A Simulation of the Accumulation of Solid Particles in Coal Liquefaction Reactors Based on the NEDOL Process

Abstract

A direct coal liquefaction plant was constructed in Kashima, Japan, based on the concept of “NEDOL Process”, and successfully processed 150 tons of Tanitorarum coal per day during 1997−1998. The plant was equipped with three reactors: 1 m in diameter and 11.8 m in length, connected in series. During the operation, solid particles were accumulated mainly in the first reactor. Slurry samples were directly removed from the reactors, and size distributions of solid particles were determined. Two types of particles were found: particles with cores and particles without cores. The size of the former particles was in the range of 10−200 μm, while that of the latter particles was 1−80 μm. The growth rate of the particles was estimated to be 0.10 nm s-1 under the reaction conditions. The solid accumulation in the first reactor was classified into a dense region in the lower part of the reactor and a lean region extending above the dense region. The former region was expressed as a three-phase fluidized bed model, and the latter was expressed by a one-dimensional sedimentation−dispersion model. These reactor models were validated on the basis of pressure differences and particle size distributions. It was confirmed by the simulation that removing a small amount of solids from the bottom of the first reactor was effective to achieve a long-term continuous operation without accumulation of coarse solid particles.

Analysis of Inorganic Constituents Deposited in a 150 T/day Coal Liquefaction Pilot Plant

“…Quantitative Analysis of Deposits. There have been several studies related to behavior of inorganic matter in the liquefaction process. − ,− In these studies, inorganic matter in deposits, − liquefaction residue, and extract solution after solid−liquid separation 10,11 were characterized. However, no systematic and quantitative analysis of the deposits in the liquefaction plant has been made so far, and therefore details of the mechanism of deposit formation have not been understood yet.…”

“…The operation was almost successful; however, it was reported that some problems occurred related to the solid deposition in several units in the facility. − The deposit reduced the effective volume of the reactor and connecting pipe, resulting in a significant pressure drop and decrease of residence time of the slurry in the reactor. There have been several reports about the deposits in coal liquefaction plants. − In these studies, the deposits in coal liquefaction plant were analyzed qualitatively. For example, Aramaki et al analyzed the carbonaceous and inorganic solids in deposits of a 150 t/day pilot plant.…”

Catalytic Hydrogenation of HyperCoal (Ashless Coal) and Reusability of Catalyst

“…Although demonstrating the principles of coal liquefaction, the disadvantages of the NEDOL process rendered it impractical for wide-scale implementation. The catalyst can be deactivated through the deposition of coke and ash onto the catalyst surface, and the presence of minerals in the reaction mixture can cause accumulation of solid particles and eventual deterioration of equipment such as liquefaction reactors, separators, and pipelines. , Furthermore, relatively high temperatures and hydrogen pressures were required, leading to a high cost for coal liquefaction.…”

A Simple Sampling Method for the Reaction History in Fluidized or Transport Reactors

“…This technique could find application in waste treatment, metal oxide reduction, energy production, − petrochemical, and other fluid−solid processes. It could contribute substantially to surface treatment of medical tablets, production of carbon nanotubes, , sulfur capture in energy production, − solids and catalyst attrition and modification, − and degradation of metal oxide used as oxygen carrier chemical vapor deposition, , foodstuff and grain conditioning, and particle distributions in reactors .…”