Tesoro Hawaii Corporation Refinery - Executive Summary
TESORO HAWAII CORPORATION REFINERY RISK MANAGEMENT PLAN |
The following company wide policy statement best expresses Tesoro's overall commitment to safety.
Tesoro Petroleum Corporation considers safety an integral part of its performance. At Tesoro we believe:
7 All accidents can be prevented.
7 Safety is not to be compromised for any reason.
7 Each employee is responsible for their own safety and working safely is a condition of employment.
7 Line management from the president through the first line supervisor is accountable for accident prevention.
7 Trained employees are an essential element for safe workplaces.
7 All operating exposures can be safeguarded.
7 Immediate corrective action shall be taken on all unsafe practices and incidents with injury or damage potential.
Refinery Process Description
The Tesoro Hawaii Corporation operates a petroleum refinery in Campbell Industrial Park, processing 95,000 barrels per day of crude oil to produce
products such as jet fuel, gasoline, asphalt, fuel oil and propane; with the processes optimized around the production of jet fuel. No petrochemicals are produced. Following is a description of the refining processes that are used.
Crude Distillation: The crude oil is washed to remove salt and then heated and distilled into components such as naphtha, kerosene, diesel, atmospheric gas oils (middle distillates), and residual oil in an atmospheric distillation tower (CDU). The heavier oils from the atmospheric column are further processed by vacuum distillation (VDU). The RMP does not address the VDU as a separate process since it does not contain 10,000 pounds of a covered flammable mixture. However, the VDU was included in the CDU HAZOP and is included as an integral part of Tesoro's safety program. The naphtha and other light ends coming off the top of the atmospheric tower are covered by the RMP as a flammable mixture. The hazards associated with the CDU include high temper
ature and pressure of the hydrocarbons, and chemicals such as caustic used to treat the kerosene. The CDU also contains the sour water stripper (SWS). The sour water stripper uses steam to strip ammonia (NH3) and hydrogen sulfide (H2S) from water containing ammonium hydrosulfide. The H2S and NH3 are sent to the Sulfur Recovery Units discussed below. In 1997, a SWS feed tank was installed in the SWS feed system to prevent upsets from carryover of hydrocarbons to the sulfur recovery units. This has resulted in a safer operation.
Visbreaking: The heavy residual oils from the bottom of the VDU tower are processed in the visbreaker (VBK) by viscosity breaking at high temperature. This results in breakdown of the heavy oil to produce fuel gas, naphtha and lighter oils. The hazards associated with this process are again high temperature and pressure of the hydrocarbons, gases containing ~10% H2S, and chemicals such as potassium hydroxide (KOH) used to neutralize the H2S.
Manufacturing Unit: The AMU takes heavy residual oils and produces asphalt by blowing with air. The unit does not contain 10,000 pounds of a covered flammable mixture and is not regulated under the RMP. The unit is however covered under our PSM program and has had a HAZOP done. The potential exists to form an explosive mixture in the oxidizer and mitigative steps have been taken to prevent this from occurring.
Distillate Hydrocracker: In the hydrocracker (DHC), gas oils from the CDU and VDU are mixed with hydrogen and sent to a series of catalytic reactors where nitrogen and sulfur are removed and the oils are cracked and reacted with hydrogen to form diesel, kerosene, naphtha and lighter gaseous products. Some of the reactions in these reactors are exothermic and the potential exists for a runaway reaction. Process controls minimize this possibility and provide for rapid pressure reduction by dumping the reactors to the flare to protect against accidents. Following the reacto
rs, vapor-liquid separation and hydrogen recovery occur. The liquid is then reheated before going to a fractionation tower for diesel, kerosene and naphtha separation. Additional hazards include H2S and NH3 up to 5% in some gaseous streams, high temperature and pressure of the hydrocarbons, and flammable mixtures.
Amine Treatment Unit: In the ATU, H2S in gaseous and liquid petroleum (LPG) hydrocarbon streams is absorbed in methyldiethanolamine (MDEA). The rich MDEA is then stripped by heating to produce a 90+% H2S stream that is sent to the sulfur recovery unit. Although the amount of H2S never approaches 10,000 pounds, and therefore the unit is not covered by the RMP, Tesoro considers the H2S to present a significant risk, and treats it accordingly. H2S ambient monitors are strategically placed to pick up any leak. This process unit also includes the LPG Merox Unit where mercaptans are removed with caustic (NaOH). Large amounts of LPG are present in this unit in addition to
the normal hazards of high temperature and pressure.
