Multipass comminution process to produce precision wood particles of uniform size and shape with disrupted grain structure from wood chips
A process of comminution of wood chips (C) having a grain direction to produce a mixture of wood particles (P), wherein the wood chips are characterized by an average length dimension (L C ) as measured substantially parallel to the grain, an average width dimension (W C ) as measured normal to L C and aligned cross grain, and an average height dimension (H C ) as measured normal to W C and L C , and wherein the comminution process comprises the step of feeding the wood chips in a direction of travel substantially randomly to the grain direction one or more times through a counter rotating pair of intermeshing arrays of cutting discs (D) arrayed axially perpendicular to the direction of wood chip travel.
1. A process of comminution of wood chips (C) having a grain direction to produce a mixture of wood particles (P), wherein the wood chips are characterized by an average length dimension (L C ) as measured substantially parallel to the grain, an average width dimension (W C ) as measured normal to L C and aligned cross grain, and an average height dimension (H C ) as measured normal to W C and L C , wherein W C >H C , and wherein the comminution process comprises the step of feeding the wood chips in a direction of travel substantially randomly to the grain direction one or more times through a counter rotating pair of intermeshing arrays of cutting discs (D) arrayed axially perpendicular to the direction of wood chip travel.
2. The process of claim 1 , wherein the wood chips are further characterized by having a retained field moisture content of greater than 30% dry weight basis.
3. The comminution process of claim 1 , wherein the cutting discs have a uniform thickness (T D ).
4. The comminution process of claim 1 , wherein the cutting discs have a non-uniform thickness.
5. The comminution process of claim 3 , wherein at least one of L C , W C , and H C is greater than T D .
6. The comminution process of claim 5 , wherein: T D ≧H C .
7. The comminution process of claim 6 , wherein: T D ÷H C =4 or less.
8. The comminution process of claim 7 , wherein: T D ÷H C =2 or less.
9. The comminution process of claim 3 , wherein: 1/32 inch<T D <¾ inch.
10. The comminution process of claim 1 , comprising the step of feeding the wood chips in a direction of travel substantially randomly to the grain direction through more than one counter rotating pairs of intermeshing arrays of cutting discs.
11. The comminution process of claim 10 , comprising the step of feeding the wood chips in a direction of travel substantially randomly to the grain direction sequentially through at least first and second counter rotating pairs of intermeshing arrays of cutting discs (D 1 and D 2 ).
12. The comminution process of claim 11 , wherein the first cutting discs D 1 have a uniform thickness (T D1 ) and the second cutting discs D 2 have a uniform thickness (T D2 ).
13. The comminution process of claim 12 , wherein T D1 >T D2 .
14. The comminution process of claim 13 , wherein: ⅛ inch<T D1 <1.5 inch.
15. The comminution process of claim 13 , wherein: 1/32 inch<T D2 <¾ inch.
16. The comminution process of claim 1 , wherein the wood particles (P) are characterized by a length dimension (L P ) aligned substantially parallel to the grain, a width dimension (W P )normal to L P and aligned cross grain, a height dimension (H P ) normal to W P and L P , L P ×H P dimensions defining two side surfaces characterized by substantially intact longitudinally arrayed fibers, W P ×H P dimensions defining two cross-grain end surfaces characterized individually as aligned either normal to the grain or oblique to the grain, wherein a majority of the W P ×H P surfaces aligned oblique to the grain have end checking, and L P ×W P dimensions defining two parallel top and bottom surfaces.
17. The comminution process of claim 16 , wherein a majority of the W P ×H P surfaces in the mixture of wood particles have end checking.
18. The comminution process of claim 1 , wherein the mixture of wood particles is characterized by a substantially uniform size distribution profile as determined by the following protocol:
drying approximately 1000 g of the wood particles to constant weight at 110° F.;
pouring 400 g of the dried wood particles into a stacked screen assembly consisting of in a contiguous size-ordered array: a top ⅜-inch screen having 9.53 mm nominal sieve openings, a No. 4 screen having 4.75 mm nominal sieve openings, a No. 10 screen having 2.00 mm nominal sieve openings, a No. 16 screen having 1.18 mm nominal sieve openings, a No. 20 screen having 0.84 mm nominal sieve openings, a No. 35 screen having 0.50 mm nominal sieve openings, a No. 50 screen having 0.30 mm nominal sieve openings, a No. 100 screen having 0.15 mm nominal sieve openings, and a bottom pan;
shaking the stacked screen assembly for 10 minutes on a motorized tapping sieve shaker;
weighing the wood particles that are retained on each of the screens; and
determining that the wood particle mixture is characterized by a substantially uniform size range if the sum of the weights of wood particles retained on any contiguous five of the screens exceeds 320 g in total.
19. The comminution process of claim 1 , wherein the mixture of wood particles is characterized by a substantially uniform size distribution profile as determined by the following protocol:
drying approximately 1000 g of the wood particles to constant weight at 110° F.;
pouring 400 g of the dried wood particles into a stacked screen assembly consisting of in a contiguous size-ordered array: a top 1-inch screen having 25.00 mm nominal sieve openings, a ½-inch screen having 12.50 mm nominal sieve openings, a ⅜-inch screen having 9.53 mm nominal sieve openings, a ¼-inch screen having 6.30 mm nominal sieve openings, a No. 4 screen having 4.75 mm nominal sieve openings, a No. 8 screen having 2.38 mm nominal sieve openings, a No. 10 screen having 2.00 mm nominal sieve openings, a No. 16 screen having 1.18 mm nominal sieve openings, a No. 20 screen having 0.84 mm nominal sieve openings, and a bottom pan;
shaking the stacked screen assembly for 10 minutes on a motorized tapping sieve shaker;
weighing the wood particles that are retained on each of the screens; and
determining that the wood particle mixture is characterized by a substantially uniform size range if the sum of the weights of wood particles retained on any contiguous five of the screens exceeds 320 g in total.
20. The comminution process of claim 1 , wherein the mixture of wood particles is characterized by a substantially uniform size distribution profile as determined by the following protocol:
drying approximately 1000 g of the wood particles to constant weight at 110° F.;
pouring 400 g of the dried wood particles into a stacked screen assembly consisting of in a contiguous size-ordered array: a top 3-inch screen having 75.00 mm nominal sieve openings, a 1.5-inch screen having 37.50 mm nominal sieve openings, a 1-inch screen having 25.00 mm nominal sieve openings, a ½-inch screen having 12.50 mm nominal sieve openings, a ¼-inch screen having 6.30 mm nominal sieve openings, a ⅛-inch screen having 3.18 mm nominal sieve openings, a No. 16 screen having 1.18 mm nominal sieve openings, and a bottom pan;
shaking the stacked screen assembly for 10 minutes on a motorized tapping sieve shaker;
weighing the wood particles that are retained on each of the screens; and
determining that the wood particle mixture is characterized by a substantially uniform size range if the sum of the weights of wood particles retained on any contiguous five of the screens exceeds 320 g in total.