CN112166171B - Conditioning controller for a catalytic olefin unit - Google Patents

Abstract

An advanced conditioning controller for a converter of a catalytic olefin unit is disclosed. A Fluid Catalytic Cracking (FCC) type converter (i.e., a reactor-regenerator) is combined with an ethylene type cold end for product recovery. The tuning controller operates using an advanced tuning control (ARC) application that uses variables such as controlled variables, four disturbance variables, associated variables, and manipulated variables. The ARC application manipulates the fuel oil or tail gas flow to the regenerator in response to expected future steady state values of regenerator bed temperature caused by changes in the values of the selected set of variables.

Description

Conditioning controller for catalytic olefin units

Technical Field

This application claims priority from U.S. provisional application serial No. 62/675452 filed on 2018, month 5, 23 and U.S. non-provisional application serial No. 16/420350 filed on 2019, month 5, 23. The present disclosure relates to catalytic olefin conversion. More specifically, the present disclosure relates to regenerator bed temperature control of a catalytic conversion unit.

Background

Olefins are a class of chemicals such as ethylene, propylene, and butylene. Olefins are building blocks for a variety of products such as plastics, rubbers and solvents. In addition, olefins are produced from natural gas liquids and refinery products such as naphtha, kerosene and gas oil. Olefins can be produced, recovered and converted using a variety of processes. Olefins may be produced using olefin production techniques such as, but not limited to, steam cracking, fluid catalytic crackingChemical (FCC) and catalytic dehydrogenation

To produce. In addition, light olefin recovery techniques can be used to recover olefins. Olefins are converted to higher value products such as, but not limited to, polyethylene, polypropylene, and alkylate. Olefins can be converted using Olefin Conversion Technology (OCT), ethylene dimerization, and Comonomer Production Technology (CPT).

One factor that plays an important role in the operation of catalytic olefin technology is the converter/regenerator bed temperature. The present disclosure relates to the effective control of regenerator bed temperature.

Brief Description of Drawings

For a detailed understanding of the present disclosure, reference should be made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, in which like elements are given like numerals, and wherein:

FIG. 1 depicts an illustrative system diagram 100 utilizing an Advanced Process Control (APC)/Advanced Regulatory Control (ARC) strategy for catalytic olefin conversion, according to one embodiment;

FIG. 2 depicts an illustrative block diagram 200 showing the operation of an APC/ARC strategy according to one embodiment;

FIG. 3 depicts an illustrative DCS screen interface 300 according to one embodiment; and

FIG. 4 depicts another illustrative DCS screen interface 400 according to one embodiment.

Detailed Description

In various aspects, a high level conditioning controller for a converter of a catalytic olefin unit is described in the present disclosure. The catalytic olefin technology described hereafter can provide a process for converting low value olefin streams to valuable propylene and ethylene products. In one instance, the low value olefin stream may comprise mixed butenes, pentenes, fluid Catalytic Cracking (FCC) light gasoline, and coker gasoline. In current designs of catalytic olefin technology, FCC-type converters (i.e., reactor-regenerator) can be combined with an ethylene-type cold end for product recovery. Furthermore, in current designs, catalytic olefin technology may include innovative heat integration features and may be designed for regenerator bed temperature control.

In certain arrangements, catalytic olefin technology works properly when the converter/regenerator bed temperature is 703 ℃. However, when the converter/regenerator bed temperature falls below the design operating point of 703 ℃, excessive afterburning (afterburn) may be experienced in the regenerator portion of the converter and in the flue gas system during initial operation. Thus, a reformer/regenerator bed temperature of 720 ℃ or even 730 ℃ may be required to reduce afterburning.

In addition, the converter/regenerator bed temperature can swing significantly due to disturbances in one or more variables such as feed rate, feed temperature, settler overhead temperature, and stripper column level. In some conventional Fluidized Catalytic Converters (FCC), the feed rate, feed temperature, reactor temperature, or stripper level sometimes vary, and the coke automatically moves in the correct direction to minimize the effect on the converter/regenerator bed temperature. However, in other FCC processes, little fuel is provided by coke on the catalyst and thus the inherent equilibrium mechanism is missing. Embodiments of the present disclosure provide systems and methods for controlling regenerator bed temperature.

