Biogas Plant Upgrade to CO2-Free Technology: A Techno-Economic Case Study

A techno-economic analysis was performed for a biogas plant with in-built algae production. Degradation in the fermenter occurs under mesophilic conditions, to produce 605 Nm³t⁻¹_TS of biogas and 343 Nm³t⁻¹_TS of methane after 50 days. The biogas was combusted in a combined heat-and-power unit to produce heat and electricity. Cultivation of Chlorella vulgaris was done in co-annular photo-bioreactors, with an annual productivity of 107.5 t. For cultivation, both autotrophic and mixotrophic growth were assumed. Detailed mass and energy balances were done. For both conditions of algae growth, the results are approximately the same after a 30-year payback period.     

Flexibility Potential of Photovoltaic Power Plant and Biogas Plant Hybrid Systems in the Distribution Grid

The potential of combining biogas and photovoltaic (PV) power plants in hybrid systems in the German distribution grid is analyzed. The focus of the present research is on balancing the intermittent power supply from PV power plants with the controllable power production of combined heat and power (CHP) units of biogas plants within a period of seconds. To achieve an increase of the total energy feed-in of biogas and PV power plants to the electricity grid, a biogas plant energy management system is described. System parameters, such as the variable feed-in of PV power plants or power ramps of the start-up process of controllable biogas plant CHP unit, are described and adapted to the global installed capacity of PV power plant and biogas plants in the German distribution grid.     

Biogenic Catalysis by Adding Compost when Using Wheat Straw in a Biorefinery Concept

The high content of lignocellulose limits the biodegradability of wheat straw for bioenergy production. To counteract this fact, a thermobiological pretreatment was applied to improve the utilization of lignocellulose biomasses for a biorefinery concept. The use of compost assured the growth of cellulose-degrading anaerobic microorganisms under thermophilic conditions. Results revealed a lignocellulose material degradation in all samples. Moreover, the combination of a thermobiological pretreatment under thermophilic conditions created a synergistic effect that accelerated the biomethanization of wheat straw due to the sugar compounds released during the biogenic catalysis.     

Monitoring and Mitigation of Methane Emissions from Pressure Relief Valves of a Biogas Plant

The two-year monitoring (732 days) of operational methane emissions from pressure relief valves of the gasholders from an agriculture biogas plant is presented. The monitoring aimed at the identification of major factors influencing the emissions and the effect of mitigation measures deduced from the results. The determined emission factors from the valves of both gastight covered digesters are 1.8 and 0.6 % CH₄ loss for the first and second year of investigation, respectively. The emission rates strongly depend on seasonal factors like (fast) changes in ambient air temperature as well as the capacity utilization of the combined heat and power and the operation of the gasholders. The implemented mitigation measures significantly reduced the measured methane emissions in the second year of the investigation.     

沼气发动机技术概述

论述了沼气性质及沼气収动机燃烧特点,简单介绍了国内外兲于沼气収动机的研究概况。同时,对沼气収动机的分类和特点迚行了总结与分析,幵针对沼气収动机特点,对提高沼气収动机热敁率的技术迚行了概述。最后,针对目前的収展形势,对沼气収动机今后的研究収展趋势迚行了总结和展望。     

Comparative Study on the Performance of Aboveground and Underground Fixed-Dome Biogas Digesters

A comparative analysis of aboveground and underground biogas digesters is described in relation to their performance and effect of temperature, pH, and hydraulic retention time. The digestion chamber of the two biogas systems under study was fabricated using high-density polyethylene (HDPE) plastic, while the inlet and outlet chamber were constructed with bricks. The performance of small-scale digesters, particularly of the fixed-dome type, should be improved. Cow dung served as substrate in the performance test. Biogas production from the two systems was measured by a customized gas temperature pressure measurement sensor. Evidently, the insulation provided to the underground digester helped to achieve a more stable internal temperature for the digester.     

Operation and Control of a Full-Scale Biogas Plant Treating Wastewater from the Cleaning of Car Tanks

A 1200-m³ full-scale biogas plant treating highly polluted wastewater (WW) from the cleaning of tank cars transporting food and fodder is working stably and efficiently despite the WW is constantly varying in strength and composition, is easily acidifying, and low in alkalinity. Na₂CO₃ has to be added to maintain the digester alkalinity and the digester pH at defined values due to softened water used for car tank cleaning. Monitoring volatile organic acid concentration and controlling the alkalinity in the digester are essential for maintaining the digestion process stability. Biogas production is adapted to the demand by a modulated feeding regime. The drastic modulation of feeding is possible due to the moderate organic loading of the plant along with the high average hydraulic retention time.     

