Arsenic 1.9 µg / LAntimony < 3 µg / LBeryllium < 0.2 µg / L

Manganese 0.4 mg / LLead < 0.1 mg / L

Selenium < 2 µg / LThallium < 5 µg / L

Vanadium < 2 µg / LTotal Toxic Metals 10Cyanide < 0.05 mg / L 2Phenols < 0.1 mg / L 1Sulphide 0.2 mg / L 10Sulphate 53 mg / L 1000Total Nitrogen 3.1 mg / L 200Total Phosphorus 17 mg / L 50Total Surfactants 86 mg / L 200

Appendix III

Figure 11.1: Impact on black smoke emissions

Figure 11.2: Impact on fuel consumption

Figure 11.3: Impact on vehicle horse-power

Figure 11.4: Impact on lubrication oil consumption

Figure 11.5: Willingness to wash trap filter daily

Figure 11.6: Support requirement of trap on small diesel vehicles

Documents

Feasibility Study of Retrofitting Low Cost Traps to in-use ......feasibility study includes a trial program of testing 62 in-use diesel taxis, diesel light buses and diesel light goods