EP-4028430-B1 - SLURRY LOOP REACTOR POLYMERIZATION RATE AND QUALITY CONTROLLER

EP4028430B1EP 4028430 B1EP4028430 B1EP 4028430B1EP-4028430-B1

Inventors

PICOU, DOUGLAS J.
TRAPP, KEITH W.
Forcht, Kelly M.
QUANT, Asha C.
POINDEXTER, Ariana L.
MCGEE, Maxwell T.

Dates

Publication Date: 20260513
Application Date: 20200820

Claims (6)

A process for optimizing polymerization of a monomer in a loop polymerization reactor controlled by a reaction rate controller program, comprising: continuously and periodically obtaining polymerization results comprising at least melt index (MI), production rate and ash content on the polymerized monomer; the reaction rate controller program (RRC): determining whether each of the polymerization results is within predetermined target ranges for those results; storing recently obtained polymerization results in a computer readable database stored within the RRC, and averaging the recently obtained results with previously stored results; and when at least one of the polymerization results is out-of-range with respect to its predetermined target range, modifying at least one reaction parameter set-point comprising monomer concentration, catalyst feed rate and reactor temperature, and controlling associated hardware for modifying reaction parameter set-point(s) to drive any out-of-range polymerization result(s) toward the predetermined target range for that result; the process further comprising the RRC assessing the reasonableness of the MI result when the MI result is out-of-range, and if the result is unreasonable, retaining it for comparison to subsequently obtained MI results, without averaging it with previously stored MI results; wherein when the production rate is above its predetermined target range, the RRC decreases the catalyst feed rate set-point and/or varies the reactor temperature set-point and/or decreases monomer concentration set point until a production rate result reasonable progress rate toward its predetermined target range is established, wherein: (i) when the MI result is below its predetermined target range, the RRC increases reactor temperature; and/or (ii) when the MI result is above its predetermined target range, the RRC decreases reactor temperature; wherein: (iii) when the production rate is within its predetermined target range but the MI result is below its predetermined target range, the RRC increases the catalyst feed rate set-point and/or increases the reactor temperature set-point and/or decreases monomer concentration set point; and/or (iv) further wherein, when the production rate is within its predetermined target range but the MI result is above its predetermined target range, the RRC can decrease the catalyst feed rate set-point and/or decrease the reactor temperature set-point and/or increase monomer concentration set point; wherein when the production rate is below its predetermined target range, the RRC increases the catalyst feed rate set-point and/or varies the reactor temperature set-point and/or increases monomer concentration set point until a production rate result reasonable progress rate toward its predetermined target range is established, wherein: (v) when the MI result is below its predetermined target range, the RRC increases reactor temperature; and/or (vi) when the MI result is above its predetermined target range, the RRC decreases reactor temperature; wherein: (vii) when the ash content is above its predetermined target range and the MI is below its predetermined target range, the RRC increases the reaction temperature set-point, to reduce ash and increase the MI result; and/or (viii) when the ash content is above its predetermined target range and the MI is above its predetermined target range, the RRC increases the monomer concentration, to reduce ash and decrease the MI result.
A system for maintaining optimum polymerization production in a loop polymerization reactor, comprising: a loop polymerization reactor having hardware associated with modifying reaction parameters including at least monomer concentration, catalyst feed rate and reactor temperature; a digital control system having an executable multivariable reaction rate controller program (RRC) stored therein, which controls the hardware associated with modifying the reaction parameters; wherein the RRC: continuously and periodically receives and stores polymerization results comprising at least melt index (MI), production rate and ash content on one or more polymerized monomers; determines whether each of the polymerization results is within predetermined target ranges for those results; stores recently obtained polymerization results in a computer readable database within the RRC, and averages the recently obtained results with previously stored results; with the proviso of the RRC assessing the reasonableness of the MI result when the MI result is out-of-range, and if the result is unreasonable, retaining it for comparison to subsequently obtained MI results, without averaging it with previously stored MI results; and when at least one of the polymerization results is out-of-range with respect to its predetermined target range, the RRC modifies at least one reaction parameter set-point comprising monomer concentration, catalyst feed rate and reactor temperature by controlling the associated hardware for modifying reaction parameters to drive any out-of-range polymerization result(s) toward the predetermined target range for that result; wherein when the production rate is above its predetermined target range, the RRC decreases the catalyst feed rate set-point and/or vary the reactor temperature set-point and/or decrease monomer concentration set point until a production rate result reasonable progress rate toward its predetermined target range is established, wherein (i) when the MI result is below its predetermined target range, the RRC increases reactor temperature; and/or (ii) when the MI result is above its predetermined target range, the RRC decreases reactor temperature; wherein: (iii) when the production rate is within its predetermined target range but the MI result is below its predetermined target range, the RRC can increase the catalyst feed rate set-point and/or increase the reactor temperature set-point and/or decrease monomer concentration set point; and/or (iv) when the production rate is within its predetermined target range but the MI result is above its predetermined target range, the RRC can decrease the catalyst feed rate set-point and/or decrease the reactor temperature set-point and/or increase monomer concentration set point; wherein when the production rate is below its predetermined target range, the RRC increases the catalyst feed rate set-point and/or varies the reactor temperature set-point and/or increases monomer concentration set point until a production rate result reasonable progress rate toward its predetermined target range is established, wherein: (v) when the MI result is below its predetermined target range, the RRC increases reactor temperature; and/or (vi) when the MI result is above its predetermined target range, the RRC decreases reactor temperature; wherein: (vii) when the ash content is above its predetermined target range and the MI is below its predetermined target range, the RRC increases the reaction temperature set-point, to reduce ash and increase the MI result; and/or (viii) when the ash content is above its predetermined target range and the MI is above its predetermined target range, the RRC increases the monomer concentration, to reduce ash and decrease the MI result.
The system of claim 2, wherein when at least one subsequently obtained MI result is reasonable with respect to a previously-obtained unreasonable MI result, the RRC updates the MI average obtained at current reaction parameter set-point(s).
The system of claim 2 or claim 3, wherein the hardware associated with controlling reactor temperature includes a cooling system having a variable position coolant valve that incrementally opens and closes to provide more or less cold water flow into a heat exchanger that then cools water jackets of the polymerization reactor.
The system of claim 2 or any one of claims 3-4, wherein the hardware associated with controlling monomer concentration includes one or more monomer feed valves that incrementally open and close as needed to maintain predetermined monomer flow rates into the polymerization reactor.
The system of claim 2 or any one of claims 3-5, wherein the hardware associated with controlling catalyst feed rate includes a semi-continuous shot feeder comprised of a ball-valve that fills with catalyst and then empties said catalyst into the polymerization reactor by turning at a predetermined speed, measured in turns (or drops) per minute.

