DHL corner tube boiler is field assembled boiler, it uses a piping system as the frame of the entire boiler, and it bears the full load of the boiler, which makes a non-framework boiler. At the same time, this frame also serves as the down comer of the boiler and upper and lower headers. The boiler drum is an external type drum, the furnace is a fully enclosed membrane wall structure, the convective heat absorbing surface adopts the flag tube structure. The corner tube boiler has the advantages of compact structure, low steel consumption and rapid temperature increase.