Efficient use of energy has both economic and environmental benefits. For industries, while it lowers production costs and raises productivity, it also reduces emissions of various pollutants, including GHGs like CO₂. As an economic factor, the cost of CO₂ emissions changes the calculation of the value of energy efficiency improvements, and so it may provide viability for energy-saving projects that otherwise would not be economical. Regardless of the cost of CO₂ emissions (as determined by government regulations and/or market forces), projects that improve refinery energy efficiency can provide a positive return on investment in the current economy.

Our 2007 Report on Energy Management (titled "Future Refinery Operations to Meet Fuel Supply Security and Environmental Requirements") provides details on opportunities and means for refiners to improve energy efficiency. Coverage of energy efficiency in the present Report, however, is in terms of reducing the use of energy sourced by the combustion of fossil fuels. Specifically, this report focuses on energy and fuel savings in refining operations and provides quantitative estimates translating energy savings into CO₂ emissions reductions.

For refiners, energy matters should be viewed from two alternative perspectives to ensure a comprehensive improvement approach. Considering strategies to optimize both the supply side and the demand side of refinery energy usage will provide refiners with the opportunity to maximize the benefits of an energy-saving project. Supply-side energy efficiency focuses on improving the efficiency of utility generation to ultimately lower the necessary input of natural gas, petcoke, coal, fuel oil, or fuel gas to meet plant demands. The demand side of energy efficiency—which will be discussed later and organized by processing unit—involves reducing the energy consumption of each process in the plant on a per-barrel-of-throughput (or product) basis.

Due to the impending implementation of carbon cap and trade systems, investment in energy savings on both the supply and demand sides must now include a factor accounting for the cost of carbon emissions. This Report will translate the benefits from (1) improving energy supply efficiency and (2) lowering overall energy demand into economic savings and actual CO₂ reductions.

Supply Side

Utility generation to meet refinery requirements is one of the largest consumers of energy in the plant, accounting for around 40% of a refinery's total operating costs, and utility management techniques can be applied to steam, heat, and electric power systems in a refinery with varying investment requirements and benefits. According to the US Dept. of Energy's 2002 Manufacturing Energy Consumption Survey (MECS), 1.717 quad of the energy distributed to conversion units went to fired heaters, 0.017 quad was for process cooling, and 0.178 was for driving machinery like pumps, compressors, mixers, etc. Also, 0.672 quad was sent directly to processing units as steam. It is clear that the single greatest demand for energy in the refinery comes from fired heaters, with steam in second place. The survey indicates that the losses in energy before reaching the processing units was 31.5% of the total supplied, or 0.976 quad. If energy management could save 10% of that, or about 0.1 quad, then this could reduce CO₂ emissions by 5-10MM mt/y, depending on the overall mix of fuels. This reduction is about 2?4% of the total emissions in 2002. Specific opportunities for savings in the supply, transmission, and conversion of energy along with corresponding reductions in CO₂ emissions are discussed in this Report.

Power, steam, and heat consumption in refineries represents a massive portion of overall plant energy demands. With increasing overall crude throughput, more stringent product specifications (e.g., sulfur), and the processing of heavier crudes, the consumption of both electricity and steam has been increasing over the past several decades.

The first step in supply-side energy management is to evaluate the plant's total utility demand. Electricity requirements to drive pumps, compressors, motors, fans, cooling systems, lighting, etc. for the average refinery approach 8% of the total energy demand, versus approximately 30% for steam. The average refinery's heat consumption rate ranges between 330K Btu/bbl and 550K Btu/bbl. Once plant demands are determined, the focus of supply-side energy efficiency is to improve the overall efficiency of utility generation to meet energy demands with a lower combustion fuel input.

The combustion efficiency improvements identified in this Report, along with the installation of efficient cogeneration units, can help refiners improve energy management in steam, heat, and power generation.