Fig. 1 depicts an illustrative system diagram 100 utilizing an Advanced Process Control (APC)/Advanced Regulation Control (ARC) strategy for catalytic olefin conversion. As shown in fig. 1, the regenerator bed temperature controller 102 may be cascaded directly to the flow controller 104 (i.e., FIC controller) of the fuel oil 106 or tail gas 108 feeding the regenerator 110 under regulatory control. In addition, the regenerator 110 may receive combustion air 112 and an olefin feed 118. The regenerator 110 outputs effluent 120, which may be a product, and flue gas 122. The regenerator bed temperature controller 102 and the flow controller 104 are hereinafter interchangeably referred to as TIC controller 102 and FIC controller 104, respectively.

In the APC/ARC mode, the flow controller 104 for the fuel oil 106 or the tail gas 108 can receive a setpoint from an Advanced Process Control (APC) application controller 114. It should be noted that the operator may switch operation from basic TIC control to the APC application controller 114 using a selector on the TIC controller 102 (i.e., a DCS selector) or a local/remote switch. Hereinafter, the terms APC application and ARC application may be used interchangeably. The controller 114 may be a general purpose computer having a processor, memory, and algorithms.

APC applications can include control of manipulated variables such as exhaust gas (W) _TG ) 108 or fuel oil 106 (W) _FO ) A selector 116 of the flow rate. For example, in one case, an initial setting of the manipulated variable can be used to control the flow of fuel oil 106. In addition, APC applications can include controller variables such as regenerator bed temperature (T) and disturbance variables such as feed rate (i.e., feed flow) to the unit (W) _F ) Temperature of feed (T) _F ) Settler top temperature (T) _DT ) Stripper liquid level (S) _L ) And combustion air rate (A) _F ). APC applications can further include a correlating variable such as flue gas excess oxygen composition (O) _PV )。

It should be noted that the basic design of an ARC application may be equivalent to a model predictive controller. The model predictive controller may be used to provide a feed forward element to the TIC controller 102 and may therefore allow the TIC controller 102 to be more active (aggressive) while maintaining control robustness. In a model predictive controller, the control action can be expressed using control equation 1 provided below:

in equation 1 above, "ε" represents the model prediction error, i.e., SP-PV, where PV represents the model predicted steady state value of the Process Variable (PV).

In addition, equation 1 above may correspond to a proportional-integral (P-I) controller. It should be noted that this form of APC/ARC controller can belong to the general class of controllers, namely General Predictive Controllers (GPC). Furthermore, the strategy of a General Predictive Controller (GPC) can be used for small applications and/or situations where model predictions can be derived explicitly. A General Process Controller (GPC) strategy can be further employed, wherein the basic control strategy can be represented using equation 2 provided below.

Further, the basic control strategy can be defined in a discrete form using equation 3 provided below.

Thus, the new set point W for the fuel oil can be determined using equation 4 provided below _FO 。

W _FO ＝W _{FO Current} +ΔW _FO 8230equation 4

In equations 3 and 4 provided above, "Δ W _FO "means the fuel oil set point change from the ARC application, which is regulated by the flue gas excess oxygen composition. "W _{FO Current} "indicates the current value of the fuel oil or fuel gas flow rate set point. "Δ T" represents the set point (T) _SP ) Predicted value (T) from ARC calculation _Computing ) With Δ T = T, bed temperature difference between _SP -T _Computing 。“K ₁ "indicates the change (Δ W) for adjusting the manipulated variable _FO ) A variation suppression parameter of the magnitude. "τ" represents the integration time parameter of the controller, and the 0 and 1 subscripts used with Δ T represent the parameter values for the previous and current time periods.

“G _FO "represents the estimated gain between regenerator bed temperature and the flow of fuel oil (i.e., obtained by steady state step test in a commercial unit) and is calculated using equation 5 provided below.

Similarly, "G" is _TG ", i.e., the estimated gain between the regenerator bed temperature and the flow of the tail gas, can be determined using equation 6 below.

