Lignin Syngas Bioconversion by Butyribacterium methylotrophicum: Advancing towards an Integrated Biorefinery

Hybrid bio-thermochemical based technologies have the potential to ensure greater feedstock flexibility for the production of bioenergy and bioproducts. This study focused on the bioconversion of syngas produced from low grade technical lignin to C2-/C4-carboxylic acids by Butyribacterium methylotrophicum. The effects of pH, medium supplementation and the use of crude syngas were analyzed. At pH 6.0, B. methylotrophicum consumed CO, CO2 and H2 simultaneously up to 87 mol% of carbon fixation, and the supplementation of the medium with acetate increased the production of butyrate by 6.3 times. In long-term bioreactor experiments, B. methylotrophicum produced 38.3 and 51.1 mM acetic acid and 0.7 and 2.0 mM butyric acid from synthetic and lignin syngas, respectively. Carbon fixation reached 83 and 88 mol%, respectively. The lignin syngas conversion rate decreased from 13.3 to 0.9 NmL/h throughout the assay. The appearance of a grayish pellet and cell aggregates after approximately 220 h was indicative of tar deposition. Nevertheless, the stressed cells remained metabolically active and maintained acetate and butyrate production from lignin syngas. The challenge that impurities represent in the bioconversion of crude syngas has a direct impact on syngas cleaning requirements and operation costs, supporting the pursuit for more robust and versatile acetogens.

Catalytic Tar Conversion in Two Different Hot Syngas Cleaning Systems

Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of the most promising approaches is the catalytic decomposition of the tar species combined with hot syngas cleaning. The catalyst must be able to convert tar components in the synthesis gas at temperatures of around 700 °C downstream of the gasifier without preheating. A Ni-based doped catalyst with high activity in tar conversion was developed and characterized in detail. An appropriate composition of transition metals was applied to minimize catalyst coking. Precious metals (Pt, Pd, Rh, or a combination of two of them) were added to the catalyst in small quantities. Depending on the hot gas cleaning system used, both transition metals and precious metals were co-impregnated on pellets or on a ceramic filter material. In the case of a pelletized-type catalyst, the hot gas cleaning system revealed a conversion above 80% for 70 and 110 h. The catalyst composed of Ni, Fe, and Cr oxides, promoted with Pt and impregnated on a ceramic fiber filter composed of Al2O3(44%)/SiO2(56%), was the most active catalyst for a compact cleaning system. This catalyst was catalytically active with a naphthalene conversion of around 93% over 95 h without catalyst deactivation.

PROSES PEMBERSIHAN SYNGAS HASIL GASIFIKASI TEMPURUNG KEMIRI MENGGUNAKAN SIKLON

This study aims to examine the process of cleaning for synthesis gas (syngas) resulted from candlenut shell gasification by using a cyclone. Research was started by design or manufacture a cyclone as a tool that can condense the tar carried in the syngas produced from the gasification process. This tool was tested with by trial and error such that got a tool that can function optimally to condense tar. The syngas cleaning experiment using the cyclone was conducted by four treatments, namely S1 (1 cyclone), S2 (2 cyclones), S3 (3 cyclones), and S4 (4 cyclones). All treatments were repeated 4 (four) times, so there were 16 experimental units. The parameter measured is the amount of tar that was condensed on the cyclone. Result showed that the syngas cleaning process using a cyclone worked well, and the best treatment was S3 (3 cyclones) with an average amount of condensed tar of 141.7 ml/kg of shell. The use of cyclones can condense tar and other particulates carried in the syngas. The cleaned syngas can be applied as fuel in an internal combustion engine as a substitute for diesel and gasoline fuels. Keywords: gasification, syngas, cleaning, cyclone

Analytical studies on deposition and entrainment present in the Venturi nozzle two-phase flow

The syngas purification is a basic problem in the gas production process through the biomass gasification. This issue is important due to the use of the Venturi scrubbers in the syngas cleaning process. As it is commonly known, syngas is an alternative for the coal and using syngas instead of the coal leads to ‘clean energy’ generation. The paper concerns the analytical research studies on two-phase fluid flow pattern in Venturi’s throat. The uniform coverage of Venturi’s cross-section with small droplets plays a significant role in the dust particles collection and chemicals removal as Venturi’s cleaning efficiency mostly depends on this operation parameter. Therefore, the analysis of the two-phase fluid flow with respect to a droplet deposition and entrainment was carried out. Based on these research studies, it is possible to determine the variation of the liquid superficial velocity in the core of the flow and within the liquid wall film, the length at which the droplet entrainment starts to occur, the liquid fraction variation with Venturi’s throat length and diameter. The obtained analytical model, which is introduced in the paper, was validated with the use of the experimental data available in the literature.