Power, Heat, and Steam Supply via Cogeneration (or CHP)

For separate generation of electricity, steam, and heat, the achievable efficiency of each process is limited by the best available technology. For power generation, average efficiency is usually in the range of 30-45%; state-of-the-art steam boilers provide approximately 80% efficiency; and the efficiency for the average furnace installed in a refinery is estimated at 70-82%. To add to this, many refiners are operating older units that were designed below current state-of-the-art efficiency ratings and/or operating units that have decreased in efficiency due to natural occurrences related to service time (i.e., fouling). Combined heat and power generation efficiency can approach 80%, resulting in an overall efficiency improvement of 27% compared to generating the utilities separately. A limiting factor for refiners, however, may be the sourcing of utilities. If a particular refinery traditionally imports electricity, then the installation of cogeneration technology may not be as attractive as it would be to a refiner that generates all utilities onsite.

The basic need for clean, cost-effective, efficient power is present in every refinery operation throughout the world. However, oil refiners have traditionally been skeptical about constructing power plants onsite due to their limited electricity requirements (usually about 60 MW for a stand-alone refinery) and the capital intensity of such projects. Besides the legislative requirements of capping CO₂ emissions, the recent trend toward liberalization of the electricity market (particularly in the EU) combined with an increasing need to dispose of refinery waste streams has led many to reconsider their options. Combined heat and power (CHP), or cogeneration (cogen), has emerged as an efficient way to meet increasing energy demands while maintaining superior environmental performance. In 2002, it was estimated that 26% of electric power consumed by refineries was generated by onsite cogen operations. Traditional CHP methods primarily include gas turbines, reciprocating engines, microturbines, combined boiler/steam turbine configurations, and combined-cycle implementations.

Despite these factors, CHP installations have decreased in recent years; however, the contemporary trend to cap emissions (CO₂, NO_X, etc.) has once again jump-started the research and development effort for cogeneration technology. Cogeneration is widely viewed as an effective option to improve efficiency and meet environmental standards in the future for large-scale industrial plants.

In the refining sector, the installation of CHP will largely depend on plant demands and the capabilities of each type of system. Reciprocating engines and microturbines are best suited for facilities requiring a significant amount of electricity, while the heat supplied may be limited to low-pressure steam or hot water. Alternatively, gas and steam turbines (and also combined-cycle implementations of the two) produce a significant amount of high-temperature exhaust that can be used to generate high-pressure steam or used directly for process heating in addition to the electricity supplied.

This Report will evaluate currently available CHP technologies to determine those most applicable to the refining industry in terms of efficiently meeting a refiner's heat and power demands. Additionally, a study of current and future R&D trends will provide an estimate of the emerging cogeneration technologies that may be of interest for refiners moving forward.

Other factors that may contribute to the value of these technologies include the polygeneration of additional utilities (e.g., hydrogen) and the ability of refiners to profitably export excess electricity, heat, hydrogen, and/or chemical feedstocks to other industrial, residential, and commercial consumers. The following table displays calculations for the efficiency of common CHP systems being fired on natural gas.

A survey of all US refinery-related CHP facilities was conducted based on both the fuel type and the prime mover. As can be seen in the following figure, combustion turbines (CT) made up the largest demographic with 34% of the CHP plants, while combined-cycle (CC) and boiler/steam turbine (B/ST) plants followed closely with 30% and 29%, respectively. The remaining 7% of US cogeneration plants utilized reciprocating engines (RE—3%) and microturbines (MT—1%) with information for the remaining 3% being unavailable.

Figure 1: Breakdown of Refinery-related CHP Facilities in the US

Refiners have already begun to invest in CHP technologies to take advantage of the improvement in energy efficiency with a strong ROI, and the implementation of carbon-cap-and-trade policies in many regions around the world will further improve the economics of such projects. Recent refinery cogeneration projects that are discussed in this Report include:

• ExxonMobil's 126-MW CHP at the company's Antwerp refinery in Belgium;
• Chevron's Richmond, California refinery in the US is planning a 43-MW CHP plant using a GE turbine;
• BP's Whiting, Indiana refinery in the US installed a 525-MW plant that cost about $210MM;
• StatoilHydro's Mongstad, Norway refinery is planning a 280-MW cogen plant to be started in 2010;
• Tesoro's Salt Lake City refinery in the US started up a 22-MW CHP project and has realized a simple payback period of 4.2 years.

