A Strategy of Reactant Mixing in Methane Direct-Fired sCO2 Combustors

2018 ◽  
Author(s):  
K. R. V. Manikantachari ◽  
Scott Martin ◽  
Ladislav Vesely ◽  
Jose O. Bobren-Diaz ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Power Generation ◽  
Flow Reactor ◽  
Plug Flow ◽  
Kinetic Mechanism ◽  
Operating Conditions ◽  
Lean Burn ◽  
Initial Portion ◽  
Cross Sectional ◽  
Power Cycles ◽  
Stirred Reactor

The sCO2 power cycle concept is identified as a potentially efficient, economical, and pollutant free power generation technique for future power generation. Recent work in the literature provides some strategies and best operating conditions for direct-fired sCO2 combustors based on zero-dimensional reactor modeling analysis, however there is a need for a detailed investigation using accurate combustion chemical kinetics and thermophysical models. Here, the sCO2 combustor is modelled by coupling perfectly stirred reactor (PSR) and plug flow reactor (PFR) models. The real gas effects are incorporated using the Soave-Redlich-Kwong (SRK) equation of state. Also, the detailed Aramco 2.0 kinetic mechanism is used for the combustion kinetic rates. It is found that the primary zone must be diluted either with thirty or forty-five percent of the total CO2 in the cycle to have a feasible combustor design. However, the forty-five percent dilution level at 950 K and 1000 K yielded a better consumption of CO, O2 and CH4. Also, the cross-sectional area of the sCO2 combustor can be scaled-down to 10 to 20 times smaller than a traditional combustor with the same power output. Further, from this investigation, it is also recommended to have a gradually increasing secondary dilution in the dilution zone, by using progressively larger diameter holes. This design would help retain relatively high temperature in the initial portion of the dilution zone and would help consume fuel species such as, CO and CH4. It appears that, for sCO2 combustors “lean burn” is the better strategy over stoichiometric burning to eliminate CO build up at the combustor exit. The lean burn condition at equivalence ratio (ϕ) equal to 0.9 is recommended for sCO2 combustor operation. Also, the length of the dilution zone can be scaled-down to 50% by lean burn operation of the combustor. It is also observed that the lean burn increases the net turbine power. Current work provides crucial design considerations for the development of advanced sCO2 combustors to be used with direct-fired power cycles.

A Strategy of Mixture Preparation for Methane Direct-Fired sCO2 Combustors

2018 ◽  
Author(s):  
K. R. V. Manikantachari ◽  
Scott Martin ◽  
Ladislav Vesely ◽  
Jose O. Bobren-Diaz ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Residence Time ◽  
Flow Reactor ◽  
Plug Flow ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Time Requirement ◽  
Stirred Reactor ◽  
Primary Zone ◽  
Real Gas Effects ◽  
Time Required

The reactor residence time required for a sCO2 combustor is comparatively higher than an equal power, airdiluted conventional combustor. Therefore, the strategies to reduce the reactor residence time are very important in the design of sCO2 combustors. The current work recommends a method to reduce the residence time requirement in the sCO2 combustion chamber. Here, the combustor is modelled by coupling the perfectly-stirred-reactor (PSR) and plug-flow-reactor (PFR) models along with the detailed Aramco 2.0 combustion chemical kinetic mechanism. The real gas effects are considered by using the Soave-Redlich-Kwong (SRK) equation of state incorporated in CHMEKIN-RG. Though, the CO emission level at the exit of the primary zone of the sCO2 combustor is lower or in some cases equal to the conventional combustor, the further decline of CO in the dilution zone is identified as very poor. Therefore, very high CO levels can be expected at the exit of the sCO2 combustor compared to conventional combustors. CO from the sCO2 combustor exhaust can be eliminated by lean operation of the combustor and the excess O2 retained in the re-cycled CO2 stream due to lean operation can be mixed with primary methane before entering the primary combustion zone. This strategy is shown to reduce the primary zone residence time requirement of sCO2 combustion. However, the minimum level of O2 in the re-cycled CO2 stream is approximately 5000 ppm and the minimum required residence time in this pre-mixing chamber is around 4 ms. Also, it is observed that the primary zone residence time requirement decreases linearly with respect to the O2 level in the re-cycled CO2 stream.

scholarly journals Oscillatory flow reactors for synthetic chemistry applications

2020 ◽  
Vol 10 (3) ◽  
pp. 475-490 ◽  
Author(s):  
Pauline Bianchi ◽  
Jason D. Williams ◽  
C. Oliver Kappe
Keyword(s):  
Mass Transfer ◽  
Oscillatory Flow ◽  
Flow Reactor ◽  
Plug Flow ◽  
Operating Conditions ◽  
Solid Particles ◽  
Flow Reactors ◽  
Liquid Systems ◽  
Suspend Solid ◽  
Biphasic Systems

