EmiH₂: Measurement and Evaluation of Emissions from Glass Melting Furnaces Using Hydrogen as a Fuel

The use of hydro­gen as an alter­na­ti­ve ener­gy source has been incre­asing­ly dis­cus­sed, rese­ar­ched and, in some cases, alre­a­dy tes­ted in recent years. Howe­ver, the use of hydro­gen pres­ents a num­ber of chal­lenges. The pro­vi­si­on of hydro­gen in the neces­sa­ry quan­ti­ties and qua­li­ty, as well as an exten­si­ve sup­p­ly infra­struc­tu­re, are open ques­ti­ons that still need to be cla­ri­fied, in addi­ti­on to the tech­ni­cal fea­si­bi­li­ty and adapt­a­ti­on of the pro­cess chains. In glass pro­duc­tion, the use of hydro­gen is alre­a­dy being inves­ti­ga­ted in a lar­ge num­ber of rese­arch and pilot pro­jects. Pro­mi­sing approa­ches can be obser­ved the­re. The issues men­tio­ned abo­ve must also be addres­sed in this con­text. One point that should not be over­loo­ked is the mea­su­re­ment of emis­si­ons at the glass mel­ting tank. The switch to hydro­gen can redu­ce direct com­bus­ti­on-rela­ted CO₂ emis­si­ons. Howe­ver, emis­si­ons that may ori­gi­na­te from the raw mate­ri­als used, the recy­cled glass used and the com­bus­ti­on reac­tion of hydro­gen (espe­ci­al­ly nitro­gen oxi­des NO_x) must also be taken into account. In the glass indus­try, the­se emis­si­ons must com­ply with the regu­la­to­ry requi­re­ments of the Tech­ni­cal Ins­truc­tions on Air Qua­li­ty Con­trol (TA Luft), be adjus­ted if neces­sa­ry and moni­to­red relia­bly. The emis­si­on limits to be com­pli­ed with refer to a mea­su­re­ment of the dry off-gas. For this pur­po­se, the water vapour is remo­ved befo­re ente­ring the gas ana­ly­ser. The pro­por­ti­on of water vapour in the off-gas increa­ses signi­fi­cant­ly when hydro­gen is bur­ned. If the com­bus­ti­on is done with pure oxy­gen as an oxi­dizer, in what is known as the oxy­fuel pro­cess, the off-gas con­sists almost enti­re­ly of water vapour. This poses major tech­ni­cal chal­lenges for con­ven­tio­nal mea­su­re­ment methods, and the com­pa­ra­bi­li­ty of the mea­su­red values with regard to the legal limit values must be questioned.

The EmiH₂ fun­ding pro­ject deals in detail with emis­si­on mea­su­re­ment and emis­si­on mea­su­re­ment tech­no­lo­gy when using hydro­gen as a fuel, using the exam­p­le of a glass mel­ting tank. In the cour­se of the pro­ject, com­pre­hen­si­ve refe­rence mea­su­re­ments are being car­ri­ed out on a small rese­arch glass fur­nace. The­re, dif­fe­rent ope­ra­ting points can be recor­ded with regard to the fuel used (natu­ral gas/hydrogen) and the raw mate­ri­als used (car­bo­na­te-loa­de­d/­car­bo­na­te-free). At the same time, dif­fe­rent emis­si­on mea­su­ring devices are being tes­ted on a test com­bus­ti­on cham­ber and com­pared with the stan­dard refe­rence method (SRM). The com­bus­ti­on cham­ber can be ope­ra­ted with both natu­ral gas and hydro­gen as fuel gases. In addi­ti­on, it is pos­si­ble to choo­se bet­ween air or pure oxy­gen as the oxi­dizer. In par­al­lel, the dry emis­si­on mea­su­re­ment methods are used to test whe­ther and to what ext­ent water-solu­b­le spe­ci­es in the off-gas, such as SO₂ or NO₂, are washed out in the coo­ler con­den­sa­te. For this pur­po­se, the two spe­ci­es men­tio­ned abo­ve are spe­ci­fi­cal­ly injec­ted into the com­bus­ti­on cham­ber and the con­den­sa­te is exami­ned in the labo­ra­to­ry. The pro­ject focu­ses in par­ti­cu­lar on the design and test­ing of a sui­ta­ble sam­pling device for mobi­le field use for the appli­ca­ti­on of SRM in off-gases from hydro­gen-oxy­fuel com­bus­ti­on. Due to the high water vapour con­tent, the dry off-gas con­sists only of small amounts of oxy­gen and emis­si­ons from the melt and com­bus­ti­on. On the one hand, it is tech­ni­cal­ly dif­fi­cult to gene­ra­te a suf­fi­ci­ent volu­me flow for the gas ana­ly­zers in this case and, on the other hand, the legal limits can no lon­ger be com­pli­ed with when con­side­ring the gas spe­ci­es in per­cen­ta­ge terms. The inno­va­ti­ve mea­su­ring pro­be is desi­gned to enable the tar­ge­ted dilu­ti­on of the off-gas with an inert gas (N₂, CO₂, Ar, etc.) and thus the con­tin­ued use of SRM devices. The mea­su­ring prin­ci­ple will first be tes­ted in a test com­bus­ti­on cham­ber and, if suc­cessful, con­ver­ted for mobi­le use.

Upon com­ple­ti­on of the pro­ject, in addi­ti­on to a tes­ted pro­to­ty­pe of the mobi­le sam­pling device, com­pre­hen­si­ve recom­men­da­ti­ons for action will be made for the fur­ther deve­lo­p­ment of the mea­su­re­ment tech­no­lo­gy as well as for the inte­gra­ti­on of the mea­su­re­ment method into the appli­ca­ble stan­dards and its pos­si­ble certification.