Cleaning of Atmospheric Air in a City Street and Road Network as an Environmental Safety Technology for Road Transport

Cleaning of Atmospheric Air in a City Street and Road Network as an Environmental Safety Technology for Road Transport

Available online at www.sciencedirect.com ScienceDirect Transportation Research Procedia 20 (2017) 200 – 204 12th International Conference “Organiza...

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Available online at www.sciencedirect.com

ScienceDirect Transportation Research Procedia 20 (2017) 200 – 204

12th International Conference “Organization and Traffic Safety Management in Large Cities”, Saint Petersburg, 28–30 September 2016

Cleaning of Atmospheric Air in a City Street and Road Network as an Environmental Safety Technology for Road Transport Vitaly Fedotov*, Albyna Gorbacheva, Anna Dorodnikova, Maria Yerokhina Saint Petersburg Mining University, 2, 21st Line, St Petersburg 199106, Russia

Abstract: The article provides scientific basis for a new innovative concept of cleaning the polluted ambient air in a city road network during road transportation and a calculative model for changes in concentrations of polluting agents for mobile cleaning units used as part of road traffic flow. The article describes the design of equipment (reactor) used to decontaminate the toxic components of exhaust gas and disperse particles and explains its difference from the existing facilities by its function to clean the air within a city highway with a wide speed range of dust and exhaust gas flows (proved by two patents of the RF: No.2237816, No.3231858). © Published by Elsevier B.V. This © 2017 2016The TheAuthors. Authors. Published by Elsevier B.V.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th International Conference "Organization and Traffic Peer-review under responsibility of the organizing committee of the 12th International Conference “Organization and Traffic Safety Safety Management in large cities". Management in large cities” Key words: Road transport, environmental safety, city street and road network, UV-reactor and electric filter package

1.

Introduction

When we consider city ground transport systems, road transport in particular, as a means of transportation for city dwellers we can distinguish several components of this special process of road transportation: – main process: transportation – moving of material objects (passengers and cargoes); – auxiliary processes: maintenance of functional status of rolling stock, city road network, infrastructure, traffic safety, decrease in the level of polluting agents as a result of transportation services (exhaust gases, solid particles, noise, electromagnetic radiation, service and repair waste materials)

* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: [email protected]*

2352-1465 © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th International Conference “Organization and Traffic Safety Management in large cities” doi:10.1016/j.trpro.2017.01.052

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Objective necessity for using of engineering methods to decrease the concentration of polluting agents in ambient air of city street and road network. There are commonly known traditional ways of decreasing the mass of polluting agents in the traffic flows. These include improving environmental safety of vehicles (packaging with electric motors, electronically control engines and three stage exhaust gas reactors, emission monitoring during operation, usage of advanced and alternative fuels); improvement of the transportation process (usage of buses with large passenger capacity, distribution of traffic flows according to their carrying capacity); mitigation of unsteady operation modes of engines (construction of continuous traffic highways, road junctions in different levels, underground crossings, etc.). As we have stated in [Fedotov (2011)], technical solutions implemented to decrease the emission level of the combustion engines should significantly limit the impact of polluting agents on the quality of the city ambient air in the immediate future. At the same time, the emissions caused by the wear of brake parts, tyre protectors and wear of road surface (fractions РМ10 – РМ2,5) by road transport still remain the major sources of pollution which require effective strategies for their removal.

2. Main part The calculations made according to the western procedures for environmentally friendly external conditions which are close to the European ones (good quality of roads, contamination of the road surface with suspended particles of 0.4 g/mg3) yielded the following emission values of РМ-particles: 0.04–0.12 g/km and 0.20–0.80 g/km for each passenger and commercial car (with carrying capacity of more than 9 t), respectively, for a speed range of 20–50 km/h, typical for a road network in Saint Petersburg and other large cities [Denisov (2013)]. Table 1 gives concentration values for polluting agents for a length of 2000 m of the road network of a large city with traffic density of 50–60 cars/km (1000–1200 cars/h) with adjacent buildings (average number of floors of 7–12; building density of 70–80%) and wind speed of 2–5 m/s. Emission of РМ-particles in traffic flow amounted for passenger cars to 63–72 g/km, for buses and commercial cars to 120–150 g/km [Fedotov (2011)]. Table 1. Concentration of polluting agents within a length of the road network of a large city (for Volgograd as an example). Assessment points for concentration of polluting agents At the edge of a highway at an elevation of 0.4–2.0 m In the center of traffic flow

