PrintOverview
Video: Lesson 12 (5:38)
PRESENTER: Natural gas is a very important fuel fossil fuel in the United States. Its significance has increased since the hydrofracking operations to produce shale gas as an unconventional source for natural gas. Now, the production of natural gas through hydrofracking or other techniques is beyond the scope of this course. But we will focus on the processing of natural gas as it comes out of the ground.
The main component of natural gas is methane, but it also contains heavier hydrocarbons-- principally, ethane, propane, butane and pentanes, which may be referred to as the natural gas liquids. In addition, the raw gas could contain significant amounts of water, hydrogen sulfide, carbon dioxide, and nitrogen, in some cases. So there is a need to process the natural gas as it comes out of the ground before it is sent to, or fed into the pipeline system for transport to remote locations.
There are essentially four components of natural gas processing, which are oil and condensate removal, and sulfur and carbon dioxide removal. Sulfur comes out as H2S, mainly. Removing water is important, and the separation and fractionation of natural gas liquids. That's anywhere from butane or propane, butane up to and about pentanes.
Now, as we have talked about before, these natural gas liquids are-- in a sense-- newer feeds to the refinery as liquid materials to be blended into practically to gasoline product as an additional feed material. So it's important that we really look at this natural gas processing techniques.
Now, for processing of natural gas, we use pretty much the same techniques as we have in petroleum refining. One major process is, of course, removal of H2S and carbon dioxide as acid gases. We'll use the amine absorption or solutions that contain the base-- ethanolamine or diethanolamine-- to absorb these acid gases, H2S and carbon dioxide, which are, of course sent to sulfur recovery using, again, the similar techniques that we have talked about for petroleum refining. That is the Claus and then also the SCOT method.
The separation and fractionation of natural gas liquids uses essentially the same processes as we have talked about in the lights end unit-- a petroleum refinery-- to separate ethane and butane and propane and the heavier liquids in this unit. That's essentially going to be a similar setup as we have talked about in the lights end unit.
Overview
Natural gas has become a very significant fossil fuel in the U.S. because of a sharp increase in shale gas production starting in 2006. The U.S. Energy Information Administration projects that the U.S. natural gas production will increase 44% from 23.0 trillion cubic feet in 2011 to 33.1 trillion cubic feet in 2040 [1]. Almost all of this increase in domestic natural gas production is due to projected growth in shale gas production, which is projected to grow from 7.8 trillion cubic feet in 2011 to 16.7 trillion cubic feet in 2040. It is interesting to note that before the shale gas boom (that has taken place largely in Pennsylvania), the U.S. was planning to import liquefied natural gas (LNG) from countries as far as Peru with the planned construction of LNG ports in California and other states. Currently, there are prospects of exporting LNG overseas in the near future. One particular aspect of the natural gas boom that concerns the petroleum refining industry is the increased production of natural gas liquids (NGL) that are co-produced with natural gas. NGL consist of light hydrocarbons, and they have become an important non-conventional feedstock for refineries, contributing mainly to gasoline production. This new input to refineries along with the increased domestic oil production by the new drilling technology has helped small inland refineries that do not have easy access to imported crude oil as, for example, Gulf Coast refineries.
This lesson will provide an overview of the natural gas processing that employs the same techniques and processes as we have covered in petroleum refining operations, such as in Light Ends Unit for fractionation of light hydrocarbons, and recovering H2S, as well as its conversion to S. Brief introductions to shale gas and natural gas liquids will be presented before discussing the natural gas processing.
Learning Outcomes
By the end of this lesson, you should be able to:
- appraise different natural gas reserves (conventional, tight, and shale) and assess the contribution of natural gas to energy supply;
- illustrate and evaluate the different stages of natural gas processing, including condensate removal, acid gas removal, water removal, fractionation of natural gas liquids.
What is due for Lesson 12?
This lesson will take us one week to complete. Please refer to the Course Syllabus for specific time frames and due dates. Specific directions for the assignment below can be found in this lesson.
| Readings: | Natural Gas |
|---|---|
| Assignments: |
Review the DOE page on shalle gas: https://www.energy.gov/articles/producing-natural-gas-shale |
Questions?
If you have any questions, please post them to our Help Discussion (not email), located in Canvas. I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.