Stepping Up Profits
There are two primary reasons for petrochemical facility owners to consider an energy appraisal: to reduce cost or to increase productivity, both of which should increase profits.
The primary motivator of these two profit enhancers is cost savings, or reduction. The cost of energy, or better said, the cost of "lost" energy, becomes a greater factor in times of rising energy costs, like we are seeing today. The price of natural gas has risen steadily over the past decade; nearly doubling in price, and currently sits near $7 per million BTU. Crude oil has risen 50 percent in the past year and a half and is hovering around $60 per barrel. The cost of coal has been a little more stable, but is utilized less in the petrochemical industry as a source of fuel.
Increasing productivity by reducing energy loss—either through heat loss or heat gain—is generally more critical than reducing cost, and is less often left ignored. Increasing energy efficiency can enhance productivity by providing dryer steam to a turbine, resulting in, among other things, less maintenance issues. Delivering more heat to the process can allow for a more efficient reaction or more output. Or, proper temperature control can allow an otherwise non-viscous material to flow.
Whether reducing cost or improving productivity, insulation maintenance issues can easily be seen as a potential root cause of heat loss or heat gain problems. Absent insulation is obvious, if one would take the time and effort to notice it missing. But damaged insulation generally evolves over time and can go unnoticed.
It is much more difficult, however, to determine the effect of insulation issues, such as BTU loss. 3E Plus® software can help determine the calculations if the proper data is gathered. But, knowing how many BTUs are being lost is only the first step. The facility owner must also make a business decision about whether to correct any deficiencies, or do nothing and maintain status quo. The business decision generally is not driven by energy savings, but instead, payback: How much time is needed for the energy savings to cover the cost of the repairs? With the rising cost of energy in today’s environment, the payback period is becoming shorter each day.
At one resin plant in Pennsylvania, payback was not the concern: It had more to do with work stoppages, the unplanned type. Resin lines had a tendency to plug up when product was transferred from the production unit to the storage tanks located across the plant. The situation was especially noticeable in the winter months. The resin line was designed for 450 F and the resin would begin to solidify at or near 400 F. The resin transfer lines were kept at the appropriate temperature by a combined process of hot oil jacketing, steam tracing and electric tracing of the line.
The plant maintenance group was aware of the general condition of insulation on the transfer line and knew that it was at least a contributing factor in their plugging problem. (See Figure 1.) An energy appraisal was done to determine where the heat loss was occurring. Although in some locations the insulation was clearly damaged or missing, there were also locations where the insulation appeared to be in an acceptable condition, but was, in fact, performing very poorly.
As a result of the energy appraisal, the plant was able to determine areas where damaged, missing or improperly installed insulation was allowing considerable heat to escape the surface, resulting in a cooling of the pipe. Concurrently, the plant evaluated the efficiency of the tracing methods they were using and found opportunities to improve them. The plant performed the repairs to both the insulation and tracing systems and the transfer process was corrected.
Through the energy appraisal, defects of the insulation found throughout the plant were discovered and a priority plan—based on the plant-specific focus—was created to address improvement opportunities. Saving energy at the resin unit was one opportunity found in the plant, but the plant has yet to follow up on this. In the process, however, they have addressed problems with a cold service unit that utilizes brine at 5 F and glycol at 30 F. The piping and storage tank for these products were found to have corrosion under insulation (CUI). When there are defects in the weather barrier in cold service insulation applications, condensation results, which, if left unchecked, can lead to corrosion. An energy appraisal can locate areas of heat gain and be a valuable tool in addressing CUI. (See Figures 2 and 3.)
Crushed Insulation Reduces Plant Efficiency in the Carolinas
A chemical plant in the Carolinas requested an energy appraisal to determine if the noticeably poor condition of insulation in their pipe bridges was resulting in lost BTUs. This was a relevant concern since the plant was switching from a steam system generated by boilers within the plant to steam purchased from an adjacent cogeneration facility. In addition, their furnaces were fueled by natural gas, which produced hot oil at an elevated temperature of 650 F. The plant’s utilities group was spearheading the effort to locate and eliminate energy losses. This group was responsible for the delivery of the steam and the hot oil to the operating units in headers that ran inside the plant pipe bridges, and their intent was to deliver the steam and oil as close as possible to the temperatures at which they were generated.
While there was extensive damage to the insulation in the pipe bridges, there was little or no missing insulation. The insulation that was damaged was primarily crushed. Through further investigation, two primary causes were discovered for the crushed insulation, both dealing with operator access.
