Entrained Flow Research Articles

Fuel Particle Conversion of Pulverized Biomass during Pyrolysis in an Entrained Flow Reactor

This study addresses the change of char morphology and fuel conversion during pyrolysis in a laminar entrained flow reactor by experiments and particle simulation. Three experimental parameters were examined: reaction temperature (1073 and 1273 K); particle size (125–250, 250–500, and 500–1000 μm); and the length of reaction zone (650 and 1885 mm). The scanning electron microscopic (SEM) images showed that biomass swelled during heating and shrank during initial stage of pyrolysis. Then, char morphology transformed to cenospheres after the plastic stage. The yields of solid residue from the experiments were reasonably predicted by particle simulation. To give a guideline for the design of laminar entrained flow pyrolysis reactors, the required reactor length for complete conversion of biomass was also calculated for the pyrolysis. High reaction temperature, small particles, and slower gas flow were favorable for high fuel conversion.

Comparative Study of Gasification Performance between Bituminous Coal and Petroleum Coke in the Industrial Opposed Multiburner Entrained Flow Gasifier

A comprehensive three-dimensional numerical model for simulating Shenfu bituminous coal and petroleum coke in the industrial opposed multiburner (OMB) gasifier is established. The “effectiveness factor” method is used to extrapolate the intrinsic char reactivity data to industrial gasifier conditions. With the proposed models, the predicted gasification performance of Shenfu coal is in good agreement with industrial operating data, and the predicted carbon conversion of petroleum coke is about 96.7%. Comparing with Shenfu coal, the specific solid fuel consumption of petroleum coke is lower, while the specific oxygen consumption is higher. The characteristic of char gasification in the entrained flow gasifier is investigated. In the high temperature jet flow region and impinging flow region, when the particle diameter is above 200 μm, the Thiele modulus of the char gasifying with steam for Shenfu coal and petroleum coke are 15.4 and 4.8, respectively. Therefore, pore diffusion has a significant effect on the apparent char reactivity. While for the char gasifying with CO2, the Thiele modulus is below 5 in different regions of the OMB gasifier, and the apparent char reactivity is affected by the chemical reaction and pore diffusion. When the char reactivity of petroleum coke is accelerated at 5 times by catalysis effects, the carbon conversion reaches 99.2% and the consumption of oxygen and feedstock decrease obviously. Importantly, the temperature at the dome of the gasifier decreases to 1345 °C, which prolongs the life of refractory wall and favors a long period of availability for the gasifier.

Numerical Simulation of Industrial Opposed Multiburner Coal–Water Slurry Entrained Flow Gasifier

A comprehensive three-dimensional numerical model is developed for simulation of the industrial opposed multiburner (OMB) coal–water slurry (CWS) entrained flow gasifier. The CWS gasification process is divided into several submodels, including water evaporation, coal pyrolysis, and homogeneous and heterogeneous char reactions. The “effectiveness factor” method is used to extrapolate the intrinsic char reactivity data to industrial CWS gasifier conditions. Numerical simulations with the proposed models are performed on the industrial OMB gasifier, and the predicted temperature and gas compositions at the outlet of the gasifier are in good agreement with industrial operating data. The profiles of flow field, temperature, and gas composition in the gasifier are described. In addition, the effects of the slurry concentration and oxygen/coal ratio on the gasifier performance are also studied, which reveal that the lower oxygen/coal ratio or higher slurry concentration leads to higher cold gas efficiency, whil...

Hydrogen production from biomass gasification in the oil refining industry – A system analysis

In this paper, the global CO2 effect of integrating different biomass gasification concepts to meet an increasing demand of hydrogen in an oil refinery is examined and presented in comparison with a conventional steam reformer. The studied refinery is a hydro skimming refinery with a future hydrogen deficit of 16,000 Nm3/h. Three gasification concepts are considered: Entrained Flow (EF), Circulated Fluidised Bed (CFB) and Double Bed (DB). The system analysis is made with respect to global CO2 emissions and primary energy use. The results show that if biomass is considered as an unlimited resource (i.e. sufficient biomass is considered to be available to substitute for all fossil fuels in society), biomass gasification concepts have a potential to reduce CO2 emissions. The EF case shows the largest reduction potential. However, if biomass is considered as a limited resource (i.e. increased use of biomass at the refinery will lead to increased use of fossil fuel elsewhere in society), all concepts show an increase of CO2 emissions. Here, the CFB gasifier shows lowest increase of CO2 emission. The CO2 effect of the different alternatives shows sensitivity to assumptions regarding alternative biomass user.