Further, the predicted regenerator bed temperature may be determined as the sum of the current measured temperature and the predicted change due to the change in any or all of the disturbance variables using equation 7 below.

T _Computing ＝T _PV，0 +ΔT _Computing 8230equation 7

In the above equation 7, "T _PV "means a measure of the regenerator bed temperature at a previous time period (or a previous time period). In one case, when ARC execution time is fast, T _PV,0 And T _PV,1 The difference between them may be slight; thus, for implementation purposes, the current T may be used _PV,1 The value replacing the previous value, i.e. T _PV,0 。

Δ T mentioned in equation 7 above _{Calculating out} Indicating an expected future change in regenerator bed temperature due to a change in the disturbance variable. In addition, Δ T, as defined below using equation 8 _Computing Can be viewed as a linear function of the gain between regenerator bed temperature and disturbance variable.

Δ T may be expressed in vector notation using equation 9 provided below _Computing 。

Further, Δ T _Computing Other constants may be included that may allow the operator to select the disturbance variable to be included in the ARC application, as defined below using equation 10.

ΔT _Computing ＝C ₁ *G _F *ΔW _F +C ₂ *G _TF *ΔT _F +C ₃ *G _DT *ΔT _DT +C ₄ *G _SL *ΔS _L +C ₅ *G _A *ΔW _A 8230equation 10

In the above equation 10, in calculating "Δ T _{Calculating out} "constants C1, C when disturbance variables are taken into account during the period ₂ 、C ₃ 、C ₄ And C ₅ May be "1" while calculating Δ T _Computing Constant C during which no disturbance variable is used ₁ 、C ₂ 、C ₃ 、C ₄ And C ₅ May be "0". "Δ W _F "means from time t ₀ To time t ₁ Variation of feed flow to the unit, i.e. W _F1 -W _FO Wherein t is ₁ ＞t ₀ And (t) ₁ -t ₀ ) An ARC time period is defined.

Furthermore, G _F Can be calculated as

Wherein G is _F Represents the estimated steady state gain between regenerator bed temperature and feed flow. Delta T _F Representing the time t from ₀ To time t ₁ Variation T of feed temperature to the unit _F1 -T _FO 。G _TF Can be calculated as

Wherein G is _TF Represents the estimated steady state gain between regenerator bed temperature and feed temperature. Delta T _TD Representing the time t from ₀ To time t ₁ Variation T of the temperature of the top of the settler reaching the unit _TD1 -T _TD0 . Furthermore, G _DT Represents the estimated steady state gain between regenerator bed temperature and settler overhead temperature, and can be determined as

Further, Δ S _L Representing the time t from ₀ To time t ₁ Change of stripper liquid level in unit S _L1 -S _L0 。G _SL Represents the estimated steady state gain between regenerator bed temperature and stripper column liquid level, and can be determined as

ΔW _A Representing the time t from ₀ To time t ₁ Variation W of combustion air flow rate to unit _A1 -W _A0 。G _A Represents an estimated steady state gain between regenerator bed temperature and combustion air flow rate, and can be determined as

Additionally, the method and apparatus for calculating Δ T may be used without departing from the scope of the present disclosure _Computing Other disturbance variables such as, but not limited to, air temperature, gain, and constants may also be included in equation 10. As discussed above, the ARC application may include associated variables. The associated variable may include flue gas excess oxygen composition (O) _PV ) Which can limit the variation of the flue gas flow rate set point. It should be noted that the variation in the flue gas excess oxygen composition may be linearly dependent on the combustion air flow rate variation and the fuel flow rate variation to the regenerator 110. Calculated value of change (Δ W) using fuel oil 106 _FO ) The change in the value of the flue gas excess oxygen composition can be determined using equation 11 or equation 12 below.

