Hüsnü Atakül

Removal of H2S from fuel gases at high temperatures using MnO/γ-Al2O3

Abstract High temperature desulfurization of gases from coal gasification processes has important aspects for many industrial applications and electrical power generation plants. MnO, supported by γ-Al 2 O 3 (MnO/γ-Al 2 O 3 ), was used as a regenerable sorbent for high temperature removal of H 2 S from gases. The sorbent was prepared by wet impregnation and tested for successive sulfidation-regeneration cycles. Sulfidation was carried out at 600°C with an N 2 /H 2 /H 2 S mixture containing 1.41–4.48% H 2 S. Regeneration of the sorbent was performed with both N 2 /H 2 and N 2 /H 2 /steam mixtures at the same temperature. The sorbent can be completely regenerated with a gas-steam mixture, while only 25-20% of the sulfur can be removed by physical (N 2 /H 2 ) regeneration. The breakthrough and total capacities of the sorbent were found to be affected by the flow rate and the H 2 S concentration of the gas. Consumption of steam for regeneration increased slowly until 60–70% of the regeneration was completed, and then rose rapidly. The manganese conversion ranged from 15–19% at the breakthrough point, to 32–35% at the end of sulfidation (acceptation).

Regeneration of MnO/γ-Al2O3 used for high-temperature desulfurization of fuel gases

Abstract The regeneration of MnO/γ-Al 2 O 3 used as a sorbent to remove H 2 S from fuel gases was studied with a packed bed reactor. The sorbent was prepared by wet method in which MnO was impregnated onto a standard γ-Al 2 O 3 . The sorbent was regenerated at 600°C. The regenerating gas was a mixture of N 2 , H 2 and steam in various proportions. The N 2 -H 2 -steam mixture resulted in a complete regeneration of the sorbent. The composition of the reactor off-gas varied according to the regenerating gas composition. Under suitable conditions the concentration of H 2 S in the reactor off-gas was high enough for use to produce elemental sulfur.

Co-firing of pine chips with Turkish lignites in 750kWth circulating fluidized bed combustion system

Two Turkish lignites which have different sulfur levels (2-2.9% dry) and ash levels (17-25% dry) were combusted with a Turkish forest red pine chips in a 750kW-thermal capacity circulating fluidized bed combustor (CFBC) system. The combustion temperature was held at 850±50°C. Flue gas emissions were measured by Gasmet DX-4000 flue gas analyzer. Two lignites were combusted alone, and then limestone was added to lignites to reduce SO2 emissions. Ca/S=3 was used. 30% percent of red pine chips were added to the lignites for co-firing experiments without limestone in order to see the biomass effects. The results showed that with limestone addition SO2 concentration was reduced below the limit values for all lignites. CO emissions are high at low excess air ratios, gets lower as the excess air ratio increases. During co-firing experiments the temperature in the freeboard was 100-150°C higher as compared to coal combustion experiments.

Temperature profiles in a lignite flotsam-rich fluidized bed

Abstract Temperature measurements along the vertical axis of an 11 cm i.d. fluidized bed were successfully used to interpolate the segregation patterns for Can lignite burning in quartz sand. Using differential temperature data the lignite flotsam-rich type segregation patterns were investigated for changes in lignite type, bed materials, particle size, fluidization velocity and static dynamic bed heights. It is concluded that the quality of mixing deteriorates when the lignite particle size, the fluidization velocity and the length of static and dynamic bed heights are each decreased and ash content, density and particle size of bed material increased. These were in accordance with the behaviour of a flotsam-rich type system in which lignite was the flotsam component. In this study the effect of volatile matter content on freeboard combustion was found to be unimportant compared with the effect of changes in the segregation patterns.

Synthesis of carbon foam with high compressive strength from an asphaltene pitch

Carbon foams were synthesized using an asphaltene pitch as a carbon precursor. The effects of foaming conditions and carbonization on the pore structures and physical properties of the carbon foams were investigated. Results indicate that the average pore size and density of as-synthesized carbon foams were about 150 μm and 800 kg/m3, respectively. The compressive strength of the carbon foam increased from 10 to 18.7 MPa after carbonization at 1 323 K. The high ash content (41.76%) of the pitch plays an important role in determining the density and compressive strength of the carbon foams.