GRICULTuPE ROOM -.16710 ENGINEERING CALCULATIONS rep Mt DISTILLATION Of THE FURFURAL-WATEI? SYSTEM October 1959 FOREST PRO1JUCTS LABORATORY UNITED STATES DEPARTMENT OF AGRICULTURE MADISON 5. WISCONSIN FOREST SERVICE In Cooperation with the University of Wisconsin
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GRICULTuPE ROOM-.16710
ENGINEERING CALCULATIONS rep
Mt DISTILLATION Of THEFURFURAL-WATEI? SYSTEMOctober 1959
FOREST PRO1JUCTS LABORATORY UNITED STATES DEPARTMENT OF AGRICULTURE
MADISON 5. WISCONSIN FOREST SERVICE
In Cooperation with the University of Wisconsin
ENGINEERING CALCULATIONS FOR THE DISTILLATION
OF THE FURFURAL-WATER SYSTEM
By
J. F. HARRIS, Chemical Engineerand
J. M. SMUK, Chemical Engineer
Forest Products Laboratory, 1 Forest ServiceU. S. Department of Agriculture
Introduction
Process design calculations being carried out at the U. S. ForestProducts Laboratory to obtain optimum operating conditions for apilot-plant furfural reactor required data on high-pressure, vapor-liquid equilibrium for the furfural-water system. While the litera-ture yielded some data for pressures up to 9.5 atmospheres, theprocessing investigations involved pressures up to about 20 atmo-spheres. Part I of this report outlines how the existing data were'extrapolated and gives the results of this extrapolation.
The important results of the calculations concerning the recoveryof furfural by distillation at atmospheric pressure are presentedin Part 2. Also included in Part 2 is a calculation procedure forselecting equipment of optimum size. The procedure is elucidatedwith an example calculation.
1—Maintained at Madison, Wis. , in cooperation with the University of
Wisconsin.
Report No. 2070 -1-
A
PART 1: EXTRAPOLATION OF VAPOR-LIQUID EQUILIBRIUM DATA
Nomenclature i
The nomenclature used in the extrapolation of vapor-liquid equilibriumdata is as follows:
p - partial pressure - atmospheres.n- - total pressure - atmospheresn - gram - molsR - Universal Gas Constant = 1.987
cals
gm. mol - °KT temperature - °Ky liquid activity coefficientx mol fraction in the liquidy mol fraction in the vaporP vapor pressure of pure component atmospheres
AFT - heat of mixing - ,calsgm. - mol
A - Van-Laar coefficientsB
Subscripts
w - waterF - furfurala - azeotrope
T - boiling point of waterws
Basic Equations
PF + Pw = IT
PF = riF RTV
p = n w RTw
YF xF PF = YF Tr = PF
Yw xw Pw = Yw ir = Pw
Report No. 2070 -2-
V
Vapor pressuthe Internati
re data for water in the range 100° to 300° C. , taken fromonal Critical Tables, 2 was fitted to the functional form,
In Pw a—T + b, by the method of least squares to obtain the constants
in equation (9).
The fopublic
llowing vapor pressure equation for furfural was taken from aation by Dunlop and Peters. 3
r
r
(5 in yy)
OT
AH
RT 2 (6)
log 'yF Bxw2
(7)[xw+ ( i.:6!) xl- ]2
Axw2log y (8)w
(L1k ) xw + x Fj2
Data--Values and Sources.
= 4731.6 In Pw + 12.7172T (9)
5086. 4 In PF =
+ 11. 6926T
apor-Liquid Equilibrium
When this work was begun, only one source of data for the homogeneoussystem was known to be available._4 Subsequently, some Russian
.International Critical Tables, III, 233 (1928)._Dunlop, A. P. and Peters, F. N. "The Furans" p. 315. Reinhold,
New York, 1953.
!Curtis, R. G. , and Hatt, H. H. Australian Journal of Science Research,A, 1, 213 (1948).
Report No. 2070 -3-
(10)
V
data5 became available but were not used in the extrapolation. Theextrapolation was based on experimental data for pressures of 5.97,7.60, and 9.51 atmospheres. At each of these pressures the systemexhibits a homogeneous azeotrope. Data taken at these pressuresare included in table 3.
