Influence of Feedstock Variability on Corrosion Dynamics in Municipal Wast-to-Biofuel Conversion Processes

Municiple waste contains a plethora of organic and inorganic chemicals. While the front-end separation and chomping process removes many of the inorganic materials there are a lot of inorganic materials processed through the gasifier. The gas flow from the gasifier contains sulfurs, acids both organic and Inorganic, halides and just about every other corrodent that will negatively affect the materials of construction.

Materials of construction are selected by the FEED engineering group based on a given assumption of the process constituents in the feedstock. The materials of construction are then specified based on the anticipated damage mechanisms that negatively affect the materials of construction. Materials are specified to last for a given time period, typically 25 to 30 years. When feed streams change the assumptions that were used to select materials are no longer valid. The problem with municipal waste feed stock is that the chemical composition is unpredictable and anticipated damage mechanisms change throughout the process. Corrosion rates once assumed so that equipment can have a life of 30 years are now shortened. Cracking mechanisms, not anticipated, are now causing failures.

The asset integrity and reliability program must be very robust. Every potential damage mechanism must be identified with the understanding that feed stock will change. Inspection and testing must be performed to ensure damage is detected long before a loss of containment event. Feed stream analysis must be evaluated on a daily basis in order to predict downstream damage.

The benefits of using municipal waste to manufacture Americas chemical and fuel needs are great. Preventing loss of containment events and keeping these plants safe is a new asset integrity challenge that must be met.