Mississippi Power Co.’s nearly $7 billion Kemper County energy facility should be fully operational on lignite coal by Jan. 31, the utility said late Friday in a U.S. Securities and Exchange Commission filing.

Mississippi Power, a unit of Atlanta-based Southern Co., had estimated the plant would have a January in-service date in early December. This was preceded by a series of missed projected deadlines.

Mississippi Power said in its January filing that it is experiencing challenges with the plant’s gas clean-up systems for one of its gasifiers.

The plant has two gasifiers, which convert lignite coal into a synthetic gas (syngas) and are part of what the company calls the plant’s clean-coal technology. Once fully operational, the company expects to reduce its carbon dioxide emissions by 65 percent.

Though each gasifier has previously produced electricity using syngas, the facility must have “integrated operation of both gasifiers,” Mississippi Power said through its filing.

At one point, the plant, which is now running on natural gas, was supposed to go into full operation running on syngas by May 2014.

As for what the public pays, there is a $2.88 billion cap on what Mississippi Power ratepayers can pay for the plant. Any increase beyond that depend on the Mississippi Public Service Commission’s approval.

Mississippi Power estimates that any extension of the in-service date beyond Jan. 31 would cost about $25 million to $35 million per month. The utility also said that additional costs may be required if any further equipment or design issues emerge.

“If integrated operation of both gasifiers does not occur by mid-January, the expected in-service date and related cost estimate for the Kemper IGCC may require further revision,” the utility said its filing.