A CFD Study on the Effect of Carbon Particle Seeding for the Improvement of Solar Reactor Performance

2010 ◽  
Author(s):  
Nesrin Ozalp ◽  
Anoop Kanjirakat
Keyword(s):  
Methane Conversion ◽  
Particle Deposition ◽  
Flow Reactor ◽  
Carbon Particle ◽  
Chemical Reactor ◽  
Reactor Performance ◽  
Surface Absorption ◽  
Injection Point ◽  
Carbon Particles ◽  
Production Of Hydrogen

With the increasing concern of CO2 emissions and climate change, efforts have grown to include solar technologies in chemical processes to manufacture products that can be used both as a commodity and as a fuel, such as hydrogen. This study focuses on a technique, referred to as “solar cracking” of natural gas for the co-production of hydrogen and carbon as byproduct with zero emission footprint via the following reaction: CH4→C(s)+2H2(g). However, some portion of the incoming solar energy absorbed by the cavity greatly exceeds the surface absorption of the inner walls because of multiple internal reflections. Studies have shown that by seeding the reactor with micron-sized carbon particles, methane conversion improves drastically due to the radiation absorbed by the carbon particles and additional nucleation sites formed by carbon particles for heterogeneous decomposition reaction. This can maintain more heat at the core and can reduce the carbon deposits on the reactor walls. Present study numerically tries to investigate the above fact by tracking carbon particles in a Lagrangian frame-work. Initially, the numerical model is validated qualitatively by comparing the particle deposition on reactor window with the experimental observations. Effect of particle loading, particle emissivity, injection point location, and effect of using different window screening gases on a flow and temperature distribution inside a confined tornado flow reactor are studied. It is observed that the methane conversion substantially increases by particle seeding. The results of this research can be used in thermo-chemical reactor design.

A Computational Fluid Dynamics Study on the Effect of Carbon Particle Seeding for the Improvement of Solar Reactor Performance

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Nesrin Ozalp ◽  
Anoop Kanjirakat
Keyword(s):  
Flow Reactor ◽  
Carbon Particle ◽  
Decomposition Reaction ◽  
Reactor Performance ◽  
Injection Point ◽  
Carbon Particles ◽  
Solar Reactor ◽  
Lagrangian Framework ◽  
Nucleation Sites ◽  
Window Screening

This study focuses on a technique, referred to as “solar cracking” of natural gas for the coproduction of hydrogen and carbon as byproduct with zero emission footprint. Seeding a solar reactor with micron-sized carbon particles increases the conversion efficiency drastically due to the radiation absorbed by the carbon particles and additional nucleation sites formed by carbon particles for heterogeneous decomposition reaction. The present study numerically tries to investigate the above fact by tracking carbon particles in a Lagrangian framework. The results on the effect of particle loading, particle emissivity, injection point location, and effect of using different window screening gases on a flow and temperature distribution inside a confined tornado flow reactor are presented.

Study on Properties of Carbon Particle Modified Silicon Carbide Composite Ceramics

2011 ◽  
Vol 311-313 ◽  
pp. 276-282 ◽  
Author(s):  
You Jun Lu ◽  
Hong Fang Shen ◽  
Yan Ming Wang
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Carbon Particle ◽  
Composite Ceramics ◽  
Carbon Particles ◽  
High Temperature Mechanical Properties ◽  
Sic Ceramics ◽  
Carbide Composite ◽  
Application Fields ◽  
Different Content

High-temperature mechanical properties, machinability, oxidation resistance and thermal shock resistance of different content of carbon particles modified silicon carbide composite ceramics (Cp/SiC) prepared by pressureless sintering techniques were studied. Adhesion of Cp/SiC to melted glass under 1000°C was also observed. The results showed that 15-Cp/SiC had the optimum machinability and it also did not adhere to melted glass at high temperature. And flexural strength, hardness, and fracture toughness of 15-Cp/SiC is 136.5MPa, 274.6kgf/mm2, 2.58MPa•m1/2 respectively. The good performance of Cp/SiC made it possible to be used as high temperature glass fixture, which means that Cp/SiC can not only improve the service life of fixture materials, but also broaden the application fields of SiC ceramics.

