Description

Chemical Plant Optimization

1.       Introduction (20):

1.1.   Analysis Customer/Consumer (4):

The Chemical Optimizer is a distillation system that can be tailored for various companies such as Exxon, Shell etc. in the crude oil sector. The function of the System of Interest (SOI) is to efficiently separate crude oil into the multiple constituents within it so it can further utilized by the United States chemical industry.

 1.2.   Analysis Goal/Purpose/Objective (8)

The idea behind the SOI is the design of a distillation column called the ‘Chemical Optimizer’ (CO). The objective is to convert fluid into its different constituents through the process of fractional distillation. The objective function for this could be to maximize the Reflux Ratio which in return can be used to minimize the Total Cost of operating the system. . Reflux Ratio (RI) is the ratio between the boil up rate and the take-off rate. Or in other words it is the ratio between the amount of reflux that goes back down the distillation column and the amount of reflux that is collected [1]. There are three input factors that will be varied in order to achieve the objective stated above. These are, Heat Energy removed in the condenser, Heat Energy added for the re-boiler and Number of Trays. The fixed factors shall be the diameter and operating pressure of the distillation column, the input feed rate (mass flow rate) and performance factors of the condenser and the reboiler etc.)

1.3.   System Description (8):

As stated in Section 1.2, the SOI is called a Chemical Optimizer that consists of various components such as Distillation Column (which consists of two predefined areas, the Enriching Section and the Stripping Section, and a point of feed entry), a Condenser that is used on the Top Product to reflux back some of it in order to separate the constituents purely, and finally the Re-boiler which is also used to heat and send back the bottom product into the column. Before we delve into the operation side of the SOI it is important to understand the background concepts of the process. The generic process being implemented in the chemical plant is ‘Fractional Distillation’ which is the process through which oil refineries separate crude oil into different, more useful hydrocarbon products based on their molecular weights in a distillation tower. This is the first step in the processing of crude oil and is considered to be the main separation process as it performs the initial rough separation of different fuels [2]. The constituents that are separated in this process are known as fractions.

The process works as follows:

1)     First the Feed is heated to vaporize

2)     Then it is fed into the Distillation Tower/Column

3)     The vapor then rises and falls through the vertical column which is divided into the enriching section (top half) and the stripping section (bottom half).

4)     As the vapor rises through the tower, the temperature inside decreases separating certain constituents of the feed according to their respective boiling points

5)     After this initial refinement, the separated constituents shall go under more refinement to remove any contaminants or undesirable substances, basically improving the purity of the constituent; this is where the Condenser and Reboiler, mentioned above, take action.

                                             Figure 1:  System Process

2.       Analysis Overview (40):

2.1.   Analysis Metrics (8)

The analysis of the project will focus on the two principal metrics in order to evaluate the optimal design option or course of action. The metrics are provided in Table 1 below.

 Table 1: System Metrics

2.2.   COA/Design Options (8):

Four design options have to be taken into account. All these design options vary the Capital Costs, Energy Requirements and Number of Trays.

Table 2: Design Options

2.3.   Analysis Factors (8):

There are five input factors that will be varied in order to achieve the objective stated above. These are, Capital Cost of Condenser, Heat Energy removed in the condenser, Capital Cost of Boiler, Heat Energy added for the reboiler and Number of Trays. The fixed factors shall be Input Feed Rate, Temperature, Vapor Flow Rate, Molar Enthalpy and Heat Capacity of separating constituents.

Table 3: Factors