scholarly journals Experimental Investigation of Oxygen Carrier Aided Combustion (OCAC) with Methane and PSA Off-Gas

2020 ◽  
Vol 11 (1) ◽  
pp. 210
Author(s):  
Viktor Stenberg ◽  
Magnus Rydén ◽  
Tobias Mattisson ◽  
Anders Lyngfelt
Keyword(s):  
Oxygen Carrier ◽  
Silica Sand ◽  
Fuel Conversion ◽  
Fuel Gas ◽  
Bed Temperature ◽  
Bed Materials ◽  
Distribution Plate ◽  
Bed Material ◽  
Gas Conversion ◽  
No Emissions

Oxygen carrier aided combustion (OCAC) is utilized to promote the combustion of relatively stable fuels already in the dense bed of bubbling fluidized beds by adding a new mechanism of fuel conversion, i.e., direct gas–solid reaction between the metal oxide and the fuel. Methane and a fuel gas mixture (PSA off-gas) consisting of H2, CH4 and CO were used as fuel. Two oxygen carrier bed materials—ilmenite and synthetic particles of calcium manganate—were investigated and compared to silica sand, an in this context inert bed material. The results with methane show that the fuel conversion is significantly higher inside the bed when using oxygen carrier particles, where the calcium manganate material displayed the highest conversion. In total, 99.3–99.7% of the methane was converted at 900 °C with ilmenite and calcium manganate as a bed material at the measurement point 9 cm above the distribution plate, whereas the bed with sand resulted in a gas conversion of 86.7%. Operation with PSA off-gas as fuel showed an overall high gas conversion at moderate temperatures (600–750 °C) and only minor differences were observed for the different bed materials. NO emissions were generally low, apart from the cases where a significant part of the fuel conversion took place above the bed, essentially causing flame combustion. The NO concentration was low in the bed with both fuels and especially low with PSA off-gas as fuel. No more than 11 ppm was detected at any height in the reactor, with any of the bed materials, in the bed temperature range of 700–750 °C.

Rice Husk Combustion in a BFBC Using Porous Bed Material

2005 ◽  
Author(s):  
Tadaaki Shimizu ◽  
Takumi Nemoto ◽  
Hotaka Tsuboi ◽  
Toshio Shimoda ◽  
Syunji Ueno
Keyword(s):  
Rice Husk ◽  
Porous Alumina ◽  
Silica Sand ◽  
Stable Operation ◽  
N2o Emissions ◽  
Nox Emissions ◽  
Bed Materials ◽  
Average Size ◽  
Bed Material ◽  
Fluidized Bed Combustor

Rice husk was burned in a bench-scale fluidized bed combustor (53 mm I.D. and 1.3m height) at 1123 K. Silica sand (average size 0.27 mm) was employed as conventional bed material. As an alternative bed material, a kind of porous alumina (average size 0.69 mm) was employed. Unburned gas (CO) emissions were suppressed by employing porous alumina as bed material. NOx emissions from the alumina bed were also suppressed in comparison to the sand bed. N2O emissions were nearly negligible (less than 10 ppm) for both bed materials. During combustion in the sand bed, sudden temperature rise up to 1450 K and increase in pressure drop across the bed were observed. Agglomerates were found in the bed material after the experiments. For the porous alumina bed, such agglomeration trouble did not occur. As conclusion, the present porous alumina was effective for both reduction of pollutants emissions and stable operation.

scholarly journals Effect of Bed Material on Bed Agglomeration for Palm Empty Fruit Bunch (EFB) Gasification in a Bubbling Fluidised Bed System

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4336 ◽  
Author(s):  
Tanakorn Kittivech ◽  
Suneerat Fukuda
Keyword(s):  
Silica Sand ◽  
Empty Fruit Bunch ◽  
Fluidised Bed ◽  
Suitable Alternative ◽  
Heating Value ◽  
Product Gas ◽  
Bed Materials ◽  
Bed Agglomeration ◽  
High Level ◽  
Bed Material

The high level of potassium compounds in Empty Fruit Bunch (EFB) induces ash-related problems, such as bed agglomeration, which is caused by the formation of a low-melting-point sticky compound: K2On·SiO2, especially in fluidised bed gasification using silica sand as bed material. Dolomite was found to be an effective alternative bed material for preventing bed agglomeration by the release of CaO via calcination processes during gasification. CaO acts as a catalyst to inhibit bed agglomeration by possibly enhancing the formation of K2CO3 instead of K2O·nSiO2. Alumina sand was also found to be a suitable alternative bed material to prevent bed agglomeration; however, due to the relatively high density of alumina sand, high gas velocity was needed to ensure good mixing and fluidisation. Using both dolomite and alumina sand as bed materials yielded a product gas having similar higher heating value (HHV) to that when using silica sand (i.e., 3.8–3.9 MJ/Nm3).

