Evaluasi Indeks Slagging dan Fouling pada Boiler Batubara Jenis Lignit dan Bituminus

<p>Batubara saat ini merupakan salah satu jenis bahan bakar yang banyak digunakan padaPLTU. Pada proses pembakaran batubara selain menghasilkan panas juga menghasilkan partikulat abu yang terbawa bersama gas panas. Partikulat abu batubara memiliki kemampuan untuk menempel pada dinding boiler dan kemampuan menempelnya abu ini terutama dipengaruhi oleh suhu melebur abu (ash fusion temperature, AFT) dan unsur – unsur dalam abu.Ada 2 jenis fenomena menepelnya abu batubara pada dinding boiler, yaitu <em>slagging</em> dan <em>fouling</em>. Hal ini akan berdampak pada penggunaan batubara menjadi lebih banyak dan meningkatkan pekerjaan pemeliharaan boiler. Metode evaluasi indeks <em>slagging</em> dan <em>fouling</em> mengunakan analisa karakteristik batubara melalui perhitungan indeks <em>slagging</em> dan <em>fouling</em>. Analisa karakteristik batubara dengan menggunakan analisis komposisi abu (SiO2, Al2O3, Fe2O­3, CaO, MgO, K2O, Na2O, TiO2, MnO2), ash fusion temperature, analisis proksimat (Kadar air, abu, zar terbang, dan karbon padat), analisis ultimat(C, H, S, N), dan penentuan nilai kalor batubara. Penelitian ini menggunakan metode perhitungan dengan menggunakan data analisa dari batubara,yaitu analisa proksimate, ultimate dan ash fusion temperature. Berdasarkan evaluasi dan analisa yang diperoleh bahwa abu jenis bituminous dengan kandungan unsur Fe2O3 memiliki pengaruh pada indeks pembentukan <em>slagging</em> dengan hasil indeks <em>slagging</em> lebih rendah, dan abu jenis lignit dengan unsure kandungan CaO dan MgO sangat mempengaruhi besar nilai indeks pembentukan <em>slagging</em> dengan hasil indeks <em>slagging</em> lebih tinggi jika dibandingkan dengan batubara jenis bituminus. Begitujuga halnya dengan kandungan Na2O pada abu bituminous dan lignit menjadi unsur yang berpengaruh ini selain indeks pembentukan <em>fouling</em>.</p>

A Model for Predicting Arsenic Volatilization during Coal Combustion Based on the Ash Fusion Temperature and Coal Characteristic

Arsenic emission from coal combustion power plants has attracted increasing attention due to its high toxicity. In this study, it was found that there was a close relationship between the ash fusion temperature (AFT) and arsenic distribution based on the thermodynamic equilibrium calculation. In addition to the AFT, coal characteristics and combustion temperature also considerably affected the distribution and morphology of arsenic during coal combustion. Thus, an arsenic volatilization model based on the AFT, coal type, and combustion temperature during coal combustion was developed. To test the accuracy of the model, blending coal combustion experiments were carried out. The experimental results and published data proved that the developed arsenic volatilization model can accurately predict arsenic emission during co-combustion, and the errors of the predicted value for bituminous and lignite were 2.3–9.8%, with the exception of JingLong (JL) coal when combusted at 1500 °C.

Statistical Model for Prediction of Ash Fusion Temperatures from Additive Doped Biomass

The prediction of phase transformation of biomass ashes is challenging due to the highly variable composition of these fuels as well as the complex processes accompanying phase transformations. The AFT (Ash Fusion Temperature) model was performed in Statistica 13.1 software. This model was divided into three separate submodels, which were designed to predict the characteristic ash melting temperatures for raw and modified biomass. It is based on the chemical composition of fuel and ash as obtained using ash analysis standards. For the discussed models, several coefficients describing multiple regression parameters are presented. The AFT model discussed in this article is suitable for predicting ash fusion temperatures for biomass and allows for the prediction of the temperature with an average error of <±70.05 °C for IDT; <±51.98 °C for HT; <±47.52 °C for FT for raw biomass. For some of the additionally tested biomass, a value higher than the average difference between the measured temperature and the designated model was observed (<90 °C). Moreover, morphological analyses of the structure SEM-EDS for ash samples with and without additive were performed.

Geopolymer Preparation from Bamboo Ash Containing Kaolin as Ash Fusion Control Agent

Bamboo is a prospective biomass fuel due to its high heating value and growth rate. The addition of kaolin is necessary in the thermal conversion of biomass to increase its ash fusion temperature (AFT), thus reducing fouling and corrosion of the combustion system. This study evaluates the feasibility of utilizing bamboo-kaolin co-processing residue for geopolymer synthesis. Thermochemical calculations suggest that bamboo culm ash liquidus increases by 15% by adding kaolin during combustion at a biomass to kaolin mass ratio of 95:5%. A 23 full factorial experiment measures the effect of activator Na2SiO3:KOH ratio, KOH concentration, and heat-curing period at 60 °C on the early strength of geopolymer mortars. Co-processing residue of bamboo-kaolin at a mass ratio of 95:5% produces geopolymer mortars with compressive strengths in the 10.7-40.3 MPa range. ANOVA treatment of the data indicate strong positive effect of KOH concentration. Crystalline phase characterizations indicate that the co-processing is able to convert kaolin to the amorphous, more reactive metakaolin. A shift in the IR absorption band from 1034 to 1008 cm-1 is attributed to the conversion of Si-O-Si bonds of the co-processing residue into Si-O-Al and Si-O-K bonds of the geopolymer gel phase. These results suggest the feasibility of geopolymerization as a waste valorization pathway to ensure the sustainability of the biomass-based energy production.

Effects of Pyrolysis Temperature and Retention Time on Fuel Characteristics of Food Waste Feedstuff and Compost for Co-Firing in Coal Power Plants

Food waste is an underutilized organic resource given its abundance and high potential energy. The purpose of this study was to confirm the suitability of pyrolyzed food waste as a co-firing fuel by adjusting the pyrolysis temperature (300–500 °C) and retention time (15–60 min). Both high moisture (compost) and low moisture (feedstuff) food waste were examined. Increasing the temperature and retention time yielded more volatile H and O as well as C sequestration, resulting in reduced H/C and O/C ratios. Notably, the van Krevelen diagram increased in similarity to that of coal. Upon pyrolyzing food waste compost, more than half of the chloride was volatilized, the highest carbon content of the compost and feedstuff were 61.35% and 54.12%, respectively, after pyrolysis at 400 °C for 60 min; however, the calorific value of the pyrolyzed feedstuff was reduced owing to the high salt concentration. The pyrolyzed compost and feedstuff had high Ca contents, which contributed to an increased ash fusion temperature. Therefore, food waste byproducts are advantageous as co-firing fuels in terms of energy regeneration. Nevertheless, further research is required regarding the removal of salt and alkali earth metal ion materials.