Monitoring of Ammonia in Biogas

Ammonia content is an important factor, which has to be considered when optimizing the processes in a biogas plant. A measurement system for a continuous monitoring of ammonia has been constructed, which can be placed in the gas room above the digester. The monitoring is based on the measurement of the electrical impedance. In this system, a condensate is generated on the surface of an interdigital electrode so that the whole stray field is covered by the condensate. For determining the ammonia content, impedance spectroscopy of these drops is performed. The ammonia of the biogas causes a decrease in the impedance in comparison to a pure aqueous condensate. A first evaluation of this measurement system using artificial slurries has been performed.     

沼气低温净化工艺的模拟研究

依据气液相平衡理论,运用Aspen Plus软件,选用合适的单元操作模块,采用PENG-ROB物性计算方法,通过对沼气泡点、露点图的分析选择合适的模拟条件;在Aspen Plus软件上对沼气低温净化工艺进行模拟,并根据模拟数据分析压力、温度对低温净化工艺的效果的影响。     

沼气发动机专用油的研制

通过研究沼气发动机工作情况,综合分析沼气燃料特殊性质,对添加剂进行筛选、配比。研制油具有优异的抗高温氧化性、抗硝化性、抗腐蚀性、防锈性、粘温特性等,灰分适当,可延长换油周期,降低使用成本,能满足不同类型沼气发动机的使用要求。     

分布式能源联供技术在油田的应用

提出了适用于油田的天然气综合利用方案,开发了热电联供技术,介绍了热电联供装置的组成、选型原则以及在油田的实际应用方案和效果,提高了能源综合利用效率,降低了生产运营成本,适应油田电力和热能的需求,实现了"低碳环保、能效倍增"的生产目标。     

Environmental Effects on the Properties of Biopolymer Service-ware Products

The current trend towards sustainability has promoted a new interest in biodegradable plastics. Although there have been many studies on the behavior of biodegradable plastics, the changes in properties that may occur during use have not been fully documented. The mechanical properties of seven commercial service-ware items produced with biodegradable plastics were analyzed in this investigation. The effects of UV exposure, humidity, and accelerated aging on the mechanical properties were studied. In general, samples from polylactic acid and wheat straw had properties comparable to traditional synthetic plastics used in this application. However, the strength of other polymers such as bagasse, fiber pulp and potato starch was less than that of comparable synthetic plastics. The mechanical properties of the biopolymers generally deteriorated significantly upon exposure to UV radiation and humidity, with polylactic acid, wheatstraw, potato starch, and the bamboo bulrush wheatstraw blend being affected the most. Accelerated aging data indicate that after 6 months under ambient conditions, the potato starch, wheatstraw, and bamboo bulrush wheatstraw blend have a significant reduction in strength and modulus. In general, the thermal analysis behavior of most of the plastics was similar indicating a major weight loss of about 69–97% over a temperature range of 250–400?C. Additional improvements may be necessary to increase the environmental resistance of these biopolymers so that they can be effective replacements for traditional plastics.     

Molten Salt Storage for Power Generation

Storage of electrical energy is a key technology for a future climate-neutral energy supply with volatile photovoltaic and wind generation. Besides the well-known technologies of pumped hydro, power-to-gas-to-power and batteries, the contribution of thermal energy storage is rather unknown. At the end of 2019 the worldwide power generation capacity from molten salt storage in concentrating solar power (CSP) plants was 21 GWh_el. This article gives an overview of molten salt storage in CSP and new potential fields for decarbonization such as industrial processes, conventional power plants and electrical energy storage.     

Slurry Utilization and Impact of Mixing Ratio in Biogas Production

The anaerobic conversion of waste to biogas in a biogas digester is influenced by a number of factors including mixing ratios, type of substrate, temperature, organic loading rate, pH, and carbon/nitrogen ratio. The appropriate mixing ratio of water and animal waste leads to effective biogas yield. Different mixing ratios proposed in literature for various animal waste for improving biogas yield are reviewed. Characterization and application of animal slurry, the choice of animal slurry as suitable feedstock for biogas production, the storage of animal slurry, the agitation process of slurry as well as mixing ratios of animal slurry are evaluated.     

