Method and apparatus for estimating relative proportion of wood chips species to be fed to a process for producing pulp

Abstract

Improved methods and apparatus for estimating and controlling relative proportion of wood chips originating from a plurality of sources characterized by various wood species, in a mass of wood chips to be fed to a process for producing pulp, use light reflection-related and density-related properties as input in a model characterizing a relation between such wood chip properties and species information. This principle allows efficient monitoring of the variation in wood species composition characterizing the wood chips to be processed, for the purpose of stabilizing chip feeding control and optimizing process parameters adjustment.

1 . A method for estimating relative proportion of wood chips originating from a plurality of sources of wood chips, in a mass of wood chips to be fed to a process for producing pulp, said wood chips of each said source being characterized by one of a pure wood species and a mixture of wood species, said method comprising the steps of: 
 i) estimating a set of wood chip properties characterizing the wood chips of said mass to generate corresponding wood chip properties data, said set including at least one light reflection-related property and at least one density-related property; and    ii) feeding said wood chip properties data at corresponding inputs of a model characterizing a relation between said wood chip properties and said one of a pure species and a mixture of wood species wood chips for each said source, to obtain an estimation of said wood chips relative proportion.    
   
   
       2 . The method of  claim 1 , wherein said at least one density-related property includes one of basic density and bulk density of the wood chips of said mass.  
   
   
       3 . The method of  claim 1 , wherein said at least one density-related property includes basic density and bulk density of the wood chips of said mass.  
   
   
       4 . The method of  claim 1 , wherein said set of wood chip properties further includes moisture content.  
   
   
       5 . The method of  claim 1 , wherein said at least one light reflection-related wood chip property data is expressed as at least one optical parameter representing light reflection characteristics of the wood chips of said mass.  
   
   
       6 . The method of  claim 5 , wherein said optical parameter is luminance.  
   
   
       7 . The method of  claim 5 , wherein said optical parameter is selected from the group consisting of hue, saturation, luminance and darkness indicator.  
   
   
       8 . The method of  claim 7 , wherein said set of wood chip properties further includes moisture content.  
   
   
       9 . The method of  claim 1 , wherein said at least one light reflection-related wood chip property data is expressed as a plurality of optical parameters representing light reflection characteristics of the wood chips of said mass, including hue, saturation and luminance.  
   
   
       10 . The method of  claim 9 , wherein said plurality of optical parameters further include darkness indicator.  
   
   
       11 . The method of  claim 1 , wherein said set of wood chip properties further includes moisture content.  
   
   
       12 . A method for estimating relative proportion of wood chips originating from a plurality sources of wood chips, in a mass of wood chips to be fed to a process for producing pulp, said wood chips of each said source being characterized by one of a pure wood species and a mixture of wood species, said method comprising the steps of: 
 i) estimating a set of wood chip properties characterizing the wood chips of said mass to generate corresponding wood chip properties data, at least a portion of which is obtained by measuring at least one light reflection-related property and at least one density-related property; and    ii) feeding said wood chip properties data at corresponding inputs of a model characterizing a relation between said wood chip properties and said one of a pure species and a mixture of wood species wood chips for each said source, to obtain an estimation of said wood chips relative proportion.    
   
   
       13 . The method of  claim 12 , wherein said at least one density-related property includes one of basic density and bulk density of the wood chips of said mass.  
   
   
       14 . The method of  claim 13 , wherein said step i) includes the steps of: 
 a) measuring weight of the wood chips of said mass;    b) measuring volume of the wood chips of said mass,    c) deriving bulk density data from said measured weight and volume of the wood chips of said mass.    
   
   
       15 . The method of  claim 14 , wherein said step i) further include the steps of: 
 d) measuring moisture content of the wood chips of said mass;    e) deriving basic density data from said measured weight, volume and moisture content of the wood chips of said mass.    
   
   
       16 . The method of  claim 12 , wherein said set of wood chip properties further includes moisture content as estimated by said measured moisture content of the wood chips of said mass.  
   
   
       17 . The method of  claim 1 , wherein said at least one light reflection-related wood chip property data is expressed as at least one optical parameter representing light reflection characteristics of the wood chips of said mass.  
   
   
       18 . The method of  claim 17 , wherein said optical parameter is luminance.  
   
   
       19 . The method of  claim 17 , wherein said optical parameter is selected from the group consisting of hue, saturation, luminance and darkness indicator.  
   
   
       20 . The method of  claim 19 , wherein said set of wood chip properties further includes moisture content.  
   
   
       21 . The method of  claim 12 , wherein said at least one light reflection-related wood chip property data is expressed as a plurality of optical parameters representing light reflection characteristics of the wood chips of said mass, including hue, saturation and luminance.  
   
   
       22 . The method of  claim 21 , wherein said plurality of optical parameters further include darkness indicator.  
   
   
       23 . The method of  claim 12 , wherein said set of wood chip properties further includes moisture content.  
   
   
       24 . An apparatus for estimating relative proportion of wood chips originating from a plurality of sources of wood chips, in a mass of wood chips to be fed to a process for producing pulp, said wood chips of each said source being characterized by one of a pure wood species and a mixture of wood species, said apparatus comprising: 
 illumination means for directing light onto an area of wood chips included in said mass of wood chips, said illuminated wood chips presenting light reflection characteristics being substantially representative of the wood chips of said mass;    an optical imaging device for sensing light reflected from the illuminated wood chips to produce image data representing at least one light reflection-related property characterizing the wood chips of said mass;    a density measuring unit for generating data representing at least one density-related property characterizing the wood chip of said mass; and    a computer programmed with a model characterizing a relation between said wood chip properties and said one of a pure species and a mixture of wood species wood chips for each said source, said computer processing all said data with said model to obtain an estimation of said wood chips relative proportion.    
   
