The main target of my project was to investigate the behaviour of lignocellulosic waste before and after conventional pre-treatment of leaching, A method used in the past for coal. A Fluidized bed used for thermochemical studies of combustion, gasification and pyrolysis at different temperatures ranging from 750-950oC. The reactivity and the bed agglomeration were studied for straw/forest biomass waste in both batch and continuous mode. Both wood and barley straw were used in the experiments to understand the biomass type’s behaviour during thermochemical treatments. Leaching pre-treated the biomass was carried out by using deionized water and tap water. The key result of the pre-treatment was the alkali and the alkali earth metals content in the biomass decreased by over 60%.
The VTT facilities and equipment was highly organized, well equipped and had excellent preparation for carrying out experiments in fluidized bed reactors both in continuous and batch mode. The fluidized bed reactors used for bioenergy production and the main products are gases such as H2, CO, CO2, CH4 , C2H6 and as well others. The workplace environment is flexible with a nice atmosphere and the people were really very helpful and supportive. Their bench scale Bubbling Fluidized Bed (BFB) system has an electrical temperature stabilization and control with also primary and secondary gas feeds with varying gas compositions (air and mixed gases O2, CO2, CO, SO2, NO etc.). The gas products can be analysed by using FTIR with gas analyser with function of time and temperature.
Pyrolysis, combustion and gasification conditions were applied in the batch operation for better understanding the effects of the hypo-stoichiometric oxygen level (ranging from 0-10%) on the reactivity of the biomass waste and products with a batch feed of less than 1g of sample for each run. Both treated and untreated biomass waste were used in batch mode to determine the effect of pre-treatment of leaching in the reactivity of the biomass waste under different conditions.
The continuous test was carried out under gasification conditions (limited oxygen content) at different temperatures, using both untreated and pre-treated barley straw. The aim of this test was to determine the reactivity of this straw waste, rich in ash, in continuous operation and investigate the risk of bed agglomeration phenomena. At the end of each test, the bed materials were collected for further analysis by XRD and XRF for determining the composition of the residues and bed agglomeration constituents. In addition, microscope images were taken for bed materials all the continuous tests for biomass before and after pre-treatment at different temperatures.
Continuous tests for untreated barley straw showed that as the temperature of the reactor increased, the bed agglomeration takes place faster, detected a collapse of the reactor bed pressure due to formation high agglomerated content in (20-40 mins) by feeding (4-9 g) of untreated barley straw. However, pre-treated barley straw samples didn’t form any agglomerates and the bed pressure was stable for a longer time (60-80 mins) by even feeding around (21-23 g) of pre-treated by leaching treated barley straw. As a result, leaching of this type of rich in ash biomass with water reduced the risk of the agglomeration and improved the stability of the reactor operating conditions (pressure and temperature). In addition, pre-treated biomass produced slightly higher amount of gases such as CH4, CO2 and H2 as determined from FTIR analysis. In conclusion, pre-treatment of barley straw which has a higher ash content than other straws in UK ,there were a reduction in the risk of the bed agglomeration, improvement the stability of the process and enhancement the gases products in both continuous and batch operations.
For me applying to the BRISK2 projects was a great opportunity to learn and explore new ideas and applications in my field. This project was very fruitful, enhanced my knowledge and proved very helpful for continuation of my PhD study in the field of biomass waste pre-treatments for downstream thermochemical treatment routes. It was a really nice experience and great opportunity to follow the transitional access to VTT via BRISK2 which helped me understand and learn different applications and methods about the thermochemical processes by being trained in bench scale thermochemical reactors in both continues and batch mode.