Charles Grayson, Bigger Pie Forum – March 31, 2017
An automobile and the Kemper syngas production plant have a commonality, each have thousands of parts. One or two parts can fail in a car without disrupting a trip from Jackson to Brandon, but most must work together before driving from Mississippi to El Paso, TX. However, the engine (the main
part) must work to get to either Brandon or El Paso.
The gasifier reactors are the engine of Kemper as promised by Southern Co. (SO) and Mississippi Power Co. (MPC). They turn the carbon in lignite into a gas which becomes syngas, the proposed cheap fuel for generating cheap electric power at Kemper. Alas, the engines still do not work almost three years after the Kemper turbines began producing electricity from natural gas.
Southern promised that their new technology, called TRIG, had solved the long-standing problem of gasifying coal or lignite economically. The key to TRIG was its ability to gasify lignite at a lower temperature (by a few hundred degrees F) than older processes, which would correct the older processes’ issue of slag formation and erosion of the special tiles lining the reactors. Even though a large part of Kemper is complex pieces of equipment to modify and cleanup the gas from the gasifiers, ash is turning into slag chunks. It just ain’t going to work! At this point, even if it did work, it wouldn’t be cheap syngas or power.
Bigger Pie Forum has long felt the gasifier units (the engine) would never work reliably for long periods. The small temperature range within which the gasifier units must operate cannot be controlled uniformly across the large reactors. Either hot or cold spots will develop within the very large volumes of moving solid, gas mixture. Hot spots will fuse ash into slag, plugging the system, shutting down the units for long periods of time. Cold spots will result in either lower syngas production or low energy efficiency across the system. Both hot and cold spots result in terrible economics, assuming the reactors run at all.
Below is a distillation of problems relating ONLY to the gasifier units taken from the Independent Monitor Report to the PSC posted March 24, 2017. Many other problems with other parts of the syngas plant were listed, but we are focusing only on the engine (gasifiers). However, the other problems remain – with the transmission, the steering, the tires, and of course the brakes don’t work.
Oh, and the radiator was installed backwards.
We’ll zero in on the gasification reactors in more detail as the crucial June 3, 2017 date approaches. MPC is mandated to make a rate filing by that date. Can MPC satisfy the Mississippi Public Utilities Staff (MPUS) and PSC that syngas assets should be considered for inclusion in rates by that date? If MPC cannot operate the gasifiers by that date and must make a rate filing again for the electric power generating turbines burning natural gas, then the Kemper rate process is on a new course. Keep in mind, MPC already had to file a rate case for the turbines only burning natural gas back in July 2015. They have struggled two more years now and still can’t crank the engine. The battery is about to die.
IM Monthly Report, URS Corporation 600 Carondelet Street New Orleans, LA 70130-3587, Kemper IGCC Project, February 2017 report posted by PSC March 24, 2017
Pages 8-9: The following process and technology concerns are described in Section 1.1
The long-term viability of the modified refractory system design in repaired areas and of the original refractory system design in remaining areas of both gasifiers.
- The root cause(s) of the temperature excursion event in Gasifier B in August and the trips of Gasifier A in late October due to high temperatures in the Lower Mix Zone were investigated. Mitigation actions were developed and an updated RCA Report was provided by MPC in February (see Appendix B).
- It is unclear to the IM Team that the minor reductions in gasifier operating and alarm set point temperatures will significantly reduce the risks of thermal excursions or long-term clinker formation.
- Continuous, stable operation of the Airlocks/Rotary Valves upstream and immediately downstream of the Coal Dryers and of the Coal Dryers themselves for weeks/months at full design rates must be achieved before concluding that full functionality of the Coal Preparation System has been demonstrated.
- Trouble-free operation of the Venturi Scrubbers is required to enable the coal feed system for either gasifier train to operate continuously at full design coal feed rate. The IM Team will continue to monitor the progress, testing and performance of the multiple modifications to the Venturi Scrubber – Recovered Water Filter system and any future modifications that Plant Operations may implement to this part of the coal feed system.
Pages 9-10: Key Technical Milestones Not Yet Achieved as of 02 MAR 2017
- Complete hard face refractory repairs in Mix Zone of Gasifier B.
