Injection of a Liquid Spray into a Fluidized Bed:  Particle−Liquid Mixing and Impact on Fluid Coker Yields

Abstract

In industrial fluid cokers, the feedstock, consisting of heavy bituminous hydrocarbons, is atomized with steam and injected into the hot fluidized bed of coke. Good and uniform contact of the liquid droplets with the solid particles is required to provide heat for the cracking reactions while mass transfer effects are minimized. Experiments in a pilot plant coker have suggested that the initial particle/liquid mixing, in the spray jet, is rather poor. Experiments in a X-ray scanner showed that liquid droplets and entrained particles accumulate just below the tip of the jet plume. To illustrate the importance of the initial liquid-solid mixing, a simple model has been proposed to predict its effect on coker yields. An experimental technique was developed to quantitatively determine the quality of mixing with current nozzle technology and a new enhanced solids entrainment (ESE) device. The model has been used in combination with the experimental results to show the effect of ESE on product yields. The ESE nozzle has been shown to greatly improve liquid/solid mixing by increasing the amount of wetted solids and achieving a more uniform initial liquid/solid mix. The model suggests that ESE will improve liquid yield by up to 0.6 wt % and reduce the coke yield by up to 2 wt %.

Electric conductance method to study the contact of injected liquid with fluidized particles

“…Both the hydrocarbon conversion efficiency and the operability of the reactor are strongly affected by the initial contact between the injected liquid and the fluidized solids. 1,2 It has been shown that improving the contact of injected liquid with fluidized particles increases the yield of valuable liquid products in both the fluid catalytic cracking process, where most of the liquid is vaporizable, and in the fluid coking process, where most of the liquid is not directly vaporizable, but must first be cracked to generate vaporizable fractions. 1,3 In the case of vaporizable liquids, liquid-solid agglomerates may or may not be formed, depending on the operating conditions, 4,5 while they always form with nonvaporizable liquids.…”

“…1,2 It has been shown that improving the contact of injected liquid with fluidized particles increases the yield of valuable liquid products in both the fluid catalytic cracking process, where most of the liquid is vaporizable, and in the fluid coking process, where most of the liquid is not directly vaporizable, but must first be cracked to generate vaporizable fractions. 1,3 In the case of vaporizable liquids, liquid-solid agglomerates may or may not be formed, depending on the operating conditions, 4,5 while they always form with nonvaporizable liquids. 6 Bruhns et al 7 investigated the interaction between vaporizable liquid jets and fluidized solids in a pilot-scale re-actor operated at 120-180 8C.…”

“…The formation of agglomerates upon the contact between liquid jets and a small-scale fluidized bed was quantified by House et al 1,8 They injected a binder solution via gas-atomization nozzles into a fluidized bed of coke particles at room-temperature, and froze the formed agglomerates right after completing the liquid injection by interrupting the fluidization air. They found that both the nozzle internal geometry and internals, such as a draft tube or an impact cone interacting with the liquid jet, have a strong impact on the quality of the liquid-solid contact.…”

Comparison of the impact of flow pulsations on the performance of various liquid–gas injectors in a gas–solid fluidised bed

“…Heat from the hot coke particles thermally cracks the bitumen and converts it into lighter and more valuable hydrocarbon products. The thermal cracking reaction depends on the contact between bitumen and hot coke, which should occur rapidly to increase the yield of valuable condensable products and to avoid poor bed fluidity (House et al, 2004).…”

Enhanced Productivity of Chemical Processes Using Dense Fluidized Beds

“…However, the agglomeration techniques were only applicable in the lab, not in a commercial reactor. House et al (2004) discuss the coker application and state that the actual temperature difference of interest in a coker is 300°C (coke particles up to 650°C, bitumen feed 350°C). They developed a technique to measure how much liquid initially contacts coke particles when sprayed into a fluidized bed.…”