Experimental investigation of high temperature and high pressure coal gasification

Pyrolysis and gasification behavior is analyzed at operation conditions relevant to industrial scale entrained flow gasifiers. A wire mesh reactor and the Pressurized High Temperature Entrained Flow Reactor (PiTER) are used to measure volatile yield of Rhenish lignite, a bituminous coal and German anthracite at high temperature and high pressure. In the wire mesh reactor at 1000 °C a significant influence of pressure on volatile yield is observed. For lignite the volatile yield (daf) decreases from 57 wt% at atmospheric pressure to 53 wt% at 5.0 MPa. In the same pressure interval the volatile yield of the bituminous coal strongly decreases, whereas no significant influence of pressure on the volatile yield of anthracite is detected. In entrained flow experiments (PiTER) at higher temperature and 0.5 MPa an enhanced devolatilization of the lignite is observed. At 1200 °C, the maximum volatile yield is 62 wt% and it increases to 67 wt% at 1400 °C. In entrained flow gasification experiments with Rhenish lignite a high level of conversion is measured at atmospheric pressure and at 0.5 MPa. At both pressures, coal conversion increases with temperature and residence time. The highest conversion of 96 wt% is achieved at a particle residence time of 1.3 s, at a temperature of 1600 °C, and a pressure of 0.5 MPa. The experimental results show a large influence of operation parameters on pyrolysis and gasification behavior of Rhenish lignite. The volatile release in the pyrolysis stage and the high level of conversion after a short residence time indicate that Rhenish lignite is suitable for gasification in an entrained flow reactor. The reactivities of char samples that are collected from the hot reaction zone of the PiTER are measured in a pressurized thermogravimetric analyzer (PTGA) at lower temperature (600–850 °C). The pyrolysis temperature in the entrained flow experiments significantly influences the reaction rate in the PTGA at lower temperature. With increasing pyrolysis temperature (1200–1600 °C) a continuous loss of reactivity is observed.

Elucidation of Biomass Pyrolysis Products Using a Laminar Entrained Flow Reactor and Char Particle Imaging

We have mapped the formation of tars during white oak thermochemical conversion using a bench scale laminar entrained flow reactor (LEFR). White oak particles (80 mesh, <180 μm) were pyrolyzed under conditions not limited by heat transfer. Measurements were made with residence times of 0.2, 0.4, 0.6, and 0.8 s, between 500 and 900 at 100 °C increments, and with residence times of 1 s at temperature from 450 to 950 °C at 25 °C increments. Products were monitored with a molecular beam mass spectrometer (MBMS), and the mass spectra were analyzed using model-free multivariate analysis (multivariate curve resolution). Six groups of correlated masses were identified that suggest the mechanisms of pyrolysis and gasification. The first group of masses (lowest temperature) is associated with primary species from lignin and hemicellulose, followed by cellulose products. The next two groups (increasing temperature) are composed of secondary products resulting from the cracking of carbohydrate vapors and the cracking of lignin in the gas or solid phase. Molecular weight growth products are seen in the next two groups including substituted aromatic compounds in the fifth group and polycyclic aromatic hydrocarbons (PAHs) in the sixth group. The results of this study show that as the temperature of pyrolysis is increased, the molecular weight of the tars decreases up to 750 °C, because the pyrolysis vapors are cracked. As the temperature increases beyond 750 °C, molecular weight growth is seen with increasing temperature. The analysis also shows that as the temperature increases from 450 to 950 °C, oxygen is lost from the tars and converted into CO and CO2. The char samples were collected and analyzed with light and electron microscopy. This analysis revealed that micropores develop in the cell wall around 550 °C and increase in size and coalesce into a cenosphere morphology with increasing temperature. Above 850 °C, these cenospheres appear to rupture, releasing their contents into the gas phase. This rupture event correlates with increased MBMS signals from PAH-associated masses.

