Like the game of Whack-A-Mole, Mississippi Power knocks out one problem with the Kemper Project clean coal power plant only for another to appear as the utility tries to get the more than $7 billion plant operational.
A February report filed with the Mississippi Public Service Commission by independent monitor and engineering firm AECOM shows that problems continue to multiply at Kemper. The plant is designed to gasify lignite coal to fuel the facility’s electricity-generating turbines and remove byproducts such as carbon dioxide, sulfuric acid and anhydrous ammonia.
The issues, both new and ongoing, are the reason why the plant has blown through six months of commercial operation dates and is nearly three years behind schedule and more than $5 billion more expensive than when it was originally announced in December 2006. The utility says every month of delay costs it, not ratepayers, between $25 million and $35 million.
One critical problem found by the IM was the erosion of refractory material from the interior of the one of the two gasifiers — which convert lignite coal mined on site into synthesis gas. That plugged up the system that cools hot lignite ash after it leaves the gasifier.
The refractory coating is critical because it protects the thin metal shell of the gasifier from contact with the 1,800-degree temperatures inside the vessel, which could cause a breach and a possible explosion.
The company has previously admitted it has problems with removing ash from the gasifier and has had to replace large parts of the refractory layers in both gasifiers. The IM, in its reports on Kemper, continues to express concern over the “long-term viability” of both the repaired and original refractory coatings.
The particular process used at Kemper is supposed to allow for a longer-lived refractory and reduced operating costs, but it hasn’t worked out that way. The process used by Mississippi Power, called transport gasification (or TRIG), uses lower gasifer temperatures — around 1,800 degrees Fahrenheit vs. 2,400 degrees in other gasifier designs — to prevent the formation of slag or clinker, a rocky, cement-like substance which can adhere to and damage the refractory and require the gasifier to be shut down to remove it. Clinker forms when non-combustible ash particles melt and cling together.
According to the independent monitor, key milestones Kemper has not yet met include:
- Four days of continuous, simultaneous operation of both gasifiers producing on-specification syngas and fueling both turbines on 100 of it.
- Show that the gasifiers can run reliably without clinker formation. According to the IM, neither gasifier has run longer than eight weeks without clinkers.
- The ability to remove ash reliably from the gasifiers.
- Operation of coal feed and drying systems to provide coal for the gasifiers at the designed rate.
- Demonstrate the ability to produce saleable quality carbon dioxide, ammonia and sulfuric at near designed rates for a yet to be determined minimum time while in compliance with the plant’s environmental permits. According to the report, the lone off-taker for CO2, Denbury Onshore, has already received some CO2 from Kemper on Feb. 22.
- Achieve the plant’s 524 megawatt power rating fueled by 100 percent syngas. The plant has a capacity of 582 megawatts on syngas, but 58 megawatts is needed to run various processes needed for gasification.
AECOM also said the facility is having problems with corrosion in the sour water system, which processes contaminated water used to remove harmful chemicals from the syngas before it reaches the turbines.
There are also continuing problems with a filtering system that recovers water for re-use in the plant. The system is being plugged repeatedly by small coal particles known as coal fines. As a result, the plant’s needs for clean water have outstripped the capacity of its original 5 million gallon storage tank, which the utility has dealt with by adding a 1.7 million gallon temporary tank.
Coal fines have also damaged parts of the coal feed system as well.
The plant also lacks enough nitrogen capacity with its installed plant for startup, necessitating the utility to have it trucked in from off site.
The report was filed with the PSC before last week’s admission by the company that it wouldn’t meet its mid-March online to bring Kemper’s gasifers online.
The company will have to file a rate case with the PSC by June 3, as the present 15 percent increase passed in December 2015 will expire by then.