The effect of low temperature on the explosion characteristics of a methane/air mixtures

Prevention and mitigation of unwanted explosions require knowledge of explosion characteristics. Available explosion data are not always adequate for use in a particular application. For example, predicting the behavior of gas explosions at a lower temperature should be based on the explosion data obtained at these temperatures and not atmospheric. Basic knowledge of the methane explosions at low temperatures is desirable for a thorough understanding of this gas that cannot be found in the literature. In the presented research, the methane/air deflagrations were studied in the millisecond time domain. The standard 20-L deflagration chamber was adopted to produce consistent and reproducible data for the comparison of atmospheric and low initial temperature measurements. Methane/air mixtures were studied experimentally for concentrations between 4.6 vol.% and 16.6 vol.% and two initial temperatures of 20 and -5 degrees C. More than three hundred and fifty pressure-time curves were recorded and analyzed. Twenty-five deflagration curves of the methane/air mixtures were studied in 20-L volume for the first time, including thirteen pressure-time curves at -5 degrees C. The effects of temperature on the maximum rate of pressure rise and deflagration index were investigated. The evaluated experiments' results are the maximum pressure rise rate of 261 bar/s at -5 degrees C. This work allowed potential hazards involving the handling and storing of fuels. Many pieces of knowledge must be collected to advance the phenomenological understanding of low-temperature deflagrations to make realistic theoretical predictions and correlations.Web of Science830830

Coke oven gas-to-liquid synthesis: Experimental approach

Carbon resource utilisation is one of the many options to reduce carbon emissions and create additional value from ecological and economic points of view. The utilisation of e.g. process or residue gases is carried out through different technological process steps, including various technologies to convert carbon-rich gases to high value-added products in the form of hydrocarbon (HC) compounds. Several types of residue gas from the iron, steel and coke industries containing different types of elements such as H-2, CH4 and CO are valuable feedstock for carbon utilisation systems. In this study, the possibility of coke oven gas (COG) conversion to HCs using a cobalt catalyst was examined. For a better understanding of the whole process, chromatographic analysis was performed to determine the exact composition of the HC chains synthesised from the COG. The results had shown the efficiency of the liquefaction very close to 20 % w/w for every investigated temperature regime, however, the character of the produced hydrocarbon chains varied. The findings suggest increased production of alcohols of C4 to C9 groups in lower temperatures, while a broad range of alkanes and alkenes C7 to C19 can be efficiently produced if the synthesis temperature is increased.Web of Science9757

Torrefaction and gasification of biomass for polygeneration: Production of biochar and producer gas at low load conditions

In this paper, a matter of biomass torrefaction and gasification is closely looked at from different points of view during low load and low equivalence ratio regime, defined as lambda = 0.08. Considering gas production, the hot gas efficiency of conversion (30%) and its energy content (4.14 MJ m(-3)) were not quite satisfying, however, this matter of fact was compensated by an interesting yield of biochar. This material was generated in 0.387 and 0.314 rates for torrefaction and torrefaction + gasification processes, respectively, which, in both cases, represents an attractive, alternative approach to the functional energy storage. It was determined that a CO2 offset of 721 kg and 660 kg could be achieved per 1 tonne of woodchips for gasification of raw woodchips and a 2-stage process with torrefaction and gasification, respectively. The measured data from both technological complexes were compared with the computational model, applying equilibrium reactions for gas components determination. In addition, the question of tar compounds contained within the producer gas, is investigated through GC-MS analysis on both qualitative and quantitative basis.Web of Science814413

Návrh úpravy reaktoru zplyňovací technologie

In this thesis, gasification and its principles are briefly introduced together with chemical reactions as well as different ways of gasification in terms of reactor types, in the research part of the work. The principal part of the thesis deals with heat issue of the bottom part of reactor of Energy Research Centre in Ostrava. In order to solve this issue, cooling apparatus design is proposed and calculated from many technological and safety aspects. The cooling water is then supposed to be utilised in form of hot steam, which might enhance the gasification process, if injected into the reactor. Thus, steam boiler and piping are proposed as well in this thesis. Such proposal solves technological problem and at the same time brings new possibilities on field of science of Energetic Research Centre in Ostrava.V teoretické části diplomové práce je stručně představeno zplyňování a jeho princip společně s chemickými reakcemi, a také různé druhy zplyňování v závislosti na druhu reaktoru. Hlavní část práce je zaměřena na tepelný problém ve spodní části reaktoru Výzkumného energetického centra v Ostravě. S cílem vyřešit tento problém, chladící aparát je navrhnut a kalkulován z několika technologických a bezpečnostních aspektů. Chladící voda je dále plánována k využití výrobě páry, která může vylepšit zplyňovací proces, pokud je vedena zpět do reaktoru. Tedy parní kotel a potrubní cesta jsou také navrhnuty v této diplomové práci. Tento návrh tedy řeší technologický nedostatek a zároveň přináší nové možnosti na poli vědy ve Výzkumném energetickém centru v Ostravě.361 - Katedra energetikyvelmi dobř

