The majority of large spinning, dyeing, washing, and weaving mills have implemented new heat recovery technologies to recycle waste heat energy from gas burners installed to run the factories.
Gas heat recovery has become the name of the game in the textile and garment industry for sustainability and a green revolution to save the world and the next generation while remaining competitive in the market.
Previously, the burner exhausts used to be released in the air but now the millers capture it to boil water and run air conditioning and other purposes for which they can save both energy and money.
The waste heat recovery system offers textile industries an economic and green solution to save valuable energy.
The system extracts and reuses waste energy from industrial processes instead of dissipating it into the environment, according to the Partnership for Cleaner Textile (PaCT), a programme led by International Finance Corporation (IFC).
Launched in 2013, the PaCT focuses on reducing the environmental impact and resource consumption of Bangladesh’s textile sector.
The PaCT said more than 338 factories are using the waste heat recovery systems and gas consumption has annually reduced by 1.26 per cent to 12,74,983 cubic metres from 12,91,122 cubic metres.
Industry operators said the recovered heat can be used for onsite power and steam generation and preheat combustion air.
“By using exhaust gas boilers, we have reduced natural gas consumption and increased engine’s overall performance and annual savings of $1.04 million,” said MA Jabbar, managing director of DBL Group, a leading textile and garment group.
The DBL’s 90 MW natural gas engine’s current efficiency is 56 per cent and it is working on the heat recovery to increase it to 61 per cent.
“I regularly review our energy efficiency level every month for further improvement to save the environment and also continuation of production,” said Jabbar, adding that he plans on solar energy accounting for 10 per cent of the group’s power consumption by 2025.
One of the processes involve converting the exhaust fuel into steam which is fed into a turbine to produce electricity, said A Matin Chowdhury, managing director of Malek Spinning Mills.
However, these steam turbines can only convert 35 per cent of the steam into electricity, he said.
Wherever the industry uses captive power units, steam can be additionally generated for various other uses, such as for chillers, dyeing and availing hot water, which would have otherwise required consuming additional gas, he said.
The overall gas consumption in such industries attains efficiencies of 81 per cent to 86 per cent. Where combined cycle power plants are run, the efficiency is higher, at 47 per cent to 52 per cent, Chowdhuy said.
Chowdhury said he has been making savings capturing waste heat energy from gas usage in his three units including Knit Asia, Salek Textile and JM Fabrics at Shafipur in Gazipur.
He produces 50 tonnes of fabrics a day to produce garment items at Knit Asia.
Md Anarul Islam Sarker, deputy general manager for utility and maintenance at Fakir Apparels, operates four natural gas-fired generators to run facilities.
The generators generate huge amounts of high-temperature exhaust gases, which are used to power boilers and produce steam for fabric ironing, dyeing, and finishing units.
The company’s electricity and boiler fuel demands have been lowered by 27,456 kWh/year and 2,595,840 m3/year, respectively, thanks to the waste heat recovery system.
the factory saves $208,615 per year thanks to waste heat recovery, which cost $177,000 to implement, Sarker said.