Burner assembly for air preheating combustion

A burner assembly for air preheating combustion, comprising a combustion chamber (1) and a metal box (4), wherein a heat exchanger (2) is disposed on a top of the combustion chamber (1), a burner (3) is disposed on a bottom of the combustion chamber (1), the burner (3) is provided with a metal throat pipe (10), and the metal throat pipe (10) is configured to receive gas from outside and transmit the gas into the burner (3);

• wherein the metal box (4) is disposed outside the combustion chamber (1) and a preheating channel (5) is defined between the metal box (4) and the combustion chamber (1);
• each of four sides of the metal box (4) defines a plurality of ventilation holes (8) uniformly arranged on an upper end of each of the four sides of the metal box (4);
• a bottom end of the metal box (4) is provided with a sealing baffle (9), a bottom of the burner (3) is provided with a metal baffle (6), and a hot air return compartment (11) is defined between the sealing baffle (9) and the metal baffle (6) and is connected to the preheating channel (5);
• and the metal baffle (6) defines a plurality of air inlet holes (7);
• wherein the burner assembly is configured to:
• when the burner assembly is operated, guide air from outside of the burner assembly to first pass through the plurality of ventilation holes (8), then enter the preheating channel (5) to make the air be preheated to thereby obtain preheated air, and guide the preheated air to reach at the hot air return compartment (11) to complete air movement from top to bottom;
• and make the preheated air be in contact with the burner (3) via the plurality of air inlet holes (7) to preheat the gas in the burner (3), and guide the preheated air to enter the combustion chamber (1) for enhancing combustion, thereby to complete the air movement from bottom to top;
• and
• wherein the bottom end of the metal box (4) extends in a first direction (A) to form first folded edges (14), the first folded edges (14) define threaded holes (15) thereon, the sealing baffle (9) extends in a second direction (B) to form a second folded edge (18), the first direction (A) is different from the second direction (B), and the second folded edge (18) of the sealing baffle (9) is threadedly connected to the first folded edges (14) on the metal box (4) through bolts (16).