Chemical Process Industries Chemical Engineering

Regarding Chemical Process Industries in the engineering subject of Chemical Engineering

1. CH3303 : CHEMICAL PROCESS INDUSTRIES OBJECTIVE: To impart knowledge on various aspects of production engineering and make the student understand the practical methods of production in a chemical factory. Om Sakthi

2. UNIT V: FUEL AND INDUSTRIAL GASES Fuel Gases –Natural gas, Liquefied natural gas, Synthesis Gas Industrial gases – Carbon dioxide, hydrogen, nitrogen and oxygen – Argon

3. Fuel Gases Fuel gas is one of a number of fuels that under ordinary conditions are gaseous. Most fuel gases are composed of hydrocarbons (such as methane and propane), hydrogen, carbon monoxide, or mixtures thereof. Such gases are sources of energy that can be readily transmitted and distributed through pipes.

4. Fuel Gases (contd.) Fuel gas is contrasted with liquid fuels and solid fuels, although some fuel gases are liquefied for storage or transport. For example, liquefied petroleum gas (LPG), liquefied petroleum gas (LNG).

5. Fuel Gases (contd.) While their gaseous nature has advantages, avoiding the difficulty of transporting solid fuel and the dangers of spillage inherent in liquid fuels, it also has limitations. It is possible for a fuel gas to be undetected and cause a gas explosion. For this reason, odorizers are added to most fuel gases. The most common type of fuel gas in current use is natural gas.

6. Natural Gas C hinese piped natural gas in bamboo tubes and used it for lighting in about 900 A.D.

7. Natural Gas Natural gas (also called fossil gas, methane gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon dioxide, nitrogen, hydrogen sulfide , and helium are also usually present.

8. Natural Gas (contd.) Natural Gas / Methane Gas is colourless and odourless , and the second largest greenhouse gas contributor to global climate change after carbon dioxide. Because natural gas is odourless, odorizers such as mercaptan (which smells like sulfur or rotten eggs) are commonly added to it for safety so that leaks can be readily detected.

9. Natural gas is a fossil fuel and non-renewable resource that is formed when layers of organic matter (primarily marine microorganisms ) decompose under anaerobic conditions and are subjected to intense heat and pressure underground over millions of years . The energy that the decayed organisms originally obtained from the sun via photosynthesis is stored as chemical energy within the molecules of methane and other hydrocarbons.

10. Uses of Natural gas Natural gas can be burned for heating, cooking, and electricity generation. It is also used as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals and less commonly used as a fuel for vehicles.

11. Natural Gas Drilling Rig & Processing Plant

12. Natural Gas Processing The natural gas processing is done for purification of the raw natural gas to obtain a pipeline quality gas. In general, natural gas processing includes the following steps: Condensate and Water Removal Acid Gas Removal Dehydration – moisture removal Mercury Removal Nitrogen Rejection NGL Recovery, Separation, Fractionation, and Treatment of Natural Gas Liquids

13. A generalized natural gas processing flow diagram

14. A generalized natural gas flow diagram is shown in Figure . After initial scrubbing to remove particles , the first step in natural gas processing is the removal of condensate (oil) and water that is achieved by controlling the temperature and pressure of the inlet stream from the well, as shown in Figure. Natural Gas Processing (contd.)

15. Gas separated in this unit is sent to acid gas recovery; the condensate or the oil recovered is usually sent to a refinery for processing , while water is disposed, or treated as wastewater. Natural Gas Processing (contd.)

16. Acid gases (H2S and CO2) are separated usually by absorption in an amine solution. The recovered H2S is sent to a Tail Gas Treating unit to be converted to elemental sulfur . After removing the acid gases, the natural gas stream is sent to a dehydration unit to remove water typically by absorption in a glycol unit,

17. This is followed by mercury removal (by adsorption on activated carbons or other sorbents), and nitrogen rejection either cryogenically, or by adsorption, or absorption depending on the nitrogen concentration. The last step in the processing sequence is the Natural Gas Liquids (NGL) extraction , fractionation, and treatment, as described in the flowchart .

18. Limitations The extraction and consumption of natural gas is a major and growing contributor to climate change. Both the gas itself (specifically methane) and carbon dioxide, which is released when natural gas is burned, are greenhouse gases . When burned for heat or electricity, natural gas emits fewer toxic air pollutants , less carbon dioxide, and almost no particulate matter compared to other fossil and biomass fuels. However , gas venting and unintended fugitive emissions throughout the supply chain can result in natural gas having a similar carbon footprint to other fossil fuels overall.

