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Funke A.,Karlsruhe Institute of Technology | Niebel A.,Karlsruhe Institute of Technology | Richter D.,Karlsruhe Institute of Technology | Abbas M.M.,Karlsruhe Institute of Technology | And 6 more authors.
Bioresource Technology | Year: 2016

Experiments with a process development unit for fast pyrolysis of biomass residues of 10kgh-1 have been performed to quantify the impact of two different product recovery options. Wheat straw, miscanthus and scrap wood have been used as feedstock. A separate recovery of char increases the organic oil yield as compared to a combined recovery of char and organic condensate (OC). Furthermore, it allows for an alternative use of the byproduct char which represents an important product fraction for the high ash biomass residues under consideration. The char produced shows little advantage over its biomass precursor when considered as energy carrier due to its high ash content. Significant value can be added by demineralizing and activating the char. The potential to increase the economic feasibility of fast pyrolysis is shown by an assessment of the bioliq® process chain. © 2015 Elsevier Ltd. Source


Beisheim T.,Institute of Combustion and Power Plant Technology | Zieba M.,Institute of Combustion and Power Plant Technology | Scheffknecht G.,Institute of Combustion and Power Plant Technology
Energy Procedia | Year: 2013

Applying the oxyfuel process to the circulating fluidized bed technology, one of the major process concerns is the possible deposit formation on the immersed surfaces of the external heat exchangers caused by the recarbonation of unused calcined desulphurization sorbent (CaO). This paper presents first results from experiments carried out under air- And oxyfuel atmospheres in a lab-scale BFB of calcined limestone with an in-bed cooled deposition probe. It was found, that under oxyfuel conditions, the strong recarbonation of calcined particles on the cool surface lead to hard and stable carbonate depositions. Source


Babat S.,Institute of Combustion and Power Plant Technology | Sporl R.,Institute of Combustion and Power Plant Technology | Maier J.,Institute of Combustion and Power Plant Technology | Scheffknecht G.,Institute of Combustion and Power Plant Technology
Fuel Processing Technology | Year: 2016

Fouling and slagging depend upon the boiler and firing system design, operational parameters and fuel properties. Release of inorganic compounds during combustion and their transformation into critical gaseous species, aerosols and ash particles may substantially affect the boiler efficiency and availability, due to the formation of fireside deposits. The composition of the mineral matter in three bituminous coals and the associated deposits formed at the inlet of the superheater level in a 730 MWth pulverized fuel boiler are discussed in this paper. A cooled probe was used to investigate the initial layer of the deposits while an uncooled probe was used to investigate the outer layer. In all initial layers, spherical (formerly molten) iron-rich particles, likely derived from pyrite were observed. Moreover, particles in the initial layers and mineral phases of the coal samples were determined quantitatively. Based on these analyses thermo-chemical equilibrium calculations were performed using the FACT-Sage simulation software to identify the effect of reducing and oxidizing flue gas atmospheres on the ash melting behavior and to assess their importance on the build-up of the initial deposit layers. The results of this work indicate that the deposition of an ash particle is strongly influenced by the particle's history. Besides its composition, in particular, temperature, and the atmosphere that a particle passes through have a significant influence on the mineral transformation and the adhesion of the particle. © 2015 Elsevier B.V. Source


Paneru M.,Institute of Combustion and Power Plant Technology | Babat S.,Institute of Combustion and Power Plant Technology | Maier J.,Institute of Combustion and Power Plant Technology | Scheffknecht G.,Institute of Combustion and Power Plant Technology
Fuel Processing Technology | Year: 2016

Biomass boiler issues regarding slagging, fouling and corrosion are related to alkali species present in fuels. These alkali species are released as gaseous alkali chlorides, hydroxides and/or sulfates during combustion. Alkali chlorides/sulfates later condense on cold boiler surfaces enhancing fouling and corrosion. Subsequent deposition of silica-rich ashes leads to the formation of low temperature melting eutectics, especially alkali/earth alkali-silicates (K/Ca-Si), and creates compact and strong deposits. Condensing chlorides/sulfates and low melting eutectics both reduce boiler performance and its availability. Two different woody biomass fuels and their mixture with two different kinds of aluminosilicate base additives were combusted during this study. Deposits were sampled using two different kinds of probes; cooled deposit probe and un-cooled deposit probe. The macroscopic and microscopic observations and chemical composition of deposit samples are compared using electron microscopic image analysis (EMPA) for both deposit samples. The additive significantly changes the morphology and composition of the deposit samples. The difference in morphology and composition can be explained by the change in potassium chemistry between two cases. © 2015 Elsevier B.V. Source


Sporl R.,Institute of Combustion and Power Plant Technology | Paneru M.,Institute of Combustion and Power Plant Technology | Babat S.,Institute of Combustion and Power Plant Technology | Stein-Brzozowska G.,Institute of Combustion and Power Plant Technology | And 2 more authors.
Fuel Processing Technology | Year: 2016

This article summarizes the results on the influence of combustion conditions (air, oxy-fuel) on deposit and ash formation and transformation and their implications on plant operation. The investigations involved thermodynamic equilibrium simulations as well as experiments at IFK's 20 kWth and 0.5 MWth combustion test rigs and Vattenfall's 30 MWth oxy-fuel pilot plant "Schwarze Pumpe". Comparative air and oxy-fuel experiments with Lusatian lignite showed a considerable increase of sulfur in ash and deposits and a 12 percentage point lower sulfur release to SO2 in oxy-firing. One reason for this is the higher SO2 partial pressure in oxy-fuel combustion that stabilizes sulfates. Therefore, sulfates can form at higher temperatures and more extensively. Oxy-fuel deposits may be more sintered by sulfates and therefore more difficult to remove by soot blowing. However, the experimental and theoretical considerations presented here support the conclusion that SO2 levels and therefore sulfate stability in oxy-fuel combustion of low sulfur coals is comparable to conditions experienced in air-firing of high sulfur fuels. Thus, it can be expected that problems associated with sulfatic deposits (e.g.: fouling) in low sulfur coal oxy-fuel combustion can be handled by standard techniques (e.g. soot blowing). For high sulfur fuels with considerable sulfur capture potential (e.g.: high Ca), this may not be true and additional measures may be required for a reliable plant operation. © 2015 Elsevier B.V. Source

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