Effect of H2S on the S-PAH formation during ethylene pyrolysis

The effect of the H2S presence on the formation of six different sulphurated polycyclic hydrocarbons (S-PAH), during the pyrolysis of ethylene-H2S mixtures, has been studied in a tubular flow reactor installation. Experiments with different inlet H2S concentrations (0.3, 0.5 and 1%) and temperatures of reaction (between 1075 and 1475 K) have been carried out. The 16 compounds that the Environmental Protection Agency (EPA) has stated as EPA-PAH priority pollutants were also analysed. EPA-PAH compounds were the majority of quantified PAH, and also S-PAH were found and quantified. For temperatures studied, the S-PAH/EPA-PAH ratio values showed a maximum value at 1075 K and a minimum value at 1175 K. With respect to the effect of the inlet concentration of H2S, the S-PAH/EPA-PAH ratio values increased with the increase of the H2S concentration

Exploratory study of polycyclic aromatic hydrocarbons occurrence and distribution in manure pyrolysis products

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAH) have been investigated in the products derived from the pyrolysis of pig manure at low temperatures (<550 °C) in a fixed bed reactor. The focus was on the sixteen PAH identified as priority pollutants by the US Environment Protection Agency (EPA). The pyrolysis does not generate a significant additional amount of EPA-PAH to that existing in the original pig manure, under the operational conditions studied (<550 °C). While the total EPA-PAH yield does not indicate a notable dependence on the pyrolysis temperature, the EPA-PAH distribution among the three pig manure pyrolysis products as well as the speciation changed significantly with the temperature. The proportion of heavy PAH species increased as the temperature increased. The initial EPA-PAH in the manure samples plays a significant role in both their concentration and speciation in the biochar. The relationship of the EPA-PAH concentration and speciation in the biochar with those of the raw material was corroborated with a cow manure sample and the biochars obtained from its pyrolysis. For this reason, feedstocks with low EPA-PAH concentrations are recommended in order to obtain biochars with concentrations below the maximum allowed threshold established for their use as a soil enhancer by the International Biochar Initiative (IBI) and in the European Biochar Certificate

Mercury release and speciation in chemical looping combustion of coal

In the in situ Gasification Chemical Looping Combustion of coal (iG-CLC), the fuel is gasified in situ in the fuel reactor and gasification products are converted to CO2 and H2O by reaction with the oxygen carrier. This work is the first study on mercury release in Chemical Looping Combustion of coal. The fraction of the mercury in coal vaporized in the fuel reactor depended mainly on the fuel reactor temperature and the coal type. In the fuel reactor, mercury was mainly emitted as Hg0 in the gas phase and the amount increased with the temperature. In the air reactor, mercury was mostly emitted as Hg2+. In a real CLC system, mercury emissions to the atmosphere will decrease compared to conventional combustion as only mercury released in the air reactor will reach the atmosphere. However, measures should be taken to reduce Hg0 in the CO2 stream before the purification and compression steps in order to avoid operational problems.The authors thank the Government of Aragón and La Caixa (2012-GA-LC-076 project) and the Spanish Ministry for Science and Innovation (ENE2010-19550 project) for the financial support. P. Gayán thanks CSIC for the financial support of the project 201180E102. The authors also thank to Alcoa Europe-Alúmina Española S.A. for providing the Fe-enriched sand fraction used in this work. G. Galo is acknowledged for his contribution to the experimental results.Peer reviewe