Continuous-flow configurations open-closed

Figure 2.15 — Variants of coupled continuous configurations and sensors accommodating an immobilized catalyst (Cat). (A) Conventional system. (B) Stopped-flow system. (C) Configuration with iterative reversal of the flow direction. (D) Open-closed circuit configuration. Symbol meanings are given in Fig. 2.14. For details, see text.

Automatic continuous-flow methods Involving the continuous introduction of sample into the system are implemented by means of two different configurations (a) open, in which the flow is wasted after passing through the measuring cell, and (b) closed, in which the flowing solution is returned to the vessel to be recirculated once it has passed through the detector. 

Fig. 7.1 Basic types of configuration used in completely continuous flow analysis, (a) Open the sample is discarded after measurement, (b) Closed the sample is recycled.

Two versions of the ACP have been developed (1) an open-loop configuration in which the dry spent absorbent is simply removed from the system for disposal and fresh alkali is continuously fed to the spray dryer, and (2) a closed-loop process in which the spent absorbent is regenerated and reused. The open-loop system was installed on the 410 MW, Coyote Station at Beulah, North Dakota (Botts et al., 1978). The plant used a spray dryer followed by a fabric filter for simultaneous SO2 and dust removal. As indicated by the flow diagram of Figure 7-32, the process is extremely simple. Because the particulate collected on the fabric filter bags remains on the fobric for a period of time, the gas-solids contact time is extended beyond the particulate residence time in the spray diyo so additional absorption of SO2 by the alkaline material occurs. After this system went conunercial in 1981. no other large soda ash spray dryers were built. About 1990, this scrubber was converted finm soda ash to lime to eliminate solids build-up in the dryer vessel and to use lower cost lime. The... 

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