Specific Energy Consumption of Turbocharger Driven by Condensing Turbine

Import 02/11/2016Tato bakalářská práce se zabývá soustrojím parní turbíny a turbodmychadla, zapojených v parním cyklu společně s regeneračními výměníky tepla. V první části je popsán historický vývoj parních turbín, kompresorů a tepelných výměníků, dále jejich využití a princip funkce. Druhá část bakalářské práce je zaměřena na metodiku stanovení postupu výpočtu měrné spotřeby energie turbodmychadla pro případy s různým počtem zapojených regeneračních ohříváků.This bachelor thesis deals with a set of steam turbine and turbo compressor, joined in a steam cycle along with regenerative heat exchanger. The first part describes the historical evolution of steam turbines, compressors and heat exchangers, followed by their usage and principals of function. The second part focuses on determining of computing process method of specific energy consumption of turbo compressor for various number of regenerative exchangers.361 - Katedra energetikyvelmi dobř

The effect of low temperature on the explosion characteristics of a methane/air mixtures

Prevention and mitigation of unwanted explosions require knowledge of explosion characteristics. Available explosion data are not always adequate for use in a particular application. For example, predicting the behavior of gas explosions at a lower temperature should be based on the explosion data obtained at these temperatures and not atmospheric. Basic knowledge of the methane explosions at low temperatures is desirable for a thorough understanding of this gas that cannot be found in the literature. In the presented research, the methane/air deflagrations were studied in the millisecond time domain. The standard 20-L deflagration chamber was adopted to produce consistent and reproducible data for the comparison of atmospheric and low initial temperature measurements. Methane/air mixtures were studied experimentally for concentrations between 4.6 vol.% and 16.6 vol.% and two initial temperatures of 20 and −5 °C. More than three hundred and fifty pressure–time curves were recorded and analyzed. Twenty-five deflagration curves of the methane/air mixtures were studied in 20-L volume for the first time, including thirteen pressure–time curves at −5 °C. The effects of temperature on the maximum rate of pressure rise and deflagration index were investigated. The evaluated experiments’ results are the maximum pressure rise rate of 261 bar/s at −5 °C. This work allowed potential hazards involving the handling and storing of fuels. Many pieces of knowledge must be collected to advance the phenomenological understanding of low-temperature deflagrations to make realistic theoretical predictions and correlations

Coke oven gas-to-liquid synthesis: Experimental approach

Carbon resource utilisation is one of the many options to reduce carbon emissions and create additional value from ecological and economic points of view. The utilisation of e.g. process or residue gases is carried out through different technological process steps, including various technologies to convert carbon-rich gases to high value-added products in the form of hydrocarbon (HC) compounds. Several types of residue gas from the iron, steel and coke industries containing different types of elements such as H2, CH4 and CO are valuable feedstock for carbon utilisation systems. In this study, the possibility of coke oven gas (COG) conversion to HCs using a cobalt catalyst was examined. For a better understanding of the whole process, chromatographic analysis was performed to determine the exact composition of the HC chains synthesised from the COG. The results had shown the efficiency of the liquefaction very close to 20 % w/w for every investigated temperature regime, however, the character of the produced hydrocarbon chains varied. The findings suggest increased production of alcohols of C4 to C9 groups in lower temperatures, while a broad range of alkanes and alkenes C7 to C19 can be efficiently produced if the synthesis temperature is increased

Torrefaction and gasification of biomass for polygeneration: Production of biochar and producer gas at low load conditions