Cogeneration using IGCC

In the refining sector, one emerging cogeneration option is Integrated Gasification Combined Cycle (IGCC). This technology capitalizes on both market trends and the constant drive to improve efficiency and integration within the refinery. Furthermore, hydrogen supply is considered to be an increasingly important issue in hydrocarbon processing. Many processing units throughout a typical oil refinery use large volumes of H₂, which can become a great financial burden. Refiners can take advantage of these situations by integrating large, efficient integrated gasification combined-cycle plants into their facilities to cheaply generate power and steam, as well as a significant supply of hydrogen gas.

Gasification converts a range of carbonaceous feedstocks into clean syngas for the production of hydrogen, steam, chemicals, and electricity. Currently, coal accounts for 49% of this feedstock, petroleum provides 37%, and the remaining 14% is provided by a combination of natural gas, petroleum coke (petcoke), and biomass/waste. In the next few years, the majority of new gasification projects will involve the use of coal as the primary feedstock. However, the processing of petroleum refinery residues, petcoke, and waste streams will have an added significance in a GHG-constrained world.

The syngas from a gasifier can be sent to a CO shift reactor for H₂ and chemicals production or be routed to combined-cycle turbines as part of an IGCC plant for power generation. IGCC is considered the most efficient conversion method to process solid feeds to yield electricity. Several IGCC operations are associated with refinery applications around the world to process low-value residues and petcoke for the production of power, steam, and H₂. The addition of an IGCC complex in an existing refinery also offers a more cost-effective approach to reducing emissions than other abatement technologies. The actual reductions that can be achieved include 40% of CO₂ emissions and 80% of SO_X, NO_X, CO, and particulate emissions. Additionally, interest in carbon capture and sequestration (e.g., for enhanced oil recovery in nearby, declining oil fields) is a key selling point for IGCC projects. High CO₂ concentration in gasification product streams provides needed economy of scale, and the benefits would be further magnified when combined with gasification of biomass in the future. Furthermore, recent US legislation included in the Energy Policy Act of 2005 authorized $1.65B for clean coal projects, including $800MM specifically for IGCC. The EPA also allotted $300MM in tax credits for gasification projects not directly associated with power generation. Government involvement in the development of gasification and clean coal processes will hasten the progress and availability of these breakthrough technologies. A number of refiners have already turned to IGCC technologies, and additional projects are in the planning, engineering, and construction phases:

• Valero's Delaware City (US) IGCC project was started up in 2002 and cogenerates the equivalent of 283.68 MWe of energy;
• Four refinery-related IGCC plants have been installed in Italy (Sannazzaro, Falcanora, Puertollano, and Priolo Gargallo) to cogenerate a total of 1,513 MWe of energy equivalent;
• Esso Singapore's Jurong Island refinery cogenerates the equivalent of 198.57 MWe via IGCC fed by refinery residuals;
• Furthermore, several IGCC plants remain in the planning stages in the US, fed by coal and/or petcoke and other refinery residuals.

This Report analyzes the growing importance of IGCC for CHP generation. IGCC can take advantage of a wide range of available feedstocks to efficiently and cleanly meet a refinery's utility needs.

Demand Side

Looking at the demand side of energy efficiency can also provide significant energy savings and reductions in CO₂ emissions for refiners on a per-barrel-of-throughput basis. Ultimately, management strategies that focus on more energy-efficient processing technologies for either new installations or revamps will reduce the fuel input required for the refinery and directly translate into reduced CO₂ emissions. Additionally, utilizing waste heat and reusing carbon-containing offgases for combustion will lower the amount of CO₂ being released into the atmosphere. Specific technology improvements that can be applied throughout the refinery will result in energy savings and CO₂ emissions reductions.

Utilities

Managing utility distribution systems (i.e., heat, steam, electricity, etc.) can provide opportunities to reduce the overall demand for these utilities. Substantial improvements relating to energy efficiency can be made to heat distribution systems. Heat is distributed throughout a refinery system through various Heat Exchanger Networks (HENs). Optimizing HENs as well as improving heat exchanger performance will increase energy savings. Additionally, energy savings can be realized through optimization of steam distribution. Some of the most intense steam-consuming processes include steam cracking, distillation, and process heating. The US DOE estimates that an energy savings of about 12% can be realized at most refineries from optimizing steam systems. PINCH analysis, which uses a systematic analysis of the first and second laws of thermodynamics, can be used to match sources and sinks for both heat and steam systems to improve the efficiency of the distribution systems and reduce the overall plant demand. PINCH analysis will be particularly useful for optimizing HENs in the refinery. Other energy-intensive units, such as furnaces, boilers, and refrigeration units, offer the opportunity to recover and redistribute heat to minimize fuel consumption. This Report further examines heat and steam systems and the impact that optimization of the distribution network through PINCH analysis and simple maintenance can have on the energy efficiency of the utility system.

