Fundamentals of Natural Gas Processing, Third Edition

Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9780429877148
• Edition: 3
• Topic: Tecnología e ingeniería
• Subtopic: Combustibles fósiles

Offering indispensable insight from experts in the field, Fundamentals of Natural Gas Processing, Third Edition provides an introduction to the gas industry and the processes required to convert wellhead gas into valuable natural gas and hydrocarbon liquids products including LNG. The authors compile information from the literature, meeting proceedings, short courses, and their own work experiences to give an accurate picture of where gas processing technology stands today as well as to highlight relatively new technologies that could become important in the future.

The third edition of this bestselling text features updates on North American gas processing and changing gas treating requirements due to shale gas production. It covers the international nature of natural gas trade, LNG, economics, and more. To help nonengineers understand technical issues, the first 5 chapters present an overview of the basic engineering concepts applicable throughout the gas, oil, and chemical industries. The following 15 chapters address natural gas processing, with a focus on gas plant processes and technologies. The book contains 2 appendices. The first contains an updated glossary of gas processing terminology. The second is available only online and contains useful conversion factors and physical properties data.

Aimed at students as well as natural gas processing professionals, this edition includes both discussion questions and exercises designed to reinforce important concepts, making this book suitable as a textbook in upper-level or graduate engineering courses.

Part 1

1

Processing Principles

1.1 Introduction

This chapter introduces the reader to the fundamentals needed to better understand the following chapters. It is intended for those new to gas processing and those having limited chemistry background. It contains three major sections:

1. Process terminology and units
2. Basic concepts of chemistry
3. Thermodynamics

The last two topics are major fields of science. This chapter provides only a brief introduction to the subjects to give readers without a chemical engineering education sufficient background to comprehend more technical sections in later chapters.

1.2 Units and Conversions

There are two general systems of units in use today, the International System of Units (SI) and the U.S. Engineering System (USES) and their variants. The USES is in general use in the United States, but all other industrialized countries use a system based on SI.¹ This section discusses the commonly used units and gives some conversions between USES and SI.

The book uses dual units in the text, examples, and graphs whenever possible (USES first followed by SI in parentheses) but there are cases where it will be necessary to make individual conversions. Appendix B.1² provides a set of unit conversions that should be adequate for most situations. For example, the SI unit of pressure is the pascal (commonly kPa or MPa), but both bar and kg/cm² are frequently used.

The section below gives basic units. This is followed by commonly used combinations of units. Before discussing units, the definition of commonly used prefixes is needed. Frequently, quantities in gas processing involve large values. To make large numbers more manageable in the USES, the following prefixes are used:

M = thousand	= 1,000	= 10^3
MM = million	= 1,000,000	= 10^6
B = billion	= 1,000,000,000	= 10^9
T = trillion	= 1,000,000,000,000	= 10^12
Quad	= 1,000,000,000,000,000	= 10^15

Note that these prefixes do not follow SI conventions. The letter M usually represents 10⁶ (which follows SI convention) outside the United States. To avoid confusion, 10³ and 10⁶ are sometimes used.

In this book, M represents 10³ when using USES-based units. The book also follows the U.S. convention for the comma as shown in the numbers above, not a fractional number or space as is often used elsewhere. The Quad represents an extremely large number and is used only when discussing energy terms on a national or world scale.

¹ NIST (2017) provides a complete discussion on SI and Klinkenberg (1969) gives an excellent summary of the Engineering System.

² See Appendix B on publisher website: www.crcpress.com/Fundamentals-of-Natural-Gas-Processing-Third-Edition/Kidnay-Parrish-McCartney/p/book/9781138612792

The prefixes for SI are not followed throughout all countries using SI when applied to volumes. To avoid potential confusion, large values for volumes will use the exponential format. For example, 3,000,000 m³ will be presented as 3 × 10⁶ m³. Prefixes for all other units in SI will follow the SI convention.

Conversion between USES and SI units rarely provides exact results, e.g., 80.00°F = 26.67°C. The precision of a given value dictates the number of significant figures given in the conversion. If converting 80°F and 80.0°F, the conversions will be 27°C and 26.7°C, respectively.

1.2.1 Basic Units

Table 1.1 lists five important basic units used in gas processing. The conversion from one unit system to the other is included. Of the five basic units only time is common to both sets of units.

The USES uses the pound-force (lb_f) as a base unit and it is defined as the force a standard gravitational field exerts on a mass of one pound (lb_m). However, using Newton’s second law (force = mass × acceleration) a lb-force should be equal to (1 lb_m) × (32.174 ft/s²) where 32.174 ft/s² is the standard acceleration of gravity (denoted as g). To maintain numerical and dimensional consistency it is necessary to define the term g_c = 32.174 ft-lb_m/s²-lb_f. Thus, when using USES, Newton’s second law becomes force = mass × g/g_c. As a result, whenever there is a mass–force conversion in USES units g_c must be used to obtain numerically and dimensionally correct values.

The two temperature scales, kelvin (K) and Rankine (°R) are absolute, that is, the zero point is absolute zero. These are awkward to use at ambient temperatures and above so the two relative scales, Fahrenheit (°F) and Celsius (°C) are used. The relationship between the four temperature scales is given below:

t(°F)=T(°R)−459.67t(°C)=T(K)−273.15T(K)=T(°R)/1.80t(°F)=1.80t(°C)+32

Note that by convention the degree symbol is not used with the unit symbol K, and kelvin is not capitalized. It is also common convention to use T to refer to a temperature on an absolute scale and t to refer to a temperature on a relative scale.

1.2.2 Derived Units

Table 1.2 lists other important derived units commonly used in gas processing. These are convenient combinations of the basic units. The table gives the accepted derived name. Other important combinations of units are mentioned in Section 1.2.3.

TABLE 1.1
Five Basic Units Important in Gas Processing

TABLE 1.2
Important Derived Units in Gas Processing

Both area and volume are simple multiples of length. The others are derived from physical laws and definitions as discussed below.

1.2.2.1 Force

Force is defined as mass times acceleration. This is correctly done in the SI system (1 N = 1 kg m/s²).

1.2.2.2 Pressure

This is one of the most common and important of the numerous derived uni...