- Resume solids circulation in Gasifier B and complete heat up and dry out of repaired refractory.
- Resume simultaneous operation of both Gasifier Trains A and B with clean syngas from AGR Trains A and B composing at least some fraction of the gas going to combustion turbines CTA and CTB in co-fire mode with recycled syngas going back to Gasifiers A and B.
- Achieve the scheduled/targeted 4 days of continuous, simultaneous operation of both Gasifiers with 100% of the on-spec syngas produced by both Gasifiers going to CTA and CTB operating on 100% syngas (no co-firing) near, but not above, the current maximum capacity limit (80%) imposed by combustion turbine vendor (Siemens).
- Successfully run both CTA and CTB turbines on syngas (co-firing with natural gas is acceptable) for the minimum testing time required by turbine vendor (Siemens) prior to next borescope inspection and complete that inspection with no concerns noted by Siemens.
Achieve and reliably sustain full design coal feed rate (~400 kpph) to each Gasifier for a to-be-determined minimum period of time while continuing to produce on-spec syngas, CO2, ammonia and WSA products.
- Achieve full design power production of 524 MW based on 100% syngas flow to both CTA and CTB (no co-firing with natural gas) plus design steam turbine operation for a tobe-determined minimum continuous period.
- Demonstrate ability to operate both Gasifiers reliably over an extended period without:
- Forming ash clinkers or fused ash on walls of the Gasifier, OR (Note: neither Gasifier has operated for longer than about 8 weeks without clinkers occurring.)
- Experiencing difficulties continuously withdrawing ash from each Gasifier through its associated CCAD system and reliably discharging it from the Ash Moisturizers
- Demonstrate ability to reliably operate the Venturi Scrubber – Recovered Water Filter system in both Trains A and B (with any equipment additions and modifications as may be required) while continuously removing coal fines at target efficiency level and recovering design quantities of clean water needed for downstream operations.
Pages 2-4: The following Project Execution related concerns have been reported with associated resolution status:
- Venturi scrubber solids carryover issues – new duplex strainers will be installed on all 6 trains; steel platforms and piping are complete; strainers will be installed when received; performance of the new filter elements in the Recovered Water Candle Filters is being monitored during the lignite runs; better results but these filters are not able to handle the full flow, so bypass flow is being routed to gasifier sumps and temporary tanks for solids collection and disposal; a trial coal fines removal system has been installed consisting of polymer (flocculent) injection, system testing in progress.
- Plugging issues at the roll crushers – new sealed bearings have been installed in all six gear boxes; new 7 blade feeders will replace the existing 8 blade feeders in the roll crusher rotary inlet air locks (3 of 6 complete, 4th received); will also install auto lube systems and shaft modifications.
- Lignite dryer solids accumulation – material testing and evaluation completed (primarily petrified wood); backup in feed zone eventually trips inlet feeder; revised grid plate design has been installed in feed zones on all six dryers and is being monitored for process optimization.
- Lignite dryer weigh belt feeder plugging – coal fines growth from the walls requires ongoing maintenance to clean out; periodically damages the belt feeder; will install air rappers on discharge chutes.
Gasifier A coal feed incident – An incident in October allowed hot gas to back up into train 3 coal feed system, PDAC, Dispense Vessel, and into the Lock Vessel. RCA was completed; MPC posted status of RCA Action Items in February (see Appendix B, RFI 2887).
- Gasifier B refractory repairs – post shutdown inspection found damaged refractory in the lower mixing zone (see CCAD below); repairs in progress.
- CFAD and CCAD Systems (Continuous Fine and Coarse Ash Depressurization) – ash leaking through PLD filters is eroding and plugging downstream systems; PLD’s will be replaced; vent gas has been rerouted from low pressure PLD’s to coal silos for filtering upstream of vent gas compressor; Gasifier B was shut down on 2/20 due to inability of CCAD system to remove ash from the Seal Leg due to pieces of refractory found blocking the grate, which resulted in extremely high levels of ash in the standpipe.
- Ash moisturizer system – modifications on all 4 ash moisturizers have improved operation; dust suppression still an issue at times during ash and coal loading for disposal; these systems continue to be monitored