Method of Extrapolation
Correlation of Experimental Data
Using the experimental data of Curtis and Hatt 4— and equations (1), (2),(3), (4), and (5), values of y F and yw were calculated in the concen-
tration range of interest, 0-10 mol percent. The results of thesecalculations are listed in table 3. Correlations of y F as a function
of xF at the three pressures are shown in figures 1, 2, and 3. These
curves were obtained in the following manner:
The Van-Laar equations, (7) and (8), show that
B = [ln yF ]xF 0
andA = [ln yvv ] xw 0
According to (6), both A and B should plot as straightline functions of
1 if AH is considered constant.T
Therefore, correlation was done by fitting the Van-Laar functionalform to the data, with the restriction that the constants A and B hadto be straightline functions of 1 . The values of B were Calculated
Tfrom the intercept values, and values of A from the value of ym, at
y F = 0.09, Best fit of the curves was judged by visual inspection.The final values selected for A and B are given in table 1.
5Mel' nikov, N. P. , and Tsirlin, Yu. Zhur Priklad Khim. 29 (9)1456 (1956).
Report No. 2070 -4-
(8).
r
Extrapolation Procedure
sing the method of Carlson and Coburn, 6—temperature difference between the boiling
d the boiling point of water at the same pres-thus A and B could be considered constant_ange of interest, varying only with the tern-
el.
The values of A and B used at each pressure were obtained from the
-0.20505 3X 10 + 0.9017T
0.9091 X 10 3 - 0.60886
(12)T
The value of T to be used with these equations is the saturation tempera-ture of water at the particular pressure involved. The constants usedin equations (11) and (12) were evaluated by fitting the experimentalvalues of A and B to the functional form, using the least mean squaresmethod. Calculated values used for each pressure are listed in table1.
The talculation procedure for obtaining x-y points was as follows:
1. At a chosen Tr and x F, the values of A and B were availablefrom table 1.
2. Assuming a T, the vapor pressures P F and Pw were cal-
culated from equations (9) and (10).
3. Values of y F and yw were calculated from equations (7) and
4. The partial pressures pw and pF were calculated fromequations (4) and (5).
5. The values of pw and pF must satisfy equation (1); if not, a
new temperature must be assumed in step (2) and the calculationreiterated until equation (1) is satisfied.
6—Hougen, 0. A., and Watson, K. M. Chemical Process Principles,
Vol II, Chapter XV. John Wiley and Sons, New York (1947).Report No. 2070 -5-
A preliminary estimate, uindicated that only a smallpoint of the azeotrope ansure would be expected;over the concentration rperature (pressure) lev
equations:
A-
6. The correct values of pw and p F from step (5) were used in
equations (2) and (3) to obtain the values of yF.
Results
The numerical work was set up for processing on an electronic computer.Results are listed in table 2 and presented graphically in figure 4.
Figures 5, 6, and 7 show a comparison of the calculated values withthe original experimental data used to make the extrapolation.
Comparison of the calculated values with the more recent Russian data
listed in table 9 reveals large differences. This is to be expected,as the Russian data vary considerably from the data of Curtis andHatt used to make the calculation. Unfortunately, no equilibriumtemperature measurements were included in the Russian work. Thus,it was not possible to extrapolate it over the concentration range of
interest.
PART 2: DISTILLATION AT ATMOSPHERIC PRESSURE
Nomenclature
Nomenclature used in the following distillation calculations is as fol-
lows:H - enthalpy of vapor - B.t.u. per lb.
h enthalpy of liquid - B.t.u. per lb.w reflux - lb. per hr.D - distillate - lb. per hr.s - bottoms - lb. per hr.3 - vapor - lb. per hr.r recovery - percentF - feed - lb. per hr.G - mass velocity - lb. per ft.
2-hr.
L - tower diameter - inchesq heat load - B. t. u.C tower cost - $ per platea - cross-sectional tower area - ft. 2
B - vertical coordinate of operating point for rectifying sectionon the Ponchon -Savarit Diagram - B. t. u.
Report No. 2070 -6-
X - vertical coordinate of operating point for stripping sectionon the Ponchon-Savarit Diagram - B.t.u.
a - relative volatility
Subscripts
c - condenserbottoms
n nth plate1 - top plateD distillatew water
Plate and Energy Calculations
Although the fractionation of aqueous furfural solutions is complicatedby the formation of an azeotrope at a 35 percent furfural content, itnevertheless is possible to separate pure furfural by distillation atatmospheric pressure. This is due to the partially miscible liquidsystem formed by condensing vapors that contain more than 18.1 per-cent furfural and the accompanying enrichment that takes place inthe denser phase. Solutions containing less than 18.1 percent of fur-fural can be rectified to give an 84.1 percent furfural product and abottom with practically zero furfural content. The product of rec-tification, which has passed the azeotrope composition (35 percentof furfural) because of enrichment on condensing, is then suitablefor further processing in a stripper where essentially pure furfuralis obtained.
