Several industrial sectors are keen to bring down their energy costs and optimize plant efficiency, as global energy prices remain somewhat volatile without any foreseeable stability. However, this is particularly critical to petrochemical companies.
Basic petrochemical operations, such as cracking, use up large quantities of energy and require extremely high temperatures, which have key implications regarding safety, cost, and equipment life cycles. Fortunately, these problems can often be lessened and, in several cases, financial and practical performance can be enhanced through the proper use of advanced thermal insulation and designs.
Fired heaters and furnaces are utilized across hydrocarbon, petrochemical, and chemical processing sectors, in applications ranging from coking, distillation, and alkylation to several types of cracking. They form the core of these procedures, however if they are not properly managed, they can become a liability.
All heaters utilize huge quantities of fuel, and the ensuing energy expenses can signify a considerable quantity of the cost of operating a petrochemical plant or refinery. So it is obviously in the best interest of operators to improve the operations and supervision of their furnaces and allied heaters. This is also important as savings made in these areas could have a key impact on profits.
Companies such as Morgan Advanced Materials are working to increase their range of thermal insulation options, such as highly flexible and lightweight solutions to reduce heat loss and enhance reliability and durability in petrochemical and refinery heaters. This is vital as time has exposed issues with conventional solutions that advanced products can defeat.
Traditionally, hydraulically bonded refractory castables were used to line heater floors, and are offered in powder form and blended with water prior to application. This process can be performed at the plant itself or in a fabrication shop. The shelf life of castables is limited, and although they can be robust, their performance depends a lot on the expertise of the installer. Other factors, such as the start-up process can also influence their functionality, and preliminary heat up has to be cautiously controlled, because if it is too quick, explosive spalling could occur.
Increasingly, operators are now lining heater floors with a ‘dry’ solution made up of high-duty firebrick supported by a structurally stable proprietary block insulation and insulating firebrick (IFB). The utilization of IFB is cost-effective and offers exceptional thermal efficiency, structural strength, and low levels of heat loss. These “dry floors” are highly efficient because of the superior thermal conductivity of the IFB (25 to 50% better than castable). Additionally, no blending or special dry-out is needed, which can decrease installation time.
Another alternative is to line up the heater floors with fiber logs comprising one of the latest, more thermally efficient monolithic high temperature insulation fibers, such as Pyro-Log. This easy-to-install Pyro-Log is created using a proprietary lubricant that burns out at medium temperatures. This makes the fiber logs adequately sturdy to stand on and also have an extended life cycle.
Supported by mineral wool block, high-temperature IFB has frequently been applied to safeguard the lower walls of floor fired units. However, these mineral wool-based blocks are likely to degrade, resulting in long term hot spots. The application of the latest microporous materials, which possess ultra-low thermal conductivity, enables users to prevent these issues and can offer numerous advantages. This can be seen in the case study below.
Ceramic fiber linings like layered blanket or modules with vacuum formed fiber peepsites are conventionally used to line the upper walls of floor fired units, however vacuum formed pieces can be costly and may result in brittleness during operation. It can also be complicated to unite vacuum formed shapes with the lining surrounding them.
These problems are overcome by the application of high temperature insulation fiber modules. These modules provide equal or optimized thermal conductivity and at the same time prevent the problem of broken peepsites and integrating different types of materials. High temperature insulation fiber modules are long-lasting, more durable than conventional options, and can be easily cut for application as peepsites. Also, high temperature insulation fiber modules compress in all directions, supplying an improved fiber-to-casing and fiber-to-fiber fit. In addition, the application of high density insulation fiber modules can offer main advantages in terms of decreased heat flow and substantial energy savings.
One current example relates to a main petrochemical company contacting Morgan’s Thermal Ceramics business with regard to six ethylene furnaces. The cracking method can be defined as the transformation of complex organic molecules into very simple molecules, by splitting the carbon bonds in the feedstock. In order to crack ethane (the feedstock) into ethylene, the ethane is heated to a very high temperature so that the molecular bonds are split and ethylene occurs.
