The benefits of sample handling system design, related to the integrity and reliablility of on-line process analyzer.

Transcription

1 Castello di Belgioioso Pavia July 5 and 6, 2017 AUTOMATION INSTRUMENTATION SUMMIT The benefits of sample handling system design, related to the integrity and reliablility of on-line process analyzer. G.Severi G.Tani

2 Summary 1. Fores Engineering Overview 2. Sampling System Architecture 3. Sample Conditioning 4. Compatible Sample 5. Timely Sample 6. Representative Sample 7. A Real Project 7.1 Critical Issues 7.2 Process Analisys 7.3 P&ID 7.4 Sample Control 8. Conclusions

3 Integration Skid&Packages Automation Telecom Oil&Gas 1.Fores Engineering Overview Petrochemical Power Plant Chemical Expertise Reliability Worldwide Teamwork Engineering Procurement Construction

4 1.Fores Engineering Overview Fores Engineering Srl is an Italian company part of the Rosetti Marino Group, founded in 1992, specialized in the design, integration and construction of different EPC System and Products for Oil & Gas, Petrochemical, Chemical and Energy industry. The production structure of the company is divided in three main operative units: Skid & Packages Automation, Telecom and Security Industrial Service All the units operate both independently and in complete synergy, allowing the company to focus its attention on maintaining a high level of customer satisfaction. The main activities are Project Management, Engineering, Procurement, Integration, Construction, Testing and Commissioning of its products. In addition, Fores Engineering provides Technical Supervision Services and After-sale Technical Assistance Services, such as Assistance and Supervision to the construction activities, commissioning activities and start-up activities, supply of spare parts and training in the field.

5 1.Fores Engineering Overview

6 2.Sampling System Architecture The good design of this chain is critical as the analyzer choice Collection of the sample from the take-off point Sample Preconditioning Sample Transport Line Sample Conditioning Sample Analysis Exhaust Sample Outlet Pressure Regulation Vaporization Transport to the Analyzer Temperature Control Analysis Analyzer of the Sample. Collection of a significant and useful amount of sample to be analyzed. Fast Loop Sample Flow Control Exhaust sample to flare (or) Return to the process

7 3.Why a Sampling System? Often, a considerable amount of attention is normally given to the choice of the most suitable type of analyzer to perform the analytical task, whereas no similar care it s given to the sample handling system. A sample handling system, throught a pre-conditioning and conditioning subsystem, is necessary to guarantee a fluid sample compatible with the requirements of the Analyzer. That means: Compatible Sample >>> ensures the analyzer will work. Timely Sample >>> ensures a current measurement result. Representative Sample >>> ensures the right answer. The analyzer is unable to detect the bad sample or to correct the inconsistency of the analysis.

8 4.Compatible Sample The purpose of sample conditioning is to modify and control the condition of the sample to ensure that it is always compatible with the analyzer: A compatible sample will not harm the analyzer. A compatible sample prevent the analyzer from producing a reliable analytical result. It may be necessary: Remove excess solids Remove liquid drops from gas Remove bubbles from liquid Adjust temperature, pressure and flow Set pressure and temperature to avoid a two-phase sample Ensure wet materials are compatible with the sample

9 5.Timely Sample Time Lag: time between the collection of the sample at the take-off point and the analyzer inlet. The standard transport time is 1 minute maximum. A timely sample is one that provides an analysis with an acceptable delay from real time of the sample collection at the take-off. Some point where time delay happens: Sample transport line Sample pipe or vessels Sample conditioning Sample extraction Sample stream selection by the control system

10 6.Representative Sample Precise Result is one that carries a high degree of confidence. Accurate Result is one that closely represents the true value of the measurement. Representative Sample is one that provides a meaningful analytical result useful for its intended purpose. Why a sample is not representative? Composition Change Contamination Two-phase sample due to a not well controlled temperature and pressure Chemical Reaction between sample molecules or between sample molecules and wet materials of construction

11 7. A Real Application Scope of work Supply of Analyzer Shelters and ancillaries to be installed in EAU composed by the following main items: No. 2 Gas Chromatographs with two different ovens for each one: H 2 S analisys and Hydrocarbons analisys. No.2 Sample Streams for each Gas Chromatograph to be collected to both the ovens. Sample Transport Lines. Pre-Conditioning Systems for each sample stream. Sample Conditioning System for each analyzer.

12 7.1 A Real Application Critical issues Some critical issues of the project: Critical composition, temperature and pressure of the sample fluid. [T dp =43 C > T amb ] Ambient temperature range. [ T amb = C ] Sample streams selection to the desired oven. [ No. 2 Streams to No. 2 independent Ovens ] Long distance from the sample collection point and the analyzer inlet. [ L stl > 80 m ] Analyzer requirements: flowrate, temperature and pressure of the sample. [ Q s = 6 Nl/h, +30 C < T s < +120 C, P s < 3 barg ]

13 7.2 A Real Application Process Analysis Sample composition Component Molar Fraction CH 4 74,86% C 2 H 6 7,38% C 3 H 8 4,85% C 4 H 10 1,07% CO 2 4,85% H 2 S 32,38% T, P, Flowrate required by the Gas Chromatograph Sample Transport Line lenght Sample Temperature and Pressure at the Take-off Point Sample Chemical Properties Pre-conditioning system Conditioning System Sample Transport Line Pressure Reduction Vaporizer Fast Loop Flow to Analyzer Sample Stream Selection Heated transport line to maintain the sample temperature Sizing of the line

14 7.3 A Real Application P&IDs Take-off Point Pre-Conditioning System Sample Transport Line Sample Conditioning System Fast Loop Control of the sample streams Analyzer Calibration Utilities

15 7.4 A Real Application Multistream System Pneumatic actuated three way valves with single and double effect have been used for the sample streams and calibration gas selection with double block & bleed configuration: Stream 1 to Analyzer Stream 2 to Analyzer Calibration Gas to Analyzer With this solution it s important to be careful to the analyzer control system time delay!

16 8. Conclusions A good and reliable Analyzer System should not ignore a careful and correct design of overall chain from process stream to analyzer, given the importance of sample compatibility, timing and representativeness, before it could be analyzed. Often there s a lack of understanding the importance of this pretreatment, jeopardising the correct analsyis and making more difficult the operation and maintenance activities as well. It's not just important the Analyzer, but also how the sample arrives to it. For info: gabriele.severi@fores.it gioele.tani@fores.it salvatore.mecca@fores.it THANK YOU ALL!