Fractionation
NoDoC cost models considers fractionation as a unit operation utilized to separate mixtures into individual products. Fractionation involves separating components by relative volatility. The difficulty of a separation is directly related to the relative volatility of the components and the required purity of the product streams. Virtually all gas processing plants producing natural gas liquids require at least one fractionator to produce a liquid product which will meet sales specifications. Heat is introduced to the reboiler to produce stripping vapors. The vapor rises through the column contacting the descending liquid. The vapor leaving the top of the column enters the condenser where heat is removed by some type of cooling medium. Liquid is returned to the column as reflux to limit the loss of heavy components overhead.
NoDoC simulation considers the number and type of fractionators based on the number of products to be made and the feed composition. Typical NGL products from a fractionation process that NoDoC presents include:
• Demethanized Product (C2+)
• Deethanized Product (C3+)
• Ethane/Propane mixtures (EP)
• Commercial Propane
• Propane/Butane mixture (LPG)
• Butane(s)
• Butane/Gasoline mixtures
• Natural Gasoline
• Mixtures with a vapor pressure specification
The feed stream contains too much ethane to be included in the products; thus, the first column is a deethanizer. The overhead stream is recycled to the upstream processing plant or sent to a fuel system. The bottom product from this column could be marketed as a deethanized product. The second column, a depropanizer, produces a specification propane product overhead. The bottom product, a butane-gasoline mixture, is often sold to a pipeline without further processing. The third column, a debutanizer, separates the butane and gasoline products. This separation is controlled to limit the vapor pressure of the gasoline. The overhead butane product can be sold as a mixture or an additional column can be used to separate the iso-butane and normal butane.
The columns can be trayed or packed and there are different types of trays and packings that the NoDoC considers in addition with other parameters.
NoDoC simulation considers the number and type of fractionators based on the number of products to be made and the feed composition. Typical NGL products from a fractionation process that NoDoC presents include:
• Demethanized Product (C2+)
• Deethanized Product (C3+)
• Ethane/Propane mixtures (EP)
• Commercial Propane
• Propane/Butane mixture (LPG)
• Butane(s)
• Butane/Gasoline mixtures
• Natural Gasoline
• Mixtures with a vapor pressure specification
The feed stream contains too much ethane to be included in the products; thus, the first column is a deethanizer. The overhead stream is recycled to the upstream processing plant or sent to a fuel system. The bottom product from this column could be marketed as a deethanized product. The second column, a depropanizer, produces a specification propane product overhead. The bottom product, a butane-gasoline mixture, is often sold to a pipeline without further processing. The third column, a debutanizer, separates the butane and gasoline products. This separation is controlled to limit the vapor pressure of the gasoline. The overhead butane product can be sold as a mixture or an additional column can be used to separate the iso-butane and normal butane.
The columns can be trayed or packed and there are different types of trays and packings that the NoDoC considers in addition with other parameters.
