Home / SHELL AND TUBE HEAT EXCHANGER – RECOVER HEAT FROM CORROSIVE FLUE GAS
You want to recover more heat from your flue gas, but corrosion concerns are stopping you. Your stack temperatures are kept well above the Acid Dew Point (ADP). HeatMatrix polymer air preheaters (APH) and heat exchangers allow you to recover the heat from the corrosive flue gas and turn your waste heat into profit.
A significant amount of waste heat in flue gases remains untapped due to the limited applicability of metal heat exchangers under conditions where acid dew point corrosion can occur. The HeatMatrix polymer heat exchanger overcomes this limitation and enables energy savings by up to 5% in combustion processes and even up to 25% on dryers. The HeatMatrix exchangers allow companies to save on energy costs and to fulfill their sustainability targets for a very attractive return on investment (Typical pay-out: less 2 years on the equipment itself).
In the search for energy efficiency in the industry waste heat recovery from flue gas and exhaust gas makes stacks one of the most interesting sources of lost energy to look at:
Large untapped amounts ofwaste heat. This heat canpotentially be re-used toheat up cold outside air forcombustion or drying. Thissaves energy costs.
Heat recovery from fluegases is difficult due tocorrosion and fouling.
HeatMatrix offers acorrosion and foulingresistant polymer airpreheater with a shortpay-back period.
ABSTRACT WHITE PAPER
Typically, flue gas is sent out the stack at elevated temperatures of 150 C and up. As a result, around 10% of the process heat is lost to atmosphere. Corrosion concerns have up to now stopped operators from recovering this heat. This corrosion arises from sulphuric acid condensation from the flue gas at temperatures below the acid dew point (ADP). This paper explains this phenomenon and how to calculate the acid dew point. The HeatMatrix polymer-based technology allows operators to recover more heat from the challenging flue gas. The paper looks at acid and temperature related corrosion rates and explains how cooling flue gases through the acid dew point reduces the corrosivity of the flue gas, thereby taking away the corrosion concerns that stop heat recovery in the first place.
AIR PRE-HEATER (APH)
The HeatMatrix air preheater consists of multiple corrosion resistant tube bundles contained in a metal shell or housing. The proprietary polymer bundle design consists of multiple tubes that are connected to each other over almost the full length of the tube. This structure creates a strong rigid matrix grid that is able to resist high gas velocities and thermo shocks. The supporting connector between the individual tubes creates simultaneously a counter current flow configuration between the two fluids. This configuration improves the heat transfer by 20% compared to cross flow type exchangers.
The system design allows for easy access to the polymer tube bundles. These lightweight bundles are retractable from the top and can be cleaned or replaced without demounting the complete exchanger. In the case of fouling flue gas each bundle can be equipped with a spraying nozzle, which thoroughly cleans each bundle in an alternating cleaning sequence during operation.
The capacity of the air preheater is fully scalable by placing multiple polymer bundles in a metal housing . The smaller size exchangers have a cylindrical shell and the larger size air preheaters have a boxed casing to accommodate flue gas flows up to 500,000 kg/hr.
The polymers applied for the HeatMatrix exchanger have a design temperature of 200°C. For applications with higher flue gas temperatures a hybrid design between a metal and a polymer part is offered.