LIST OF FIGURES AND DRAWINGS Air Emissions from 175,000 BPSD Crude Unit Heaters Firing Fuel Gas Air Emissions from 175,000 BPSD Crude Unit Atmospheric Cnide Heater Firing 1 wt% Sulfur F
Basisofstudy
The Pollution Prevention Task Force (PPTF) of the American Petroleum Institute
(NI) has developed the following working definition of pollution prevention:
Pollution prevention is a comprehensive approach aimed at minimizing or eliminating the release of pollutants into air, water, and land This strategy encompasses the creation of environmentally friendly products, modifications in processes and practices, source reduction, beneficial reuse, and sustainable recycling methods.
The PPTF and the API Committee on Refinery Environmental Control (CREC) emphasize the need for effective pollution prevention strategies in refineries This study aims to explore design modifications for the crude unit in a typical refinery to reduce multi-media environmental releases while maintaining its traditional operational efficiency.
This report outlines the study's findings and aims to be a valuable reference for refinery designers in the initial design phase of constructing a new crude unit or upgrading an existing one.
A generic methodology for conducting pollution prevention studies on process units was developed and applied to the refinery crude unit This approach considered pollution prevention from two distinct perspectives.
The design of a model new crude unit
The revamp of a conventional existing crude unit, applying the principles leamed in Case 1
A typical ten-year-old U.S Gulf Coast crude unit of 175,000 BPSD capacity was chosen to serve as the reference point or Base Case
This report encompasses essential technical details such as crude charge and product slates, process flow diagrams, major equipment lists, and the utilization of raw materials, water, and energy Additionally, it outlines equipment costs and multi-media releases, which consist of point source air emissions, fugitive air emissions, solid and hazardous waste production, and wastewater inventory.
The study explored various pollution prevention methods, including modifying vacuum towers for dry operation and reducing flash zone pressure to minimize feed cracking It also examined the implementation of dry operations to decrease sour condensate production and the use of vacuum pumps to partially replace steam jet ejectors for vacuum generation Additionally, the research highlighted the benefits of using reboiled sidestrippers on atmospheric towers instead of open steam stripping to lower sour condensate levels The replacement of first-generation low NOₓ burners with advanced low NOₓ burners in furnaces was also investigated, along with the application of catalytic and non-catalytic processes for selective NOₓ reduction Finally, the study emphasized the reuse of stripped sour water as a substitute for clean process water in desalting operations.
A P I P U B L * 3 L L 93 0 7 3 2 2 9 0 05LL233 667 = heat integration for maximum energy utilization (commonly referred to as pinch analysis).
Limitations of Study Results
This study evaluates various pollution prevention concepts without suggesting a definitive "best" design While it provides a comprehensive overview within the time constraints, there are likely additional measures applicable to crude units Each refiner must assess their specific requirements and consider the most suitable ideas The techniques and concepts presented can serve as a foundational resource for corporate planning, engineering, regulatory, and operations teams to conduct a detailed, case-by-case evaluation of pollution prevention strategies for crude units at their refineries.
For a model new crude unit (Case l), the following pollution prevention ideas may be considered in the design stage and are reported in Section 6:
Pollution Prevention Ideas for Model New Crude Unit
Apply pinch analysis to the crude preheat train heat integration (refer to Appendix I) Increase crude preheat temperature and minimize heat losses to air and cooling water
Increase crude distillation column pumparounds from two to four Reboil sidestrippers with a heat transfer oil rather than by steam stripping
Lower vacuum column flash zone pressure from 35 to 20 mmHgabs This will lower furnace fired duty and reduce cracking of the feed to lighter products and wet oivrecovered oil
Use a liquid ring vacuum pump in place of the third stage steam jet ejector on the vacuum tower overhead
Strip desalter brine for benzene removal before sending brine to wastewater treatment Send recovered benzene to gasoline blending
Install new generation low NO, burners Use selective catalytic reduction (SCR) to reduce NO, in furnace flue gas
Scrub furnace flue gas for removal of SO, when f d n g high sulfur fuel oil
Optimize water reuse by application of sidestream softening to blowdown streams
Implement advanced process control techniques to enhance energy efficiency, while integrating analyzers for continuous monitoring of pollutants Utilize specialized hardware along with inspection and maintenance (I&M) practices to effectively eliminate fugitive emissions of volatile organic compounds (VOCs).
- Select leakless or graphite packed valves
- Use sealless design pumps or pumps with double seals
- Minimize flanges and install sealing rings on leaking flanges
Blind, plug, or cap open-ended vent and drain valves
- Route relief valves to flare and add rupture disks
- Pipe compressor seal vents back to process and vent compressor distance pieces to refinery flare
- Install a maintenance drain-out (MDO) system to eliminate open discharges from drains
- Totally close-loop all samplers
1.4 Pollution Prevention Ideas for Revamp of Conventional Crude Unit
For the revamp of an existing conventional crude unit (Case 2), the following pollution prevention ideas may be considered and are reported in Section 7:
Apply pinch analysis to the crude preheat train heat integration
Increase crude preheat temperature and minimize heat losses to air and cooling water Keep equipment and piping relocation to a manageable minimum
Reboil the atmospheric column sidestrippers using heat transfer oil instead of steam stripping, excluding the high boiling point Atmospheric Gas Oil Additionally, install two new sidestrippers and modify one existing sidestripper.
