Determining the dynamics of carbon monoxide formation during gas welding processes

This paper reports a study of the air medium where welding processes take place, with special attention paid to the evolution of carbon monoxide (CO) in the working medium in the process of gas welding. Plots were constructed and polynomial dependences were obtained to show a change in the concentration of carbon monoxide in the air of the working area during gas welding. It was confirmed experimentally that the concentration of carbon monoxide exceeds the permissible sanitary and hygienic indicators MPC (20 mg/m3) during gas welding. As a result of the experiment, the effectiveness of the use of an additional device was proven, namely an umbrella gas concentrator, in order to capture welding gases that are formed during gas welding. It was established that the MPC is exceeded under certain working conditions and welding wire. The carbon monoxide formation during gas welding was analyzed; these processes were compared with electric arc welding. The mathematical dependences derived make it possible to assess the risks of the welders’ work and conclude that the electric arc welding is characterized by a much higher rate of CO evolution from the beginning of the welding process (8.5 mg/s), that speed then decreases over 20 s by 2 times (to 4.5 mg/s). In 90 s, the speed becomes constant, to 2 mg/s. In comparison, gas welding has almost the same rate of CO formation, namely 0.3–0.9 mg/s. By changing the types of welding wires used in gas welding and taking into consideration the type of material that needs to be welded (including the period of its use), it is possible to influence the volume of CO emissions entering the working area and an employee’s respiratory area

Carbon monoxide formation as an intermediate product in photocatalytic steam reforming of methane with lanthanum-doped sodium tantalate

Photocatalytic steam reforming of methane (PSRM) has been studied as an attractive method to produce hydrogen by utilizing photoenergy like solar energy around room temperature with metal-loaded photocatalysts, where methane...

Development of a Loss Method for Energy and Exergy Audit of Condensing Hot Water Boilers

Condensing boilers are used in commercial and residential buildings extensively. In this paper, a loss method is proposed to estimate the energy and exergy efficiencies of condensing hot water boilers. The presented method is based on the development of the method presented in ASME PTC 4.1. Energy loss terms consist of exhaust flue gas, carbon monoxide formation, radiation, and condensate outflow sensible heat. Exergy loss terms also include radiation losses, physical exergy of the exhaust flue gas, chemical exergy of the exhaust flue gas, increase in the chemical exergy of the flue gas due to carbon monoxide formation, condensate outflow exergy, boiler exergy destruction, and economizer exergy destruction. Energy and exergy efficiencies are calculated by estimation of these loss terms. To depict the method 's capability and compare results with the direct method, an experimental setup was designed and constructed. Results of energy and exergy audition of the boiler by applying the loss method are compared with the direct method. The results show that, although the condensing economizer improves energy efficiency, it does not improve the exergy efficiency significantly. The energy and exergy efficiencies were calculated 98.65 and 5.14 percent, respectively.

Determination of the Conditions for Carbon Materials Oxidation with Carbon Monoxide Formation at High Temperatures

In this paper, the influence of carbon material type, temperature and oxygen concentration in gas mixture on the processes of carbon monoxide formation in production of the electrodes by graphitization was explored experimentally. Specific quantity of gas formed for a definite time, reduced to mass unit of carbon loading using pitch, packing materials and charge mixture of industrial use, was calculated. It is demonstrated that pitch provides the highest rate of carbon oxidation with the release of CO and substantially exceeds packing materials and charge mixture for this index.

DEVELOPMENT OF ENERGY-EFFICIENT AND ENVIRONMENTALLY FRIENDLY LININGS AND THERMAL INSULATION OF ELECTRODE PRODUCTION FURNACES

A numerical analysis of the thermoelectric state of the Acheson furnace was performed and the use of new thermal insulation of blanks that are graphitized was proposed. The expediency of using a single-component heat-insulating charge as thermal insulation is shown. In this case, in comparison with the use of a traditional multicomponent synthetic mixture, not only a decrease in the temperature of the blanks is observed, but also a significant equalization of temperature along the axis of the blanks. Based on the results of measuring the thermophysical properties and numerical simulation of temperature fields in the volume of the Acheson graphitizing furnace, a resource-saving and environmentally efficient carbon heat-insulating mixture was selected, which consists of raw and graphite coke grains 50/50 % (wt.) up to 2 mm in size. Theoretical and experimental studies of the ecological state of kilns and graphitizing furnaces have been carried out. Based on the analysis of the obtained experimental data, the temperature and time dependences of the concentration of carbon monoxide in kilns and graphitizing furnaces are established. The main sources of carbon monoxide formation are determined: under-oxidized carbon materials, aromatic and resinous substances of binder preforms. A set of measures has been developed that can reduce the concentration of carbon monoxide emissions from furnace equipment in industrial conditions. Experimental studies were carried out to determine the temperature dependence of the concentration of carbon monoxide during heating of a multicomponent and one-component heat-insulating charge, which made it possible to establish a reduction in CO emissions by more than 20 % in the case of using the proposed one-component charge. Bibl. 17, Fig. 9, Tab. 3.

Integrating CO2 capture with electrochemical conversion using amine based capture solvents as electrolytes

Carbon dioxide (CO2) is currently considered as a waste material due to its negative impact on the environment. However, it is possible to create value from CO2 by capturing and utilizing it as a building block for commodity chemicals. Electrochemical conversion of CO2 has excellent potential for reducing greenhouse gas emissions and reaching zero net emissions by 2050. To date, Carbon Capture and Utilization (CCU) technologies have been studied independently. We report a novel methodology based on the integration of CO2 capture and conversion by the direct utilization of a CO2 capture media as electrolyte for electrochemical CO2 conversion. This has a high potential for reducing capital and operational cost when compared to traditional methodologies. A novel mixture of chemical and physical absorption solvents allowed for the captured CO2 to be converted to formic acid with faradaic efficiencies up to 50 % and with carbon conversion of ca. 30 %. By increasing the temperature in the electrochemical reactor from 20 °C to 75 °C, the productivity towards formic acid increased by a factor of 10, reaching up to 0.7 mmol∙m-2·s-1. The direct conversion of captured CO2 was also demonstrated for carbon monoxide formation with faradaic efficiencies up 45 %.

Carbon monoxide formation from trimethylamine-boranecarboxylate: DFT studies of SNi and chelotropic mechanisms

According to a DFT model, CO is formed from trimethylamine boranecarboxylate, a carbon monoxide releasing molecular pro-drug (CORM), via initial SNi subsitution followed by chelotropic fragmentation of the resulting cyclic carboxyborane anion.