Method and device for condensing a carbon dioxide-rich gas stream

Abstract

The invention relates to a method for condensing a carbon dioxide-rich gas stream, wherein a stream of water heated by an exchange of heat with the carbon dioxide-rich stream, which is at least partially condensed, is sent to at least one compressor (3,21) for compressing the carbon dioxide-rich stream or a fluid, the carbon dioxide-rich stream of which is derived, in order to at least partially cool at least one stage of said compressor.

Claims

1. A method for condensing a gas stream rich in carbon dioxide, in which method a stream of water is heated up by exchange of heat in a heat exchanger with the gas stream rich in carbon dioxide which at least partially condenses to produce a heated water stream and an at least partially condensed carbon dioxide rich stream, wherein the heated water stream is further heated by sending the heated water stream to: i) a first compressor of the gas stream rich in carbon dioxide in order to cool the first compressor of the gas stream rich in carbon dioxide; and ii) a second compressor of a fluid from which the stream rich in carbon dioxide is derived in order to at least partially cool at least one stage of the second compressor, thereby producing an extra heated water stream, wherein the heated water stream is sent to the first compressor and the second compressor in a parallel configuration.

2. The method as claimed in claim 1, further comprising the step of cooling the extra heated water stream to produce a cooled water stream, and recycling at least a portion of the cooled water stream to be used as the stream of water order to cool the stream rich in carbon dioxide that is to be at least partially condensed.

3. The method as claimed in claim 1, in which the fluid compressed in the second compressor is derived from a process to form the stream rich in carbon dioxide, wherein the process is selected from the group consisting of distillation, amine scrubbing, permeation, adsorption, and combinations thereof.

4. The method as claimed in claim 1, in which the heated water stream is at a first temperature and is sent to the first compressor and the second compressor at a temperature equal to the first temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

(2) FIG. 1 shows an embodiment of the prior art.

(3) FIG. 2 shows an embodiment of the prior art.

(4) FIG. 3 shows an embodiment of the invention.

(5) FIG. 4 shows an embodiment of the invention.

(6) FIG. 5 shows an embodiment of the invention.

DETAILED DESCRIPTION

(7) The invention will be described in greater detail with reference to FIGS. 3 to 5.

(8) FIG. 3 differs from FIG. 1 in that the water used to cool the compressors 3 and 21 comes from the same cooling circuit as the water of the condenser 27 and has been used to condense the gas rich in carbon dioxide before being used to cool the compressors.

(9) Thus, the water 31 is divided into two parts 31A, 31B. The part 31A is sent to the compressor 21 to cool it and the water thus heated is sent to a cooling means 53. The part 31B is sent to the compressor 3 of fluid intended for distillation and the water thus heated is also sent to the cooling means 53 which may be a cooling tower. The cooled water 51 from the cooling means 53 is once again sent to the condenser 31.

(10) The separation means 11 may be a separation means working by cooling and condensation or by amine scrubbing or by permeation or by adsorption.

(11) The fluid 1 is preferably a gas containing at least 50% carbon dioxide.

(12) Thus, the water is sent to the two compressors in parallel. It would also be conceivable to send the water to just one of these two compressors. It would also be conceivable to send the water to other consumers on the site (compressors of air separation devices, coolers on the boiler or any other consumer).

(13) A numerical example illustrates the advantages of the invention:

(14) TABLE-US-00001 Cooling water networks in parallel Cooling water Thermal temperatures Water power Inlet Outlet flow rate kcal/h ° C. ° C. m.sup.3/h Water for condensation 7.13E+06 25 28.84 1860 Water for the rest of the 3.33E+07 25 35 3340 plant Specific energy (kWh/t 132.2 excluding energy from CO2 condensed) the water circuit Specific energy (kWh/t 136.4 with water circuit (pumps and fans) CO2 condensed) (86% for pumps) Total flow rate of water 5200 stream to be circulated

(15) TABLE-US-00002 Cooling water networks in series Cooling water Thermal temperatures Water power Inlet Outlet flow rate kcal/h ° C. ° C. m.sup.3/h Water for condensation 25 28.84 1860 Water for the rest of the 28.15 38.15 3095 plant (of which 100% of the flow rate used for condensation) Specific energy (kWh/t 133.3 excluding energy from CO2 condensed) the water circuit Specific energy (kWh/t 136 with water circuit (pumps and fans) CO2 condensed) (78% for pumps) Common cooling tower 4.06E+07 38.15 25 3095 Total flow rate of water 3095 stream to be circulated

(16) For the same condensed quantity of stream rich in carbon dioxide, the cooling water flow rate therefore drops from 5200 m.sup.3/h according to the prior art to 3095 m.sup.3/h for the invention. The specific energy of the compressors increases because the cooling water is hotter (from 132.2 to 133.3 kWh/t of CO.sub.2 condensed), but if the energy needed to circulate the cooling water is taken into consideration, the total amount of energy needed on site will be reduced.

(17) Another advantage of the invention is that it becomes economical to increase the flow rate of water through the condenser of the stream rich in carbon dioxide. Although doing so would not be economical with networks in parallel—because the drop in condensation temperature (and therefore in compression energy) had to fully compensate for the increase in flow rate and therefore in the cost of the associated equipment—it does become conceivable in networks in series where increasing the flow rate through the condenser has a number of positive outcomes: reducing the condensation temperature; reducing the temperature of the cooling water in the other equipment and therefore the compression energy for the rest of the plant.

(18) By contrast, the condenser of the stream rich in carbon dioxide needs to be sized for a larger flow rate of water, but that is undoubtedly of secondary concern compared with the benefit of condensing at a lower temperature.

(19) According to another aspect of the invention, it is the rest of the plant that adapts to suit the water flow rate chosen for the condenser. The heat rise therefore increases in the other coolers and the water network is smaller, with larger coolers because the thermal approaches (LMTDs) reduce as the water is heated up more against the gas which becomes cooled. In the example given hereinabove, the flow rate of water consumed on site would drop to 1860 m.sup.3/h rather than 3100 m.sup.3/h and the compression energy would increase a little more because of the water being hotter (28.84° C. in place of 28.15° C.).

(20) FIG. 4 shows a diagram for exchange of heat in the condenser of the stream rich in carbon dioxide when the gas condenses at around its critical pressure; thus the condensation level-off may be seen. The heat exchanged is shown on the ordinate axis and the temperature on the abscissa axis. ΔT indicates the rise in temperature of the water, ΔTa the approach temperature in the condensation exchanger at an intermediate point and ΔTb the approach temperature at the cold end.

(21) In contrast with FIG. 4, FIG. 5 shows the same diagram for supercritical condensation, which is why there is no level-off Pseudocondensation corresponds to a pronounced change in density.

(22) It would also be possible to implement the invention with the diagram of FIG. 2. In that case, the water would be heated up in the condenser 27. This heated water would then be used to cool at least one of the compressors 3, 21, 121, 221 or any other cooling water consumer on the site.

(23) While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

(24) The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

(25) “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.

(26) “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary a range is expressed, it is to be understood that another embodiment is from the one.

(27) Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

(28) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such particular value and/or to the other particular value, along with all combinations within said range.

(29) All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.