631
23
Hydrogen Production
23.1 INTRODUCTION
Throughout the previous chapters, there have been several references and/or acknowledgments of a
very import property of petroleum and petroleum products. And that is the hydrogen content or the
use of hydrogen during refining in hydrotreating processes, such as desulfurization (Chapter 21) and
in hydroconversion processes, such as hydrocracking (Chapter 22). Although the hydrogen recycle
gas may contain up to 40% by volume of other gases (usually hydrocarbons), hydrotreater catalyst
life is a strong function of hydrogen partial pressure. Optimum hydrogen purity at the reactor inlet
extends catalyst life by maintaining desulfurization kinetics at lower operating temperatures and
reducing carbon laydown. Typical purity increases resulting from hydrogen purification equipment
and/or increased hydrogen sulfide removal as well as tuning hydrogen circulation and purge rates
may extend catalyst life up to about 25%.
A critical issue facing the world’s refiners today is the changing landscape in processing petroleum crude into refined transportation fuels under an environment of increasingly more stringent
clean fuel regulations, decreasing heavy fuel oil demand and increasingly heavy, more sour crude
supply. Hydrogen network optimization is at the forefront of world refineries options to address
clean fuel trends, to meet growing transportation fuel demands, and to continue to make a profit
from their crudes. A key element of a hydrogen network analysis in a refinery involves the capture
of hydrogen in its fuel streams and extending its flexibility and processing options. Thus, innovative
hydrogen network optimization will be a critical factor influencing refiner’s future operating flexibility and profitability in a shifting world of crude feedstock supplies and ultra-low-sulfur (ULS)
gasoline and diesel fuel.
As hydrogen use has become more widespread in refineries, hydrogen production has moved
from the status of a high-tech specialty operation to an integral feature of most refineries (Raissi,
2001; Vauk et al., 2008). This has been made necessary by the increase in hydrotreating and hydrocracking, including the treatment of progressively heavier feedstocks (Chapter 23). In fact, the use
of hydrogen in thermal processes is perhaps the single most significant advance in refining technology during the twentieth century (Scherzer and Gruia, 1996; Bridge, 1997; Dolbear, 1998). The
continued increase in hydrogen demand over the last several decades is a result of the conversion of
petroleum to match changes in product slate and the supply of heavy, high-sulfur oil, and in order
to make lower boiling, cleaner, and more salable products. There are also many reasons other than
product quality for using hydrogen in processes adding to the need to add hydrogen at relevant
stages of the refining process and, most important according to the availability of hydrogen (Bezler,
2003; Miller and Penner, 2003; Ranke and Schödel, 2003).
With the increasing need for clean fuels, the production of hydrogen for refining purposes
requires a major effort by refiners. In fact, the trend to increase the number of hydrogenation (hydrocracking and/or hydrotreating) processes in refineries coupled with the need to process the heavier
oils, which require substantial quantities of hydrogen for upgrading because of the increased use
of hydrogen in hydrocracking processes, has resulted in vastly increased demands for this gas. The
hydrogen demands can be estimated to a very rough approximation using API gravity and the extent
of the reaction, particularly the hydrodesulfurization reaction (Speight, 2000; Speight and Ozum,
2002). But accurate estimation requires equivalent process parameters and a thorough understanding of the nature of ach process. Thus, as hydrogen production grows, a better understanding of the
23
Hydrogen Production
23.1 INTRODUCTION
Throughout the previous chapters, there have been several references and/or acknowledgments of a
very import property of petroleum and petroleum products. And that is the hydrogen content or the
use of hydrogen during refining in hydrotreating processes, such as desulfurization (Chapter 21) and
in hydroconversion processes, such as hydrocracking (Chapter 22). Although the hydrogen recycle
gas may contain up to 40% by volume of other gases (usually hydrocarbons), hydrotreater catalyst
life is a strong function of hydrogen partial pressure. Optimum hydrogen purity at the reactor inlet
extends catalyst life by maintaining desulfurization kinetics at lower operating temperatures and
reducing carbon laydown. Typical purity increases resulting from hydrogen purification equipment
and/or increased hydrogen sulfide removal as well as tuning hydrogen circulation and purge rates
may extend catalyst life up to about 25%.
A critical issue facing the world’s refiners today is the changing landscape in processing petroleum crude into refined transportation fuels under an environment of increasingly more stringent
clean fuel regulations, decreasing heavy fuel oil demand and increasingly heavy, more sour crude
supply. Hydrogen network optimization is at the forefront of world refineries options to address
clean fuel trends, to meet growing transportation fuel demands, and to continue to make a profit
from their crudes. A key element of a hydrogen network analysis in a refinery involves the capture
of hydrogen in its fuel streams and extending its flexibility and processing options. Thus, innovative
hydrogen network optimization will be a critical factor influencing refiner’s future operating flexibility and profitability in a shifting world of crude feedstock supplies and ultra-low-sulfur (ULS)
gasoline and diesel fuel.
As hydrogen use has become more widespread in refineries, hydrogen production has moved
from the status of a high-tech specialty operation to an integral feature of most refineries (Raissi,
2001; Vauk et al., 2008). This has been made necessary by the increase in hydrotreating and hydrocracking, including the treatment of progressively heavier feedstocks (Chapter 23). In fact, the use
of hydrogen in thermal processes is perhaps the single most significant advance in refining technology during the twentieth century (Scherzer and Gruia, 1996; Bridge, 1997; Dolbear, 1998). The
continued increase in hydrogen demand over the last several decades is a result of the conversion of
petroleum to match changes in product slate and the supply of heavy, high-sulfur oil, and in order
to make lower boiling, cleaner, and more salable products. There are also many reasons other than
product quality for using hydrogen in processes adding to the need to add hydrogen at relevant
stages of the refining process and, most important according to the availability of hydrogen (Bezler,
2003; Miller and Penner, 2003; Ranke and Schödel, 2003).
With the increasing need for clean fuels, the production of hydrogen for refining purposes
requires a major effort by refiners. In fact, the trend to increase the number of hydrogenation (hydrocracking and/or hydrotreating) processes in refineries coupled with the need to process the heavier
oils, which require substantial quantities of hydrogen for upgrading because of the increased use
of hydrogen in hydrocracking processes, has resulted in vastly increased demands for this gas. The
hydrogen demands can be estimated to a very rough approximation using API gravity and the extent
of the reaction, particularly the hydrodesulfurization reaction (Speight, 2000; Speight and Ozum,
2002). But accurate estimation requires equivalent process parameters and a thorough understanding of the nature of ach process. Thus, as hydrogen production grows, a better understanding of the