6.13-heating-system-design-philosophy.pdf

KCP-GNS-PCD-DPR-0008

Rev.: 03

Project Title: Kingsnorth Carbon Capture & Storage Project Page 1 of 17

Document Title: Heating System Design Philosophy

Kingsnorth CCS Demonstration Project The information contained in this document (the Information) is provided in good faith. E.ON UK plc, its subcontractors, subsidiaries, affiliates, employees, advisers, and the Department of Energy and Climate Change (DECC) make no representation or warranty as to the accuracy, reliability or completeness of the Information and neither E.ON UK plc nor any of its subcontractors, subsidiaries, affiliates, employees, advisers or DECC shall have any liability whatsoever for any direct or indirect loss howsoever arising from the use of the Information by any party.

Heating System Design Philosophy

Table of Contents

1. Scope and Functional Requirements ............................................................... 3

1.1 Introduction .................................................................................................... 3 1.2 Design Objectives ......................................................................................... 4 1.3 System Description ...................................................................................... 4

1.3.1 Rationale for Heating ............................................................................ 4 1.3.2 Heating Facilities Proposed ................................................................. 5 1.3.3 Heat Transfer Equipment ................................................................... 11

1.4 Quantification of Heating Duties ............................................................... 12 1.4.1 Injection Heating Duties ..................................................................... 12 1.4.2 Vent Heating Duties ............................................................................ 13

1.5 Requirement for New Facilities / Further Work ...................................... 13 2. Assumptions ....................................................................................................... 14 3. Design Requirements ....................................................................................... 15

3.1 Heat Loads .................................................................................................. 15 3.2 Temperature ................................................................................................ 15 3.3 Pressure ....................................................................................................... 15 3.4 Physical Properties ..................................................................................... 16 3.5 Materials of Construction ........................................................................... 16 3.6 Insulation ...................................................................................................... 16 3.7 Equipment Isolation / Protection .............................................................. 16 3.8 Process Control .......................................................................................... 16

4. Mandatory References ..................................................................................... 17 5. Supporting References ..................................................................................... 17


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Table of Figures

Figure 1-1 Gaseous Phase Case - Offshore Process Infrastructure ................ 6 Figure 1-2 : Proposed Offshore Infrastructure with Fired Heater ..................... 8 Figure 1-3 Full Flow Case With Separate Heaters on Each Flowline............. 10 Figure 1-4 : Estimated Field Life Injection Duties for Steady State Dense

Phase Operation and 1600 MWg Power Plant Capacity .......................... 12


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1. Scope and Functional Requirements

1.1 Introduction

This design philosophy describes the design requirements for the Heating System that is to be located offshore. The design philosophy will ensure that a consistent approach is taken by all parties throughout the design, construction and operational phases of the project. This document will cover the following elements:

Design Criteria

Rationale for Heating

Heating System Users

Quantification of Heating Duties

Consideration of Heating Source

Requirement for New Facilities / Further Work Heating will be required at the offshore infrastructure to avoid compromising system design temperatures. However, equipment that is downstream of the heater must be designed to cope with short term low temperatures in the event of heater failure. Additionally, heating is also required to protect the reservoir and wells from being subjected to multi-phase flow and low temperatures created by very cold CO2 that will be generated when there is a large differential pressure across the topsides choke valve. Such a scenario will persist mainly during dense phase operation of the system (start-up and normal operation), especially at lower reservoir pressures. However, there is also the potential for it to occur during line packing and / or start-up of the system when operating in gas phase mode. Therefore heating at the offshore infrastructure will be required for both modes of operation (S1 & S2).


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1.2 Design Objectives

The design objective is to ensure that essential heating requirements are supplied to the facilities under all foreseeable operating circumstances in the most effective manner. The system should also be able to be controlled / monitored remotely including start-up and shutdown. Priority shall be given to health, safety and environmental issues with a view to identification and elimination of potential hazards before they become a problem.

1.3 System Description

1.3.1 Rationale for Heating

It is anticipated that heating for the injection of CO2 at the offshore infrastructure will be required for dense phase mode start-up and normal operation, for gas phase mode start-up and line packing, and potentially depressurisation / venting activities. Heating will only be required during situations when significant pressure drops are taken across the topsides choke valve e.g. for normal dense phase operation. Heating will be required to avoid compromising system design temperatures but also protect the reservoir from being damaged by very cold CO2. It is not anticipated that heating will normally be required for gaseous phase operation when the pressure drop across the topsides choke should be small or minimal. Heating may also be required for depressurisation/venting activities to aid CO2 dispersion, to prevent solids formation in the vent system and avoid a visible plume of CO2 snow being discharged. However, the requirement to provide vent heating needs to be reviewed further; it is only an assumption that it is required at this stage. Refer to the Pressure Let-down System Design Philosophy, Doc. No. KCP-GNS-PCD-DPR-0004 for further details on venting requirements S3.


