DE102013219254A1 - Energetically optimized process for material coal / biomass utilization - Google Patents

Abstract

The invention relates to a process for the energy-optimized production of synthesis gas, in which a synthesis gas is produced in a gasification apparatus under steam use, which gas is cooled in a contactless heat exchanger and used materially after it leaves the heat exchanger. In the heat exchanger, the working medium of a gas turbine is heated. After the discharge of the working fluid from the gas turbine, it is fed to a waste heat boiler, where it emits residual heat to generate steam. The generated steam can be used as a gasifying agent or elsewhere in the process.

Description

The present invention is a method in which the energy balance in the material utilization of gas obtained from coal or biomass can be significantly improved.

For the material use of coal and / or biomass in the form of basic materials for the chemical industry, the primary energy source (coal or biomass) is first converted into a gas (gasified) according to the state of the art. At a Winkler gasification under pressure (~ 30 bar) and at high temperature (outlet temperature ~ 890-950 ° C), high conversion rates are achieved from the feed to the product gas. Since this gasification is allothermic, an external energy input is needed in the process. This can be done by the gasification saturated steam. Since the gasification energy has to be provided externally, the process becomes very energy consuming.

Gasification produces a combustible gas at around 920 ° C, which must be cooled before gas purification and subsequent synthesis (e.g., Fischer-Tropsch, SNG, DME synthesis). This entire process chain of gasification and subsequent synthesis is not yet economically feasible. Therefore, an energetic improvement of the overall process is necessary to make it more efficient.

Due to the lack of economic efficiency of biomass gasification processes and the subsequent material use, various processes are being tested on a pilot plant scale. In the previously known methods is either a pure material or a pure energetic use:
There are a number of solutions that have set themselves the goal of improving the overall efficiency of the processes. Typically, heat recovery and utilization methods are proposed for this purpose.

In the US 4,099,383 A is described inter alia that a gas stream (synthesis gas, pyrolysis gas) from a gas generator through a non-contact heat exchanger (recuperator) is performed. In this heat exchanger, a heat transfer medium is heated. As a heat transfer medium, among others explicitly water, helium, nitrogen and argon are named. The heat transfer medium is then fed to a turbine as a working medium, where it is used to generate energy. It is explicitly described that the waste heat of the heat transfer medium is used for preheating the oxygen carrier for the gasification. In the US 4099383 A an in-process generation of the steam required for gasification is provided, this is done from the raw gas of the carburetor. This approach has a number of disadvantages: higher corrosion of the steam generator, since it is flowed through with unpurified raw gas (high alkali and dust content); lower efficiency, since possibly an additional cooling in the gas turbine process is needed so that it can be operated closed, so that the waste heat can not be ideally exploited.

The DE 28 21 413 C2 describes a process in which H ₂ and CO-containing gases are produced by partial oxidation of the fuels in a reactor. These synthesis gases are cooled in a high-temperature heat exchanger (recuperator) by means of water, whereby a vapor stream is formed. This is optionally used partly in a turbine for energy production. Another part of the superheated steam is added to the synthesis gas stream. As material for the high-temperature heat exchanger metallic or ceramic materials are named. The whereabouts of the steam leaving the turbine and its residual heat are not discussed further.

The known methods for using biomass for the production of synthetic substances, so far have a too low efficiency. So far, no combined material and energetic use of biomass based on gasification has been realized with high efficiency. As a result, energy flows are not used efficiently.

Studies have shown that the prior art methods often use existing waste heat sources only conditionally. Thus, necessary temperature adjustments in the process are still carried out by quenching or cooling when the waste heat is released to the environment.

It is therefore the task to propose an improved process management for the material coal / biomass use, by which the overall energy efficiency of the process can be improved.

The object is achieved by the method mentioned in claim 1. Advantageous embodiments of the method are objects of the dependent claims.