ΔO _{Calculating out} ＝G _OA *ΔW _A +G _FO *ΔW _FO 8230equation 12

In equations 11 and 12 provided above, "Δ O _{Calculating out} "indicates the expected future change in the flue gas excess oxygen composition due to a change in the disturbance variable. G _OA An estimated steady state gain between the flue gas excess oxygen composition and the combustion air flow rate is expressed and may be used

And (4) determining. Δ W _A Representing the slave time t ₀ To time t ₁ Variation W of combustion air flow rate to unit _A1 -W _AO Wherein t is ₁ ＞t ₀ And (t) ₁ -t ₀ ) An ARC time period is defined. G _FO Represents an estimated steady state gain between the flue gas excess oxygen composition and the fuel gas flow rate, and may be determined as

ΔW _FO A calculated value representing a change in the fuel gas flow rate from a previous calculation of the fuel gas flow rate.

Such as G as defined in equations 9 and 10 _F 、G _TF 、G _DT 、G _SL And G _A And the parameter G defined in equation 12 _OA And G _FO Can be obtained by steady state step tests in the operating unit. The steady state step test will be described later. Further, upper and lower limits on the flue gas excess oxygen composition may be defined and entered via the DCS field. It should be noted that the fuel supplied to the regenerator 110 may be limited when the calculated change in the flue gas excess oxygen composition forces the oxygen composition to exceed a limit. Therefore, the limit check can be performed using equation 13 below.

ΔO _UP ＝O _UP -O _PV And Δ O _LO ＝O _LO -O _PV 8230equation 13

In the above equation 13,. DELTA.O _UP Represents the flue gas excess oxygen composition value (O) _PV ) With the upper limit of oxygen composition (O) in the flue gas _UP ) Difference therebetween, and Δ O _LO Represents the flue gas excess oxygen composition value (O) _PV ) And lower limit of oxygen composition (O) in flue gas _LO ) The difference between them. Further, O _PV Are process values obtained from analyzers or from laboratory reports.

In one case, when Δ O _{Calculating out} ≥ΔO _UP The change in fuel oil set point can then be limited using equation 14 below.

ΔW _FO ＝ΔW _FO ·(ΔO _UP /ΔO _Computing ) 8230equation 14

Similarly, when Δ O _Computing ≤ΔO _UP The change in fuel oil set point can be limited using equation 15 below.

ΔW _FO ＝ΔW _FO Equation 15 (Δ OLO/Δ O calculation).

When the mobility limit is not violated, the variation in the fuel oil flow rate may not be limited, i.e., full mobility, i.e., AW, may be allowed _FO ＝ΔW _FO . In addition, two separate labels UP may be defined _O2 And LO _O2 To indicate to an operator that the flue gas excess oxygen composition may be active. In one case, when O _PV ≥O _UP At the same time, UP _O2 = on, otherwise UP _O2 And (h) = off. In another case, when O _PV ≥O _LO Time, LO _O2 On, otherwise LO _O2 And (h) = off.

It should be noted that the controller (i.e., TIC controller 102) may have high and low set point limits that may override the controller action when the set point exceeds the limits. The change in the manipulated variable may have upper and lower limits and may require a ramp function to smoothly adjust the set point and provide a bumpless transition from the adjusting action.

As discussed above, such as G can be determined by steady state step testing in the operating unit _F 、G _TF 、G _DT 、G _SL And G _A The parameter (c) of (c). For example, in one case, G may be determined using a steady state step test in the operating unit _F . Furthermore, G may be _F Determined as Δ T/Δ W _F Wherein the delta value of the variable may be determined by a steady state step test on the operating unit or by an operator training simulator system. The steady state step test may include a steady state gain that may be estimated as a control variable, i.e., a ratio of a discrete steady state change in regenerator bed temperature to a step change in a disturbance variable or manipulated variable. It should be noted that the following method can be used to estimate as Δ T/Δ W _F Calculated G _F Steady state gain of。

