Sirvi Autor "Bradna, J." järgi
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Kirje Comparison of a 1 t and a 55 t container when storing spelt grain in mild climate of the Czech Republic(2019) Bradna, J.; Šimon, J.; Hájek, D.; Vejchar, D.; Polišenská, I.; Sedláčková, I.Maintaining a suitable microclimate inside the storage space is the most significant factor in maintaining good quality of stored grain for small farmers. This article is aimed at evaluating the influence of outdoor climatic conditions on the storage conditions, specifically the temperature of stored grain in two storage containers. One structure was a 4 × 6 m cylindrical container (55 t capacity) with a steel wire mesh wall lined with a textile shell. Spelt grain (Triticum spelta) was also stored simultaneously at the same location in a fabric intermediate bulk container (FIBC) bag with maximum capacity of 1 t. Neither structure was mechanically aerated. Grain moisture and temperature were monitored during the spring and start of the summer period of the year 2017 because of the biggest differences between the night and day temperatures. For monitoring of the grain microbiological changes samples were taken for laboratory tests during the whole experiment. Grain quality parameters measured during storage included the bulk density, crude protein, falling number, germination, gluten content, sedimentation index and contamination by mycotoxins. Monitored outdoor environment parameters were temperature, dew point and relative humidity. Results showed a strong dependence of the stored material temperature on the outside temperature in the case of FIBC bags (coefficient of determination R 2 = 0.927), whereas the dependence was weaker in the larger structure (R 2 = 0.625). Mycotoxins monitored during the period were below the detection limit in both cases.Kirje The effect of bedding amount on gas emissions from manure during storage(2017) Šimon, J.; Vegricht, J.; Bradna, J.One of the major agricultural pollutants of environment is manure from livestock. We focused on dairy cows kept in the barns with straw bedding commonly used in the Czech Republic. We tested the hypothesis that the amount of bedding used daily relative to the number and size of animals kept has a significant effect on the emissions of gases from manure stored in a manure pile. In the experiment, a group of 10 dairy cows of Holstein and Czech Red Pied breed was housed in a stable bedded with various amounts of wheat straw (4–10 kg/livestock unit per day). The manure was removed from the stable after 48 h and mixed was stored in cubic containers with drain floor allowing measurement of manure leachate release. For 50 days we measured weight, volume, weight of manure leachate and manure temperature. Decreasing stored manure weight can be attributed to release of manure leachate and emissions of gases, primarily water vapor, as a result of microbial activity and increased temperature in the manure during storage. Using the calculated model, we found that daily production of emissions of water vapor and other gases was related to bedding amount in a statistically significant manner (P < 0.001). The cumulative amount of gas emissions grew rapidly in all treatments. Also total amount of emissions was related to bedding amount in a statistically significant manner (P = 0.004). We also found the relationship between internal manure temperature and the logarithm of the amount of emissions produced to be statistically significant (P < 0.001).Kirje Energy consumption of milking pump controlled by frequency convertor during milking cycle(2018) Vaculik, P.; Prikry, M.; Bradna, J.; Libich, L.The article deals with selected parameters affecting the energy consumption of a vacuum pump in a milking system during the whole milking cycle in variants with and without regulation by a frequency convertor. When put into practice, the latest research of creation, control and stabilization of vacuum in milking devices allows dairy farmers to obtain a vacuum system that ensures maximum stability of milking pressure, which is a basic requirement affecting the health of dairy cows. The choice of vacuum system prioritizes in particular high performance, maximum operational reliability, minimum maintenance, long service life, environmental friendliness and economy. The vacuum pump was a Roots vacuum pump with a rotary piston which is typical for this use. Use of a frequency convertor significantly affected the efficiency of this pump for control of vacuum pressure level and pump performance by varying the rotation frequency according to the actual airflow requirement. Using this control system, only as much vacuum pressure is produced as necessary. By measurement of an experimental setup, it was found that the average power requirement of a setup with a control valve was 3.8 kW compared to 1.7 kW in the case of the variant with frequency convertor. Measurements and calculations have shown that this system is capable of saving more than 50% of electric energy.Kirje Evaluation of dried compost for energy use via co-combustion with wood(2018) Malaťák, J.; Bradna, J.; Velebil, J.; Gendek, A.; Ivanova, T.There is still a question of utilization of compost of unsatisfactory quality. This article deals with energy utilization of untreated compost. The energy utilization of raw compost as a fuel is not directly possible without further processing. Separation might be necessary due to large amount of mineral content (soils and other inert substances). This article is focused on the analysis of the basic fuel characteristics of compost. Proximate and elemental analyses were performed and stoichiometric combusti on was calculated. Finally, the sample was co - burned with wood biomass in a fixed grate combustion device and the gaseous emissions were determined in dependence on the amount of combustion air supplied. The emissions were expressed in graphs against exces s air coefficient and flue gas temperature. Elemental analysis of the compost sample shows high percentage of ash up to 61.70% wt. on dry basis causing low average calorific value of 8.51 MJ kg - 1 on dry basis. For combustion tests, the heating value was in creased by addition of wood chips to reach an average calorific value of the mixture to 13.4 MJ kg - 1 . The determined stoichiometric parameters can help in optimization of diffusion controlled combustion of composts or similar materials. In combustion