According to the invention the problem is solved by the material is coupled with the energetic use. By transmitting an energy flow from the raw gas to an indirectly heated gas turbine at a high temperature level, in addition to the synthetic substances and electricity and steam generated, the steam is preferably used within the overall process to meet the gasification requirements or partially cover. The crude gas is preferably supplied after cooling and gas treatment of the material use (eg Fischer-Tropsch synthesis). However, the raw gas can also be used for other methods according to the prior art.

The core of the invention is the process control of coupled material and power generation as well as internal heat utilization for steam supply for the gasification process. The material use is made possible by a prior art gasifier with subsequent syntheses.

In the gasification process, coal or biomass is gasified in a high-temperature gasifier (for example high-temperature Winkler gasifier) at elevated pressure (preferably about 30 bar). The resulting combustible crude gas preferably has a temperature in the range of 750 ° C to 1100 ° C, more preferably from 820 ° C to 1000 ° C and most preferably from about 890 ° C to 950 ° C and a pressure preferably in the range of 25 bar to 50 bar, more preferably from 28 bar to 45 bar and most preferably in the range of 30 bar to 40 bar. It is cooled and fed to the desired synthesis after a gas treatment (cleaning / dedusting). Products of the synthesis may e.g. Gasoline and diesel fractions, methanol, dimethyl ether or hydrogen.

The raw gas is, optionally after a preliminary dedusting (eg. In a cyclone or ceramic filter cartridges), led to the cooling in the primary circuit of a heat exchanger, wherein a guided in the secondary circuit, preferably gaseous working fluid is heated for a gas turbine process.

The waste heat streams from the raw gas are thus advantageously used to drive an indirectly heated gas turbine process for power generation. This is preferred by an innovative ceramic high-temperature heat exchanger, as in [1], [2], or in the DE 10 2012 209052.5 described, which transfers the heat from the raw gas to the compressed gas turbine working medium.

The working medium occurs, depending on the process control (open / closed), depending on the compressor ratio and medium preferably at a temperature in the range of 150 ° C to 350 ° C, more preferably from 200 ° C to 300 ° C and most preferably from 240 ° C to 290 ° C and a pressure of preferably 2 bar to 30 bar, more preferably 2 bar to 20 bar and most preferably 2.5 bar to 10 bar, in the recuperator and at a temperature in the range of preferably 600 ° C. to 910 ° C, more preferably from 700 ° C to 900 ° C and most preferably from 800 ° C to 900 ° C from the heat exchanger. It preferably reaches a temperature of up to 900 ° C. (The higher the discharge temperature of the working fluid, the higher the efficiency of the gas turbine process, but it can not reach the raw gas temperature at the entrance to the heat exchanger (preferably 920 ° C).)

As a working medium known from the prior art media are used. Air, helium, argon, etc. are preferred here. An open gas turbine process (preferably with the working media air if necessary with water or steam injection) or a closed gas turbine process (preferably air, helium, nitrogen or argon as the working medium) is possible. Since the raw gas has a very high temperature, a high-temperature heat exchanger (recuperator) is preferred for removing the heat from the crude gas stream. Preferably, this consists of ceramic, more preferably, it has ceramic heat pipes. Particularly advantageously, the use of the high-temperature heat exchanger based on heat pipes allows a large temperature spread between incoming and exiting raw gas. But there are also other types of heat transfer from the prior art under the condition of long expected life can be used.

Further preferably, the design of the heat exchanger is also possible in several stages, the seen in Rohgasströmungssicht, first stage is particularly resistant to temperature (preferably high-temperature heat exchanger with ceramic heat pipes), while the other stages either also with a heat exchanger with heat pipes, possibly not ceramic and with Other working media for the corresponding temperature range, or with a conventional construction (eg shell and tube heat exchanger made of metallic materials) can be realized. Thus, the particularly expensive high-temperature heat exchanger is advantageously limited to the necessary application. The working medium of the gas turbine process is advantageously conducted in countercurrent, so that it first flows through the heat exchanger of the last and possibly middle stages before it is fed into the heat exchanger of the first stage.

Both open and closed gas turbine processes are preferred. In the open gas turbine process ambient air is preferred and in the closed gas turbine process preferably also air, but also preferably also helium, argon, nitrogen, water vapor or other fluids from the prior art used.

