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1、TECHNICAL SPECIFICATION CONTROL SYSTEM AND INSTRUMENTED PROTECTIVE FUNCTIONS FOR FIRED EQUIPMENT - System for a tangentially gas-fired CO boiler (S 24.036) DEP 32.24.20.40-Gen. July 1997 (DEP Circular 57/97 has been incorporated) DESIGN AND ENGINEERING PRACTICE USED BY COMPANIES OF THE ROYAL DUTCH/S
2、HELL GROUP This document is confidential. Neither the whole nor any part of this document may be disclosed to any third party without the prior written consent of Shell International Oil Products B.V. and Shell International Exploration and Production B.V., The Hague, The Netherlands. The copyright
3、of this document is vested in these companies. All rights reserved. Neither the whole nor any part of this document may be reproduced, stored in any retrieval system or transmitted in any form or by any means (electronic, mechanical, reprographic, recording or otherwise) without the prior written co
4、nsent of the copyright owners. PDF created with pdfFactory Pro trial version PREFACE DEP (Design and Engineering Practice) publications reflect the views, at the time of publication, of: Shell International Oil Products B.V. (SIOP) and Shell International Exploration and Production B.V. (SIEP) and
5、Shell International Chemicals B.V. (SIC) The Hague, The Netherlands, and other Service Companies. They are based on the experience acquired during their involvement with the design, construction, operation and maintenance of processing units and facilities, and they are supplemented with the experie
6、nce of Group Operating companies. Where appropriate they are based on, or reference is made to, national and international standards and codes of practice. The objective is to set the recommended standard for good design and engineering practice applied by Group companies operating an oil refinery,
7、gas handling installation, chemical plant, oil and gas production facility, or any other such facility, and thereby to achieve maximum technical and economic benefit from standardization. The information set forth in these publications is provided to users for their consideration and decision to imp
8、lement. This is of particular importance where DEPs may not cover every requirement or diversity of condition at each locality. The system of DEPs is expected to be sufficiently flexible to allow individual operating companies to adapt the information set forth in DEPs to their own environment and r
9、equirements. When Contractors or Manufacturers/Suppliers use DEPs they shall be solely responsible for the quality of work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, the Principal will expect them to follow tho
10、se design and engineering practices which will achieve the same level of integrity as reflected in the DEPs. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the Principal or its technical advisor. The right to use DEPs is granted by
11、 SIOP, SIEP or SIC, in most cases under Service Agreements primarily with companies of the Royal Dutch/Shell Group and other companies receiving technical advice and services from SIOP, SIEP or SIC. Consequently, three categories of users of DEPs can be distinguished: 1)Operating companies having a
12、Service Agreement with SIOP, SIEP, SIC or other Service Company. The use of DEPs by these Operating companies is subject in all respects to the terms and conditions of the relevant Service Agreement. 2)Other parties who are authorized to use DEPs subject to appropriate contractual arrangements. 3)Co
13、ntractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) or 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards. Subject to any particular terms and
14、 conditions as may be set forth in specific agreements with users, SIOP, SIEP and SIC disclaim any liability of whatsoever nature for any damage (including injury or death) suffered by any company or person whomsoever as a result of or in connection with the use, application or implementation of any
15、 DEP, combination of DEPs or any part thereof. The benefit of this disclaimer shall inure in all respects to SIOP, SIEP, SIC and/or any company affiliated to these companies that may issue DEPs or require the use of DEPs. Without prejudice to any specific terms in respect of confidentiality under re
16、levant contractual arrangements, DEPs shall not, without the prior written consent of SIOP and SIEP, be disclosed by users to any company or person whomsoever and the DEPs shall be used exclusively for the purpose for which they have been provided to the user. They shall be returned after use, inclu
17、ding any copies which shall only be made by users with the express prior written consent of SIOP and SIEP. The copyright of DEPs vests in SIOP and SIEP. Users shall arrange for DEPs to be held in safe custody and SIOP or SIEP may at any time require information satisfactory to them in order to ascer
