Plant and method for generation of synthesis gas

Abstract

Method and plant for generation of synthesis gas, comprising the steps of air fractionation to give oxygen, nitrogen and tail gas, gasification of a hydrocarbonaceous fuel to give crude synthesis gas and cleaning of the crude synthesis gas by removal of acid gas by means of cryogenic absorption, wherein the absorbent is cooled by means of a compression coolant circuit and the cooling water used is cooled by evaporative cooling by means of the tail gas obtained in the air fractionation.

Claims

1. A method of generating a synthesis gas which consists essentially of carbon monoxide and hydrogen and has been purified of acid gases, proceeding from a hydrocarbonaceous fuel, and also air and steam, the method comprising the steps of: a) fractionating air by low-temperature rectification to give an oxygen stream, a tail gas stream and a nitrogen stream, wherein the tail gas stream and the nitrogen stream are at ambient temperature and the nitrogen stream is at a pressure above ambient pressure; b) converting a hydrocarbonaceous fuel at a pressure above ambient pressure and a temperature above ambient temperature with the oxygen stream generated in step a) and the steam to a synthesis gas; c) removing the acid gases from the synthesis gas generated in step b) by low-temperature absorption in an absorption column with a liquid absorbent; d) cooling the absorbent used in step c) to the low temperature needed for the low-temperature absorption by means of a compression refrigeration plant, wherein the compression refrigeration plant comprises a coolant circuit in which a coolant is compressed and hence heated and is cooled and condensed by subsequent heat exchange with cooling water; and e) cooling the cooling water before it exchanges heat with the coolant in step d) by evaporative cooling, wherein the evaporative cooling in step e) is conducted with the tail gas stream generated in step a) and/or, after the tail gas stream has been expanded, with the nitrogen stream generated in step a).

2. Method according to claim 1, wherein the nitrogen stream generated in step a) is first expanded and contemporaneously cooled by means of a turbine, then used for cooling by heat exchange of the coolant in the coolant circuit of the compression refrigeration plant and then for evaporative cooling of the cooling water.

3. A plant for generation of synthesis gas, comprising: a) a first plant for fractionation of air using an air fractionation plant that works by the principle of cryogenic rectification under a pressure above ambient pressure, suitable for generating a stream of gaseous oxygen and a stream of gaseous nitrogen at a pressure above ambient pressure and ambient temperature, and a tail gas stream; b) a second plant for conversion of a carbonaceous fuel with a gasifying agent to give a synthesis gas comprising mainly hydrogen and carbon monoxide, wherein the first and second plant are connected such that the oxygen generated in the first plant can be added to the gasifying agent used in the second plant; c) a third plant for removal of the acid gases carbon dioxide and hydrogen sulfide from the crude synthesis gas generated in the second plant by absorption at low temperature with a liquid absorbent comprising methanol; d) a compression refrigeration plant, comprising a coolant selected from the group consisting of ammonia, propylene, and combinations thereof; and e) an evaporative cooler configured to cool cooling water.

4. The plant for generation of synthesis gas, as claimed in claim 3, further comprising an expansion turbine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Developments, advantages and possible uses of the invention are also apparent from the description of non-limiting working and numerical examples and of the drawings which follows. All the features described and/or shown in images, alone or in any combination, form the invention, irrespective of the way in which they are combined in the claims or the dependency references therein.

(2) The figures show:

(3) FIG. 1: block diagram of the plant according to the invention,

(4) FIG. 2: method diagram of a compression coolant circuit with the inventive use of nitrogen and tail gas for cooling of the cooling water.

