Process for reducing sulfur emissions with calcium-containing sorbents

A process for reducing the emission of sulfur oxides from the combustion of coal, comprising:

• (a) combusting a fuel mixture of sulfur-containing coal and calcium-containing sulfur sorbent, said coal comprising coal particles resulting from aggressively beneficiating raw coal, wherein said aggressive beneficiation comprises (i) separating the raw coal into a coarse size fraction and a fine size fraction (ii) density separating the coarse fraction into a clean coal fraction, a refuse fraction and a middling fraction, (iii) comminuting said middling fraction, and (iv) combining said comminuted middling fraction with said fine fraction and further beneficiating the combined fraction, said calcium-containing sulfur sorbent comprising a calcium-containing compound selected from the group consisting of lime, limestone, hydrated lime, calcium oxide, dolomite, burnt dolomite, hydrated dolomite and combinations thereof, at least a portion of calcium in said sulfur sorbent reacts with sulfur oxides emitted during the combustion of coal, said combusting producing a flue gas comprising sulfur and calcium derived from said sulfur sorbent;
• (b) following said combusting, allowing a first portion of said calcium in the flue gas to react with a first portion of said sulfur in the flue gas in a first stage of sulfur capture in a high temperature region following combustion;
• (c) following said reaction of said first portion of said calcium in the flue gas, cooling said flue gas to a temperature within about 100.degree. F. above the condensation temperature using heat exchange or adding water to the flue gas said condensation temperature is the temperature at which aqueous liquid condenses from said flue gas;
• and
• (d) following said cooling, allowing a second portion of said calcium in the flue gas to react with a second mortion of said sulfur in the flue gas at a temperature within about 100.degree. F. above the condensation temperature of the flue gas stream in a second stage of sulfur capture prior to particulate separation from said flue gas, said second stage of sulfur capture having a residence time of greater than about 0.1 second.