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Phosphorus recovery from liquid digestate
Heger, Jan ; Procházková, Michaela (referee) ; Touš, Michal (advisor)
The focus of this thesis is the posibility of obtaining phosphorus from liquid digestate. The theoretical part of the thesis is focused on summarizing the current situation regarding phosphorus recovery. The research summarizes the essential information about the method of struvite precipitation, by which phoshphorus is obtained in the form of struvite, which can be further used as a fertilizer. Based on the process information, an experimental device was designed to obtain phosphorus in the form of struvite, corresponding to industry standards. It is a cylindrical vessel with a conical bottom, in which the liquid digestate with the chemicals is mixed with a stirrer. The functionality of the device was tested experimentally on the created device. The results of the experiment were analyzed by XPS method, which confirmed the formation of struvite. For future operation, modifications of the device and pre-treatment of the liquid digestate were proposed, which could improve the whole process and its results.
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Integration of a technology for digestate thickening in a biogas plant
Miklas, Václav ; Touš, Michal (referee) ; Vondra, Marek (advisor)
This diploma thesis is mainly focused on the digestate thickening in a biogas plant. First, overview of the biogas technology in the Czech Republic is presented. Furthermore, problems with waste heat utilization and processing of fermentation residues (digestate) are described in more detail. Based on the research, multi-stage flash (MSF) evaporation was chosen as the technology for the digestate thickening. The main part deals with the integration of the chosen technology into a biogas plant process. The programming language Python was used to simplify the given task. In the preliminary stage, a complex mathematical model of a biogas plant was created, focusing particularly on the mass and energy balances. Subsequently, a computational model of the MSF evaporator was programmed. A procedure for the integration was suggested using the sensitivity analyses. Additionally, the model of a biogas plant was extended with the MSF evaporator. The key outcome of the thesis is a technical-economic analysis in which the impact of digestate transport price and electricity feed-in tariff on payback period is investigated. The results suggest profitability of MSF evaporator for biogas plants without subsidized feed-in tariff. Contrastingly, installation of MSF evaporator in older biogas plants with subsidized feed-in tariff can be economically viable only in cases of significantly longer transport distances.
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Fermentation remainder treatment in a biogas plant
Budín, Oto ; Touš, Michal (referee) ; Vondra, Marek (advisor)
This diploma thesis deals with dewatering technologies of fermentation residues from biogas plants and aims to design an integration of selected technology into the biogas plant. Fermentation residues (or digestate), which are a by-product of anaerobic biomass fermentation in biogas plants, contain a certain amount of nutrients and are usually used as agricultural fertilizers. However, the high-water content in digestate and the associated low nutrient concentration increase the cost of its storage and transport. Dewatering of fermented material could help reduce these costs. The main part of this work included the design of an integration of the selected dewatering technology into the biogas plant – its placement in a process, an addition of necessary appliances, the influence on material and energy flows. In this case, the fermentation residues are processed in two phases. First, a separation of the solid and the liquid fraction by a screw press. The second step is to thicken the liquid digestate by evaporation in a multistage evaporator. Evaluation of the design of a dewatering technology, including its impact on the economy of the biogas plant, is also part of the diploma thesis.
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Liquid-vapor mass exchange in stripping processes
Liman, Martin ; Kalivoda, Josef (referee) ; Svěrák, Tomáš (advisor)
This diploma thesis deals with the solution of ammonia separation from waste raw materials of agricultural production. It focuses on determining the efficiency of desorption from an experimental stripping device depending on the measurement temperature. Ammonia water solutions and liquid digestate samples from technical practice were used to verify the functionality of the equipment. Increasing separation efficiency with increasing temperature has been demonstrated. The device was gradually improved during the measurement for a better profitability of the separation process. The results of the experiments are discussed concerning the theoretical assumptions and compared with other methods of ammonia separation.