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1.3.2 Heating Facilities Proposed

1.3.2.1 Gaseous Phase Demonstration Phase

It is anticipated that heating will only be required during the gaseous phase of operation for system/wells start-ups or for allowing reduced flow of CO2 into individual wells. The peak total heating duty, which needs to be confirmed, is anticipated to be approximately 2 MW. The only feasible approach to adding heat to the CO2 in this mode of operation would be by separate electrical heaters on each well. This is due to the following reasons:-

Due to the complicated nature and unreliability of fired heaters, then the use of a fired heater on the offshore facility would require personnel to be permanently based offshore. An electrical heater is simpler, much easier to start remotely and is much better suited to a normally unmanned facility.

Multiple heaters would be required to ensure that adequate system availability is maintained. In addition, individual wells may require separate heating due to varying conditions in that particular injection string. A separate heater on each well would meet all of the availability and flexibility requirements for the system.

A fired heater would require additional hydrocarbons to either be stored on the facility (diesel), or piped in (fuel gas). The offshore safety risks for this these alternatives are much greater than for an electrically heated option.

A separate heater may also be required on the vent system. However, use of the process heaters for this duty maybe feasible and will need to be investigated. Figure 1-1 provides the proposed flowscheme for the electrically heated gaseous phase mode of operation. It should be noted that the flowschemes in this philosophy are intended to be used to show the configuration, number and type of the heaters only, and that some features, such as the position of the meters, may change.


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Figure 1-1 Gaseous Phase Case - Offshore Process Infrastructure


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1.3.2.2 Dense Phase Full Flow Case

In order to accommodate the heating scenarios identified in the previous sections, the following heating equipment and configuration may be required for the dense phase mode of operation (See Figures 1-2 and 1-3 below). It should be noted that the final topsides configuration and means of supplying heat to the CO2 needs to be confirmed. The options utilizing seawater as the heating medium were evaluated in two separate decision papers S4 and S5, which were completed in a previous phase of the project. These decision papers recommended that the seawater heating options are to be discounted from further evaluation. Two design options that are to be considered further are presented below. 1. Single Fired (Direct or Indirect) or Single Electric Heater Scheme (Fig 1-2) A fired heater or electric heater will be utilised upstream of the topsides choke valve to raise the injection temperature to the required value. The fired heating system maybe direct fired or indirect. The indirect system would use a fired heater to warm up a separate closed loop heating medium system. A fired / electric heater is also allowed for on the vent line.


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Figure 1-2 : Proposed Offshore Infrastructure with Fired Heater1

1 Proposed Infrastructure taken from ITT submission D172 and shows a fired heater and

depressurisation heater and a riser base ESDV. The actual system layout maybe different from this when the final offshore flowscheme is developed.


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1. Electrical Heating on Each Individual Well (Fig 1-3)

This system is effectively an expansion upon the scheme that is proposed to be used for the gaseous phase of operation. This option utilizes an electrical heater on each well flowline upstream of each choke valve. An electric heater is also allowed for on the vent line.


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Figure 1-3 Full Flow Case With Separate Heaters on Each Flowline


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1.3.3 Heat Transfer Equipment

The final heating scheme and majority of components within the heating system and their type are still to be confirmed. The following components should be considered when selecting the final design: 1. Fired Heater A directly fired heat exchanger may be able to be installed. However there could be concerns regarding corrosion on the external bundle walls caused by the cold CO2 being carried in the tubes. If a directly fired heat exchanger becomes unattractive then a system incorporating an intermediate heating medium system could be installed. This system could include circulation pumps, expansion and storage tanks, filters, associated piping, valves and instrumentation. An appropriate heating medium would need to be selected. 2. Electric Heater An electric heater could be an alternative to a directly fired heater. Using this system would also remove a lot of HSE issues associated with having a hydrocarbon fired heater installed on the platform. It should be noted that significantly sized thyristor panels would also need to be provided for with this option (i.e. a larger electrical scope associated with this option).

Another significant attraction about this type of heater is its ability to be used on an Normally Unmanned Installation, due to its inherent simplicity and reliability.


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1.4 Quantification of Heating Duties

1.4.1 Injection Heating Duties

The amount of heating required will depend on the flow scheme option selected, reservoir pressure and CO2 flowrate. Figure 1-4 details the estimated steady state heating duties required for the full power plant capacity of 1600 MWg2. The figure shows the fired / electric heater duty required to ensure single phase flow down the injection wellbore. It also details the seawater heater duty to ensure fluids entering the well bore are at 0C. The heating duties assume normal operation of the system in dense phase mode, gas phase heating will not require be required except for start-up. The use of seawater as the heating medium has since been discounted from further consideration, but this data is purely provided for information only.

Figure 1-4 : Estimated Field Life Injection Duties for Steady State Dense Phase Operation and the full 1600 MWg Power Plant Capacity

0

2

4

6

8

10

12

14

16

18

20

0 20 40 60 80 100 120 140 160 180

Du

ty (

MW

)

Reservoir Pressure (bar)

Steady State Injection Heating at Offshore for a Power Plant Capacity of 1600 MWg (Dense Phase Operating Cases)

Fired Heater Sea Water Heater

2 For alternative power plant capacities the heating duty can be pro-rated to

estimate the required heating duty.