Determination of the plate and energy requirements for this two-tower distillation system was made by the Ponchon-Savarit method.The problem was divided into two parts corresponding to the azeo-trope column (where the dilute solution is concentrated to yield atwo-phase liquid product) and the dehydrating column (where pure fur-fural is stripped from the 84.1 percent furfural feed).
Azeot rope Column
In the derivation of furfural solutions from pentose-containing materials,the reaction kinetics and processing conditions limit the possible feed
Report No. 2070 -7-
concentrations to the azeotrope column to less than 7 percent of fur-fural. In rectifying such feeds, the condensed overhead vapors yielda two-phase liquid containing 84.1 percent of furfural in the denserphase and 18.1 percent in the lighter phase. The lighter phase is re-fluxed to the azeotrope tower, while the heavy phase is sent to thedehydrator. It is possible to describe the operation of the azeotropetower if the vapor-liquid equilibrium relationship is known and thefollowing four variables are specified: Feed composition, enthalpyof the feed, reflux ratio, and recovery. In the analysis of theazeotrope tower, the range of these variables was:
The values for the enthalpy of the feed correspond to feed conditionsfrom below saturation to slightly above saturation. In the solution ofthe azeotrope problem to find the plate and energy requirements forthe variables listed above, the following equations were used:
(100 - x) y
(100 - y) x
H = -7.48 y + 1155
h = -.7 x + 180
h - hF. H - h
- xF y - x
3cD - Y1 B - H1
Yl - hw
w XI) yl — =D Yl - xw
Report No. 2070 -8-
r
81, 997.5 + xn- 1096.13]
- 6.78 xn + B + 449.1
75 xs - yn (x - 180 + 7.48 xs)
- 6. 78 yn - .7 xs - + 1155
Yn+1
xn+1
r- D D [100]xF F
Calculation was c arried out by the following procedure:
1. Dete rmination of the tie line through a given xF and HF.
A. Assume x lies on the tie line and find the equilibriumy value from:
- (100 - x) y
(100 - y) x
B. Compute the corresponding h, H, h F., and HF by:
h = - 0.7 x + 180
H= - 7.48 y + 1155
C. Check the computed values
h - h F H - h
x - xFy - x
D. (a) If the assumed x satisfied the equation, then it lieson the tie line that passes through (x F, HF).
(b) If the equation is not satisfied, a new x must beassumed and the calculation repeated.
2. Minimum reflux ratio
A. Extrapolate the tie line determined in step 1 throughxD to obtain the operating point (X D, B).
9
Report No. 2070 -9-
B. Solve the following two equations for yi and Hi:
qcxD
tY1 k--D– + hD) - H1
Yl xw H1 - hw
H = - 7.48 y + 1155
and w 39) - Y1
D Yl -
3. Determine theoretical plates and heat loads at various re-flux ratios.
A. For a given reflux ratio, determine and Hi fromthe equations given in 2 B.
B. Determine the operating point (x D , B)
B= (Hi - hw) y
[ +Yl xw
qcC. Find x F
; condenser heat load per pound of furfural
fed to the column.F
B = q -D
+ hD
X]) x F [1 - R]xs
xD - R xF
xF F xF xD xs
qc[ [ B - hp xF - xs
4. Extrapolate the line through (xD , B) and (xF, HF) to get the
operating point (xs , X).
5. Calculate s ; reboiler heat load per pound of furfuralxF F
fed to the column.
n••
Report No. 2070 -10-
q.
sponding xi.
xF F
X = h s -
hs X xF xr)
xF x s - 3cD
6. Determinsection.
e the theoretical number of plates in the rectifying
A. Using the y1 determined in step 3A, find the corre-
[100 - xa = [
100 - y x
B . Calculate yn+ 1 by:
Yn+1 81, 997. 5 + xn [B - 1096.13 ]
- 6. 78 xn + B + 449.1
C. If xn is greater than the x determined in step 1, then
steps A and B must be repeated using the previously calculated yn+1.
7. Determine the theoretical number of plates in the strippingsection.
A. From the relative volatility relationship, get the yass ociated with xs.
B. Calculate xn+1 by:
975 xs - yn (X - 180 + 7.48 xs)
xn+1-6. 78 yn - .7 xs - X + 1155
C. If xn+1 is greater than the x determined in step 1,
steps A and B must be repeated, using the calculated xn+1•
Report No. 2070 -11-
The above computations were programed and carried out on an electroniccomputer for the entire grid of variables listed on page 6. Resultsof these computations are listed in tables 4, 5, and 6, and illustratedin figures 10, 11, and 13.
