Investigation of Ammonia Formation During Gasification in an Air Blown Spouted Bed

2002 ◽  
Author(s):  
N. Paterson ◽  
Y. Zhuo ◽  
D. R. Dugwell ◽  
R. Kandiyoti
Keyword(s):  
Temperature Control ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Spouted Bed ◽  
Fuel Gas ◽  
Bed Temperature ◽  
Control Options ◽  
High Concentrations ◽  
Ammonia Formation

High NH3 concentrations were measured in the fuel gas produced by a pilot scale, air blown gasifier that was operated by British Coal. A laboratory scale gasifier has subsequently been developed to investigate the reactions that produce these potentially high concentrations. It has been found that in addition to the NH3 formed through pyrolytic processes, the introduction of steam (or H2 produced by its decomposition) increases the amount formed. The latter reaction produced the higher proportion of the total NH3. The effect of the gasifier operating conditions on the amount of NH3 formed has been studied. The main control options to minimise the NH3 formed are using an alternative method of bed temperature control (i.e. avoid the use of steam), operating with higher bed temperatures and operation at lower pressures.

scholarly journals Simulation of a Downdraft Gasifier for Production of Syngas from Different Biomass Feedstocks

2021 ◽  
Vol 5 (2) ◽  
pp. 20
Author(s):  
Mateus Paiva ◽  
Admilson Vieira ◽  
Helder T. Gomes ◽  
Paulo Brito
Keyword(s):  
Modeling And Simulation ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Fuel Gas ◽  
Heating Value ◽  
Downdraft Gasifier ◽  
Process Operation ◽  
Independent Parameters ◽  
Gasification Temperature ◽  
Main Operating

In the evaluation of gasification processes, estimating the composition of the fuel gas for different conditions is fundamental to identify the best operating conditions. In this way, modeling and simulation of gasification provide an analysis of the process performance, allowing for resource and time savings in pilot-scale process operation, as it predicts the behavior and analyzes the effects of different variables on the process. Thus, the focus of this work was the modeling and simulation of biomass gasification processes using the UniSim Design chemical process software, in order to satisfactorily reproduce the operation behavior of a downdraft gasifier. The study was performed for two residual biomasses (forest and agricultural) in order to predict the produced syngas composition. The reactors simulated gasification by minimizing the free energy of Gibbs. The main operating parameters considered were the equivalence ratio (ER), steam to biomass ratio (SBR), and gasification temperature (independent variables). In the simulations, a sensitivity analysis was carried out, where the effects of these parameters on the composition of syngas, flow of syngas, and heating value (dependent variables) were studied, in order to maximize these three variables in the process with the choice of the best parameters of operation. The model is able to predict the performance of the gasifier and it is qualified to analyze the behavior of the independent parameters in the gasification results. With a temperature between 850 and 950 °C, SBR up to 0.2, and ER between 0.3 and 0.5, the best operating conditions are obtained for maximizing the composition of the syngas in CO and H2.

Dynamic Modeling of CATOFIN® Fixed-Bed Iso-Butane Dehydrogenation Reactor for Operational Optimization

2016 ◽  
Vol 14 (1) ◽  
pp. 491-515 ◽  
Author(s):  
Zeeshan Nawaz
Keyword(s):  
Coke Formation ◽  
Fixed Bed ◽  
Process Intensification ◽  
Operating Conditions ◽  
Catalytic Dehydrogenation ◽  
Heating Rates ◽  
Reactor Model ◽  
Fuel Gas ◽  
Bed Temperature ◽  
Operational Optimization

