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The reformate market is changing. While global reformate demand continues to grow, there are local regions where demand is flat or on a decline, like the US. This decrease may be explained by the expansion of ethanol use as an additive in gasoline, by alternative transportation technologies such as hybrid vehicles and electric vehicles, and by natural gas as a transportation fuel. More dedicated hydrogen (H2) plants are also being built, offsetting the need for net H2 production from reforming operations.
Catalytic reforming unita reactors that were designed to process heavy naphtha feeds at high severity are now operating at mild severity. The continuous catalyst regeneration (CCR) sections of these units are impacted by these changes. Operating the catalytic reforming unit at mild severity results in less coke generation. As coke generation decreases, limitations within the regeneration section begin to manifest. If the reduced catalytic reforming severity is long term, then catalyst regeneration will eventually need to be stopped.
Low-severity operation in the reactor leads to intermittent use of the regenerator, or to catalyst circulation through the CCR section without regeneration. Catalyst regeneration may become inconsistent, with some portions of the catalyst bed never being fully regenerated. These market-driven changes are expected to be long term. In the future, low coke operation could become the new normal in some markets.
Low coke generation also may be caused by operational upsets upstream or downstream of the catalytic reforming unit. At times, naphtha feedrates may be limited by other units operating in turndown or even shutdown mode. These operational upsets are usually short-term (issues are typically resolved within a few weeks), and can be managed without significant impact on the catalytic reforming unit.
However, any situation that causes low coke make can be severe enough to force operation outside of design parameters. The authors feel that it is necessary for the CCR user to develop a long-term, low-coke plan to deal with inevitable operating changes or upsets over a unit's lifetime. When perturbations put the CCR section outside of its design envelope, operators, engineers and managers must have reliable, readily available options at their disposal.
In high-coke situations where consequences are severe and may result in lost production, catalyst phase damage or equipment damage, the correction methods...