After hardwork by Dynamis‘ R&D department, our bubbling type Fluidized Bed Hot Gas Generator is in operation, our D-FBed Chamber, at Votorantim, dedicated to the new cement mill at the Pecém plant, providing heat input necessary for cement drying and grinding system.
Its principle is to use an inert material (such as sand) to support combustion, providing a very high thermal inertia, leaving the system very stable, even with variations in fuel characteristics, whether in moisture or its LHV (lower heating value). One of the characteristics of a fluidized bed system for the application is the flexibility of the fuels used, whether traditional fuels such as coke or coal or lower cost fuels, such as biomass or alternative fuels, enabling an intelligent strategy for the plant, allowing it to plan with the offers of the cheapest fuels available in a spot demand, or taking advantage of the seasonality of a specific fuel, always using fuels with high granulometry, without the need to grind them, another important advantage for operational costs. Such features certainly make it the best option in terms of OPEX and competitiveness of your product.
The hot gas generation system was designed to operate continuously, with thermal loads between 4 Gcal/h and 12 Gcal/h and with three fuel types (petroleum coke, coal and wood chips), operating with part of the recirculated and diluted gases generated. Below are some characteristics of the Dynamis system and the construction components of its combustion chamber:
| PARAMETERS | VALUE |
| Nominal capacity | 12 Gcal/h |
| HGG fuels | Coal or petcoke (< 30 mm)Biomass (< 50 mm) |
| Heating Fuel | Diesel Oil |
| Hot Gas Temperature | 800 – 900°C |
| Hot Gas Flow Generated | 30.000 – 43.200 kg/h |
| Expected pressure at the mill | -50 mm c.a. |
The system is composed of a hopper located in the fuel storehouse that feeds the combustion chamber system (see detail in the figure below) by a belt conveyor, being monitored by a detector and metal separator. Depending on the characteristics of the plant and the fuels to be used, alternatives can be considered in future projects, with a bucket elevator, replacing the belt conveyor, leaving a smaller footprint.
The system is controlled automatically or manually, according to the exhaust gas temperature of the cement mill. The control variables are the rotations of the screw conveyors, for each type of fuel with its pre-defined operations. Additionally, the system also controls the minimum and maximum operations of all equipment, the temperature and internal pressure of the combustion chamber, the bed height and the recirculation gases or the fresh air injection for dilution air.
For start-up, the fluidized bed system has Dynamis burners, symmetrically distributed, featuring a high-quality combustion air injection system, with stainless steel nozzles specially designed to have a long service life and maximize fluidization efficiency. It is also necessary to fill the ash bottom with an inert fluidizing bed, in this case with the application of sand with own specifications for the application.
The operation process of the D-FBed Chamber is simple: after heating the chamber and bed, the system is able to receive the fuel in the fluidized bed. From this stage, there is a strict control of the bed, so as not to increase its fluidization speed so that the dragging of particles from the bed via pneumatic transport does not occur. Under the conditions of minimum temperature required by the fuel, the fuel injection process is then started until full load and its regular operation.
The D-FBed Chamber was designed to work with high availability and reliability, eliminating shutdowns for cleaning, with the removal of ash or addition of sand as fluidizing material during regular operation, being able to carry out maintenance according to the shutdown schedule of your plant. Another highlight and unique point of the Dynamis project is the recirculation of part of the hot gases generated, in a 100% automatic setup, operating with the hot gas temperature control mesh, thus avoiding an excessive use of dilution air with cold air, being more efficient from an energy point of view (reducing the flow of discarded gases by the cement grinding chimney) and enabling high turndown, an operation in lower capacity, if necessary.
Dynamis, a company dedicated to innovation in the studies of industrial processes and combustion equipment, developing its projects with the most modern technology, and our new project for the hot gas generation system in a fluidized bed is another success project of our technology, with the satisfaction expressed in a quick and successful startup and operation.
The next steps of the system that Dynamis is presenting is the use of the fluidized bed D-FBed Chamber technology for gasification and the use of new fuels as alternative solid and waste fuels and operation with more diversity of biomass, in the generation of SynGas in the production application clinker or even calcined clay, all so that our customers can arrive at a zero-carbon plant, neutralizing the plant’s greenhouse gas emissions.
Team Dynamis