Abstract: Disclosed in the present disclosure is a double-deck multi-span bridge construction method. According to the double-deck bridge construction method of the present disclosure, construction is carried out by using a method of disassembling a support jig frame in a graded and span-separated mode, an upper chord jig frame and a lower chord jig frame can be used in a recycle manner, and construction costs are reduced. In addition, a construction period of building the support jig frame is shortened, and other construction operations can be synchronously carried out on a span in which the jig frame is disassembled, for example, fire retardant coating construction can be carried out on a mounted bridge deck after the jig frame is disassembled, and the construction period of a double-deck multi-span bridge is effectively shortened.

Abstract: The present invention discloses a method for producing lithium carbonate from a low-lithium brine by separating magnesium and enriching lithium. A salt-lake brine is used as a raw material and is converted into halide salts through dehydration by evaporation and separation by crystallization; the halide salts are directly extracted using trialkyl phosphate or a mixture of trialkyl phosphate and monohydric alcohol, and an organic extraction phase as well as remaining halide salts are obtained after solid-liquid separation; reverse extraction is performed on the organic extraction phase to obtain a lithium-rich solution with a low magnesium-to-lithium ratio, and lithium carbonate is obtained after concentration and removal of magnesium by alkalization. The used solid-liquid extraction method is simple with no co-extraction agent used, and a solute distribution driving force is strong, unaffected by phase equilibrium of the brine extraction agent.

Abstract: The present invention discloses a method for producing lithium carbonate from a low-lithium brine by separating magnesium and enriching lithium. A salt-lake brine is used as a raw material and is converted into halide salts through dehydration by evaporation and separation by crystallization; the halide salts are directly extracted using trialkyl phosphate or a mixture of trialkyl phosphate and monohydric alcohol, and an organic extraction phase as well as remaining halide salts are obtained after solid-liquid separation; reverse extraction is performed on the organic extraction phase to obtain a lithium-rich solution with a low magnesium-to-lithium ratio, and lithium carbonate is obtained after concentration and removal of magnesium by alkalization. The used solid-liquid extraction method is simple with no co-extraction agent used, and a solute distribution driving force is strong, unaffected by phase equilibrium of the brine extraction agent.