Optimal Design and Operating Conditions of the CO₂ Liquefaction Process, Considering Variations in Cooling Water Temperature

Abstract

Ship transportation of liquid CO 2 is now considered as an alternative transport option to pipelines, in the absence of any suitable onshore storage locations. The compressors for a liquefaction process in the transport chain account for a significant portion of the total energy consumption. The temperature of seawater as an intercooling medium has a very significant effect on the energy consumption of the multistage compressors. Although several studies for the optimal design and operation of liquefaction process have been proposed, they do not consider the seasonal and locational variations in the cooling water temperature; therefore, further improvement in the energy efficiency in the CO 2 liquefaction process is necessary. In this study, the variations in the operational energy and other operational issues of the CO 2 liquefaction process, according to the actual seawater temperature in the range of 5−30 °C was investigated. Moreover, the optimal discharge pressure of the final stage compressor before the Joule−Thomson (J-T) expansion and the pressure ratio of multistage compressors are provided, given the seawater temperature, to minimize the total compressor power consumption. Furthermore, the optimal number and position of multistream heat exchangers are investigated. The total compressor power consumption is ∼90−140 kW h /ton CO 2 in the seawater temperature range of 5−30 °C.

Factors Influencing CO2 and Energy Penalties of CO2 Mineralization Processes

“…Most are in the range of 2 to 4, whereas some suggest a ratio that is less than 2. Briefly, some studies have used pressure ratios that are above 2. In contrast, researchers have presented the development of a Ramgen compressor by the U.S DoE because there are difficulties associated with CO 2 compression ratios that are above 2.…”

Optimization of the CO2 Liquefaction Process-Performance Study with Varying Ambient Temperature

“…In addition to Hegerland et al [6], Lee et al [21] also investigated the relationship between cooling temperature and liquefaction process performance. However, both of these studies only consider liquefaction at low pressure and Lee et al limit their study to the performance of open cycle CO 2 processes.…”

Stochastic Optimization of a Natural Gas Liquefaction Process Considering Seawater Temperature Variation Based on Particle Swarm Optimization

“…For example, even if there are seawater temperature variations that may have a significant impact on operational costs, previous studies do not consider them. Lee et al handled a stochastic optimization problem including seawater temperature variations, which are very sensitive to the compressor power consumption in case seawater is used as the coolant for the CO 2 liquefaction process . The seawater temperature becomes a critical factor in decreasing the operational energy of the CO 2 liquefaction process, and the seawater temperature varies seasonally and even daily and also differs according to the seashore .…”

“…Lee et al handled a stochastic optimization problem including seawater temperature variations, which are very sensitive to the compressor power consumption in case seawater is used as the coolant for the CO 2 liquefaction process. 14 The seawater temperature becomes a critical factor in decreasing the operational energy of the CO 2 liquefaction process, and the seawater temperature varies seasonally and even daily and also differs according to the seashore. 14 Thus, this point also should be considered as generating a stochastic optimization problem for a DMR cycle, in which seawater is used as the coolant.…”

“…14 The seawater temperature becomes a critical factor in decreasing the operational energy of the CO 2 liquefaction process, and the seawater temperature varies seasonally and even daily and also differs according to the seashore. 14 Thus, this point also should be considered as generating a stochastic optimization problem for a DMR cycle, in which seawater is used as the coolant.…”