Integration potential,resource efficiency and cost of forest-fuel-based biorefineries

A multidisciplinary study of the implementation potential of a biorefinery, using forestry residues as feedstock, is performed by assessing techno-economic factors, system integration and feedstock supply. The process is based on biochemical conversion of logging residues to produce ethanol, biogas, pellets, heat and electricity. Nine models were designed in Aspen Plus based on the available feedstock and the required co-products. Focus was on the product ratio of pellets and heat. The net present value of the plants was calculated and thermal integration with district-heating systems in areas with regional feedstock availability was investigated. Also co-location with pulp and paper mills in Sweden was investigated to replace fossil fuels with pellets. Seven of the nine models showed a positive net present value assuming an 11% discount rate and 30% corporate tax. Five counties in Sweden were identified as potential feedstock suppliers to a biorefinery processing 200 kt dry feedstock/y.     

基于Aspen Hysys的沼气中N_2对净化工艺的影响

沼气净化技术主要包括脱硫、脱水、脱碳等工艺,而很少涉及N_2对净化工艺的影响。系统地研究了沼气中氮含量对其净化效果的影响。利用化工过程模拟软件,对沼气虚拟临界性质、热值、定压比热容等进行了物性分析,以及对压缩机功耗进行了模拟计算。研究发现,随着N_2含量从0%增至9%时,沼气的临界温度下降12.53℃,热值下降9.03%;N_2含量的增加,也使得在脱碳工序中,对沼气进行冷却降温时所需的换热量增加,且冷却效率明显降低;在相同排气压强工况下,随着N_2含量的增加,压缩机功耗增加明显。     

固体氧化物燃料电池系统及其应用

对固体氧化物燃料电池系统和单体电池及其工作原理、材料组成等作了简要介绍,并介绍了固体氧化物燃料电池在电厂混合发电方面与燃气轮机组成的联合系统技术以及以天然气为燃料家庭热电联产方面的应用。并指出固体氧化物燃料电池由于其高效、环保清洁将是未来能源利用的主要方式。     

Determining Conditions of Intermittently Fed Digesters from Biogas Production Rate Data

As the contribution from renewable energy to the power grid increases, biogas plants could profit from on-demand production. Flexible feeding can supplement gas storage for further benefits. Changing to flexible feeding introduces transient events to the feeding, and by monitoring the system response to the feeding transients it is possible to gain information about the system stability. Testing was performed at the laboratory and pilot scale to investigate the response characteristics. A statistical analysis was carried out to assess the response to feeding events and make an estimate of the system stability. This analysis was then used as the input to a proportional integral derivative controller for controlling the feeding rate for an anaerobic digestion model No. 1 simulation.     

Biogas reforming over La-NiMgAl catalysts derived from hydrotalcite-like structure: Influence of calcination temperature

Hydrotalcite-like compound with general formula [M(II)_1 − xM(III)_x(OH)₂]^x+(Aⁿ⁻_x/n) ^· mH₂O, where Aⁿ⁻ is the compensation anion, has been used as precursor of active catalysts for biogas reforming. This precursor was calcined at six different temperatures between 250 and 750 °C and the resulting catalysts were tested in order to evaluate the influence of the calcination temperature on the catalytic activity and stability. XRD characterization showed that from 250 °C the hydrotalcite structure is no longer detected, leading to Mg(Ni,Al)O solid solutions, where no peaks related to lanthanum appear. An increase on the calcination temperature increased the grain size and cell parameter value. 50 h-catalytic tests were carried out at 700 °C, CH₄:CO₂ molar ratio of 1:1 and a mass/feed alimentation ratio (W/F) of 0.4 mg min cm^− 3. Used catalysts were characterized by temperature programmed oxidation (TPO), scanning electron microscopy (SEM) and Raman spectroscopy in order to obtain information about coke deposition. Catalytic tests highlighted the great influence of calcination temperature over catalytic activity and stability, having found that, as a general trend, calcination temperatures below 750 °C decrease both the stability and catalytic activity, with the exception of the catalyst calcined at 550 °C, where a higher activity was achieved but with a comparatively low stability.     

Biogas Production of Ozone and/or Microwave-Pretreated Canned Maize Production Sludge

The production of canned maize is accompanied by formation of large volumes of waste water, with high contents of starch, and high chemical- and biochemical oxygen demand. In our work the effects of acidic, microwave and ozone pretreatment on the biogas production and aerobic biodegradability of canned maize production sludge were examined and the energy balance of the processes were determined when different sludge pretreatments were used. It was found that ozone treatment decreased the chemical oxygen demand, while the biochemical oxygen demand and the aerobic biodegradability increased. The combination of microwave and ozone treatment increased the biodegradability relative to ozone treatment alone.