First, the operation unit can be operated in a stable steady state. In addition, a step change may be made on the feed flow controller. It should be noted that the magnitude of the variation may be consistent with the operation prior to testing. Furthermore, the value of the variable may be in the variation of the overall feed flow and in a steady state (T, W) _F ) Is recorded. Thereafter, the operator may wait until the operating unit reaches a steady state or some stable operation. Then, the value of the new temperature (T) can be recorded after the step change _New ). Further, a change value of the regenerator bed temperature (Δ T = T) may be determined _New -T). It should be noted that Δ W _F The value of (d) may be the difference between the values of the feed flow rate after and before the step change, i.e. aw _F ＝W _{F, new} -W _F . Thereafter, the steady step gain (G) may be applied _F ) Is estimated as the ratio of the differences, i.e., G _F ＝ΔT/ΔW _F 。

It will be apparent to those skilled in the art that the above-described method for determining the gain may be applied to other gains, such as, but not limited to, temperature gains for the flow rates of the fuel oil 106 and the tail gas 108, without departing from the scope of the present disclosure.

FIG. 2 depicts an illustrative block diagram 200 showing the operation of the APC/ARC strategy. The configuration of the controller (i.e., TIC controller 102) may be implemented in a DCS system without requiring additional hardware or software.

First, in step 202, the ARC application may receive one or more inputs from an operator (i.e., manual inputs). The one or more inputs may include an on/off activation of the ARC application, a manipulated variable rejection factor K ₁ And K ₂ Constant C for including variable gain in ARC applications ₁ 、C ₂ 、C ₃ 、C ₄ And C ₅ An on/off binary variable, and an on/off activation parameter for the flue gas excess oxygen composition calculation that regulates the flow rate of the fuel oil 106. In step 204, G may be determined based on the received input _F 、G _TF 、G _DT 、G _SL 、G _FO 、G _TG 、G _OA And G _OF Steady state ofAnd (4) gain. The steady state gain may be calculated using a steady state step test in the operating unit.

The ARC application may then receive one or more process inputs in step 206. Process inputs may include, but are not limited to, feed rate to the unit, feed temperature, settler overhead temperature, stripper level, fuel oil flow, tail gas flow, regenerator bed temperature, flue gas excess oxygen composition, and combustion air rate. Further, in step 208, may be at T ₁ The data is retrieved. At T ₁ The data of (A) may include W _F1 、T _F1 、T _DT1 、S _L1 、G _F1 、G _T1 、T _SP 、T _PV,1 And W _A1 . Similarly, in step 210, T may be ₀ The data is retrieved. At T ₀ The data of (A) may include W _F0 、T _F0 、T _DT0 、S _L0 、G _FO 、G _TG 、T _SP 、T _PV,0 And W _A0 。

In step 212, a time T may be received ₁ And T ₀ The data at (A) calculate the change in the variable value, i.e. Δ W _F1 、ΔT _F1 、ΔT _DT1 And Δ S _L1 . It should be noted that for each predetermined time period t ₁ -t ₀ The ARC application may begin at the beginning of the time period (t) ₀ ) And end of the time period (t) ₁ ) The change in the disturbance variable is calculated. After the calculation, the ARC application may proceed from T in step 214 ₁ Loading T ₀ . Further, in step 216, the change in the value of the variable and the calculated steady state gain and constant (i.e., C) may be used ₁ 、C ₂ 、C ₃ 、C ₄ And C ₅ ) To determine Δ T _{Calculating out} . It should be noted that the value of the constant may be provided by the operator to determine Δ T _Computing . In addition, the operator can set the constant C ₁ 、C ₂ 、C ₃ 、C ₄ And C ₅ To determine which disturbance variable gain can be used to calculate the regenerator bed temperature. In use, the value of the constant may be set to "1", otherwise it may be set to "0".

Then, in step 218, unconstrained variations of the manipulated variables may be computed. May be based on a variation suppression parameter (i.e., K) ₁ ，K ₂ ) And integrating the time parameter (τ) to compute unconstrained variations of the manipulated variable. The unconstrained variation of the manipulated variables may be determined using equation 16 below.

ΔW _FO ＝K ₁ *G _FO *ΔT+1/τ(ΔT ₁ -ΔT ₀ ) 8230equation 16

In step 220, the manipulated variable variation may be constrained based on at least the unconstrained variation of the manipulated variable, the flue gas excess oxygen composition value, and the process value. Thereafter, a set point (i.e., a manipulated variable, FIC, set point) may be calculated in step 222. The set point may be determined using equations 17 and 18 below.