AbstractThe catalytic dehydrogenation of iso-butane to iso-butylene is an equilibrium limited endothermic reaction and requires high temperature. The catalyst deactivates quickly, due to deposition of carbonaceous species and countered by periodic regeneration. The reaction-engineering constraints are tied up with operation and/or technology design features. CATOFIN® is a sophisticated commercialized technology for propane/iso-butane dehydrogenation using multiple adiabatic fixed-bed reactors having Cr2O3/Al2O3 as catalyst, that undergo cyclic operations (~18–30m); dehydrogenation, regeneration, evacuation, purging and reduction. It is always a concern, how to maintain CATOFIN® reactor at an optimum production, while overcoming gradual decrease of heat in catalyst bed and deactivation. A homogeneous one-dimensional dynamic reactor model for a commercial CATOFIN® fixed-bed iso-butane dehydrogenation reactor is developed in an equation oriented (EO) platform Aspen Custom Modeler (ACM), for operational optimization and process intensification. Both reaction and regeneration steps were modeled and results were validated. The model predicts the dynamic behavior and demonstrates the extent of catalyst utilization with operating conditions and time, coke formation and removal, etc. The model computes optimum catalyst bed temperature profiles, feed rate, pre-heating, rates for reaction and regeneration, fuel gas requirement, optimum catalyst amount, overall cycle time optimization, and suggest best operational philosophy.

FB Combustion of a Biomass Fuel: Comparison Between Pilot Scale Experiments and Model Simulations

2003 ◽  
Author(s):  
Francesco Miccio ◽  
Fabrizio Scala ◽  
Riccardo Chirone
Keyword(s):  
Heat Release ◽  
Pilot Scale ◽  
Combustion Efficiency ◽  
Volatile Matter ◽  
High Reactivity ◽  
Operating Conditions ◽  
Biomass Combustion ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Carbon Loading

In the present work the efficiency of the fluidized bed combustion of high-volatile fuels and the extent of volatile matter post-combustion in the splashing zone and freeboard are investigated. A typical Mediterranean biomass (pine-seed shells) has been burned in a pilot-scale bubbling FB combustor (200kWt) at different operating conditions. Both over- and under-bed fuel feeding options have been considered. A FBC model specifically developed for high-volatiles fuels has been also applied to provide a comparison with bed carbon loading, in-bed heat release and splashing region temperature experimental data. Experimental results showed that the biomass combustion efficiency is always very high as a consequence of the high reactivity of the fuel. Extensive volatiles post-combustion above the bed is observed, whose extent appears to be sensitive to the over/under bed feeding option and to the excess air. Approximately 80% of the total heat is released/recirculated in the bed, the remainder leading to appreciable overheating of the freeboard with respect to the nominal bed temperature. Very low bed carbon loadings have been found. Model results compare well with the experimental temperature, heat release and carbon loading trends. However, detailed prediction of the freeboard temperature profiles requires further improvements of the model.

Attrition Behavior of Coal Ash Under Circulating Fluidized Bed Combustion Conditions

2003 ◽  
Author(s):  
Franz Winter ◽  
Xin Liu
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Silica Sand ◽  
Electrical Heating ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Wide Range

The attrition behavior of ash produced from two bituminous and one anthracite coal was studied under laboratory-scale circulating fluidized bed combustor (CFBC) conditions. After the ash was produced in the oven, the ash sample with a size range from 0.1 to 1 mm was fed into the hot CFBC, which was heated by electrical heating shells and fluidized by air. The laboratory-scale CFBC was operated with using fine silica sand (40 to 80 μm) as bed material. After a certain time the operation was stopped, all particles were collected and sieving analysis was performed to obtain the actual particle size distribution (PSD) of the coal ash. The operating conditions were changed in a wide range, i.e. the bed temperature from 600 to 850°C, the fluidizing velocity from 1.2 to 2 m/s, the residence time from 60 to 120 min and the design of the cyclone. The effects of operating conditions and coal type were studied and their relative importance is discussed. Elemental analysis of the coal ashes showed that Si and Ca may play an important role during attrition.

Gasification Tests With Sewage Sludge and Coal/Sewage Sludge Mixtures in a Pilot Scale, Air Blown, Spouted Bed Gasifier

2002 ◽  
Author(s):  
N. Paterson ◽  
G. P. Reed ◽  
D. R. Dugwell ◽  
R. Kandiyoti
Keyword(s):  
Sewage Sludge ◽  
Pilot Scale ◽  
Process Performance ◽  
Spouted Bed ◽  
Fuel Conversion ◽  
Fuel Gas ◽  
Bed Height ◽  
Coal Mixtures ◽  
Very High