scholarly journals Oxygen Carrier Aided Combustion (OCAC) of Wood Chips in a 12 MWth Circulating Fluidized Bed Boiler Using Steel Converter Slag as Bed Material

2018 ◽  
Vol 8 (12) ◽  
pp. 2657 ◽  
Author(s):  
Magnus Rydén ◽  
Malin Hanning ◽  
Fredrik Lind
Keyword(s):  
Fluidized Bed ◽  
Alkali Metals ◽  
Circulating Fluidized Bed ◽  
Converter Slag ◽  
Oxygen Carrier ◽  
Point Of View ◽  
Wood Chips ◽  
Silica Sand ◽  
Ld Slag ◽  
Bed Material

The novel combustion concept Oxygen Carrier Aided Combustion (OCAC) is realized by addition of an active oxygen-carrying bed material to conventional fluidized bed boilers. The active bed material is meant to become reduced in fuel-rich parts of the boiler and oxidized in oxygen-rich parts, thus potentially providing advantages such as new mechanisms for oxygen transport in space and time. In this study, oxygen-carrier particles prepared from so called Linz-Donawitz (LD)-slag are examined as active bed material in a 12 MWth Circulating Fluidized Bed (CFB) boiler. LD-slag is the second largest by-product in steel making and is generated in the basic LD oxygen converter process. The experimental campaign lasted for two full weeks. The fuel was wood chips. LD-slag worked well from an operational point of view and no problems related to handling, agglomeration or sintering were experienced, albeit the production of fly ash increased. The boiler temperature profile suggested that fuel conversion in the main boiler body was facilitated, but the effect did not readily translate into reduced emissions from the stack. Spraying an aqueous solution of ammonium sulphate directly into the cyclone outlet with the aim of rejecting alkali metals as alkali suphates was found to solve the problems related to carbon monoxide emissions, suggesting that the problems could be due to the poor ability of LD-slag to absorb certain ash components. Use of a mixed bed consisting of 10–50 wt% LD-slag, with the remaining part being silica sand for ash absorption, also worked well. It is concluded that LD-slag could be a very cheap and readily available oxygen-carrying bed material for use in fluidized bed applications.

scholarly journals Mapping the Effects of Potassium on Fuel Conversion in Industrial-Scale Fluidized Bed Gasifiers and Combustors

Catalysts ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1380
Author(s):  
Teresa Berdugo Vilches ◽  
Jelena Maric ◽  
Henrik Thunman ◽  
Martin Seemann
Keyword(s):  
Fluidized Bed ◽  
Silica Sand ◽  
Fuel Conversion ◽  
Comprehensive Overview ◽  
Char Gasification ◽  
Gasification Rate ◽  
Catalytically Active ◽  
Dual Fluidized Bed ◽  
Bed Agglomeration ◽  
Bed Material

Potassium (K) is a notorious villain among the ash components found in the biomass, being the cause of bed agglomeration and contributing to fouling and corrosion. At the same time, K is known to have catalytic properties towards fuel conversion in combustion and gasification environments. Olivine (MgFe silicate) used as gasifier bed material has a higher propensity to form catalytically active K species than traditional silica sand beds, which tend to react with K to form stable and inactive silicates. In a dual fluidized bed (DFB) gasifier, many of those catalytic effects are expected to be relevant, given that the bed material becomes naturally enriched with ash elements from the fuel. However, a comprehensive overview of how enrichment of the bed with alkali affects fuel conversion in both parts of the DFB system is lacking. In this work, the effects of ash-enriched olivine on fuel conversion in the gasification and combustion parts of the process are mapped. The work is based on a dedicated experimental campaign in a Chalmers DFB gasifier, wherein enrichment of the bed material with K is promoted by the addition of a reaction partner, i.e., sulfur, which ensures K retention in the bed in forms other than inactive silicates. The choice of sulfur is based on its affinity for K under combustion conditions. The addition of sulfur proved to be an efficient strategy for capturing catalytic K in olivine particles. In the gasification part, K-loaded olivine enhanced the char gasification rate, decreased the tar concentration, and promoted the WGS equilibrium. In the combustion part, K prevented full oxidation of CO, which could be mitigated by the addition of sulfur to the cyclone outlet.

