I
L. S. STANTONl, E.
8. REID, and H. F. MASON
California Research Corp., Richmond, Calif.
Computer Use in Pilot Plant Calculations Computer program processes routine data from pilot plant with a great saving in time. The need for careful editing and reviewing of raw information is always a problem. This program takes a step in the direction of doing some of this automatically
program used to analyze the results from a petroleum processing pilot plant was designed to exercise discretion in handling raw data-i e., reject bad data points on statistical grounds and compensate for occasional missed readings, as well as produce the desired summary of information regarding the run. Editing data as part of a manual calculation is no particular problem because it falls in naturally with processing the data. However, scrutinizing tables for omissions and obvious errors, as is usually done, may be more time-consuming than the machine computation itself. In routine processing of plant information, it is desirable to make the editing part of the computing progiam so that raw data from run sheets may be read directly into the computer. The program was written for the Datatron computer, which the California Research Corp. installed a t its Rich-
A C o x w m R
1 Present address, United States Borax and Chemical Corp., Boron, Calif.
mond Laboratory for use in scientific and engineering work. This computer has card input, card output, on-line printer, and Flexowriter output. Process The pilot plant chosen for illustration is a catalyst testing unit with various process uses. Oil and hydrogen are passed through the catalytic reactor and the product is taken to a liquid gas separator. The gases are led to a gas recovery system or to the vent. The liquid phase is collected and analyzed. Two important results derived from a run are the catalyst activity and the decline of activity with catalyst onstream time. As the change in API gravity in going through the unit proved to be a good criterion of the activity for the catalyst under study, the results can be conveniently analyzed. The log of API gravity changes linearly with the log of the catalyst on-stream time. Consequently, the change in OAPI at a specified time, 7' (8 hours), is taken as the catalyst activity and the slope of
Table I.
Input Data
Run number API gravity 4nd aniline point of liquid product for each 2-hour sample Volume of stock fed during each 2-hour interval Weight and specific gravity of oil used to displace hydrogen Hydrogen system pressure Reactor pressure API gravity of feed Clock time and date, start and end of run Catalyst description and history (coded)
the line as the catalyst decline. T o put different runs on a comparable basis, the gravity of the product is corrected to Btandard reference values of space rate and gas rate. Program The input information available to the computer is shown in Table I. The manner in which the program carries out its analysis can best be described by following the schematic flow diagram. The following steps are involved.
HYDROGE N FEED
REACTOR
-
TO GAS RECOVERY
ACT I V I T Y
-----T LOG TIME Catalyst activity decreases with time at constant 'APl gravity feed
Pilot plant catalyst testing unit has various process uses VOL. 50, NO. 5
MAY 1958
719
DATA R E A D I N
5. The API gravities of the liquid products are corrected to standard values of space rate and gas rate. Empirical correlations have been built up which allow these adjustments to be made so that results from different runs are directly comparable. 6. The API gravity observations are correlated by least squares methods with the equation
1 I F MISSING, TYPE OUT
M I S S I N G DATA SEARC?t
I
CALC. OF ELAPSED TIMES
I
Log ‘API = a
I
C A L C . OF O I L F E E D R A T E , SPACE R A T E , G A S R A T E
+ b log T
where T is the on-stream time in hours. T o do this, the program converts “API and T to their logarithms, determines the number of points, and makes the fit. The equation is also solved for the API gravity at the observed on-stream times and the deviations are computed. 7 . The Q test is applied to the deviations of the observed API gravities from the curve as a criterion for the rejection of inconsistent data points. This involves ordering the deviations by size and making tests on the extremes. If a point is shown to be out of line, the program rejects it and goes through the equation-fitting program again. Normally, six points are involved in the fitting; however, if, through missing data or rejected data, less than four points are available for final fitting, the run is rejected. 8. The activity of the catalyst is found by solving the equation at 8 hours’ on-stream time to find the API gravity and subtracting from this the feed gravity. 9. Output data are assembled and printed out.
I C O R R E C T I O N O F S A M P L E ‘APl T O STAND. C O N D . O F SPACE R A T E AND G A S R A T E
C A L C . OF L O G “ A P I A N D L O G T D E T N . OF N O . OF P O I N T S L E A S T SQ. F I T OF E Q U A T I O N C A L G . ‘APl FOR O B S . T
1 1
Q T E S T A P P L I E D FOR R E J E C T I O N OF DATA P O I N T S I
IF P O I N T REJECTED
I
‘I ICOMP. OF 8 - H O U R ACTIVITY
I
FEMBLE OUTPUT DATA A N D PUNCH I ~~
Program schematic flow chart
1. The run data are read in for computation. The data for this are punched into cards directly from the plant run sheet. The sheet is set up in such a way that no transcription of data is required and no further instructions need be given for keypunching. 2. The program tests the data for completeness. If flow rate data or clock time a t start or end of run are missing, the calculation cannot be made. The identification of the missing data is
Table II.
Run No. Unit No. Cat. No. Cat. history Composition Activity Decline Aniline point SCF/B Sum deviations API gravity 2 4 hr. 4-6 hr. 6-8 hr. 8-10 hr. 10-12 hr. 12-14 hr. No. of points
720
typed out on the Flexowriter, the run is rejected, and a new run is read in. If the missing data are from among the product inspections, the program will make note of these and move on. 3. The calendar dates and clock times are used to compute hours of elapsed time. 4. From the elapsed times and feed readings, the hydrocarbon feed rate, hydrogen gas feed rate, and space velocity are computed.
Output of Program 170596 2
1
453000 100115
548013 700372
21.2 0.03799.8 6140 6
3 308002 505015
24.5 0.037100.5 6280 29
20.9 0.02699.7 6200
7
Calcd.
Obsd.
Calcd.
Obsd.
Calcd.
Obsd.
48.2 47.3 46.8 46.3 46.0 45.7
48.1 47.5 46.8 46.4 46.0 45.5
51.6 50.7 50.0
52.4 50.0 49.3 55.8 49.4 49.4
47.3 46.7 46.3 46.0
47.2 46.8 46.6 45.8
45.6
45.5
6
INDUSTRIAL AND ENGINEERING CHEMISTRY
49.2 48.9 5
5
The output of the program is shown in Table 11. Most of it is self-explanatory. The tenth item, “Sum deviations,” is merely the sum of the absolute deviations of the observed values of API gravity from the curve to give a quick indication of the consistency of the data. The “No. of points” is the number of observations used in the final fitting of the equation. In unit 2, a rejected point is shown. The blank “Calcd. API” a t 8 to 10 hours indicates the 55.8 point was not used. The blank a t 10 to 12 hours, unit 3, indicates the datum was missing. Table I1 shows the results from three different units. Actually, six identical pilot units are operated simultaneously, and all calculations are carried out in parallel. A part of the data is common to all six units. Running of the program requires approximately 2 minutes compared t o manual calculation, which requires 3 to 4 hours. RECEIVED for review November 18, 1957 ACCEPTEDFebruary 14, 1958 Division of Petroleum Chemistry, Symposium on Application of Machine Computation in Petroleum Research, 132nd Meeting, ACS, New York, N. Y . , September 1957.
