Gas Generation Processes Research Articles

Gas-Generating Porous Electrodes: Calculating Complete Polarization Curves

A complete set of equations that allow one to estimate the maximum electrochemical activity of gas-generating porous electrodes (GGPE) is derived. The equations are valid if all stages that restrict the electrochemical process of gas generation are removed. The equations also allow one to calculate polarization curves throughout the entire range of variations in the overvoltage, provided no ohmic limitations are present in the system. The derivation is based on the lattice model describing the gas and electrolyte distributions over the GGPE thickness. The model was tested in previous works of the authors. Other basic characteristics of porous electrodes are calculated as well. These include, the overvoltage dependences of the oversaturation of electrolyte with gas, the electrolyte and gas porosities, the electrolyte-wetted specific surface area that takes part in the electrochemical gas evolution process, the average distance between neighboring pores, etc. The calculation makes use of constants close to those inherent in the chlorine generation process on DSA. The calculated polarization curves exhibit a clearly pronounced low-polarizability portion, which is the region of a rapid current increase in GGPE, which follows the linear Tafel portion. The presented theory gives one a chance to point out ways to change the structure of the porous space of GGPE and, in particular, DSA, in order to optimize characteristics of DSA and GGPE of other types in the future.

Gas-Generating Porous Electrodes: Calculating Characteristics in the Low-Polarizability Portion

It is shown in the paper how specific features of the structure of the porous space in gas-generating porous electrodes (GGPE) create conditions for the emergence of a low-polarizability portion (LPP) in a polarization curve (PC). A set of equations is derived, which allows one to perform calculation of PC in the initial part of LPP. In the region of small overvoltages and in the initial part of a low-polarizability portion, calculations of basic characteristics of GGPE are performed. The calculations are carried out with the values of constants that are close to those that take place for the process of chlorine generation in dimensionally stable anodes. The shape of PC is established, together with the distribution of the oversaturation of electrolyte solution with gas over the GGPE thickness, the specific liquid surface area at which the electrochemical process of gas generation occurs, the amount of gas in the pores of the porous electrode, the overvoltage dependence of the oversaturation of electrolyte solution with gas at the front surface of GGPE, and the magnitude of the effective penetration depth of the process of gas formation into the porous electrode.

Manufactured Gas in California, 1852–1940: Basis for Remedial Action

California was a relatively late entry (1852) in the manufactured gas industry. However, its gas entrepreneurs showed considerable invention and enterprise in establishing more than 250 separate gas plants, this in a total geographic environment approximating a whole nation of separate-operating and now environmentally endangering, conditions. Virtually all of the many gas generation processes and patent variations were employed in the state, and a wide variety of geologic conditions have created an even wider variety of fate and transport conditions related to their tar and other residuals. A complex development of holding companies and other management forms also need interpretation as to the level of operational understanding present at the many former manufactured gas plants and other coal tar sites. As with all locations worldwide, a close understanding of the conditions surrounding technical operation and waste management options is essential to correct planning for environmental remediation.

Aspects of Natural Gas Generation and Migration in Sedimentary Systems

The present state of natural gas research could be described as comprising a substantial amount of empirical wisdom with certain more or less isolated conceptual chemical and physical models on gas generation, migration and concurrent fractionation processes. The apparent lack of a comprehensive framework for quantitative description and prediction of natural gas generation and accumulation processes must be attributed to the complexity of this issue and the limited control on starting and boundary conditions of the pertaining processes in geological systems. Some basic issues of gas generation and migration that have been addressed in our recent research from an experimental and theoretical point of view will be presented and discussed in the following sections.

Gas simulation models for solid waste landfills

Sanitary landfills remain an attractive disposal route for municipal solid waste, because, in most cases, it is more economical than other alternatives such as incineration and composting. Although the composition of solid waste may very substantially with location and time, organic materials constitute the vast majority of this waste. Organic materials are susceptible to microbial decomposition that result in gas and heat generation within the landfill. The migration of gas away from the landfill boundaries and their release into the surrounding environment, present serious environmental concerns at both existing and new facilities. Mathematical models have been used widely to evaluate gas and heat generation and transport processes in landfills. This article presents a critical review of models designed to simulate biological, chemical, and physical processes responsible for the generation and transport of gas and heat in landfills.

