Reduction of regenerator clogging

A combustion method comprising

• (A) combusting fuel and gaseous oxidant in a furnace to generate heat of combustion which heats a charge in the furnace and generate gaseous combustion products which include alkali vapor species,
• (B) passing a gaseous flue gas stream comprising gaseous combustion products from the furnace through a first passageway in a heat recovery device wherein the first passageway has surfaces exposed to the flue gas stream, to heat the surfaces and cool the flue gas stream, and forming liquid or solid deposits on the surfaces by interaction between components of the combustion products, and passing cooled depleted flue gas out of the first passageway,
• (C) discontinuing passage of the flue gas stream through the first passageway and then passing a gaseous reducing stream through the first passageway in the direction opposite to the flow direction of the flue gas stream in contact with said deposits to react the gaseous reducing stream with the deposits and thereby causing removal of deposits from the surfaces and forming in the first passageway a gaseous byproduct stream comprising products of reaction of the deposits with the reducing stream,
• wherein alternatingly (i) the gaseous reducing stream is produced by (a) passing a gaseous flue gas stream from the furnace which comprises gaseous combustion products including alkali vapor species through a second passageway in a heat recovery device wherein the second passageway has surfaces exposed to the flue gas stream, to heat the surfaces and cool the flue gas stream, and forming liquid or solid deposits on the surfaces in said second passageway by interaction between components of the combustion products, and passing cooled depleted flue gas out of the second passageway, and (b) combining a portion of the cooled depleted flue gas from the second passageway with fuel;
• wherein the gaseous byproduct stream passed from the first passageway comprises carbon monoxide and hydrogen formed in an endothermic reaction in the first passageway;
• and (ii) cooled depleted flue gas passed out of the first passageway is combined with fuel and passed into and through the second passageway in contact with said deposits on surfaces in said second passageway, and reacts with the deposits thereby causing removal of deposits from the surfaces, and forms in the second passageway a gaseous byproduct stream comprising products of reaction of the deposits with the reducing stream and comprising carbon monoxide and hydrogen formed in an endothermic reaction in the passageway, and
• (D) passing the byproduct stream from the first passageway into the furnace and combusting reducing components in said byproduct stream in the furnace.