Method of and control system for monitoring a process of circulation of solid material in a circulating fluidized bed reactor

Abstract

A method of monitoring circulation of solid material in a circulating fluidized bed reactor including a reaction chamber, at least one solid material separator, and a return path between the separator and the chamber. The method includes selecting process variables of the process of circulating of solid material in the return path, and selecting performance indicators of the process of circulation of solid material amongst the selected process variables for each performance indicator of the process of circulation of material, creating a multivariate model for each performance indicator, using history data of the process variables and the performance indicators, determining a modelled value of the performance indicators, by applying current measured values of the process variables to the multivariate model, and comparing the modelled value of each performance indicator to a respective measured value and inspecting a presence of an anomaly between the modelled value and the respective measured value.

1 .- 21 . (canceled) 
     
     
         22 . A method of monitoring a process of circulation of solid material in a circulating fluidized bed reactor, the reactor comprising a reaction chamber, at least one solid material separator, a return path between the at least one solid material separator and the reaction chamber and, in which method, the process of circulation of the solid material comprises arranging solid material to be entrained by gas flow in the reaction chamber, and to entrain further from the reaction chamber to the at least one solid material separator and passing solid material from the solid material separator via a return path to the reaction chamber, the method comprising the following steps:
 (a) selecting process variables of the process of circulation of the solid material in the return path, and selecting performance indicators of the process of circulation of the solid material amongst the selected process variables for each performance indicator of the process of circulation of the solid material;   (b) creating a multivariate model for each performance indicator, using history data of the process variables and the performance indicators of the process of circulation of the solid material;   (c) determining a modelled value of the performance indicators, by applying current measured values of the process variables to the multivariate model; and   (d) comparing the modelled value of each performance indicator to a respective measured value of each performance indicator and inspecting a presence of an anomaly between the modelled value and the respective measured value.   
     
     
         23 . A method according to  claim 22 , wherein the multivariate model is updated after a period of time triggered by a lapse of a constant predetermined time interval, or by a trigger input. 
     
     
         24 . A method according to  claim 22 , wherein, when the reactor comprises at least a first return path between a first solid material separator and the reaction chamber and a second return path between a second solid material separator and the reaction chamber, the method further comprises separately performing the method concerning the process of circulation of the solid material in the first return path and the method concerning the process of circulation of the solid material in the second return path. 
     
     
         25 . A method according to  claim 22 , wherein the multivariate model is a multivariate linear regression having a first number (N) of measured observations of each process variable and a second number (P) of different process variables of the process of circulation of solid material as follows: 
       
         
           
             
               
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         where i=1, 2, . . . N, and 
         the method further comprising reading history data of y i , x i1 , x i2 , . . . , x ip  where y=a performance indicator and x i,1 , x i,2 , . . . , x i,p  are process variables, solving a constant b 0  and factors b 1 , b 2 , . . . , b P , and performing a fitting process by minimizing a sum of squares of vertical deviations from each data point to a line that fits best for the history data. 
       
     
     
         26 . A method according to  claim 25 , wherein the first number of measured observations N is at least ten times the second number (P) of different process variables. 
     
     
         27 . A method according to  claim 22 , wherein a risk index for each performance indicator is calculated using information of a presence of the anomaly. 
     
     
         28 . A method according to  claim 27 , wherein calculating the risk index for each performance indicator uses an anomaly between the modelled value and the respective measured value. 
     
     
         29 . A method according to  claim 22 , wherein the process of circulation of the solid material comprises passing the solid material from the solid material separator directly to the reaction chamber via a loop seal in the return path, and further comprising selecting:
 (i) a pressure difference of the loop seal in the return path of the circulation of the solid material; and   (ii) a temperature in the loop seal in the return path in the circulation of the solid material,   
       as the performance indicators of the process in step (a). 
     
     
         30 . A method according to  claim 29 , wherein:
 (iii) process variables of the performance indicator of the pressure difference of the loop seal in the return path comprise an aggregate reaction gas flow rate fed into the reactor, temperature of a product gas upstream the loop seal, and bed temperature in the reaction chamber, and   (iv) process variables of the performance indicator of temperature in the loop seal in the return path in the circulation of the solid material comprise an aggregate reaction gas flow rate fed into the reactor, a temperature of product gas upstream of the loop seal, and a bed temperature in the reaction chamber.   
     
     
         31 . A method according to  claim 30 , wherein the aggregate reaction gas flow rate is total flow rate of gas flows into the reaction chamber. 
     
     
         32 . A method according to  claim 30 , wherein the bed temperature is an average bed temperature in the reaction chamber, which is calculated from at least two measurement points in the reaction chamber, at least one of which is at a grid level of the reaction chamber. 
     
