No abstract

Renewable natural gas (RNG), produced from biogas upgrading, is an important alternative to fossil fuels. Unfortunately, RNG contains several trace contaminants, one being NH 3 , of particular concern for RNG produced from farming operations. The presence of NH 3 in RNG, particularly if it is injected into the natural gas (NG) pipeline network, could have serious consequences, ranging from damage to the NG infrastructure, to corrosion of the end-user equipment, and increased pollutant formation during combustion. This paper is part of a broader investigation studying all such impacts, the focus here being pollutant emissions. Two common end-user equipment were tested: An internal combustion engine and a household water heater, both operating with NG injected with NH 3 with concentrations ranging from 0 to 500 ppmv. Emissions studied included unburned hydrocarbons (UHC), CO, and nitrogen oxides (NO x ), the latter being of key concern. The presence of NH 3 resulted in increased NO x emissions for both equipment. For the water heater, the relationship between the amount of NO x formed and the NH 3 concentration was quantitative: For every molecule of NH 3 fed to the water heater, one molecule of NO x was additionally produced. However, for the engine a lower quantity of NO x was formed, to that corresponding to complete conversion. The results with both devices are significant, indicating the need for thorough RNG purification prior to its injection into the NG network.

We present here a preliminary experimental study of a novel reactor configuration, consisting of a membrane reactor (MR) followed by two adsorptive reactors (ARs) in parallel, operating alternately, utilized for the production of high-purity hydrogen with simultaneous CO2 capture during the water–gas shift (WGS) reaction treating a coal gasifier off-gas. In the study, we used a commercial sour-shift WGS catalyst (Co/Mo/Al2O3) in both the MR and the AR. A carbon molecular sieve (CMS) membrane was used in the MR, and a hydrotalcite adsorbent was used in the AR. The experimental results show that membrane, catalyst, and adsorbent all operated stably under the integrated gasification combined cycle (IGCC)-relevant conditions. The MR–AR reactor sequence displayed performance superior to that of a conventional packed-bed reactor (PBR) with near 100% conversions attained while the ARs are functional (with an ultrapure hydrogen stream exiting the AR and permeate-side hydrogen purities from the MR of ∼75–80%). Thus, these findings manifest the ability of the hybrid MR–AR process configuration to operate properly under the desired conditions and to intensify the efficiency of the WGS reaction, as well as to validate its potential to function as a high-efficiency, ultra-compact process for incorporation into IGCC power plants for environmentally benign power generation with pre-combustion CO2 capture.

No abstract

Experimental and computational study of the mechanism of conversion, via pyrolysis, of pV4D4 films into silica ceramics and of the impact of preparation conditions on their final structure.