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With the development of an energy sector based on renewable primary sources, structural changes are emerging for the entire national energy system. Initially, it was estimated that energy generation based on fossil fuels would decrease until its disappearance. However, the evolution of C O 2 capture capacity leads to a possible coexistence for a certain period with the renewable energy sector. The paper develops this concept of the coexistence of the two systems, with the positioning of green hydrogen not only within the renewable energy sector but also as a transformation vector for carbon dioxide captured in the form of synthetic fuels, such as C H 4 and C H 3 O H . The authors conducted pilot-scale research on C O 2 capture with green H 2 , both for pure (captured) C O 2 and for C O 2 found in combustion gases. The positive results led to the respective recommendation. The research conducted by the authors meets the strict requirements of the current energy phase, with the authors considering that wind and solar energy alone are not sufficient to meet current energy demand. The paper also analyzes the economic aspects related to price differences for energy produced in the two sectors, as well as their interconnection. The technical aspect, as well as the economic aspect, of storage through various other solutions besides hydrogen has been highlighted. The development of the renewable energy sector and its demarcation from the fossil fuel energy sector, even with the transcendent vector represented by green hydrogen, leads to the deepening of dispersion aspects between the electricity sector and the thermal energy sector, a less commonly mentioned aspect in current works, but of great importance. The purpose of this paper is to highlight energy challenges during the current transition period towards climate neutrality, along with solutions proposed by the authors to be implemented in this phase. The current stage of combustion of the C H 4 − H 2 mixture imposes requirements for the capture of the resulting C O 2 . [ABSTRACT FROM AUTHOR]

The expansion of renewable electricity storage technologies, including green hydrogen storage, is spurred by the need to address the high costs associated with hydrogen storage and the imperative to increase storage capacity. The initial section of the paper examines the intricacies of storing electricity generated from renewable sources, particularly during peak periods, through green hydrogen. Two primary challenges arise: firstly, the complexity inherent in the storage technology and its adaptation for electricity reproduction; and secondly, the cost implications throughout the technological chain, resulting in a significant increase in the price of the reproduced energy. Electric energy storage emerges as a pivotal solution to accommodate the growing proportion of renewable energy within contemporary energy systems, which were previously characterized by high stability. During the transition to renewable-based energy systems, optimizing energy storage technology to manage power fluctuations is crucial, considering both initial capital investment and ongoing operational expenses. The economic analysis primarily focuses on scenarios where electricity generated from renewable sources is integrated into existing power grids. The subsequent part of this paper explores the possibility of localizing excess electricity storage within a specific system, illustrated by domestic hot water. [ABSTRACT FROM AUTHOR]

For the modelling of gasification processes, several models have been developed over the years. It is remarked that gasification calculation models of very high complexity entail some complications. Therefore, simpler mathematical representations of gasification characteristics and process behavior are required as a first step in addressing such systems. The preliminary calculation simplicity is needed form two perspectives: First – the pre-sizing of gasification installations, and second – the estimation of experimental or functional results. For this kind of topics, an adequate simplified model should be defined. Further, to validate the results it will be necessary to use complex calculation models. The model proposed in this paper addresses gasification with distributive air in the air distribution current, considering general concurrent flow of air fuel. Previous successful investigations, conducted by the present research team, are taken into account within model definition stages. Thus, the work presented here provides useful advances in the field of mathematical modeling of gasification processes. The originality of the model consists in its easy computational accessibility, which allows the approach of technological optimizations, such as the variation of excess air and fuel composition.