Abstract Oscillatory flow reactors (OFRs) superimpose an oscillatory flow to the net movement through a flow reactor. OFRs have been engineered to enable improved mixing, excellent heat- and mass transfer and good plug flow character under a broad range of operating conditions. Such features render these reactors appealing, since they are suitable for reactions that require long residence times, improved mass transfer (such as in biphasic liquid-liquid systems) or to homogeneously suspend solid particles. Various OFR configurations, offering specific features, have been developed over the past two decades, with significant progress still being made. This review outlines the principles and recent advances in OFR technology and overviews the synthetic applications of OFRs for liquid-liquid and solid-liquid biphasic systems.

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.

Uncertainty Quantification of NOx Emission Due to Operating Conditions and Chemical Kinetic Parameters in a Premixed Burner

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Sajjad Yousefian ◽  
Gilles Bourque ◽  
Rory F. D. Monaghan
Keyword(s):  
Sensitivity Analysis ◽  
Uncertainty Quantification ◽  
Gas Turbine ◽  
Flow Reactor ◽  
Epistemic Uncertainty ◽  
Plug Flow ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Nox Emission ◽  
Gas Turbine Combustion

Many sources of uncertainty exist when emissions are modeled for a gas turbine combustion system. They originate from uncertain inputs, boundary conditions, calibration, or lack of sufficient fidelity in a model. In this paper, a nonintrusive polynomial chaos expansion (NIPCE) method is coupled with a chemical reactor network (CRN) model using Python to quantify uncertainties of NOx emission in a premixed burner. The first objective of uncertainty quantification (UQ) in this study is development of a global sensitivity analysis method based on the NIPCE method to capture aleatory uncertainty on NOx emission due to variation of operating conditions. The second objective is uncertainty analysis (UA) of NOx emission due to uncertain Arrhenius parameters in a chemical kinetic mechanism to study epistemic uncertainty in emission modeling. A two-reactor CRN consisting of a perfectly stirred reactor (PSR) and a plug flow reactor (PFR) is constructed in this study using Cantera to model NOx emission in a benchmark premixed burner under gas turbine operating conditions. The results of uncertainty and sensitivity analysis (SA) using NIPCE based on point collocation method (PCM) are then compared with the results of advanced Monte Carlo simulation (MCS). A set of surrogate models is also developed based on the NIPCE approach and compared with the forward model in Cantera to predict NOx emissions. The results show the capability of NIPCE approach for UQ using a limited number of evaluations to develop a UQ-enabled emission prediction tool for gas turbine combustion systems.

scholarly journals Design Cum Performance Equation for a Reactor Type Adsorption Unit

2009 ◽  
Vol 1 (3) ◽  
pp. 450-460
Author(s):  
M. A. Islam ◽  
M. S. I. Mozumder ◽  
M. M. R. Khan
Keyword(s):  
Conventional Method ◽  
Flow Reactor ◽  
Plug Flow ◽  
Fixed Bed ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Adsorption System ◽  
Column Test ◽  
Physico Chemical ◽  
Reactor Type

The conventional method for designing a fixed bed adsorption unit has been discussed. The method is based on the data obtained from an adsorption column test. The characterization of an adsorption system, however, is performed in a laboratory batch experiment. It is shown that the conventional method does not make proper use of the physico-chemical parameters of an adsorption system determined by batch test. Also the method fails to predict the performance of an adsorption unit, if the operating condition differs from that under which the column test has been conducted for design purposes. New design equation has been proposed for both ‘Constantly Stirred Tank Reactor (CSTR)’ and ‘Plug Flow Reactor (PFR)’ type adsorption units. The equation predicts the performance of a reactor type adsorption unit under varying operating conditions. The proposed method is based only on the data obtained in batch experiment.Keywords: Adsorption; Unit design; Reactor; Optimal Operation, Dosage; Coefficient of utilization.© 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.DOI: 10.3329/jsr.v1i3.2592     J. Sci. Res. 1 (3), 450-460 (2009)

Reactor Design for Simple Reactions

2001 ◽  
Author(s):  
L. K. Doraiswamy
Keyword(s):  
General Class ◽  
Flow Reactor ◽  
Plug Flow ◽  
Reactor Design ◽  
Design Principles ◽  
Plug Flow Reactor ◽  
Organic Reactions ◽  
Variable Volume ◽  
Stirred Reactor

Ideal reactors and their design principles were discussed in Chapter 4. In addition to these ideal reactors, there are certain reactors in which a reasonably welldefined measure of mixing can be introduced. These are the recycle plug-flow reactor and a sequence of fully mixed reactors. Many organic reactions are conducted in a stirred reactor containing a batch of the same or a second reactant, and continuously feeding, or withdrawing, or feeding and withdrawing one or more of the reactants and/or products. These are referred to as semibatch reactors. They belong to a more general class of reactors known as variable volume reactors. The design of all of these types of reactors is briefly considered in this chapter. The principle of the recycle-flow reactor (RFR) is sketched in Figure 10.1.

