Aerojet Rocketdyne gasification technology is being developed under a Cooperative Research and Development Agreement between Aerojet Rocketdyne and the Department of Energy's Gasification Systems program. Development of Aerojet Rocketdyne’s Compact Gasifier has had the objective of applying technology developed, and experience gained from rocket propulsion engines to coal gasification. Key technology components include: a rapid-mix feed injection system to facilitate rapid burning; an advanced reactor cooling system to mitigate the need of refractory lining; and a rapid spray quench system for raw syngas cooling. These attributes offer the potential of developing a very compact and low-cost gasifier, with high carbon conversion and increased thermal efficiency. Development of an advanced high-pressure, dry coal feed solids pump is also part of development activities. Figure 1 shows a simplified drawing of an Aerojet Rocketdyne gasification system.
The Aerojet Rocketdyne gasifier is a single-stage, pressurized, oxygen-blown, plug-flow entrained reactor capable of achieving carbon conversions approaching 100 percent. The gasifier borrows several design features from rocket engine technology to enable a compact, low-cost, long-life, and highly efficient gasifier design.
Figure 2 shows the various components of an Aerojet Rocketdyne gasifier that can be developed by patterning after similar, but well proven, features within a rocket engine. These include a rapid mix injector design that can use multi-element injection to rapidly mix the coal feed with steam and oxygen, and disperse them across the reactor cross section. By doing so, it enables the injected coal particles to be heated rapidly to high temperature, and allows the gasification reactions to take place in a very short residence time. This rapid mixing is said to greatly minimize the mass transfer and kinetic limitations to gasification reactions. The result is a gasification system that can achieve rapid and complete carbon conversion with less oxygen required. This feed injection system is being developed in conjunction with the development of a high-pressure solids pump and a dense phase flow splitter capable of bulk feeding and distributing the pulverized coal fines to the gasifier at high pressure.
Another engineering feature borrowed from the rocket engine experience is the gasifier cooling liner design, which allows the internal reactor wall to be cooled and protected by forming a layer of solidified slag on its inside surface. This type of ceramic matrix composite (CMC) liner helps to protect the refractory underneath, enabling an operational life much longer than the six- to 18-month life typically experienced for non-cooled refractory brick in existing gasifiers.
The high temperature raw syngas would need to be cooled to about 700 °F before entering a commercially available cyclone and candle-type filter for fly ash removal. This is accomplished by rapid spray quenching the produced raw syngas with water.
The Aerojet Rocketdyne gasifier is expected to be able to process all different ranks of coal.
Figure 3 depicts the development of the Aerojet Rocketdyne gasifier and gasification system, going back decades to initial proof of concept, and continuing through to recent pilot plant work and dry solids pump development. As indicated, DOE has participated in funding and cost sharing for certain aspects of this work which continues currently with cost sharing for high pressure dry solids pump coal feed technology development.
The recent developmental work at GTI utilized an 18 tpd pilot plant gasifier, which completed partial oxidation and coal gasification tests in 2013 to validate modifications for improved gasifier performance. Currently, 400 tpd-scale Dry Solids Pump performance testing is underway and will provide verification for larger scale operation and underpin development of operating procedures.
Aerojet Rocketdyne gasification technology is now considered ready for demonstration at a 400+ tpd scale system with integrated gasifier and dry solids pump, and is seeking commercial demonstration partners to provide a host site. Successful demonstration would support advancement to commercial scale at 1000-3000 tpd.