Process measurement and control

An apparatus comprising

• a. a first controller for accepting a first process parameter measurement signal and a process parameter setpoint signal and delivering in response thereto an intermediate control signal,
• b. transforming means for accepting said first process parameter measurement signal and generating a first predictive process parameter signal responsive thereto, said transforming means comprising
• aa. lag means for accepting said first process parameter measurement signal and generating a lagged signal by applying a second or higher order lag to said process parameter measurement signal, and
• bb. derivative means for accepting said lagged signal and generating said first predictive process parameter signal by a first time derivative to said lagged signal, and
• c. first signal combining means for accepting said first intermediate control signal and said first predictive process parameter signal and delivering in response thereto a first process variable signal being the weighted sum or difference between the intermediate control signal and said predictive process parameter signal.

A method for generating a process variable signal, said method comprising

• a. generating a process parameter measurement signal representative of the value of a preselected process parameter;
• b. transforming said process measurement signal into a transformed signal that is characterized as essentially the first time derivative of the process parameter measurement signal having applied thereto a second or higher order lag,
• c. converting said process parameter measurement signal into an intermediate control signal related to the time integral over the difference between the process parameter measurement signal and a process parameter setpoint signal, and
• d. generating in response to said transform signal and said intermediate process control signal a process variable signal representative of the weighted sum or difference of said transformed signal and said intermediate control signal.

A process for the production of ammonia comprising:

• a. introducing a fresh feed stream resulting from a first feed stream from a hydrogen source and a second feed stream from a nitrogen source into a reaction zone, said fresh feed stream being a portion of a total feed stream being introduced into said reaction zone,
• b. reacting said total feed stream in said reaction zone to convert hydrogen and nitrogen to ammonia and to generate a hydrogen, nitrogen and ammonia-comprising reaction effluent,
• c. separating an ammonia product stream from said reaction effluent as the product of the process,
• d. recycling a portion of said reaction effluent comprising hydrogen, nitrogen and ammonia as a recycle stream to said reaction zone, said recycle stream being another portion of said total feed stream,
• e. measuring the composition of said total feed stream and generating a first process parameter measurement signal representative of the hydrogen to nitrogen ratio of said feed stream,
• f. generating in response to first process parameter measurement signal and a process parameter setpoint signal a first intermediate control signal related to the deviation of said first process parameter measurement singal from said process parameter setpoint signal,
• g. generating a first transformed signal from said first process parameter measurement signal which is related thereto by the relationship:
• ##EQU9## wherein MP.sub.1 is said first process parameter measurement signal,
• PP.sub.1 is said transformed signal,
• S is the Laplace transform operator (d/dt),
• k.sub.41 is a constant not equal to 0,
• c.sub.1, c.sub.2 . . . c.sub.n are constants not equal to 0,
• n is an integer of at least 2,
• h. combining said first intermediate control signal and said first transformed signal to generate a first process variable signal constituting the weighted sum or difference of the first intermediate control signal and the transformed signal.
• i. controlling the relative size of said first feed stream from said hydrogen source and said second feed stream from said nitrogen source in response to said first process variable signal.

A process for the production of ammonia comprising

• a. introducing a fresh feed stream resulting from a first feed stream from a hydrogen source and a second feed stream from a nitrogen source into a reaction zone, said fresh feed stream being a portion of a total feed stream being introduced into said reaction zone,
• b. reactng said total feed stream in said reaction zone to convert hydrogen and nitrogen to ammonia and to generate a hydrogen, nitrogen and ammonia-comprising reaction effluent,
• c. separating an ammonia product stream from said reaction effluent as the product of the process,
• d. recycling a portion of said reaction effluent comprising hydrogen, nitrogen and ammonia as a recycle stream to said reaction zone, said recycle stream being another portion of said total feed stream,
• e. measuring the composition of said total feed stream and generating a first process parameter measurement signal representative of the hydrogen to nitrogen ratio of said feed stream,
• f. generating in response to said first process parameter measurement signal and a process parameter setpoint signal a first intermediate control signal related to the deviation of said first process parameter measurement signal from said process parameter setpoint signal,
• g. generating a first transformed signal from said first process parameter measurement signal characterized as the first time derivative of said first process parameter measurement signal having applied thereto a second or higher order lag,
• h. combining said first intermediate control signal and said first transformed signal to generate a first process variable signal constituting the weighted sum or difference of the first intermediate control signal and the transformed signal, and
• i. controlling the relative size of said first feed stream from said hydrogen source and said second feed stream from said nitrogen source in response to said first process variable signal.