W _FO ＝W _{FO Current} +ΔW _F0 8230equation 17

W _TG ＝W _{TG current} +ΔW _TG 8230equation 18

It should be noted that in step 224, the flue gas excess oxygen composition constraint may be retrieved and used as a flag value. Can be based on input such as O _PV 、O _UP And O _LO To retrieve the flue gas excess oxygen composition. In one case, the flow rate variation may be constrained by a flue gas excess oxygen composition calculation before it can be applied to the FIC controller 104. In addition, the ARC application may communicate the calculated set point to the controller 226. It should be noted that the ARC selector and the manipulated variable selector may feed into the controller 226. Thereafter, the ARC application can vary the fuel oil and tail gas flow rates.

It should be noted that the predicted regenerator bed temperature may be compared to a set point (T) _SP ) A comparison is made and the difference can be used as an error value to determine a manipulated variable (W) _F ) A change in (c). Further, the recommended ARC operating frequency may be once per minute and may be easily adjusted to run slower or faster depending on the quality of control observed. Further, in one case, the ARC set point may be applied to the flow controller 104 through a filter, such as a ramp function, to ensure operationA gentle and undisturbed change in the magnitude of the longitudinal variable.

FIG. 3 depicts an illustrative DCS screen interface 300. The operator may use the DCS screen interface 300 to define all the variables of the ARC application. The DCS screen interface 300 may display variables such as controlled variables 302 of the ARC application. In addition, the DCS screen interface 300 may display a flags field 304 and a measurements field 306 of the variables. The tag field 304 may be selected from the table provided below, which shows the DCS tag associated with the variable of the ARC application.

	Marking	Description of the invention	Unit of
				1	FIC10P01_1	Flow rate of feed	Kg/H
2	FIC10R01_8	Injecting fuel oil into the regenerator	Kg/H
				3	LIC10R01_2	Stripper liquid level	％
4	TI10R01_17	Settler dome *	Degree centigrade
				5	TIC10HO1_3	Temperature of feed	Degree centigrade
6	TIC10R01_25	Temperature of dense bed of converter regenerator	Degree centigrade
				7	FIC10R01_3	Exhaust gas flow rate	Kg/H
8	AI10E03_2A	Flue gas O2 analyzer	Mol％
				9	FI15K01_1	Main air compressor discharge	Nm3/h

The DCS screen interface 300 may also display a target field 308 of the controlled variables 302, which the operator may use to set a target or desired value, and a mode field 310. It should be noted that the mode field 310 may indicate which variable may be used to control the regenerator bed temperature. It should also be noted that in an embodiment, the settler temperature may be replaced by the controller TIC10R01 — 1 set point.

As shown in FIG. 3, the DCS screen interface 300 may further display manipulated variables 312 and set points 314 for the manipulated variables. It should be noted that depending on the configuration of the manipulated variables 312, schemas may include Manual (MAN), automatic (AUTO), cascading (CASCADE), or REMOTE cascading (REMOTE CASCADE). In addition, the DCS screen interface 300 may display an associated variable 316 and a distributed variable 318 having an upper limit field 320, a lower limit field 322, a unit(s) field 324, and an available field 326.

The upper limit field 320 and the lower limit field 322 may be changed by the operator and the labeling constraints may be displayed to the operator as a change in color of the upper limit field 320 and the lower limit field 322. It should be noted that the flag constraint may be displayed when the upper and lower limits are reached, and may change back when the upper and lower limits are normal. The available field 326 may be changed, i.e., on/off, by an operator to activate the adjustment of the fuel set point by calculating the flue gas excess oxygen composition. Further, the operator may use the available field 326 when the gain of the dependent variable may be active in the ARC temperature calculation.

The DCS interface screen 300 may further display an application status field 328, which application status field 328 may be configured as a selector for ARC applications and tuning controls. The operator may use the application status field 328 to set on/off when the ARC application is active or inactive.

