S018_PROC-852.2015

ACHEMA Worldwide News2/2015

Worldwide News Could “surplus” electricity be put to work in flexible chemicals production capacities that are switched on and off according to energy availability? As the share of renewable energy grows, the volatility of the energy supply increases as well. Germany with its “Energiewende” (energy turnaround) is at the vanguard of this challenge, but other countries globally are pushing forward the installation of solar parks or wind power plants, and they will face the same issues. In the past, storage technologies have been in the focus, and they are still being developed at high pace. But recently, some other ideas have been put forward that address the demand side of the energy equation. The chemical industry has a number of processes that can be driven either by electricity or by other means; therefore, it seems predestined to play an important role in “demandside management”. Electrolysis ranks high among them; for example, the capacity for chloralkalielectrolysis in Germany alone is five million tons per year, corresponding to a connected wattage of 1,450 MW, and is already partly used to level peaks in electricity generation. Compared to batteries or physical storage, there is an efficiency gain if the electrolysis is performed at low current denELECTRIFYING IDEAS • The part of the plant that is run with flexible load should have the lowest investment cost (usually the reactor). • All following steps (especially product purification) should be designed for continuous loads according to the maximum sales volume expected. • This means that raw product needs to be stored. The investment is comparably low, but for dangerous chemicals legal permits will set limits. • The downstream process should be located close by to avoid additional transport cost. • The whole process chain has to be designed so that even if all raw product is transferred to storage, storage capacity is not exhausted. • Fluctuating operation may not be dimensioned for 100 % product sales as storage capacity for the raw product cannot be adjusted freely to all situations on the electricity market. This list shows that in order to decide on the viability of a flexible process, the whole system has to be analyzed. The selected processes have to be highly dynamic. The Role of Electrochemistry “Classical” water electrolysis is the basic element of many powertoxconcepts for the production of hydrogen, methane sity, and the chemical product has a higher energy density. But as for all large chemical plants, the primary goal is to maximize capacity utilization. If plants are made more flexible, however, they have to be dimensioned above their average sales volume, and interim storage has to be installed. Due to the current small prize spread on the energy market, this is usually not economically viable if there is no additional compensation. The same is true for the flexibilization of most continuous processes. Usually batch processes offer more flexibility as the starting point can be chosen without changing other process parameters. This applies universally and is not restricted to electrochemical processes as electricity is used for heating and cooling, compacting and pumping as well. The generation of steam (powertoheat) is also an option that can be relatively easily implemented and is in use at a couple of locations in Germany. New Processes — Input of Thermal Energy In addition to existing plants and processes, a number of other options are currently discussed, preferably for largescale operations. The aspects to be considered include: This article is based on the “Diskussionspapier Elektrifizierung Chemischer Prozesse” published by DECHEMA in March 2015. It is available for download at (German language only): http://dechema.de/studien.html 18 A special edition from PROCESS


ACHEMA Worldwide News2/2015
To see the actual publication please follow the link above