Abstract
This research discusses the results of experiments performed on a large-scale gasification installation to determine the influence of total system pressure and partial pressure of CO2 on the efficiency of conversion and the quality of the produced gas. The three tested feedstocks were bark, lignin and a blend of bark and wheat straw, while softwood pellet (SWP) was used as a reference fuel. A mixture of O2/CO2/H2O was used as a gasification agent. The tests were devised to validate the previously proposed process parameters, verify whether similar ash agglomeration problems would occur and compare the thermal behaviour of the feedstocks converted in close-to-industrial process conditions. An understanding of the effect of using CO2 for gasification was further deepened, especially regarding its influence on the yield of H2 and temperature profiles of the fluidized bed. The influence of gasification pressure was predominantly visible in higher yields of all hydrocarbons (including CH4) and lower overall production of producer gas. At the process development unit (PDU), all tested feedstocks were converted at similar process conditions and no signs of potential bed agglomeration could be noticed. This opposes the findings observed in smaller-scale bubbling fluidized bed (BFB) tests. The discussion behind these discrepancies is also presented.
Highlights
Throughout the years, pressurized gasification has been treated as one of the most promising technologies for the conversion of primary, non-renewable feedstocks such as hard coals or lignites into chemical intermediates and fuels
The results presented hereafter should be viewed as taking into account the previous small-scale gasification experiments [27]
Small and large amounts of agglomerates observed in bed material recovered after the bark and lignin gasification runs, respectively; Fragmentation of fuel particles and a large amount of produced fines from gasification of bark and lignin leading to conversion losses; Increase in the intensity of agglomeration of the bed resulting from increasing streams of feedstocks leading to unstable gasification runs at higher pressures; Quick and uncontrollable defluidization and sintering of the bed upon changes of system pressure; Separation of size fractions of bed material inducing lower homogeneity of the temperature profile registered in-bed while leading to defluidization in the bubbling section
Summary
Throughout the years, pressurized gasification has been treated as one of the most promising technologies for the conversion of primary, non-renewable feedstocks such as hard coals or lignites into chemical intermediates and fuels. We observed the development of a couple of remarkable pressurized biomass gasification installations aimed at the production of renewable fuels and chemicals These actions were aligned with changing EU legislation and were highly supported by such esteemed bodies as the International Renewable Energy Agency and the International Energy Agency. These two institutions have indicated the following goals as priorities for broadening the scale of market uptake of biomass thermal conversion technologies, which is one of the keys for the opening opportunities regarding the decarbonization of our industries: To develop biomass-to-liquids (BtL) routes for the production of biodiesel and dimethyl ether (DME) from black liquor gasification; To maturate pressurized gasification plants to produce bio-synthetic natural gas (bio-SNG), as in the GoBiGas Phase 2 and E.ON Bio2G Project [1,2]; To study hybrid biochemical and thermochemical conversion routes
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