ORC system and method for stepwise recycling low-grade heat

Abstract

The invention discloses an ORC system and method for stepwise recycling low-grade heat and belongs to the field of energy saving. The system comprises a first pump (1), a second pump (5), a third pump (9), a first heat exchanger (2), a second heat exchanger (6), a third heat exchanger (10), a first gas-liquid separator (3), a second gas-liquid separator (7), a first expander (4), a second expander (8), a third expander (11), a mixer (12) and a condenser (15). The system belongs to a multistage organic Rankine cycle system and can efficiently and stepwise recycle a variable-temperature heat source; meanwhile, a pressure pump is arranged in front of each heat exchanger, so that better temperature matching in the heat exchange process of working mediums and the variable-temperature heat source is achieved, and available energy losses of the variable-temperature heat source can be effectively decreased. The system is suitable for recycling sunlight heat, geothermal energy, industrial waste heat, medium-low-temperature humid air and other low-grade heat energy.

Description

technical field [0001] The invention relates to an ORC system and method for cascade recovery and utilization of low-grade heat, belonging to the field of energy conservation. technical background [0002] Fossil fuels are the basis for human survival. Extensive use of fossil fuels not only brings environmental pollution, but also causes a huge waste of energy due to low utilization rates. With the depletion of fossil fuels, the utilization of variable temperature heat sources such as renewable clean energy solar energy, biomass energy, geothermal energy and factory waste heat has attracted more and more attention from researchers. Organic Rankine cycle power generation technology is regarded as one of the most suitable technologies for recovering low-grade energy, but the efficiency of general organic Rankine cycle systems is generally low. It is of far-reaching significance to improve the efficiency of the organic Rankine cycle and to popularize this technology. [0003]...

AI Technical Summary

Problems solved by technology

[0003] At present, for low-grade variable temperature heat sources, two methods of ORC waste heat recovery are mainly used: the first method mainly uses the ORC cycle of conventional pure working fluid, because there is an obvious constant temperature section in the evaporation process, which makes the heat energy recovery process of variable temperature heat sources difficult. The heat transfer temperature difference is large, so there is a significant loss of useful energy;

[0004] The second method mainly uses a zeotropic mixed working fluid ORC cycle to achieve temperature matching. Since the slip temperature of the conventional mixed working fluid evaporation process is not high, although the efficiency of the ORC system using pure working fluid can be improved, but Thermal efficiency improvement is limited

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