Effect of Carbon Particle Feeding as Radiant Absorbent for Enhanced Heat Transfer

2021 ◽  
pp. 1-15
Author(s):  
Hamed Abedini ◽  
Nesrin Ozalp
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Temperature Profile ◽  
Energy Absorption ◽  
Carbon Particle ◽  
Carbon Particles ◽  
Solar Reactor ◽  
Simulation Results ◽  
Particle Feeding ◽  
Solar Receiver

Abstract Carbon particles can be used as catalyst in solar reactors where they serve as radiant absorbent and nucleation sites for the heterogeneous decomposition reaction. Unlike commonly used metal catalysts, carbon catalyst does not have durability problem and high cost. However, in order to achieve sustainable catalytic decomposition of feedstock over carbon catalysts at elevated temperatures, the surface area of the carbon particles must be maintained. A subsequent treatment of deactivated carbon samples with CO2 at about 1000 °C would increase the surface and would recover the original activity as catalyst. In a windowed solar reactor, carbon particles are directly exposed to the high flux irradiation providing efficient radiation heat transfer directly to the reaction site. Therefore, one of the key parameters to achieve higher conversion efficiencies in a solar reactor is the presence and transport of carbon particles. In this paper, a transient one-dimensional model is presented to describe effect of carbon particle feeding on energy transport and temperature profile of a cavity-type solar receiver. The model was developed by dividing the receiver into several control volumes and formulating energy balance equations for gas phase, particles, and cavity walls within each control volume. Monte Carlo ray tracing (MCRT) method was used to determine the solar heat absorbed by particles and cavity walls, as well as the radiative exchange between particles and cavity walls. Model accuracy was verified by experimental work using a solar receiver where carbon particles were injected uniformly. Comparison of simulation results with the experimentally measured temperatures at three different locations on cavity receiver wall showed an average deviation of 3.81%. The model was then used to study the effect of carbon particle size and feeding rate on the heat transfer, temperature profile, and energy absorption of the solar receiver. Based on the simulation results, it was found that injection of carbon particles with a size bigger than 500 µm has no significant influence on heat transfer of the system. However, by reducing the particle size lower than 500 µm, temperature uniformity and energy absorption were enhanced.

Carbon Particle Generation and Preliminary Small Particle Heat Exchange Receiver Lab Scale Testing

2013 ◽  
Author(s):  
Lee Frederickson ◽  
Kyle Kitzmiller ◽  
Fletcher Miller
Keyword(s):  
High Temperature ◽  
Heat Exchange ◽  
Natural Gas ◽  
Small Particle ◽  
Carbon Particle ◽  
Solar Flux ◽  
Gas Mixture ◽  
Solar Simulator ◽  
Spherical Cap ◽  
Carbon Particles

High temperature central receivers are on the forefront of concentrating solar power research. Current receivers use liquid cooling and power steam cycles, but new receivers are being designed to power gas turbine engines within a power cycle while operating at a high efficiency. To address this, a lab-scale Small Particle Heat Exchange Receiver (SPHER), a high temperature solar receiver, was built and is currently undergoing testing at the San Diego State University’s (SDSU) Combustion and Solar Energy Laboratory. The final goal is to design, build, and test a full-scale SPHER that can absorb 5 MWth and eventually be used within a Brayton cycle. The SPHER utilizes air mixed with carbon particles generated in the Carbon Particle Generator (CPG) as an absorption medium for the concentrated solar flux. Natural gas and nitrogen are sent to the CPG where the natural gas undergoes pyrolysis to carbon particles and nitrogen is used as the carrier gas. The resulting particle-gas mixture flows out of the vessel and is met with dilution air, which flows to the SPHER. The lab-scale SPHER is an insulated steel vessel with a spherical cap quartz window. For simulating on-sun testing, a solar flux is produced by a solar simulator, which consists of a 15kWe xenon arc lamp, situated vertically, and an ellipsoidal reflector to obtain a focus at the plane of the receiver window. The solar simulator has been shown to produce an output of about 3.25 kWth within a 10 cm diameter aperture. Inside of the SPHER, the carbon particles in the inlet particle-gas mixture absorb radiation from the solar flux. The carbon particles heat the air and eventually oxidize to carbon dioxide, resulting in a clear outlet fluid stream. Since testing was initiated, there have been several changes to the system as we have learned more about the operation. A new extinction tube was designed and built to obtain more accurate mass loading data. Piping and insulation for the CPG and SPHER were improved based on observations between testing periods. The window flange and seal have been redesigned to incorporate window film cooling. These improvements have been made in order to achieve the lab scale SPHER design objective gas outlet flow of 650°C at 5 bar.

