Yoğuşmalı kazanlarda, hidrojen takviyeli doğalgaz kullanımının verimlilik, performans ve güvenliğe olan etkilerinin deneysel olarak incelenmesi = Experimental ınvestigation of the effects of hydrogen-enriched natural gas usage on efficiency, performance, and safety in condensing boilers

Abstract

Gaz sektörünün karbondan arındırılması için en umut verici alternatif yakıtlar biyogaz ve hidrojendir. Fosil yakıtları karbon içermeyen yakıtlarla değiştirmek, nihai karbon nötrlüğü hedefine ulaşmak için önemli bir adımdır. Doğrudan mevcut doğal gaz enerji sistemlerinden saf hidrojene geçmek yerine, doğal gaza kademeli olarak hidrojen takviye edilmesi, sorunsuz bir geçiş sağlayabilir. Birçok ülkede tartışma ve kısmi uygulama aşamasında olan doğal gaz sistemlerine belli oranlarda hidrojen ilave edilmesi konusu, Türkiye doğalgaz sektörü tarafından yoğun bir şekilde takip edilmektedir. 157 bin kilometrelik şebeke uzunluğu ve Avrupa'nın en büyük altıncı gaz dağıtım şebekesine sahip Türkiye genç, modern dağıtım şebekesi ve düşük kayıp oranları ile hidrojen ekonomisine geçişin en kolay sağlanabileceği ülkelerden biri olacaktır. Bu tez çalışmasında, ülkemizde ev ve ticari binaların ısıtılmasında kullanılan yoğuşmalı kazanlarda, belli yüzde oranlarında hidrojen takviyeli doğalgaz kullanımının etkilerinin incelenmesi amaçlanmıştır. Tez kapsamında, günümüzde geçerli olan Avrupa Normlarına uygun şekilde tasarlanmış ve üretilmiş duvar tipi yoğuşmalı kombinin sahada doğalgaz yerine %20 hidrojen takviyeli doğalgaz ile kullanılmasının olası etkilerinin hem teorik hem de deneysel olarak incelendi. Teorik inceleme kapsamında, şebeke gazına belirli oranlarda hidrojen ilavesinin yakıt olarak kullanılan gazın fiziksel özelliklerine olası etkileri değerlendirildi. Ayrıca hidrojen takviyeli yakıt kullanımının ürünün performans ve güvenliğini etkileyebilecek olan sitokiyometri, alev hızı ve baca gazı emisyonlarında yaratacağı olası etkiler incelendi. Teorik incelemenin akabinde deneysel çalışmaya hazırlık kapsamında test edilecek ürün ve test düzeneği tanıtıldı, yapılan hata modu ve etki analizi sonucunda planlanan testlerin amaç ve koşulları açıklandı. Tezin konusuna uygun olarak planlanan testler yapıldı. Bu test sonuçları, şebeke hazına hidrojen takviyesinin ürün performansına, ürünün devreye alınmasına, ürün ve kullanıcı güvenliğine diğer bazı hususlara olası etkileri göz önüne serecek şekilde yorumlandı. Sonuç olarak, günümüzde geçerli olan standart ve regülasyonlara uygun olarak ve sahada doğalgaz ile çalışmak üzere tasarlanan ve üretilen duvar tipi kombilerin, sahada saf doğalgaz yerine %20 hidrojen takviyeli bir karışım gazıyla çalışmasının ürün performansına olan olumsuz etkilerinin göz ardı edilebilecek kadar az olduğu ve ayrıca bu durumun ürün ve kullanıcı güvenliğini de tehlikeye sokacak bir etkisi bulunmadığı tespit edildi.

