Noriyuki Okuyama

Solvent de-ashing from heavy product of brown coal liquefaction using toluene:: 2. concentration and separation of ash with a continuous de-ashing system

The brown coal liquefaction (BCL) process is a two-stage liquefaction (hydrogenation) process developed for Victorian brown coal in Australia. The BCL process has a solvent de-ashing step to remove the ash and heavy preasphaltenes from the heavy liquefaction product (vacuum residue) derived from the coal in primary hydrogenation and named CLB (coal liquid bottom). This solvent de-ashing step uses toluene or coal-derived naphtha as a de-ashing solvent (DAS). After dissolving the CLB into the solvent (CLB/solvent ratio, 1/8–1/4, w/w) under high temperature (200–290°C) and high pressure (4–5 MPa), insoluble solid particles which consist of ash and heavy preasphaltenes are settled by gravity and separated from the solution as an ash-concentrated slurry. The ash-concentrated slurry and the de-ashed solution are withdrawn from the settler as an underflow and overflow, respectively. The de-ashed heavy product is recovered from the solution by eliminating the solvent and is further hydrogenated in secondary hydrogenation. The authors have reported on the solubility of CLB in toluene and the settling velocity (V) of the boundary of ash content in the settler under de-ashing conditions. This paper discusses the effects of de-ashing conditions on ash concentration in the settler bottom and the operating conditions of a continuous de-ashing system. The ash content in underflow (CUF, kg/kg or wt.%) at the settler bottom was found to increase with temperature and to decrease with the rate (flux) of downward flow (underflow). The maximum CUF, Z, is expressed by the equation: Z=BCLB(FL/0.35)−0.32(T/523)4.26, where BCLB, FL and T are the characteristic parameters of organic CLB (kg/kg or wt.%), flux of underflow in the settler (kg/m2 s) and temperature (K), respectively. BCLB is also expressed by using the analytical results of organic insolubles in the CLB under de-ashing conditions. Finally, stable operating conditions of a continuous de-ashing system are confirmed to be determined as the following qualifications: |Vu| WSA/CUF and Z>CUF, where |Vu|, |V|, WSA and WUF are the upward velocity of the solution in the settler (mm/s), settling velocity of the ash boundary (mm/s) in the settler, flow rate of ash in the feed slurry (kg/h) and flow rate of underflow (kg/h), respectively. Under these qualified conditions, the 50 t/d pilot plant constructed in Australia was operated under stable conditions for 3700 h using toluene as a DAS.

Study on the Hyper-coal Process for Brown Coal Upgrading

ABSTRACT The Hyper-coal process is a coal refinery process that makes an ash-free coal by thermal extraction and solid-liquid separation technology. This study investigates the upgrading of brown coal by applying the Hyper-coal process. Several kinds of bituminous, sub-bituminous, and brown coals were thermally extracted with 1-methynaphthalene using a high temperature-extraction/filtration unit. As a result of these coal extraction tests, Hyper-coal (HPC) yields of more than 60% weight (daf) were obtained from the bituminous coals, but less than 30% weight (daf) were obtained from brown coals. Hyper-coal contains negligible ash (<500 PPM) and high heat value (>8000 kcal/kg). In addition, the excellent thermal plasticity of this product may facilitate metallurgical applications, such as coke binder. In the case of brown coal, the ash content in the insoluble coal is less than 5%, since the parent coal has only 3% ash. In addition, the elimination reaction of the oxygen containing functional groups yields a substantial increase in heat value. Thus, the Hyper-coal process is an effective way to upgrade brown coals, producing not only ash-free coal but also low ash and high heat value coal.

Solvent de-ashing from heavy product of brown coal liquefaction using coal-derived naphtha

The brown coal liquefaction (BCL) process is a two-stage liquefaction (hydrogenation) process developed for Victorian brown coal in Australia. In this process, the heavy liquefaction product (vacuum residue) derived from the coal in primary hydrogenation, which is named CLB (coal liquid bottom), is treated in a solvent at high temperature (200–290°C) and high pressure (5 MPa) to remove the ash and heavy preasphaltenes (solvent de-ashing). This solvent de-ashing step uses toluene or coal-derived naphtha as a de-ashing solvent. After dissolving the CLB into the solvent, insoluble solid particles which consist of the ash and heavy preasphaltenes are settled by gravity and separated from the solution as an ash-concentrated slurry. The de-ashing efficiency (recovery of the heavy product and rate of ash removal) depends on the operating conditions and the properties of CLB and solvent, because they affect the extract yield from CLB, the settling velocity and concentration of the ash in the settler. This paper describes the stable operating conditions of the de-ashing plant using a coal-derived naphtha produced in the primary hydrogenation by discussing the effects of such parameters on the de-ashing efficiency. The de-ashing experiments with batch and continuous systems using the naphtha were carried out to determine the extract yield from CLB (eCLB), the settling velocity of the ash boundary (VNP) and the maximum ash content (ZNP) in underflow of the settler under the de-ashing conditions. According to the results of these experiments, the equations expressing eCLB, VNP and ZNP are introduced by using the de-ashing conditions, the naphtha density and the properties of CLB expressed by analytical results of ash content and solvent extraction. The stable operating conditions of a continuous de-ashing system using coal-derived naphtha can be fixed by determining the upward velocity of solution in the settler, and the flow rates of ash in underflow and feed slurry based on the predictions of these equations.

Prebaked Anode from Coal Extract (3) — Carbonization Properties of Hypercoal and Its Blends with Binder Pitch

The preparation of prebaked anodes from coal using solvent extraction technology was investigated. Several bituminous coals were extracted with methylnaphthalene-based solvent under pressurized nitrogen atmosphere at 653K, and ash-free and high purity coal extract (Hypercoal, HPC) was obtained. It was found that the HPC can be utilized as an additive for binder pitch of anode manufacturing; the HPC improves the coke yield of the pitch and reduces the ash content of the binder. It was also found that a suitable modified HPC was self-sinterable, and was successfully molded and carbonized without binder pitch to result of dense carbon specimen. These results suggest the possibility for coal-based raw materials for prebaked anodes

Prebaked Anode From Coal Extract (2) - Effects of the Properties of Hypercoal-Coke on the Preformance of Prebaked Anodes

The preparation of prebaked anodes utilizing coal solvent extraction technology is reported. A steaming coal was extracted with methylnaphthalene-based solvent under pressurized nitrogen atmosphere at 653K, and ash-free coal extract (Hypercoal, HPC) was obtained. The HPC was further heat-treated at 633 to 673 K in the presence of the methylnaphthalene solvent to alter the carbonizing properties of HPC. It was found that adjusting the H/C atomic ratio of HPC in the range 0.6-0.65 suppressed excess dilatation ability of the HPC and produced anode-quality coke. The effect of heat treatment temperature of the HPC on the resultant properties of the HPC coke (HPCC) was also investigated. It was confirmed that HPC is a suitable source of anode coke due to the low content of impurities such as sulfur, nickel, vanadium, and good chemical stability.