The paper presents an investigation on the conditions for implementing a methanation membrane decarbonator coupled to an energy installation that generates flue gases. The retention of the carbon dioxide content in the flue gases and its conversion to methane is envisaged. For start, low thermal power installations, employing natural gas as main fuel supply, are considered. Internal combustion engines (also working with natural gas fuel) are taken into account for the testing of the carbon dioxide retention process. For this, a classification of the flue gas composition by fuel categories is initially carried out. The decarbonation efficiency is defined and clarifications are made withal regarding the connection between the decarbonation installation and the energy plant. The first practical achievements are also presented, resulting from a decarbonator with a volume of 940 cm3 (having the inner diameter of 12 cm and a height of 50 cm). The results prove that the proposed solution has great potential for practical applications, further research being however necessary. In terms of operating costs (including hydrogen consumption), it is remarked that they can be reduced by exploiting the methane production and eliminating the carbon tax, extending the integration perspective form economic point of view.

The hydrogen is expected to become the energy vector of the future. If for environmental protection this concept it is obvious, the data for the design of hydrogen combustion facilities are still insufficient. This paper discusses the fundamental actions related to the design of a hydrogen burner. Numerical modelling researches using the Ansys-Fluent software has shown the link between the flow velocity in combustible gas jets together with the required air and the combustion rates. Combustion models (both analytical and numerical) allowed finding the optimal ratios between the two specified velocities (combustion and flow) compared to those for methane combustion, correlated also with the classical directions and recommendations for the burner design.

Research was carried out at the experimental installation defined by the 2 MW furnace pilot from the Politehnica University of Bucharest and ICEMENRG institute who was involved for measurements. The purpose of the experimental study is to confirm that the use of a coal with low sulphur content S

The experimental investigations carried out within the present research focus on a simple gasification technology dedicated to biofuels conversion according to the Lurgi procedure. Specifically, an installation with a fixed grill and a homogeneous distribution of the air inlet over the combustion space are considered. In order to provide a thorough background for the experimental research, this paper presents first the challenges related to the air distribution. If for coal gasification the difficulty of the homogeneous penetration of the air inlet within the whole combustion volume is balanced by the possibility of the direct emission of CO valorization, for biomass gasification this factor becomes fundamental. The original contribution of the technology introduced in this paper assumes an improved combustion process for Lurgi-type gas generators. The experimental installation employed has a particular design, enabling a homogeneous distribution of the air inlet over the entire combustion zone, up to the top of the embers layer. This allows achieving a maximum CO2 content in the flue gas flux, effectively reducing it inside the embers bed. The high calorific value of biofuels used favors developing an efficient combustion process, occurring at high temperatures. Thus, the reduction process of the CO2 is self-controlled. The experimental installation operates at a slow fuel rate, with discontinued supply and precise airflow control. The quality of the gas obtained is evaluated based on the resulting open flame, analyzing its composition.

Romania is in a full process of development in regards to producing energy from renewable sources. Successes have been recorded in the wind and hydro sectors, however, challenges are still to be solved in the field of biofuels. In previous years, research and investments targeting facilities that make use of a larger range of renewable fuels and their respective incineration technologies were carried out. The experience thus gained allows for a redefinition of the range of fuels which can constitute cost-worthy power producing solutions. Defining the renewable fuels of the future is of utmost importance for a country with a significant agricultural potential, but also with a temperate climate. After eliminating some cultures specific to warmer climates and not taking into account the quantity/price ratio, the current paper highlights a synthetic approach (a matrix) to the fuels of the future applicable to the power sector in Romania. At the definition base for the matrix also stands data gained from the experience of the researchers in the respective domain.

Solid bio-fuels have the highest and most frequent deficiencies for the efficient use of energy. Besides the humidity, the bulk density, often a consequence of harvesting is the biggest impediment. Appropriate storage is thus essential but also a source of higher investment cost. Processing solid biomass to produce ethanol and methanol, alongside biogas is increasingly a global energy efficiency solution. Agricultural, industrial as well as water purification wastes depend more and more on their transformation into biogas. Energy experience in general has shown that combustion of more than two fuels simultaneously is a high and as a rule, unnecessary effort. The mixture of fuels very rarely contains a mélange of them. Mélange is the easiest way to achieve solid-phase combustion when used in the storage or in the feed stage. The use of vegetable and used (burned) oils in the food and transport industry usually leads to their mixing with liquid hydrocarbons. Mixing in hydrocarbons is also the technology applied to animal fats. Reduced calorific power (LHV) biogas will need to have a thermal support, due to the high CO2 content that presents a low burning rate in combustion. [ABSTRACT FROM AUTHOR]

