V. V. Kireenkov

Use of syngas as an auto fuel additive: State of the art and prospects

A method for the production of a hydrogen-rich gas on board a vehicle was suggested and driving- and bench-tested for application in studies on energy-efficient internal combustion engines with minimum CO, CO2, CH, and NOx emissions. The generated gas is further added to the main fuel fed to the engine. Catalysts for hydrocarbon fuel conversion to syngas were developed. A compact on-board syngas generator mounted under the motor hood and a generator control system adapted to the engine control system were designed. It was shown experimentally that the suggested solution allows a reduction of 13–40% in the fuel rate depending on the operating mode under the urban cycle conditions and considerably decreases the release of CO, CO2, and NOx. Prospects for the applications of this technology for creating ecologically clean engines were assessed.

Thermochemical conversion of fuels into hydrogen-containing gas using recuperative heat of internal combustion engines

The problem of the thermochemical recuperation of heat from the exhaust gases of internal combustion engines (ICEs) as a method of increasing of the efficiency of fuels has been considered. The thermodynamic analysis of thermochemical recuperation conditions was performed, and maximum efficiency conditions were determined. Catalysts for the steam conversion of oxygen-containing fuels into syngas were developed, and the Co-Mn/Al2O3 catalyst was shown to be the most promising. The model of a thermochemical heat recuperation system was developed and manufactured, and its bench tests in the conversion of alcohols were performed using the simulated exhaust gases from a heating device. Mathematical models for calculating units of the heat recuperation system were developed. A recuperation system was manufactured and tested in the ICE-free and ICE-integrated variants. Based on the test results, the equivalent fuel consumption characteristics of a recuperative ICE was revealed to decrease by 11–22% depending on its load with a decrease in the concentration of hazardous emissions by 8–12 times for CO, 2–3.5 times for CH, and 18–25 times for NOx.

Catalysts for the Conversion of Hydrocarbon and Synthetic Fuels for Onboard Syngas Generators

The use of syngas derived on board a vehicle as a supplement to the main fuel fed to engines ensures engine operation using dilute fuel mixtures. This leads to a decrease in emission toxicity and an increase in the fuel efficiency of the engine. The preparation of new types of efficient catalysts for the conversion of hydrocarbon and synthetic fuels for onboard syngas generators requires the use of new approaches to the design of catalysts not only as catalytically active material, but also as a structural component of a chemical reactor. We prepared and tested a set of catalysts for the conversion of hydrocarbons, i.e., natural gas, diesel and biodiesel fuels, biofuels, and alcohols (ethanol, methanol) to syngas. Primary supports for the catalysts were metals grids and porous tapes; secondary supports were oxides of aluminum and magnesium deposited on or sintered to a primary support. The catalysts exhibited high thermal stability and mechanical strength, and were characterized by the conformity of the coefficients of thermal expansion of the support material and the catalytically active bed. The catalysts can be used as structural components of reactors and as a basis for the preparation of monolithic blocks and planar components of radial and planar reactors. The developed catalysts were subjected to laboratory and bench tests and examined as components of onboard generators of vehicles.

Catalytic external combustion engine

The operating regimes of a laboratory external combustion engine consisting of a catalytic heater, working cylinder, connection unit with hydroresistance, back pressure unit, and thermochemical recuperator have been studied. An experimental technique that provides an estimate of the power developed by an engine to perform mechanical work has been created. It has been shown that the efficiency can be increased by recuperating the heat of combustion products from the endothermic reaction of the steam that reforms the initial fuel, e.g., propane–butane, into syngas. The effect of the process parameters on an increase in the inner engine efficiency is analyzed. It has been shown that the maximum pressure in the working cylinder has the greatest effect on an increase in the inner efficiency.

Development of a Catalytic Heating System for External Combustion Engines

A catalytic heater design was proposed for an external combustion engine. This design is based on the partial oxidation or autothermal conversion of hydrocarbon fuel to syngas and its further oxidation with heat generation in a radial catalytic reactor integrated with a tubular heat exchanger. The theoretical analysis of operational regimes for a catalytic heater with a thermal power of 25–50 kW was performed with regard to the distribution of gas and the mathematical modeling of processes in a catalyst bed integrated with a heat exchanger, and some estimates were given for the performance of an external combustion engine. The conditions providing a uniform distribution of gas along the length of a radial reactor with suction of a reaction mixture into the catalyst bed were determined. A design of catalytic heating system elements was developed, and some layout solutions that provide a rational mutual arrangement of system components were created.