Dehydrating Column
The 84.1 percent furfural product of the azeotrope column is fed tothe dehydrator, where pure furfural is withdrawn as bottoms and avapor of the azeotrope composition is produced overhead. The cal-culations for this tower can be treated similarly to those for theazeotrope tower by using concentrations in terms of water ratherthan furfural and by reversing the enthalpy lines on the Ponchon-Savarit diagram. The feed may be considered as two parts --a feedresulting from refluxing part of the overhead vapors, and the fur-fural-rich layer from the azeotrope column. With the followingchanges, the dehydrating column can be solved, using the same pro-gram as for the azeotrope column.
(1) The feed to the dehydrating tower contains 15.9 percentof water and is fed at saturation temperature.
(2) This feed falls on a known equilibrium tie line, so theminimum reflux ratio is also known without calculation. This partof the computation can therefore be skipped.
( 3 )
It is not necessary to use the rectifying plate calculation.
(4) Change the constants in the xn+l and enthalpy equations.
(5) Bottoms composition is known to be 99.5 percent furfural.
Table 7 summarizes the results of this computation.
Costs and Design Factors for the Distillation Columns
The design of the distillation unit was based on a production of 15,000, 000pounds of furfural per year. Using the results of the plate and energycalculation, distillation costs were determined from the following re-lations:
-1. F = D [ r) xs
xF xs
Report No. 2070 -12-
2. V1 = D [xn
xw
3. a = V1
G
G = 904 lb. per hr. -ft. 2
where G is the allowable vapor velocity. This was based on using theproperties of water as the properties of the fluid being distilled andassuming a plate spacing of 24 inches.? The area based on the vaporvelocity is sufficient to accomodate the liquid flow if the liquid down-spouts comprise 10 percent of the plate area and if the velocity inthem is at least 4 feet per second.
4. Overall plate efficiency = 43 percent. .Q
5. In C = 0.1187 (ln L) 2 + 4.95769
This relation was determined from the data presented in Newton and
Aries, 2. and was scaled to current costs with the Marshall Stevensindex. The final tower cost was amortized over a 3-year period aftermaintenance costs of 10 percent were included.
6. Steam cost = $1.00 per million B.t.u.'s
The above relations were applied to the engineering results of theprevious sections to obtain the data shown in table 8 and figures 8, 9,12, and 13. Comparison of figures 8 and 9 indicates there is negli-gible variation in the cost of the azeotrope distillation with a changein feed enthalpy. In going from 100 to 225 B.t.u. per pound of feed,
the distillation cost for a feed solution with 2 percent of furfural isdecreased by less than 0.03 cent per pound of furfural produced. Thisrepresents about a 3 percent change in the cost.
?Sanders, M. , and Brown, G. G. Ind. Eng. Chem., 26, 98 (1934).
80' Connell, H. E. Trans. Inst. Chem. Engrs., 42, 741 (1946).
9—Aries, R. S., and Newton, R. D. Chemical Engineering Cost Esti-
mation, p. 70. McGraw-Hill Book Company, Inc., New York(1955).
xw
Report No. 2070 -13-
Figures 8 and 9 also demonstrate that the optimum ratio of actualreflux to minimum reflux is very nearly constant and is in the regionof 1.10 to 1.15. The major portion of the cost for distillation in theazeotrope tower can be attributed to the cost of steam. According tothe values in table 8, the steam cost accounts for approximately 80percent of the total cost and, in general, amounts to less than acent per pound of furfural. From figure 10, the steam requirementrange from 17 to less than 5 pounds per pound of furfural at feed con-centrations of 1 and 6. 45 percent of furfural. This corresponds to anannual steam cost of about $50, 000 to $160, 000, whereas the totalazeotrope tower costs are in the order of $50, 000.
In contrast to the distillation in the azeotrope column, the requirementsfor the recovery of furfural in the dehydrator are exceedingly small.Steam consumption in the dehydrating tower is approximately one-tenth of that for the azeotrope column; while, in addition, the towerdiameter and the number of plates necessary for separation in thedehydrator are smaller by a factor of about seven or eight. Accord-ingly, the economics of the entire distillation operation are predomi-nately influenced by the mode of operation in the azeotrope column.
