8.50

Physical Properties Analyzers—ASTM Methods N. S. WANER (1972) I. VERHAPPEN

A. ALSTON

(1982)

D. E. PODKULSKI

(1995)

TO RECEIVER

AT

FLASH POINT OR BOILING POINT, ETC.

Flow Sheet Symbol

(2003)

Analyzer Type:

A. Distillation analyzer B. Vacuum distillation analyzer C. Horizontal still distillation analyzer D. Simulated distillation by gas chromatography E. Air-saturated vapor pressure analyzer—continuous F. Air-saturated vapor pressure analyzer—cyclic G. Dynamic vapor pressure analyzer H. Continuous vapor—liquid ratio analyzer I. Differential-pressure pour pointer J. Viscous-drag pour pointer K. Optical-cloud point analyzer L. Freeze-point analyzer M. Low-temperature flash-pointer analyzer N. High-temperature flash-point analyzer O. Octane engine comparator analyzer P. Reactor-tube continuous octane analyzer Q. Near-infrared inferential measurements

Potential Applications:

Crude fractions (A, B, C, D, I, J, K, L, M); gasoline components/product (A, B, C, D, E, F, G, H, O, P); diesel (K, M); jet or kerosene (L, M); lube oils (I, J, N)

Reference Methods:

ASTM D86 (A, C); ASTM D1160; (B); ASTM D2887/D3710 (D); ASTM D4953–90 (E, F, G); ASTM D1267 (G); ASTM D2533 (H); ASTM D97 (I, J); ASTM D2500 (K); ASTM D2386 (L); ASTM D56/D93 (M, N); ASTM D2699/D2700 (O, P)

Costs:

A. $40,000 B. $56,000 C. $31,000 D. $40,000 E. $38,000 F. $28,000 G. $26,000 to $35,000 H. $85,000 I. $37,000 J. $41,000 K. $28,000 L. $33,000 M. $44,000 N. $41,000 O. $220,000 P. $86,000 Q. $100,000

Partial List of Suppliers:

ABB Process Analytics (D, F) (www.abb.com) Benke (A, B, E, J, K, L, M, Q) (www.benke.de)

1589 © 2003 by Béla Lipták

1590

Analytical Instrumentation

Core Labs/Waukesha (H,O) (www.dresser.com) Ocean Optics (UOP) (P) (www.oceanoptics.com) Precision Scientific (A, B, C, E, G, I, K, L, M, N) (www.precisionsci.com) Rotork Ltd. (C, D, G, J) (www.rotork.com) Siemens Applied Automation (D) (www.sea.siemens.com.ia/)

INTRODUCTION This section deals with on-stream analyzers, which measure a physical property of a process stream. More specifically, onstream analyzers are related to ASTM Standard Test Methods for refinery processes and products. Table 8.50a provides an overall orientation of the various physical property analyzers that are available. Prior to the introduction of on-stream analyzers, analyses were done in the laboratory on periodic grab samples, and the results were reported to the process unit operator at some later time, permitting set point adjustments of parameters such as flow, temperature, pressure, and level. Continuous on-stream plant analyzers offer many advantages over laboratory analyses, including the characteristics enumerated below.

is the currently accepted laboratory standard for determining the boiling characteristics of petroleum products distilled at atmospheric pressure. The method employs a batch technique and approaches a single plate distillation process without reflux. The petroleum products analyzed are complex mixtures of components, and a low level of fractionation is achieved. True boiling-point distillation, in columns with 15 to 100 theoretical plates and at reflux rations of 5:1 or more, produce greater separation of components. The apparatus and procedures for true boiling-point determination are not standard, are complex, take longer to perform, and are not as widely used. Distillation curves for a few hydrocarbons are shown in Figure 8.50b along with a comparison of curves generated by ASTM Method D86-IP-123 and by true boiling-point determinations for kerosene.

