Swedish plant installs Alfa Laval Compabloc heat exchangers

The five Alfa Laval Compabloc heat exchangers are installed in the benzene recovery part of the SSAB coke oven plant. Prior to installing the Compabloc units, SSAB had used other types of heat exchangers. However, the company decided to look for alternative solutions to try to reduce the intensive maintenance requirements. The choice lay between spiral heat exchangers and Compablocs. Spiral heat exchangers have a solid reputation within the coke oven gas process industry, so SSAB was initially hesitant to use the lesser-known Compabloc type. However, the company finally decided on the compact Compabloc solution because it was more cost-effective. This was an especially important issue because it was necessary to use titanium, for its corrosionresistant properties. The result, according to maintenance engineer Helmut Moser, is that “The Compabloc heat exchangers just keep on running with only a minimum of maintenance.” 

Three of the Compabloc heat exchangers were installed to cool the regenerated wash oil before it enters the scrubbing tower. Sea water is used as a coolant. One of these heat exchangers was installed in 1994 and the other two the fol-lowing year. To remove the BTX fractions (benzene, toluene and xylene) from the coke oven gas, wash oil is sprayed over the gas in a gas-scrubbing tower. The wash oil is regenerated in the light oil stripper where BTX fractions are removed. The vapours that come from the stripper contain BTX (mainly ben-zene). These are condensed and the condensate is then pumped to the distillation tower for further refining. Distillation column light oil preheater PPI00039EN 1904 The fourth Compabloc unit was installed in 1999 and replaced the old traditional pipe oven, with coke oven gas as the heating media. This Compabloc was installed to preheat the spent wash oil going to the stripper, where the heating media is steam. The Compabloc has operated without any problems since start-up and no mechanical cleaning has been necessary. At the same time as SSAB bought the fourth Compabloc, the company also purchased an identical spare unit for the pipe oven, a square brick building that is 7 metres in height, with a footprint of 25 m2. Helmut Moser comments, “Since the steam heater was running so well, we felt confident that we wouldn’t need the spare unit, so we started looking for another place to put it.” The pipe oven had a second pipe used for heating the condensed raw benzene before going to distillation. According to Helmut Moser, the company has achieved energy savings of 30% in the distillation step by installing the spare Compabloc as a raw benzene heater. In addition, the Compabloc made it possible to obtain better quality benzene. This Compabloc has been in operation since 2002 and is running without any problems. As a result of the safe operation of the two Compablocs used as preheaters, SSAB has now disassembled the pipe oven and removed it from the site.