Report No. 2070 - 14- 1. -55
Table 1.--Extrapolated values of Van-Laar constants at variouspressures based upon experimental data at 5.97, 7.60, and 9.51 atmospheres
Table 4.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(99 percent of furfural in feed recovered overhead)
Line :Furfural: Feed : Reflux :Furfural:Condenser
No. :content :enthalpy: ratio :content : duty!: of HF W/D : of ::feed by : : :overhead:: weight : : • vapor :: xF :
(1) : (2) (3) : (4) (5) (6) : (7)
:Percent • B.t.u. : Lb, per :Percent :B,t.u. per:B.t.u.
Table 4.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric_pressure(99 percent of furfural in feed recovered overhead)--Con.
: . : .Line :Furfural: Feed : Reflux :Furfural:Condenqer : Reboiler : Number of : Number ofNo. :content :enthalpy: ratio :content : duty dutyl :theoretical: theoreticalof : HF W/D : of : qc qs : plates in : plates inr :feed by :
Table 4.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(99 percent of furfural in feed recovered overhead)--Con.
Line :Furfural: FeedNo. :content :enthalpy:
of : HF::feed by :: weight: xF:
Reflux :Furfural:Condenqer : Reboiler : Number of : Number ofratio :content : duty! : duty! :theoretical:theoretical
W/D : of : qc q, : plates in : plates in:overhead: xFF 7,17g. :rectifying : stripping: vapor : : section : section. :
Table 4.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(99 percent of furfural in feed recovered overhead)--Con.
Line :Furfural: Feed : Reflux :Furfural:Condenser : Reboiler : Number of : Number ofNo. :content :enthalpy: ratio :content : duty! duty! :theoretical:theoretical
: of : HF: W/D : of : qc qs : plates in : plates in
:feed by : :overhead: xFF xFF :rectifying : stripping
: weight : : vapor : : section : section: xF :
(1) : (2) : (3) 1 (4) : (5) : (6) : (7) : (8) (9)
:Percent : B.t.u. : Lb. per :Percent :B.t.u. per:B.t.u. per:
Table 4.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(99 percent of furfural in feed recovered overhead)--Con.
Line :Furfural: Feed : Reflux :Furfural:Condenser : Reboiler : Number of : Number of
No. :content :enthalpy: ratio :content : duty 1- duty! :theoretical:theoretical
of HFW/0 : of : cis : plates in : plates inqc
:feed by : :overhead: xFF ;;T, :rectifying : stripping
Table 4.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(99 percent of furfural in feed recovered overhead)--Con.
LineNo.
:Furfural: Feed ::content :enthalpy:
of : HF::feed by :: weight
xF
: (2)
Reflux :Furfural:Condenser : Reboiler : Number of : Number ofratio :content : dutyil dutyl :theoretical:theoretical
WAD : of : q c : plates in : plates incis:overhead: xFF xFF :rectifying : stripping
vapor : •. : section : section•
(1) : (3) : (4) : (5) : (6) : (7) : (8) (9)
:Percent : B.t.u. : Lb. per :Percent :B.t.u. per:B.t.u. per::
Table 5.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(97 percent of furfural in feed recovered overhead)
Table 5.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(97 percent of furfural in feed recovered overhead)--Con.
:Furfural:Condenser : Reboiler : Number of : Number of:content : duty! duty! :theoretical:theoretical
of : q c qs : plates in : plates in_:overhead: :rectifying : strippingxFF x FF
: vapor : : section : section
(4) : (5) . (6) : (7) : (8) (9)
:Percent : B.t.u. Lb. per :Percent :B.t.u. per:B.t.u. per:
Table 5.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(97 percent of furfural in feed recovered overhead)--Con.
r-
Line :Furfural: Feed : RefluxNo. :content :enthalpy: ratio
: of : HF : W/D:feed by :: weight :
xF : •
:Furfural:Condenser : Reboiler:content : dutyl : dutyl: of : q c : qs:overhead: --- :xFF xFF: vapor :
•
: Number of : Number of:theoretical:theoretical: plates in : plates in:rectifying : stripping: section : section
Table 5.--Plate and energy requirements for producinll a furfural-waterazeotropc in a tower operating at atmospheric pressure(97 percent of furfural in feed recovered overhead)--Con.
Line :Furfural: Feed : Reflux :Furfural:Condenser : Reboiler : Number of : Number ofNo. :content :enthalpy: ratio :content : dutyl : dutyl :theoretical:theoretical
of : HF: W/D : of : q c•. qs : plates in : plates in
:feed by : :overhead: --; •. xFF :rectifying : stripping
Table 5.--Plate and ener re uirements for •roducin? a furfural-waterazeotrope in a tower operating at atmospheric pressure(97 percent of furfural in feed recovered overhead)--Con.
