The use of Coal to produce electrical power is rapidly coming to an end. The Navaho Generating Plant will close later this fall, it receives its coal from a pipeline originating in Wyoming. Mixed with water it creates a “slurry” easily transported in pipes with the aid of pumps south to where the four corners states of Arizona, Utah, Colorado and New Mexico intersect. It has the distinction of emitting the equivalent of 3.3 million passenger cars annually. No other plant in the United States releases more carbon into the environment.
In Pennsylvania, the Bruce Mansfield plant is scheduled to be shut down by the end of the year as well. This plant has released 123 million tons of carbon into the air between 2010 and 2017.
The Paradise Plant in Kentucky has emitted 102 million tons during the same period; it will be the last to shut down this year.
The environmental impact of each plant is only part of the reason for the shutdowns, many believe it is the main driving force. Economics is the predominant factor in the shutdowns, the cost of natural gas is much lower than coal. But that is only part of the fiscal impact on the plants, there is one other major consideration.
Maintenance is viewed by most manufacturers as overhead, to be avoided as much as possible, in solid fuel plants it is a major expense. Power Producing Plants conduct maintenance shutdowns two times a year, more may be required depending upon equipment breakdowns. They are expensive, the cost of one outage costs tens of millions of dollars. Coal, Petroleum Coke, Biomass and Garbage burners have three heavy maintenance components. The fuel feed system, Fire Box (Boiler) and the Ash System, all are subject to extreme wear brought on by the silica (sand) that is carried with the fuel.
Sand is abrasive, acting as sandpaper over the course of a few months the effects are noticeable in the belt conveying systems carrying the fuel to the bunkers (surge tanks) that hold and control as it is introduced to the firebox. Included in that array of equipment are drag conveyors made of steel, conveyors to move the fuel from the piles to the conveying belts, grinders to reduce it to what is called “spec size”, and separators which pass the correct sized material directly to the firebox feeding belts. The conveyor belts are long 1/4 mile is not an exaggeration in some plants, with a width of 6 feet a lot of material is moved in a short amount of time. There are hundreds of ball bearings, countless electric motors, screens, and huge heavy hammers in the grinders. They all need replacing along with the conveyor belts, the quantity is doubled to 1/2 mile because it has to be a closed-loop. Sheets of heavy steel must be installed on the bottom of drag conveyors, the sand takes it toll on plates 1/2 inch and thicker; labor is intense and costly.
The fuel feed system into the fireboxes must be renewed, here too the sand is a relentless factor to deal with. Depending upon how it is fed into the firebox, whether by screw conveyor, sprayed through nozzles, or compressed in slugs the 24-hour service the equipment experiences is detrimental to its life cycle. Many of the fireboxes (boilers) are what is known as fluidized bed combustors, that is the fuel is cast upon molten sand then combusted. It creates an updraft with the height of the firebox acting as a flue sending the smoke, ash, and heat upward. Along the sides of the firebox are boiler tubes moving water from the bottom of the boiler to the top turning it into steam to power the Steam Turbines. Sand is sent airborne as well, red hot it clings to the boiler tubes running down them like water eroding the steel along with it on its downhill journey. The red hot molten sand causes erosion digging deep into the relatively thin 1/4 inch thick boiler tubes, often causing them to leak. During the repair cycle, the tubes must be inspected, repaired and or replaced as needed requiring highly skilled welders, riggers, and crane operators.
From the firebox the flue gas, smoke, and sand infused hot gases flow into a separation cyclone, the heavy particles drop to the bottom to be re-introduced into the firebox, the lighter particles are lifted away to an air-cleaning Baghouse. Lined in firebrick the Cyclonic separator, as well as the firebox, must be lined and repaired where they have been damaged. Heat resistant bricks and mortar are installed; again highly skilled Refractory installers are employed.
The Cyclone sends the lighter particles to the Baghouse, the clean air exits through specially constructed bags as long as 50 feet and 6 inches in diameter, through a fan then out the Smoke Stack. The Ash is conveyed out of the baghouse from the bottom via screw conveyors and deposited into a holding tank. The Ash is abrasive also, more so when combined with the silica it has carried with it throughout the entire process, the conveyors must be removed and replace. The holding tank has experienced heavy wear as well as needing attention to many of its critical parts.
The Ash is conveyed from the bottom of the firebox through a screw conveyor with water flowing through it to cool the red hot molten ash prior to depositing it into it’s holding tank; which needs maintenance as well. The water lined conveyor demands heavy maintenance throughout the year, normally replacement is needed during the outages.
All of the equipment is a constant maintenance issue, often shutting down entire plants for emergency repairs, those shutdowns cost in the millions, not including lost production. The costs of the fuel handling heavy equipment, bulldozers, front end loaders, and trucks have not been mentioned, that is a cost as well, it takes a lot of equipment and manpower to move the fuel around.
The Solid Fuel Plants require a fuel buyer, it is a full-time job hunting down fuel suppliers, normally one main supplier is used but often others must be acquired to assure an ample supply. The Ash is a Toxic Waste, one person managing the Ash is another full-time position. The person in charge of the Ash is the linchpin of whether the plant can continue to operate or must shut down because of not having a place to store or disposal; it’s the most important job in the plant. If a use for it cannot be found it must then go to a toxic waste landfill, the costs are enormous with the person named on the manifest he/she is responsible for the waste even in the landfill; until death do us part.
All of these expenses are eliminated when Natural Gas is used as fuel. There is only a high-pressure pipe delivering it to the firebox, no ash, no erosion, and no re-lining with fire brick and mortar. All of the labor has been reduced to just the steam system saving literally tens of millions of dollars yearly. The owners realize an increase in profits, the ratepayers don’t experience any savings other than environmental.
Coal will never come back, it doesn’t matter what any politician spouts off about, the owners of the plants hold all of the cards. It is an industry that must spend a lot of money to make a lot of money, with the use of Natural Gas, Solar, and Wind, the money invested is not nearly as great; the profits yeh, they increase but that’s the way of it isn’t it?
Jacques Lebec Natural Self Reliance