Concentration values of polluting agents according to the measurements [Fedotov (2011)] 3.7–5.6 mg/m3, including total concentration of solid particles 0.28 – 0.41 mg /m3, concentration of РМ-10 particles and lower 0.14–0.24 mg/m3 12.2–18.1 mg/m3

Concentration values of polluting agents according to calculations 2.1–3.5 mg/m3 31.6–40.7 mg/m3

Near the ground concentrations of polluting agents can be increased by 2-3 times due to unfavourable weather conditions which include still air, fog, dangerous wind direction and speed, trapping layers, high air temperature. Estimate calculations for unfavorable weather conditions with equations proposed by the author in [Fedotov (2012)] are in line with the figures and conclusions given in [Fedotov (2011)]. With the traffic intensity of 1000–1500 cars/h (more than 90 % of road transport with category М1, М2, М3) the volumes of air polluted with exhaust gases and solid particles with a three lane traffic in concentrations which make harmful effect on human body can amount to: 60–72 th. m3/h with an average height of air passage of 2.8-3.2 m, (99% of the mass of impurities dissipate in the volume) per 1 km of a highway in the city center and other districts with a dense residential development. Such volumes of polluted air in a city street and road network are comparable with emission levels of polluting agents during production of metal, cement, gas and coal combustion where special air cleaning methods are used [Fedotov (2012)]. These figures prove the urgency for developing the air cleaning system within city highways to clean the air from polluting agents of traffic flows. Road transport dust and gas emission cleaning system. We designed a reactor for cleaning the air from solid and gaseous particles to be moved in traffic which is covered by the patent of the RF [Komarov et al. (2008)]. The reactor has a dust and gas flow speed damper and a conical gas duct which ensure a narrow speed range and an onward movement of dust and gas flow in the reactor, Fig. 1.

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Fig. 1. Reactor for cleaning the air from solid and gaseous particles [Savinov (2007)].

Continuous operating time of removable collector (maintenance frequency) depends on physical and mechanical properties of dust and the total area of collecting electrodes.

Functional components of reactor

Table 2.Reactor operating stages and performance. I

II and III

IV

V

Speed damper. When passing through the speed damper, the dust and gas flow attains progressive rotation which reduces the speed and decreases the max to min ratio of speed values by 1.5 – 2.0 times.

UV-lamp. Dust and gas flow running at a rate of 0.1–0.5 m/s when exposed to UV radiation shows atomization of the molecules of toxic gases and recombination of active atoms N, O, C into steady molecules N2, CO2, H2O. When photocatalysts are used for UV-decontamination, the efficiency of cleaning the air from СО and NO reaches at least 60%, and for СН and benzpyrene – at least 90% [Savinov (2007)].

Spiral gas duct. The mixture of cleaned gas and disperse particles moving along the spiral duct due to centrifugal forces separates by mass into mineral dust, soot particles sized from 5 to 20 microns which will further go to the first cavity of the collector 6. Adjusting the deflection angle of the spirals changes the screw motion of the flow to the onward motion and reduces the flow speed to 0.5 m/s at the outlet of the gas duct.

Electric filter. Gas cleaned partly from disperse particles will be filtered through a fine mesh diaphragm 7 and goes to the second cavity of the collector – electric filter 8. Clean gas leaves the collector through the hole 11. Electric filter performance for trapping the disperse particles is at least 90% [Aliev (1986)]

The proposed design of the decontamination reactor for dust and gas flows can be used as a universal one. Model for calculating the changes in concentration of polluting agents in the air for mobile air cleaning units. The option for equipping the trolley-buses with cleaning reactors was described in [Fedotov (2011/2007)]. The equation for calculating the required performance of mobile cleaning units was also given there:

KdpTSN NTSN dV 

dQZV D ˜ ’c ˜ dt

(1)

where η – effectiveness ratio of cleaning units; NТСН – traffic intensity of transport vehicles; dQzv – mass of polluting agents within a time period dt; D – diffusion coefficient of polluting agents; ’с – concentration gradient of polluting agents. The benefits of installing a battery of reactors on a trolley-bus compared to such standard sites as city street and road networks and special transport are obvious enough (in middle term perspective). The ongoing activities are

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targeted at solving the issue with the power supply of cleaning units due to recovery of electric power and other methods, preventing air contamination with toxic components of exhaust gases, the capacity of the lanes is not affected by special transport and last but not least trolley-bus schedule and general intensity of traffic flow can be regulated only by a single factor namely passenger flow requirements. According to the data of http://trollcity.narod.ru/stat.htm/26.12.2014 there are 88 large cities in the RF with existing trolley-bus traffic and total number of routes of 954. Let's take a model for calculating the changes in concentrations of polluting agents in the air for air cleaning units which are carried as part of the road transport flow. Cleaning units carried as part of the traffic flow and effecting the concentrations of polluting agents become the sources of irregularity gradient in air density, Fig.2. In this case calculating the required performance of the cleaning process shall account for space and time limits of flows of mobile cleaning units and cars as interacting line sources which affect air density.