Line :Furfural: Feed : Reflux :Furfural:Condenser : Reboiler : Number of : Number of
No. :content :enthalpy: ratio :content : dutyl : dutyl :theoretical:theoreticalof : Hp. : W/D : of : qc: qs : plates in : plates in
:feed by : . :overhead: : ;;"E". :rectifying : stripping
Table 6.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(95 percent of furfural in feed recovered overhead)
Line :Furfural: FeedNo. :content :enthalpy:
of :HF:feed by :weight :
xF :
(1) : (2) : (3) :
Ref lux :Furfural:Condeaser : Reboiler
'ratio :content : duty! duty!
W/D : of
qc
qs:overhead:
xFP XFF
: vapor :
(4) : (5) : (6) •
: Number of : Number of:theoretical:theoretical: plates in : plates in:rectifying : stripping: section : section
(9)(7) : (8)
Report No. 2070
Line :Furfural: Feed : ReflNo. :content :enthalpy: rat
: of :HF : W/:feed by :: weight :: xp. :
(1) : (2) : (3) :
:Percent : B.t.u. ::per lb.
ux :Furfural:Condenser : Reboiler : Number of : Number of
io :content : dutyl : dutyl :theoretical:theoreticalD : of : qc : qs : plates in : plates in
Table 6.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(95 percent of furfural in feed recovered overhead)--Con.
Table 6.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(95 percent of furfural in feed recovered overhead)--Con.
: .Line :Furfural: Feed : Reflux :Furfural:Condenser : Reboiler : Number of : Number ofNo. :content :enthalpy: ratio :content : duty 1- dutyl :theoretical:theoretical
of HF : W/D : of : q c qs : plates in : plates in
:feed by : :overhead: xFF xFF :rectifying : stripping
Table 6.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure (95 percent of furfural in feed recovered overhead)--Con.
Table 6.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure (95 percent of furfural in feed recovered overhead)--Con.
Line :Furfural: Feed : Reflux :Furfural:Condenser : Reboiler : Number of : Number ofNo. :content :enthalpy: ratio :content : duty 1- dutyl :theoretical:theoretical
Table 6.--Plate and energy requirements for producing a furfural-waterazeotrope in a tower operating at atmospheric pressure(95 percent of furfural in feed recovered overhead)--Con.
Line :Furfural: Feed : Reflux :Furfural:Condenser : Reboiler : Number of : Number ofNo. :content :enthalpy: ratio :content : dutyl : dutyl :theoretical:theoretical
of : HF: W/D : of : qc : qs : plates in : plates in:feed by : . :overhead: 717, :
1-Mel l nikov, N. P. and Tsirlin, Yu. A. Zur Prikiad Khim29.2 (9) 1456 (1956).
Report No. 2070
SUBJECT LISTS OF PUBLICATIONS ISSUED BY TEE
FOREST PRODUCTS LABORATORY
The following are obtainable free on requestLaboratory, Madison 5, Wisconsin:
from the Director, Forest Products
List of publications onBox and Crate Constructionand Packaging Data
List of publications onChemistry of Wood andDerived Products
List of publications onFungus Defects in ForestProducts and Decay in Trees
List of publications onGlue, Glued Productsand Veneer
List of publications onGrowth, Structure, andIdentification of Wood
List of publications onMechanical Properties andStructural Uses of Woodand Wood Products
Partial list of publicationsfor Architects, Builders,Engineers, and RetailLumbermen
List of publications onFire Protection
List of publications onLogging, Milling, andUtilization of TimberProducts
List of publications onPulp and Paper
List of publications onSeasoning of Wood
List of publications onStructural Sandwich, Plasticlaminates, and Wood-BaseAircraft Components
List of publications onWood Finishing
List of publications onWood Preservation
Partial list of publicationsfor Furniture Manufacturers,Woodworkers and Teachers ofWoodshop Practice
Note: Since Forest Products Laboratory publications are so varied in subjectno single list is issued. Instead a list is made up for each Laboratorydivision. Twice a year, December 31 and June 30, a list is made upshowing new reports for the previous six months. This is the only itemsent regularly to the Laboratory's mailing list. Anyone who has askedfor and received the proper subject lists and who has had his name placedon the mailing list can keep up to date on Forest Products Laboratorypublications. Each subject list carries descriptions of all other sub-ject lists.