Climate change is one of the most critical global issues of our time. Natural gas is one of Europe's primary energy sources today, used in various sectors including electricity generation, industry, and individual consumption. Since natural gas is a fossil fuel, it is known to be significantly responsible for CO2 emissions, a greenhouse gas. The most promising alternative fuels for decarbonizing the gas sector are biogas and hydrogen. Producing hydrogen from electricity obtained from renewable energy sources and water allows not only meeting energy demands but also storing the produced energy by keeping hydrogen in a liquid state. Replacing fossil fuels with carbon-free fuels is an essential step towards achieving ultimate carbon neutrality. Gradually adding hydrogen to natural gas instead of switching directly from existing natural gas energy systems to pure hydrogen can ensure a smooth transition. The addition of hydrogen to natural gas systems, a topic currently under discussion and partial implementation in many countries, is being closely monitored by the Turkish natural gas sector. With a network length of 157,000 kilometers and Europe's sixth-largest gas distribution network, Turkey, with its young, modern distribution network and low loss rates, will be one of the easiest countries to transition to a hydrogen economy. The purpose of this thesis is to theoretically and experimentally examine the effects of using hydrogen-blended natural gas on the efficiency, performance, and safety of condensing wall-mounted boilers by selecting a model currently sold in Turkey and Europe and designed and certified to be compatible with natural gas. It is known that the fuel and combustion properties of the new mixture will change compared to pure natural gas when hydrogen is added to natural gas. Considering that methane and hydrogen have significantly different chemical and physical properties, the increase in hydrogen addition to natural gas will lead to changes in the combustion process due to changes in fuel properties. Within the scope of the thesis, the possible effects of using 20% hydrogen-blended natural gas instead of natural gas in a wall-mounted condensing combi boiler designed and produced in accordance with current European Norms were examined both theoretically and experimentally. In the theoretical examination, the possible effects of adding hydrogen to the network gas on the physical properties of the gas used as fuel were evaluated. In addition, the possible effects of using hydrogen-blended fuel on the product's performance and safety, including stoichiometry, flame speed, and flue gas emissions, were examined. Following the theoretical examination, the product to be tested and the test setup were introduced, and the purposes and conditions of the planned tests were explained as a result of the failure mode and effects analysis conducted. Tests planned in accordance with the subject of the thesis were carried out. These test results were interpreted to reveal the possible effects of hydrogen addition to network gas on product performance, product commissioning, product and user safety, and other aspects. In the theoretical examination, it was predicted that the calorific value of hydrogen gas is lower than that of methane, thus the thermal power obtained from the mixture gas would decrease. A 5% difference was calculated between the Wobbe indices of 100% CH4 and gas mixtures containing 20% H2. Therefore, it was expected that the thermal power would decrease by at least 5% under complete combustion conditions. As a result of the tests, it was observed that the thermal power decreased by 5% at minimum capacity and 4.0% at maximum capacity. Accordingly, the results of the theoretical examination and experimental study are consistent. In the theoretical examination, it was predicted that CO2 emissions would decrease in parallel with the reduction in the proportion of methane, a carbon-based fuel, in the combustion reaction, and this was confirmed by the test results. Accordingly, the results of the theoretical examination and experimental study are consistent. Regarding CO emissions, the prediction was that they would decrease due to the increasing excess air coefficient, provided the flame remains stable. During the tests, it was confirmed that the increased excess air coefficient did not negatively affect flame stabilization, and the flame was formed stably, thus not increasing CO emissions. Therefore, it was observed that CO emissions decreased as predicted. Accordingly, the results of the theoretical examination and experimental study are consistent. The prediction regarding NOx formation in the theoretical examination was that NOx emissions would be more dependent on combustion chamber temperatures and the presence of oxygen in these hot regions rather than fuel content. Although the expectation was for a decrease, it was more in need of confirmation compared to CO and CO2 emissions. The tests showed that the already high excess air coefficient further increased with hydrogen addition, balancing the adiabatic combustion temperatures that would rise due to fuel properties, and resulting in a decrease in NOx emissions. Accordingly, the results of the theoretical examination and experimental study are consistent. In the theoretical examination, it was expected that increasing the hydrogen ratio in the combustion gas would lead to different effects, both reducing and increasing efficiency. The extent to which these effects would balance each other could not be predicted. The calculated combustion efficiencies for pure natural gas and the mixture gas from the test results were almost the same. Therefore, as predicted, the efficiency-increasing and decreasing effects balanced each other, and adding 20% hydrogen to the fuel did not positively or negatively affect the combustion efficiency of the device Flame flashback tests were successfully conducted, and no issues were observed It was observed that adding 20% hydrogen to natural gas did not create a measurable leakage risk. As a result, it was determined that the negative effects of operating wall-mounted boilers designed and produced to work with natural gas in the field with a 20% hydrogen-blended mixture gas on product performance are negligible and that this situation does not pose a risk to product and user safety.