Mechanical Technology may 2015

⎪ Proactive maintenance, lubrication and contamination management ⎪

Urgent! Upgrading SA’s air pollution systems

Because of Eskom’s focus on the backlog of essential maintenance on the generation side, the legal requirements for improved emission control at South African power plants have been shelved for a further five years. MechTech talks to Clyde Bergemann Africa’s Themba Masimula, senior sales engineer and Jeremy Kirsch, executive director, about the company’s air pollution control solutions.

Citing a German power station that receives coal from 124 different sources, he relates that as each load of coal comes in, by rail or barge, a sample is taken and analysed before determining where to stockpile the delivery. “The coal is blended to achieve consistency in terms of calorific value and ash. This makes it easier to control the power sta- tion’s output and its emissions. But coal for Tutuka, for example, is delivered by 1 000-odd trucks per day. This makes it very difficult to look ahead and manage the coal quality and consistency. Power station managers don’t always know where the coal is from and are faced with the impossible task of achieving consistency,” says Kirsch. ESP upgrades, an interim solution Describing Clyde Bergemann Africa’s response to the problem, Masimula says that well designed and maintained ESPs should be able to control particulate emissions to below 100 mg/Nm 3 . “For the foreseeable future, we still need to carry on using ESPs, but we can’t con- tinue to use the existing units with dated technology without the quantity of ash going up the stacks increasing dramati-

at our power plants are failing,” warns Kirsch, “and anyone can see this from Google Earth,” he says showing a current image of the Duvha power station. “I call this ‘the tail of two stacks’. Half of the Duvha units have fabric filters, which work relatively well, while the other half have electrostatic precipitators (ESPs),” he points out. Smoke is seen pouring out of one of the stacks, while the other looks reactively clean. “150 mg/Nm 3 is permissible under the current license, but few stations are achieving anywhere near that,” he suggests, adding that most power sta- tions with ESPs are emitting more than 200 mg/Nm 3 on a regular basis. “The bag filters are running quite well, but at stations with ESPs such as Tutuka and Lethabo, all the emission stacks are bad,” Kirsch believes. The reasons? “Mostly maintenance, although the coal quality, with its high ash content, and multiple-supplier purchasing policies do not help,” he responds. “The coal industry has been opened up, which has lead to wider toler- ances and more mixed coal quality. This creates havoc in the furnace and with the pollution control technologies,” he says.

Clyde Bergemann Africa’s Themba Masimula, senior sales engineer and Jeremy Kirsch, executive director.

A ccording to the DEA’s National Environmental Management: Air Quality Act 39 of 2004, as amended according to the Air Quality Amendment Act 20 of 2014, solid particulate emissions levels in in- dustrial environments are reduced to no more than 100 mg/Nm 3 from April 2015. “Unfortunately though,” says Kirsch, “the Act also makes provisions for ‘exemptions’ and last year Eskom put in an application for exemptions for all South African power stations. This appli- cation was granted on Tuesday February 24, 2015, which means that Eskom is effectively exempt from meeting nation- ally binding emission limits for a further five years,” he reveals. This five-year exemption period takes the utility to the 2020 requirements, which halve emis- sion limits again, down to the ultimate goal of 50 mg/Nm 3 . “The air pollution control systems

Clyde Bergemann’s retrofitted pulse jet fabric filters feature: a patented stepped inlet manifold design for uniform gas distribution and reduce pres- sure drop; a patented inlet vane system to uniformly distribute gas flow and reduce bag wear; lower total pressure drop, which reduces I.D. fan power consumption and operational costs.

Clyde Bergemann offers proven wet and dry ESP technology which feature: a low maintenance design with an electromagnetic rapping system located outside the gas stream; a rigid (Rigitrode ® ) anode design; and Modulok TM collecting electrode plates that overcome distortion for improved plate alignment and structural integrity.

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Mechanical Technology — May 2015