| 1. |
|
|
| 2. |
- Rydén, Magnus, 1975, et al.
(författare)
-
Fe2O3 on Ce-, Ca- or Mg-stabilized ZrO2 as oxygen carrier for chemical-looping combustion using NiO as additive
- 2010
-
Ingår i: AICHE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 56:8, s. 2211-2220
-
Tidskriftsartikel (refereegranskat)abstract
- Oxygen-carrier particles for chemical-looping combustion have been manufactured by freeze granulation. The particles consisted of 60 wt % Fe2O3 as active phase and 40 wt % stabilized ZrO2 as support material. Ce, Ca, or Mg was used to stabilize the ZrO2. The hardness and porosity of the particles were altered by varying the sintering temperature. The oxygen carriers were examined by redox experiments in a batch fluidized- bed reactor at 800–950°C, using CH4 as fuel. The experiments showed good reactivity between the particles and CH4. NiO was used as an additive and was found to reduce the fraction of unconverted CH4 with up to 80%. The combustion efficiency was 95.9% at best and was achieved using 57 kg oxygen carrier per MW fuel. Most produced oxygen carriers appear to have been decently stable, but using Ca as stabilizer resulting in uneven results. Further, particles sintered at high temperatures had a tendency to defluidize.
|
|
| 3. |
- Rydén, Magnus, 1975, et al.
(författare)
-
Ilmenite with addition of NiO as oxygen carrier for chemical-looping combustion
- 2010
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 89:11, s. 3523-3533
-
Tidskriftsartikel (refereegranskat)abstract
- The naturally occurring mineral ilmenite, FeTiO3, has been examined as oxygen carrier for chemical-loopingcombustion. NiO-based particles have been used as an additive, in order to examine if it is possible toutilize the catalytic properties of metallic Ni to facilitate decomposition of hydrocarbons into more reactivecombustion intermediates such as CO and H2. Firstly, ilmenite was examined by oxidation and reductionexperiments in a batch fluidized-bed reactor. These experiments indicated moderate reactivitybetween ilmenite and CH4, which was used as reducing gas. However, adding 5 wt.% of NiO-based particlesto the ilmenite improved the conversion of CH4 greatly, resulting in an increase in combustion efficiencywith a factor of 3. Secondly, 83 h of chemical-looping combustion experiments were conducted ina small circulating fluidized-bed reactor, using ilmenite as oxygen carrier and natural gas as fuel. A widerange of process parameters and different levels of NiO addition were examined. Occasionally, there wereproblems with the circulation of solids between the air reactor and fuel reactor, but most of the time theexperiments worked well. The products were mostly CO2, H2O and unconverted CH4. Adding smallamounts of NiO-based particles to the reactor increased the conversion of the fuel considerably. Forthe base case conducted at 900, the combustion efficiency was 76% for pure ilmenite and 90% for thecorresponding experiments with 1 wt.% NiO-based particles added to the reactor. The properties ofilmenite were found to change considerably during operation. Used particles had lower density, weremore reactive and more porous than fresh particles. These changes appear to have been physical, andno unexpected chemical phases could be identified.
|
|
| 4. |
- Rydén, Magnus, 1975, et al.
(författare)
-
Waste products from the steel industry with NiO as additive as oxygen carrier for chemical-looping combustion
- 2009
-
Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 3:6, s. 693-703
-
Tidskriftsartikel (refereegranskat)abstract
- Fe2O3-containing waste materials from the steel industry are proposed as oxygen carrier for chemical-looping combustion. Three such materials, red iron oxide, brown iron oxide and iron oxide scales, have been examined by oxidation and reduction experiments in a batch fluidized-bed reactor at temperatures between 800 and 950°C. NiO-based particles have been used as additive, in order to examine if it is possible to utilize the catalytic properties of metallic Ni to facilitate decomposition of hydrocarbons into more reactive combustion intermediates such as CO and H2. The experiments indicated modest reactivity between the waste materials and CH4, which was used as reducing gas. Adding small amounts of NiO-based particles to the sample increased the yield of CO2 in a standard experiment, typically by a factor of 1.5-3.5. The fraction of unconverted fuel typically was reduced by 70-90%. The conversion of CH4 to CO2 was 94% at best, corresponding to a combustion efficiency of 96%. This was achieved using a bed mass corresponding to 57 kg oxygen carrier per MW fuel, of which only 5 wt% was NiO-based synthetic particles. The different materials fared differently well during the experiments. Red iron oxide was fairly stable, while brown iron oxide was soft and subject to considerable erosion. Iron oxide scales experienced increased reactivity and porosity as function of the numbers of reduction cycles.
|
|
| 5. |
- Shulman, Alexander, 1978, et al.
(författare)
-
Chemical - Looping with oxygen uncoupling using Mn/Mg-based oxygen carriers - Oxygen release and reactivity with methane
- 2011
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 90:3, s. 941-950
-
Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion with oxygen uncoupling (CLOU) is a method for combustion of solid and gaseous fossil fuels, which enables easy separation of carbon dioxide from the gaseous product mixture. In contrast to the related chemical-looping combustion (CLC) technology where gaseous or gasified fuels react directly with oxygen carriers, CLOU processes require oxygen carrier materials to be able to release oxygen in the fuel reactor and to regenerate by re-oxidation in oxygen-rich atmosphere in the air reactor at elevated temperature. Oxygen uncoupling properties and reactivities for methane combustion of 12 oxygen carrier particles, produced from mixtures of manganese and magnesium oxides with optional addition of titanium dioxide or calcium hydroxide, are investigated in a quartz batch reactor at 810 degrees C, 850 degrees C, 900 degrees C and 950 degrees C. All investigated oxygen carriers have oxygen release characteristics. The addition of calcium hydroxide facilitates oxygen release and combustion of methane, whereas addition of titanium dioxide does not have a pronounced effect on either oxygen uncoupling or reactivity of the oxygen carrier. In general, particles with greater extent of oxygen release have superior methane combustion properties. (C) 2010 Elsevier Ltd. All rights reserved.
|
|