   
       25 . The apparatus of  claim 24 , wherein said at least one density-related property density includes bulk density, said density measuring unit including: 
 a weighing device for measuring weight of at least a representative portion of the wood chips of said mass;    a volume meter for measuring volume of said representative portion of the wood chips of said mass;    a data processor for deriving bulk density data from said measured weight and volume of the wood chips of said mass.    
   
   
       26 . The apparatus of  claim 25 , wherein said data processor is included in said computer.  
   
   
       27 . The apparatus of  claim 24 , wherein said at least one density-related property density includes basic density, said apparatus further comprising: 
 a moisture sensor for measuring moisture content of the wood chip of said mass; said density measuring unit including:    a weighing device for measuring weight of at least a representative portion of the wood chips of said mass;    a volume meter for measuring volume of said representative portion of the wood chips of said mass;    a data processor for deriving basic density data from said measured weight, volume and moisture content of the wood chips of said mass.    
   
   
       28 . The apparatus of  claim 27 , wherein said data processor is included in said computer.  
   
   
       29 . The apparatus of  claim 24 , wherein said set of wood chip properties further includes moisture content, said apparatus further comprising: 
 a moisture sensor for producing data representative of the moisture content of the wood chip of said mass, which data being processed by said computer with said model to obtain the estimation of said wood chips relative proportion.    
   
   
       30 . A method for controlling relative proportion of wood chips originating from a plurality of sources of wood chips discharging to form a mass of wood chips to be fed to a process for producing pulp, said wood chips of each said source being characterized by one of a pure wood species and a mixture of wood species, said method comprising the steps of: 
 i) estimating a set of wood chip properties characterizing the wood chips of said mass to generate corresponding wood chip properties data, said set including at least one light reflection-related property and at least one density-related property;    ii) feeding said wood chip properties data at corresponding inputs of a model characterizing a relation between said wood chip properties and said one of a pure species and a mixture of wood species wood chips for each said source, to obtain estimation data representing said wood chips relative proportion;    iii) comparing said estimation data with predetermined target data to produce error data; and    iv) selectively modifying the discharge rate of one or more of said wood chip sources on the basis of the error data, to adjust the relative proportion of wood chips in said mass.    
   
   
       31 . A system for controlling relative proportion of wood chips originating from a plurality of sources of wood chips in communication with means for discharging thereof to form a mass of wood chips to be fed to a process for producing pulp, said wood chips of each said source being characterized by one of a pure wood species and a mixture of wood species, said system comprising: 
 illumination means for directing light onto an area of wood chips included in said mass of wood chips, said illuminated wood chips presenting light reflection characteristics being substantially representative of the wood chips of said mass;    an optical imaging device for sensing light reflected from the illuminated wood chips to produce image data representing at least one light reflection-related property characterizing the wood chips of said mass;    a density measuring unit for generating data representing at least one density-related property characterizing the wood chip of said mass;    a computer programmed with a model characterizing a relation between said wood chip properties and said one of a pure species and a mixture of wood species wood chips for each said source, said computer processing all said data with said model to obtain estimation data representing said wood chips relative proportion, said computer being further programmed to compare said estimation data with predetermined target data to produce error data; and    a controller operatively connected to said discharging means for selectively modifying the discharge rate of one or more of said wood chip sources on the basis of the error data, to adjust the relative proportion of wood chips in said mass.    
   
   
       32 . The system of  claim 31 , wherein said at least one density-related property density includes bulk density, said density measuring unit including: 
 a weighing device for measuring weight of at least a representative portion of the wood chips of said mass;    a volume meter for measuring volume of said representative portion of the wood chips of said mass;    a data processor for deriving bulk density data from said measured weight and volume of the wood chips of said mass.    
   
   
       33 . The system of  claim 32 , wherein said data processor is included in said computer.  
   
   
       34 . The system of  claim 31 , wherein said at least one density-related property density includes basic density, said system further comprising: 
 a moisture sensor for measuring moisture content of the wood chip of said mass; said density measuring unit including:    a weighing device for measuring weight of at least a representative portion of the wood chips of said mass;    a volume meter for measuring volume of said representative portion of the wood chips of said mass; and    a data processor for deriving basic density data from said measured weight, volume and moisture content of the wood chips of said mass.    
   
   
       35 . The system of  claim 34 , wherein said data processor is included in said computer.  
   
   
       36 . The system of  claim 31 , wherein said set of wood chip properties further includes moisture content, said system further comprising: 
 a moisture sensor for producing data representative of the moisture content of the wood chip of said mass, which data being processed by said computer with said model to obtain the estimation of said wood chips relative proportion.    
   
   
       37 . A software product data recording medium in which program code is stored, which program code will cause a computer to perform a method for estimating relative proportion of wood chips originating from a plurality of sources of wood chips, in a mass of wood chips to be fed to a process for producing pulp, said wood chips of each said source being characterized by one of a pure wood species and a mixture of wood species, said method comprising the steps of: 
 i) estimating a set of wood chip properties characterizing the wood chips of said mass to generate corresponding wood chip properties data, said set including at least one light reflection-related property and at least one density-related property; and    ii) feeding said wood chip properties data at corresponding inputs of a model characterizing a relation between said wood chip properties and said one of a pure species and a mixture of wood species wood chips for each said source, to obtain an estimation of said wood chips relative proportion.