System and method for integrated gasification control

A method for controlling an oxygen to carbon (O/C) ratio in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• determining a syngas demand based on load constraints, the syngas demand being representative of a desired output of a gasifier;
• determining oxygen and carbon setpoint values based on an oxygen to carbon (O/C) ratio setpoint value and the syngas demand;
• adjusting oxygen and carbon valves in the gasification plant based on the oxygen and carbon setpoint values, respectively;
• converting a carbon flow rate to a demand controller signal by a macro unit conversion;
• receiving the demand controller signal and a demand controller setpoint value at a PID controller and generating a PID controller signal;
• receiving the PID controller signal and an automatic demand value at a signal selector and generating a selected demand value;
• receiving the selected demand value and a syngas demand override value at a low selector and generating a load constrained demand value;
• converting the load constrained demand value to a bias value, and
• biasing an oxygen flow rate with the bias value;
• wherein the carbon flow rate is converted to the syngas demand signal by the following equation:
• m=F*12.011*(24/2000),
• where,
• m represents the syngas demand and F is a slurry flow in lb-mol/hour.

A method for determining an oxygen setpoint value in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• multiplying an oxygen setpoint value by a carbon flow rate to generate an oxygen setpoint high limit;
• determining an oxygen demand constrained by a carbon flow rate at a low selector from a syngas demand and the oxygen setpoint high limit;
• multiplying the oxygen setpoint high limit by a predetermined factor to generate an oxygen setpoint low limit, and
• determining a constrained oxygen setpoint value at a high selector from the oxygen setpoint low limit and the oxygen demand constrained by the carbon flow rate.

A method for determining a carbon setpoint value in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• determining a carbon setpoint low limit at a high selector from an oxygen flow rate and a syngas demand;
• multiplying the oxygen flow rate by a predetermined factor to generate a carbon setpoint high limit;
• determining a constrained carbon setpoint value at a low selector from the carbon setpoint high limit and the carbon setpoint low limit;
• and
• dividing the constrained carbon setpoint by a O/C ratio setpoint to generate the carbon control setpoint value.

A method for controlling an oxygen flow in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• calculating a compensated oxygen flow from an oxygen flow rate and oxygen temperature at a flow compensator;
• converting the compensated oxygen flow to a molar oxygen flow at a molar converter;
• multiplying the molar oxygen flow by an oxygen purity value to generate an oxygen flow signal;
• receiving the oxygen flow signal and an oxygen control setpoint value at a PID controller and generating a PID controller output signal;
• velocity limiting the PID controller output signal at a velocity limiter;
• and
• adjusting an oxygen valve using the velocity limited PID controller output signal.

A method for controlling a carbon flow in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• calculating a carbon flow rate from a charge pump speed;
• selecting an actual carbon flow rate from an inferred carbon flow rate and a measured carbon flow rate at a signal selector;
• converting the carbon flow rate to a molar carbon flow rate at a molar converter;
• generating a carbon flow signal from the molar carbon flow rate, a velocity limited slurry concentration and a velocity limited carbon content;
• generating a carbon pump speed signal at PID controller using the carbon flow signal and a carbon control setpoint value;
• and
• adjusting the speed of a carbon pump by the carbon pump speed signal.

A method for controlling moderators in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• generating a compensated oxygen line steam flow signal at a first flow compensator from an oxygen line steam flow rate, a steam temperature and a steam pressure;
• generating a compensated carbon line steam flow signal at a second flow compensator from a carbon line steam flow rate, the steam pressure and the steam temperature;
• adding the compensated oxygen line steam flow signal and the compensated carbon line steam flow signal at a first adder to generate a total steam flow signal;
• determining a total moderator flow from the total steam flow signal and a recycled black-water flow;
• dividing the total moderator flow by the carbon flow at a first divider to determine a moderator/carbon ratio;
• determining a desired oxygen line steam rate from the moderator/carbon ratio signal and a moderator/carbon setpoint value at a ratio controller;
• determining an oxygen line steam valve signal from the desired oxygen line steam rate and the oxygen line steam flow signal;
• adjusting an oxygen line steam valve by the oxygen line steam valve signal;
• determining a carbon line steam valve signal from the compensated carbon line steam flow signal and a carbon line steam flow setpoint value;
• and
• adjusting a carbon line steam valve by the carbon line steam valve signal.