Review of Ozone Processes and Applications as an Oxidizing Agent in Aquaculture

Abstract Ozone has been used in a range of aquaculture applications related to disinfection and improving water quality. Ozone has seen wide use because it is a powerful oxidizing agent that has a rapid reaction rate and few harmful reaction products. This paper reviews the application of ozone within aquaria and in aquaculture systems that use single-pass or recirculated water. The issues and mechanisms required to use ozone are reviewed, with particular emphasis on the processes of ozone gas generation and gas-to-liquid absorption, the contact time for reaction, and the removal of residual ozone. In addition, the toxicity of ozone to humans and to aquatic organisms is discussed, as well as techniques to monitor or control ozone in both the gaseous and aqueous phases.

97/01098 Multi-zone molten-metal hydrogen and fuel gas generation process using carbonaceous feeds including hazardous wastes

97/01098 Multi-zone molten-metal hydrogen and fuel gas generation process using carbonaceous feeds including hazardous wastes

5592831 Process for recovering a pure carbon monoxide fraction : Bauer Heinz;Fabian Rainer Ebenhausen, Germany assigned to Linde Aktiengesellschaft

Gas generation from low- and intermediate-level nuclear waste (LILW) is an important process related to the safety of near surface and geological nuclear waste repositories. Generation of a gas phase has the potential to transport gaseous radionuclides such as 14C to the biosphere. Furthermore, pressurisation and gas phase formation can affect the engineered barrier system and water flow, which can affect the transport of radionuclides and other soluble contaminants in water. Microbial gas generation is coupled with a wider range of biogeochemical processes that are also relevant to the safety of LILW repositories through effects on pH, Eh and organic complexation. The large scale Gas Generation Experiment (GGE), located at the VLJ repository, Olkiluoto, Finland has been in operation for 18 years to study processes of gas generation from cellulose-containing low-level waste (LLW) from the Olkiluoto power plants. Here we provide an update of the experiment data set that records, over a period of 18 years, the neutralisation of the initial pH 10–11 conditions in the water filled regions of the experiment that were buffered by a concrete container, of relatively small mass, by acidity generated by degradation of cellulose LLW materials. The neutralisation of pH below pH 9 coincides with a doubling of the generation rate of a CH4-rich gas to around 1 m3 per year. Aqueous sulfide is also present at low levels (<3 × 10−6 M) at this time, consistent with equilibrium with mackinawite (FeS). Dissolved organic carbon attained a peak concentration of 8 mM during the early stages of the experiment, prior to the higher gas generation rate, but after 9 years declined. After 18 years the Eh of the tank water measured by a Pt electrode is consistent with that calculated for the S(-2)/S(6) and methanogenesis redox couples suggesting equilibration of redox processes. Carbonate concentration has increased steadily to around 15 mM. After 7 years CO2 gas and aqueous and solid carbonates are also close to equilibrium. The experimental data has been interpreted with the aid of a biogeochemical model that represents the coupled processes of organic waste degradation, pH buffering and microbial gas generation. The model simulates that the majority of the gas is generated by H2 and organic consuming methanogenic processes in the waste drums. The increase in CH4 generation is simulated to be the result of methanogenic processes that consume soluble cellulose degradation products that diffuse into the tank water from the waste drums. It is expected that under the steady state conditions now established, resulting from gas/liquid/solid equilibrium and diffusion processes, that gas generation should continue until the cellulose and steel materials are exhausted. The experimental data and biogeochemical model can be used to predict the rate of CH4-rich gas generation from the VLJ and other repositories with higher proportions of cementitious materials. In addition the study has shed further light on the role of microbial processes in affecting pH buffering of cementitious conditioned LILW.

Temperature Effects in Modeling Solid Waste Biodegradation

Microbial growth models are often used to evaluate anaerobic biodegradation processes and estimate gas generation rates from solid waste decomposition in sanitary landfills. Temperature effects on anaerobic processes have been commonly evaluated in anaerobic digestion studies by deriving mathematical expressions relating media temperature to biokinetic parameters of microbial growth models. Such expressions have not been derived or are rarely used in estimating gas generation rates from solid waste landfills. The first part of this paper presents a review of gas generation-microbial growth modeling techniques applied in simulating biodegradation and gas generation processes in solid waste landfills. The review includes a description of solid waste hydrolysis with temperature effects on hydrolysis rates and biokinetic parameters. The second part of the paper describes the incorporation of kinetic expressions into a gas generation-microbial growth model. Model simulation results were in good agreement with ...