The first cause dealt with valve-handle access. Operators turning valve handles required a place to stand, and, in the absence of a platform, would stand on top of adjacent insulated piping. The weight of the operators crushed the insulation. The second cause was the tops of insulated piping serving as walkways. Operators or maintenance workers obviously walked from one building to another along the tops of the lines in the pipe bridges, resulting again in crushed insulation. (See Figure 4.)
The steam and hot oil systems were insulated with various materials in different sections of the plant. Calcium silicate had held up much better than mineral wool. What was discovered, however, was that insulation performing far below its design capabilities, even at reduced thickness, still had insulating value. The result was energy savings below expectations, and subsequently longer payback periods. A plan to correct the damaged insulation and to address some of the access issues that caused the damage—building platforms and walkways or specifying a more rigid insulation material—was under consideration by the utilities group, but the long paybacks and a subsequent reorganization of the utilities group has delayed action.
Also during the energy appraisal, one unit was found to be operating at full capacity. It was running wide open, to the extent that all bypasses were opened to gain more consistent temperatures from their hot oil system and, thus, more consistent product flow. It was initially believed that increasing the temperature delivered to the unit, by reducing the amount of heat lost in the transfer of hot oil, could increase the output of the unit. This situation merited action and further study was done. It was found, however, that flow restrictions was the greater factor in limiting production increases as opposed to heat loss, and plans to correct the insulation were tabled.
A chemical plant in Tennessee conducted a small, pilot energy appraisal in several areas of their facility in an attempt to locate areas of heat loss or gain that would result in enough energy savings to justify insulation repairs and to expand the scope of the appraisal to include a larger portion of the plant.
The sections of the plant selected for the pilot were chosen to provide a contrast for evaluation. One section was an older operating unit in the plant, which was expected to have significant energy-saving opportunities due to neglect and general aging of the insulation. A second section was chosen due to its recent construction. Here the owner expected to find few saving opportunities, but believed it would provide a contrast of age and newer specifications. The first section had two areas with steam systems and processes that were heated by steam supplied by the plant’s coal-fired boilers. The third area was a hot oil system loop, and was chosen because the fuel for this furnace is natural gas.
The energy appraisal of the first two pilot areas revealed energy-saving opportunities, much more in the older area as expected, but with some opportunity in the newer unit as well. However, the savings were smaller than expected, due to the relatively low temperature of the steam utilized and the lower cost of BTUs generated with coal. The operating temperatures were generally 250 F or less, with a few lines up to 400 F and a limited amount of 600psi steam at a higher temperature. When the cost of repair was calculated, the payback period was too long to justify the expense of repairs.
The steam was generated in-house with coal-fired boilers tasked to generate electricity for the plant. Steam generation was not the primary function of the boilers but more a by-product of generating electricity. This dual purpose, along with the relatively low, stable cost of coal, limits repair to damaged insulation of steam systems—or any steam-heated processes in the plant—because of modest savings and long paybacks. Even if the insulation proved to be more efficient, the plant would still produce the same amount of steam to generate electricity. This is a factor in a facility producing more steam than it can use or needs. A plant that is "steam limited" would benefit considerably from even the smallest improvement.
The hot oil loop proved to be quite different. The temperatures were higher—nearly 700 F—and the furnaces were fueled by natural gas. The savings were significant and payback periods averaged less than six months. One furnace was already scheduled for replacement due to corrosion, but energy savings will be an additional benefit. There will be further savings when bare pipe or damaged insulation is repaired. (See Figures 5 and 6.)
During the process of evaluating the three areas chosen for the pilot, a fourth application revealed itself. A refrigeration room within the plant had numerous cold service applications, including ethylene glycol at 26 F and chilled water at 38 F. The purpose of this pilot was not to find energy savings, but safety and health concerns. There was a significant condensation problem within the building that was making the floor unsafe. The fuel source for the equipment was steam from the boiler, so expectations of significant savings and quick paybacks were low. However, resolution to the condensation issue was expected. In addition, CUI was discovered. (See Figures 7 and 8.) Action was taken in the refrigeration room to remedy the issues as a result of the energy appraisal and insulation survey.
