TABLE OF CONTENTS Much effort was expended in the earlier chapters of this book providing methods for determining the conditions of pressure and temperature at which hydrates would form for natural gas mixtures. Another means of combating hydrate formation is to avoid the regions of pressure and temperature where hydrates would form. This issue is the topic of this chapter.
We have already discussed the range of temperature and pressure where hydrates may form. In order to prevent the formation of hydrates, one merely has to keep the fluid warmer than the hydrate-forming conditions (with the inclusion of a suitable margin for safety). Alternately, it may be possible to operate at a pressure less than the hydrate formation pressure.
With a buried pipeline, which loses heat to the surroundings as the fluid flows, the temperature must be such that no point in the pipeline is in the region where a hydrate will form. This heating is usually accomplished by two means, either by using line heaters or heat tracing.
A heater can be used to warm the fluid. Because this is a single-point injection of energy, the amount of energy must be such that the fluid remains above the hydrate point until the next point where heat is added is reached. This means that the fluid entering the pipeline must be well above the hydrate temperature.
Another method to add heat to a system is to use heat tracing. In this method, heat is injected continuously along a line. Thus...
