Process Simulations of High-Purity and Renewable Clean H₂ Production by Sorption Enhanced Steam Reforming of Biogas

Renewable clean H2 has a very promising potential for the decarbonization of energy systems. Sorption enhanced steam reforming (SESR) is a novel process that combines the steam reforming reaction and the simultaneous CO2 removal by a solid sorbent, such as CaO, which significantly enhances hydrogen generation, enabling high-purity H2 production. The CO2 sorption reaction (carbonation) is exothermic, but the sorbent regeneration by calcination is highly endothermic, which requires extra energy. Biogas is one of the available carbon-neutral renewable H2 production sources. It can be especially relevant for the energy integration of the SESR process since, due to the exothermic sorption reaction, the CO2 contained in the biogas provides extra heat to the system, which can help to balance the energy requirements of the process. This work studies different process configurations for the energy integration of the SESR process of biogas for high-purity renewable H2 production: (1) SESR with sorbent regeneration using a portion of the produced H2 (SESR+REG_H2), (2) SESR with sorbent regeneration using biogas (SESR+REG_BG), and (3) SESR with sorbent regeneration using biogas and adding a pressure swing adsorption (PSA) unit for hydrogen purification (SESR+REG_BG+PSA). When using biogas as fuel (Cases 2 and 3), these configurations were studied using air and oxy-fuel combustion atmospheres in the sorbent regeneration step, resulting in five case studies. A thermodynamic approach for process modeling can provide the optimal process operating conditions and configurations that maximize the energy efficiency of the process, which are the basis for subsequent optimization of the process at the practical level needed to scale up this technology. For this purpose, process simulations were performed using a steady-state plant model developed in Aspen Plus, incorporating a complex heat exchanger network (HEN) to optimize heat integration. A comprehensive parametric study assessed the effects of biogas composition, temperature, pressure, and steam to methane (S/CH4) ratio on the process performance represented by the selected key performance indicators, i.e., H2 purity, H2 yield, CH4 conversion, cold gas efficiency (CGE), net efficiency (NE), fuel consumption for the sorbent regeneration step, and CO2 capture efficiency. H2 with a purity of 98.5 vol % and a CGE of 75.7% with zero carbon emissions can be achieved. When adding a PSA unit, nearly 100% H2 purity and CO2 capture efficiency were achieved with a CGE of 77.3%. The use of oxy-fuel combustion during regeneration lowered the net efficiency of the process by 2.3% points (since it requires an air separation unit) but allowed the process to achieve negative carbon emissions

MOESM2 of An enhanced vector-free allele exchange (VFAE) mutagenesis protocol for genome editing in a wide range of bacterial species

Additional file 2. Schematic representation and comparison of the original and modified VFAE procedures

Bacterial strains and plasmids used in this study.

a<p>phenol⁺, growth on phenol; phenol⁻, no growth on phenol; Ap^R, ampicillin resistance; Tc^R, tetracycline resistance; Km^R, kanamycin resistance.</p

Primers used in this study.

a<p>Restriction sites for BamHI (5′-GGATCC-3′), HindIII (5′-AAGCTT-3′), EcoRI (5′-GAATTC-3′), and SalI (5′-GTCGAC-3′) are shown in bold and italic.</p

Analysis of the promoter region and transcriptional start site for mphK.

<p>(A) Intergenic region between <i>mphR</i> and <i>mphK</i>. The first nucleotide in the transcript is shown in bold. Arrows and dashed arrows indicate incomplete inverted repeats (named IR1, IR2, and IR3) and the translational start codons for <i>mphR</i> and <i>mphK</i>, respectively. Double-underlines mean the putative σ⁵⁴-dependent −12/−24 promoter consensus sequence and the σ⁷⁰-dependent −10/−35 promoter consensus sequences. An arrowhead with +1 indicates the transcriptional start site for <i>mphK</i>. A grey-shaded box indicates the putative ribosome-binding site for the <i>mphK</i> transcription. (B) Mapping of the transcriptional start site for <i>mphK</i> by primer extension. A sequence ladder was generated with the same primer (lanes T, A, C, and G).</p

Unrooted Deinococcales neighbor-joining phylogenetic tree deduced from the nucleotide acid sequences of the orthologous proteins that occur in all 14 sequenced strains from the phylum Deinococcus-Thermus.

<p><i>D. gobiensis</i> and <i>D. radiodurans</i> are most closely related. Numbers indicate bootstrap values below 100.</p

General features of the <i>D. gobiensis</i> genome.

<p>General features of the <i>D. gobiensis</i> genome.</p

<i>D. gobiensis</i> I-0 genome structure.

<p>The seven replicons were opened at sequence position 1 and concatenated. Circle 1, red, chromosome (3.1 Mb); violet, plasmid 1 (P1, 433 kb); indigo, P2 (425 kb); blue, P3 (232 kb); light blue, P4 (72 kb); dark green, P5 (55 kb); light green, P6 (53 kb). Circles 2 and 3, predicted protein coding sequences (CDSs) clockwise and anticlockwise, respectively. Coloring is according to COG. Circle 4, Fold change in the immediate global transcriptional response to UV irradiation for each gene: green, upgulated; red, down-regulated; yellow, not changed significantly. Circle 5, red, rRNA; purple, tRNA; green, ncRNAs (noncoding). Circle 6, blue, genes with homologues in other <i>Deinococcus</i> genomes; red, genes found only in <i>D. gobiensis</i> I-0; other colors, genes with closest homologues in other phyla. Circle 7, deviation from the average 69.15% total genomic GC content: red, higher; blue, lower. Circle 8, previously reported genes that are involved in DNA repair and stress-responses. Circle 9, location of the 23 genomic islands. Circle 10, Mb scale.</p