In this case, when the client consulted Morgan, the furnaces of the client had been in use for a decade, and were lined to a depth of 200 mm (8”) with refractory ceramic fiber (RCF) 1260°C (2,300°F) blanket (25 mm or 1”) and RCF 1,430°C (2,606°F) modules (175 mm or 7”). Apart from being unproductive, these units had extremely high skin temperatures that workers protection had become a concern. The linings of the furnace also revealed widespread deterioration.
The client requested that Morgan measured the level of degradation in the lining, and based on that created a new lining solution that would decrease the casing temperature and optimize efficiency. The new lining depth was meant to not increase the thickness of that already in place.
Testing by Morgan revealed that the linings of the furnace had degraded by about 35-40%, and that the average temperature was X03=123°C (253°F). Therefore, Morgan recommended a complete re-lining of the furnaces, and provided the following solutions for the client to select from:
Solution A: RCF 1430°C (2,606°F) Pyro-Bloc modules 240 kg/m3 (15 lb/ft3) 175 mm (7”) and RCF 1260°C (2,300°F) Cerablanket 128 kg/m3 25 mm (1”).
Solution B: RCF 1430°C (2,606°F) Pyro-Bloc modules 240 kg/m3 (15 lb/ft3) 175 mm (7”) and microporous board 1000°C (1,832°F) at a thickness of 25 mm (1”).
Morgan prepared a number of solutions as the client was initially skeptical about utilizing microporous materials to line the furnaces. It was decided in the first phase that only two furnaces would be lined, with one microporous insulation and that the design for the other units would be informed by the in-field outcomes from the first two furnaces.
According to the customer’s needs, both of the planned solutions stuck to a lining thickness of 200 mm (8”). In the field, for Solution A the average temperature in area X03=104°C (219°F) while for Solution B, the average temperature in area X03=82°C (180°F).
Based on this, the client opted to re-line all of the other furnaces using microporous products, as this decreased the casing temperature by an average of 41°C (106°F). Eventually, this method was used to re-line all of the crackers. Advanced materials not only play an important role in furnace insulation, they can also assist in overcoming problems in areas that have conventionally been difficult to insulate. For example, burner blocks and side walls have frequently been lined with refractory castables and IFB, but the former present thermal shock problems, in the midst of other problems.
One solution is to restore the IFB with fiber, but when this is performed the castable burner blocks can result in issues due to thermal shock and extreme weight to the surrounding lining. This can be resolved with the use of the high density (240 kg/m3 or 15 lb/ft3) high temperature fiber (2600°F grade) as burner blocks. While this practice was once assumed to be highly hazardous, the flame pattern of the flat flame burner is ideal for a fiber burner block. With similar fiber materials, the adjoining wall is much easier to design and prevent probable hot spots.
Ceramic fiber modules provide a good solution here: although once thought to be hazardous in this setting, in reality high density monolithic ceramic fiber modules prevent the issues linked with castables, and transmit considerably less heat than brick or castables. They can also be retro-fitted to several burners.
High density monolithic modules 192- 240 kg/m3 (12-15 lb/ft3), which compress in all four directions, can also be applied to line tricky areas such as corners and arches. These modules are ideal for application in convection sections, but care must be taken to not steam clean the tubes, which can damage the lining.
Calculating the Benefits
The chemical processing and petrochemical sectors have obviously benefited from the development of lightweight and highly convenient heaters linings. However, with these developments, a new challenge has come up – that of comparing the available thermal insulation options and making a selection from amongst them that will improve the safety profile, productivity, efficiency, and revenue of the company.
The case study discussed here clearly indicates the way advanced thermal insulating materials can be used to transform thinner, older insulation designs to match the current requirements for energy savings and lining longevity, resulting in better furnace dependability, better bottom line, and a safer working environment.
Products such as IFB, lightweight microporous insulation, and monolithic fiber logs can all aid in altering the results in terms of finance and operation. However, in any heater or furnace re-lining project all options should be cautiously considered and factors such as heat loss, temperature, operating conditions, and energy consumption should be taken into account, so as to make an ideal choice of insulation and guarantee the best possible outcomes alongside optimized furnace consistency.
This information has been sourced, reviewed and adapted from materials provided by Morgan Advanced Materials.
For more information on this source please visit Morgan Advanced Materials.