     
         33 . A method according to  claim 22 , wherein the process of circulation of the solid material comprises passing the solid material from the solid material separator via a fluidized bed heat exchanger to the reaction chamber, and further comprising selecting:
 (i) a pressure difference of a loop seal in the return path in the circulation of the solid material;   (ii) a temperature in the loop seal in the return path in the circulation of the solid material;   (iii) a pressure difference of the fluidized bed heat exchanger; and   (iv) a temperature of the solid material downstream of a fluidized bed heat exchange unit in the fluidized bed heat exchanger,   
       as the performance indicators of the process in step (a). 
     
     
         34 . A method according to  claim 33 , wherein:
 (v) process variables of the performance indicator of a pressure difference of the loop seal in the return path comprise an aggregate reaction gas flow rate fed into the reactor, a temperature of a product gas upstream the loop seal, and a bed temperature in the reaction chamber,   
       (vi) process variables of the performance indicator of a temperature in the loop seal in the return path in the circulation of the solid material comprise an aggregate reaction gas flow rate fed into the reactor, a temperature of a product gas upstream of the loop seal, and a bed temperature in the reaction chamber,
 (vii) process variables of the performance indicator of a pressure difference of the fluidized bed heat exchanger comprise an aggregate reaction gas flow rate fed into the reactor, a temperature in the loop seal in the return path in the circulation of the solid material, a pressure difference of the loop seal, a gas flow rate to the fluidized bed heat exchanger, and a bed temperature in the reaction chamber, and 
 
       (viii) process variables of the performance indicator of the temperature of the fluidized bed heat exchanger comprise an aggregate reaction gas flow rate fed into the reactor, a temperature in the loop seal in the return path, a pressure difference of the loop seal, a gas flow rate to the fluidized bed heat exchanger, and a bed temperature in the reaction chamber. 
     
     
         35 . A method according to  claim 34 , wherein the aggregate reaction gas flow rate is a total flow rate of gas flows into the reaction chamber. 
     
     
         36 . A method according to  claim 34 , wherein the bed temperature is an average bed temperature in the reaction chamber, which is calculated from at least two measurement points in the reaction chamber, at least one of which is at a grid level of the reaction chamber. 
     
     
         37 . A method according to  claim 22 , wherein creating the multivariate model comprises:
 measuring values of predetermined process variables, storing the measured values of the predetermined process variables with a time stamp, thus, forming the history data of the process variables;   measuring values of the performance indicator and storing the measured values of the performance indicator with a time stamp, thus, forming the history data of performance indicators; and   selecting valid history data using predetermined data filters.   
     
     
         38 . A method according to  claim 37 , wherein the data filters are configured to approve data that is not older than two months. 
     
     
         39 . A method according to  claim 37 , wherein the data filters are configured to filter out from history data at least any data from shut down situations and from any abnormal operation, based on predefined limits for input variables or external information of abnormal operation. 
     
     
         40 . A method according to  claim 37 , wherein the data filters are configured to approve data that is older than a pre-set quarantine time. 
     
     
         41 . A method according to  claim 40 , wherein the data filters are configured to approve data that is older than two weeks. 
     
     
         42 . A control system for monitoring a process of circulation of solid material in a circulating fluidized bed reactor between a reaction chamber and at least one solid material separator, and to the reaction chamber via a return path comprising a loop seal, the control system comprising:
 a performance modelling unit comprising:   (a) access to source history data of performance indicators of the process of circulation of the solid material in the return path and process variables for each performance indicator;   (b) a multivariate model for each performance indicator; and   (c) executable instructions which, when executed in the control system, update the multivariate model for each performance indicator, using history data of predetermined process variables and the performance indicators of the process of circulation of the solid material, resulting in a calibrated multivariate model; and   a performance diagnostic module comprising:
 (a) inputs for receiving measurement data of process variables and performance indicators of the process of circulation of the solid material; and 
 (b) executable instructions which, when executed in the control system,
 (i) determine a modelled value of the performance indicators, by applying current measured values of the process variables to the calibrated multivariate model; and 
 (ii) compare the modelled value of each performance indicator to a measured respective value of the performance indicator and inspecting a presence of an anomaly between the modelled value and the measured respective value. 
 
   
     
     
         43 . A control system according to  claim 42 , further comprising measurement sensors for at least the following process variables:
 pressure sensors for measuring a pressure drop in the loop seal;   a product gas temperature sensor downstream of the solid material separator; and   sensors for determining an aggregate gas flow rate to the reactor and bed temperature in the reaction chamber of the reactor.   
     
     
         44 . A control system according to  claim 42 , further comprising:
 a fluidized bed heat exchanger in the return path;   measurement sensors for at least following process variables:
 pressure sensors for measuring a pressure drop in the loop seal; 
 a temperature sensor in the loop seal; 
 a product gas temperature sensor downstream of the solid material separator; 
 pressure sensors for measuring a pressure drop in the fluidized bed heat exchanger; 
 temperature sensors for measuring temperature of solid material downstream of a heat exchange unit in the fluidized bed heat exchanger; and 
 sensors for determining an aggregate gas flow rate to the reactor and bed temperature in the reaction chamber of the reactor.