Insulation is key to increased efficiency

Jan 18, 2012 | Heat Transfer

Richard Barlow, technical applications engineer, Morgan Thermal Ceramics, reviews the type of insulating products available for use in industries such as chemical and hydrocarbon processing. He looks at key material properties, types of insulation and gives some application examples

The continuing high energy prices and the need to reduce greenhouse gas emissions are driving companies in the chemical and hydrocarbon processing industries to review all aspects of their energy use. One key area is the efficiency of the insulating systems in their high temperature processing equipment.

A variety of lining products is available for thermal processing equipment in applications such as fired heaters, secondary ammonia reformers, sulfur recovery units, fluid catalytic cracking units and boilers.

Typically, many processes are lined with dense castables or conventional firebrick as these offer long life and resistance to chemical attack in harsh environments. However, a high temperature fibre thermal insulation from Morgan Thermal Ceramics, which is up to 20% more energy efficient than competitive insulations, is now available.

Operating conditions in chemical processes are harsh with corrosive atmospheres and high temperatures present. To restrict heat loss and increase energy efficiency, insulations must be able to withstand such environments and should have a number of important characteristics to provide reliable performance over a long life.

Resistance to abrasion and thermal shock, good cold strength, excellent hot strength and thermal stability, and low shrinkage all contribute to a superior insulation that remains effective and will stay in place, without degradation. It should also be easy to install to minimise process downtime.

There are various products available,?which are described below:

Insulating firebricks

IFBs offer good thermal efficiency, low heat loss and robust structural properties. They are durable and withstand high velocity process gases. Low and high temperature grades of IFBs are available for use at temperatures up to 1790°C and are more thermally efficient than dense castables in the same temperature range.

Monolithics and castables

Monolithics and castable insulations are suitable for where specific shapes are required, and provide insulation at temperatures up to 1800°C. Different formulations and densities can be manufactured depending on process requirements and various grades have been developed for high temperature insulation, metal contact, slag resistance, abrasion resistance or thermal shock resistance.

Insulating fibres (insulation wools)

There are two main types of insulating fibre – refractory ceramic fibres (RCFs) and alkaline earth silicates (AES). The fibres are available as blankets and offer high strength and surface integrity. They are tough, resilient and strong, and resist tearing before and after heating.

RCF in general is a suitable insulation material for high temperatures and can withstand repeated operation at a higher temperature than AES fibres. For example, Morgan Thermal Ceramics’ Cerablanket insulation can withstand temperatures up to 1260°C and Cerachem and Cerachrome fibres have a high classification temperature of 1425°C.

However, AES wools are more environmentally-friendly and have a lower biopersistance than RCFs. For example, they are exonerated from the carcinogen classification in the European Union under the terms of Nota Q of Directive 67/548/EEC.

Morgan Thermal Ceramics has recently introduced Superwool Plus fibre, a high temperature insulation wool that provides insulation in applications up to 1200°C. It has lower thermal conductivity (up to 20% lower) than competitive insulations, and enhanced energy saving properties with improved handleability.

Superwool Plus is efficient at restricting energy flow while maintaining other key material properties such as low shrinkage and good mechanical durability. It delivers high performance with less mass and blanket thickness than alternative products. Consequently, users can use less insulation and make weight and cost savings.

There are many applications where insulation is used in hydrocarbon processing, for example:

The fired heater is the ‘central processing unit’ in many refineries and petrochemical plants. Insulation linings are used in the floor and walls, the convection section, stacks and any ductwork in between. In these applications, high quality castable products such as Kaolite, Firelite or Tri-Mor insulating castables offer superior heat savings and long service life.

Hydrogen transfer lines and secondary ammonia reformers present tough operating conditions for refractory materials due to the high pressure, high hydrogen environments.

High purity, low silica hot face lining materials, such as the company’s Kao-Tab 95, are suited to these harsh conditions because they can withstand the aggressive atmosphere. Insulation with low levels of iron and other impurities make them resistant to tough, reducing atmosphere conditions. As temperatures increase and dew points drop, high refractory purity provides a long life lining.

High alumina (90+%) bricks with ultra-high purity, such as Morgan Thermal Ceramics’ SR dense firebricks are suitable in catalyst support domes and checkers as they can withstand difficult applications. High purity bricks offer good load-bearing strength at temperatures above 1649°C and provide good thermal shock resistance.

In conclusion, by using the next generation range of efficient high temperature insulations, process managers can reduce heat and energy loss to increase efficiencies and achieve cost savings while protecting the environment.