Laboratory-Scale Investigation of Biogas Treatment by Removal of Hydrogen Sulfide and Carbon Dioxide

Abstract

The use of organic residues and waste for production of biogas as an energy source is a viable option for waste management and reduction of greenhouse gas emissions. However, before any eventual utilization of biogas, hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) must be removed since those contaminants are highly undesirable in combustion systems. This work deals with the construction and examination of a laboratoryscale, low-cost test stand for quick evaluation of the existing and new methods for H 2 S and CO 2 removal from biogas. The test stand consists of two sections: one based on absorption in liquid phase (barbotage process) and the other adsorption in a bed of solid reagent. Seven different reagents of various concentrations were used in the experiment: sodium hydroxide (NaOH), ethylene glycol (EG), ethanoloamine (EA), diethanoloamine (DEA), and distilled water (H 2 O) in the barbotage section of the test stand, and bog iron ore (BIO) and activated carbon (AC) in the adsorption column. In the absorption tests, treating biogas with 1M NaOH solution and 100% EA resulted in complete removal of H 2 S and CO 2 . For 100% DEA, high H 2 S and moderate CO 2 absorption efficiency were achieved. EG and H 2 O allowed the removal of H 2 S only to a very limited extent. Both reagents used in the tests with adsorption in a bed, BIO and AC, were able to eliminate H 2 S from biogas, but practically did not change the concentration of CO 2 .

A Review of Biogas Utilisation, Purification and Upgrading Technologies

“…Amine solution is widely used to absorbed CO 2 and there is little or no methane losses (0.1-1.2%), with methane recovery greater than 99% because the chemical solvent reacted selectively with CO 2 . Although some reports [7,8,16,20] reported methane losses up to 4% due to CH 4 dissolution in alkanolamine. It also operated like water scrubbing countercurrent flow configuration, and H 2 S should be treated prior to chemical scrubbing because of amine poisoning (Fig.…”

“…This is the same way as water/glycol scrubbing for biogas-liquid mass transfer principles, but chemical reaction takes place between the solvent and the absorbed substances. It relies on CO 2 reactive absorbents such as alkanol amines (mono ethanol amine (MEA)) or di-methyl ethanol amine (DMEA), and alkali aqueous solutions such as KOH, K 2 CO 3 , NaOH, Fe(OH) 3 , FeCl 2 [20]. The unit consists of a packed bed (random or structural) coupled with desorption unit equipped with reboiler to simplify process configuration, with no risk of biomass growth as result of high pH of the amine solutions [4].…”

Removing Hydrogen Sulfide Contamination in Biogas Produced from Animal Wastes

“…These results are in agreement with previous studies (Chung et al, 2006; Ho et al, 2013; Horikawa et al, 2004; Lin et al, 2013), which removed H 2 S by a combined chemical–biological solution, showing that H 2 S removal efficiency increased with increasing retention time. Others have found that H 2 S removal efficiency increased with increasing retention time through increasing bed height of bog iron ore (30, 53, and 80 mm height) at the same gas flow rate (Lasocki et al, 2015) or with decreasing biogas flow rates (from 60–80% at 50 L min −1 to 25–60% at 140 L min −1 ) (Lien et al, 2014). Pagella et al (1996) found that the H 2 S removal efficiency can be enhanced through either reducing gas flow rates or increasing the soil volume.…”

“…These results are in agreement with the studies of Chung et al (2006), who concluded that more than 99.5% of H 2 S is removed in the first 10 h of feeding by chemical adsorption. Lasocki et al (2015) indicated that using bog iron ore and activated carbon as H 2 S adsorption beds in filters also reduced almost 100% of H 2 S in a 30-min exposure period. Rogers and Whitehead (1998) showed that 2500 mg L −1 H 2 S concentration in raw gas was removed to below 1 mg L −1 by three different filtration stages, including an iron chelate solution, a dry iron oxide box, and an activated carbon filter.…”

Removal of hydrogen sulphide content from biogas by atomizing of alkali solution

“…Additionally small amount of ammonia (NH 3 ), hydrogen sulfide (H 2 S), nitrogen (N 2 ), oxygen (O 2 ), carbon monoxide (CO), water (H 2 O), siloxanes and halogenated volatile organic compounds (VOCs) are present as impurities in biogas [2; 5-8]. Table 1 shows the chemical composition of raw biogas from different sources [7].…”