Short answers, pulled from the story.
Hot blast is the preheated air blown into a blast furnace or used in other metallurgical processes. It cut fuel use substantially and ranks among the most important technologies developed during the Industrial Revolution, while also allowing higher furnace temperatures and greater furnace capacity.
James Beaumont Neilson invented and patented hot blast for iron furnaces in 1828 at Wilsontown Ironworks in Scotland. Thomas Botfield has a rival historical claim based on a January 1828 patent, but Neilson is credited as the inventor because he won the patent litigation.
Hot blast was patented in 1828 by James Beaumont Neilson and partners including Charles Macintosh. Neilson had found that raising the blast temperature to 149 C reduced fuel consumption from 8.06 tons of coal to 5.16 tons of coal per ton of iron produced.
George Crane and David Thomas developed hot blast independently at the Yniscedwyn Works in Wales. Crane filed a British patent in 1836, and the pair began producing iron using the process on the 5th of February 1837.
Hot blast allowed anthracite, which had resisted ignition under cold blast conditions, to be used successfully in iron smelting. Dr. Frederick W. Gessenhainer filed a US patent for the anthracite hot blast process in 1831 and produced anthracite iron at Valley Furnace near Pottsville, Pennsylvania, in 1836.
Adoption spread slowly because ironmasters had to pay for a license under Neilson's patent. By 1840-58 ironmasters held licenses paying £30,000 a year in royalties, and by 1843, just after the patent expired, only 42 of 80 furnaces in south Staffordshire were using hot blast.