Lock hopper

FIOR Process. In the FIOR process, shown in Figure 5, sized iron ore fines (0.04—12 mm) are dried in a gas-fired rotary dryer. A skip hoist dehvers the dry fines to lock hoppers for pressurizing. The fines pass through four fluidized-bed reactors in series. Reactor 1 preheats the ore to 760°C in a nonreducing atmosphere. Reactors 2, 3, and 4 reduce the ore at 690—780°C. At higher (ca 810°C) temperatures there is a tendency for the beds to defluidize as a result of sticking or hogging of the reduced material. 

The PEBC at the Tidd Station operates at 1200 kPa (170 psi) and a bed temperature of 860°C (51). A pressure vessel, 13.4 m in diameter by 20.7 m high, houses the combustor and its ancikafies. Coals, which contain ash contents less than about 25%, are blended with dolomite and pumped to the combustor as a paste having a total water content of 20—25%. Coals, which contain ash contents higher than 25%, and dolomite are individually fed pneumatically via separate lock hoppers. Both coal and dolomite are cmshed to 3-mm top size before being fed to the unit. 

Continuous Pressure Filters These filters consist of conventional drum or disk filters totally enclosed in pressure vessels. Filtration takes place with the vessel pressurized up to 6 bar and the filtrate discharging either at atmospheric pressure or into a receiver maintained at a suitable backpressure. Cake discharge is facilitated through a dual valve and lock-hopper arrangement in order to maintain vessel pressure. Alternatively, the discharged filter cake can be reslurried within the filter or in an adjoining pressure vessel and removed through a control valve. 

Solids may be processed continuously or semicontinuously by pumping slurries or by using lock hoppers. An example is the separation of insoluble polymers by floatation with a variable-density SCF. For liquid feeds, multistage separation may be achieved by continuous counter-current extraction, much like conventional liquid-hquid extraction. The final produces may be recovered from the extract phase by a depressurization, a temperature change, or by conventional distillation. 

Coal is fed as a paste containing 25 wt % water, and sorbent is fed diy by a lock-hopper system with pneumatic conveying. The top size of each feedstock is 3 mm in). The latent heat lost evaporating the water fed with the paste is compensated by increased gas turbine power output resulting from the increased flue-gas mass flow rate. For the 80-MWe unit, there are six coal feed points (one per 4.5 m" [48 ft"]) and four sorbent feed points (one per 6.7 m" [72 ft"]), all entering beneath the tube bank along one wall. The bed depth is... 

KRW Figure 2.5 illustrates key features of this gasifier. Coal and limestone, crushed to below 1/4," are transferred from feed storage to the KRW fluidized-bed gasifier via a lock hopper system. Gasification takes place by mixing steam and... 

CHAIRMAN SEGLIN I think their conceptual design was based on lock hoppers. He alluded to slurry pumping, but that s a horror. 

A. CONN If anybody has had any experience with lock hoppers, I think they would rather have almost anything else. 

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