A closed gas turbine process is particularly preferred since it has the advantage that on the one hand, no heat losses with the exhaust air from the gas turbine process are dissipated to the environment and on the other hand, other working media can be used in closed processes, such. B. Helium, which has about five times the heat capacity as air (Cp (He) = 5.2kJ / kg / K, Cp (air) = 1.0kJ / kg / K (at 20 ° C) and 1, 1 at 900 ° C).

The relaxed working medium still has a high temperature after the gas turbine. Preferably, the turbine exit temperature is in the range of 500 ° C to 700 ° C, more preferably 520 ° C to 650 ° C, and most preferably 540 ° C to 610 ° C. The working medium is therefore passed to the gas turbine in a conventional waste heat boiler (AHK), in which the required amount of steam for the gasification (preferably saturated steam) is completely or at least partially generated. The waste heat boiler may also have a multi-stage heat exchanger. By virtue of this process management, it is advantageously not necessary to have a year-round heat consumer since the heat is used internally for the gasification process. In the energetic use of biomass as currently operated and researched, however, a heat sink is always necessary to make electricity generation ecologically sensible and economical. By the present invention, the district heating extraction is no longer necessary because the waste heat streams are preferably used for the support of the material use. With open gas turbine process only air at a temperature in the range of 60 ° C to 90 ° C, preferably from about 77 ° C from.

By the method according to the invention advantageously takes the best possible utilization of the feedstock (domestic) brown coal and hard coal or biomass through a material and energy use and the reduction of greenhouse gas emissions. In particular, the use of biomass from sustainable (forest) economy, less CO ₂ emissions. The process represents a step towards independence from oil and coal imports, towards a coupled generation of electricity and materials.

characters

1 schematically shows the overall process according to the invention, which couples the material and energy use by optimally utilizing energy flows. Coal or biomass ( 01 ) is used in a high-temperature gasifier ( 1 ) gassed. The combustible raw gas ( 12 ) is cooled and after a gas treatment ( 2 ) of the desired synthesis ( 3 ). By the cooling of the raw gas ( 12 ) is in a gas-gas heat exchanger, the working medium ( 124 ) of the gas turbine ( 4 ) heated. In open gas turbine process ambient air and in the closed gas turbine process also air but also helium or other fluids are used. To the gas turbine ( 4 ) is a generator connected (not shown), the current ( 40 ) generated. The working medium ( 45 ) has after relaxation in the gas turbine ( 4 ) still a high temperature. The working medium ( 45 ) is therefore after the gas turbine ( 4 ) in a conventional waste heat boiler (AHK) ( 5 ), in which the gasification ( 1 ) required amount of saturated steam ( 501 ) is produced. The saturated steam ( 501 ) is then the carburetor ( 1 ).

2 shows schematically the process according to the invention for the recovery of heat and its conversion into electrical energy and superheated steam using an open gas turbine process.

3 shows schematically the use of a closed gas turbine process to recover the heat and its conversion into electrical energy and superheated steam.

embodiments

The following exemplary embodiments are intended to explain the method according to the invention in more detail, but without limiting the invention to these. The examples were calculated without pressure losses.

All four embodiments are based on a carburettor with the following performance data: carburetor Thermal input: 500MW Mass flow of raw gas: 39,4kg / s Temperature: 920 ° C Print: 30bar gasification agent Steam (37bar, saturated) 11,9kg / s Oxygen (33bar, 240 ° C) 9.4kg / s