3-1-2 気流層反応器による木質系バイオマスの急速熱分解特性(3-1 熱分解1,液化,Session 3 バイオマス等,研究発表)

3-1-2 気流層反応器による木質系バイオマスの急速熱分解特性(3-1 熱分解1,液化,Session 3 バイオマス等,研究発表)

Impact of torrefaction on syngas production from wood

Torrefaction is a way to treat biomass before transportation or thermochemical conversion. It can be used to increase the energy content of wood or to facilitate grinding. The purpose of this paper was to quantify the impact of such a treatment on the behaviour of wood during gasification by steam at high temperature to produce syngas. The aspects of both gas yields and reaction kinetics were considered. Beechwood was submitted both to light torrefaction and severe torrefaction, using a specially designed crossed fixed bed reactor. The initial wood and the torrefied woods were first characterised, then gasified in a new laboratory high-temperature entrained flow reactor (HT-EFR) at 1400 °C for 2 s in an atmosphere containing 20 vol% steam in N 2. The syngas produced was then analysed. The experiments were modelled using a thermo-dynamical equilibrium approach. It was confirmed that torrefaction decreased the O/C ratio. The quantity of syngas produced increased with the severity of the torrefaction. The equilibrium approach describes the results satisfactorily. Gasification experiments carried out at a lower temperature – 1200 °C – indicated that the chars from torrefied woods are less reactive towards steam than the char from wood.

203 気流層反応器による木質系バイオマスの急速熱分解特性(循環型廃棄物処理技術(1))

203 気流層反応器による木質系バイオマスの急速熱分解特性(循環型廃棄物処理技術(1))

Efficiency of an Integrated Gasification Combined Cycle (IGCC) power plant including CO2 removal

This study is devoted to technical evaluation of a carbon dioxide removal in an existing Integrated Gasification Combined Cycle (IGCC) plant. This IGCC case is based on an oxygen blown entrained flow gasifier operating at 27 bar, the removal of acid gas (H2S) is performed with MDEA unit, the efficiency of this IGCC is 43% based on the low heating value (LHV) of coal. A carbon dioxide separation unit conveniently integrated in a pre-combustion separation process is chosen, in order to take advantage of the high pressure of the gas. The methanol process for carbon dioxide removal is integrated downstream the existing desulfuration unit, and after a CO shift conversion unit. In this study, the integration of the CO2 capture process to the IGCC is simulated as realistically as possible. The design parameters of both the gas turbine (the turbine inlet temperature, compressor pressure ratio, reduced flow rate) and the steam turbine (Stodola parameter) are taken into account. Maintenance of low NOx production in the combustion chamber is also considered. The production of NOx is supposed to be influenced by the low heating value of the gas which is maintained as low as for case of the synthesis gas without CO2 capture. Thus the choice is made to feed the gas turbine of the combined cycle with a diluted synthesis gas, having similar low heating value than the one produced without the CO2 capture. Plant performances for different conversion and capture rates are compared. A final optimized integration is given for 92 mol% CO conversion rate and 95 mol% CO2 absorption rates, a comparison with former studies is proposed.

The effect of mineral additions on coal ash deposition

The introduction of low-NOx burners to UK coal-fired power stations has changed the nature of ash deposition within the boilers. Lower peak flame temperatures and the delayed mixing of combustion air have reduced the rate of mineral transformations. The resulting ash is finer and less ‘sticky’ than the ash produced with conventional burners, reducing the proportion of saleable bottom ash and increasing the load on electrostatic precipitators. One possible solution is to use a mineral additive to increase the proportion of coal ash that deposits in the boiler.Coal-additive mixtures have been prepared and combusted on an entrained flow reactor that reproduces the time–temperature history of particles in a pulverised coal-fired boiler. Six additives were tested with three coals; ash and deposit samples were collected and characterised. Calcite and albite produced the greatest change in deposit properties, and these two minerals were studied in further entrained flow reactor trials and on the RWE 0.5 MW combustion test facility. The re-firing of fly ash was also studied on the CTF. These additives did have an effect on deposit growth and microstructure, but did not reverse the impact of low-NOx burners on coal ash behaviour.

Conversion of Biomass Based Slurry in an Entrained Flow Gasifier

AbstractA two‐step process, BIOLIQ, with pyrolysis and subsequent entrained flow gasification has been developed at the Forschungszentrum Karlsruhe to produce synfuel from biomass. Experiments in a 60 kW pilot‐scale atmospheric entrained flow gasifier allow quantitative evaluation of the combustion behavior of biomass‐based slurry, leading to a better understanding of the gasification process.