19. liquefied natural gas (LNG) Liquefied natural gas (LNG) is the liquid form of natural gas that has been cooled to enable easy and safe transportation of natural gas to distant places that are difficult to be reached by pipelines.

20. Why LNG ? Many people in need of energy are located far from gas fields , making pipelines too impractical or costly to build. To get around this problem, gas can be cooled to make a liquid, shrinking its volume for easier, safer storage and shipping overseas. This process creates liquefied natural gas (LNG).

21. Image: Qatargas is the world’s largest LNG producing company. Photo courtesy of Qatargas Operating Company Limited. The world's largest exporter of liquefied natural gas (LNG) in 2022 was Qatar.

22. Liquefied natural gas (LNG) is natural gas that has been cooled to a liquid state, at about -260° Fahrenheit, for shipping and storage. The volume of natural gas in its liquid state is about 600 times smaller than its volume in its gaseous state. This process makes it possible to transport natural gas to places pipelines do not reach.

23. Liquefying natural gas is a way to move natural gas long distances when pipeline transport is not feasible. Markets that are too far away from producing regions to be connected directly to pipelines have access to natural gas because of LNG. In its compact liquid form, natural gas can be shipped in special tankers to terminals around the world. At these terminals, the LNG is returned to its gaseous state and transported by pipeline to distribution companies, industrial consumers, and power plants.

24. A typical LNG process

25. Composition of LNG Liquefied natural gas (LNG) is natural gas (predominantly methane, CH4, with some mixture of ethane, C2H6) that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. It takes up about 1/600th the volume of natural gas in the gaseous state at standard conditions for temperature and pressure.

26. liquefied natural gas (LNG ) Process

27. Characteristics of LNG LNG is odourless, colourless, non-toxic and non-corrosive. Hazards include flammability after vaporization into a gaseous state, freezing and asphyxia.

28. The liquefaction process involves removal of certain components, such as dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream. The natural gas is then condensed into a liquid at close to atmospheric pressure by cooling it to approximately −162 °C (−260 °F); The maximum transport pressure is set at around 25 kPa (4 psi) (gauge pressure), which is about 1.25 times atmospheric pressure at sea level.

29. Synthesis gas Synthesis gas (Syngas) is the generic term for raw gas produced from feedstock hydrocarbon and It consists of hydrogen (H 2 ) and carbon monoxide (CO) as primarily components and carbon dioxide (CO 2 ), methane (CH4), etc. as remaining components. 

30. Syngas, or synthesis gas , is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as a fuel. Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited.

31. Production of Synthesis gas Syngas is produced by steam reforming or partial oxidation of natural gas or liquid hydrocarbons, or coal gasification.

32. Production of Synthesis gas by Steam reforming Steam reforming of methane is an endothermic reaction requiring 206 kJ/mol of methane: CH4 + H2O → CO + 3 H2

33. Tri-reforming of natural gas using flue gas for Syngas production

34. Syngas Process & Applications The syngas production process involves a variety of steps, including: (1) Drying : Drying involves inserting input feedstock like coal, biomass, petroleum residues, and other types of carbon-based materials into the gasifier. Biomass materials may include wood chips, corn husks, municipal or farm waste , and wastewater treatment sludge, among others. These materials may also require shredding or pulverizing prior to undergoing drying and subsequent gasification.

35. ( 2) Pyrolysis : This is a thermochemical treatment exposing materials to high pressure, high heat, and an oxygen-depleted environment. During this process , biomass breaks down into volatiles and charcoal.

36. ( 3) Combustion/Oxidation This process introduces a gasification agent to the materials, which usually comprises pure oxygen. Volatile matter in the mixture then degrades into multiple gases, resulting in a charcoal-like char byproduct . At this point, exothermic reactions generate CO2 and H2O. The summarized reaction is as such: Biomass + O2 → CO + H2 + CO2 + H2O + CH4.

37. ( 4) Reduction Through reduction, H2O and CO2 pass over charcoal, using endothermic reactions to convert them into CO and H2. Both of these gases are ideal for use as fuel gas.

38. Uses of Synthesis Gas Syngas is used as a source of hydrogen as well as a fuel. It is also used to directly reduce iron ore to sponge iron. Chemical uses include the production of methanol, liquid fuels and lubricants, ammonia via the Haber process, which converts atmospheric nitrogen (N2) into ammonia which is used as a fertilizer; and oxo alcohols via an intermediate aldehyde.