example 1

It is based on the presentation in 2 Referenced. The hot raw gas stream ( 12 ) from the carburetor is on the primary side in the heat exchanger ( 6 ). The crude gas stream ( 12 ) has a temperature of 920 ° C and a pressure of 30 bar. He gives his heat to the working medium ( 125 ), in this case air, compressed at a temperature of 15 ° C (air ( 120 )) enters the secondary circuit and the heat exchanger ( 6 ) as cooled Crude gas stream ( 62 ) leaves at a temperature of 300 ° C and a pressure of about 30 bar. The compressed air ( 125 ) has on entry into the heat exchanger ( 6 ) a temperature of 268 ° C. The heated compressed air ( 124 ) leaves the heat exchanger ( 6 ) with a temperature of 900 ° C at a pressure of 6.73 bar. It is fed to the gas turbine, where the hot compressed air ( 124 ) relaxes and cools while giving off energy to the turbine. This drives next to the compressor ( 41 ) also a generator (not shown) for power generation. The compressed air ( 45 ) leaves the turbine ( 4 ) at a temperature of 545 ° C and a pressure of about 1 bar. The hot compressed air ( 45 ) now enters the steam generator ( 5 ), which together with the preheater ( 55 ) acts as a waste heat boiler. The still hot turbine exhaust ( 45 ) Cools in the steam generator to 251 ° C and, seen in the flow direction of the working fluid, subsequent preheater finally to 77 ° C at a pressure of 1 bar. The now cool relaxed air ( 452 ) (77 ° C) leaves the plant, typical of an open turbine process. In the waste heat boiler ( 5 ), consisting of steam generator and preheater, the incoming water (15 ° C, 1 bar) ( 502 ) to saturated steam ( 501 ) heated at a temperature of 246 ° C and a pressure of 37 bar. The relatively low pressure ratio of 6.73, in contrast to conventional gas turbines, results from optimization calculations with regard to the best efficiency as a function of the given temperatures.

Example 2

It is based on the presentation in 3 Referenced. The hot raw gas stream ( 12 ) from the carburetor is on the primary side in the heat exchanger ( 6 ). The crude gas stream ( 12 ) has a temperature of 920 ° C and a pressure of 30 bar. He gives his heat to the working medium ( 125 ), in this case air, which circulates in the secondary circuit and leaves the heat exchanger ( 6 ) as a cooled crude gas stream ( 62 ) at a temperature of 300 ° C and a pressure of about 30 bar (minus pressure losses). The heated compressed air ( 124 ) leaves the heat exchanger ( 6 ) with a temperature of 900 ° C at a pressure of 4.71 bar. It is fed to the gas turbine, where the hot compressed air ( 124 ) relaxes and cools while giving off energy to the turbine. This drives next to the compressor ( 41 ) also a generator (not shown) for power generation. The compressed air ( 45 ) leaves the turbine ( 4 ) at a temperature of 600 ° C and a pressure of 1 bar. The still hot turbine exhaust ( 45 ) now enters the steam generator ( 5 ), which together with the preheater ( 55 ) acts as a waste heat boiler. The hot turbine exhaust ( 45 ) Cools in the steam generator to 251 ° C and, seen in the flow direction of the working fluid, subsequent preheater finally to 43 ° C at a pressure of 1 bar. The now cool relaxed air ( 452 ), typical of a closed turbine process, the compressor ( 41 ), which, from the turbine ( 4 ), the air ( 452 ) again compressed to a pressure of 4.71 bar. The compressed air ( 125 ) has a temperature of 257 ° C when entering the heat exchanger. In the waste heat boiler ( 5 ), consisting of steam generator and preheater, the incoming water (15 ° C, 1 bar) ( 502 ) to saturated steam ( 501 ) heated at a temperature of 246 ° C and a pressure of 37 bar.

