THE 500 kW SYNPET SOLAR GASIFICATION PLANT
The installation of the 500 kW Solar Gasification Plant on the top of the SSPS/CRS tower at the Plataforma Solar de Almeria is foreseen for the end of 2008. Manufacture of the solar-receiver was finished at the beginning of this year following the design of ETH. Rest of the components, including coke pneumatic transport, heat exchanger, torch, etc for upstream and downstream systems were defined by CIEMAT.
A gasification plant, by their nature, involves the processing of flammable gases, mists or vapors or by combustible dusts. In Europe, certification standards are now being put in place for these risk areas as part of the ATEX Directive. Under the associated ATEX 94/9/EC Directive limitations are dictated by the type of equipment that can be installed within the classified hazardous areas. Once an area has been identified as hazardous it should be classified into zones based on the frequency and persistence of the potentially explosive atmosphere. Equipment is categorised depending on the level of zone (0, 1 and 2) where it is intended to be used. A certification procedure following ATEX Directive was included in our installation for the purpose of advancing the technology to commercialization. As a result, a classification is given according to our preliminary layout.
The solar gasification plant is designed to utilize about 50 kg/h of petcoke (dry basis). A special unit based on pneumatic conveyor to feed finely ground coke (particle size less than 100 pm) from the ground has been installed. It is expected a coke consumption between 30 and 50 kg/h and a water consumption between 60 and 100 kg/h. This installation includes a multi-screw feeder and a mixing tank, as well as valves, flow meters and pumps. The multi-screw feeder comprises a weighing hopper for metering and weighing pulverized coke. It runs with high accuracy with a capacity of 50 kg/h. In the mixing tank, coke is mixed with water to form the slurry.
Finally, slurry prepared in the tank is conveyed to the entrance of the reactor by a pump. An electrical evaporator with a capacity of about 60 kg/h will supply the extra steam flow to keep the window cool and clean from particles. The coke reacts with steam at a temperature of 1100 - 1400°C to produce a raw fuel gas and ungasified material. After having left the reactor, the product gas is simply cooled down by water in a standard TEMA type BEU heat-exchanger to reduce the temperature enough to accomplish the requirements of the torch. In this regard, the requirements of heat exchanger for a heat recovery gasification system are more stringent than a cooler. Major difficulties encountered in the use of heat recovery systems for these technologies are fouling and pressure and temperature limitations of present materials and designs. An important effort has been initiated in our group for the demonstration of advanced heat exchangers and cleaning systems for gasification applications based on industrial experience.
In a final separator tank, the remaining water content of the product gas is separated from the syngas. Most of the residual solids from gasification fall into this device or in a water trap placed after. These residual solids generally consist of slag (the inert material from the feed coke) and some unreacted carbon. A small amount of the gas is separated for chemical analysis in a gas chromatograph and/or infrared gas measurement system. For this plant a syngas production of around 100 to 180 kg/h has been estimated. The schematic layout of the system is showed in Fig.
2.
In a future step, it is envisaged to use the remaining sensible heat of the exhaust gases to preheat the reacting steam before entering the reactor. Furthermore, a gas cleaning system is also foreseen, this includes a separation unit for particles and NH3 using water as washing medium, a H2S removal unit working with a NaOH solution, and finally the synthetic gas would be stored in a conventional refinery gas deposit system.
For evaluation of SYNPET solar receiver and plant performance the system is equipped with the following sensors:
• Gas chromatograph and IR gas analyzer connected to the exit for online measurement of the H2, CO2, CO and CH4 mole fractions
• Thermocouples to monitor temperatures at several locations (receiver, inlet and outlet, insulation, vessel, heat exchangers, etc.)
• Mass flow meter to measure syngas quantity
• Pressure transducers at several locations (receiver pressure, receiver pressure drop, etc). All the data will be recorded by the control system located on the ground.