18、tain how users implement this requirement. All administrative queries should be directed to the DEP Administrator in SIOP. NOTE: In addition to DEP publications there are Standard Specifications and Draft DEPs for Development (DDDs). DDDs generally introduce new procedures or techniques that will pr
19、obably need updating as further experience develops during their use. The above requirements for distribution and use of DEPs are also applicable to Standard Specifications and DDDs. Standard Specifications and DDDs will gradually be replaced byDEPs. DEP 32.24.20.40-Gen. July 1997 Page 2 PDF created
20、 with pdfFactory Pro trial version TABLE OF CONTENTS 1.INTRODUCTION4 1.1SCOPE.4 1.2DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS 4 1.3DEFINITIONS AND ABBREVIATIONS.4 1.4CROSS-REFERENCES5 2.GENERAL6 3.FUNCTIONAL (OPERATIONAL) DESCRIPTION 7 3.1LOAD CONTROL .7 3.2AIR/FUEL RATIO CONTROL .7 3
21、.3START-UP .8 4.TECHNICAL DESCRIPTION10 4.1IMPLEMENTATION CONSIDERATIONS. 10 4.2LOCATION OF ALARMS, SWITCHES, ETC11 4.3CALCULATION FORMULAE12 4.4DESCRIPTION OF INSTRUMENTED PROTECTIVE FUNCTIONS15 4.5IPF CLASSIFICATION AND CAUSE AND EFFECT DIAGRAM20 5.REFERENCES.22 APPENDICES APPENDIX 1Functional log
22、ic diagrams for a tangentially gas-fired CO boiler.23 DEP 32.24.20.40-Gen. July 1997 Page 3 PDF created with pdfFactory Pro trial version 1.INTRODUCTION 1.1SCOPE This DEP specifies requirements and gives recommendations for control systems and instrumented protective functions for a tangentially ga
23、s-fired CO boiler. This DEP shall not be used for any other equipment or firing configuration. This DEP contains a control and IPF narrative and logic diagrams and refers to a standard specific process engineering flow scheme. This DEP shall be used together with Standard Drawing S 24.036. This DEP
24、is written for systems which use DCS for control and monitoring and PLC and Solod State / Magnetic core type Instrumented Protective Functions. Accordingly, more use has been made of inverted signals than would have been the case for relay type IPFs. 1.2DISTRIBUTION, INTENDED USE AND REGULATORY CONS
25、IDERATIONS Unless otherwise authorised by SIOP and SIEP, the distribution of this DEP is confined to companies forming part of or managed by the Royal Dutch/Shell Group, and to Contractors nominated by them (i.e. the distribution code is “C“, as defined in DEP 00.00.05.05-Gen.). This DEP is intended
26、 for use in oil refineries. If national and/or local regulations exist in which some of the requirements may be more stringent than in this DEP the Contractor shall determine by careful scrutiny which of the requirements are the more stringent and which combination of requirements will be acceptable
27、 as regards safety, economic and legal aspects. In all cases the Contractor shall inform the Principal of any deviation from the requirements of this DEP which is considered to be necessary in order to comply with national and/or local regulations. The Principal may then negotiate with the Authoriti
28、es concerned with the object of obtaining agreement to follow this DEP as closely as possible. 1.3DEFINITIONS AND ABBREVIATIONS 1.3.1General definitions The Contractor is the party which carries out all or part of the design, engineering, procurement, construction, commissioning or management of a p
29、roject or operation of a facility. The Principal may undertake all or part of the duties of the Contractor. The Principal is the party which initiates, and ultimately pays for, the project. The Principal will generally specify the technical requirements. The Principal may also include an agent or co
30、nsultant, authorised to act for the Principal. The word shall indicates a requirement. The word should indicates a recommendation. 1.3.2Specific definitions Instrumented protective functionA function comprising the Initiator function, Logic (IPF)Solver function and Final Element function for the pur
31、pose of preventing or mitigating Hazardous Situations. NOTE:The term “safeguarding“ is not widely used in this DEP because safeguarding relates not only to instrumented protective functions but also to protective equipment of a mechanical nature such as non- return valves, relief valves and bursting
32、 disks. DEP 32.24.20.40-Gen. July 1997 Page 4 PDF created with pdfFactory Pro trial version 1.3.3Abbreviations ARWUAnti reset wind-up COCarbon monoxide DCSDistributed control system IPFInstrumented protective function MCRMaximum continuous rating PEFSProcess engineering flow scheme PLCProgrammable
33、logic controller SRFStandard refinery fuel TSOVTight shut off valve 1.4CROSS-REFERENCES Where cross-references to other parts of this DEP are made, the referenced section number is shown in brackets. Other documents referenced by this DEP are listed in (5). DEP 32.24.20.40-Gen. July 1997 Page 5 PDF