One refinery plant in Texas diligently measures energy consumption. Their initial effort to reduce energy costs—fueled by the rising price of natural gas—was to repair or replace all of the steam traps within the plant. The plant spent approximately $70,000 surveying the traps and making the necessary repairs or replacements. A work-when-available plan accomplished little in the year it was utilized, but once a dedicated crew was committed to making the recommended improvements, it was accomplished within a two-week period. The resulting energy savings was an impressive figure, approaching $500,000.
Based on these results, the plant selected three of their units with the highest temperature processes—and highest energy consumption—and performed an energy appraisal. The focus of the appraisal was to find uninsulated pipe and equipment and determine the potential savings. The items that were found uninsulated and operating at elevated temperatures included pipes, valves, flanges, exchanger heads, pumps, turbines and man ways. In one fluid catalyst-cracking unit (FCCU), more than $800,000 in potential savings was revealed in the 106 items identified as energy-saving candidates. The biggest potential savings in the unit was found at a waste-heat boiler, where all of the outlet headers were 700 F and missing insulation. (See Figures 9 and 10.) Almost one-third of the potential savings found were in that one area alone.
There was also extensive savings potential from insulating valves and flanges that were purposely left bare due to a plant specification not to insulate valves and flanges that could potentially leak and go unnoticed. Two options were offered: insulate just the valve bodies, leaving the flanges exposed for visual inspection; or also insulate the flanges, utilizing drip tubes that would allow leaks to flow through and still be visible during inspection.
The energy appraisal was engineered by professionals who quantified and planned the repair and replacement work, versus a crew turned loose in a unit to "fix" the insulation. Initially, the insulation work was scheduled to begin in the FCCU. The majority of the listed items in the FCCU were corrected; however, the savings anticipated as a result of the appraisal have been difficult to quantify.
The decision was made to insulate only the body of the valves and not the flanges that were listed. BTUs were saved, but not nearly to the extent that insulating the entire valve and flange together would have saved. It is also possible some saved energy was deflected to other areas of the unit for consumption. During the project, the dynamics of the unit’s regeneration process and flue gas system changed. The insulation repair project took three months to complete, during the same time these other changes were occurring. Had the project been completed quicker, the plant would have been better able to quantify the energy savings. As it is, energy consumption has increased, but how much more it would have increased is nearly impossible to determine.
As the example plants have proven, there are some good reasons to utilize an energy appraisal for the operation and maintenance of a petrochemical facility. Many times, appraisals will even locate unplanned and additional energy-saving techniques. Most importantly, though, appraisals can increase profits through saving energy and increasing productivity.
For example, in the resin plant discussed, plant production issues were the driving force; and with data from the energy appraisal, the issues were corrected. As a bonus, several additional insulation-related concerns were identified in the plant, and those concerns were addressed in a planned—rather than emergency—basis.
The Carolina plant was seeking to identify energy loss in the pipe-bridge headers. This was a preventative step against rising energy prices that could show themselves through a new energy source (cogeneration facility) and consumption measuring system. While this survey did not result in action, it did provide the owner with the data to make the do-nothing decision.
The Tennessee plant, through the data provided from the energy survey, was able to determine which of its high energy-using processes could have improved energy retention. In addition, an energy appraisal in the refrigeration room provided data to correct the condensation issues they were having, as well as identify CUI, and develop a plan to address these issues.
The Texas refinery sought an energy appraisal as a follow up to improvements they discovered in their steam-trap program. Action was taken based on the data developed with the survey, and while measuring the improvement has proven to be difficult, it has nonetheless improved the potential for energy savings.
Whatever the reason for an energy appraisal, the data garnered will always prove valuable, and, in many cases, open the door to additional, unexpected information that can reduce long-term maintenance problems and save the facility money.
Click Photo to Enlarge
Figure 1. Being used as an access walkway damaged the insulation on this transfer line, resulting in significant cooling of the process.
Figure 2. The energy appraisal revealed many defects in the insulation system, as seen in this brine line.
Figure 3. Infrared demonstrates unwanted heat gain on the cold brine line.
Figure 4. Operators using these lines as walkways caused serious insulation system damage.
Figure 5. Repairing damaged insulation on elbows, like this one, further improves energy efficiencies.
Figure 6. Infrared demonstrates areas of heat loss on 700 F line.
Figure 7. The energy appraisal revealed corrosion under insulation.
Figure 8. Infrared details areas of heat loss due to condensation damage.
Figure 9. All outlet headers on the 700 F waste-heat boilers were missing insulation.
Figure 10. Infrared reveals areas of significant heat loss from absent insulation in the boiler area.