Coal Reactivity by Rod Hatt - Chap 18

Coal Reactivity

This chapter discusses the reactivity of coal and how it correlates with rank. The transcript covers five areas: volatile matter, fuel ratio, oxygen content and moisture ash-free BTU, carbon to hydrogen ratios, and hardgrove grindability influence on some coals.

Volatile Matter

• Volatile matter is like lighter fluid on a charcoal grill.

• Low amounts of volatile matter make coal harder to light off.

• Loading values or pounds of volatile per million BTUs can help separate differences in coals.

• High-rank bituminous or anthracite type coal has mostly hydrogen and carbon in its volatile matter. Sub-bituminous or lignite coal has more oxygenated volatile matter.

Fuel Ratio

• Fuel ratio is equal to fixed carbon.

Overall, this chapter provides an overview of the importance of understanding the reactivity of different types of coal. It highlights the significance of measuring volatile matter and fuel ratio as key indicators for ranking coals based on their ability to light on fire and burn.

Understanding Coal Properties

In this section, the speaker discusses the properties of coal and how they impact its reactivity.

Fixed Carbon and Fuel Ratio

• Fixed carbon is calculated by difference and can have some air associated with it. It's not as strong a number as the direct measurement of volatile.

• The fuel ratio is the fixed carbon divided by the volatile. They are each measured in percent and the percents cancel out so the fuel ratio is just a value usually around one or two but it's just a value with no units so it's hard to utilize.

Oxygen Concentration

• The oxygen concentration in coal decreases as we go higher in rank, while carbon goes up.

• If oxygen concentration in a coal is high, it's more reactive.

• Oxygen content from laboratory is on a weight percentage basis and not correlated to calorific value.

Moisture Ash-Free Calorific Value (MAF)

• MAF indicates how much heat energy can be obtained from burning coal without moisture or ash dilution.

• As oxygen concentration goes up, MAF BTUs per pound or kilocalories per kilogram go down.

Hardgrove Grindability Index (HGI)

• Soft or easy-to-grind coals have higher HGI values.

• Higher HGI values allow for smaller particle size which affects combustion efficiency and burnout time of char.

Types of Petroleum Coke

In this section, the speaker discusses the two basic types of petroleum coke: sponge coke and shot coke.

Types of Petroleum Coke

• Sponge coke is more crunchy and can grind up, with a hard growth grind ability in the 40s or 50s.

• Shot coke is little round balls or big round balls that may have grinds in the 30s. It's harder to use because the HGI is tougher, making it harder to grind to smaller particles.

Utilizing Analysis for Coal Reactivity

The speaker explains how approximate and ultimate analysis can be used to determine which coal is more reactive and easier to burn.

Coal Reactivity

• Approximate and ultimate analysis can help sort out which coal is more reactive and easier to burn.

• The reactivity of coal correlates with its potential for spontaneous combustion issues, as well as lower LOI or lower unburnt carbon in ash.