Reactor For Thermal Decomposition Research Articles

Additive manufacturing of ceramic single and multi-material components–A groundbreaking innovation for space applications too?

The main advantages of ceramic materials are their excellent thermal, chemical, and mechanical properties. They also have a much lower density than metals, making them ideal for lightweight construction, which can also be interesting for space components. However, ceramics have not been widely used due to their low ductility and the challenges of mechanical processing using conventional methods like milling and turning. Additionally, integrating different functions into a single component has been limited.The introduction of additive manufacturing (AM) technologies has revolutionized this field. It is now possible to manufacture highly complex ceramic components with unprecedented functionality. By hybridizing different manufacturing technologies and materials, additional functions such as electrical contacts, sensors, and actuators can be directly integrated, leading to improved manufacturing costs and component properties.Three different demonstrator examples are presented in this paper to give a first impression of what will be possible in the field of space applications in the future. These examples are a ceramic igniter, a ceramic reactor for thermal decomposition of H2O2, and a ceramic aerospike engine.

태양열 이용 바이오메탄 분해 해석연구

In this study, the optical properties, heat transfer capabilities and chemical reaction performance of a methane thermal decomposition reactor using solar heat as a heat source were numerically analyzed on the basis of the cavity shape. The optical properties were analyzed using TracePro, a Monte Carlo ray tracing-based program, and the heat transfer analysis was performed using Fluent, a CFD program. An indirect heating tubular reactor was rotated at a constant speed to prevent damage by the heat source in the solar furnace. The inside of the reactor was filled with a porous catalyst for methane decomposition, and the outside was insulated to reduce heat loss. The performance of the reactor, based on cavity shape, was calculated when solar heat was concentrated on the reactor surface and methane was supplied into the reactor in an environment with a solar irradiance of 700 W/㎡, a wind speed of 1 m/s, and an outdoor temperature of 25°C. Thus, it was confirmed that the heat loss of the full-cavity model decreased to 13% and the methane conversion rate increased by 33.5% when compared to the semi-cavity model.

Metal sulfide-based process analysis for hydrogen generation from hydrogen sulfide conversion

Fossil fuel power plants often generate sulfur species such as hydrogen sulfide or sulfur dioxide due to the sulfur content of the raw feedstocks. To combat the associated environmental, processing, and corrosion issues, facilities commonly utilize a Claus process to convert hydrogen sulfide (H2S) to elemental sulfur. Unfortunately, the potential for H2 production from H2S is lost in the Claus process. In this study, two chemical looping process configurations utilizing metal sulfides as chemical intermediates for sulfur recovery are investigated: (1) sulfur recovery (SR) system for sulfur production; (2) sulfur and hydrogen (H2) recovery (SHR) system for sulfur and H2 and production utilizing staged H2 separation. Since, H2 yield and sulfur recovery in a single thermal decomposition reactor is limited by low H2S equilibrium conversion, a staged H2 separation approach is used to increase H2S conversion to H2 using the SHR system. Steady-state simulations and optimization of process conditions are conducted in Aspen Plus (v10) simulation software for the chemical looping process configurations and the Claus process. An energy and exergy analysis are done for the Claus and chemical looping processes to demonstrate the relative contribution to exergy destruction from different unit operations as well as overall exergy and energy efficiency. The two chemical looping process configurations are compared against the conventional Claus process for similar sulfur recovery in a 629 MWe integrated gasification combined cycle power plant. The SHR system is found to be the most efficient option due to a 97.11% exergy efficiency with 99.31% H2 recovery. The overall energy and exergy efficiencies of this chemical looping system are 14.74% and 21.54% points higher than the Claus process, respectively, suggesting more efficient use of total input energy.

