For years, EVAL Europe has been contracting its engineering projects out to Sweco Belgium in order to be able to focus on its own core business: the production and servicing of EVOH synthetic resin, a barrier material for, inter alia, food packaging.
EVAL has joined the Benchmark Covenant, which in the context of achieving the Kyoto emission standards before 2012, is a commitment to have the most energy-efficient plants and production methods.
Situation
In order to identify potential energy savings in a systematic way, EVAL had a pinch analysis carried out by an external consultant. One of the results of the analysis was the proposal to use top vapours from a distillation column as a heating medium in reboilers of other distillation columns. The current heating medium in these distillation columns is steam, produced in boilers. This reduction in steam supply is an energy saving in the boilers and also reduces CO2 emissions.
Assignment
Sweco has taken care of detailed process studies, simulations and worked out a project-based concept for this reduction and also the realization thereof. The proposal from the energy study only appeared to be feasible after adjustment of the process conditions in the relevant distillation column. For example, the condensation temperature of the top vapours was initially too low to be able to be used in reboilers. Simulations of the distillation column at higher pressures showed however that only a limited increase in the required energy (steam) was necessary in order to maintain the same separation. Moreover, it is further proposed to use the energy of the bottom stream as well as preheating for the feed to the column. Thus the energy from this bottom stream may also be used more usefully in the factory.
Results
The increased pressure in the column required an adjustment of the baffle plates. More efficient baffles were installed, which also resulted in lower power consumption for the distillation column.
The project was carried out on one of the two production lines and at full capacity it saves about 5 tons of steam per hour (~3 MW). A second identical project will then have double the energy savings. This represents a total saving of 10 tons per hour of steam production (6 MW) in the boiler or a reduction of 10,000 tons of CO2 emissions annually.