Description

FIELD Disclosed is a process and system for optimizing polymerization rate and polymer quality during polymerization in a slurry loop reactor. BACKGROUND Polymer production rate and quality in slurry loop reactors are known to be affected by various reaction parameters, such as monomer concentration, catalyst feed rate and reactor temperature. To optimize polymer production rate and quality, one or more of these parameters may be varied. For example, if the production rate is too low, reactor temperature may be increased, within certain limits, to more thoroughly polymerize the monomer(s) within the reactor loop. But if the reactor temperature called for exceeds the limits of the reactor, it can be advantageous to increase the amount of catalyst fed to the reactor, such as by dropping catalyst more frequently into the reactor, to increase polymer production rate Polymer quality is often defined by various physical characteristics of the polymer formed during the polymerization process, such as the molecular weight of the resulting polymer and/or the ash content. For polymers which are formed from primarily olefin monomers, polymer molecular weight can often be expressed by the melt index (MI). Conventionally, loop polymerization reactors are controlled manually, i.e. by one or more operators who must continuously monitor the various reaction parameters as well as the results of those parameters; production rate and polymer quality. However, due to limitations as to the operator's time, it is difficult to efficiently monitor all aspects of the reactor operation and input reaction parameter updates in a manner which optimizes all of the desired polymerization results consistently. As such, either or both of low production rate or off-spec polymer properties can occur. It would be advantageous to have a process and system which automatically monitors and updates polymerization reaction parameters so as to maintain consistent polymerization results. SUMMARY Presented herein is a process for optimizing polymerization of a monomer in a loop polymerization reactor controlled by a reaction rate controller program, comprising continuously and periodically obtaining polymerization results comprising at least melt index (MI), production rate and ash content on the polymerized monomer, the reaction rate controller program (RRC) determining whether each of the polymerization results is within predetermined target ranges for those results, storing recently obtained polymerization results in a computer readable database stored within the RRC, and averaging the recently obtained results with previously stored results, and when at least one of the polymerization results is out-of-range with respect to its predetermined target range, modifying at least one reaction parameter set-point comprising monomer concentration, catalyst feed rate and reactor temperature, and controlling associated hardware for modifying reaction parameter set-point(s) to drive any out-of-range polymerization result(s) toward the predetermined target range for that result. In one form, the process further comprises the RRC assessing the reasonableness of the MI result when the MI result is out-of-range, and if the result is unreasonable, retaining it for comparison to subsequently obtained MI results, without averaging it with previously stored MI results. In this form, when at least one subsequently obtained MI result is reasonable with respect to a previously-obtained unreasonable MI result, the RRC updating the MI average obtained at current reaction parameter set-point(s). In another form, when the production rate is above its predetermined target range, the RRC decreases the catalyst feed rate set-point and/or vary the reactor temperature set-point and/or decrease monomer concentration set point until a production rate result reasonable progress rate toward its predetermined target range is established. In this form, when the MI result is below its predetermined target range, the RRC increases reactor temperature, and when the MI result is above its predetermined target range, the RRC decreases reactor temperature In another form, when the production rate is within its predetermined target range but the MI result is below its predetermined target range, the RRC can increase the catalyst feed rate set-point and/or increase the reactor temperature set-point and/or decrease monomer concentration set point. In yet another form, when the production rate is within its predetermined target range but the MI result is above its predetermined target range, the RRC can decrease the catalyst feed rate set-point and/or decrease the reactor temperature set-point and/or increase monomer concentration set point. In another form, when the production rate is below its predetermined target range, the RRC increases the catalyst feed rate set-point and/or vary the reactor temperature set-point and/or increase monomer concentration set point until a production rate res