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Bitumen
Published in A. Bahurudeen, P.V.P. Moorthi, Testing of Construction Materials, 2020
Tar is another binder used in the construction of flexible pavement. However, it is rarely preferred in current practices. Tar is obtained by the destructive distillation of coal. Due to its severe harmful gas emission effect, its usage has been proscribed by several government agencies all over the world.
Asphalt Binders
Published in M. Rashad Islam, Civil Engineering Materials, 2020
On the other hand, tar is obtained from crude petroleum vapor and from the bituminous coal destructive distillation. Asphalt material is primarily used in asphalt pavement road construction, whereas tar is primarily used for waterproofing membranes in roofs and pavement treatment, especially in parking lots where fuel spills may dissolve the asphalt. Tar is no longer used for road construction because of its health hazards (such as eye and skin irritation) and high-temperature susceptibility. Carbon and hydrogens are the main elements present in asphalt binder (Peterson 1984). Some other minor elements present are sulfur, nitrogen, oxygen, and occasionally vanadium and nickel are found (Halstead 1985).
Environmental Impacts of Biofuel-Fired Small Boilers and Gasifiers
Published in Mateusz Szubel, Mariusz Filipowicz, Biomass in Small-Scale Energy Applications: Theory and Practice, 2019
Jozef Viglasky, Juraj Klukan, Nadezda Langova
The tars in particular, as well as the condensates, are toxic and require careful evaluation of their occupational and safety aspects. Little research has been carried out to determine the mutagenic and carcinogenic effects of biomass tar, but research on coal tar has confirmed the above reservations. It would be prudent to assume that some of the tar components may be carcinogenic. High-temperature gasifier operation can increase these problems, since the mutagenic and carcinogenic effects are related to the presence of polycyclic aromatics and their relative concentrations increase as process temperature increases. Direct contact between skin and tars or condensate, clothing and complete instruction.
Experimental investigation on a jet impingement scrubber to clean producer gas from biomass gasifier
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Biomass gasification is a process used to generate liquid or gaseous fuel production. It is a thermo- chemical process used to generate useful gas from biomass and these gases basically called as PG which consists of H2, CO, CO2, CH4, N2 and H2O. From this application, PG needs to cool down and reduce tar (Jain 2000). A main technical obstacle is to remove T&P from the PG. Biomass gasifier generates organic matter such as tar which is black in color (Devi et al. 2005). Tar can be classified into two main categories: light tar and heavy tar. Light tar is water soluble which is a mixture of phenol and Naphthalene. At the lower gas temperature, heavy tar will condense, causing clogging and fouling (Maniatis 2000). In this study, both heavy and light methods were effective in getting rid of both types of tar. Different tar removal methods had to be researched since light tar typically exists as a vapor and heavy tar typically exists as droplets (Bergman and Boerrigter 2002).
Experimental investigation of tar recycling in pilot-scale down-draft biomass gasifiers: prospects, operating procedures, process variations, and controls
Published in Biofuels, 2023
Haider A. Al-Rubaye, Jia Yu, Joseph D. Smith, Hasan J. Al-Abedi
Tar is a complex organic mixture of condensable liquids, which are generally considered a byproduct of the coal or biomass gasification processes. Tar will result in 1) the shutdown of gasification facilities, internal combustion engines, and turbines; 2) loss of the heating value of the produced syngas; and 3) environmental pollution due to the toxicity of aromatic hydrocarbons. Gasification processes usually produce a significant amount of tar: around 2 g/Nm3 for downdraft gasifiers [1], 10-15 g/Nm3 for updraft gasifiers [2], and 10 g/Nm3 for circulating fluidized beds (CFB) [3]. However, the maximum concentration of tar for a stable-operated internal combustion engine must be less than 0.1 g/Nm3 [4, 5]. The tar compositions create process inefficiencies, such as pipeline corrosion and blockage, therefore, it must be cleaned from the syngas before feeding it to downstream facilities. Tar removal is considered the most significant challenge for produced syngas utility [6].
Environmental impact of rejuvenators in asphalt mixtures containing high reclaimed asphalt content
Published in Road Materials and Pavement Design, 2022
M. Muñoz, R. Haag, R. Figi, C. Schreiner, M. Zaumanis, M. C. Cavalli, L. D. Poulikakos, N. V. Heeb
In the past, coal derived tar was widely used as a binder for asphalt mixtures instead of crude oil-based bitumen. PAH contents in coal tar-based materials are up to three orders of magnitude higher than those in bituminous asphalt mixtures (Birgisdóttir et al., 2007). Tar-containing asphalt with more than 0.1% coal tar is classified as hazardous waste in Europe (Turk et al., 2014). Therefore, the risk of high PAH contents from tar-containing material arises and must be assessed whenever RAP material is reused. Although the use of coal tar is banned in Switzerland, still some older roads and the reclaimed material contain tar. Current regulations according to Swiss guidelines (BAFU, 2006) specify that RAP can only be reused if the content of the 16 priority PAHs is below 250 mg/kg in asphalt, which is about equivalent to <5000 mg/kg in binder, otherwise, its use is prohibited. It is expected that these regulations will be tightened in the near future. Figure 1 displays chemical structures of those 16 PAHs considered as priority pollutants by the US EPA (2009). Eight of them are genotoxic according to the IARC (International Agency for Research on Cancer).