Experimental Study of the Temperature Rise in the Frontal Layer of a Structured Porous Metal Catalyst in Air Conversion of Methane

Heat-resistant Ni/MgO block catalysts have been developed on porous nickel carriers for the air conversion of natural gas to synthesis gas. The catalysts were tested under normal pressure, which allowed one to select of a number of samples that demonstrate relatively the low temperature of the frontal layer of the catalytic block of 880–940°C at the inlet temperature of the mixture of 20°C and excess air factor of 0.3. The composition of the mixture at the outlet remained close to thermodynamic equilibrium at a volumetric flow rate of up to 49 000 h–1. It was experimentally established that the temperature of the frontal layer decreases with increasing pressure (2–6 atm), an increase in the frontal layer temperature with an increasing coefficient of excess air (0.31–0.42) and the rate of the inlet mixture (0.30–0.74 m/s). This made it possible to obtain approximate estimates of the areas of exothermic and endothermic reaction stages taking into account external diffusion inhibition based on the analysis of the heat balance equation for the frontal layer of the catalyst.

Experimental and theoretical study of associated petroleum gas processing into normalized gas by soft steam reforming

The article presents the results of experimental investigation and mathematical modeling of a new technology for converting associated petroleum gas to a normalized combustible gas that can be used in gas turbine and gas reciprocator power plants or, after removing part of the СО2, can be pipelined. The essence of the new technology is that the C2+ hydrocarbons contained in associated petroleum gas are converted by soft steam reforming into a gaseous fuel that consists mainly of methane and contains carbon dioxide and a small amount of hydrogen. This process increases the volume of the gas mixture and normalizes its heating value and Wobbe index to the standard characteristics of commercial natural gas (purified from СО2). The soft steam reforming technology has been tested on laboratory, pilot, and pre-commercial scales. A mathematical model has been developed for the process. A numerical analysis based on this model has demonstrated that, using this technology, it is possible to process associated petroleum gases varying widely in methane homologue concentrations in one tubular catalytic reactor.

Effect of the nonuniformity of the inlet liquid distribution on the trickle-bed reactor output in an exothermic reaction accompanied by evaporation

The effect of the inlet liquid distribution on the operation of a trickle-bed reactor is experimentally investigated, and the observed phenomena are analyzed using a one-dimensional mathematical model with nonequilibrium approaches to describing phase transitions. The modeling shows that, if the fraction of the wetted surface at the reactor inlet is below unity, then, along a sufficiently long bed, there is always a stationary front of complete evaporation and complete conversion. The main conclusion within the framework of the considered one-dimensional model with separate evaporation (on completely wetted granules) and gas-phase hydrogenation (on dry granules) is that safe operation (the absence of a thermal explosion) can be ensured by complete suppression of the reaction in the gas phase.

Mathematical Modeling of Methane Air Conversion on a Structured Porous Metal Catalyst

A one-dimensional two-phase mathematical model of an ideal plug-flow reactor for methane air conversion on a Ni–MgO monolith catalyst on porous nickel was proposed. The model describes the methane air conversion as the result of three simultaneous reaction stages: methane deep oxidation, methane steam reforming, and reverse shift reaction. The effect of the external gas–solid mass transfer is taken into account in two variants: (i) independent diffusion and (ii) multicomponent diffusion for all mixture components. The results of modeling were used to analyze the experimental data (obtained in our previous work) on the dependence of the temperature of the front layer of the catalyst on the pressure and excess air coefficient. The best agreement between the calculation and experiment was obtained under conditions of complete external diffusion control of the exothermic stage for oxygen and the transition (between the kinetic and external diffusion) region of the endothermic stage, the kinetic effect of the endothermic stage being further limited by internal pore-diffusion resistance of the rate of this stage for methane.