You’ve Heard Of Coal. Ever Hear Of Slag?

Globally coal is continuing to serve the modern and developing world’s energy interests. Any energy expert will tell you the power and influence of Coal on the power sector is undeniable. Coal is cheap, abundant and available to developing countries that intend to utilize it. Coal will remain popular in coal dependent Asian countries like China and India; experts predict coal will remain as the dominant fuel source for the next fifty years plus.

As time marches forward and more and more higher quality coal is mined and consumed, this leaves a growing problem. There becomes more and more low quality coal left over that must be consumed. As more power plants are forced into using lower quality, lower BTU coal and higher ash coal types, they must contend with numerous challenges. Poorer quality coal types tend to be more difficult to burn and tend to negatively impact on boilers performance. It also should be noted that boilers burning lower grade coals are being kept running at higher operating load for much longer periods of time to make up for the lower heat values of the lower BTU coal burned.

Due to the deteriorating quality in available coal, boiler operations have become more challenged. Poorer quality coals have caused many boilers to experience increasing slag deposits on the interior furnace walls, air preheater and super heater sections of their boilers. When a boiler has severe slagging in the boiler combustion chamber it forces the boiler to be shutdown for mechanical cleaning. All unscheduled or unnecessary shutdowns cost the boiler operator a lot of money. Severe slagging causes many different operational problems such as production delays and production losses, sometimes if the boiler is producing power there are other economic penalties. Unscheduled shutdowns due to slagging costs boiler operators billions of dollars per year in lost productivity.

What is slag and what causes slagging? Coal contains carbon, hydrogen and oxygen – all of these are combustible, however, there are numerous inorganic impurities that are not combustible and contribute to slagging. The inorganic parts affect ash fusion temperatures. A particular coal type’s ash might be known for its tendency to slag and foul is related to the chemistry of the ash and ash fusion temperatures. Ash fusion temperatures relate directly to the propensity for slag formation in the boiler. When slagging deposits form on the boiler’s fireside surfaces and continue to collect the slag density also increases with time creating a deposit that is very hard and difficult to remove with traditional soot blowing techniques. When a boilers soot blowers cannot remove the ash build up from the upper recesses of a boiler in a timely manner, slag deposits can continue to grow, harden, and form very large and dangerous deposits.

Slagging usually is occurring in the convective areas of the boiler where ash collects on the boiler tubes and internal surfaces inside the furnace, where it crystallizes and hardens. The slag than acts as a heat refractory, insulating the boiler rather than convicting the heat to the water inside the boiler tubes.

The continual ash deposition on the furnace walls is what causes slagging and it occurs in the high temperature areas of furnaces directly exposed to flame radiation. In other areas these deposits are called fouling when they’re in other regions such as on tubes in the convection section of the boiler.

Why is slagging so bad? When large slag deposits form they can unexpectedly fall. Falling slag can puncture boiler tubes; damage the floor of the lower furnace forcing an unscheduled shutdown and lost production. When a large slag formation falls it will often damage the system.

In order to avoid severe slagging and unscheduled shutdowns, boiler operators are offered a fireside chemical treatment, CC-88.

CC-88 is a fireside chemical treatment. CC-88 is added to the coal on the coal feed conveyor belt and fed into the furnace along with the coal. CC-88 has proved its ability to significantly reduce slagging, fouling and plugging of boilers burning coal.

How does CC-88 work to reduce slagging? CC-88 plays a significant role in preventing the ash from sintering and fusing. Fusing and sintering describes the physical and chemical bonding of deposited slag particles. As sintering progresses, it results in increasing strength of deposits. Therefore preventing the ash from sintering and hardening is the objective of CC-88. CC-88 has a unique catalytic ability to generate oxygen, thereby enabling more complete combustion of more of the carbon contained in each tonnes of coal.

CC-88 promotes a slow burning by softening the hard carbon deposits and cracking slag formation, penetrating their surfaces and further cracking, which increases the slag porosity, and promotes cracking at the surface of the ash, thereby making the slag easier to remove with soot blowers.

CC-88 also work to decrease the melting point and friability of deposits formed from the ash constituents in the coal during combustion process. By changing the slag’s porosity makes the slag easier to remove during normal soot blowing and out-of-service cleaning.

After use of CC-88 combustion catalyst, boilers slagging, fouling and plugging problem are reduced dramatically. Boiler Temperature profiles in the furnace and exit flue gases are consistently lower when compared to operating the boiler with heavy slag.

Combustion catalysts improve boiler efficiency by extracting more heat energy from the fuel and by reducing heat losses when operating at minimum excess air. In addition, an effective combustion catalyst may reduce the level of smoke and solid combustibles and help a plant attain emissions compliance requirements that are not always achieved with the existing pollution control equipment. Combustion catalysts promote the combustion process by lowering the ignition temperature of the fuel, allowing for a longer burn time, and increasing the rate of combustion.

Asia’s Huge Energy Challenges

Despite having the world’s largest coal based economies Asia is energy starved.

1.5 Billion people in Asia have only partial access to electricity, which is vital to a decent living standard. The life-giving but very complicated solution: electricity from coal.

World leaders consumed with battling climate change are also taking to task extending electricity throughout the developing world.

We are at odds with crisis . First we have an environmental crisis with global warming. At the same time a human crisis of the “energy poor” who don’t have access to electricity in the home. These people cannot purchase any common household necessities. The UN and World Bank will focus efforts to bring affordable energy supplies to the world’s poorest people.

Most sensible environmentalists acknowledge that climate policy cannot forget aspirations of people in developing countries to lift they’re living standards.

Energy poverty — or the lack of access to electricity in the home-represents a staggering challenge across the developing world.

It is among the most critical issues  raise the standard of living of the world’s poorest citizens.

33% of India’s 1.2 billion people live without access to electricity, and twice that number rely on wood or dung to cook.

The dependence on wood for energy is environmentally destructive — for example, a major cause of deforestation — and a significant cause of ill health and early death due to hazardous indoor air quality.

In the developed world coal and oil are what has fueled our industrialization: Coal powers more than half the world’s electricity, while oil fuels the world’s transportation system.

It is immoral to deny India or Bangladesh the opportunity to enjoy the benefits of the modern hydrocarbon economy.

Unfortunately fossil fuel like coal and oil are polluting.

With 400 million people still living without electricity, India relies on coal for 69 per cent of its power supply and has the fourth-largest coal reserves in the world, after the U.S., Russia and China.

Both India and China are rapidly expanding their coal-based power supply. Coal is by far the cheapest way to generate electricity.

Its Energy vs Environment for billions of people. It will be a huge challenge to bring the two things together to address poor people’s basic development requirements.

1.4 Billion Chinese consumers are each day improving their standard of living. This new population deserving of all Creature Comforts like air conditioning and refrigerators are stretching China’s energy resources.

Experts worry that China’s energy needs will have to rely on Coal is an abundant fuel resources.

China is working hard to meet energy efficiency targets. For at least another 50 years fossil fuels emitting carbon dioxide, sulfur dioxide, nitrogen oxide and other greenhouse gases will grow.

This past winter and spring showed the largest six-month increase in CO2 tonnage ever by a single country.