Hydrogen Peroxide Effect on HCCI Performance

2001 ◽  
Author(s):  
Cüneyt Uykur ◽  
Andrew L. Zuccato ◽  
Graham T. Reader ◽  
David S.-K. Ting
Keyword(s):  
Hydrogen Peroxide ◽  
Internal Combustion Engines ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Combustion Engines ◽  
Flexible Control ◽  
Hcci Combustion ◽  
Stirred Reactor ◽  
H2o2 Addition

Abstract Methane fueled Homogeneous Charged Compression Ignition (HCCI) combustion is investigated using detailed kinetic modeling. Control of heat release rate is identified as the biggest challenge against HCCI operation. A new control strategy, hydrogen peroxide (H2O2) addition, along with intake mixture preheating, is proposed to resolve this problem. A single-zone perfectly stirred reactor type formulation is employed with detailed chemical kinetic mechanism to predict homogeneous gas-phase chemical kinetics. The effects of H2O2 addition on the performance parameters of a methane-fueled HCCI engine are simulated. The results show that HCCI performance can be improved radically by the addition of H2O2 since it lowers the ignition delay time substantially. The resulting NOx concentration in high IMEP operating conditions is significantly less than that emitted from conventional internal combustion engines. Possibility of increasing NOx emissions with increasing initial temperature has been shown. Reduction in carbon monoxide emission is predicted with the addition of H2O2 via the increased hydroxyl chemistry. More flexible control of HCCI operation is possible by regulating the amount of H2O2 added.

scholarly journals Ozone absorption in a mechanically stirred reactor

2007 ◽  
Vol 72 (8-9) ◽  
pp. 847-855 ◽  
Author(s):  
Ljiljana Takic ◽  
Vlada Veljkovic ◽  
Miodrag Lazic ◽  
Srdjan Pejanovic
Keyword(s):  
Mass Transfer ◽  
Liquid Phase ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Plug Flow ◽  
Operating Conditions ◽  
Volumetric Mass Transfer Coefficient ◽  
Pseudo First Order Reaction ◽  
Ozone Absorption ◽  
Stirred Reactor

Ozone absorption in water was investigated in a mechanically stirred reactor, using both the semi-batch and continuous mode of operation. A model for the precise determination of the volumetric mass transfer coefficient in open tanks without the necessity of the measurement the ozone concentration in the outlet gas was developed. It was found that slow ozone reactions in the liquid phase, including the decomposition of ozone, can be regarded as one pseudo-first order reaction. Under the examined operating conditions, the liquid phase was completely mixed, while mixing in a gas phase can be described as plug flow. The volumetric mass transfer coefficient was found to vary with the square of the impeller speed. .

scholarly journals A High-Throughput Screening Approach to Identify New Active and Long-Term Stable Catalysts for Total Oxidation of Methane from Gas-Fueled Lean–Burn Engines

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 159
Author(s):  
Thomas Lenk ◽  
Adrian Gärtner ◽  
Klaus Stöwe ◽  
Thomas Schwarz ◽  
Christian Breuer ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Flow Reactor ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Plug Flow ◽  
Exhaust Gas ◽  
Lean Burn ◽  
Total Oxidation ◽  
Oxidation Of Methane

A unique high-throughput approach to identify new catalysts for total oxidation of methane from the exhaust gas of biogas-operated lean-burn engines is presented. The approach consists of three steps: (1) A primary screening using emission-corrected Infrared Thermography (ecIRT). (2) Validation in a conventional plug flow gas phase reactor using a model exhaust gas containing CH4, O2, CO, CO2, NO, NO2, N2O, SO2, H2O. (3) Ageing tests using a simplified exhaust gas (CH4, O2, CO2, SO2, H2O). To demonstrate the efficiency of this approach, one selected dataset with a sol-gel-based catalysts is presented. Compositions are 3 at.% precious metals (Pt, Rh) combined with different amounts of Al, Mn, and Ce in the form of mixed oxides. To find new promising materials for the abatement of methane, about two thousand different compositions were synthesized and ranked using ecIRT, and several hundred were characterized using a plug flow reactor and their ageing behaviour was determined.

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