As part of the ener­gy trans­for­ma­ti­on, a reduc­tion in CO₂ emis­si­ons is essen­ti­al in ther­mal pro­cess tech­no­lo­gy too. In addi­ti­on to opti­mi­sing the hea­ting sys­tems curr­ent­ly used, which are based on fos­sil fuels, this requi­res abo­ve all a trans­for­ma­ti­on to alter­na­ti­ve con­cepts. Elec­tric hea­ting sys­tems are one opti­on for CO₂-neu­tral hea­ting, pro­vi­ded that no fos­sil fuels are used to gene­ra­te the elec­tri­ci­ty. In the field of pro­cess heat gene­ra­ti­on, howe­ver, the­se elec­tric hea­ting sys­tems are curr­ent­ly only available in small num­bers or limi­t­ed to spe­cial appli­ca­ti­ons (e.g. elec­tric arc fur­naces). Resis­tance hea­ting in par­ti­cu­lar offers the pos­si­bi­li­ty of being used in a wide ran­ge of sys­tems. At pre­sent, the­re are still seve­ral ques­ti­ons regar­ding the wide­spread use of resis­tance hea­ting. The “Sus­tainable elec­tri­fi­ca­ti­on of ther­mal pro­ces­sing plants — Ena­bEL” pro­ject pur­sues the over­ar­ching objec­ti­ve of expan­ding the ran­ge of elec­tri­fi­ca­ti­on of ther­mal pro­ces­sing plants (indus­tri­al fur­naces) through resis­tance hea­ting. Over­all, the pro­ject is made up of the three clo­se­ly inter­lin­ked sub-pro­jects “High­PowHeat”, “OptiEL­Heat” and “MatE­L­Heat” and focu­ses pri­ma­ri­ly on expan­ding the scope of appli­ca­ti­on of resis­tance hea­ting sys­tems in plants with plant power capa­ci­ties of gene­ral­ly < 1 MW to date to power capa­ci­ties of up to 10 MW or more.

Sub-pro­ject 1: High­PowHeat — Fea­si­bi­li­ty stu­dies for high elec­tri­cal con­nec­ted loads in ther­mal pro­ces­sing plants with resis­tance heating

Sub-pro­ject 2: OptiEL­Heat — Opti­mi­sed ther­mal design of powerful elec­tri­cal resis­tance hea­ting sys­tems for con­vec­tion-domi­na­ted ther­mal pro­ces­sing plants

Sub-pro­ject 3: MatE­L­Heat — Inves­ti­ga­ti­ons into the mate­ri­al-tech­ni­cal design of elec­tri­cal resis­tance hea­ting sys­tems for hybrid-hea­ted ther­mal pro­ces­sing plants

Resis­tance hea­ting ele­ments in a furnace

As alre­a­dy descri­bed, the covera­ge of this exten­ded out­put ran­ge is neces­sa­ry for the objec­ti­ves of the ener­gy trans­for­ma­ti­on. Plants that are cha­rac­te­ri­sed by low out­puts, a less com­plex struc­tu­re, simp­le pro­cess con­trol requi­re­ments, no flue gas sys­tem and short ope­ra­ting times per year are alre­a­dy elec­tri­fied. In con­trast, lar­ge indus­tri­al plants are cha­rac­te­ri­sed by signi­fi­cant­ly hig­her instal­led elec­tri­cal out­puts and long annu­al ope­ra­ting times. This results in requi­re­ments for resis­tance-based hea­ting ele­ment sys­tems for use in exten­ded power ran­ges (e.g. power input, ope­ra­ting time, H₂-rich atmo­sphe­res), which must be inten­si­ve­ly inves­ti­ga­ted. One exam­p­le of this is the over­hea­ting of the indi­vi­du­al hea­ting ele­ments. Loca­li­sed over­hea­ting often leads to pre­ma­tu­re fail­ure of the ele­ments and should the­r­e­fo­re be avo­ided whe­re­ver pos­si­ble. For this reason, the elec­tri­cal ener­gy sup­p­ly and the sub­se­quent heat exch­an­ge via the sur­face of the ele­ments are being inves­ti­ga­ted in the “High­PowHeat” and “OptiEL­Heat” sub-pro­jects. At the same time, over­hea­ting and the resul­ting local rise in tem­pe­ra­tu­re also leads to incre­asing oxi­da­ti­on of the hea­ting ele­ment mate­ri­als. This in turn leads to dama­ge to the ele­ments. The effects of the tem­pe­ra­tures and atmo­sphe­res on the mate­ri­als of the hea­ting ele­ments are being inves­ti­ga­ted in the “MatE­L­Heat” sub-project.

Given this back­ground, the aspect of lon­ger usa­bi­li­ty of the ele­ments plays a decisi­ve role in the three sub-pro­jects of the lead tech­no­lo­gy pro­ject, along­side an increase in per­for­mance. The­se objec­ti­ves can­not be inves­ti­ga­ted and rea­li­sed inde­pendent­ly of each other, but requi­re a holi­stic view of

• the power sup­p­ly and power elec­tro­nics of the hea­ting ele­ments with hig­her vol­ta­ges as well as the opti­ons of a sup­p­ly with alter­na­ting vol­ta­ge (AC) or direct vol­ta­ge (DC) (sub-pro­ject 1, HighPowHeat),
• the ther­mo-/elec­tri­cal design of the hea­ting ele­ment sys­tems or hot gas gene­ra­tors inte­gra­ted into the fur­naces (sub-pro­ject 2, OptiEL­Heat) as well as
• the ser­vice life of hea­ting ele­ment mate­ri­als for purely elec­tric, but also for hybrid ope­ra­ti­on (com­bi­ned electric/fossil ope­ra­ti­on as a bridging tech­no­lo­gy or later H₂/electricity) (sub-pro­ject 3, MatELHeat).

The know­ledge gai­ned in the lead tech­no­lo­gy pro­ject will be sum­ma­ri­sed in a joint gui­de­line at the end of the pro­jects in order to enable an impro­ved design and opti­mi­sed ope­ra­ti­on of the hea­ting ele­ments and thus expand the pos­si­ble appli­ca­ti­ons in ther­mal pro­cess technology.