Oldoinyo Lengai Volcanic Ash for Removal of Hydrogen Sulfide and Ammonia from Biogas

Abstract

Oldoinyo Lengai mountain located in Northern Tanzania is the only active natrocarbonatite volcano with unusually alkali-rich natrocarbonatites which are not found elsewhere in the world. Volcanic ash formed earlier during eruptions was collected from different sites along the mountain, and its potency to adsorb hydrogen sulfide (H 2 S) and ammonia (NH 3) from biogas was investigated. The samples were calcinated at different temperatures (550˚C-850˚C) and were characterized by X-ray florescent, scanning electron microscopy and X-ray diffraction techniques. The on-site adsorption experiments were conducted at the biogas digester at ambient conditions. The calcinated ash was packed into the reactor bed, biogas allowed to pass through the adsorbent, and the inlet and outlet concentrations of H 2 S and NH 3 were measured. The height of the site where the adsorbent was taken from, calcination temperature, biogas flowrate and mass of the adsorbent were variable parameters and found to influence greatly on the efficiency of H 2 S and NH 3 removal. The efficiency is increased with calcination temperature raise and mass of adsorbent and decreased with flowrate increase. The samples collected from the top site of the mountain and calcinated at 850˚C exhibited the best sorption performance.

Performance of Sweet Potato’s Leaf-Derived Activated Carbon for Hydrogen Sulphide Removal from Biogas

“…These results could be influenced by a higher amount of activated carbon that enhances larger contact surface area for H 2 S to be held into the pores of adsorbent hence higher RE. Similar outcomes may be observed in the studies [4,19] where the sorption performance of adsorbents increased with an increase of sorbent mass.…”

“…where C 0 and C are the initial and final concentrations of H 2 S, respectively. Sorption capacity (SC) was calculated using equation (2) [19]:…”

“…Capacity. Sorption capacity in a gram of sulphur per 100 g of sorbent for both carbonized and activated samples was calculated using equation (2) as portrayed in [19]. Breakthrough time for both carbonized and activated samples is shown in Table 5 together with textural parameters.…”

“…However, each adsorbent has its drawbacks; for instance, the use of water hyacinth has the potential of promoting its cultivation, which may lead to invading and dominating more water bodies. Oldoinyo Lengai volcanic ashes have been reported to have a hydrogen sulphide removal capacity of up to 1.00 g of sulphur/100 g of sorbent [19]; however, the exploitation of Oldoinyo Lengai volcanic ashes will lead to the destruction of the Oldoinyo Lengai conservation area. Zeolite is another efficient hydrogen removing material [20].…”

Removal of Hydrogen Sulfide from Biogas Using a Red Rock

“…The biogas composition differs according to the material used in the whole process of production. The main components are carbon dioxide (CO 2 ) and methane (CH 4 ), although it likewise encompasses some amounts of contaminants like H 2 S, NH 3 , volatile halogenated organics, and siloxanes [2].…”