No abstract

A statistical-entropy analysis is performed for three existing low-output (up to 1500 kg/h) plants. A plant in Petergof, Leningradskaya Oblast, operates on a simple throttling cycle. A plant in Razvilka, Moscow Oblast, operates on a somewhat complicated throttling-ejector cycle. A plant run by the Kriogenmash Company is equipped with two ejectors and three additional separators, permitting removal of low-boiling components from the natural gas. All these plants are analyzed with consideration of the natural-gas composition.In analyzing plants employed for the liquefaction of natural gas (LNG), it is important to consider that the composition of the natural gas (NG) delivered to the plant may differ appreciably with respect to different gas fields.In this connection, it is necessary to focus attention on the effectiveness of the operating processes in the plant, taking the composition of the product obtained into account. Additional components, which make it possible to improve the quality and lower the fraction of impurities in the LNG produced are occasionally introduced to a system under design.This paper analyzes the statistical entropy of three existing low-output plants (up to 1500 kg/h). A plant (fabricated by the Lentransgas Co. in Petergof, St. Petersburg Oblast) operates on a simple throttling cycle. A plant (fabricated by the EKIP, in the village of Razvilka, Moscow Oblast) operates on a somewhat complicated throttling-ejector cycle. A plant built by the Kroigenmash (city of Balashikha, Moscow Oblast) for China, is equipped with two ejectors and three additional separators, permitting removal of low-boiling components from NG.Preliminary cooling to the 238 K level is employed at all of the plants.They were all analyzed with consideration of the NG composition (in contrast to [1], in which it was proposed that they operate on pure methane). The composition of the gas, as determined from data provided by the Kriogenmash Co. is presented in Table 1; these data permit more reliable evaluation and comparison of plant effectiveness and comparison with computed results from [1].1. Initial data for determination of methane-cycle characteristics (a schematic diagram of the plant operating on the throttling-ejector cycle is shown in Fig. 1).T am = 300 K -average temperature of ambient medium; T pr.cool = 238 K -preliminary cooling temperature of methane;

This paper is devoted primarily to thermodynamic analysis of cycles implemented in three low-capacity pilot plants for liquefaction of natural gas (in Moscow, St. Petersburg, and Yekaterinburg). In our opinion, results of the research conducted will undoubtedly be defined more precisely in possible replication of small-capacity plants, or the creation of new ones.The problem of producing liquefied natural gas (LNG) in Russia has existed for some time: as early as the outset of the 1980s, the design and construction of a large-scale liquefaction complex was begun by the collective Scientific-Production Association Kriogemash on the initiative of the general contractor for cryogenic engineering, member-correspondent of the Academy of Sciences of the USSR V. P. Belyakov. These operations had ceased with the breakup of the USSR. Today, foreign companies are constructing on Sakhalin Island the heavy-duty liquefaction complex Sakhalin-2 with a capacity of the order of several hundred tons of LNG per hour, which will basically provide for export demands. As for internal demands for LNG, it must be remembered that a branching pipeline system for the distribution of natural gas containing a significant portion of methane (CH 4 ), which attains 95-98%, is being built and is functioning within the Russian landmass. Since LNG is used as a fuel for all types of transport, including aviation, and is extremely promising, LNG production is actually limited in a number of cases by small truck gas-filling compression stations (TGFCS) and gas-distribution stations (GDS), which have a heavy-duty, and at the present time, incompletely loaded compressor base. Today, there are three low-capacity (up to 1000 kg/h) "pilot" liquefaction plants in St. Petersburg, Moscow, and Ekaterinburg. They are built in accordance with two designs: with a simple throttle cycle, and with a rather complex throttle-ejector cycle; and, preliminary chilling at a level of 238 K is utilized in both designs. The degree of thermodynamic improvement in the liquefaction of methane (the ratio of the minimum required energy for liquefaction to that actually expended) for these plants does not exceed 0.3 (i.e., 30%). To improve the efficiency of the plants (or demonstrate the need to search for new solutions), it is necessary to determine the feasibility of reducing energy losses, which is of particular import, since it should be considered that replication of small liquefaction systems not only in our country, but also in many others is inevitable with expanding use of LNG in all types of transport. The probability of this situation is rather high: it is substantiated by a large amount of experience acquired in the fields of transportation, storage, and utilization of other cryogenic liquids such as oxygen, nitrogen, and hydrogen on the one hand, and by expanding pipeline export of natural gas to Europe on the other.( ) 400 * Actually, the existing plant is equipped with four compressors, each with an output of 900 nm 3 /h and a 125-kW electric motor. Overall output...

No abstract

No abstract