Example 3

It is also on the representation in 3 Referenced. The hot raw gas stream ( 12 ) from the carburetor is on the primary side in the heat exchanger ( 6 ). The crude gas stream ( 12 ) has a temperature of 920 ° C and a pressure of 30 bar. He gives his heat to the working medium ( 125 ), in this case helium, which circulates in the secondary circuit and leaves the heat exchanger ( 6 ) as a cooled crude gas stream ( 62 ) at a temperature of 300 ° C and a pressure of about 30 bar. The heated helium ( 124 ) leaves the heat exchanger ( 6 ) at a temperature of 900 ° C at a pressure of 2.68 bar. It is fed to the gas turbine, where the hot helium ( 124 ) relaxes and cools while giving off energy to the turbine. This drives next to the compressor ( 41 ) also a generator (not shown) for power generation. Helium ( 45 ) leaves the turbine ( 4 ) at a temperature of 594 ° C and a pressure of 1 bar. The hot helium now enters the steam generator ( 5 ), which together with the preheater ( 55 ) acts as a waste heat boiler. The hot helium ( 45 ) Cools in the steam generator to 251 ° C and, seen in the flow direction of the working fluid, subsequent preheater finally to 57 ° C at a pressure of 1 bar. The now cool relaxed helium ( 452 ), the compressor ( 41 ), which, from the turbine ( 4 ), the helium ( 452 ) again compressed to a pressure of 2.68 bar. The compressed helium ( 125 ) has on entry into the heat exchanger ( 6 ) a temperature of 256 ° C. In the waste heat boiler ( 5 ), consisting of steam generator and preheater, the incoming water (15 ° C, 1 bar) ( 502 ) to saturated steam ( 501 ) heated at a temperature of 246 ° C and a pressure of 37 bar.

LIST OF REFERENCE NUMBERS

01

 Coal / biomass and gasification agent

1

 gasification

12

raw gas stream

120

 cool air as a working medium of the open gas turbine process

124

 heated gas turbine working medium

125

 compressed, not yet heated gas turbine working medium

2

 gas processing

23

 Synthesis gas stream (cooled and purified raw gas)

3

 Synthesis (eg FT, SNG, DME, methanol synthesis)

30

 product flow

4

 Indirectly heated gas turbine (Air, He, Ar ...)

40

 electrical power generated by the generator coupled to the gas turbine

41

 Compressor for indirectly heated gas turbine process

45

 Working medium with residual heat after gas turbine outlet

451

 Working medium between evaporation and preheating

452

 cool working medium after the waste heat boiler

5

 waste heat boiler

55

 Preheater of the waste heat boiler

501

 Steam flow for use as a gasification agent or process steam for other applications

502

 feedwater

6

 Heat exchanger

62

 cooled crude gas stream

7

 Feedwater pump

Quoted non-patent literature

• [1] Pause, J .; Beckmann, M .: New applications for heat pipes. In: Hufenbach, WA (ed.): Proceedings of the International Colloquium of the Leading Technology Cluster ECEMP 2010. TU Dresden, 2010. p. 215-225. ISBN 978-3-00-032522-9
• [2] Unz, S .; Beckmann, M .: Calculation method for the design of ceramic heat pipe heat exchangers. In: Hufenbach, WA; Gude, M .: ECEMP-European Center for Emerging Materials and Processes Dresden-International Colloquium of the Leading Technology Cluster ECEMP 2011. Dresden 2011. ISBN 978-3-942267-43-4

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4099383 A [0005, 0005]
• DE 2821413 C2 [0006]
• DE 102012209052 [0015]

Claims (8)

Process for the energetically optimized production of synthesis gas, in which a synthesis gas is produced in a gasification apparatus under steam use, which is cooled in a contactless heat exchanger and used material after exiting the heat exchanger, wherein in the heat exchanger, a working fluid of a gas turbine is heated, characterized in that the working medium is fed after exiting the gas turbine to a waste heat boiler, where it emits residual heat, which is used to generate steam. A method according to claim 1, characterized in that the working medium is guided in a closed gas turbine process in a circle. A method according to claim 2, characterized in that is used as the working medium air, water vapor, argon, nitrogen or another gas inert to the materials of the gas turbine. A method according to claim 1, characterized in that the working medium is used in an open gas turbine process. A method according to claim 4, characterized in that air or water vapor is used as the working medium. Method according to one of the preceding claims, characterized in that the generated steam is supplied to the gasification device for generating the synthesis gas. Method according to one of the preceding claims, characterized in that a high-temperature heat exchanger with ceramic heat pipes is used as the heat exchanger. Method according to one of the preceding claims, characterized in that the heat exchanger is designed in multiple stages.

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