WO2013088184A1

WO2013088184A1 - A method for assessment of benefit of advanced control solutions

Info

Publication number: WO2013088184A1
Application number: PCT/IB2011/003050
Authority: WO
Inventors: Arun Gupta; Eduardo Gallestey; Konrad Stadler; Tarun Prakash Mathur
Original assignee: ABB Research Ltd Switzerland
Current assignee: ABB Research Ltd Switzerland
Priority date: 2011-12-15
Filing date: 2011-12-15
Publication date: 2013-06-20
Anticipated expiration: 2014-06-15

Abstract

The invention relates to a method for assessment of benefit of advanced control solutions. The method of the invention comprises the steps of estimating statistical distributions of the variables and parameters of the process or of the plant thereof, determining the baseline system of the process to estimate the baseline performance of the process or plant thereof. And, to estimate the improved performance of the process or plant thereof, over the baseline performance, by employing the baseline system considering the effects of reduced statistical distribution of the variables and parameters on the process and / or the effects of advanced control solutions and of optimization thereof.

Description

A METHOD FOR ASSESSMENT OF BENEFIT OF ADVANCED

CONTROL SOLUTIONS

FIELD OF THE INVENTION

The invention relates to Advanced Control Solutions, and more particularly to assessment of benefit of Advanced Control Solutions.

BACKGROUND

Generally, new investments are made in an industry based on the potential economic benefits and the associated payback period, and the process industry is no exception to this. In this context, it becomes important to have an assessment of the benefits that could be achieved through possible implementation or changes or adaptation or modification or the like, that involves such investment.

In a process industry, through Advanced Control Solutions, it becomes possible to control or solve multivariable problems. Therefore, the benefits that arise through the implementation of Advanced Control Solutions are enormous. Currently, the assessment of such benefit is done using heuristic rules and / or simplified calculations involving many assumptions, due to which the benefits are either under estimated or over estimated. For instance, the capability of Proportional Integral Derivative (PID) controller is often underestimated, where a PID controller can actually perform much more than what they are usually employed for. Thus, the current practice of assessment of such benefits results in inaccurate assessment of benefits.

Hence, there is a need for a solution with more systematic approach with regard to assessment of benefits, that provide more accurate assessment of benefits and that is more practical in nature. The invention is aimed at providing such solution through which the assessment of benefits becomes more accurate and reliable.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a method for assessment of benefit of Advanced Control Solutions, which is more accurate and reliable. It is another object of the invention to provide a method for assessment of benefit of Advanced Control Solutions, wherein the benefits can be quantified.

It is also an object of the invention to provide a method for assessment of benefit of Advanced Control Solutions, which can estimate current plant performance and improvement over it.

Yet another object of the invention is to provide a method for assessment of benefit of Advanced Control Solutions, which can quantify the likelihood of given performance level of the plant, and of the catastrophic failures thereof.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method for assessment of benefit of advanced control solutions. The method of the invention comprises the steps of estimating statistical distributions of the variables and parameters of the process or of the plant thereof, determining the baseline system of the process to estimate the baseline performance of the process or plant thereof. And, to estimate the improved performance of the process or plant thereof, over the baseline performance, by employing the baseline system considering the effects of reduced statistical distribution of the variables and parameters on the process and / or the effects of advanced control solutions and of optimization thereof.

BRIEF DESCRIPTION OF THE DRAWING

With reference to the accompanying drawing in which:

Fig. 1 depicts the method for assessment of benefit of advanced control solutions, in accordance with the invention.

DETAILED DESCRIPTION

The invention is described herein after with reference to a non exhaustive exemplary embodiment, and as illustrated in Fig. 1. Fig. 1 shows the method (100) for assessment of benefit of advanced control solutions, in accordance with the invention. The data in relation to the process and of the plant are obtained (100). The data in this context include but not limited to one or more of online operating data of the plant, perturbed operating condition data of the plant, e.g., step test data, laboratory data and / or production reports, data related to pricing e.g., cost of raw material, cost of energy, cost of the product (margin price) etc. The data herein include relevant and related variables and parameters of the process and of the plant.

The model of the plant is tuned (102) to estimate the values of the parameters and of the statistical distribution accordingly. The tuning of the model, for instance, may correspond to grey-box process model. Other suitable models can also be applied. Here, the estimation include but not limited to estimating the parameters and of the statistical distribution thereof, input disturbance distribution, output disturbance distribution etc.

The baseline system is determined to estimate the baseline performance of the plant (103) in respect of the process and of the plant. Estimating the baseline performance of the plant is done considering the one or more of the present control strategy as applied to the process or plant, disturbances and of the process behaviour thereof, intervention of the operator etc. Accordingly, the baseline system is being established considering the performances involving controller and / or operator intervention.

At step (104), the effects of a) reduced statistical distribution of the variables and parameters on the process; and b) advanced control and optimization solutions, are determined. With regard to this, simulation is performed on the baseline system with reduced distribution of disturbances and parameters so as to capture the effect on output distribution. Similarly, simulation is performed on the baseline system with the advanced control and optimization solution so as to capture its corresponding effects. The simulation can be performed employing Monte Carlo type engine or by any other suitable ways.

In step (105), the possible shift in the operating condition of the plant is estimated. This may purport to the changes or modifications or adaptations or shifts or the like in respect of the implementation of the advanced control and optimization solution. This aids in providing more realistic assessment of benefits with regard to the advanced control and optimization solution and in relation to the possible shifts from the present operating conditions of the plant.