In this paper, a matter of biomass torrefaction and gasification is closely looked at from different points of view during low load and low equivalence ratio regime, defined as λ=0.08. Considering gas production, the hot gas efficiency of conversion (30%) and its energy content (4.14 MJ m−3) were not quite satisfying, however, this matter of fact was compensated by an interesting yield of biochar. This material was generated in 0.387 and 0.314 rates for torrefaction and torrefaction + gasification processes, respectively, which, in both cases, represents an attractive, alternative approach to the functional energy storage. It was determined that a CO2 offset of 721 kg and 660 kg could be achieved per 1 tonne of woodchips for gasification of raw woodchips and a 2-stage process with torrefaction and gasification, respectively. The measured data from both technological complexes were compared with the computational model, applying equilibrium reactions for gas components determination. In addition, the question of tar compounds contained within the producer gas, is investigated through GC–MS analysis on both qualitative and quantitative basis

Solid recovered fuel gasification in sliding bed reactor

This study examines a solid recovered fuel gasification process in the context of a regional, clean energy supply from an affordable source. The examination of this approach was performed under various equivalence ratios and load regimes. A unique cross/updraft gasification reactor with a fixed (sliding) bed over the circular grate with tangential gasification media intake was utilised. This technology is a perspective in waste-to-energy and waste-to-materials production. The investigated parameters included producer gas quality and purity, overall conversion efficiency and char material yield. It was found that a low material load is very beneficial in terms of gas purity and conversion efficiency, reaching up to 93%. Also, the formation of tar compounds was measured as low as 0.7 g/m3. However, when the equivalence ratio parameter was 0.14, the gas's lower heating value was only 2.4 MJ/m3. Also, a lower heating value equal to 5.0 MJ/m3 was reached in a low-efficiency regime (48%) when the fuel load was more significant (48.5 kg/h), and the equivalence ratio was only 0.04. The low tar content suggests a very clean process. Also, the material valorisation in the form of char is beneficial as this carbon-rich material no longer has a waste character and can be utilised in many fields.Web of Science278art. no. 12783

Charakterystyka eksplozji gazu syntezowego z procesu zgazowania

This paper describes a series of experiments performed to study the explosion parameters of syngas and its flammable component air mixtures. More than 100 pressure-time curves were recorded allowing to investigate the effects of three different gasification process conditions on the maximum explosion pressure and deflagration index. The representative syngas samples were prepared by thermochemical wood-pellets gasification. The experiments were performed in 20-L oil-heated spherical experimental arrangement for different concentrations at representative explosion initial temperature of 65 degrees C. The experimental results were further compared with the explosion parameters of pure gases, namely hydrogen, methane, carbon monoxide and propane as the main flammable syngas components. The most important results are the maximum values of explosion pressure 7.2 +/- 0.2 bar and deflagration index 170 +/- 14 bar.m/s derived for start-up process conditions. These knowledge could be used to understand the effects of operating conditions to both the optimization design on syngas-fueled applications and the safety protection strategies.Artykuł opisuje serię eksperymentów wykonanych w celu zbadania parametrów eksplozji gazu syntezowego oraz jego części palnych w mieszaninie z powietrzem. Więcej niż 100 krzywych w układzie ciśnienie-czas zostało zarejestrowanych pozwalając na zbadanie efektów trzech różnych warunków procesu zgazowania przy maksymalnym ciśnieniu eksplozji i wskaźniku deflagracji. Reprezentatywne próbki gazu syntezowego zostały przygotowane za pomocą zgazowania termochemicznego drewnianych granulek. Eksperymenty zostały wykonane w podgrzewanej olejem instalacji o kształcie sferycznym, której objętość wynosiła 20 Li wykorzystana została dla różnych stężeń oraz reprezentatywnej temperatury wstępnej na poziomie 65°C. Wyniki doświadczalne były następnie porównane z parametrami wybuchu czystych gazów, którymi były wodór, metan, tlenek węgla oraz propan, jako główne składniki gazu syntezowego. Najważniejszymi wynikami okazały się maksymalne wartości ciśnienia wynoszące 7,2 ± 0,2 barów oraz wskaźnik deflagracji na poziomie 170 ± 14 bar.m/s wyznaczony dla warunków startowych procesu. Informacje te mogą zostać wykorzystane w celu zrozumienia wpływu warunków operacyjnych dla optymalizacji zastosowań gazu syntezowego oraz strategii bezpieczeństwa związanego z jego wykorzystaniem.Web of Science2120019