Mathematical modeling of the gas generation process in a coal reaction chamber

A computational mathematical model of the process of gas generation in a reaction coal chamber is developed. The model portrays the coal chamber in the form of conjoined oxygen and deoxidizing sectors.

95/01153 Liptinite in Indonesian tertiary coals

Secondary macropores and mosaic structure, common characteristics in metallurgical and natural cokes, are considered to be the solid residue after the release of liquid and gas during the heating process. In north-central Henan province, People's Republic of China, secondary macropores and “mosaic” structure are found in semi-anthracite and anthracite of lower Permian telemagmatic (not in contact with intrusion) metamorphic coal. Coal rank exhibits a zoned distribution cored by a northwest-southeast trending zone of anthracite. Coal rank decreases from this central zone toward both the northeast and southwest margins from low-volatile bituminous through medium-volatile bituminous to high-volatile bituminous. The zoned rank distribution of coal in this area is interpreted as being the result of regional metamorphism overprinted by telemagmatic metamorphism. Coal metamorphism in this area occurred in three stages: (1) pre-orogenic (late Carboniferous-late Triassic). Regional metamorphism produced coals of subbituminous to high volatile bituminous rank. (2) Orogenic (early Jurassic-late Cretaceous). Telemagmatic metamorphism resulted in zones of higher rank coal (medium-volatile bituminous through anthracite rank). (3) Post-orogenic (Tertiary-Quaternary). Shallow burial depth due to the tectonic uplift followed by erosion had a negligible effect on coal rank. Secondary macropores and “mosaic” structure found in semi-anthracite and anthracite in the research area are similar in form, by microscopic and SEM observation, to those of metallurgical cokes and other natural cokes, indicating extraordinary heating effect on the coal. High temperature, high-pressure experiments on high volatile bituminous coal from the marginal area show that the pores develop in the 250–300°C range and “mosaic” structure develops in the 350–500°C range. It is therefore postulated that the high rank coal in this area may have been subjected to temperatures similar to carbonization temperatures during the orogenic period. Because the heat sources for telemagmatic metamorphism are deep-seated plutons, the rate of heating on this coal might be relatively slow, the time involved in the metamorphism was considerably longer, and the affected area might be extensive. During the heating process, bituminous coal near the center of high heat flow region was heated to a thermoplastic temperature range and coal underwent a soft stage (plastic). Gases evolved in this phase and left the pore system in their wake. Mesophase growth units may also develop in this phase, which could get compressed into each other to form mosaic structure. The existence of secondary macropores and mosaic structure in coal can be used as an indicator of heating effect and gas generation. Ubiquitous macropores developed in the coal in a considerable area indicate that a regional gas-generation process occurred. The gases generated by thermal cracking of the coal during the heating process could be captured later by the macropores, migrate through the network of pores, and form the underground gas reservoirs where the storage conditions are favorable for gas retention. Therefore secondary macropores and mosaic structure in telemagmatic metamorphic coal have potential significance in natural gas exploration.

BHP PETROLEUM&amp;apos;S NEW TECHNOLOGY METHANOL RESEARCH PLANT

BHP Petroleum (BHPP) is in the process of constructing a 164 tonne per day Methanol Research Plant (MRP) on the outskirts of Melbourne. The plant is designed to demonstrate and develop the Leading Concept Methanol (LCM) technology of ICI Katalco. The plant will be the first large scale demonstration of this technology and is part of BHPP's strategy to develop viable options for the development of Australia's uncommitted gas resources. The strategy is to demonstrate and develop the LCM technology onshore and then to apply the technology to an offshore production environment.The LCM technology as applied to the MRP involves a new synthesis gas generation process and other features which result in a compact plant design with low utilities requirements and insensivity to vessel motion effects.Although the MRP is being built primarily for Research and Development (R&amp;D) it has been sized consistent with future scale up to world scale methanol capacity. The plant capacity is sufficient to supply a major share of Australia's methanol demand, particularly that of the immediate vicinity in Victoria.The construction of the plant started in April, 1993 and is currently about 85 per cent complete and on schedule. Final mechanical completion is scheduled for mid 1994 with commissioning in the third quarter. The capital cost of the project is approximately A$70 million.

