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 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.

Pengurangan Pelepasan Emisi dari Pembakar Lapisan Terbendalir Menggunakan Tempurung Kelapa Sawit Sebagai Bahan Api

2012 ◽  
pp. 07-11
Author(s):  
Mohammad Nazri Mohd Jaafar ◽  
Rosyida Permatasari ◽  
Mohd Nazar Yakin Mohd Sobree
Keyword(s):  
Fluidized Bed ◽  
Fuel Oil ◽  
Silica Sand ◽  
Nox Emissions ◽  
Fuel Feed ◽  
Bed Height ◽  
Excess Air ◽  
Axial Temperature ◽  
Fluidized Bed Combustor ◽  
Air Staging

Emissions released from fluidized bed combustor (FBC) are highly dependent on several operating parameters, for example, temperature, staged air, excess air, fuel feed rate, and fuel properties. This paper presents results of experiments conducted using air staging technique on a laboratory scale fluidized bed rig, using palm shells as fuel oil and silica sand as an inert medium. Silica sand was used to ensure a sustainable fuel ignition and stable combustion occurs in the FBC. Emission of CO and NOx emissions, and temperatures along the height of the bed and flue were measured. The experimental results show that the axial temperature profile along the height was proportionally reduced with bed height of FBC. CO and NOx emissions obtained exhibit lower values for the air staged combustion. Pelepasan emisi dari pembakar lapisan terbendalir (FBC) adalah sangat bergantung kepada beberapa parameter kendalian sebagai contoh: suhu, udara berperingkat, udara berlebihan, kadar suapan bahan api, dan sifat bahan api. Kertas kerja ini mempersembahkan keputusan eksperimen yang dilaksanakan menggunakan teknik pemeringkatan udara ke atas rig lapisan terbendalir skala makmal, menggunakan tempurung kelapa sawit sebagai bahan api dan pasir silika sebagai bahan perantara lengai. Pasir silica telah digunakan untuk memastikan pencucuhan bahan api mampan dan pembakaran stabil berlaku di dalam FBC. Pelepasan gas emisi CO dan NOx serta suhu sepanjang ketinggian pembakar dan juga dalam serombong diukur. Keputusan ujikaji menunjukkan bahawa profil suhu paksi berkurangan secara berkadaran sepanjang ketinggian FBC. Pelepasan CO dan NOx yang diperolehi mempamerkan nilai yang lebih rendah untuk keadaan pembakaran dengan pemeringkatan udara.

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 Evaluation of mechanical properties of porous alumina ceramics obtained using rice husk as a porogenic agent

Cerâmica ◽  
2019 ◽  
Vol 65 (suppl 1) ◽  
pp. 70-74 ◽  
Author(s):  
G. C. Ribeiro ◽  
B. A. Fortes ◽  
L. da Silva ◽  
J. A. Castro ◽  
S. Ribeiro
Keyword(s):  
Mechanical Properties ◽  
Rice Husk ◽  
Porous Alumina ◽  
Alumina Ceramics

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.

Lean Blowout Limit and NOx-Production of a Premixed Sub-ppm NOx Burner With Periodic Flue Gas Recirculation

2004 ◽  
Author(s):  
Jochen R. Kalb ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Flue Gas ◽  
Gas Content ◽  
Stable Operation ◽  
Reacting Flow ◽  
Nox Emissions ◽  
Lean Blowout ◽  
Fresh Mixture ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

The technological objective of this work is the development of a lean-premixed burner for natural gas. Sub-ppm NOx emissions can be accomplished by shifting the lean blowout limit (LBO) to slightly lower adiabatic flame temperatures than the LBO of current standard burners. This can be achieved with a novel burner concept utilizing periodic flue gas recirculation: Hot flue gas is admixed to the injected premixed fresh mixture with a mass flow rate of comparable magnitude, in order to achieve self-ignition. The subsequent combustion of the diluted mixture again delivers flue gas. A fraction of the combustion products is then admixed to the next stream of fresh mixture. This process pattern is to be continued in a cyclically closed topology, in order to achieve stable combustion of e.g. natural gas in a temperature regime of very low NOx production. The principal ignition behavior and NOx production characteristics of one sequence of the periodic process was modeled by an idealized adiabatic system with instantaneous admixture of partially or completely burnt flue gas to one stream of fresh reactants. With the CHEMKIN-II package a reactor network consisting of one perfectly stirred reactor (PSR, providing ignition in the first place) and two plug flow reactors (PFR) has been used. The effect of varying burnout and the influence of the fraction of admixed flue gas have been evaluated. The simulations have been conducted with the reaction mechanism of Miller and Bowman and the GRI-Mech 3.0 mechanism. The results show that the high radical content of partially combusted products leads to a massive decrease of the time required for the formation of the radical pool. As a consequence, self-ignition times of 1 ms are achieved even at adiabatic flame temperatures of 1600 K and less, if the flue gas content is about 50%–60% of the reacting flow after mixing is complete. Interestingly, the effect of radicals on ignition is strong, outweighs the temperature deficiency and thus allows stable operation at very low NOx emissions.

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