Sulfur Recovery Units: Although the SRUs are not covered by the RMP (neither H2S or SO2 approaches 10,000 pounds), the potential for an H2S or SO2 release is a major concern. Because of stack releases that occurred in 1995, the refinery has made many upgrades in these units to enable safer and more flexible operation and thereby limit unit shutdowns or upsets. In the SRU, 1/3 of the H2S is burned to SO2, which then reacts with the remaining H2S to form sulfur. The sulfur is condensed, prilled and sold. The unit also includes the Shell Claus Offgas Treater (SCOT) unit which reduces excess SO2 from the SRU over a catalyst and absorbs it in MDEA. The amine is stripped of H2S, which is the recycled back to the SRU.
Light Ends Recovery Unit: The LERU is a collection of four fractionating columns designed to separate and purify the lighter products for sale or reuse. Methane and ethane are used as fuel gas, butane and isopent
ane are used for gasoline blending, and propane is sold separately. There are no heaters in this unit. The unit contains large amounts of light flammable hydrocarbons in addition to the hazards of high temperature and pressure.
Catalytic Reforming Unit: This unit includes the naphtha hydrotreater (NHT) where sulfur and nitrogen are removed from the naphtha using hydrogen at high temperature and pressure. The sulfur must be removed to prevent poisoning of the catalyst in the reformer (CRU). The reformer consists of a series of reactors using platinum catalysts to reform naphtha into reformate with increased aromatics and higher octane for gasoline blending. Hazards in this unit, in addition to flammable mixtures, include exothermic reactions, high temperature and pressure, H2S and hydrogen. The hydrogen generated in the CRU is used in the DHC.
Hydrogen Generating Unit: A hydrogen plant produces hydrogen that is used primarily in the hydrocracker. The hydrogen is produced
by reacting steam with light hydrocarbons in the presence of a catalyst. In addition to the potential for combustion of the hydrogen and hydrocarbons, the methanation reaction to remove small amounts of CO and CO2 is highly exothermic and presents the possibility of a runaway reaction. The HGU does not contain 10,000 pounds of a flammable mixture, so it is not covered by the RMP; however, like the rest of the refinery, it does present risks and is an integral part of our PSM program. As with all refinery processes, the process hazards such as high temperature and pressure, are mitigated by process controls.
Cogeneration Unit: The CGU consists of a combustion turbine power generating unit combined with a waste heat boiler to produce steam. The CGU burns light reformate as fuel, and the hazard is mainly due to the possibility of a fire or explosion from one of the storage bullets associated with this unit which are located adjacent to a public road. Both our worst case release and
our highest impact alternative release scenario assumes butane is stored in one of these bullets. Note that all of the bullets are protected with deluge systems.
Wastewater Treatment Unit: The wastewater treatment unit (WTU) separates oil from oily wastewater and also strips dissolved hydrocarbons from the wastewater. Liquid hydrocarbons are stored in a recovered oil tank and recycled back into the process. Stripped hydrocarbons are burned in a thermal oxidizer to prevent air pollution. This process is considered a covered process because of the possibility that light product might be stored in the recovered oil tank. This has never been the case, and is considered highly unlikely. Therefore, this process presents only a minimal possibility of a fire.
Tank Farm: The tankfarm (TKF) contains many petroleum storage tanks, since Hawaii is isolated and must maintain a large inventory. Stored products include crude oil, fuel oils, diesel, kerosene, gasoline, naphtha, isopentane,
butane and propane. The isopentane, butane and propane is stored in pressurized tanks which have deluge systems in case of fire. All tanks are diked to contain releases. Foam is also available for tank fires.
Flare System: The flare system consists of the various flare headers throughout the process areas and two knockout drums. The flare system transports gases from pressure safety relief valves to the flare for safe combustion. The drums have the potential for fire or explosion but it is unlikely since it is designed as an emergency relief system.
Release Scenarios (Worst Case and Alternatives)
Under the RMP regulations, if any refinery process stores toxic or flammable chemicals above EPA's threshold quantities, the refinery must determine the worst case accidental release (defined as the release resulting in the greatest downwind impact) for that chemical. While EPA strictly defines the worst case scenario that must be used, alternative cases that may be more like
ly to occur may be presented, and are more likely to be the subject of HAZOPs and drills.
Toxic Substances: Toxic substances generated as a by-product of refining processes include Hydrogen Sulfide (H2S), Ammonia (NH4), and Sulfur Dioxide (SO2). These gases are not stored or found in the process above the RMP regulatory threshold level of 10,000 pounds. Therefore they are not addressed in this plan. However, they have been fully addressed throughout our safety program and potential release scenarios have been analyzed and mitigation measures taken. Tesoro Hawaii is an active member of the Campbell Local Emergency Action Network (CLEAN), and potential worst case and alternative releases of the chemicals listed above are given in the CLEAN Emergency Management Plan for Campbell Industrial Park. Those release scenarios show that the potential for off-site impacts exists for both H2S and SO2. Means to prevent and mitigate impacts from these releases is addressed in Tesoro's PSM
program and Emergency Response Plan.