Deformation of foamed rhyolites under internal and external stresses: an experimental investigation

The style of magma eruption depends strongly on the character of melt degassing and foaming. Depending on the kinetics of these processes the result can be either explosive or effusive volcanism. In this study the kinetics of foaming due to the internal stresses of gas expansion of two types of obsidian have been investigated in time series experiments (2 min-24 h) followed by quenching the samples. The volumetric gas-melt ratio has been estimated through the density measurements of foamed samples. The variation of gas volume (per unit or rhyolite melt volume) with time may be described by superposition of two exponentials responsible for gas generation and gas release processes respectively. An observed difference in foaming style in this study is interpreted as the result of variations in initial contents of microlites that serve as bubble nucleation centers during devolatilization of the melts. Quantitatively the values of the gas generation rate constants (k g) are more than an order of magnitude higher in microlite-rich obsidian than in microlite-free obsidian. Possible origins of differences in the degassing style of natural magmas are discussed in the light of bubble nucleation kinetics in melts during foaming. In a complementary set of experiments the mechanical response of vesicular melt to external shear stress has been determined in a concentric cylinder viscometer. The response of vesicular melt to the pulse of shear deformation depends on the volume fraction of bubbles. The obtained response function can be qualitatively described by a Burgers body model. The experimental shear stress response function for bubble-bearing melt has an overshoot due to the strain-dependent rheology of a twophase liquid with viscously deformable inclusions.

Secondary macropores and mosaic structure in a telemagmatic metamorphosed coal and their significance in exploration for natural gas, Henan, China

Secondary macropores and mosaic structure, common characteristics in metallurgical and natural cokes, are considered to be the solid residue after the release of liquid and gas during the heating process. In north-central Henan province, People's Republic of China, secondary macropores and “mosaic” structure are found in semi-anthracite and anthracite of lower Permian telemagmatic (not in contact with intrusion) metamorphic coal. Coal rank exhibits a zoned distribution cored by a northwest-southeast trending zone of anthracite. Coal rank decreases from this central zone toward both the northeast and southwest margins from low-volatile bituminous through medium-volatile bituminous to high-volatile bituminous. The zoned rank distribution of coal in this area is interpreted as being the result of regional metamorphism overprinted by telemagmatic metamorphism. Coal metamorphism in this area occurred in three stages: (1) pre-orogenic (late Carboniferous-late Triassic). Regional metamorphism produced coals of subbituminous to high volatile bituminous rank. (2) Orogenic (early Jurassic-late Cretaceous). Telemagmatic metamorphism resulted in zones of higher rank coal (medium-volatile bituminous through anthracite rank). (3) Post-orogenic (Tertiary-Quaternary). Shallow burial depth due to the tectonic uplift followed by erosion had a negligible effect on coal rank. Secondary macropores and “mosaic” structure found in semi-anthracite and anthracite in the research area are similar in form, by microscopic and SEM observation, to those of metallurgical cokes and other natural cokes, indicating extraordinary heating effect on the coal. High temperature, high-pressure experiments on high volatile bituminous coal from the marginal area show that the pores develop in the 250–300°C range and “mosaic” structure develops in the 350–500°C range. It is therefore postulated that the high rank coal in this area may have been subjected to temperatures similar to carbonization temperatures during the orogenic period. Because the heat sources for telemagmatic metamorphism are deep-seated plutons, the rate of heating on this coal might be relatively slow, the time involved in the metamorphism was considerably longer, and the affected area might be extensive. During the heating process, bituminous coal near the center of high heat flow region was heated to a thermoplastic temperature range and coal underwent a soft stage (plastic). Gases evolved in this phase and left the pore system in their wake. Mesophase growth units may also develop in this phase, which could get compressed into each other to form mosaic structure. The existence of secondary macropores and mosaic structure in coal can be used as an indicator of heating effect and gas generation. Ubiquitous macropores developed in the coal in a considerable area indicate that a regional gas-generation process occurred. The gases generated by thermal cracking of the coal during the heating process could be captured later by the macropores, migrate through the network of pores, and form the underground gas reservoirs where the storage conditions are favorable for gas retention. Therefore secondary macropores and mosaic structure in telemagmatic metamorphic coal have potential significance in natural gas exploration.

