Reactor apparatus and methods

A bitumen or petroleum product processing apparatus includes a flow path through which bitumen or petroleum product and one or more reagents and/or catalysts flow. The apparatus may include a gas separation unit for removal of gas from the flow path. A pressure reducer may be positioned before the gas separation unit. The separation unit may include a separation volume that is elongate or flat in the horizontal plane, so as to maintain a high surface area relative to volume for bitumen or petroleum product in the separation volume. The separation unit may include a spray arrangement configured to spray bitumen or petroleum product mixed with gas into the separation volume. Two or more shut-down valves may be arranged to close a section of the flow path, thereby limiting or preventing ingress of air and/or oxygen into the closed section of the flow path when the apparatus is shut down. Two or more mixer stages may be arranged to operate in series or independently.