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1.4.2 Vent Heating Duties

The requirement to install a vent heater will need to be decided when dispersion studies have been investigated. If it is required the heating duties will need to be determined based upon the worst case depressurisation rates and the amount of heating to ensure the required dispersion is achieved.

1.5 Requirement for New Facilities / Further Work

The need for further modeling to establish the behavior of high pressure CO2 depressurisation to atmosphere needs to be performed to determine if a vent line heat exchanger is required or not. The preferred flow scheme and means of supplying heat offshore needs to be determined (i.e. fired direct, fired with heating medium, electric etc). Whether capacity upgrades in the future are likely. This will need to be known so that sufficient platform space is allowed for in the design for future expansion of the heating system (e.g. Thames Cluster).


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2. Assumptions

1. The offshore facility will be a Normally Unmanned Installation (NUI), if at all possible. 2. The heating system will initially be designed to handle the CO2

flow for the demonstration case (6600 tonnes/day), which is of the full CO2 flow from the 1600 MWg power plant. Heating duties are presented in this philosophy for the full power plant capacity (1600 MWg). The heating duties for lower power plant outputs, during dense phase operation, should use the data from the 1600 MWg case and prorate them accordingly.

3. It is assumed for the full flow scheme that the preferred heating arrangement and means of providing heating energy offshore will be determined in the next stage of design. 4. A vent heater has been assumed to aid CO2 dispersion and avoid a visible plume of CO2 snow. The requirement for this equipment item needs to be checked through dispersion studies etc. 5. In order to avoid the requirement for high integrity low temperature trip systems, then systems that are downstream of the heater will be designed to cope with short term exposure to very low temperatures (minus 78 deg C). This event could occur in the event of heater failure.

6. The use of a local reservoir as the fuel gas source has been discounted for the fired heater option. This is due to the fact that the additional fuel gas treatment facilities would be required, and the fact that it is extremely unlikely that the source of fuel gas would be available for the 40 year design life.


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3. Design Requirements

3.1 Heat Loads

The heating loads detailed in Figure 1-4 should be taken as indicative values for dense phase operation of the injection system taking all the CO2 from a 1600 MWg power plant. Any start-up duties / partial fired heater duties will need to be confirmed at the next stage of design when the flow scheme and means of providing heat have been selected. Sufficient platform space should be allowed for future expansion of the injection system.

3.2 Temperature

The design temperatures of the heating system are to be confirmed at a later stage of design, once the flow scheme and means of providing heat has been agreed. However, it should be noted that items subjected to CO2 downstream of a choke valve could see temperatures as low as -78C (assuming no upstream heating). To guarantee a single phase fluid downstream of the choke valve (during dense phase operations), the CO2 fluids need be heated to ensure the temperature downstream of the choke is above the critical temperature of CO2, which is circa 32C. The heater outlet temperature will be dictated by the pressure upstream and downstream of the choke. It should be noted that heating during the gaseous phase operation should not normally be required.

3.3 Pressure

The design pressures of the heating system are to be confirmed at a later stage of design, once the flow scheme and means of providing heat has been agreed. The maximum pressure will partly be determined by the need for line packing of the flowline (to act as CO2 storage) and could exceed 200 barg.


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3.4 Physical Properties

The physical properties of the heating medium will be advised at a later stage of design, if this option is selected at the next stage of design.

3.5 Materials of Construction

Reference should be made to the Materials Selection Report For Offshore Infrastructure Phase 1A, Doc. No. KCP-GNS-PLD-REP-0009. Appropriate materials of construction should be selected. These will depend on what flow scheme and the means of heating selected. It should be noted that care must be taken when selecting elastomers in contact with CO2, due to the potential for the adsorption of high pressure CO2 into components. It is therefore recommended that extensive testing takes place of any selected elastomers that could come into contact with pressurized CO2.

3.6 Insulation

Depending on the heating option selected at the next stage of design personnel protection and or heat conservation insulation may be required on the heating system.

3.7 Equipment Isolation / Protection

Suitable equipment isolation and over pressure protection etc will need to be provided for depending on the heating solution selected.

3.8 Process Control

The heating system on the offshore installation shall be designed to be self regulating. The control philosophy will be to provide sufficient heat to the CO2 such that it can be injected / vented at the correct temperature. Given that the offshore installation will be largely unmanned, the system should have the ability to be started / stopped remotely. This will be considerably easier in the case of the electric heater. The performance of the system will require to be monitored by onshore operators.


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4. Mandatory References

M1 ASME Boiler and Pressure Vessel Code: Rules for Construction of

Pressure Vessels ASME VIII. To be developed further when heating solution selected.

5. Supporting References

S1 Internal Report. S2 Intrernal Report. S3 Pressure Let-down System Design Philosophy Doc. No. KCP-GNS-PCD-DPR-0004 Rev 01. S4 Internal Report. S5 Internal Report. S6 Power Supply Design Philosophy, Doc. No. KCP-GNS-PSP-DPR-0001 Rev 01.

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