Browsing by Subject "Energieeffizienz"

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A full-scale study on efficiency and emissions of an agricultural biogas plant
(2013) Nägele, Hans-Joachim; Jungbluth, Thomas
In this study we focused on process engineering for the conversion of biomass, and utilization of the gas obtained by fermentation. Several topics regarding efficiency and emissions have been addressed by conducting intensive and long-term measurements. In detail, our objectives were (1) to conduct long-term measurements of the electric energy consumption of the biogas plant and its individual components and examination of energy-saving potentials; (2) to develop a method to measure mixing quality in the digester and to examine the mixing quality by measuring nutrient distribution in the digester with different agitator setups; (3) measure the influence of maintenance strategies on efficiency and emissions at long-term operation in practical application; (4) examine the efficiency of an external biological desulfurization plant under practical conditions to enhance biogas fuel quality. The results of electric energy measurement over a period of two years showed that a percentage of 8.5% (in 2010) and 8.7% (in 2011) of the produced electric energy was required to operate the biogas plant. The consumer unit agitators with 4.3% (in 2010) and 4.0% (in 2011) and the CHP unit with 2.5% (in 2010 and 2011) accounted for the highest electrical power demand, in relation to the electric energy produced by the CHP unit. Calculations show that the agitators consumed 51% (in 2010) and 46% (in 2011) of the total electric energy demand. The results stress the need for further research in the fields of substrate homogenization in biogas plants in order to reduce the demand for electric energy. Based on the results of electric energy consumption, follow-up studies have been conducted on nutrient distribution, which depends on agitator type and agitator regime. The investigation showed that significant differences in local concentrations of organic acids, which are not correlated to DM content, are found in dependence on agitator type and agitation regime. Measurements on electric energy consumption of the different agitator types verified that, depending on the agitator type, the saving potential rises up to 70%. The results for emissions and efficiency of the CHP unit confirm the fact that after readjustment of the air-fuel ratio (Lambda value), the emission values for NOx decline while CO increases. However, the emission-optimized operation mode leads to lower engine efficiency. The permanent measurements proved their legitimacy showing various emission deviations from the limiting values prior and post maintenance. In addition, the results show that by monitoring the lubricating oil quality, the oil change intervals can be maximized, while ensuring that engine performance is not endangered. This allows the operator to reduce maintenance expenditures while minimizing wear. To increase engine efficiency, the reduction of the lambda value combined with exhaust gas scrubbing and exhaust gas power generation is a promising approach. However, that would presuppose a permanent and almost total removal of H2S from the biogas. The fourth part of the study examined the technical and economic feasibility of a Fixed Bed Trickling Bioreactor (FBTB) for external biological desulfurization of biogas. In contrast to well-established biological methods to oxidize H2S, the FBTB allows removal of these from the biogas process, thus ensuring a constant low H2S concentration in the biogas. The FBTB showed H2S removal efficiencies (RE) of 98% at temperatures between 30-40°C. A major decline in RE in a range of 21-45% was observed when temperature in the FBTB dropped to a range of 5-25°C. The results revealed that different pH values of the percolation fluid and air ratios have little effect on RE. The practical use of the investigated FBTB system is an interesting technological alternative as disadvantages of internal biological desulfurization methods are being avoided. Due to high expenditures for operation resources and maintenance for FBTB operation during the research, a technical optimization is necessary to ensure economical operation. The results presented in this thesis show that the scientific instrument ?research biogas plant? is the ideal supplement to methods such as laboratory scale research and measuring programs. Research at full scale offers an entirely new opportunity to determine the interaction of process technique and process biology and to conduct long-term studies of gas utilization. Compared to measuring programs at commercial biogas plants, the research biogas plant has the advantage of being significantly better equipped with measurement technologies and that economic success is not the overall goal.
Potentialbewertung effizienzsteigernder Technologien bei Landmaschinen in Verfahrensketten mit Körnerfruchternte
(2023) Meiners, Arwid Steffen
Reducing fuel consumption in agricultural process chains through increased energy efficiency in machine use is effectively achieved through process-oriented approaches. Although European targets for greenhouse gas reduction are increasingly being demanded legislatively and socially, the farmer’s pressure to act is primarily motivated intrinsically due to economic constraints. There are technologies existing on the market that contribute to increasing machine and process efficiency. To this day, however, it is difficult to evaluate their economic use on a farm-specific basis before deciding on investments. The complexity of agricultural process chains encourages and demands comprehensive approaches for both the use and the evaluation of efficiency-increasing technologies and measures. The objective of this research is to develope and apply a proper evaluation method. As a virtual evaluation environment, a machine model is created which can be used to calculate time-related fuel consumption of agricultural machine combinations under the influence of efficiency-increasing technologies. Supplemented by a process model, the consumption of individual process chains and entire crop rotations can be simulated. A modular model topology allows flexible combinations of tractors and implements for process chains with grain crop production. Corresponding simulation models are built and parametrised. The focus is on developing a model for self-propelled harvesters and on parameterising it for application as a combine harvester. As a data basis for the process components, load and performance data are collected in field tests using a state-of-the-art hybrid combine harvester. At the same time this contributes to the general data availability of performance requirements of process components in harvesting operations. In the model application, a potential evaluation of efficiency-increasing technologies and measures, such as optimised traction conditions, driving strategies or reduced intensities in tillage and harvesting, is carried out on a virtual model farm representing typical process chains with grain crop production in the region of South Hanover. Optimisation potentials for three- and five-part crop rotations are established along the individual process steps. Specific recommendations from individual technology analyses are made for efficient use of the machinery in use. As an overall assessment, a potential for reducing fuel consumption of about 26% resulting from optimised machine efficiency can be identified.