Two-stage hydroprocessing reaction scheme with series recycle gas flow

A hydroprocessing plant for parallel hydroprocessing of hydrocarbon with series flow hydrogen recycle, comprising:

• a hydrocarbon feedstock stream;
• a first catalytic reactor zone for hydroprocessing a single common multistage fractionator product stream with a recycle hydrogen-rich gas stream;
• a first separator for separating an effluent stream from the first reactor zone into a first hydrogen-rich gas stream and a first hydroprocessed product stream;
• a second catalytic reactor zone for hydroprocessing the hydrocarbon feedstock stream with the first hydrogen-rich gas stream in a single pass at a hydrogen partial pressure substantially lower than in the first catalytic reactor zone so as not to require compression of the first hydrogen-rich stream, wherein the first hydrogen-rich stream is the sole source of hydrogen in the second catalytic reactor zone;
• a second separator for separating an effluent stream from the second reactor zone into a second hydrogen-rich gas stream and a second hydroprocessed product stream;
• a make-up hydrogen stream for adding make-up hydrogen to the second hydrogen-rich gas stream;
• a compressor for compressing the second hydrogen-rich gas stream to a pressure of the first catalytic reactor zone as the recycle hydrogen-rich gas stream;
• a single common multistage fractionator for receiving and fractionating together the first and second hydroprocessed product streams into a plurality of single fractionator product streams including a sidestream;
• and
• a line for supplying the sidestream to the first catalytic reactor zone.

In a process comprising parallel hydroprocessing of first and second hydrocarbon streams in first and second respective reaction zones, and separating effluents from the reaction zones to form at least one hydroprocessed liquid product and a hydrogen-rich recycle gas, the improvement comprising:

• separating the hydroprocessed effluents in separate first and second separators to form respective first and second hydrogen-rich gas streams and first and second hydroprocessed liquid product streams;
• operating the second reaction zone at a substantially lower hydrogen partial pressure with respect to hydrogen partial pressure of the first reaction zone;
• supplying the first hydrogen-rich gas stream from the first separator to the second reaction zone in a single pass to substantially satisfy hydrogen requirements for the second reaction zone;
• adding make-up hydrogen to and then compressing the second hydrogen-rich gas stream from the second separator for feed to the first reaction zone, wherein the compression of the second hydrogen-rich gas stream is the sole compression of hydrogen in the improved process;
• fractionating the first and second hydroprocessed product streams together in a common multistage fractionator;
• and
• supplying a sidestream from the common multistage fractionator as the first hydrocarbon stream to the first catalytic reactor zone wherein the sidestream is the sole feed to the first catalytic reactor zone and wherein a fresh hydrocarbon feedstock is the sole feed to the second reactor zone.

A process for parallel hydroprocessing of hydrocarbon with series flow hydrogen recycle, comprising the steps of:

• fractionating a hydrocarbon feedstock stream into relatively light and heavy fractionator product streams;
• hydroprocessing the light fractionator product stream with a hydrogen-rich recycle gas stream in a single pass as the sole source of hydrogen in a first catalytic reactor zone to form a first reactor effluent stream;
• separating the first reactor effluent stream to form a first hydrogen-rich gas stream and a first hydroprocessed product stream;
• hydroprocessing the heavy fractionator product stream with the first hydrogen-rich gas stream in a single pass as the sole source of hydrogen in a second catalytic reactor zone, at a lower hydrogen partial pressure than the first reactor zone, to form a second reactor effluent stream;
• separating the second reactor effluent stream to form a second hydrogen-rich gas stream and a second hydroprocessed product stream;
• and
• adding a make-up hydrogen stream to the second hydrogen-rich gas stream and then compressing the second hydrogen-rich gas stream to form the hydrogen-rich recycle gas stream.

A hydroprocessing plant for parallel hydroprocessing with series flow hydrogen recycle, comprising:

• a fractionator for fractionating a hydrocarbon feedstock stream into relatively light first and heavy second hydrocarbon streams;
• a first catalytic reactor zone for hydroprocessing the first hydrocarbon stream with a single pass of a recycle hydrogen-rich gas stream as the sole source of hydrogen;
• a first separator for separating an effluent stream from the first reactor zone into a first hydrogen-rich gas stream and a first hydroprocessed product stream;
• a second catalytic reactor zone for hydroprocessing the second hydrocarbon stream with a single pass of the first hydrogen-rich gas stream as the sole source of hydrogen at a hydrogen partial pressure lower than in the first catalytic reactor zone;
• a second separator for separating an effluent stream from the second reactor zone into a second hydrogen-rich gas stream and a second hydroprocessed product stream;
• a make-up hydrogen stream for adding make-up hydrogen to the second hydrogen-rich gas stream;
• a compressor for compressing the second hydrogen-rich gas stream after the addition of the make-up hydrogen and supplying the compressed second hydrogen-rich gas stream to the first reactor zone as the recycle hydrogen-rich gas stream.