Single-train

As of the end of 1996, about 70 SNAM plants, 125 STAC, and 7 Toyo stripping plants have been built. Currently STAC will design plants for over 3000 MTD, SNAM about 2800 MTD, and Toyo about 2300 MTD as single train units. 

Steam-Reforming Natural Gas. Natural gas is the single most common raw material for the manufacture of ammonia. A typical flow sheet for a high capacity single-train ammonia plant is iadicated ia Figure 12. The important process steps are feedstock purification, primary and secondary reforming, shift conversion, carbon dioxide removal, synthesis gas purification, ammonia synthesis, and recovery. 

W. Turner, "Ten Years of Single Train Ammonia Plants," NMPO 74, ICI Operating Symposium, BiUingham, UK, 1974. 

Couplings are discussed with reliability partly because in the past, as the single-train compressor installations were going through early growing pains, couplings were certainly a part of the pain. Not too many words need be used here, but possibly a bit of a reminder of the past will avoid problems in the future. 

These i high-pressure core spray (HPCS) system that replaced the HPCI system. The const e motor-driven pump train powered by its own electrical division complete with J diesel fhese plants also have a single train low-pressure core spray system, as well as a RHR system similar to the system design in the BWR. 3/4 group. 

The primary lesson from this example is that no process is infinitely scalable. Sooner or later, additional scaleup becomes impossible, and further increases in production cannot be single-train but must add units in parallel. Fortunately for the economics of the chemical industry, the limit is seldom reached. 

Small versions of production facilities are sometimes used for product development, particularly in the polymer industries. Single-train plants producing... 

Scale in Parallel. This common scaling technique was discussed in Section 3.2.1. Subject to possible tube-to-tube distribution problems, it is an inexpensive way of gaining capacity in what is otherwise a single-train plant. 

World-scale, single-train units, coupled with advances in automation, led to the use of servomechanisms for valve plug positioning. 

Fifth, if the system is merely enlarged it does not require any more operating personnel than a smaller unit. For this reason, a larger so-called single-train plant would be preferable to two duplicate plants side by side, even if there were no other savings. 

Before the hold tanks can be specified it must be determined whether one, two, or three products are to be made simultaneously. If only one product is made at a time, a large single-train centrifuging and drying system can be constructed. However, when two or three products are produced in separate trains at different rates, it would appear that the desire to have both similar equipment and optimally sized equipment for each train cannot be met. Therefore, for this plant only one product will be made at a time. Further, two full trains will be constructed. This is to prevent the plant from fully shutting down because of the failure of a piece of equipment. When the proposed expansion occurs another full train will be added. 

This cost is very low, compared to other estimates. This may be due to the fact that Zevnik and Buchanan assume a single-train plant, whereas the plant just designed has two trains. If this assumption is made, the direct investment cost of a functional unit for a 75,000,000 lb/yr plant would be 280,000. Making the same calculations as before, the cost of a 75,000,000 lb/yr plant would be 4,400,000. The cost of two such plants would be 8,800,000. This is still low. 

Single train availabilities must be at least 90% for utility applications and greater than 97% for refineries and petrochemical complexes. 

A single train oil-gas separation system for the subject crude would have vessels about 12 ft in diameter by 45 ft long. Although not unreasonable compared with the space and cost associated with two or three trains, a single-train concept may not perform at the 95% uptime which Is... 

---