A method for controlling an air separation unit (ASU) that provides oxygen to a gasification plant, the gasification plant converting the oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• comparing oxygen valve positions of a plurality of gasifiers that are operating simultaneously at a high selector, and outputting a value x;
• calculating F(x)=0.002x+0.08, where F(x)>0.99, and x is the output of the high selector;
• and
• calculating F(y)=0.002y+0.81, where F(y)>1.0, and y is the oxygen valve position of a selected gasifier.

A method for controlling high pressure of a syngas header in a gasification plant, the syngas header transporting syngas from a gasifier, the gasification plant converting oxyzen and hydrocarbon feedstock into the syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method comprising the steps of:

• receiving a syngas header flow rate, a syngas header temperature and a syngas header pressure signal at a flow compensator, and calculating a compensated syngas header flow;
• and
• calculating a syngas header flare vent valve bias from the compensated syngas header flow, the syngas header temperature, and a maximum allowable flow through a syngas header valve;
• wherein the syngas header flare vent valve bias is calculated from the following equation:
• Δ ⁢ ⁢ Z = q q R · P R P + P 0 · T + T 0 T R · 100 , ⁢ where , ⁢ Δ ⁢ ⁢ Z = High override clean syngas pressure controller output bias, in %, q = Predicted compensated syngas flow, in scfh, q R = Syngas design flow, in scfh, P R = Absolute clean syngas design pressure, in psia, P = Clean syngas pressure, in psig, P 0 = Absolute pressure conversion, T = Clean syngas temperature, in ° F., T 0 = Absolute temperature conversion, and T R = Absolute clean syngas design temperature, in ° R.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of controlling an oxygen to carbon (O/C) ratio in a gasification plant, the gasification plant converting oxygen and feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• determining a syngas demand based on load constraints, the syngas demand being representative of a desired output of a gasifier;
• determining oxygen and carbon setpoint values based on an oxygen to carbon (O/C) ratio setpoint value and the syngas demand;
• adjusting oxygen and carbon valves in the gasification plant based on the oxygen and carbon setpoint values, respectively;
• converting a carbon flow rate to a demand controller signal by a macro unit conversion;
• receiving the demand controller signal and a demand controller setpoint value at a PID controller and generating a PID controller signal;
• receiving the PID controller signal and an automatic demand value at a signal selector and generating a selected demand value;
• receiving the selected demand value and a syngas demand override value at a low selector and generating a load constrained demand value;
• converting the load constrained demand value to a bias value;
• and
• biasing an oxygen flow rate with the bias value.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of controlling an oxygen to carbon (O/C) ratio in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• determining a syngas demand based on load constraints, the syngas demand being representative of a desired output of a gasifier;
• determining oxygen and carbon setpoint values based on an oxygen to carbon (O/C) ratio setpoint value and the syngas demand;
• adjusting oxygen and carbon valves in the gasification plant based on the oxygen and carbon setpoint values, respectively;
• converting a carbon flow rate to a demand controller signal by a macro unit conversion;
• receiving the demand controller signal and a demand controller setpoint value at a PID controller and generating a PID controller signal;
• receiving the PID controller signal and an automatic demand value at a signal selector and generating a selected demand value;
• receiving the selected demand value and a syngas demand override value at a low selector and generating a load constrained demand value;
• converting the load constrained demand value to a bias value, and
• biasing an oxygen flow rate with the bias value;
• wherein the carbon flow rate is converted to the syngas demand signal by the following equation:
• m=F*12.011*(24/2000),
• where,
• m represents the syngas demand and F is a slurry flow in lb-mol/hour.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of determining an oxygen setpoint value in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• multiplying an oxygen setpoint value by a carbon flow rate to generate an oxygen setpoint high limit;
• determining an oxygen demand constrained by a carbon flow rate at a low selector from a syngas demand and the oxygen setpoint high limit;
• multiplying the oxygen setpoint high limit by a predetermined factor to generate an oxygen setpoint low limit, and
• determining a constrained oxygen setpoint value at a high selector from the oxygen setpoint low limit and the oxygen demand constrained by the carbon flow rate.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of determining a carbon setpoint value in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• determining a carbon setpoint low limit at a high selector from an oxygen flow rate and a syngas demand;