Advantages of Continuous Analyzers 1. Continuous measurement of the stream, eliminating long time lags 2. Reduction of errors caused by unrepresentative samples or by changes in sample composition caused by sample handling 3. Elimination of human errors characteristic of nonautomated laboratory procedures 4. Ability to recognize process trends, thus permitting the automatic control of a given process variable by closed-loop control 5. Cost reductions resulting from minimization of laboratory analyses 6. Closer control resulting in smaller tolerances in final product specifications and reduction in quality “giveaway” 7. Feasibility of implementing in-line blending systems, which result in economic benefits resulting from the elimination of tankage, and from increased system flexibility and better quality control 8. Ability to provide continuous inputs to computerized process control systems for plant optimization 9. Direct measurement of process variables rather than detection of properties by inference DISTILLATION ANALYZERS Laboratory Measurements Distillation analyzers were introduced to provide data on the volatility characteristics of process streams and separation efficiency of distillation units. ASTM Method D 86-IP-123

© 2003 by Béla Lipták

ASTM Method D 86-IP-123 A sample is heated in an Engler flask at a prescribed rate. Packing is not used, and some refluxing occurs as a result of condensation (Figure 8.50c). The vapors that are produced flow through a condenser immersed in an ice-water bath, and the distillate is collected in a graduated cylinder. The initial boiling-point temperature is defined as the reading of the thermometer at the instant the first drop of condensate falls from the lip of the condenser tube. As the higher boiling fractions vaporize, condense, and collect in the graduate, corresponding temperature readings are recorded to permit the plot of a curve of temperature vs. percent of sample recovered. The end point or final boiling point is described as the maximum thermometer reading observed during the test; it usually occurs when all the liquid has been boiled off from the bottom of the flask. Usually, the percentage recovered does not equal the 100ml sample charge, partly because of the inability of the apparatus to condense the lightest fractions. A curve of temperature vs. percent evaporation is determined by adding the percent of light ends lost to each of the recorded percentages recovered. The precision of this method is a function of the temperature change vs. boiling rate. Repeatability ranges from ±2 to 9°F (±1 to 5°C), and the reproducibility ranges from ±5 to 20°F (±3 to 11°C). ASTM Method D 1160 This method provides for measurements under vacuums, ranging from 1 mmHg (133 Pa) absolute to atmospheric, to a maximum liquid temperature of 750°F (399°C). Results are not comparable with other ASTM distillation tests, although they may be converted to corresponding vapor temperature at 760 mmHg by reference to Maxwell and Bonnel vapor pressure charts.

TABLE 8.50a Orientation Table for Physical Properties Analyzers Repeatability (+/−)

Flow Rate GPH (LPH)

Pressure PSIG (kPa)

Cycle Time (minutes)

Cost (in $1000s)

30°F (17°C) below IBP

5

40

Precision Scientific

50–250 345–1724

180°F (82°C) max

16

56

Precision Scientific

0.4 (1.5)

5–100 (35–700)

40°F (22°C) lower than IBP

2

31

Rotork

3–12°F (2–7°C)

4(15) (sample inject)

5–150 (35–1035)

Below expected IBP

10–30

40

Asea Brown Boveri Applied Automation Rotork

0.1 psia

1.6 (6)

10–100 (69–690)

50–110°F (10–43°C)

2

38

Precision Scientific

0.75

Analyzer

Type

Range

Distillation

Distillation

5–95% 100–650°F (38–343°C)

1% sample boiling range

1.2 (4.5)

20–150 (138–1035)

Vacuum

650–1000°F (343–538°C)

1% sample boiling range

2.3 (8.7)

Horizontal Still

5–95% 150–650°F (65–343°C)

Equal or better than ASTM

Simulated Distillation

2–98% 0–1000°F (–17–538°C)

Air-saturated Continuous

2–19 psia

Vapor Pressure

Temperature F (C)

9

0–20 psia

0.05 psia

Bypass flow

Dynamic

0–20 psia 0–200 psia

Equal to or better than ASTM

10–50 (38–190)

75–500 (520–3450)

70–120°F (21–49°C)

Vapor/Liquid

Continuous

10–30 V/L to 150°F (66°C)

0.5 V/L

2–4 (7.6–15.1)

50–150 (350–1050)

Normal Blending Range

Pour Point

Differential Pressure

–75−+50°F (–59−+10°C)

5°F (2°C)

2 (7.6)