Up and out for healthy air

13 December 2018

To stop the flues of power stations or factories from emitting too many pollutants and endangering the health of both people and the environment, statutory limits must be observed. Compliance is monitored by emissions experts from TÜV NORD like Christian Thometzek. We peered over his shoulder in Hamburg as he was taking measurements of pollution emissions at the ship loading facility at the Moorburg CHP.

There’s a lowering sky over the combined heat and power plant in Moorburg. For Christian Thometzek, it’s up and out into the elements in spite of the persistent drizzle. Weighed down with cable drums, a sampling probe, a gas meter, a pump and a variety of small instruments and sensors, the TÜV NORD expert climbs the stairs of the ship loading facility. Up he goes, step by step via a large platform, leaving the power house behind him on the level below. And still higher, on a latticework staircase through which he has an unobstructed view of the yawning depths beneath him, until he reaches the flue through which scrubbed gases from the plant are blown out into the air. This is the reason why he's up here today.

The power plant is constantly visited by ships bringing the coal it needs to keep running; other smaller ships remove the ash left over from the combustion process. One of them is docked just below him at the foot of the loading facility on the quay wall and is patiently waiting for ash from the power plant, which is loaded into the bowels of the ship and transported away for further processing. However, this operation is not without side effects: Whenever hundreds of tonnes of ash are loaded into the belly of the ship, a whole load of dust is kicked up into the air. Conveyor belts between the ship and the power plant used to be deployed for loading and unloading. This way, however, the ash used to spread unchecked into the environment, soiling the laundry of nearby residents and impacting on their health. Since 2005, a law has been in place governing exactly how much ash may be emitted into the environment. To keep the emissions as low as possible, continuous ship-unloading and loading systems are now used – and it is this very steel structure on which Christian Thometzek is just in the process of getting his measuring equipment ready.

The expert explains how a massive tube is fed down into the ship’s cargo bay to carry the ash. “Any dust that’s generated is immediately removed with suction and transported through pipes to a dust filter - which is an outsized fabric bag with a very fine structure and grain.” No more than 5 milligrams of dust per cubic metre leave the flue – so, at least, the manufacturer promises. And it’s Thometzek’s job to check whether the scrubbing systems are actually delivering what they say they deliver.

With a probe somewhat reminiscent of a welding torch, he sucks air from the exhaust flue. This passes through a balanced filter sheet previously installed in the probe. If there is any dust in the air, it is captured in the fine structure of the filter, which looks rather like a powder puff. “To get realistic results, the air must be sucked in at the same speed as the exhaust gas flowing through the flue,” Thometzek explains. If the speed were different, larger or smaller particles would increasingly get caught in the sample. To ensure that this doesn't happen, the expert first of all measures the air flow in the exhaust gas flue and sets the suction device at the correct speed with a frequency-controlled pump. In the next step, the exhaust gas is sent through a drying tower. The crystals in the large cylinder extract the moisture from the exhaust gas to protect the instruments. The volume of the gas is then determined using a gas meter. Later on, in the lab, the filters are weighed. In this way, the expert can determine how much dust has accumulated in the filter. He can in this way calculate how much dust is contained in each cubic metre of air in relation to the volume of the extracted exhaust air flow.

The German Immission Control Act stipulates that approved plants must be checked every three years for compliance with the statutory emission limits. However, these intervals are not set in stone. “If the authority doesn’t trust the operator or the condition of the plant, it can also specify shorter intervals, for instance annual measurements. It would even have the right to take a measurement every two weeks,” Thomatzek says. Whenever plants change their operator, the authorities can stipulate more frequent checks.

In the CHP plant in Moorburg, Christian Thometzek isn’t on this occasion acting on behalf of the authorities; instead, he is voluntarily carrying out on-the-spot measurements by order of power station operator Vattenfall, which is acting in its own self-interest. “The manufacturers of filtration systems promise what we call a guaranteed value,” Thometzek says. If the plant is operating according to the regulations, the dust emissions shouldn’t exceed a certain value. As the expert explains, “Vattenfall regularly arranges for measurements to find out whether this guaranteed value is being adhered to, if the plant is still state of the art and, if necessary, to bring forward maintenance work.” This is because power plant operators also have a financial stake in perfectly functioning filtration systems. “If the locals notice more particulate matter pollution than is allowed by law, the operator will in cases of doubt have to answer for it,” Thometzek explains. At the same time, the dust damages the mechanical systems of the plants themselves. If, for example, it settles on the rollers and bearings of the conveyor belts, these will wear more quickly and have to be cleaned at considerable expense. “This is why the operators like to have the systems checked as often as possible, to avert the risk of damage in the first place,” explains Thometzek.

Such ship loading facilities are not the only places where Thometzek and his colleagues are deployed. They are also to be found in block heat and power plants, biogas plants, smokehouses, painting facilities, coffee roasters, sand drying installations, silos and waste incineration plants, taking measurements to ensure that the air emerging from them is clean. “Wherever things are combusted, heated, dried or ground, wherever solvents are used or vapours released, that’s where we set to work,” explains the expert. In addition to protecting the environment and local residents, they also ensure that people can go about their business without any risk to their health.

Just like today at the ship loading and unloading facility in Moorburg, Thometzek is often deployed out of doors and at dizzying heights. “We take our measurements at the very end of the exhaust air or exhaust gas chain, shortly before the scrubbed process air is released into the environment – and experience shows that this is usually quite a long way up.” After all, they are seeking to establish whether what comes out of a flue is going to endanger human health and pollute the environment. Which is why the experts need not just knowledge and experience but also forbearance in the face of the weather and a good head for heights. Skills that a lot of the environmental engineer’s colleagues bring from their previous occupations. “A lot of chimney sweeps work for us,” Thometzek relates. This is because chimney sweeps do the same kind measuring work in private homes that the experts perform in industrial plants. “A lot of chimney sweeps come to us in search of a challenge: every day they’re faced with different plants with another background, which gives them an opportunity to keep on learning,” the expert says.

For Christian Thometzek, it’s this variety which makes his job so exciting. Moreover, he likes his role as a facilitator between two worlds. After all, on the one hand, he and his team advise and assist operators in their efforts to keep their plants fully up to date and to bear the environment in mind. On the other, they actively work for the public good and will reveal their measurements if unnecessary pollutants are being emitted because a company is playing fast and loose with environmental protection. “We advise both the operators and the public and mediate between these two parties who often have conflicting agendas.”

TV station NDR also followed Christian Thometzek and other TÜV NORD colleagues as they went about their work, and you can watch the gripping report here.