Operational Performance and Optimization of a 465t/h CFB Boiler in China

2005 ◽  
Author(s):  
Xinmu Zhao ◽  
Junfu Lu ◽  
Jianhua Yang ◽  
Qingguo Zhang ◽  
Fengliang Dong ◽  
...  
Keyword(s):  
Circulating Fluidized Bed ◽  
Bottom Ash ◽  
Heating Surface ◽  
Gas Temperature ◽  
Fuel Gas ◽  
Future Design ◽  
Bed Temperature ◽  
The Future ◽  
And Performance ◽  
Bed Material

In the last three years in China, more than 80 units of 135MWe circulating fluidized bed (CFB) boilers were ordered, and about two dozens of them have been put into operation. So far, the experience and performance evaluation of the boilers with such large capacity are very limited. A series of cold and hot tests were carried out on the boiler in order to optimize the operation and provide more information to the future design. The influence of coal properties, bed material fluidization, air distribution, bed temperature and pressure drop on the boiler performance such as carbon content in fly ash was assessed and discussed. Some problems of the boiler, including the bottom ash system, milling system, abrasion of the heating surface in the furnace, refractory stability, and exhaust fuel gas temperature are reported and suggestions are given for the future improvement and design.

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.

Relationship Between Feedstock Characteristics and Erosivity of FBC Bed Materials

1992 ◽  
Vol 114 (1) ◽  
pp. 145-151
Author(s):  
A. V. Levy ◽  
B. Q. Wang ◽  
G. Q. Geng
Keyword(s):  
Heat Exchangers ◽  
Major Effect ◽  
Plain Carbon Steel ◽  
Sand Content ◽  
Degradation Mechanisms ◽  
Sharp Transition ◽  
Fluid Bed ◽  
Alkali Compounds ◽  
Bed Materials ◽  
Bed Material

The erosion-corrosion (E-C) metal wastage mechanisms and rates that occur in 1018 plain carbon steel used in tubular heat exchangers of fluid bed combustors (FBC) are discussed. The characteristics of FBC bed material erodent particles such as composition, shape, size, and strength were found to have a major effect on the surface degradation mechanisms and rates that occurred. A total of 16 different bed material particles from ten different FBCs were tested. It was determined that when the particles were strong enough not to shatter when they impacted the steel’s surface, their shape and composition were the most important factors in determining their erosivity. The relative amounts of SiO2, CaO, CaCO3, CaSO4, and alkali compounds in the bed materials were related to the metal wastage by using laboratory mixtures of the compounds as erodents. The ratio of SiO2 to CaO and CaCO3 was especially important in determining the erosivity of the bed materials. It was found that increasing this ratio increased the metal wastage. A sharp transition ratio occurred on either side of which the metal wastages were linear. The slope of the linear curve was low for the lower sand content mixtures and higher for higher sand content mixtures. The transition ratio required a higher CaO content for higher velocity particles.

Icequake streaks linked to potential mega-scale glacial lineations beneath an Antarctic ice stream

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 99-102
Author(s):  
C. Grace Barcheck ◽  
Susan Y. Schwartz ◽  
Slawek Tulaczyk
Keyword(s):  
Mechanical Properties ◽  
Spatial Distribution ◽  
High Porosity ◽  
Back Projection ◽  
West Antarctica ◽  
S Wave ◽  
Frictional Properties ◽  
Ice Stream ◽  
Bed Materials ◽  
Bed Material

Abstract Icequakes radiating from an ice-stream base provide insights into otherwise difficult to observe sub-kilometer-scale basal heterogeneity. We detect basal icequakes beneath an ∼3-km-wide seismic sensor network installed on the Whillans Ice Plain (WIP) in West Antarctica, and we use S-wave back-projection to detect and locate thousands of basal icequakes occurring over 14 and 21 days in January 2014 and 2015, respectively. We find flow-parallel streaks of basal icequakes beneath the WIP, which we conjecture are related to the presence of mega-scale glacial lineations (MSGLs) indicated by ice-penetrating radar, with at least one streak originating in a local trough adjacent to a MSGL. Patterned basal seismicity can be caused by systematic spatial variation in basal pore pressure, bed-material frictional properties, or both. We interpret these flow-parallel icequake streaks as being due to frictionally heterogeneous bed materials in the presence of a streamlined ice-stream bed: bedform ridges correspond to aseismic, high-porosity deforming till, and some troughs to ephemeral exposures of deeper, seismogenic material such as lodged till or older sediments or rocks. Our results are consistent with MSGL formation by either erosion in troughs to expose deeper seismogenic material, or deposition of aseismic high-porosity till in bedform highs. Our results also suggest that evolving subglacial geomorphology can impact basal traction by reorganizing the spatial distribution of basal materials with varying mechanical properties.

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