Flammable Mixtures: The refining industry produces flammable mixtures as part of its main business and therefore has a significant potential for explosion and fire. For this reason, the industry goes to great length to prevent accidents that could cause a fire or explosion. The Tesoro refinery was built in 1972 and has not had a fire or explosion with significant off-site impacts. Nevertheless, refinery explosions and fires do happen, and the potential exists for off-site consequences. The worst case scenario would involve one of our cogeneration plant bullets assumed to be storing butane. EPA rules assumes the entire contents of the bullet is released as a gas over a 10 minute period and is then involved in a vapor cloud explosion. EPA guidance was used to calculate the endpoint (impact distance) of 0.38 miles. Similar releases from other bullets had larger areas of impacts, but because of their locations, they had smaller offsite impacts.
Note that this bullet has a deluge system on it to mitigate the effects of a fire. The vessel is also isolated and inspected and tested according to industry standards to prevent failure. The alternative case given is for a two inch hole or line failure from the same bullet. This was chosen because of its proximity to a public road. This case would release 3,600 lb/min of butane. The entire contents would be released in 30 minutes. EPA guidance suggests this would have impacts (up to the LEL of 1.5%) of < 0.06 miles; however modeling suggested it could reach 0.09 miles. It should be noted that the CLEAN publication shows larger impact areas because the calculations were based on more conservative, and theoreticly impossible, EPA assumptions which have since been changed.
Accidental Release Prevention Program
Tesoro Hawaii has an extensive Process Safety Management (PSM) Program designed to minimize or eliminate incidents that might result in injury to its employees, the neig
hboring public, or the environment. The PSM program includes the entire refinery, and is not limited to processes that contain a threshold quantity of a regulated chemical. Hazard and Operability Studies (HAZOPS) are completed by professionals on all refinery processes and repeated every five years as a minimum. This assures that design standards are adequate for safe operations, and that controls are installed and address all identified hazards. Note that the great majority of actions identified in the HAZOP are addressed as quickly as practicable. Some items however require long lead times due to design requirements or other work necessary to determine a solution. Management of Change (MOC) procedures and Pre-Startup Safety Reviews (PSSRs) ensure that any change in materials, equipment or procedures is thoroughly reviewed for safety and risk. A mechanical integrity program ensures that equipment is maintained, inspected and tested using manufacturers and industry standards. Ac
cidents and near misses are subject to an incident investigation process that ensures actions are taken to prevent similar incidents in the future.
This RMP submittal asks for a number of dates to show compliance with various elements of the prevention program. We have tried to provide the latest dates; however, the program is dynamic and many dates will have changed as we continuously change and update our program. Computer programs track actions, recommendations and resolutions to completion for the HAZOPs, MOCs, PSSRs, incident investigations and the mechanical integrity program.
The refinery has not experienced a fire, explosion or other incident involving a flammable mixture that has generated any off-site consequences within the last five years. In fact, as indicated above, there has not been a fire with offsite consequences since the refinery was built in 1972. We did however experience two releases of SO2, probably mixed with small amounts of H2S and fr
ee sulfur in November and December 1995. These releases caused eye irritation and breathing difficulties for nearby off-site workers. These stack releases resulted from the malfunction of our sulfur recovery units (SRUs) during a period of unfavorable meteorological conditions. The refinery has since spent approximately six million dollars to upgrade the SRUs so that the likelihood of this happening again is greatly reduced. Note that the figure given for 6.10(d), off-site evacuations, is an estimate. Tesoro does not have a count of those who were asked to evacuate Campbell Industrial Park or prevented from entering.
Emergency Response Program
Our emergency response program is designed around the Incident Command System (ICS) and is used for all types of emergencies. Training and drills are held routinely to test response, communication, coordination and training. Drills range from routine un-announced checks of the call in system to scheduled all day drills involving other Tes
oro locations and response agencies. The refinery maintains a well-trained Fire Brigade with a full range of response equipment.
The refinery routinely makes changes to procedures, equipment, training programs and materials in order to improve safety and reduce environmental impacts. These changes are made as a result of HAZOP studies, accident and near-miss investigations, safety inspections, pre-startup reviews and audits. The refinery is currently developing a behavior based program to improve safety awareness of all employees. Throughout the refinery safety programs, a key objective is continuous improvement through involvement at all employee levels.