Direct Liquefaction of Brown Coal Using a 0.1 Ton/Day Process Development Unit: Effect of Hydrothermal Treatment on Scale Deposition and Liquefaction Yield

Abstract

Scale deposition is a very troublesome problem for a long-term stable operation of a direct coal liquefaction plant. The scale reduction effect of hydrothermal treatment (HTT) for a brown coal liquefaction was investigated using a 0.1 ton/day process development unit (PDU). It was found that the amount of scale formed was reduced by half compared to non-treated coal when HTT coal treated at 325 °C was liquefied. This was because most carboxyl groups were decomposed and exchangeable cations, such as Ca and Na, precursors of the scale, such as CaCO 3 and NaCl, were reduced during HTT. Furthermore, the formation of scale comprising Fe 1−x S and SiO 2 was also suppressed by HTT probably because of a decrease in the amounts of NaCl and CaCO 3 . Liquefying the HTT coal slightly decreased the oil yield compared to the non-treated coal. However, this disadvantage is compensated by the increase in the space time yield of the reactors liquefying HTT coal, because the coal concentration of the HTT coal−solvent slurry fed to the reactors can be increased from 28 to 42 wt % as a result of the reduction of viscosity, as reported in an our previous paper. The concentrations of major scale precursors in the HTT coal−solvent slurry of 42 wt % coal concentration are lower than those in the non-treated coal−solvent slurry of 28 wt % coal concentration. These results indicate that HTT is an effective pretreatment method not only to realize a long-term stable operation but also to improve the oil productivity of the liquefaction plant.

Modularized production of fuels and other value‐added products from distributed, wasted, or stranded feedstocks

“…It is broadly distributed (Seiple et al, ) and its valorization would provide benefits both from the sale of the products and savings on waste disposal. We recommend initially focusing on non‐supercritical hydrothermal liquefaction as the front‐end for processing the initial candidate feedstocks because of its omnivorism (Elliott, ; Lu, Yang, Wang, & Yang, ), ready scalability (Barreiro, Gómez, Hornung, Kruse, & Prins, ; Inoue, Okuma, Masuda, Yasumuro, & Miura, ), tolerance of wet feedstocks, and demonstrated production of a tractable bio‐oil (Elliott, ; Goudriaan & Peferoen, ) with an attractive greenhouse gas footprint (Connelly, Colosi, Clarens, & Lambert, ) (see Appendix). Examples of feedstocks that have been processed with hydrothermal liquefaction include wood (Zhixia Li et al, ), cellulose (Nan, Shende, Shannon, & Shende, ), microalgae (Barreiro et al, ; Brown, Duan, & Savage, ; Connelly et al, ; Faeth, Valdez, & Savage, ), macroalgae (Zhou, Zhang, Zhang, Fu, & Chen, ), food waste (Anouti, Haarlemmer, Déniel, & Roubaud, ), sewage sludge (Snowden‐Swan et al, ), and municipal solid waste (Chiaberge et al, ).…”

Two-Stage Conversion of Low-Rank Coal or Biomass into Liquid Fuel under Mild Conditions

“…It has been shown that the scale deposition can be minimized by removing minerals and −COOH groups in the coal. 28,29 Because soluble is almost free from mineral matters and contains little oxygen functional groups, as stated above, liquefaction of soluble is expected to minimize the scale deposition. The size of the liquefaction reactor may also be reduced because only soluble is fed to the liquefaction reactor.…”

Effects of Sodium Carbonate Additive on the Hydroliquefaction of a Sub-bituminous Coal with Fe-Based Catalyst under Mild Conditions

“…Direct coal liquefaction (DCL) is one of the feasible Coal-To-Liquid technologies that have been available since the first half of the last century. − Therefore, DCL technology attracts more and more attention for alleviating the oil shortage. China has devoted to R&D the DCL technologies in the past few decades, and by the end of 2008, the first and the largest DCL plant since WWII was completed and operated in Inner Monglia, China, which will produce about 780 000 t/y of diesel fuel, 230 000 t/y of naphtha, and 100 000 t/y of LPG. , The successful running of the industrial DCL plant aroused the interest of many researchers about the DCL technologies. − …”

“…FTIR spectra of HLL and the resulting PAs and ASs from hydroliquefaction without or with FC and NCFC. FTIR spectra of HLL coal (1), PA obtained without catalyst (2), over FC (3) and over NCFC (4), AS obtained without catalyst (5), over FC(6) and over NCFC(7).…”