The World Health Organization (WHO) estimates that nine out of ten people every year breathe polluted air. Fine particulate matter and high concentrations of damaging gases such as sulphur oxides account for around seven million deaths a year.
Internationally, heavy industry remains a major contributor to poor air quality. Until now, coal-fired power plants have done the most damage, but as numerous nations take corrective action to reduce coal-related emissions, other industries have shifted into the spotlight.
Earlier this month, the Chinese government moved to implement new regulations in the local steel industry, requiring steel plants to comply with new ‘ultra-low’ emission criteria by 2025.
Steel has become the leading polluter in China since the government targeted coal-powered plants with a similar campaign. China manufactures almost half the world’s steel, five times more than the European Union.
Making steel is a dirty job
As with coal-burning power production, making steel is a dirty job. It requires the consumption of large quantities of coal and coke, using these as fuel to drive the manufacturing process.
The environmental impact is significant. In Beijing, the nation’s capital and home to more than 20 million people, air pollution exceeds WHO guidelines by five times.
In 2018, the city’s air concentrations of PM2.5 - a closely-watched particulate because of its ability to enter deep into the lungs - averaged out at 51 micrograms per cubic metre (m3). The WHO suggests that PM2.5 should not exceed 10 micrograms per cubic metre.
This extreme pollution is partly due to the concentration of steel production in the northern Beijing-Tianjin-Hebei region. Due to emissions interventions started as far back as 2012, coal power pollution has steadily decreased. Eventually, In 2017, steel moved past coal to become the biggest air polluter in the country.
Radical emissions reductions are possible
However, a recent case study at the Yancheng Steel Plant just north of Shanghai shows that radical emissions reductions are possible when making steel.
On behalf of the Lianxin Steel Group, Pacific Green Technologies (PGT) recently installed the ENVI-Clean™ Flue Gas Desulphurization (FGD) system at Yancheng. The plant burns coal and coke to produce steam that powers a turbine generating 93 MW of electricity.
The FGD solution extracts more than 99% of the sulphur dioxide from the plant’s new power boiler exhaust gas, which contains up to 250 mg/m3 of SO2.
This brings Yanchen well in line with 2025 emissions controls. In addition to particulate matter, another dangerous by-product of steel manufacturing is sulphur dioxide (SO2). Current standards require producers to limit emissions of particulate matter to 50 milligrams (mg) per cubic metre (m3) and sulphur (sulfur) dioxide to 200mg/m3.
Under the new rules, however, steel plants will only be permitted to generate 10mg/m3 of particulate matter, and 35mg/m3 of SO2 – a five-fold reduction. Yanchen Steel Plant is achieving SO2 emission levels below 3mg/m3.
Inside the FGD system’s primary absorber vessel, PGT’s patented TurboHead™ technology creates a limestone slurry froth which works towards maximum SO2 absorption. As the sulphur dioxide reacts with water it produces acid, which is then neutralised by the limestone and converted to gypsum.
The gypsum solids are continuously removed from the system, before being concentrated into a gypsum cake which can be sold or disposed of in a landfill.
The efficacy of this system should be encouraging to Chinese steel producers. In addition to avoiding penalties, plants that transform to meet new emissions standards will receive more support on taxes, finance, and environmental protection policies.
This technology has global relevance. PGT’s partnership with massive Chinese state-owned enterprise, PowerChina, makes the FGD system a viable solution at an international scale.
This is especially critical in countries such as China, India and members of the developing world which are seeing major industrialisation. The movement towards alternative energy is positive but slow. In these regions, governments and industry are often given a stark choice: growth or clean air.
When burning fossil fuels, atmospheric emissions of SO2 can be reduced by lowering the sulphur content of the fuel, removing sulphur at the time of combustion, or removing SO2 after combustion.
Where national industries have little choice but to burn fossil fuels, option one is often not available.
The primary process applied option two - extraction of sulphur at point of combustion - produces large amounts of alkaline waste, uses twice the amount of sorbent as an FGD system, and is not as effective.
The post-combustion FGD system is the most efficient SO2 extractor available to heavy industry players needing to improve their compliance standards.
With its large production capacity, trademarked technology and international reach, Pacific Green Technologies is uniquely placed to bring this solution to plants across the world.