Regeneration Reactor Research Articles

The Effect of Voidage on the CO2 Sorption Capacity of K-Based Sorbent in a Dual Circulating Fluidized Bed Process

The performance of the CO2 capture of a potassium-based dry sorbent was investigated in a dual circulating fluidized bed process. The dual circulating fluidized bed process consisted of a carbonation reactor and a regeneration reactor. It was operated in the continuous solid circulation mode between a fast fluidized-bed carbonator of 6 m in height and a bubbling fluidized-bed regenerator. As the solid circulation rate increased from 7 to 36 kg/m2/s, the CO2 removal of the potassium sorbent, sorbKX40, increased from 25 to 55% and the mean voidage was maintained from 0.94 to 0.99 representing the dilute phase in the fluidization regime. The continuous solid circulation behavior in a dual fluidized bed process was well expressed by a single closed loop in a pressure balance curve that indirectly explained the direction of the sorbent flow and the mean bulk densities of the gas–solid mixture. The information on hydrodynamics and sorption capacity will be used for the conceptual and scale-up design of the system.

Inactive enzymatic mutant proteins (phosphoglycerate mutase and enolase) as sugar binders for ribulose-1,5-bisphosphate regeneration reactors

BackgroundCarbon dioxide fixation bioprocess in reactors necessitates recycling of D-ribulose1,5-bisphosphate (RuBP) for continuous operation. A radically new close loop of RuBP regenerating reactor design has been proposed that will harbor enzyme-complexes instead of purified enzymes. These reactors will need binders enabling selective capture and release of sugar and intermediate metabolites enabling specific conversions during regeneration. In the current manuscript we describe properties of proteins that will act as potential binders in RuBP regeneration reactors.ResultsWe demonstrate specific binding of 3-phosphoglycerate (3PGA) and 3-phosphoglyceraldehyde (3PGAL) from sugar mixtures by inactive mutant of yeast enzymes phosphoglycerate mutase and enolase. The reversibility in binding with respect to pH and EDTA has also been shown. No chemical conversion of incubated sugars or sugar intermediate metabolites were found by the inactive enzymatic proteins. The dissociation constants for sugar metabolites are in the micromolar range, both proteins showed lower dissociation constant (Kd) for 3-phosphoglycerate (655–796 μM) compared to 3-phosphoglyceraldehyde (822–966 μM) indicating higher affinity for 3PGA. The proteins did not show binding to glucose, sucrose or fructose within the sensitivity limits of detection. Phosphoglycerate mutase showed slightly lower stability on repeated use than enolase mutants.ConclusionsThe sugar and their intermediate metabolite binders may have a useful role in RuBP regeneration reactors. The reversibility of binding with respect to changes in physicochemical factors and stability when subjected to repeated changes in these conditions are expected to make the mutant proteins candidates for in-situ removal of sugar intermediate metabolites for forward driving of specific reactions in enzyme-complex reactors.

Integrated Tests for Removal of Nitric Oxide with Iron Thiochelate in Wet Flue Gas Desulfurization Systems

Wet flue gas desulfurization scrubbers can be retrofitted for combined removal of SO 2 and NO x from flue gas by adding a newly developed iron(II) thiochelate to limestone slurries. This additive enhances the solubility of NO in limestone slurries by binding NO to form iron nitrosyl thiochelates. The bound NO is then converted to an ammonium ion by iron metal, regenerating the active iron(II) catalyst for continued NO capture. The conditions of the chemical regeneration of iron(II) thiochelate have been studied. This chemical reduction method is efficient, simple, and cost-effective. Integrated tests of this new iron additive on a bench-scale system have been conducted. A turbulent contact absorber was employed to test simultaneous removal of NO and SO 2 with iron(II) thiochelate in a limestone slurry. The steady-state NO removal efficiency depends on the operating conditions of an absorber, the iron chelate concentration, the fraction of the flow diverted for regeneration, and the conditions used in the regeneration reactor. The bench-scale test results were used to develop a prediction of the performance of a full-scale spray absorber.

Catalysts Deactivation by Coking

Abstract Catalyst deactivation due to coke formation is an important technological and economic problem in petroleum refining and in the petrochemical industry. Remedies to catalyst deactivation are sought by a variety of strategies involving modification of catalyst surface composition such as the use of polymetallic catalysts and/or by manipulation of the reaction environment which often limits the yield due to thermodynamic constrains (i.e., high hydrogen pressures, etc.). In the limit, when the activity reaches unacceptable limits, regeneration by burning off carbon residues can usually be attained, Regeneration can take place in situ, as in fixed-bed reactors, or in an adjacent reactor to which the catalysts is transported to, such as in moving-bed reactors or in fluidized-bed reactors. In the first case intermittent operation is required, whereas in the second case the operation is continuous, but a second regeneration reactor is required. The choice of the proper process cycle is an economic optimi...