DETAILED DESCRIPTION OF THE INVENTION

(5) In FIG. 1, the plant 1 according to the invention comprises the component plants of cryogenic air fractionation 2, gasification 3, Rectisol plant 4, compression refrigeration plant 5 and the evaporative cooling plant 6. Air 7 is sucked in from the environment and fractionated in the air fractionation 2 into an oxygen stream 8, a nitrogen stream 9a and a tail gas stream 10. The gasification plant 3 is supplied with carbonaceous fuel 11, and it is converted therein with the oxygen stream 8 and steam 12 supplied to the plant to crude synthesis gas 13 and ash 14. The crude synthesis gas 13 generated is fed to the Rectisol plant 4, where the acid gases hydrogen sulfide 34 and carbon dioxide 19 are removed by cryogenic absorption with methanol as absorbent. The hydrogen sulfide removed is discharged from the plant 1 as stream 34 and the cleaned synthesis gas as stream 15 for further treatment. The carbon dioxide 19a removed is used for cooling in the coolant circuit of the compression refrigeration plant 5 and then discharged from the plant as stream 19b for further use or disposal. The methanol absorbent used in the Rectisol plant 4 is heated in the course of its use and therefore has to be cooled continuously. A stream of heated methanol 16a is guided into the compression refrigeration plant 5, cooled therein, and conducted back into the Rectisol plant 4 as stream 16b. The cooling output of the component plant 5 is assisted by employing the nitrogen stream 9b that has been generated in the air fractionation 2 and expanded and simultaneously cooled in the turbine 20 for cooling of the coolant in the coolant circuit of the compression refrigeration plant 5. The nitrogen stream 9b that has been expanded and cooled in the turbine 20 is guided into the compression refrigeration plant 5, heated therein and guided as stream 9c to the cooling tower 6, in order to flow through the cooling tower together with the tail gas stream 10 from the air fractionation 2 and to cool the cooling water by evaporation. The nitrogen-tail gas mixture 17 laden with moisture in the cooling tower is discharged for further treatment outside the plant 1. From a plant outside the plant 1, which is not shown, cooling water 18a is supplied to the cooling tower 6, cooled therein and fed to the compression refrigeration plant 5 as stream 18b and thence discharged from the plant 1 as stream 18c.

(6) FIG. 2 shows the compression refrigeration plant 5 and evaporative cooling plant 6 components of the plant according to the invention. The coolant circulates in the compression coolant circuit 21. Frequently, the coolant used is ammonia or else propylene.

(7) The coolant stream 22 is compressed in two stages in the series-connected compressors 23 and 24 and cooled by means of cooling water and partly condensed in heat exchanger 25. The coolant stream is then divided into streams 26 and 27. Stream 27 is expanded in valve 28, simultaneously cooled, and used for cooling of stream 26 in heat exchanger 29 and then recycled back into the main stream upstream of compressor 24. The coolant stream 26, after being cooled in heat exchanger 29, is cooled in heat exchanger 30 by the carbon dioxide stream 19a removed in the Rectisol plant 4, FIG. 1. The nitrogen stream 9a generated in the air fractionation 2, FIG. 1, is introduced, expanded in the turbine 20 and cooled. The nitrogen stream is then used as stream 9b in heat exchanger 31 for cooling of the coolant stream. Subsequently, the coolant stream is expanded in valve 32, simultaneously cooled further, and then used in heat exchanger 22 for cooling of the methanol absorbent 16a, b. From a supply unit which is not shown and is not part of the plant, cooling water 18a is introduced into the evaporative cooler 33 of the component plant 6. Likewise introduced into the evaporative cooler 33 is residual gas 10 from the air fractionation 2, FIG. 1, and the nitrogen stream 9c. These gases are laden with moisture, discharged from the plant as stream 17 and disposed of. The cooling water 18b that has been cooled in the evaporative cooler 33 is guided into the compression refrigeration plant 5, where it is used for cooling and condensation of the coolant in heat exchanger 25 and then discharged from the plant as stream 18c.

(8) 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.

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

(10) “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.

(11) “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.

(12) 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.

(13) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

(14) 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.

INDUSTRIAL APPLICABILITY

(15) The invention provides a way of lowering the expenditure of electrical energy in the production of synthesis gas that has been freed of acid gas. The invention is therefore industrially applicable.

LIST OF REFERENCE NUMERALS

(16) 1 method/plant according to the invention

(17) 2 low-temperature air fractionation

(18) 3 gasification

(19) 4 low-temperature absorption (Rectisol plant)

(20) 5 compression refrigeration plant

(21) 6 evaporative cooling plant

(22) 7 air

(23) 8 oxygen

(24) 9 nitrogen

(25) 10 tail gas

(26) 11 hydrocarbonaceous fuel

(27) 12 steam

(28) 13 crude synthesis gas, comprising acid gases

(29) 14 residue/ash

(30) 15 synthesis gas, free of acid gases

(31) 16 a, b methanol

(32) 17 nitrogen-tail gas mixture, laden with moisture

(33) 18 a, b, c cooling water

(34) 19 a, b carbon dioxide

(35) 20 turbine

(36) 21 compression coolant circuit

(37) 22 coolant stream

(38) 23 compressor

(39) 24 compressor

(40) 25 heat exchanger

(41) 26 coolant stream

(42) 27 coolant stream

(43) 28 valve

(44) 29 heat exchanger

(45) 30 heat exchanger

(46) 31 heat exchanger

(47) 32 valve

(48) 33 evaporative cooler