Modeling the Formation of Pollutant Emissions in Large-Bore, Lean-Burn Gas Engines

2017 ◽  
Author(s):  
Anamol Pundle ◽  
David G. Nicol ◽  
Philip C. Malte ◽  
Joel D. Hiltner
Keyword(s):  
Partial Oxidation ◽  
Flow Reactor ◽  
Batch Reactor ◽  
Plug Flow ◽  
Chemical Reactor ◽  
Chemical Kinetic ◽  
Pollutant Emissions ◽  
Lean Burn ◽  
Reciprocating Engines ◽  
Stroke Engine

This paper discusses chemical kinetic modeling used to analyze the formation of pollutant emissions in large-bore, lean-burn gas reciprocating engines. Pollutants considered are NOx, CO, HCHO, and UHC. A quasi-dimensional model, built as a chemical reactor network (CRN), is described. In this model, the flame front is treated as a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR), and reaction in the burnt gas is modeled assuming a batch reactor of constant-pressure and fixed-mass for each crank angle increment. The model treats full chemical kinetics. Engine heat loss is treated by incorporating the Woschni model into the CRN. The mass burn rate is selected so that the modeled cylinder pressure matches the experiment pressure trace. Originally, the model was developed for large, low speed, two-stoke, lean-burn engines. However, recently, the model has been formatted for the four-stroke, open-chamber, lean-burn engine. The focus of this paper is the application of the model to a four-stroke engine. This is a single-cylinder non-production variant of a heavy duty lean-burn engine of about 5 liters cylinder displacement Engine speed is 1500 RPM. Key findings of this work are the following. 1) Modeled NOx and CO are found to agree closely with emission measurements for this engine over a range of relative air-fuel ratios tested. 2) This modeling shows the importance of including N2O chemistry in the NOx calculation. For λ = 1.7, the model indicates that about 30% of the NOx emitted is formed by the N2O mechanism, with the balance from the Zeldovich mechanism. 3) The modeling shows that the CO and HCHO emissions arise from partial oxidation late in the expansion stroke as unburned charge remaining mixes into the burnt gas. 4) Model generated plots of HCHO versus CH4 emission for the four-stroke engine are in agreement with field data for large-bore, lean-burn, gas reciprocating engines. Also, recent engine tests show the correlation of UHC and CO emissions to crevice volume. These tests suggest that HCHO emissions also are affected by crevice flows through partial oxidation of UHC late in the expansion stroke.

Investigation on the Combustion Rate of Carbon Particle in Pressurized Oxygen-Enriched Conditions

2011 ◽  
Vol 354-355 ◽  
pp. 380-384
Author(s):  
Chun Bo Wang ◽  
Jin Gui Sheng ◽  
Ming Lei ◽  
Jian Guo Wei ◽  
Xiao Fei Ma
Keyword(s):  
Particle Size ◽  
Combustion Rate ◽  
Carbon Particle ◽  
Enriched Environment ◽  
Carbon Particles

The combustion rates of carbon particle in pressurized oxygen-enriched environment were studied. The combustion rates of different diameter carbon particles were calculated in atmospheric as well as pressurized oxygen-enriched conditions. The effects of pressure and particle size on combustion rate of carbon particle were investigated. It shows that the combustion rate of carbon particle rise with the increase of the pressures in pressurized oxygen-enriched and pressurized air conditions. But, the combustion rate of carbon particle change little at higher pressure. When particle size increased from 50μm to 100μm，the combustion rate of carbon particle rising. When the particle size increased to 150μm, the combustion rate of carbon particle changed little.

Effect of Fuel Staged Proportion on NOX Emission Performance of Centrally Staged Combustor

2013 ◽  
Author(s):  
Fuqiang Liu ◽  
Yong Mu ◽  
Cunxi Liu ◽  
Jinhu Yang ◽  
Yanhui Mao ◽  
...  
Keyword(s):  
Equivalence Ratio ◽  
Flow Reactor ◽  
Flame Temperature ◽  
Plug Flow ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Nox Emission ◽  
Wide Range ◽  
Pilot Fuel ◽  
Pollution Emissions

The low NOX emission technology has become an important feature of advanced aviation engine. A wide range of applications attempt to take advantage of the fact that staged combustion operating under lean-premixed-prevaporized (LPP) conditions can significantly decrease pollution emissions and improve combustion efficiency. In this paper a scheme with fuel centrally staged and multi-point injection is proposed. The mixing of fuel and air is improved, and the flame temperature is typically low in combustion zone, minimizing the formation of nitrogen oxides (NOX), especially thermal NOX. In terms of the field distribution of equivalence ratio and temperature obtained from Computational Fluid Dynamics (CFD), a chemical reactor network (CRN), including several different ideal reactor, namely perfectly stirred reactor (PSR) and plug flow reactor (PFR), is constructed to simulate the combustion process. The influences of the pilot equivalence ratio and percentage of pilot/main fuel on NOX and carbon monoxide (CO) emissions were studied by Chemical CRN model. Then the NOX emission in the staged combustor was researched experimentally. The effects of the amount of pilot fuel and primary fuel on pollution emissions were obtained by using gas analyzer. Finally, the effects of pilot fuel proportion on NOX emission were discussed in detail by comparing predicts of CRN and experimental results.

Sign in / Sign up

Export Citation Format

Share Document