Reduce the vacuum column flash zone pressure from 35 to 20 mmHg absolute by replacing the third stage steam jet ejector with a liquid ring vacuum pump on the vacuum tower overhead Additionally, incorporate parallel ejectors in the first and second stages to enhance efficiency.
Strip desalter brine for benzene removal
Upgrade to advanced low NOx burners and implement SCR systems for effective post-combustion NOx reduction Additionally, scrub flue gas to eliminate SOx emissions when using high sulfur fuel oil in heaters Enhance water reuse by applying sidestream softening to blowdown streams.
Apply advanced process control to optimize energy utilization Install analyzers to provide continuous pollutant monitoring
Employ specialized hardware and I&M to reduce fugitive emissions of VOC:
- Improve I&M program (leak definition, monitoring frequency, and repair response time)
Selectively retrofit leakless or graphite packed valves
Selectively retrofit sealless design pumps or pumps with double seals
Minimize flanges and install sealing rings on leaking flanges
Blind, plug, or cap open-ended vent and drain valves Route relief valves to flare and/or add rupture disks
- Pipe compressor seal vents back to process and vent compressor distance pieces to refinery flare
- Install a MDO system to eliminate open discharges from drains
- Totally close-loop all samplers
The findings regarding air emissions, wastewater effluents, solid wastes, energy consumption, and associated costs are concisely presented in Table 1.1 Additionally, Figures 1.1 to 1.4 provide visual representations of air emissions, wastewater loads, and the generation of solid waste.
The findings of this pollution prevention study on refinery crude units are summarized below:
A generic systematic methodology for conducting pollution prevention studies on process units can be applied to the crude unit in a typical refinery
There is a correlation between energy efficiency and environmental effectiveness: the more efficient the crude unit, the less it pollutes
The total energy usage in the crude unit can be reduced by improving heat integration in the crude preheat train through pinch analysis
Reductions in wastewater generation can be achieved by energy reduction and stream recycling
Water recycling and the prevention of mixing hazardous and non-hazardous waste streams are effective strategies for reducing solid and hazardous waste Additionally, using limestone scrubbing to reduce sulfur dioxide emissions from heaters that burn high sulfur fuel will produce non-hazardous sludge.
O NO, emissions can be reduced by new generation low NO, burners, SCR units, and Flue Gas Recirculation (FGR)
O The total annual benzene quantity (TAB) in wastewater can be reduced by steam stripping
Fugitive emissions from piping components can be reduced by hardware improvements and stringent inspection & maintenance programs
O O O O O O O O O O in O ln O ln O in O in t d c) m hl e4 r r
API has developed the following working definition of pollution prevention:
Pollution prevention is a comprehensive approach aimed at minimizing or eliminating the release of pollutants into air, water, and land This strategy encompasses the creation of environmentally friendly products, modifications in processes and practices, source reduction, beneficial reuse, and sustainable recycling methods.
The API defines pollution prevention as excluding end-of-the-pipe treatment Based on this definition, the API Pollution Prevention/CR.EC Workgroup launched a study focused on pollution prevention in crude units.
This study aimed to explore methods for a typical refinery's crude unit to reduce multi-media releases while maintaining its traditional operational efficiency It emphasized the importance of integrating both pollution prevention strategies and end-of-pipe treatment methods in line with sound engineering practices.
This study examines pollution prevention through two approaches: the design of a new crude unit (Case 1) and the renovation of an existing conventional crude unit (Case 2).
To serve as a reference point or Base Case, a typical ten-year-old U.S Gulf Coast crude unit of
175,000 BPSD feed rate was chosen
This study presents a technical evaluation of alternative pollution prevention strategies for refinery crude units, detailing their integration into new or revamped facilities Additionally, it introduces a systematic methodology for analyzing pollution prevention, which can be applied to assess various refinery processes and specific pollution prevention initiatives.
This study has limitations and should not be viewed as a definitive recommendation for crude unit process design, as it only examines a single type of crude and a specific set of product specifications A comprehensive design basis for a crude unit typically involves evaluating multiple feedstocks and a variety of product specifications.
This study does not suggest a single optimal design for pollution prevention; instead, it evaluates various concepts that can be applied to crude units Each refinery must assess its specific requirements and select the ideas that best suit its unique situation The techniques and concepts developed in this study serve as a foundational resource for corporate planning, engineering, regulatory, and operations teams, facilitating a more detailed, case-by-case evaluation of pollution prevention strategies at individual refineries.
There is a significant distinction between conceptual studies and the practical implementation of pollution prevention systems Many promising ideas for individual refineries require laboratory studies or field demonstrations prior to project execution.