[en] The RAFAKO Boiler Engineering Company offer of standard and circulation fluidized bed boilers, developed in response to the market demand, is presented. The technology for wet and semi-dry flue gas desulfurization is also included in the offer

[en] The fundamental aim of this work is biomass utilization for gas production, which will be used ecologically and with efficiency for obtaining energy. For this reason, a pilot plant was constructed for biomass gasification in a fluidized bed reactor. The practical solution to fluidization of inert material, to fuel supplying, to ash removing and the system for analyzing of produced gas, were presented. The pilot plant is tested on rise hulls from the Kocani region and the fluidization was carried out with air under pressure and the quartz sand was used as inert material. The influence of the temperature and the height of fluidized bed on the minimum fluidized velocity was examined in different working conditions. Also, the influence of the working parameters (granulation and height of the inert bed material, pressure of the gas for fuel supply and the fuel supply) on the composition of gas produced by gasification, was examined. Mathematical model for the complete process was developed and all material flows were calculated. According to the calculated coefficient of over air it can be concluded that the process is carried out with partial fuel combustion i.e. the process of gasification is performed in the reactor. From the obtained results and their analyses, it can be generally said that the aim of this doctoral thesis is accomplished. (Author)

[en] A scheme of two stage fluidized combustion is proposed in order to increase the electricity production efficiency. The first combustion stage is performed in the reactor, where due to air feed less than the amount necessary for complete combustion. The output combustible components such as CO and H₂ are fed in the gas turbine. In the combustion facility before the gas turbine these components burn out with the necessary air feed leading to a temperature increase to 1200-1300⁰C. The study shows that it is technically possible to construct such an installation. The use of the lignite coal from 'Maritsa Iztok' requires additional desulfurization. The desulfurization in the pressurized fluidized boilers is lower than one in the conventional fluidized boilers. The flue gases contain more CaSO₄ and CaS (CaSO₄ increase for lower temperatures)

[en] This article gives a survey of the gasification techniques, power plant technology and boiler solutions for small power plants using biofuels. Also some experiences from commercial projects and targets of development work are presented. At present, fluidized bed combustion is by far the most important combustion technique for biomass fuels in small power plants. Compared with grate combustion, fluidized bed combustion is a distinctly more economical combustion method, and so the thermic dimensioning of a steam boiler is easier. Besides, a wider range of fuels can be used in fluidized bed combustion. Fluidized bed combustion is an excellent combustion technique for biofuels. Plenty of experience has been gained in the combustion of peat and industrial waste wood, as far as both bubbling fluidized bed combustion (BFBC) and circulating fluidized bed combustion (CFBC) are concerned. Both of the fluidized bed techniques are suitable for the combustion of biomasses

[en] Highlights: • Autothermal pyrolysis provides energy for process through partial oxidation. • Overcomes heat transfer bottleneck of pyrolysis allowing process intensification. • Limitations of previous studies overcome by accounting for parasitic heats losses. • Autothermal operation does not substantially reduce bio-oil yield. • Biomass throughput increased three-fold using autothermal operation. -- Abstract: Heat transfer is the bottleneck to fast pyrolysis of biomass. Although the enthalpy for pyrolysis of biomass is relatively small operation at temperatures around 500 °C constrains heat carrier selection to inert gases and granular media that can sustain only modest thermal fluxes in practical pyrolysis systems. With heat transfer controlling the rate of pyrolysis, reactor capacity only scales as the square of reactor diameter and does not benefit from economies of scale in building larger reactors. We have eliminated this heat transfer bottleneck by replacing it with partial oxidation of pyrolysis products to provide the enthalpy for pyrolysis in a fluidized bed reactor, a process that can be described as autothermal pyrolysis. The oxygen-to-biomass equivalence ratio depends upon the kind of biomass being pyrolyzed and the level of parasitic heat losses from the reactor, but under conditions that simulate adiabatic operation, equivalence ratios are around 0.10, compared to 0.20 or higher for autothermal gasifiers. At this low equivalence ratio, there was no significant loss in bio-oil yield when operating the reactor autothermally (64.8 wt%) as compared to conventional pyrolysis (64.4 wt%). Carbon balances indicate that less valuable pyrolysis products (char and aqueous, bio-oil light ends) are consumed via partial oxidative reactions to provide the enthalpy for pyrolysis. While the carbon yields of char and bio-oil light ends decreased by 25.0% and 21.3%, respectively, the most valuable pyrolysis product (bio-oil heavy ends) only decreased 8.0%.