KINETICS OF FAST PYROLYSIS OF RICE HUSKS USING AN EXTERNALLY PLASMA-HEATED LAMINAR ENTRAINED FLOW REACTOR

A plasma-heated laminar entrained flow reactor (LEFR) was developed for studying the kinetics of fast pyrolysis of biomass particles at rapid heating rates. In order to achieve a controllable, stable, and uniform high-temperature gas flow in the reactor, a plasma jet was used as the primary heating source for the LEFR, and an electric heater was used as an auxiliary heating source. Reynolds number was used as the principle of similitude to determine the flow distribution in the reactor through a series of cold flow tests. Comprehensive temperature measurements were taken, and corresponding temperature profiles were obtained. Experiments using rice husk were conducted in the LEFR. The results showed that biomass particles below 100 .m could be pyrolyzed sufficiently, and thus the pyrolysis kinetics of biomass could be studied in this reactor. Based on the experimental data, a kinetic model for rice husk was proposed, and the kinetic parameters (i.e., activation energy and frequency factor) were determined.

Devolatilization characteristics of biomass at flash heating rate

The devolatilization characteristics of biomass (wheat straw, coconut shell, rice husk and cotton stalk) during flash pyrolysis has been investigated on a plasma heated laminar entrained flow reactor (PHLEFR) with average heating rates of 10 4 K/s. These experiments were conducted with steady temperatures between 750 and 900 K, and the particle residence time varied from about 0.115 to 0.240 s. The ash tracer method was introduced to calculate the yield of volatile products at a set temperature and the residence time. This experimental study showed that the yield of volatile products depends both on the final pyrolysis temperature and the residence time. From the results, a comparative analysis was done for the biomasses, and a one-step global model was used to simulate the flash pyrolytic process and predict the yield of volatile products during pyrolysis. The corresponding kinetic parameters of the biomasses were also analyzed and determined. These results were essential for designing a suitable pyrolysis reactor.

CO 2 gasification rate analysis of coal char in entrained flow coal gasifier

Coal chars of four coal types were gasified with carbon dioxide using a PDTF or TGA at high temperature and pressure. Test conditions of temperature and partial pressure of the gasifying agent were determined to simulate the conditions in air-blown or oxygen-blown entrained flow coal gasifiers. Coal chars were produced by rapid pyrolysis of pulverized bituminous coals using a DTF with a nitrogen gas flow at 1670 K. In gasification tests with the PDTF, gasification temperatures were 1670 K or below and partial pressures of carbon dioxide were 0.7 MPa or below. Carbon monoxide of 0.6 MPa or below was supplied for the gasification tests with the TGA. As a result, coal types showed a large difference in the char gasification rate with carbon dioxide, and this difference remained large without decreasing even in the high-temperature area when the gasification rate was controlled by pore diffusion the same as in entrained flow gasifiers. Inhibition of the gasification reaction by carbon monoxide was also observed. Reaction rate equations of both the nth order and Langmuir–Hinshelwood type were applied to the char gasification reaction with the random pore model and the effectiveness factor, and the applicability of these rate equations to air-blown and oxygen-blown entrained flow gasifiers evaluated. Gasification rate equations and kinetic parameters applicable to a pore diffusion zone at high temperature were obtained for each coal.

Flash pyrolysis of agricultural residues using a plasma heated laminar entrained flow reactor

Abstract In order to study the volatilization characteristics of biomass particles at flash heating rates, a plasma heated laminar entrained flow reactor (PHLEFR) was designed and built in our lab. Two agricultural residues, wheat straw and corn stalk, were chosen as feedstock for pyrolysis which were conducted on the PHLEFR with the aim of determining the extent of thermal decomposition at high heating rate (more than 104 °C s−1). Based on the experimental data, a first order kinetic model was introduced and the relevant kinetic parameters (apparent active energy and apparent frequency factor) were determined for the two straws: E = 31.51 kJ mol - 1 , A = 1028 s - 1 (wheat straw) and E = 33.74 kJ mol - 1 , A = 1013 s - 1 (corn stalk). The predicted conversion of the fitted model to the experimental data provided general agreements when one considered the experimental errors.

