scholarly journals Evaluation of a membrane permeation system for biogas upgrading using model and real gaseous mixtures: The effect of operating conditions on separation behaviour, methane recovery and process stability

2018 ◽  
Vol 185 ◽  
pp. 44-51 ◽  
Author(s):  
Nándor Nemestóthy ◽  
Péter Bakonyi ◽  
Eszter Szentgyörgyi ◽  
Gopalakrishnan Kumar ◽  
Dinh Duc Nguyen ◽  
...  
Adsorption ◽  
2020 ◽  
Author(s):  
Ester Rossi ◽  
Giuseppe Storti ◽  
Renato Rota

Abstract Among the adsorption-based separation processes for gaseous mixtures, those exploiting pressure variations, so-called Pressure Swing Adsorption (PSA) processes, are the most popular. In this work, we focus on the specific PSA configuration known as Dual Reflux-Pressure Swing Adsorption (DR-PSA) given its ability to achieve sharp separations. In the case of binary mixtures, an analytical approach based on Equilibrium Theory has been proposed to identify the operating conditions for complete separation under the assumption of linear isotherms. This same approach is not available when the separation is not complete. Accordingly, in this work we study the features of non-complete separations by solving numerically a general DR-PSA model with parameter values suitable to approach equilibrium conditions (no mass transport resistances, no axial mixing, isothermal conditions and no pressure drop), thus reproducing the analytical solution when complete separations are examined. Even for non-complete separations, triangularly shaped regions at constant purity can be identified on a plane whose axes correspond to suitable design parameters. Moreover, we found a general indication on how to select the lateral feed injection position to limit the loss in product purities when complete separation is not established, whatever is the composition of the feeding mixture. Finally, a sensitivity analysis with respect to pressure ratio, light reflux ratio and heavy product flowrate is proposed in order to assess how to recover product purities according to the specific degrees of freedom of a DR-PSA apparatus.


2008 ◽  
Vol 58 (4) ◽  
pp. 789-793 ◽  
Author(s):  
D. P. Cassidy ◽  
P. J. Hirl ◽  
E. Belia

Methane production from condensed distillers' solubles (CDS, or syrup), a co-product of ethanol production, was studied in 2-l anaerobic sequencing batch reactors (ASBRs) under 10 different operating conditions. Methane production and COD removal were quantified under steady state conditions for a wide range of operating parameters. COD removals of 62–96% were achieved at OLRs ranging from 1.5–22.2 g COD l−1 d−1, SRTs from 8–40 d, and F/M ranging from 0.37–1.95 g COD g−1 VSS d−1. The methane content of the biogas varied from 57–71% with 0.27 l CH4 produced per g of COD removed. Approximately 54% of the COD fed to the ASBRs, and 83% of the COD removed in the ASBRs was converted to methane. Microbial yield (Y) and decay (b) constants were determined to be approximately Y = 0.127 g VSS g−1 COD removed and b = 0.031 d−1, respectively. Methane recovery from ethanol co-products can reduce the cost and the fossil fuel consumption of ethanol production.


2017 ◽  
Vol 35 (6) ◽  
pp. 669-679 ◽  
Author(s):  
Jessica L Linville ◽  
Yanwen Shen ◽  
Patricia A Ignacio-de Leon ◽  
Robin P Schoene ◽  
Meltem Urgun-Demirtas

A modified version of an in-situ CO2 removal process was applied during anaerobic digestion of food waste with two types of walnut shell biochar at bench scale under batch operating mode. Compared with the coarse walnut shell biochar, the fine walnut shell biochar has a higher ash content (43 vs. 36 wt%) and higher concentrations of calcium (31 vs. 19 wt% of ash), magnesium (8.4 vs. 5.6 wt% of ash) and sodium (23.4 vs. 0.3 wt% of ash), but a lower potassium concentration (0.2 vs. 40% wt% of ash). The 0.96–3.83 g biochar (g VSadded)-1 fine walnut shell biochar amended digesters produced biogas with 77.5%–98.1% CH4 content by removing 40%–96% of the CO2 compared with the control digesters at mesophilic and thermophilic temperature conditions. In a direct comparison at 1.83 g biochar (g VSadded)-1, the fine walnut shell biochar amended digesters (85.7% CH4 content and 61% CO2 removal) outperformed the coarse walnut shell biochar amended digesters (78.9% CH4 content and 51% CO2 removal). Biochar addition also increased alkalinity as CaCO3 from 2800 mg L-1 in the control digesters to 4800–6800 mg L-1, providing process stability for food waste anaerobic digestion.


2019 ◽  
pp. 195-205
Author(s):  
Priscilla Ogunlude ◽  
Ofasa Abunumah ◽  
Ifeyinwa Orakwe ◽  
Habiba Shehu ◽  
Firdaus Muhammad-Sukki ◽  
...  