Integration of Gasification and Solid Oxide Fuel Cells (SOFCs) for Combined Heat and Power (CHP)

This paper reviews the most recent information about the main operations to produce energy from carbonaceous materials, namely biomass and wastes through the integration of gasification, syngas cleaning and solid oxide fuel cells (SOFCs), which have shown to be a good option for combined heat and power (CHP) production, due to high efficiency and low environmental impact. However, some challenges still need to be overcome, mainly when mixed feedstocks with high contents of hazardous contaminants are used, thus syngas cleaning and conditioning is of major importance. Another drawback is SOFC operation, hence new materials especially for the anode has been proposed and tested. An overall process to produce CHP by gasification integration with SOFC is proposed.

Technologies for Tar Removal from Biomass-Derived Syngas

The concerns on the significant negative environmental impacts of conventional fuels such as coal, oil and natural gas have fostered the shift of energy consumption towards renewable and environment friendly sources like biomass derived energy. Many technologies have been developed to generate energy from biomass; among them gasification is considered one of the most promising technologies, since and the generated syngas has many practical applications, such as a world-wide sustainable energy production or synthesis of fuels and chemicals. Unavoidable produced impurities during gasification can create severe problems in downstream applications; therefore, the cleaning of the produced syngas is essential. A major challenge in commercialization of syngas technology and its valorization is tar removal method. This review organizes the knowledge related to tar generated from biomass-derived syngas, and discusses the recent progress on clean technologies for tar elimination. The advantages and disadvantages of different tar removal methods are critically discussed. Primary treatment is able to optimise the gas composition for the secondary cleaning step but is not sufficient for further syngas applications. Among the secondary treatments, the catalytic cracking is most valued in terms of energy and yield efficiencies for syngas cleaning. This review discusses current technical barriers and future opportunities of technical development.

Sulfur Recovery from Syngas in Pulp Mills with Integrated Black Liquor Gasification

Research Highlights: As to fill the current knowledge gap and to deliver important findings to the scientific community, efficient sulfur recovery from black liquor gasifier syngas, comprising both gas cleaning and returning sulfur to the pulping process, was modeled and assessed from a techno-economic viewpoint. This manuscript proves that the associated investment and operational costs cannot be neglected and that they impact the black liquor gasification feasibility significantly. To prove its gasification as a sustainable and more efficient processing route over its combustion in recovery boilers, a substantial process efficiency improvement and operating costs reduction must be targeted in future research. Background and Objectives: Sulfur compounds found in black liquor partly turn into hydrogen sulfide during gasification and exit the gasifier in the syngas. Their efficient recovery in their sulfidic form to the pulping process is of utmost importance. Current studies focus on black liquor gasifier syngas desulfurization only. Materials and Methods: A mathematical model of two H2S absorption units from a 66.7 tDS/h (1600 tons dry solids per day) black liquor gasification process to 20 ppm H2S content in cleaned syngas using either white liquor plus NaOH or N-methyldiethanolamine (MDEA) was created using the Aspen Plus simulation software. Results: The results show that CO2 co-absorption significantly increases the lime kiln load: +20% in the MDEA alternative and +100% in the other one. The MDEA alternative requires almost the same investment costs but by around USD 9.7 million (>50%) lower annual operating costs compared to the other one. Economic evaluation was based on the assumed discount rate of 5% and on the expected plant operation time of 25 years. The estimated total investment cost of the whole plant is around USD 170 million for both alternatives. The whole plant including this alternative exhibits a positive net present value (over USD 19 million), an internal rate of return of 5% and a profitability index of 1.12, whereas that with the other alternative is economically infeasible. Conclusions: The MDEA-based syngas cleaning technology represents a more efficient and economically feasible option of sulfur recovery. A major drawback of both modeled syngas cleaning technologies is that their estimated annual operating costs significantly reduce the expected profit margin of gasification over the traditional black liquor combustion in a recovery boiler. Syngas cleaning and sulfur recovery have to be further optimized to reach a significant cut down in operational costs to improve the economic feasibility of black liquor gasification.