Fig. 2. Carrying of mobile cleaning units in traffic flows in a city highway.

In [Fedotov (2011)] the authors came to a conclusion that trolley-buses carrying the cleaning units as elementary impact sources create a special transport flow which reduces the density of polluting agents in the air. Furthermore: “…The factor of reducing concentrations of polluting agents in a highway allows to represent the cleaning process by a special transport flow as an impact of a line source on the thermodynamic system (ambient air – author's note). In this case the length of an impact source is in line with the length of a highway section. The line impact source shall be positioned along the axis of the traffic lane of the transport carrying the cleaning units. Surface width dimensions of the line impact source and its elevation relative to the road surface depend on the design of the cleaning units and the carrier vehicle as well as traffic safety rules. The surfaces of this line source decontaminate the mass of polluting agents which is uniformly distributed along the length of the line source. Such a mass of decontaminated emissions can be represented as a conditional mass equal to the mass of decontaminated polluting agents with a reverse sign. The gradient of the negative mass of decontaminated emissions goes towards the decrease of density of negative concentrations. So, if a thermodynamic system has two line sources of masses of polluting agents and decontaminated emissions which are the focus in the initial condition (t = 1 s) for the positive and conditional negative masses, then it is clear that every point R of a thermodynamic system can be characterized by concentration values ±С [mg/m3]. Presuming that the functions +С (R1) и – С(R2) are in the same space and time limits, the combination of masses of polluting agents and decontaminated emissions within a length of a highway can be shown a an interaction of two scalar fields of concentrations С = С (x, z) with the gradients of reverse directions. …”.

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Therefore, we can assume that the values of density of contaminants in each point of the ambient air within an area of a highway specified by the functions of concentrations СПМ and СОМ can be represented by the summing function С∑ of a flat linear field with the gradient calculated by the equation:

grad СPM  ( 䒾 grad СOM )

grad (СPM 䒾 СOM )

gradѦ ,

(2)

where СPM and СОM – functions of concentrations, respectively, of positive mass (PМ) and negative mass (ОМ) in the points of ambient air within the area of a highway. After the polluting agents are decontaminated by the cleaning units their concentrations in the air shall not exceed the maximum allowable limits of concentrations of j harmful agent СjPDK. Then the calculating model for an emission decontamination process in the traffic with cleaning units in a highway can be represented by a balance equation with the summing function of the coordinates of points of concentration of two scalar fields and a constant value СпрPDK – maximum allowable concentration, corrected for one of the components of polluting agents:

сpm хpm ,z pm –com хom ,zom СprPDK .

3.

Conclusion

The proposed concept of environmental safety of road transport in big cities which integrates environmental requirements into the transportation process is considered as a perspective approach to operating of road transport as well as traffic management with intellectual transport systems, usage of alternative fuels and advanced car motors and engines. References Aliev, G.M. (1986). Techniques of dust collecting and cleaning of industrial gases, Moscow: Metallurgy, 544 p. Denisov, V.N., Kopytenkova O.I. (2013). Modern views on polluted atmosphere of urban areas. Road traffic power, (45): 93–95. Fedotov, V.N., Denisov, V.N. (2011). Engineering method of air cleaning of a city street and road network. Ambient air protection. Atmosphere, (3): 54–59. Fedotov, V.N. (2012). Experimental and analytical determination of propagation rate of the front of polluting agents in traffic flow. Bulletin of civil engineers, 5(34): 204–210. Fedyanov, E.A., Fedotov, V.N., Rysakov A. A. (2007). Selection of places for installation of equipment for cleaning of air from harmful emissions in highways. Safety of living, (12): 26–28. Komarov, Y.Y., Rysakov, A.A., Fedotov. V.N. (2008). Patent 2318580 RF, MPK В 01 D 50/00, 53/74. Decontamination reactor for toxic components of gas emissions with disperse particles. VolgTGU. Savinov, E.N. (2007). Photocatalytic methods of water and air cleaning. Available at: http://www.aerolife.ru/ Articles/fotocataliz_Aerolife.doc (viewd on: 15/05/2016) (in Russian).