Profit Maximization Techniques for Operating Chemical Plants. Sandip K. Lahiri
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3 Profit Maximization Project (PMP) Implementation Steps
3.1 Implementing a Profit Maximization Project (PMP)
Once a process unit is identified as a potential PMP application, then the following project steps are required to implement the project. These project steps are not written in stone and can be changed and modified as per the needs of individual chemical companies. Various global giant chemical companies have implemented these steps to a varying degree and have sometimes modified the sequence of these steps as per their own strength and business requirements. The project steps are summarized in Figure 3.1.
In the following sections, each of these steps is discussed.
3.1.1 Step 1: Mapping the Whole Plant in Monetary Terms
The aim of a profit maximization project is to maximize the profit generation in dollar per hour terms and sustain the profit at its peak value. Hence the first step of a PMP project is to calculate how much USD/h profit is generating from the plant in every hour on a real‐time basis. As a first step this is done by considering the whole plant as a big black box and mapping it as raw material and utilities as input to the black box and product waste and vent losses as output from the box. The value of each of these inputs and outputs are then calculated as a USD/h term. This gives an overall idea of how much profit is generating from the whole plant. In a second step, a more detailed calculation was done to estimate the USD/h generated or consumed in each major process equipment for the whole plant. Mapping the whole process in USD/h terms makes it easy to view where the actual loss of profit is occurring and to focus on that. This also combines different performance parameters usually used in process industries, like energy efficiency, yield, selectivity, specific consumption of utilities, etc., in a single cost framework and in order to make it easy to visualize the whole process in a single unit of measurements. This will help to access the current operation of the plant and gives an indication of where to focus in order to increase profit.
3.1.2 Step 2: Assessment of Current Plant Conditions
Various process equipment like distillation columns, reactors, furnaces, heat exchangers, pumps and compressors, etc., form the backbone of chemical plants. Before jumping to increase profit, it is very important to know how they are performing currently in the plant. In this step, the performance of various process equipment is assessed and any performance limitations are critically examined. It also involves assessing the efficiency of different parts of the process, such as yield, catalyst selectivity, quality consistency, etc. It is of the utmost importance to assess the performance of a base process and equipment layer and improve it before trying to build a PMP application over it. In this step an overall assessment of the base equipment layer was performed scientifically and corrective steps were taken to rectify limitations, if any (Lahiri, 2017c). This essentially means identification of any problems in distillation columns, reactors, furnaces, heat exchangers, pumps, and compressors and applies to various techniques like maintenance of rotating equipment, heat exchanger cleaning, etc., to rectify the problems.
Figure 3.1 Different steps in profit maximization project (PMP) implementation
3.1.3 Step 3: Assessment of the Base Control Layer of the Plant
The regulatory proportional, integral, and derivative (PID) control loop forms the base layer of a control system. It is of the utmost importance to assess the performance of the base control layer and improve upon it before trying to build a PMP application over it. In this step an overall assessment of the base control layer was performed scientifically and corrective steps were taken to rectify limitations, if any. This essentially means identification of any problems in control valves (like hysteresis, stiction, valve oversize, or undersize phenomena), measuring sensors (like noise, range of instruments, calibration, etc.), PID controller tuning, oscillation in process parameters, etc., and application of various techniques like controller tuning, maintenance of control valves, calibration of instruments, etc., to rectify the problems (Lahiri, 2017a). Enhancement of control performance actually reduces the variations in key economic parameters of a process and then the DCS panel engineer is able to push the process further near to its constraints. Using only this step, a 1–5% increase in profit has been reported in various literatures by various global chemical companies.
3.1.4 Step 4: Assessment of Loss from the Plant
What are the major energy and product losses in a process? This is the first question that people should ask before embarking on a significant effort to improve profit. The answer to this question could lead to identification of major improvement opportunities and help to define the need for a large profit improvement effort. In a chemical process, a valuable product can be lost either with wastewater or vent to flare. In this step, a systematic approach is followed to calculate how much money gets lost in USD/h terms due to waste and vent. Not only product loss, but also energy loss, account for a major erosion of profit in many chemical plants. In a process, energy losses consist of both thermal and mechanical losses (Zhu, 2013). Thermal losses typically originate from column overhead condensers, product rundown coolers, furnace stack, steam leaks, poor insulation of heat exchangers/piping and vessels, and so on. Mechanical losses could also be significant, which usually occurs in rotating equipment, pressure letdown valves, control valves, pump spill back, heat exchangers, pipelines, and so on. Some of the wastewater, vent gas to flare, and thermal and mechanical losses are recoverable with a decent payback of investment, but many others do not. An energy and product loss audit seeks to identify key recoverable losses. The audit is relatively quick and is designed to determine improvement potential. If the energy loss audit identifies large energy or product losses, more detailed energy assessment efforts will be undertaken later if so required. After identifying all the product and energy losses in a chemical complex, small improvement projects can be initiated and implemented to stop or reduce these losses. In this way, by reducing the money drain from plants, profit can be increased. Many companies in the world have been able to increase their profit 1–5% by following this simple but effective step.
3.1.5 Step 5: Identification of Improvement Opportunity in Plant and Functional Design of PMP Applications
Before building a PMP application for a process, the concerned chemical engineer must understand all the relevant aspects of the process, its various limitations, how it makes profit, and what area can be exploited to increase profit. As a starting step, the PMP engineer usually surveys PFDs and P&IDs of the process under study, meets with operations engineers and a specialized work force, and finds all the opportunities