FIG. 4 depicts another illustrative DCS screen interface 400. The operator may use the DCS interface screen 400 to enter values for parameters or constants for the ARC application. As shown in fig. 4, the operator may use the DCS interface screen 400 to input the ARC estimated variable gain 402. Further, the DCS interface screen 400 may include an activation field 404, such as an on/off field, that may indicate information about the flow used as a manipulated variable. The DCS interface screen 400 may further display measured values fields 406 and set points fields 408 for disturbance variables, manipulated variables, and controlled variables. It should be noted that the calculated temperature and combustion air flow rate values may also be displayed to the operator. In addition, the DCS interface screen 400 may display an adjustment parameters field 410 to the operator. The adjustment parameters field 410 may include a suppression factor field 412, an integration action field 414, and a Δ W value field 416. It should be noted that the value of the adjustment parameter field 410 may be provided by the operator and may therefore be helpful in adjusting the ARC application.

The DCS interface screen 400 may further display measurement fields for associated variables, a laboratory input field 418, and a laboratory/analyzer field 420. In one case, the operator may enter a laboratory value in laboratory input field 418 when the analyzer may not be operating. It should be noted that the lab entry field 418 and the lab/analyzer field may allow the operator to set values that may be used by the ARC application in the calculations. Further, a set of values may be selected as default values for the gain, constants, and adjustment values. These values can be easily replaced or restored using the restore default value field 422.

The disclosed embodiments include a number of advantages. Various embodiments of an advanced conditioning controller for a converter of a catalytic olefin unit may be disclosed. An advanced tuning model predictive feed forward Advanced Process Control (APC) or advanced tuning control (ARC) function may include feed forward tuning of the regenerator fuel in response to changes in variables of the ARC application, and thus may result in minimizing regenerator bed temperature swings. Thus, the function of the ARC application may allow the regenerator bed temperature to be maintained closer to the desired set point to achieve low afterburning. Further, such systems and methods may include consideration of key constraints on fuel combustion. Such operation of the flue gas mechanical system will therefore result in a more stable operation and an extended lifetime of the flue gas mechanical system.

It will be understood from the foregoing that what has been described includes a process for converting an olefin stream to a product stream. The method may comprise the steps of: feeding at least an olefin feed, a fuel oil and a tail gas to a regenerator to produce an effluent stream; and operating the regenerator. Operating the generator may include the step of determining at least one disturbance variable associated with the regenerator, the at least one disturbance variable being selected from one of: (ii) olefin feed rate, (ii) olefin feed temperature, (iii) settler temperature; and (iv) stripper column level; predicting a change in regenerator bed temperature based on the determined at least one disturbance variable; determining a set point for a flow rate of at least one input to the regenerator based on the predicted change in the regenerator bed temperature, wherein the at least one input is selected from one of: (ii) fuel oil, and (ii) tail gas; the effluent stream is fed to produce a product stream.

In an embodiment, a Distributed Control System (DCS) may be implemented to control the regenerator. As used herein, a DCS is a computer-based control system having a control loop. The automation controllers are distributed among the various components and devices that make up the system. The central operator supervises and controls the operation of the automatic monitoring controller. The automation controller exchanges data with the supervisory control using a suitable communication network.

It will be understood from the foregoing that what has been described also includes a method of controlling the regenerator temperature in the general process of converting an olefin stream to a product stream. The method may comprise the steps of: feeding at least an olefin feed, a fuel oil and a tail gas to a regenerator to produce an effluent stream; operating the regenerator by: determining at least one disturbance variable associated with the regenerator, the at least one disturbance variable selected from one of: (ii) olefin feed rate, (ii) olefin feed temperature, (iii) settler temperature, and (iv) stripper liquid level; predicting a change in a regenerator bed temperature based on the determined at least one disturbance variable; determining a set point for a flow rate of at least one input to the regenerator based on the predicted change in the regenerator bed temperature, wherein the at least one input is selected from one of: (i) fuel oil, and (ii) tail gas; and feeding the effluent stream to produce a product stream. Also, the controller may be implemented in a distributed control system.