In terms of energy sources, the vast majority of the energy for process heating comes from fuels, as discussed above. In contrast, more than half of cooling needs are met by electric power, and this is also the source for most of the energy required for operating machinery. This Report presents opportunities and new technologies that may be implemented in refineries to limit electricity losses during distribution to electricity-intensive processes and equipment.

Conventional refining requires a great deal of hydrogen, and furthermore, refinery hydrogen demand has been expanding at a rapid rate due to more stringent specifications for refined products. Many refiners view the H₂ production and distribution networks similar to a utility system, and therefore integration can be achieved through PINCH analysis. Improvements in energy efficiency during hydrogen production in steam reformers can lead to an increase in overall energy savings; however, these advances will be discussed in the section 'Strategic Application of Energy Efficiency Improvement in Refining Processes.' Hydrogen recovery is another way to save money on hydrogen production. Important factors in hydrogen recovery are cost and purity of the recovered H₂ streams. Current technologies include cryogenic distillation, pressure swing and thermal swing adsorption, and membranes. This Report offers strategies to manage refinery hydrogen distribution systems and improve H₂ recovery to reduce overall energy consumption and CO₂ emissions associated with H₂ use.

Process Hardware and Operations

To improve demand-side energy efficiency in processing units, refiners have many options relating to installed hardware and revamp opportunities and adjustments in process operations. Hardware advancements can be categorized into five general areas: heat transfer/recovery, separation, reaction vessels/metallurgy, auxiliary equipment (vacuum ejectors, pumps, valves, etc.), and catalyst considerations.

• Heat Transfer/Recovery. Heat transfer efficiency of heat exchangers will impact the refiner's ability to recover wasted heat from refinery processing units. Fouling and scaling of refinery heat exchangers effectively limits the efficiency of heat exchangers, and steps to avoid these occurrences are wide ranging. Some options for refiners include conducting maintenance activities, using chemical additives to reduce deposits, and implementing state-of-the-art technologies designed to limit fouling. Self-cleaning and zero-fouling heat exchangers are currently available and can significantly improve energy efficiency and lower CO₂ emissions. Alfa Laval recently announced that a planned replacement of older heat exchangers in a Russian refinery would result in an annual reduction in energy consumption of 340 MW, translating to an estimated CO₂ emissions reduction of 850K mt/y. Other minor improvements can be made to heat exchangers, such as installing tube inserts to improve turbulent flow, resulting in better heat transfer. Steam tracing techniques are also discussed in relation to refinery energy consumption and CO₂ emissions.
• Separation Techniques. Improving efficiency of separation in distillation and fractionation units will help to reduce the energy required for some of the more energy-intensive processes in the refinery. Improvements to distillations trays, settling units, and fuel gas and hydrogen recovery techniques are the primary focus of this section. Combining multiple distillation units (i.e., atmospheric and vacuum towers) into one divided-wall column can significantly reduce the amount of heat required for separation, and will have the additional benefit of reducing plot space for the distillation units. Progressive distillation technologies typically provide a more efficient use of process heat and result in reduction of heat demand from the distillation columns. Improved tray configuration may also contribute to separation efficiency. In terms of fuel gas and hydrogen recovery, membrane and adsorption processes are considered low-energy alternatives to conventional cryogenic separations. A look into R&D work on industrial-scale membrane technologies is included to evaluate those options that would be favorable for refinery implementation.
• Reaction Vessel/Metallurgy. Metallurgy and configuration of refinery reaction vessels will impact the energy demand of specific processes. Low-profile reactors for various processes are beneficial for refiners with plot space limitations and also to provide maximum efficiency by allowing lower pressure and temperature operations with shorter residence times.
• Auxiliary Equipment. Conventional motors, pumps, fans, and compressors are used in refineries to convert electricity into process work. In the latter three, motor use will account for about 95% of the electrical consumption and, therefore, optimization of these units will primarily focus on optimization of the motor. Motor systems account for 80% of electricity used in a refinery. About 55% of this electricity is lost due to conversion inefficiencies and distribution problems. Through various improvements, motor efficiency can be improved by about 12-15%, on average. The best way to improve efficiency within this area is to use both a systems approach while also looking to improve individual components. Motor, pump, and fan optimization can encompass several different concepts. Beyond the size of the pump, several other areas that can lead to inefficiencies include unnecessary operation of backup pumps, varying flow rate requirements, excessive noise, heat or vibration, and inadequate piping systems. Novel vacuum generating technologies (e.g., ejectors) can also yield efficiency improvements, as creating a vacuum environment is often a very energy-intensive process.
• Catalyst and Process Design Considerations. The refining catalyst industry is constantly producing novel catalyst formulations and shapes to enhance process yields and improve product quality. Some of these technologies may also result in significant energy savings for refiners. Catalysts with improved activity at lower temperatures and pressures can alleviate the demand for heat in some processes. For example, commercially-available solid acid alkylation processes have been claimed to reduce power consumption by 50% compared to conventional liquid acid technologies. Improved catalyst recycle/regeneration strategies can also offer limited improvements in the total energy consumption of processing units. On the process side, hydrogen-saving two-phase hydroprocessing, low-temperature fluidized-bed hydrotreating, and emerging energy-powered product treating methods (e.g., SulphCo's SonocrackingTM technology) are examples of energy efficiency and CO₂ reduction technologies refiners should consider.

