Controlling Properties of Sulfur
Particles Formed in Biological
Aug 2016 - 2020
Dr. Renata van der Weijden
Dr. ir. Jan Klok
Prof. dr. ir. Cees Buisman
Biogas, natural gas and other fuel gasses may
contain corrosive components such as H2S which
has detrimental effects on the environment when
combusted. Consequently, it is required to remove
H2S from gas before it can be used. Hence, a
biotechnological desulfurization process was
developed at Wageningen University, which uses
natron-alkaline sulfide oxidizing bacteria (Fig. 1).
This process is an alternative to chemo-physical
processes which are commonly applied in industry.
Advantages of the biological process are (i) no
consumption of chelating chemicals, (ii) operation
at atmospheric pressure and ambient temperature,
(iii) high removal efficiency with a sulfide-free waste
stream and (iv) beneficial use of the biologically
H2S (l) + CO3 ⇄ HS + HCO3
HS +½O2 → ⅛S8 +OH
In addition to elemental sulfur, other sulfur
compounds are formed as by-product, like sulfuric
HS- + 2O2 SO42- + H+
While formation of elemental sulfur is protonneutral, the formation of other S-products requires
compensation of produced protons by addition of
Although the optimization of sulfur formation has
been studied extensively, specific properties of the
formed sulfur, like filterability and settleability,
remain subject of interest. Knowledge on how to
control particle properties will lead to higher
recovery of the biosulfur.
Figure 2 Novel reactor line-up
Figure 1 Thiobacillus excreting sulfur [Janssen, A. et al. (1996)]
In the desulfurization process, H2S is absorbed into
a mild alkaline liquid and dissociated (Eq.1).
Subsequently, the dissolved HS- is oxidized to
elemental sulfur in a bioreactor (Eq.2).
The optimization of sulfur formation and recovery is
aimed for by operating a novel reactor line-up
including an anoxic reactor B (Fig 2), which is
compared to the classic Thiopaq line-up in terms of
(1) sulfur particle properties, (2) microbial
composition and (3) long term stability. Also the
relation between these parameters is assessed.
Wageningen University, Biotechnology (2016)
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