Opening the crude flexibility window: automation manages threats in real time

By increasing the volume of quality data, refiners can automate the correct addition of chemical additives to respond to variations in unit performance

Nalco Water

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Article Summary

The volatility of today’s crude prices presents refiners with the opportunity to significantly increase operating margins by expanding their crude diet to include more opportunity crudes. Given the fact that a refinery’s largest operational expenditure is purchasing crude oil, the processing of discounted opportunity crudes is a key lever to improve profitability and competitiveness. For example, a discount of just $0.50/bbl from the standard crude slate for an opportunity crude could raise the profitability of a typical 200 000 b/d refinery by $35 million/y.1

However, processing a more diversified crude slate that includes opportunity crudes increases the level of risk to the refinery with the potential for significant processing challenges. Refiners must be able to successfully manage this risk and maintain asset reliability while at the same time being constrained by capex and opex budget limitations.

Consequently, to maximise their profits and reduce the level of risk, refiners need to take a holistic approach to processing these opportunity crudes.

Communication between crude buyers, refiners and speciality chemical service companies, like Nalco Champion, is essential in identifying, assessing and mitigating the potential risks in processing opportunity crude. Anticipation of the key challenges some of these opportunity crudes have on crude unit and wastewater plant operations before they are processed is a critical aspect to consider. While crude assays do not contain all the information that is needed to identify potential challenges, they can be anticipated with operating strategies developed based on processing experience for crudes that have been out on the market for some time.

However, processing experience may not be available for newer crudes and a refinery could suffer a nasty surprise that quickly erodes the anticipated profitability. In these instances, Nalco Champion can work with the refiner to determine the level of risk associated with processing opportunity crudes in four key areas — specifically, desalting, fouling, corrosion, and waste plant performance — by undertaking specific laboratory evaluations prior to the crude being processed.

In two previous articles (see PTQ Q2 2017 and Q1 2018), we covered how ‘best in class’ desalting treatment accompanied by a rigorous mechanical-operational-chemical optimisation programme can deliver significant improvements in desalter performance to units that struggle to meet performance targets. This operational agility enables a refiner to capitalise on cost advantaged crude slates when they are processed.

Secondly, the monitoring of the process must evolve from long established practices that are arguably not fit for purpose, with the industry looking to embrace new technologies that are able to provide the volume of quality data in real time. By having a continuous view into the desalting process and key parameters of the crude unit overhead, the refiner is afforded increased levels of insight that can be used to identify the root causes of events or upsets that occur and then take this information to understand the “why”.

Essentially, the increased volume of good data allows us to make smart, informed decisions, allowing Nalco Champion and the refiner to take proactive measures to mitigate threats and process upsets before they can escalate and considerable damage occurs.

In this article, we will discuss the next step in the evolution of these innovative analysers and how real time data can be used to automate the control of chemical programmes and operational parameters, delivering a further step change in reliability of the crude distillation unit and wastewater treatment plant operations.

Traditional methods of monitoring and control
It is typical for refiners to assess the performance of their desalters and overhead corrosive environment on an arbitrary but set frequency. However, this frequency can vary significantly from refinery to refinery, with the most frequent approach to monitoring these parameters being once a day, typically during the day shift. During periods of continuous, stable operation, this is a reasonable approach. However, when short periods of unstable operation occur, the chances of concurrent samples being captured are low, meaning that the refiner is not getting a truly accurate and comprehensive view of what is happening. The major flaws in the traditional approach to monitoring are the frequency of data collection and the time lag before corrective actions are taken.

Many refineries process a large basket of crudes and these are likely to be more susceptible to periods of unstable operation. Consequently, they need an improved means to determine key process parameters relative to desalting, overhead corrosion and effluent treatment plant conditions. Without an improved insight, they tend to feed process additives (demulsifier, caustic, neutraliser, filmer, coagulants, and flocculants) to a baseline dose rate or adjusted based on infrequent lagging sample results to meet demand. Under current practices, refiners are not capable of measuring or responding to system changes or unstable operations fast enough. The net result is that the right amount of chemical is rarely injected at the right time.2

Refiners need to access data on key process parameters (salt in crude, overhead pH, and so on) on a far more frequent basis if they are to gain an understanding of the impacts that opportunity crudes are having on their equipment performance and reliability.  As discussed in the most recent of our articles, data are the product of observation, so it goes without saying that the more data we can collect on specific parameters, the greater clarity we have as to what is truly happening.  This allows us to place the correct context to the data so that we can fully answer the “what, where and when” questions, which then provides us with the knowledge to understand why an event has occurred.3

Once we understand the “why”, we have an objective, evaluated understanding of the problem at hand and, based on this, we have actionable intelligence to put corrective measures in place before a significant event can escalate.

An obvious development to this is that with the increased volume of good quality data it is possible to link the addition of chemical additives based on system demands at that moment in time and to put these under direct control. By doing this, the PLC in the analyser responds to changes in near real time, sending signals to the chemical dosing pumps to deliver precisely the right amount of chemical in the right place at the right time, mirroring variations in unit performance.

This is a significant departure from the current practice of flat baseline feeding of chemical, where constant under- or over-dosing is expected. Instead, the automation of chemical dosing achieves unprecedented control based on the refiner’s unique control parameters, limits and system requirements. By adopting the new Nalco Champion 3D Crudeflex platform, the delivered results significantly improved performance and these are discussed in the following case studies.

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