A Low Energy Aqueous Ammonia CO2 Capture Process

Abstract The most pressing challenges regarding the use of ammonia for CO 2 capture are the precipitation limitation and the energy penalty of solvent regeneration. Precipitation-free operation is a vital task since solids may cause the shutdown of the plant. Precipitation and slurry formation can be avoided by increasing temperature and L/G ratio but this leads to higher heat consumption, jeopardizing the economic feasibility. Here we developed, investigated, and optimized a novel CO 2 capture process design using aqueous ammonia as solvent. The proposed configuration replaces the traditional stripper for solvent based CO 2 capture with a thermal decomposition reactor. The overall energy penalty is reduced at the expense of introducing a solid handling section which consists of a saturation reactor, a crystallizer and a belt filter. The feasibility of the present approach is demonstrated by simulation. Flow-sheet calculations are performed in Aspen Plus using the extended UNIQUAC thermodynamic model for vapor-liquid-solid equilibria and for thermal properties calculation of the CO 2 -NH3-H2O system. The simulation results show that the specific regeneration duty of the novel capture alternative is comparable with existing aqueous ammonia CO 2 capture processes. Moreover, the thermal reactor can operate at 1 bar and 86 °C, therefore the NH3 regeneration temperature is reduced by approximately 50 °C. The integration of low- and mid- temperature waste heat becomes possible which can greatly improve the economics of the process. The present capture alternative is especially convenient for power plants but is also beneficial for the cement, steel and aluminum industry. Special attention is given to the ammonia slip prediction. The calculations substantiate that the slip above the absorber is 0.1 mol % after washing with the rich solution and it reduces below 100 ppm by washing with low temperature water.

FORMATION OF CARBON NANOTUBES ON CARBON PAPER AND STAINLESS STEEL SCREEN BY OHMICALLY HEATING CATALYTIC SITES

A newly designed gas phase thermal decomposition reactor, ohmically heating the catalytic sites, has been used to synthesize multiwall carbon nanotubes (MWCNTs) on carbon paper and stainless steel screen. Co-Ni catalyst particles were dispersed by a silane intermediate layer adsorbed onto the carbon fibers or the stainless steel threads of the supports. MWCNTs were obtained on both substrates by a tip grown mechanism. They are about 20 μm in length and 15–50 nm in diameter. A methanol pretreatment of the carbon fibers significantly increased the density of the tubes on the carbon paper, but the same treatment had a negative effect on stainless steel. The MWCNTs, which adhere firmly to the carbon paper and the stainless steel screen, may find applications as electrodes in fuel cells, sensors and in photonics.

Applicability of a double-membrane reactor for thermal decomposition of water: a computer analysis

A theoretical study of applicability of double-membrane reactor for direct thermal decomposition of water is presented. The analysis is based on an isothermal, steady state, plug flow reactor model. One of the two membranes was supposed to be hydrogen permeable, and the other one, oxygen permeable. The simulations were performed for T=2000 K, it being the upper limit of temperatures of practical interest. With a high vacuum in separation zones, the double-membrane configuration theoretically enables complete conversion providing high values of Damkohler number and total rate ratio. When a sweep gas is introduced into separation zones, significant water conversions can also be provided by a countercurrent single membrane reactor, but considerably lower than those obtained in a double-membrane reactor. The double-membrane reactor seems to be a promising solution for the water splitting reaction, deserving experimental investigations.

Observations of chemical effects accompanying pulverized coal thermal decomposition

A thermal decomposition reactor is used to simulate the environment of a practical coal burner and assess the influence of fuel properties on the chemical behaviour that accompanies the thermal decomposition of pulverized coal particles. The present study complements and extends previous work that explored the physical and thermal behaviour. The rate of component burnout is determined for hydrogen, nitrogen and carbon as well as the evolution of NO and HCN, and the efficiency of fuel nitrogen conversion. The results demonstrate a significant dependency on coal particle size and coal type. Modelling demonstrates that the penetration of oxygen into the fuel-rich devolatilization cloud depends on particle size and coal properties and, as a result, controls to a large extent the evolution and transformation of the chemical constituents associated with the parent fuel.