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Dependence of Sludge Thermal Pre-treatment on its Dewatering
Žerava, Zdeněk ; Houdková, Lucie (referee) ; Boráň, Jaroslav (advisor)
The first part of the thesis is focused on the problems related to sludge and evaluates sludge disposal from waste treatment plants. The thesis mentions factors influencing method selection of sludge disposal as well as it compares sludge disposal in the Czech Republic and in the other states of the EU. It describes a complete waste treatment line and sludge disposal in the area of sludge treatment and disposal. It deals with sludge disintegration and describes the most effective methods of disintegration. The second part of the thesis describes an experimental part of disintegration of waste treatment sludge. An experiment was conducted in the school laboratory in a way of thermal disintegration in the double-surface pressure tank. The disintegration was conducted to temperatures of 60 °C, 90 °C, 120 °C, 150 °C, and 180 °C. We monitored dependence of the sludge dry residue content on disintegration temperature as well as content of suspended solids in liquid fraction (FUGAT). It was possible to choose optimal temperature of disintegration in accordance with processed results.
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Assessment of evaporator integration into biogas plant
Peťovský, Patrik ; Touš, Michal (referee) ; Máša, Vítězslav (advisor)
The main waste output of the biogas plant is digested which is used as fertilizer. It can be further process. Digestate cannot be discharged freely into surface waters. This problem is associated with high transportation costs and higher costs of storage tanks in the new biogas plant. The aim of this bachelor thesis is to assess a suitable evaporation system for a particular biogas plant. The evaporation system leads to the concentration of digestate by evaporation water. The system uses heat produced by cogeneration unit. The main consequence of the integration is lower cost for the transport of liquid digestate. The output of the bachelor thesis is a technical and economic evaluation that assesses the payback period depending on the flow of concentrated digestate. The specific costs for adjustment of liquid digestate with regard to the payback period are in the range of 5–15 years. The values do not exceed 210 (Kčyear)/t_fug . The values considering selling heat are even negative. The minimum value guaranteed by the manufacturer is around 260 (Kčyear)/t_fug . The integration of the evaporation system into Žamberk's biogas plant is economically disadvantageous. The thesis brings new knowledge about the potential of multi-stage flash evaporation in biogas plants with short transport distances and high utilization of waste heat.
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Foaming of fermentation residues during a vacuum evaporation
Knob, Jan ; Brummer, Vladimír (referee) ; Vondra, Marek (advisor)
The diploma thesis deals with the processing of digestate, which is the remaining material after biogas production. It aims to experimentally prove how chosen operational parameters of antifoaming agents influence digestate foaming associated with the vacuum evaporating technology. Based on the research of available antifoamers and the issue of digestate foaming itself, it was observed how three selected antifoamers (i.e. rapeseed oil, silicone antifoamer Erbslöh Schaum-ex and oleic acid), together with the decrease in the pH factor of the evaporating digestate, influence the final foam production. For the purposes of the research, an apparatus simulating the vacuum evaporating process was set up in which the heated sample was brought to boil by gradual pressure decrease. The process of foaming was observed in a transparent cylinder of a testing culumn. The essential part of the experimental activity is represented by a planned experiment which by means of a DoE (Design of experiments) method proved rapeseed oil to be very efficient. In contrast, other antifoamers, as well as the influence of the pH factor decrease, manifested themselves as insignificant factors, while the oleic acid even supported the foaming. The supplementary measurements led to a more detailed research of the effects of rapeseed oil and to the construction of a mathematical model describing how the concentration of rapeseed oil undermines the amount of generated foam. The main contribution of the thesis is firstly the evidence that rapeseed oil plays an important part in the reduction process of digestate foaming and secondly the determination of minimum substance concentration leading to the foaming reduction of a particular sample which is considered efficient enough to enable functioning of a vacuum evaporator. The thesis has also experimentally demonstrated the influence of some polymer organic flocculants which have been proved to support the foaming.
