Liquefaction continued reactor

A question of considerable interest in coal hydroliquefaction chemistry is the amount and nature of "organically bound metals in the coal. One reason for this interest is the observation that when supported metal direct conversion catalysts are used in liquefaction reactors, a primary mode of deactivation is metals deposition Q, 2). In particular, recent work at the Pittsburgh Energy Technology Center (PETC) (4,5) and elsewhere (3) has indicated very high levels of titanium deposition on supported Co Mo catalysts used in the fixed bed continuous reactor system. It has been suggested that the culprits in such deposition are soluble metal species (6 9) The analyses of a Western Kentucky (Homestead) hvBb feed coal and of material deposited between the catalyst pellets in the fixed bed reactor at PETC (4) are shown in Table I. 

Continuous Reactors. Consider the experimental data available for the pyrrhotites formed during coal liquefaction in continuous reactors (Table m), about a dozen observations for the ten pound per day bench scale continuous liquefaction unit at four temperatures (375, 400, 425 and 450°cXl5) and about the same number of observations for the 400 pound per day reactor at 450°C (450°-460°cX4),... 

The 1973 petroleum crisis intensified research on coal liquefaction and conversion processes. The technology developed in this field was later harnessed in chemical recycling of plastics. Mastral et al. [32], for example, employed two different batch reaction systems (tubing bomb reactors and magnetically stirred autoclave) and a continuous reactor (swept fixed bed reactor). Chemical recycling techniques such as pyrolysis [28, 33-38] or coliquefaction with coal [39, 40] convert plastic wastes into hydrocarbons that are valuable industrial raw materials. 

M0rup, A., et al., 2015. Construction and commissioning of a continuous reactor for hydrothermal liquefaction. Industrial Engineering Chemistry Research 54 (22), 5935—5947. 

CCDC built a continuous short residence time coal liquefaction unit with throughput of about 4.5 kg/hr of coal. The SRC unit consisted of a short residence time reactor constructed from 53.3 m of high pressure tubing having an ID of 0.516 or... 

In addition to continuous bench-scale work, CCDC carried out a rather extensive laboratory program involving the use of the microautoclave reactor. The program developed tests to compare the activities of different solvents. These tests quickly evaluated a solvent so that the performance under coal liquefaction conditions could be predicted. The tests are now used at the Wilsonville SRC Pilot Plant as a means of determining when stable operation has been achieved. 

Autoclaves provide reactors which can be used readily to acquire data from coal liquefaction studies but are less representative of likely commercial plant tyi reactors than small scale continuous bed-type reactors. Ideally comparisons between reactors are best made by carrying out experiments in various designs of reactors under similar reaction conditions, but, in order to cover the full range of designs adequately, a larger expenditure on equipment (beyond the budgets of most laboratories) would be necessary. However, steps can be taken to cover the... 

Starch Liquefaction. Starch in its natural state is only degraded slowly by CC-amylases. To make the starch susceptible to enzymatic breakdown, it is necessary to gelatinize and liquefy a slurry with a 30—40% dry matter content. Gelatinization temperature depends on the type of starch (67) com is the most common source of industrial starches followed by wheat, tapioca, and potatoes. Liquefaction is achieved by adding a heat-stable a-amylase to the starch slurry. The equipment used for liquefaction may be stirred tank reactors, continuous stirred tank reactors (CSTR), or a jet cooker. Most starch processing plants liquefy the starch with a single enzyme dose in a process using a jet cooker (Fig. 9). 

Cooking extruders have been studied for the liquefaction of starch, but the high temperature inactivation of the enzymes in the extruder demands doses 5—10 times higher than under conditions in a jet cooker (69). For example, continuous nonpressure cooking of wheat for the production of ethanol is carried out at 85°C in two continuous stirred tank reactors (CSTR) connected in series plug-flow tube reactors may be included if only one CSTR is used (70). 

Analyses of coals which have been processed in the continuously operated pilot plants are listed in Table 1. Process liquid yields from the liquefaction step for these coals are shown in Figure 4 for different residence times in the liquefaction reactor. Longer residence time increases conversion of coal to liquids, but also increases hydrocracking of liquids to gas. 

The high calcium content of the younger coals has led to the formation and deposition of calcium carbonate in the liquefaction reactor in the form of wall scale and oolites which were first observed in German operations (10). These deposits form as calcium salts of humic acids in the coal decompose under liquefaction conditions. The deposits continue to grow with time and could lead to unwanted solids accumulation in the reactor itself as well as fouling of downstream equipment (11). Data shown in Figure 7 indicate the accumulation rate of the calcium carbonate in the liquefaction reactor for different coals under typical EDS conditions as well as two methods for controlling the solids build-up. 

For some reactions listed in Table 1-4A, the fixed-bed reactor is operated under cocurrent-upflow conditions. Unlike the trickle-flow condition, this type of operation is normally characterized by bubble-flow (at low liquid and gas rates) and pulsating-flow (at high gas flow rates) conditions. Normally, the bubble-flow conditions are used. In the SYNTHOIL coal-liquefaction process, both pulsating-and spray-flow conditions are used, so that the solid reactant (coal) does not plug the reactor. In bubble flow, the gas is the dispersed phase and the liquid Ls a continuous phase. In pulsating flow, pulses of gas and liquid pass through the reactor. In the spray-flow regime, the gas is a continuous phase and the liquid is a dispersed phase. 

Liquefaction units (not to be confused with the hydrogenation processes) using continuous stirred tank reactors, at Niigata and Sapporo. 

Dispersed catalysts are defined as heterogeneous catalysts flowing alrnig with the reactants in a reactor system. The residence time of catalyst and reactants are thus equivalent and consequently, a continuous renewal of the catalyst-reactant interface is afforded. They demonstrate their usefulness in case of competitive fast deactivation or when accessibility of reactants to catalyst surface is hampered by feed characteristics. This kind of situation typically correi nds to heavy feeds processing, and effectively, the use of dispersed catalysts is practically limited to coal liquefaction and petroleum residues conversion. 

Since the liquefaction of coal in a regular packed bed catalytic reactor would cause plugging problems, the data illustrate the feasibility of using a novel type of reactor to continuously operate a three-phase gas-liquid-solid (reactant) reaction in the presence of a catalyst. 

Elliott, D.C., et al., 2013b. Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor. Algal Research 2 (4), 445—454. 

Elliott, D.C., Hart, T.R., Schmidt, A.J., Neuenschwander, G.G., Rotness, L.J., Olarte, M.V., Zacher, A.H., Albrecht, K.O., Hallen, R.T., Holladay, J.E., 2013b. Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor. Algal Research 2, 445-454 web published September 29, 2013. 

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