A series of tests have been done in a pilot scale air blown gasifier, to assess the performance of sewage sludge pellets and sewage sludge pellet/coal mixtures. The aim has been to compare the performances with that achieved with coal alone and to assess the suitability of the sewage containing fuel as a candidate fuel for the Air Blown Gasification Cycle (ABGC). The co-gasification of sewage sludge with coal raised both the CV of the fuel gas and the fuel conversion compared with values achieved with coal alone. The mixtures were operated under very similar conditions to those needed with coal and no adverse operational problems were encountered. A lower fluidising velocity was needed with the neat pellets to enable a stable bed height to be achieved. However, the conversion of the pellets to gas was very high and the fuel gas CV was higher than that achieved during the co-gasification tests. Overall, the results suggest that sewage based materials are suitable for use in the ABGC and that their use can improve the process performance.

Modeling a Silicon CVD Spouted Bed Pilot Plant Reactor

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Juliana Piña ◽  
Verónica Bucalá ◽  
Noemí Susana Schbib ◽  
Paul Ege ◽  
Hugo Ignacio de Lasa
Keyword(s):  
Population Balance ◽  
Particle Growth ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Spouted Bed ◽  
Reactor Model ◽  
Plant Reactor ◽  
Short And Long Term ◽  
Pilot Scale Reactor

This study reports a comprehensive multiphase gas-solid dynamic mathematical model that successfully describes the batch growth of silicon particles in a CVD submerged spouted bed reactor. This multiphase reactor model takes into account the hydrodynamics and interphase mass exchange between the different fluidized bed regions (spout or grid zone, bubbles and emulsion phase) and uses applicable kinetic rate models to describe both heterogeneous and homogeneous reactions. The model also incorporates a population balance equation representing particle growth and agglomeration.The CVD submerged spouted bed reactor operation is simulated by means of a sequential modular procedure, which involves the solution of the reactor model and the population balance equation.It is shown that the proposed CVD multiphase reactor model successfully simulates experimental data obtained from batch operation in a pilot scale reactor at REC Silicon Inc. The modeling of experiments obtained for different operating conditions allows correlating the scavenging factor as a function of the silane concentration for short- and long-term operations.

An Investigation on Low-Temperature Fluidized Combustion of Liquid Fuels

2005 ◽  
Author(s):  
Lorenzo Ferrante ◽  
Michele Miccio ◽  
Roberto Solimene ◽  
Francesco Miccio
Keyword(s):  
Low Temperature ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Liquid Fuels ◽  
Experimental Program ◽  
Data Series ◽  
Low Temperature Combustion ◽  
Splash Zone ◽  
Fuel Injector ◽  
Bed Temperature

Presently, the combustion at low temperature is receiving a great deal of interest because emissions of micro- and nano-pollutants are expected to be greatly reduced. Following previous studies on the low temperature combustion behavior, the authors report results and discussion of steady-state experiments on an atmospheric, pre-pilot scale, 140 mm ID, FB reactor, equipped with an under-bed, air-assisted, liquid-fuel injector. The experimental program was focused on the operation at temperatures lower than the classical value for FBC of solid fuels (i.e., 850°C). The data series taken into consideration are the concentrations of the main unburned species in the splash zone, those of oxygen measured in the bed and in the splash zone as well as the freeboard pressure. The interpretation of the results is mainly based on the statistical analysis in the time domain. The combustion pattern of bio-diesel is compared to that of the diesel fuel under varying operating conditions (e.g., bed temperature, dispersion air velocity at the fuel nozzle, injector height in the bed). Conclusions that were previously published on the base of lab-scale results are checked against new data obtained on the pilot scale. An innovative technique for the analysis of the micro-explosive regime is presented. It consists in the comparison of oxygen concentration measured by the zirconia-based probes at different heights in the bed and in the splash region, pressure signals measured in the freeboard and purposely filtered, and video-recordings of the bed surface phenomena.