Landfill Gas: From Environment to Energy

A survey was recently achieved, on behalf of the Commission of the European Communities, to scrutinise the state-of-the-art of landfill gas control and exploitation. The survey is divided into 8 parts After an Executive Summary, part I deals with the environmental impact of landfill gas and details 166 reported cases of landfill gas damages in uncontrolled landfills. The second one details the process of landfill gas generation and the technology of landfill gas control by its exploitation. The third part surveys the methodologies for monitoring landfill gas emissions for landfill gas potential evaluation and for safety. The fourth part deals with policies and legal aspects of landfill gas in the European Community and in the World. The fifth part estimates landfill gas potentials and overviews the economics of landfill gas control and exploitation, notably by the exhaustive assessment of 6 case studies. The sixth part gives the status of landfill gas exploitation in the European Community and in the World. The two final parts list utilities and references.

Effects of minerals on Rock Eval pyrolysis of kerogen

To define the effect of common sedimentary minerals on pyrolysis of kerogen, previously separated and purified kerogen concentrates of alginite, amorphous liptinite and vitrinite were mixed with the following minerals: quartz, calcite, pyrite, limonite, kaolinite, bentonite and illite in various kerogen to mineral ratios. Rock Eval pyrolysis of these mixtures which contain 0.5 to 6.6% organic carbon show systematic variations in the parameters; hydrogen index, oxygen index, production index and Tmax and also in the amount of organic carbon consumed during the process. The variations for a given kerogen depend on the type of mineral and its proportion in the mixtures. The results of Rock Eval pyrolysis reflect the effect of the mineral matrix on the pyrolysis process of the sedimentary organic matter and its products. These effects are probably different from those caused by the same mineral during the natural oil and gas generation process. However, these analytical phenomena have to be recognized and accounted for in the interpretation of pyrolysis results.

Absorption parameters of deuterium ions in molybdenum

The capture parameters of deuterium ions in molybdenum have been studied in this paper. It has been shown that the capture coefficients decrease as the dose and the irradiation temperature increase and they increase as the energy and flux density of the ions increases. Upon heating after irradiation or exposure in a vacuum even at room temperature the number of deuterons captured in molybdenum decreases. At a raised temperature the capture coefficients measured from the gas generation spectra with heating after irradiation turn out to be smaller than the coefficients measured from the gas generation right during the irradiation. It has been established in measurements of the spectra of deuterium gas generation that the accumulation of deuterium in molybdenum occurs with a different binding energy of the deuterons in the metal. As the deuterium accumulates in the sample, those sites at which the deuterium is most strongly bound are gradually filled up and saturated. At large doses most of the deuterium is poorly retained in the metal and can be liberated into a vacuum either in the course of irradiation or during the subsequent heating. First of all, the deuterium is liberated most rapidly from the weakly bound states. It has been shown that in addition to thermal gas generation processes there is gas generation stimulated by the ion beam retarded in the sample. The contribution of radiatively stimulated gas generation at a low temperature and a high irradiation dose is especially important. A comparative analysis has been made of the results obtained by different authors, and the possible causes for the discrepancy between the experiments have been explained. It has been shown that the various results can be produced both by a difference in the irradiation parameters (which are sometimes assumed without justification to be unimportant and are not even indicated in the papers) and by a difference in measurement procedures.

DEVELOPMENT OF METHODS FOR THE QUANTITATIVE EVALUATION OF PETROLEUM POTENTIAL IN THE USSR

The paper deals with the history of the development of methods used for the prognostic evaluation of hydrocarbon resources in the USSR, their modern classification, and the calculation techniques involved. Ultimate resources are divided into discovered reserves and predicted resources. The latter are divided into D1 and D2 sub‐groups, according to the presence or absence of production from the formation under evaluation. Prognostic resources include identified and unidentified components. The modern system of forecasting provides a review of adequate information and the determination of requirements for: (i) the quality of prediction; (ii) the creation of theoretical models for oil and gas generation and accumulation processes in the region under evaluation; (iii) the determination of quantitative functional relations as a forecasting tool; (iv) resources estimation using different models; and (v) the correlation of the results obtained and the differentiation of the resources in terms of the efficiency of capital investment required for their development.