Blog Details

Author:

James Turner, Executive Director, Process Technology & Engineering, Fluor

Introduction
Electrification of industrial facilities, such as chemical plants, refineries and manufacturing facilities can have many significant positive benefits, including lower consumption of fuel, water and steam, a decrease in emissions and an increase in equipment efficiency.

TABLE 1. Impact of electrification options

For any electrification effort, the upfront capital investment is often the deciding factor on the feasibility of a project. However, there are other factors that should be considered, including secondary impacts that could have unintended consequences for other utilities and systems.

Considerations for Electrification

1. When considering electrification, it is important that the operator develops an accurate power, steam and fuel gas balance for the facility. Consider upset and other operating cases, such as when individual units are shut down for maintenance.
2. Understand the reliability of the existing systems and what outages have a significant impact on operations.
3. Evaluate the planned project portfolio for the facility. Look for cases where projects can facilitate or be improved by including electrification as part of the project. As an example, if there are steam boiler replacement or reliability improvement projects, or pump or compressor replacement projects, there may be synergies for considering electrification as part of those projects.
4. Understand the cost for incremental power purchase and imported natural gas. Understand the upgrades to the existing systems within the facility that will be required with an electrification project. Also be aware of possible infrastructure impacts to the “across the fence” electrical supplier like the utility company.
5. Understand which current or future emissions requirements (including carbon footprint) may impact the facility and need to be resolved. These could be regulatory driven or internal company requirements. For example, if the existing steam boilers require the addition of nitrogen oxides removal equipment, electrification may provide an opportunity to build new, smaller, more efficient, and more reliable steam boilers for not much more than the regulatory revamp cost. Similarly, if there are steam boiler reliability upgrade projects planned, decreasing steam consumption instead of implementing a boiler replacement or reliability upgrade project may be a better option.

Electrification Impacts

Electrical Infrastructure

When evaluating a potential electrification project, it is important to look at the existing electrical infrastructure and whether it has the necessary spare capacity to supply the additional power load, as many facilities have limited or no spare capacity. This will require new infrastructure, such as new substations or upgrades to the existing infrastructure.

There are three key electrical system studies to be performed to assess the existing electrical infrastructure:

• Load flow to check the capacity of existing equipment to support the new loads.
• Short circuit to check if existing equipment is rated to support additional motor short circuit contribution.
• Motor starting to check if the new motor can be started without impacting the system voltage.

These are complex studies that can be performed by an experienced electrical engineer using commercially available electrical analysis and simulation software.

Upgrades to the existing electrical infrastructure may include additional utility power, including new transmission lines to take delivery of power at a higher voltage or expanding the cogeneration plant for more power generation if the facility has one.

There may also be an impact to the underground and aboveground electrical infrastructure and the associated impacts to pipe ways and other structural needs to support the new conduit or trays that will feed the new loads.

Lastly, the design must consider construction and cutover challenges. If electrification is done in an existing operating facility, the electrical upgrades need to be well-planned. Electrical work requires equipment to be de-energized, so it can be most efficient to conduct the work during a turnaround or during scheduled maintenance to minimize the impact on the operating facility.

Steam System

Electric motors can reduce steam demand when replacing steam drivers. However, it is important to understand the overall impact to the steam balance at the various steam levels. If the facility is long on low-pressure steam, electrification of a back-pressure steam turbine will reduce production of excess low-pressure steam. Conversely, if the facility is short on low-pressure steam, electrification of a back-pressure steam turbine may not have much value as most of the steam saved from electrification will need to be let down from high pressure steam to balance the steam demand.

Electrification of a condensing steam turbine will reduce high-pressure steam demand, which is usually generated in steam boilers. For most facilities, this can be a significant benefit.

Water Systems

Electrification can impact water systems. A reduction in steam demand leads to a reduction in the boiler feed water demand, including reduction in treated water make-up. Water consumption is often a major expense for an operating facility, so this reduction may have an enormous impact.

The cooling water system can also be impacted by an electrification project. Many large steam turbines are condensing turbines, which usually have large cooling water surface condensers. Replacing a condensing steam turbine with an electric motor can lead to a significant reduction in cooling water demand, which debottlenecks the cooling water system, potentially supporting other projects that would increase cooling water demand, and reduce cooling water make-up consumption. In some cases, an entire cooling tower or cooling water pumps may be shut down, reducing power consumption as well.

Electrification of a condensing steam turbine, however, eliminates production of vacuum condensate which is often used by some processes and an alternate clean water source will need to be made available for these users.

Fuel Gas System

Fuel gas consumption is often reduced if fired heat is directly replaced by electricity. This is beneficial if the fuel gas system is supplemented by purchased natural gas as electrification will reduce natural gas usage but could be an issue if the facility is long on fuel gas.

Many facilities run close to fuel balance and will be long on fuel gas with major electrification changes. If this is an issue, there may be options for recovering more propane, butanes and heavier hydrocarbon material from the fuel gas pool or potentially modify process unit operations to produce less of these components.

Projects to increase recovery of propane and heavier components in gas plants can have an exceptionally good payout in selling more liquefied petroleum gas (LPG) product in addition to the benefits of electrification. If this option is pursued, product storage and transfer logistics will need to be understood so all potential project requirements are addressed.

The potential impact to the fuel gas heating value should be evaluated with the reduction of LPG material in the fuel gas. Replacing LPG material with natural gas, high in methane, will lower the fuel gas heating value and there may be heaters that will have fuel gas hydraulic issues with a lower average heating value.

Flare System

Another electrification impact to consider is the overpressure protection/flare system. The flare load may increase during a local or total power failure scenario if a turbine-driven pump or compressor, not considered to fail previously, is replaced by a motor. Conversely, if a steam heat exchanger is replaced by an electric heater, a total power failure would cut the heat source that could potentially reduce the total relief load. The total power failure case is often the controlling scenario for the design of the flare and relief header system and may be a crucial factor favoring the case for electrification.

Conclusion

To find the best project for the facility, start with high level goals, develop a good understanding of the existing systems, and compare options while understanding which parts are independent that can be evaluated individually, and which parts are interrelated and need to be considered as a group.

Understand the potential benefits of electrification:

• Reduction in operating costs.
• Improvement in energy efficiency.
• Reduction in emissions.

And understand the costs of electrification:

• Capital cost to implement changes.
• System upgrades required (both within facility and by outside suppliers).
• Process inside battery limit and outside battery limit impacts, both positive and negative, for each option.

It does not help if a preliminary study makes an option look promising but impacts that were not initially considered make the option much more expensive or impractical.