The effect of pressure on the formation of nitrogen oxides from coal char combustion in a small fixed-bed reactor

Fuel ◽  
1994 ◽  
Vol 73 (7) ◽  
pp. 1034-1038 ◽  
Author(s):  
J RICHARD ◽  
M MAJTHOUB ◽  
M AHO ◽  
P PIRKONEN
2014 ◽  
Vol 694 ◽  
pp. 136-141 ◽  
Author(s):  
Jing Hong Lian ◽  
Zi Fang Wang ◽  
Wei Ji ◽  
Guang Yang ◽  
Lian Sheng Liu ◽  
...  

Experiments of biomass char combustion in 10%O2/90%CO2, 21%O2/79%CO2, 10%O2/90%N2 and 21%O2/79%N2 atmospheres were performed in the fixed-bed reactor system at the temperature of 800°C-1200°C. The results show that at the same temperature, NO emission is higher in O2/N2 atmosphere than that in O2/CO2 atmosphere. The higher the O2 concentration is, the higher the NO yield is. As the temperature rises, the NO yield rises at first and then decreases at the same O2 concentration and atmosphere.


Author(s):  
Markus Engblom ◽  
Pia Kilpinen ◽  
Fredrik Klingstedt ◽  
Kari Era¨nen ◽  
Ranjit Katam Kumar

Present paper is a part of our on-going model development activities with aim to predict formation tendency of gaseous emissions from CFB combustion of different fuels, and especially, fuel-mixtures in real furnaces of various scale. The model is based on detailed description of homogeneous, catalytic, and heterogeneous chemical kinetics, and a sound but simple 1.5D representation of fluid dynamics. Temperature distribution is assumed known. With the tool, different fuels and fuel mixtures can be compared in respect to their tendency to form nitrogen oxides (NOx, N2O). In this paper the model was tested to predict nitrogen oxide emissions from mono- or co-combustion of coal, wood, and sludge. The plants simulated were the 12MWth CFB combustor located at Chalmers Technical University (A = 2.25m2, h = 13.6m) and the pilot scale CFB unit at the Technical University Hamburg-Harburg (d = 0.1m, h = 15m). The results gave reasonable representation of the measured emission data, and reflected correctly to the changes in the fuel characteristics and in the furnace operating conditions in most cases. An extensive laboratory fixed-bed reactor study was also performed in order to obtain input values for the kinetic constants of the catalytic reactions for the reduction and decomposition of nitrogen oxides. In literature, there is a limited data available regarding the catalytic activity of CFB solids during combustion of wood- and waste-derived fuels, especially at co-firing conditions. The kinetics for the NO reduction by CO in the temperature range of 780–910°C was determined to be of the following form (NO = 300ppm, CO = 5000ppm): −rNO=k·[NO]0.48·[CO]0.55mol/g-s with k=8.15·exp(−8869/T)m3/kg-s(emptyreactoreffectincluded)ork=830·exp(−14930/T)(emptyreactoreffectexcluded), when using a bed sample (250–355 μm) taken from the transport zone in the CTH boiler while burning a mixture of wood pellets and a pre-dried municipal sewage sludge. The role of char particle size and shape as well as the incorporation of energy balance on the char reactivity and the formation of nitrogen oxides is further illustrated by single char particle oxidation simulations.


2013 ◽  
Vol 1 (9) ◽  
pp. 544-550 ◽  
Author(s):  
Yifei Wang ◽  
Weilong Jin ◽  
Taohua Huang ◽  
Longchu Zhu ◽  
Chaoqi Wu ◽  
...  

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2210
Author(s):  
Hans-Joachim Gehrmann ◽  
Bo Jaeger ◽  
Siegmar Wirtz ◽  
Viktor Scherer ◽  
Krasimir Aleksandrov ◽  
...  

The emission from industries and the mobility sector is under strong legal regulations in many countries worldwide. In Germany, the amendment to the 17th BlmSchV (Federal pollution control ordinance), which has been in force for waste incineration plants since 2013, has given rise to a new limit for nitrogen oxides of 150 mg/m3 as the daily mean level from 2019 on. A similar focus is on biomass-fired plants. According to the MCP (medium combustion plant) guideline of the EU, as a consequence, existing plants are required to either increase their consumption of ammonia water for nitrogen oxide reduction (SNCR process) or back fit SCR catalysts as secondary measures, which is a costly procedure. This paper presents a novel two-stage process in which an oscillating supply of secondary air allows nitrogen oxides to be reduced by approx. 50% at a good burnout level, which may obviate the need for secondary measures. Besides experimental investigations in a fixed bed reactor, CFD simulations confirm a high potential for reduction of nitrogen oxides. Together with the company POLZENITH, this process is under development for scale-up in a biomass incineration plant as a next step.


2013 ◽  
Vol 19 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Jae-Young Kim ◽  
Young Cheol Park ◽  
Sung-Ho Jo ◽  
Ho-Jung Ryu ◽  
Jeom-In Baek ◽  
...  

2001 ◽  
Vol 21 (9) ◽  
pp. 917-928 ◽  
Author(s):  
H.H. Liakos ◽  
K.N. Theologos ◽  
A.G. Boudouvis ◽  
N.C. Markatos

2018 ◽  
Vol 156 ◽  
pp. 02008
Author(s):  
Yusuf Rumbino ◽  
Suryo Purwono ◽  
Muslikhin Hidayat ◽  
Hary Sulistyo

The aim of this research was to investigate the gasification of a South Kalimantan lignite coal char in the temperature range of 873-1073 ºK and steam condition to evaluate the reactions rates and the product gas compositions. Prior to the gasification experiments the raw char was pyrolysed under nitrogen atmosphere and at a temperature of 673 ºK. The gasification experiments were conducted in a fixed bed reactor, at atmospheric pressure, isothermal conditions, equipped with cooling system, gas reservoir, and temperature control. Char from coal pyrolysis weighed then gasified at variations of temperature. Gas sampling is done every 15 minutes intervals for 90 minutes. The reactivity study was conducted in the kinetically controlled by the heterogeneous reaction between solid carbon from the char and a gas phase reagent. Two theoretical models were tested to fit the experimental data and the kinetic parameters were determined. It was found that an increase in temperature enhances the reaction rate and also the formation of H2, CO, CH4, and CO2. The results show that higher temperature contributes to more hydrogen production The gasification kinetics was suitably described by the Random Pore Model. Activation energy determination of char gasification reactions by using Arrhenius graph.


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