• multiplying the oxygen flow rate by a predetermined factor to generate a carbon setpoint high limit;
• determining a constrained carbon setpoint value at a low selector from the carbon setpoint high limit and the carbon setpoint low limit;
• and
• dividing the constrained carbon setpoint by a O/C ratio setpoint to generate the carbon control setpoint value.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of controlling an oxygen flow in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• calculating a compensated oxygen flow from an oxygen flow rate and oxygen temperature at a flow compensator;
• converting the compensated oxygen flow to a molar oxygen flow at a molar converter;
• multiplying the molar oxygen flow by an oxygen purity value to generate an oxygen flow signal;
• receiving the oxygen flow signal and an oxygen control setpoint value at a PID controller and generating a PID controller output signal;
• velocity limiting the PID controller output signal at a velocity limiter;
• and
• adjusting an oxygen valve using the velocity limited PID controller output signal.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of controlling a carbon flow in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• calculating a carbon flow rate from a charge pump speed;
• selecting an actual carbon flow rate from an inferred carbon flow rate and a measured carbon flow rate at a signal selector;
• converting the carbon flow rate to a molar carbon flow rate at a molar converter;
• generating a carbon flow signal from the molar carbon flow rate, a velocity limited slurry concentration and a velocity limited carbon content;
• generating a carbon pump speed signal at PID controller using the carbon flow signal and a carbon control setpoint value;
• and
• adjusting the speed of a carbon pump by the carbon pump speed signal.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of controlling moderators in a gasification plant, the gasification plant converting oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• generating a compensated oxygen line steam flow signal at a first flow compensator from an oxygen line steam flow rate, a steam temperature and a steam pressure;
• generating a compensated carbon line steam flow signal at a second flow compensator from a carbon line steam flow rate, the steam pressure and the steam temperature;
• adding the compensated oxygen line steam flow signal and the compensated carbon line steam flow signal at a first adder to generate a total steam flow signal;
• determining a total moderator flow from the total steam flow signal and a recycled black-water flow;
• dividing the total moderator flow by the carbon flow at a first divider to determine a moderator/carbon ratio;
• determining a desired oxygen line steam rate from the moderator/carbon ratio signal and a moderator/carbon setpoint value at a ratio controller;
• determining an oxygen line steam valve signal from the desired oxygen line steam rate and the oxygen line steam flow signal;
• adjusting an oxygen line steam valve by the oxygen line steam valve signal;
• determining a carbon line steam valve signal from the compensated carbon line steam flow signal and a carbon line steam flow setpoint value;
• and
• adjusting a carbon line steam valve by the carbon line steam valve signal.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of controlling an air separation unit (ASU) that provides oxygen to a gasification plant, the gasification plant converting the oxygen and hydrocarbon feedstock into syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• comparing oxygen valve positions of a plurality of gasifiers that are operating simultaneously at a high selector, and outputting a value x;
• calculating F(x)=0.002x+0.08, where F(x)>0.99, and x is the output of the high selector;
• and
• calculating F(y)=0.002y+0.81, where F(y)>1.0, and y is the oxygen valve position of a selected gasifier.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps of controlling high pressure of a syngas header in a gasification plant, the syngas header transporting syngas from a gasifier, the gasification plant converting oxygen and hydrocarbon feedstock into the syngas composed primarily of hydrogen (H2) and carbon monoxide (CO), the method steps comprising:

• receiving a syngas header flow rate, a syngas header temperature and a syngas header pressure signal at a flow compensator, and calculating a compensated syngas header flow;
• and
• calculating a syngas header flare vent valve bias from the compensated syngas header flow, the syngas header temperature, and a maximum allowable flow through a syngas header valve;
• wherein the syngas header flare vent valve bias is calculated from the following equation:
• Δ ⁢ ⁢ Z = q q R · P R P + P 0 · T + T 0 T R · 100 , ⁢ where , ⁢ Δ ⁢ ⁢ Z = High override clean syngas pressure controller output bias, in %, q = Predicted compensated syngas flow, in scfh, q R = Syngas design flow, in scfh, P R = Absolute clean syngas design pressure, in psia, P = Clean syngas pressure, in psig, P 0 = Absolute pressure conversion, T = Clean syngas temperature, in ° F., T 0 = Absolute temperature conversion, and T R = Absolute clean syngas design temperature, in ° R.