Provided is a combustion device, including: a burner including an ammonia injection nozzle having an injection port that faces an inner space of a furnace; and an adjustment structure configured to adjust an opening area of the injection port.

A combustion system with a combustion area in a boiler including a fuel pipe for delivering fuel is disclosed. A duct having a bend extended there through is in fluid communication with the fuel pipe and the combustion area of the boiler. The duct has an outer perimeter and an inner perimeter. The duct includes a first partition plate to form a first parallel flow of the fuel between the outer perimeter and the first partition plate, upstream of the bend.

A combined combustion burner and a combustion apparatus including the combined combustion burner. The combined combustion burner may include a center tube forming a center passage configured to supply cooling air, a fuel tube surrounding the center tube and forming a fuel passage through which premixed fuel mixed with solid fuel and primary air is sprayed, a secondary tube surrounding the fuel tube and forming a secondary passage through which secondary air is sprayed, and an additional spray nozzle inserted inside the center tube and configured to spray auxiliary fuel containing ammonia.

A combustion system with a combustion area in a boiler including a fuel pipe for delivering fuel is disclosed. A duct having a bend extended there through is in fluid communication with the fuel pipe and the combustion area of the boiler. The duct has an outer perimeter and an inner perimeter. The duct includes a first partition plate to form a first parallel flow of the fuel between the outer perimeter and the first partition plate, upstream of the bend.