Three-Dimensional Characterization of a Pure Thermal Plume

Pure thermal plumes have been investigated by two-dimensional (2D) and three-dimensional (3D) particle imaging velocimetry (PIV) techniques. While classical plume features have been checked out, time-dependent analysis allows one to clearly detect contraction and expulsion phases which are mainly driven by turbulent structure behavior. Balance of momentum equation demonstrates the link between stronger structures and expulsion-contraction motion mainly dominated by plume engulfment during contraction phases. A ratio of 3 between entrained mass flow rate during contraction and expulsion phases has been estimated. A new method, never previously applied to pure thermal plume, allows one to accurately characterize entrainment mechanism and for the first time, the latter renders it possible to estimate the entrainment coefficient all along the plume height, even close to the heating source. Moreover, entrainment coefficient is found to be 20% higher with direct method as opposed to the classical differential one widely used in the literature. Such a huge gap is found to be due to the fluctuating density and velocity part. Even through it markedly contributes to an enhanced entrainment mechanism, the role of fluctuation was generally overlooked in the previous works devoted to entrainment coefficient estimate.

Design and Characterization of an Entrained Flow Reactor for the Study of Biomass Pyrolysis Chemistry at High Heating Rates

A laminar entrained flow reactor has been designed for studying the chemistry of fast biomass pyrolysis. This is the first of two papers on the reaction system. Peak heating rates in the reactor ar...

Experimental Investigation of a Vertical Planar Jet by Ultrasound and Laser Doppler Velocimetry

An experimental investigation on the velocity field of a water-jet injected vertically into a water pool was conducted. The jet flowed from a thin rectangular nozzle and was considered to be quasi-planar as it was confined along two parallel planes. Velocity measurements of the jet and the surrounding entrained flow regions were made respectively by ultrasound and laser Doppler velocimetries (UDV and LDV). In contrast to LDV, UDV operates on the principle of pulsed ultrasound echography and in our experiment, a single transducer held at a 10° angle with respect to horizontal (x-axis) was vertically traversed. The measured velocity thus represents the velocity component along this beam angle. The hydraulic diameter (D) based Reynolds numbers of flow were, Re=1.79×104 (UDV), 3.58×104 (LDV), 7.15×104 (LDV), corresponding to average exit velocities of 0.5, 1.0 and 2.0 m/s. Comparisons of the traditional jet parameters, such as the decay of the centerline and jet's half-radius vs. axial distance (z-axis), against established data confirmed proper jet-like behavior of our test facility. The conclusions from the experiments were as follows: (1) that UDV shows trends and magnitudes similar to data obtained by LDV; both velocimetry methods are applicable to this type of experimental flow configuration, (2) data presented as the axial decay of centerline velocity and jet half-radius, are consistent and similar to past experimental data, mostly of gas jets, and (3) radial profiles show agreement with a past correlation up to R/R 1/2 > 1. There are differences however, between the correlation and the data, for R/R 1/2 > 1, the latter which were showed consistent trends.

Experimental Investigation of a Vertical Planar Jet by Ultrasound and Laser Doppler Velocimetry.

An experimental investigation on the velocity field of a water-jet injected vertically into a water pool was conducted. The jet flowed from a thin rectangular nozzle and was considered to be quasi-planar as it was confined along two parallel planes. Velocity measurements of the jet and the surrounding entrained flow regions were made respectively by ultrasound and laser Doppler velocimetries (UDV and LDV). In contrast to LDV, UDV operates on the principle of pulsed ultrasound echography and in our experiment, a single transducer held at a 10° angle with respect to horizontal (x-axis) was vertically traversed. The measured velocity thus represents the velocity component along this beam angle. The hydraulic diameter (D) based Reynolds numbers of flow were, Re=1.79×104 (UDV), 3.58×104 (LDV), 7.15×104 (LDV), corresponding to average exit velocities of 0.5, 1.0 and 2.0 m/s. Comparisons of the traditional jet parameters, such as the decay of the centerline and jet's half-radius vs. axial distance (z-axis), against established data confirmed proper jet-like behavior of our test facility. The conclusions from the experiments were as follows: (1) that UDV shows trends and magnitudes similar to data obtained by LDV; both velocimetry methods are applicable to this type of experimental flow configuration, (2) data presented as the axial decay of centerline velocity and jet half-radius, are consistent and similar to past experimental data, mostly of gas jets, and (3) radial profiles show agreement with a past correlation up to R/R 1/2 > 1. There are differences however, between the correlation and the data, for R/R 1/2 > 1, the latter which were showed consistent trends.