[en] For experimental studies of Bulgarian coal behaviour in fluidized bed combustion (FBC) conditions, the bench scale fluidized bed reactor has been used, designed and built by specialists from the Institut fur Energietechnik UGH-Siegen. The dynamical characteristics of the FBC system have been calculated on the base of the experimental results. The process of modelling consists of: 1) Modelling of the channels 'mass of the coal - results from the measuring system'; 2) Measuring systems dynamic characteristics modelling; 3) Obtaining of the FBC system dynamic characteristics; 4) Determination of the reaction processes of the FBC system on the base of the developed models. The comparative analyses of CO and CO₂ formation and O₂ reduction during the combustion of the coal particles (under different combustion conditions) lead to the following conclusions: 1) The combustion of the smaller particle size coal (mean D_p=1.5 mm) is characterized with: fast and intensive process of CO formation (the CO quantity is about 2 times more compared to that for particle size D_p=4.2 mm); smaller formation (quantitative and maximal CO₂ concentration), compared to the bigger size; less O₂ consumption, because of the unfinished carbon oxidation; the combustion time of the smaller particles is about 15-20 seconds shorter. 2) The better quality Bulgarian coal (with less ash content) contains more fixed carbon which could explain the obtained results: better total ratio CO/CO₂; higher CO₂ formation and O₂ consumption; longer combustion time. 3) Bulgarian lignite coal has relatively short combustion time (50-70 seconds). The test results can be used as a base for the followed analyses connected with determination of the gas formation dynamics for different sorts of lignite coal; comparative analyses for Bulgarian coal, and other types of fuel

[en] Design, modeling and simulation of fluidized bed risers and reactors depend strongly on the knowledge, operational and hydrodynamic characteristics. In this study effort has been made to describe fluidization phenomenon and its application in fluidized beds is briefly explained. The bubble fluidized bed reactors will be introduced and the computerized calculation needed for simulating of a fluidized bed riser with 0.3m diameter and 5 m height will be given. The effect of bed height on the bubble diameter and mass transfer area is calculated and the result are discussed. Operational; conditions of the bed, type and characteristics of the catalyst, has been selected so to suit the production of Maleic Anhyd ric from the n-Butane oxidation

[en] The present work investigates the heat transfer between the immersed heater and bed and hydrodynamics of the bed in swirling fluidized bed. The heat transfer process and bed hydrodynamics characteristics for swirling fluidized bed reactor (SFBR) were compared to those of conventional fluidized bed reactor (CFBR). Then the influence of particle diameter on the bed flow characteristics and heat transfer process in SFBR were studied. The heat transfer coefficient was calculated at different superficial air velocities, radial positions, and bed heights. Compared to a CFBR, the bed pressure drop and distributor pressure drop for SFBR were lower, that characterizes swirling bed reactor. The heat transfer coefficient of SFBR was higher than the corresponding of CFBR at lower portion of the bed and it was lower at the upper portion of the bed for all radial positions and for all air superficial velocities. Increasing particle diameter in SFBR resulted in decreasing both the heat transfer coefficient and bed pressure drop.

[en] Based on the conducted experiment for lignite from 'Maritsa Iztok' fluidized bed combustion, an analysis is done of the impact of different fuel parameters (diameter of coal particles; bed temperature; ash content of the coal particles, oxygen content of the fluidized agent ) on NOx emissions

[en] The present goal for preparation of (U,Pu)C is a high-purity product to demonstrate the feasibility of the fluidized-bed process. A secondary objective of the experiments is to obtain material for irradiation testing. A helium-atmosphere glovebox system for this work has recently been completed and tested. The two gloveboxes which house the reactor system are shown in Figure III-7. The gloveboxes have a total volume of about 250 cu ft and are equipped with 52 gloveports. Other features include an interconnecting transfer lock, a vacuum lock containing a plutonium bagout mechanism, and several other mechanisms for ingress and egress of materials.