What will happen if ash backs up in a dry sorbent baghouse hopper?

When ash backs up in a dry sorbent baghouse hopper, the situation leads to moisture collection and hardening of the material. This occurs because as the ash accumulates, it can trap humidity from the environment, leading to the formation of clumps or hard masses due to the added moisture content. This hardening can obstruct the movement of the material and cause operational issues within the filtration system, potentially leading to clogging or inefficiencies in the removal of particulates from the gas stream.

In contrast, other outcomes mentioned in the options, such as improving filtration, increasing airflow, or enhancing sorbent efficiency, would not occur as a result of ash backup. In fact, these scenarios typically imply a well-functioning system where the materials are properly processed, which would be hindered by ash buildup. Therefore, the situation where ash backs up results in moisture collection and hardening is the most accurate understanding of the consequences in the context of baghouse operations.