The benefits of advanced control solutions are assessed (106). This is performed on the basis of having the plant operated at the operating conditions proposed or as laid by the advanced control and / or optimization solutions. The benefits herein may be construed to be tangible in the context of its quantitative information that can be made available. Other measures of such benefits are also within the spectrum of the invention. Some of the benefits that could be possibly assessed include but not limited to increase in production or productivity, reduction in specific energy, reduction in downtime of the plant, increase in the life of the equipment, improved product quality etc,.

Thus the invention provides a method for assessment of benefit of advanced control solutions, which is more accurate and reliable, wherein the benefits can be quantified, and which can quantify the likelihood of given performance level of the plant and of the catastrophic failures thereof.

Going through the same consideration with respect to cement, the invention can be coextensively applied thereto as described before.

Pre-calciner in cement processes is a standard technology applied thereto for de-carbonizing raw meal before it enters the kiln. The degree of de-carbonization increases with temperature. However, the material starts to agglomerate above 940°C, leading to clogging of pre-calciner. The optimal operating condition for pre-calciner operation is to achieve 95-98% de- carbonization, which is typically around 900°C. The deviation from the specified operating conditions implicates less efficient operation and higher shut-down probabilities. An advanced control and / or optimization solution provides benefits in terms of operating the process at most cost effective conditions and meeting the production and quality targets.

The control strategy for pre-calciner is essentially to control the temperature of gas / feed mix leaving the pre-calciner to pre-heaters. For a given feed, the manipulated variable is primary fuel. The input variation in pre-calciner enters as corresponding variation in feed flow, feed composition and flow of air from kiln and tertiary air duct. These variations disturb the process and deviates the temperature from desired set-point thereby initiating control action through primary fuel flow. To assess the current performance of the process or plant and estimate the benefits which can be achieved by implementing advanced control and / or optimization solution, the method of the invention can be employed.

Accordingly, the data of input-output streams and temperature measurements are recorded as time series data. The distributions of parameters in the pre-calciner model that been developed based on first principle or grey-box model, are then estimated using the data. In this example 'mass holdup' parameter is assumed to be constant and parameter representing 'reaction enthalpy' is assumed to be varying with feed composition. Therefore, a single value of mass holdup and a distribution for reaction enthalpy parameter is estimated.

The input and output disturbance distributions are estimated from the nominal operating data. A baseline system establishes current performance of the plant and pertains to baseline performance. The distributions of feed flow and reaction enthalpy are then simulated in closed loop with a controller. The controller is tuned to match the current plant performance achieved through existing control and by inputs from the operator. This closed loop simulation thus represents the baseline system. The baseline system is simulated with reduced distributions in feed flow and the improved plant performance is quantified. These simulations demonstrate the benefits that can be achieved by reducing feed flow variations, e.g. by maintenance of feeder system. The baseline system can be simulated with better tuning of existing controller or advanced control strategy to demonstrate and quantify the achievable performance by controller tuning and advanced control. The optimal operating conditions are calculated to achieve plant performance as estimated, as described herein before. The benefits are calculated as increase in production or productivity, reduction in specific energy consumption etc., due to better performance and shift in operating conditions as suggested by baseline system simulations and advanced control and / or optimization solution.

The invention is not restricted by the preferred embodiment described herein in the description. It is to be noted that the invention is explained by way of exemplary embodiment and is neither exhaustive nor limiting. Certain aspects of the invention that not been elaborated herein in the description are well understood by one skilled in the art. Also, the terms relating to singular form used herein in the description also include its plurality and vice versa, wherever applicable. Any relevant modification or variation, which is not described specifically in the specification are in fact to be construed of being well within the scope of the invention.

Claims

WE CLAIM:

1. A method for assessment of benefit of advanced control solutions, the method comprising the steps of:

estimating statistical distributions of the variables and parameters of the process or of the plant thereof;

determining the baseline system of the said process to estimate the baseline performance of the said process or plant thereof; and

estimating the improved performance of the said process or plant thereof, over the said baseline performance, by employing the said baseline system considering the effects of reduced statistical distribution of the variables and parameters on the said process and / or the effects of advanced control solutions and of optimization thereof.

2. The method as claimed in claim 1, wherein estimating statistical distributions of the variables and parameters comprising obtaining data of the said process or of the plant thereof in relation to perturbed and / or nominal operating conditions.

3. The method as claimed in claim 1 or 2, wherein estimating statistical distributions of the variables and parameters comprising tuning the model of the said plant to estimate the values of the parameters and of the statistical distribution thereof.

4. The method as claimed in claim 3, wherein the said model of the plant is a grey-box model or the like.

5. The method as claimed in claim 1, wherein estimating the baseline performance of the process or plant thereof comprises including one or more of present control strategy, or of disturbances and process behaviour thereof, or of operator intervention.

6. The method as claimed in claim 1, further comprises determining the effects of reduced statistical distribution of the variables and parameters on the process.

7. The method as claimed in claim 1 and 6, further comprises determining the effects of advanced control solutions and of optimization thereof.

8. The method as claimed in any one of the preceding claims, wherein estimating the improved performance of the said process or plant thereof comprising determining the changes or shifts in operating conditions of the plant in relation to the advanced control solutions, over the present operating conditions of the said plant.

9. The method as claimed in any one of the preceding claims, wherein estimating the improved performance of the said process or plant thereof comprising assessing the benefits of employing the advanced control solutions and of the optimization thereof over the present operating conditions of the said plant.

10. A system for performing assessment of benefit of advanced control solutions in accordance with the method as claimed in any one of the preceding claims.