34、created with pdfFactory Pro trial version 2.GENERAL This DEP shall be used as the basis for the control systems, IPFs, narratives, functional logic diagrams and PEFS for the installation for which it has been specified by the Principal. The Contractor shall prepare installation-specific narratives
35、based on this DEP, and shall add relevant tag numbers, set points, controller configurations, etc. The installation- specific narratives shall not contain general information which is not relevant to the specific installation. Like this DEP, the narrative shall contain a functional description inclu
36、ding operational aspects and a detailed technical description. DEP 32.24.20.40-Gen. July 1997 Page 6 PDF created with pdfFactory Pro trial version 3.FUNCTIONAL (OPERATIONAL) DESCRIPTION 3.1LOAD CONTROL Flow control is the lowest level of control function for fuel gas and combustion air. Minimum com
37、bustion air flow is ensured by an adjustable mechanical minimum stop on the combustion air damper, while maximum combustion air flow is limited by the capacity of the blower and burner resistance. Minimum fuel gas flow is ensured by a minimum stop pressure controller which guarantees a minimum burne
38、r load, irrespective of the number of burners in operation. Similarly, maximum burner load is limited by a maximum stop pressure controller. Note:The fuel gas pressure control limiter does not provide absolute limits to burner load since this is also affected by variations in the density of the fuel
39、 gas. In addition to the minimum stop fuel pressure controller, the fuel control valve is provided with a mechanical minimum stop. This is adjusted to correspond to minimum load with only one burner in operation, and acts as a pre-set valve position for start-up of the first burner. The control syst
40、em works as follows: The heat input from the regenerator off-gas (sensible heat and heat of combustion) is calculated on the basis of the total air flow to the regenerator (including catalyst transport air), the CO content in the off-gas and the temperature of the off-gas to the boiler, and is conve
41、rted into SRF equivalent values. The SRF equivalent of the sensible heat in the off-gas is subtracted from the output signal of the master steam flow controller. The resultant signal, representing the total fuel demand (including CO), is then passed to the fuel gas flow controller via the air/fuel r
42、atio control system. The SRF equivalent (in terms of stoichiometric air requirement) of the CO is subtracted from the required fuel flow signal going to the fuel gas flow controller. The SRF equivalent (in terms of stoichiometric air requirement) of the CO is added to the measured fuel gas flow befo
43、re this signal is fed to the air/fuel ratio control scheme. Depending on the variation in the MW of the fuel gas, the fuel gas flow measurement shall be corrected for changes in gas density (see Section 4.3, Y4). This density compensation compensates for errors in flow measurement and for changes in
44、 stoichiometric air requirement. As the compensated signal also gives a reasonably accurate representation of heat input this signal is also used as input to the fuel flow controller. In this way the fuel gas flow controller indicates a flow in Standard Refinery Fuel (SRF). 3.2AIR/FUEL RATIO CONTROL
45、 In parallel to adjusting the fuel flow, the fuel demand signal passes via the air/fuel ratio relay to adjust the setpoint of the combustion air flow controller. The required air/fuel ratio may either be manually set by the panel operator or automatically set by a closed-loop stack oxygen controller
46、. Limits should be set to the range over which the air/fuel ratio can be adjusted, in order to prevent settings that correspond to sub-stoichiometric combustion. In addition to the basic parallel control system described above, limits are imposed on the adjustment of the set points of fuel and combu
47、stion air, as follows: -This measured fuel gas flow, including the SRF equivalent CO flow (in terms of air requirement), is multiplied by a factor (typically 0.9), and provides a minimum limit (via a high selector) to the total fuel demand signal to be sent to the combustion air flow controller setp
48、oint. If the total fuel demand decreases, and the actual fuel flow does not react, this signal will limit the decrease in the combustion air flow to prevent sub- stoichiometric combustion. The control system changes from a “parallel“ control system to a “fuel-leading“ system (fuel decrease leads air
49、 decrease) after the high selector has limited the decrease in combustion air flow. DEP 32.24.20.40-Gen. July 1997 Page 7 PDF created with pdfFactory Pro trial version A similar system applies to the fuel gas flow, as follows: -the measured combustion air flow passes through a “minimum air/fuel ratio“ relay (with a setting typically 10% lower than the normal air/fuel ratio, and the signal provides a maximum limit (via a low selector) to the fuel demand signal to be sen