Claims (12)

1. A method for controlling regenerator bed temperature of a catalytic olefin unit, the regenerator receiving at least an olefin feed, fuel oil, and a tail gas, the method comprising:

-determining at least one disturbance variable associated with the regenerator, the at least one disturbance variable being selected from one of: (ii) olefin feed rate, (ii) olefin feed temperature, (iii) settler temperature, and (iv) stripper liquid level;

-predicting a change in regenerator bed temperature based on the determined at least one disturbance variable; and

-determining a set point for a flow rate of at least one regenerator input to a regenerator based on the predicted change in regenerator bed temperature, wherein the at least one regenerator input is selected from one of: (i) fuel oil, and (ii) tail gas.

2. The method of claim 1, further comprising:

-determining at least one process input selected from one of fuel oil flow, exhaust gas flow, regenerator bed temperature, flue gas oxygen content, and regenerator combustion air rate, wherein the set point is determined further based on the determined at least one process input.

3. The method of claim 1, further comprising: determining a gain for the regenerator bed temperature for a change in at least one disturbance variable and a change in the at least one regenerator input, wherein the set point is determined further based on the determined gain.

4. The method of claim 1, further comprising:

-determining the excess oxygen content in the flue gas; and

-constraining the set point based on the determined excess oxygen content.

5. The method of claim 1, further comprising:

-transmitting the determined set point to a controller; and

-adjusting the valve to the determined set point obtained using the controller.

6. The method of claim 1, further comprising: displaying the determined set point to a human controller.

7. A system for converting an olefin feed to a product stream, comprising:

-a regenerator receiving a fuel oil feed, a tail gas feed, an olefin feed and combustion air;

-a controller controlling the flow of the fuel oil feed and the tail gas feed; and

-an application controller in signal communication with the controller, the application controller configured to:

-determining at least one disturbance variable associated with the regenerator, the at least one disturbance variable being selected from one of: (ii) olefin feed rate, (ii) olefin feed temperature, (iii) settler temperature, and (iv) stripper column liquid level;

-predicting a change in regenerator bed temperature based on the determined at least one disturbance variable; and

-determining a setpoint for a flow rate of at least one regenerator input to a regenerator based on the predicted change in regenerator bed temperature, wherein the at least one regenerator input is selected from one of: (i) a fuel oil feed, and (ii) a tail gas feed.

8. A method of controlling regenerator temperature in a general process for converting an olefin stream to a product stream, comprising:

-feeding at least an olefin feed, a fuel oil feed and a tail gas feed to a regenerator to produce an effluent stream;

-operating the regenerator by:

-determining at least one disturbance variable associated with the regenerator, the at least one disturbance variable being selected from one of: (ii) olefin feed rate, (ii) olefin feed temperature, (iii) settler temperature, and (iv) stripper column liquid level;

-predicting a change in regenerator bed temperature based on the determined at least one disturbance variable;

-determining a set point for a flow rate of at least one input to the regenerator based on the predicted change in the regenerator bed temperature, wherein the at least one input is selected from one of: (ii) fuel oil, and (ii) tail gas; and

-feeding the effluent stream to produce a product stream.

9. The method of claim 8, further comprising controlling the flow of the fuel oil feed and the tail gas feed using a controller.

10. The method of claim 9, wherein the controller is implemented in a distributed control system.

11. A method of converting an olefin stream to a product stream, comprising:

-feeding at least an olefin feed, fuel oil and tail gas to a regenerator to produce an effluent stream;

-operating the regenerator by:

-determining at least one disturbance variable associated with the regenerator, the at least one disturbance variable being selected from one of: (ii) olefin feed rate, (ii) olefin feed temperature, (iii) settler temperature, and (iv) stripper column liquid level;

-predicting a change in regenerator bed temperature based on the determined at least one disturbance variable;

-determining a set point for a flow rate of at least one input to the regenerator based on the predicted change in the regenerator bed temperature, wherein the at least one input is selected from one of: (ii) fuel oil, and (ii) tail gas; and

-feeding the effluent stream to produce a product stream.

12. The method of claim 11, further comprising implementing a distributed control system to control the regenerator.

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