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Equipment for Thickening Waste Water from Biogas Plants
Vondra, Marek ; Bébar, Ladislav (referee) ; Hoffman,, Pavel (referee) ; Stehlík, Petr (advisor)
This dissertation thesis deals with the development of technology which could tackle two major issues related to biogas plants. These issues concern the insufficient use of waste heat from biogas combustion and its subsequent processing. It also concerns the use of the fermentation residues which are formed in large quantities and whose use is restricted by law. Based on a literary search of separation methods, a vacuum evaporator was selected as the most suitable technology. Its advantages include its simple construction, operational reliability and robustness, low costs of thickening medium pre-treatment, potential for a quick commercial application and, especially, the chance to use a low-potential waste heat. A primary purpose of this technological unit is the reduction in the volume of fermentation residues. Other benefits include the efficient use of waste heat from a biogas plant, which would otherwise be wasted. Evaporators with a low consumption of electrical energy (which is a main product of a biogas plant) seem to be the best option for applications in the biogas plants. Three of these technologies were subjected to a more thorough analysis, which included the development of computational models and their quantification for conditions in a sample biogas plant. A one-stage evaporator with a forced circulation (680 – 712 kWhth/m3, 25.9 – 30.5 kWhel/m3) was evaluated as the least suitable option in terms of energy demands. The energy intensity of a three-stage evaporator with a falling film (241 – 319 kWhth/m3, 12.0 – 23.6 kWhel/m3) and a nine-stage flash evaporator (236 – 268 kWhth/m3, 13.6 – 18.4 kWhel/m3) is significantly lower. A multi-stage flash evaporator (MSF) was then chosen for development and will form the central focus of this thesis. The reasons for the choice are as follows: the low requirements on the heat transfer surface, good operational experience in the field of desalination, its simple construction, modularity and evaporation outside the heat transfer surface. A thorough technical-economic evaluation was also performed on the integration of the evaporator into the biogas plant. The main part of the work included the experimental development of a MSF evaporator prototype. The main objective of this development was to achieve a stable flow rate of the thickening liquid digestate fraction and the continuous formation of the distillate. This was not an easy objective to achieve, especially due to the properties of the liquid digestate, which has a non-newtonian characteristic and increased density and viscosity compared to water. The tendency of the liquid digestate to form foam was also the subject of analysis. The development of the evaporator and first successful operational test are described in the thesis in detail. This required the use of an anti-foaming product. A fully-developed prototype of the MSF evaporator allowed us to achieve continuous operation with a distillate production, reaching from 5 to 10 kg/h at a liquid digestate flow rate of 0.4–0.5 m3/h. The main drawback of this technology is the pollution of the distillate with ammonia nitrogen, and it is for this reason that the basic procedures of its subsequent elimination was selected for further analysis.
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Measurement of selected physical properties of the waste water from biogas plant
Ondruška, Vojtěch ; Zejda, Vojtěch (referee) ; Vondra, Marek (advisor)
The aim of this Bachelor’s thesis is the experimental measurement of physical and chemical properties of the wastewater from biogas plants. Thesis concisely describes wastewater and its origin. The main part is dedicated to the design of experiments and to the detailed description of the measurement of selected properties with the available laboratory methods. Measured data are evaluated and compared to literature. The results of this thesis can be employed to further develop the equipment for thickening wastewater from biogas plants or to other scientific activity in the field of waste management in agriculture.
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Dependence of Sludge Dewatering efficiency on amount of flocculant
Volejník, Tomáš ; Medek, Jaroslav (referee) ; Boráň, Jaroslav (advisor)
The target of the first part of this diploma thesis is focused on the problems relating to the sludge production from the wastewater treatment plant and subsequent sludge treatment. Wastewater treatment plant and individual processes from the sludge management are described. The process of the sludge dewatering is described more extensively. Various methods of the dewatering and materials balance are described, too. The second part of this thesis is based on the experiment which took place on wastewater treatment plant Tetčice. The influence of the polymeric organic flocculant dosing on the sludge dewatering was monitored by this experiment. Dependence of the sludge dry matter and filtrate suspended solids content on the specific amount of flocculant was evaluated from experiment’s outputs. Using materials balance and outputs of the experiment, economical balance was made. It made possible to choose the most economic and technologically optimal way of the sludge dewatering on wastewater treatment plant Tetčice.
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