Now, reports Patricia Provot, President of the Americas at Armstrong International, change is afoot and energy efficiency is taking on an entirely new meaning.
Today’s chemical facilities are increasingly focused on achieving much greater decarbonisation gains by applying a circular approach to utilising thermal energy.
This new methodology involves recovering massive amounts of energy that escape a plant as waste heat and rerouting it back into the process (where it can be used as viable energy).
Offering chemical plant up to 40% reductions in terms of energy demand and carbon dioxide (CO2) emissions, net-zero goals have become much more feasible. But, before we dive into circular thermal, let’s take a quick look at making incremental improvements.
Steam generation and distribution
In many industrial facilities, including chemical manufacturing plant, steam is the lifeblood of the operation by providing the necessary heat for process or building applications.
Although generating steam is relatively efficient (approximately 80%), many systems within today’s industrial plant are decades old and have been reconfigured many times as processes or facility requirements change.
This can lead to system efficiencies as low as 60%, which is bad for a company’s bottom line and can make it difficult to comply with the emissions standards of regulatory bodies. The problem is only heightened as increasing legislative demands and elevated public concern continue to raise the stakes.
Therefore, companies need a thorough understanding of their steam system’s energy consumption and CO2 emission levels, as well as its safety and reliability — all of which can be evaluated with a thermal audit.
A thermal audit will uncover opportunities for incremental improvements that optimise a steam system. Although energy savings may be limited to a 10–12% gain in efficiency, results are immediate.
Potential upgrades include ensuring that the quality of combustion in the boiler is set for optimal performance, increasing the dryness fraction/level of steam, adding an economiser or condensing economiser to the boiler stack to recover energy and addressing condensate pollution.
It's also important to understand that the larger a steam network is, the more opportunity there is for heat to escape. Using thermal cameras can help to identify heat loss regions, uncover the state of the insulation surrounding the steam lines and identify any valve and pipe accessories that are not insulated.
Meanwhile, as part of a proactive steam trap management programme that includes software and a database, all steam traps should be monitored or tested annually at minimum — followed by the swift replacement of failed traps.
Maintaining a trap failure rate below 5% will ensure that the system is operating efficiently and safely.
Finally, plant engineers can look to the condensate return to make an additional 3–4% improvement in efficiency.
For low-pressure steam systems, adding a pumping system when the pressure in the heat exchanger is lower than the condensate return pressure will help to return condensate that otherwise couldn’t do so gravitationally.
For high-pressure systems, it may be helpful to use flash steam (condensate revaporisation once it reaches lower pressures) in a nearby application, helping to reduce steam use and consequent energy loss.
A roadmap to net zero
As mentioned previously, applying a circular approach to thermal energy offers far greater results to a chemical plant’s efficiency than those achieved by incremental changes (by as much as 40%).
This, however, requires a way of thinking that’s entirely different from traditional ideas of energy efficiency. Instead, we take a holistic approach.
What does that mean? For starters, your chemical plant might not need to use steam for some applications. Often, we see facilities using high-pressure, high-temperature steam because it’s an easy medium to produce and distribute … and it requires less space and smaller piping than water.
But, all too often, the process doesn’t need such high temperatures, so you’re sacrificing efficiency for convenience. If net zero is the goal, and the temperature requirement is less than 248 °F/120 °C, then the obvious choice is hot water, which can offer 90% efficiency or more.
That’s a significant jump from the 60–80% efficiency of steam.
At this stage, an important question to ask when taking a circular approach is: “Where is the energy going?” The unfortunate reality is that most of a chemical plant’s primary energy escapes into the atmosphere as waste heat — typically lost through stacks, cooling towers and sewage.
Only a small amount of that primary energy is converted into chemical energy that’s contained in the final product.
Utilising a circular approach allows us to capture waste heat and put it back into the process — in the form of hot water or steam — drastically reducing the amount of energy needed to operate the plant and maintain its processes.
Pinch
Vital to industrial waste heat recovery is a methodology known as Process Integration (PI) or Pinch, which involves mapping all heat sources and heat sinks within a facility to identify the baseline energy demand and heat recovery potential.
Once the mapping is complete, a trained thermal energy expert can develop a plan to optimise heat recovery systems, energy supply methods and process operating conditions.
Next, an engineer can use that model to determine what heat recovery methods are feasible for that particular plant, whether it be direct heat recovery using heat exchangers and coils or installing heat pumps to increase low-grade heat to a temperature that’s needed.
Although industrial heat pumps have been in use for many decades, recent technological advancements have greatly improved their efficiency, enabling them to easily produce up to 248 °F/120 °C of hot water or even steam.
Utilising an industrial heat pump in place of a traditional boiler can provide as much as 3–5 times more efficiency at low and medium temperatures, significantly reducing a plant’s energy use, production costs and CO2 emissions.
When deciding on specific heat recovery methods, engineers consider several variables depending on the plant’s infrastructure. Heat source locations, timing and seasonality are all parameters that are studied to ensure a pragmatic solution is designed.
In situations when there is no time synchronisation between heat sinks and heat sources, energy storage systems may be implemented to balance energy supply and demand.
Applying this Pinch model to chemical plants that use low and medium temperatures will significantly reduce its energy demand. In fact, chemical facilities that utilise Pinch can operate at 60% of the thermal energy previously required without compromising productivity.
In addition to cutting energy costs and improving efficiency, utilising Pinch sets a plant up for an easier transition to complete decarbonisation. Why? Because, in many cases, the distance to net zero is cut significantly, allowing engineers to bridge that gap more cost effectively with clean electricity such as solar or wind.
Conclusion
As the cost of energy continues to rise and becomes more of a business risk, organisations are looking at energy efficiency as a necessity to maintain relevance in an increasingly competitive marketplace and remaining compliant with evolving regulatory demands.
Not to mention, it’s the right thing to do for our planet.
Whether the focus is on incremental improvements or a circular thermal approach, both are practical and effective strategies to reduce a chemical plant’s energy demand and CO2 emissions.
And whereas those quick and incremental wins offer immediate cost-effective results, circular thermal methodology can position companies for long-term energy savings and futureproof them for tomorrow’s energy challenges.
