Decarbonisation Technology - August 2024 Issue

Project data from 2007 HPHE installation in an aluminium furnace air preheater application

Project data from 2020 HPHE replacement in an oil and gas refinery

Technical data

Value

Technical data

Value

Exhaust gas mass flow, kg/h Exhaust temperature in, ˚ C Exhaust temperature out, ˚ C Combustion air mass flow, kg/h Combustion air temperature in, ˚ C Combustion air temperature out, ˚ C

89,900

Exhaust gas mass flow, kg/h Exhaust temperature in, ˚ C Exhaust temperature out, ˚ C Combustion air mass flow, kg/h Combustion air temperature in, ˚ C Combustion air temperature out, ˚ C

12,000

430 155

400 265

78,600

6,400

15

30

340

245 530

Energy recovered, kW

7,100

Energy recovered, kW

Recovered energy value, $/yr

155,000 210,000

Table 2



( Source: Econotherm)

Project cost, $

Payback period, months

16.2

included to handle high particulate matter exhaust. Table 1 shows that the HPHE met the customer’s expectations, and the client is now considering additional replacements at other refineries worldwide. Case study 2: Aluminum furnace air preheater In 2007, a leading multinational client assessed the need for waste heat recovery at its automotive parts casting facility in Kentucky, US. Prioritising reliability, low fouling susceptibility, and ease of maintenance, the client selected an HPHE to handle the plant’s air preheating needs. Installed outside the existing building housing the aluminum furnace (see Figure 5 ), the HPHE was connected to a cold combustion air stream,

Table 1



( Source: Econotherm)

acid condensation, leading to equipment failure and air leakage. In 2019, an integrated oil and gas company in Illinois sought to replace an underperforming DEKA air preheater with minimal modifications to existing ductwork. A 7.1 MW HPHE retrofit was completed in 2020, using vertically oriented finned heat pipes in a cross-flow configuration. Adaptive transition pieces connected the unit with minimal duct modifications. The HPHE included temperature-sensing heat pipes and specialty stainless steel heat pipes to guard against condensation during start-up and shutdown. Cleaning nozzles were also

directing preheated air back to the smelter burners. Existing smelter exhaust was rerouted to the HPHE inlet, with new piping and an exhaust fan installed. Table 2 shows that the HPHE exceeded expectations by delivering $150,000/year in energy savings against an initial estimate of $130,000/year. The project cost was $210,000, with a payback period of 16.2 months. Completed in March 2008, the installation has operated reliably with minimal maintenance for 15 years, prompting the purchase of two additional units. The total net benefit to the client has been more than $2.8 million and 4.257 MWh saved based

Hot exhaust from smelter

Preheated combustion air to smelter burners

Cooled exhaust to the new stack

Cold combustion air

Exhaust fan

Heat pipe heat exchanger

Figure 5 External HPHE unit installation as a combustion air preheater 

( Source: Econotherm)

www.decarbonisationtechnology.com

76

Powered by