of th e mixture of compost and wood biomass an optimum of emission parameters was found not exceeding the emission limits. Measured emission concentrations show the possibility of optimizing the combustion processes and temperatures while lowering CO emissions v ia the regulation of combustion air.Kirje The impact of weather conditions on microclimate in storage facilities(2018) Bradna, J.; Šimon, J.; Hájek, D.; Vejchar, D.The key to maintaining good qualitative parameters of stored grain on farms is to achieve and maintain suitable storage temperatures relative to the outside temperature. In the framework of this research, the main focus was on typical representatives of grain storage facilities used in the Czech agriculture. In the post - harvest period after the crops were stored in the chosen storage facilities, the temperature of the material was monitored at 15 - minute intervals using an external temperature probe as well as the temperature and dew point of the outdoor air. A simple linear regression model was used for data analysis. The correlated temperature d ependence of the stored grain varies considerably in the monitored storage facilities. The storage halls were characterized by a low dependence (r = 0.2208) of the temperature of the material on the outside air temperature in the first 4 months following t he harvest when the grains were being stabilized by active aeration. In addition to the grain and the air temperature, the second focus was monitoring the dew point, i.e. assessing the risk of water vapour condensation on the surface in the upper layer of the stored grain, which is very undesirable for maintaining the quality of the stored grain. The results show that the monitored storage hall can be characterized by the ability to maintain the required climate due to outdoor climatic conditions. In genera l, this ability mainly depends on the type and design of the storage facility, the aeration system and also the storage capacity. Mainly during spring the dew point and water vapour condensation can often happen within the grain, therefore the need to focu s on appropriate measures such as reduced aeration or increased grain mixing, and thus avoiding the formation of critical spots.Kirje The potential of energy recovery from by–products of small agricultural farms in Nigeria(2019) Bappah, M.; Bradna, J.; Velebil, J.; Malatak, J.Agricultural by–products are renewable energy sources from which essential amount of energy can be recovered, which can be used to replace the use of conventional fossil fuel, reduces the potential of greenhouse gas (GHG) emission and at the same time reduces deforestation, especially in rural areas. Energy values of biomass from small Agricultural farms, in particular waste generated from different tropical crops, viz; Maize, Millet, Rice, Sorghum and Groundnut were determined, to ascertain their potentials as alternative fuel sources for rural use. The materials were found to be of importance judging by their combustion potentials in all the forms investigated. The Energy values of the by-products considered ranged between 11.68 MJkg-1 to 17.48 MJkg-1 with Groundnut pods and millet husk having the highest and least respectively. Moisture and ash had effect on the energy values of these biomass. Our results are relevant to the problems posed by the management of farm residues in developing countries.Kirje Specialty types of waste paper as an energetic commodity(2018) Malaťák, J.; Velebil, J.; Bradna, J.The collection and recycling rate of paper and paper packaging material has been on a rise. From 2010 to 2016 in Czech Republic, the recycled amount of all paper went up by 32%, while the share of energy use in waste paper utilization decreased f rom 5.5% to 3.8%. However, not every paper and cardboard product can be recycled, and some are rejected from the recycling stream. Recycling specialty types of paper with other grades of recyclable paper is often not possible and their production is not hi gh enough for their separate recycling to be feasible. If material utilization is not feasible then within the waste hierarchy the next best treatment is their energy utilization. Therefore, this article evaluates selected types of specialty paper for thei r energy content. They were silicone coated papers, polymer coated papers, and paper cores. For all samples proximate, elemental and calorimetric analyses were determined and based on them stoichiometric combustion calculations were performed. Silicon coat ed papers fared generally well having small to reasonable ash content 1 – 10% and net calorific value from 15.10 to 17.10 MJ kg - 1 on dry basis. Polymer coated papers had ash content around 6% and net calorific value from value from 16.29 to 22.98 MJ kg - 1 on dry basis. With the exception of paper cores and self - copying paper, all evaluated paper types could be recommended as a component in refuse derived fuels. The least suitable samples were paper cores with nearly 20% wt. of ash and net calorific value 12.45 MJ kg - 1 on dry basis.Kirje Suitability of 2.4 GHz and 5 GHz wireless communications in production processes(2019) Hart, J.; Bradna, J.Today, it is increasingly modern to use wireless transmissions in production. It is possible to send information messages, control messages and it is often possible to access the technologies as IoT (the Internet of Things). The aim of this work was to find out which of the selected Wi-Fi frequencies is more suitable for use in syrup processing equipment. The evaluation was performed on the basis of attenuation and download speed at each frequency (2.4 GHz and 5 GHz bandwidth). These frequencies have been chosen due to their massive deployment for wifi networks that currently dominate wireless communications. Measurements were made downloading files on different frequency bands. Mean and maximum data throughput and signal strengths were also measured. By measuring, it has been found that when using 2.4 GHz wireless Wi-Fi technology, you can very often encounter strong interference effects. Despite the theoretically worse 5 GHz frequency spread, you can achieve up to 30% better data throughput on average. The results show the suitability of 2.4 and 5 GHz Wi-Fi technology. The main finding is that, despite the worse frequency spread of 5 GHz, it is more appropriate. Not only due to speed but also in the future due to better transmission capacities and future channel expansion.