As a result of rising economies and environmental constraints, the demand for clean and renewable sources of energy is fast increasing. Biogas is a renewable form of energy that fits all expectations in terms of delivery, cost, and greenhouse emissions reduction. Biogas utilization is advantageous because it is a means of creating wealth from daily human, agricultural, household and municipal waste that could otherwise be polluting the environment as waste is deposited on a daily basis which are potential biogas sources; it is not dependent on weather conditions as other renewable forms (solar and wind). Biogas can also be compressed, stored and transported, and therefore easily responds to changes in demand. This paper entails the use of nano-structured membranes to upgrade biogas (which contains primarily methane and carbon dioxide). The benefits of membranes include their compact structure and ease of usage with low maintenance, their low running costs and minimal loss of the upgraded gas. 15nm, 200nm and 6000nm membranes were used to ascertain the flux of the model biogas mixture passing through it under various operating conditions. In each case, the exit flowrate of methane was higher than that of carbon dioxide and this is attributed to the pore sizes of the membrane and its ability to filter the heavier gases. The results show that the molecular weight of the gases also play a role in their permeation rate as it follows the Knudsen regime.


2016 ◽  
Vol 61 (2) ◽  
pp. 285-292
Author(s):  
Bronisław Buczek

Abstract Methane recovery from gaseous mixtures has both economical and ecological aspect. Methane from different waste gases like mine gases, nitrogenated natural gases and biogases can be treated as local source for production electric and heat energy. Also occurs the problem of atmosphere pollution with methane that shows over 20 times more harmful environmental effect in comparison to carbon dioxide. One of the ways utilisation such gases is enrichment of methane in the PSA technique, which requires appropriate adsorbents. Active carbons and carbon molecular sieve produced by industry and obtained in laboratory scale were examined as adsorbent for methane recuperation. Porous structure of adsorbents was investigated using densimetry measurements and adsorption of argon at 77.5K. On the basis of adsorption data, the Dubinin-Radushkevich equation parameters, micropore volume (Wo) and characteristics of energy adsorption (Eo) as well as area micropores (Smi) and BET area (SBET) were determined. The usability of adsorbents in enrichment of the methane was evaluated in the test, which simulate the basic stages of PSA process: a) adsorbent degassing, b) pressure raise in column by feed gas, c) cocurrent desorption with analysis of out flowing gas. The composition of gas phase was accepted as the criterion of the suitability of adsorbent for methane separation from gaseous mixtures. The relationship between methane recovery from gas mixture and texture parameters of adsorbents was found.


2014 ◽  
Vol 40 (6) ◽  
pp. 492-498
Author(s):  
Shuji Himeno ◽  
Shintaro Suganoh ◽  
Tomohiro Takemi

Energy ◽  
2018 ◽  
Vol 157 ◽  
pp. 744-751 ◽  
Author(s):  
Huijuan Gong ◽  
Zezhi Chen ◽  
Huiqiang Yu ◽  
Weili Wu ◽  
Weixing Wang ◽  
...  

Author(s):  
Jorge Alberto Aponte ◽  
Gerardo Gordillo

Various alternative fuel technologies have been proposed as a solution to the negative environment impact caused by greenhouse emissions from fossil fuel combustion processes. One of those alternatives technologies is the inclusion of biomass (fuel crops and agricultural and municipal wastes) as feedstock to produce gaseous and liquid fuels via thermal gasification processes. Biomass thermal gasification is a clean technology, which does not increase the atmosphere carbon concentration since biomass is a neutral carbon energetic source. Wild cane is an invasive grass with a remarkable ability to establish and spread quickly. Thus, it has the potential to yield high biomass for the production of energy. Moreover, wild cane is considered as one of the species that most produces energy per hectare crop. Although wild cane occurs as a weed in most of the Colombian geography, it does not have an extensive potential use. However, wild cane can be included as feedstock for the production of bio-fuels via partial oxidation or thermal degradation (pyrolysis). Fuels produced through this technology can be used for heat o power generation in order to decrease the dependence of farms on fossil fuels. The current paper presents results on the wild cane potential to produce gaseous fuels through thermal gasification using air-steam mixtures for partial oxidation. Also, wild cane thermochemical properties are presented. The CEA (chemical equilibrium with applications) program from NASA was used to estimate the production of gaseous fuels as a function of the operating conditions, which include equivalence ratio (Φ) and steam to fuel ratio (S:F). Based on gas composition, the energy density of the gaseous fuels was estimated. Furthermore, the energy conversion was also calculated in order to estimate the efficiency of the gasification process. Wild cane thermochemical properties were obtained using ultimate, proximate, and thermogravimetric analyses (TGA). Thermogravimetric analyses were carried out using N2 as carrier gas and under different heating rates (β: 10, 20, and 35 °C/min). Based on TGA data and using the isoconversional method (i.e., free-model), the activation energy (E) was estimated. In general, the results show that the increase in operating conditions (equivalence ratio (Φ) and steam to fuel ratio (S:F)) results in gaseous mixtures rich in H2 and with a low CO content. On the other hand, the CH4 production is only possible at Φ > 4 and increases with increased Φ. The average activation energy was ∼ 162 KJ/Kmol.


Sign in / Sign up

Export Citation Format

Share Document