Waste heat recovery in crude processing for increasing hydrocarbon yield and reducing emissions

A low grade waste heat capture system comprising:

• a first hydrocarbon gas stream separated from a crude oil stream by a first separator positioned in a gas-oil separation plant (GOSP);
• a second hydrocarbon gas stream separated from the crude oil stream by a second separator positioned in the GOSP;
• and
• a refrigeration loop comprising:
• a mixed refrigerant stream in a liquid state;
• a first waste heat recovery heat exchanger configured to transfer heat from the first hydrocarbon gas stream to a first portion of the mixed refrigerant stream to vaporize the first portion of the mixed refrigerant stream;
• a second waste heat recovery heat exchanger configured to transfer heat from a first portion of a mixture of the first hydrocarbon gas stream and the second hydrocarbon gas stream to a second portion of the mixed refrigerant stream to vaporize the second portion of the mixed refrigerant stream;
• a third waste heat recovery heat exchanger configured to transfer heat from a second portion of the mixture to a third portion of the mixed refrigerant stream to vaporize the third portion of the mixed refrigerant stream;
• a turbine-generator configured to receive a combined stream comprising the vaporized first, second, and third portions of the mixed refrigerant stream, the turbine-generator comprising turbine blades coupled to a rotor, the turbine blades configured to rotate in response to flow of the combined stream through the turbine-generator, the rotor configured to rotate with the turbine blades, the turbine-generator configured to generate electrical power in response to rotation of the rotor;
• and
• a condenser configured to cool the combined stream from the turbine-generator to condense the combined stream to reform the mixed refrigerant stream in the liquid state.

A method comprising:

• flowing a first hydrocarbon gas stream to a first waste heat recovery heat exchanger, wherein the first hydrocarbon gas stream is separated from a crude oil stream by a first separator positioned in a gas-oil separation plant (GOSP);
• transferring, by the first waste heat recovery heat exchanger, heat from the first hydrocarbon gas stream to a first portion of a mixed refrigerant stream to vaporize the first portion of the mixed refrigerant stream;
• flowing a first portion of a mixture of the first hydrocarbon gas stream and a second hydrocarbon gas stream to a second waste heat recovery heat exchanger, wherein the second hydrocarbon gas stream is separated from the crude oil stream by a second separator positioned in the GOSP;
• transferring, by the second waste heat recovery heat exchanger, heat from the first portion of the mixture to a second portion of the mixed refrigerant stream to vaporize the second portion of the mixed refrigerant stream;
• flowing a second portion of the mixture to a third waste heat recovery heat exchanger;
• transferring, by the third waste heat recovery heat exchanger, heat from the second portion of the mixture to a third portion of the mixed refrigerant stream to vaporize the third portion of the mixed refrigerant stream;
• flowing a combined stream through a turbine-generator, wherein the combined stream comprises the vaporized first, second, and third portions of the mixed refrigerant stream, wherein flowing the combined stream through the turbine-generator causes a rotor of the turbine-generator to rotate;
• generating electrical power in response to rotation of the rotor of the turbine-generator;
• and
• condensing the combined stream from the turbine-generator to reform the mixed refrigerant stream in a liquid state.