A full liquid type medium and high temperature heat accumulator comprises a box body, a plurality of trays, a plurality of screens, multi-hole quality composite
phase change heat storage
layers and a heat exchanging
pipe, wherein the inner portion of the box body is filled with saturation liquid of working medium, the plurality of trays are respectively and horizontally fixed on the inner wall of the lower portion of the box body, the plurality of screens are respectively arranged at the bottom of each tray, the multi-hole quality composite
phase change heat storage
layers are respectively paved on the screens, the multi-hole quality composite
phase change heat storage
layers are formed by composite phase change heat storage materials in an accumulating mode and completely immersed in the saturation liquid of the working medium, the heat exchanging
pipe is arranged in an inner cavity of the upper portion of the box body, a
pipe cavity of the heat exchanging pipe is isolated from the inner portion of the box body and communicated with the outer portion of the box body, and the
heat conducting working medium is in the box body in a flowing mode. The invention further discloses a medium and high temperature
flue gas
waste heat utilization heat collecting or heat storage
system composed of the full liquid type medium and high temperature heat accumulator, and a lower level
heat exchanger is used for continuously supplying heat in the range of 200 DEG C to 400 DEG C. The full liquid type medium and high temperature heat accumulator and application of the full liquid type medium and high temperature heat accumulator in
flue gas
waste heat recovery has the advantages of being excellent in heat exchanging ability, simple in structure and long in service life.