Pilot Scale Study on Advanced Treatment of Coking Wastewater with Biological Activated Carbon Technology

2014 ◽  
Vol 1073-1076 ◽  
pp. 995-999
Author(s):  
Jin Li ◽  
Guang Hua Wang ◽  
Wen Bing Li ◽  
Zheng Zhu ◽  
Yin An Zhu
Keyword(s):  
Activated Carbon ◽  
Removal Rate ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Advanced Treatment ◽  
Coking Wastewater ◽  
Biological Activated Carbon ◽  
Scale Test ◽  
Cod Removal Rate

This paper reports about a pilot-scale feasibility study of Advanced Treatment of Coking Wastewater with Biological Activated Carbon technology based on the better experimental data of laboratory scale test .The self-designed of the Biological Activated Carbon Aerated tower was based on the optimal operating conditions of the results obtained from laboratory scale test.The removal efficiency to pollutants of efficient compound bacterium is estimated in biological activated carbon process through the variation of COD concentration, chromaticity, and Contrast the total ion chromatogram and UV absorbance spectrum of effluent and inflow.The results of the pilot-scale test show that BAC technology may be a suitable option for the advanced treatment of Coking Wastewater. the efficient degrading strains can reproduce on the activated carbon quickly.Concentrations of COD and chromaticity in outflow water were at a lower level (with COD about 60mg/L and chromaticity about 50 degree), the average COD removal rate greater than 50% and chromaticity removal rate greater than 70%.

scholarly journals Laboratory and Semi-Pilot Scale Study on the Electrochemical Treatment of Perfluoroalkyl Acids from Ion Exchange Still Bottoms

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2873
Author(s):  
Vanessa Y. Maldonado ◽  
Michael F. Becker ◽  
Michael G. Nickelsen ◽  
Suzanne E. Witt
Keyword(s):  
Ion Exchange ◽  
Environmental Concern ◽  
Degradation Kinetics ◽  
Coulombic Efficiency ◽  
Pilot Scale ◽  
Electrochemical Treatment ◽  
Laboratory Scale ◽  
Perfluoroalkyl Acids ◽  
Boron Doped Diamond ◽  
High Concentrations

The ubiquitous presence of perfluoroalkyl acids (PFAAs) in the environment remains a serious environmental concern. In this study, the electrochemical oxidation (EO) of PFAAs from the waste of ion exchange (IX) still bottoms was assessed at the laboratory and semi-pilot scales, using full boron-doped diamond (BDD) electrochemical cells. Multiple current densities were evaluated at the laboratory scale and the optimum current density was used at the semi-pilot scale. The results at the laboratory scale showed >99% removal of total PFAAs with 50 mA/cm2 after 8 h of treatment. PFAAs treatment at the semi-pilot scale showed 0.8-fold slower pseudo-first-order degradation kinetics for total PFAAs removal compared to at the laboratory scale, and allowed for >94% PFAAs removal. Defluorination values, perchlorate (ClO4−) generation, coulombic efficiency (CE), and energy consumption were also assessed for both scales. Overall, the results of this study highlight the benefits of a tandem concentration/destruction (IX/EO) treatment approach and implications for the scalability of EO to treat high concentrations of PFAAs.

scholarly journals Process characterization and energy balance of air wood residues gasification using continuous operated pilot scale reactor

2020 ◽  
Vol 180 ◽  
pp. 02018
Author(s):  
Cora Gheorghe-Bulmau ◽  
Raluca Nicoleta Tirtea ◽  
Gabriela Ionescu ◽  
Cosmin Marculescu
Keyword(s):  
Energy Balance ◽  
Rotary Kiln ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Process Efficiency ◽  
Major Influence ◽  
Fuel Gas ◽  
Gasification Process ◽  
Process Characterization ◽  
Pilot Scale Reactor

This work aimed to study the effect of gasification process operating conditions on syngas composition and properties, and process efficiency. A rotary kiln gasifier lab-scale pilot plant with capacity ≅ 30 kg/h and a power of 30 kWe was used for gasification tests applied to cherry wood at different loads, for a temperature of about 600°C, while the air was used as gasification agent for all tests. The syngas composition was measured and analyzed. The results have shown that conversion of wood cherry through gasification lead to a lean fuel gas of 3.5 MJ/Nm3 and installation characteristics have a major influence both on process and syngas properties. This is happened because the rotary kiln gasifier allows some air infiltrations, and consequently a high N2 content in the syngas composition. The energy balance of the cherry biomass gasification processes was calculated. It was found also that gas density varies slightly from 1.26 to 1.43 kg/m3, while the specific heat of the gas varies from 1.04 to 1.34 kJ/kgK.

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