Solid biomass combustion is characterized by two main issues: fuel high moisture weight (that generates some ignition failures) and the high rate of carbon monoxide from flue-gasses (that diminishes the efficiency of the burner an increases the pollution). Hydrogen injection (with a higher combustion velocity) disables the disadvantages mentioned above, allowing the design and operation of more efficient and less pollutant biomass boilers. The paper enhances the theoretical and experimental issues related to the hydrogen use during solid biomass combustion. [ABSTRACT FROM AUTHOR]

Under environmental legislation, biomass is seen as a zero emitter of carbon dioxide emissions releasing only recently fixed carbon following combustion. Simultaneous combustion of biomass with coal is such an alternative energy with economic potential. Among the many stages that occur during combustion of biomass, combustion of coke (the final solid phase) is most relevant to the issue of alkali metals. The paper analyses the potential corrosion and the formation of adherent deposits in the coal-straws co-combustion process at the pilot installations. The straw (in the form of cylindrical briquettes) burning experiments carried out on 2 MW thermal pilot plant. The results of chemical analysis of ash were presented, compared with those obtained from the singular burning of straws in the burning experimental thermal plant of 55 kW. [ABSTRACT FROM AUTHOR]

The paper presents the results of some experiments of burning biomass and coal mixture in thermal energy boilers. The main purpose is to underline some problems of endurance of boilers burning this mixture, like the corrosion temperature and deterioration of the heat-transfer surfaces of the boilers. Boilers burning biomass and coal mixture are intended to be used in small communities, as a part of a co-generating energy system. Also is presented the principal environmental protection measure when using biomass and coal mixture, the content of noxious burning residues. [ABSTRACT FROM AUTHOR]

Using biomass in combustion, as a renewable source of energy, from ecological and economic considerations, sets special demands for control of the co-firing process. The paper aimed to study the problems like slugging, clogging and ash deposits formed on heat exchange surfaces during the co-firing process of agricultural biomass with coal. There are identifies the main factors that influence the formation of flying ash deposits and corrosion process. Most problems of co-firing process of biomass with coal have their origins in fuels properties. The problems related to the ash management have a strong impact on the life time of heating equipment and environment, therefore has economic and ecological relevance. [ABSTRACT FROM AUTHOR]

The paper examines the effects of high temperature corrosion of the surfaces of heat exchange due to corrosive components formed in the co-combustion of biomass and coal. High temperature corrosion of the surfaces of heat exchange becomes a priority in the combustion of biomass with high chlorine and alkali metals, as alkali chlorides formed deposited on the surfaces of heat transfer, leading to serious consequences for them. Forms of manifestation of corrosion are numerous, the most important being: pitting corrosion (point), inter-granular corrosion, crevice corrosion, selective and uneven. One of the most important limitations to the use of biomass for energy purposes is the increased corrosion of the surfaces of heat exchange. [ABSTRACT FROM AUTHOR]

The paper highlights the combustion possibilities of crude vegetable oils as fuels for stationary application. This is an opportunity of a new utilization in Romania of tee vegetable oils, for electricity production and heating systems, instead of the current situation of using in transportation as biodiesel fuel. The research focuses on crude vegetable oils obtained from some indigenous cultures: rape, soy, sunflower. An overview of the agricultural potential of oleaginous plants is made, the feedstock and the costs being essential in choosing the energy crops sort. The typical properties of some crude vegetable oils are presented, and the first experiments on their ignition conditions are reported. The results of crude sunflower oil combustion in an experimental 55 kW boiler are presented and discussed. [ABSTRACT FROM AUTHOR]