Process operation strategies to promote energy efficiency are primarily related to various process monitoring, optimization, and control techniques. Several different companies offer energy and CO₂ management software programs to be used during the planning and operating stages of oil refining. The majority of these programs can be easily operated by refinery personnel after basic training. Some of the more advanced programs may require more in-depth training that is often offered by the company. In general, these software packages use onsite and historical data to set operational targets and efficiency goals. The data is used to generate predictive models with optimized designs. During operation, several of these programs can be used as process monitors and for advanced process control.

This Report will assess a wide range of technology advances used to improve energy efficiency and reduce CO₂ emissions in an industrial setting. The technologies and operational techniques will be evaluated with a focus on implementation in a refinery setting to provide energy use and CO₂ reductions with a positive return on investment, regardless of the price of carbon allowances.

Strategic Application of Energy Efficiency Improvements in Refining Processes

To manage energy effectively in a refinery setting, it is not only necessary to explore improvements on a site-wide basis but also focus on individual processing units' contribution to energy performance. This Report will serve to assist refinery operators in identifying the main contributors to energy inefficiency on an individual unit basis, as well as offer several methods to improve savings. The latest technological developments are discussed in the previous sections to present a glimpse into the future of refining technology and processes. Many of the strategies discussed here are commercially proven and supported by success stories from various refineries throughout the world.

• The crude distillation unit (CDU) is the largest energy consumer in a refinery, and overall savings of up to 55% ($5.9MM/y in a 5MM-mt/y [100K-b/d] refinery) can be achieved by improving energy use in this unit. Fouling control, heat integration, and novel technologies can be implemented to realize these savings.
• In the FCCU, a net energy producer, energy use can be reduced by 28% by implementing power recovery operations, minimizing heat loss, and implementing various other improvements.
• An estimated 31.5% energy savings is available in the catalytic hydrotreater through improved heat recovery with PINCH analysis and optimization of the preheater configuration.
• Additional strategies are discussed in this Report identifying methods to reduce energy consumption by 23% in the catalytic reformer and 38% in the alkylation unit; furthermore, various other energy-saving measures in remaining refinery process units are discussed.

The recommendations of this Report offer efficiency improvements through revamps and retrofits as well as designing grassroots refineries with integration as a primary focus. Following the discussion of various technology options and advances, potential improvements are discussed on a unit-by-unit basis to target the most effective areas for energy savings and emissions reductions in the refinery.

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