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Table 2 The OTSG can be operated in one of three modes: constant dry gas, constant firing rate, or constant feed water flow rate. Table 2.4 shows the attributes of the technology when operated at constant dry gas conditions. The technology vendor has also reported that feed water quality does not have to be better than what is currently being fed to the traditional OTSGs for the SQ90™ design to achieve 90 percent steam quality. The technology improves boiler efficiency through the reduction in feed water volumes required for a given steam load, thereby resulting in reduced water treatment cost.?° This is a commercially available technology for deployment in the oil sands industry. With most OTSGs in the industry producing 78 percent steam quality, SQ90™ promises to take that to 90 percent while preventing dry outs. The technology is based on the use of rifled pipes within the radiant section of the OTSG. The use of rifled tubes is common in nuclear reactor designs where very high heat fluxes can be easily attained. The pipes are designed with a swirl pattern that induces a rotational flow to the fluid stream, thus, providing an even, wet layer on the pipe wall which promotes heat transfer to the liquid and reduced risk of dry out.?° The stream travels through the tubing in a spinning motion, creating a centrifugal force that separates water from steam using less energy. This is unlike the traditional smooth pipes where liquid droplets tend to remain in the lower section of the pipe due to the affects of gravity. Figure 2.4 compares the cross-sectional views of a smooth pipe and a rifled pipe in operation. does not have to be better than what is currently being fed to the traditional OTSGs for the
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