NO325049B1 - Procedures for increasing energy and cost efficiency in a gas or power plant; a thermal power plant for the same and a combustion chamber for use in connection with such plants. - Google Patents

Abstract

The invention relates to a method for increasing energy and cost efficiency in a gas power station or cogeneration plant and for energy and cost-effective C0 capture from flue gas with concentrated CO 2 content. The plant preferably comprises two gas turbines comprising at least one compressor (13) and a turbine (14) and further comprising a combustion chamber (10), as flue gas from the combustion chamber (10) is expanded, cooled and passed through a cleaning unit (11) where at least substantial parts of the CO 2 content of the flue gas is removed. Recycled flue gas is further used for cooling the flame pipe (40) in the combustion chamber (10) and concentration of the CO 2 content in the flue gas, with supply of fresh air to the combustion chamber (10) for close stoichiometric combustion. The invention encompasses an improved combustion chamber system which increases the energy efficiency of the gas turbine process and performance can be maintained at the highest possible level. The invention also relates to a power plant for carrying out the method.

Description

The present invention relates to a method for increasing energy and cost efficiency in a gas power plant or cogeneration plant and for energy and cost effective C02 capture. The gas power plant or cogeneration plant comprises a gas turbine plant or a combined plant with a steam and gas turbine cycle, preferably equipped with at least two gas turbine plants with a compressor part and a turbine part and comprising further combustion chambers with flame tubes, where said combustion chamber works with essentially two separate gas flows where one gas flow is made up of air which supplied together with fuel centrally inside the flame tube, and where the second gas stream is made up of a cooling gas that runs on the outside of said flame tube, as flue gas from said combustion chamber is expanded and cooled and passes through a cleaning unit where at least significant parts of CC> The 2 content from the flue gas is removed before the purified flue gas is released into the atmosphere.

The present invention correspondingly relates to a gas power plant or a cogeneration plant, as well as a combustion chamber adapted to such plants.

Emissions of carbon dioxide (C02) have increased significantly in recent decades and represent a global problem. Based on the Kyoto agreement and the "precautionary" principle, it is therefore desirable to limit the emission of greenhouse gases such as CO2 in order to counteract changes in the climate. One measure is to ensure the capture of C02 in connection with the conversion of energy from fossil fuels in gas power plants and/or cogeneration plants. The various elements in the C02 value chain include technology for capture, transport and further final storage or use of C02 for, for example, increased oil recovery in reservoirs (IOR).

Exhaust gas purification from gas power plants (so-called post-combustion type) is currently in operation on a medium scale. Such exhaust gas purification also has the potential for cost reductions. The existing technology for exhaust gas purification is based on the absorption of carbon after combustion has taken place. A gas power plant of this type is described in open literature, textbooks and publications.

The exhaust gas from a standard combined cycle gas turbine power plant contains approx. 3.5 volume % CO2 and the exhaust must be cooled from approximately 450-600 °C to the normal operating temperature for amine washing which is around 40-55 °C. In the atmospheric absorption tower, CO2 in the gas is transferred to the liquid phase by chemical absorption in the amine solution. It is important to have a large contact surface between gas and liquid, and the tower will be tall and can reach over 30 metres, and for a 400 MW power plant the required cross-section in the absorption column is 260-320 m<2>. A standard gas power plant with this type of exhaust gas cleaning therefore has the disadvantage that both the investment costs and the operating costs are very high, in addition to the fact that the plant is also very space-consuming.

There are known technologies that can provide more cost-effective capture facilities by increasing the CO2 content in the exhaust gas from a gas turbine power plant to approx. 10 volume % CO2. It can be achieved by recycling large amounts of exhaust gas. But recycling large amounts of exhaust gas results in another problem, namely that the oxygen content in the combustion chamber becomes too low to maintain stable combustion. It is not possible to recycle larger amounts of exhaust gas than the equivalent of approx. 6-7 volume % C02 without having problems with insufficient oxygen content to maintain stable combustion. The present invention aims to achieve approx. 10 volume % CO2 in the exhaust gas without having problems with insufficient oxygen content by using an improved combustion chamber arrangement and power plant concept.

From NO 318638, a method is known for increasing the energy and cost efficiency in a gas power plant or cogeneration plant and for energy and cost effective CO2 capture from pressurized flue gas with a concentrated CO2 content. The plant comprises a gas turbine which comprises a compressor and a turbine and further comprises a combustion chamber, as flue gas from the combustion chamber is cooled and passes through a pressurized cleaning unit where at least significant parts of the C02 content from the flue gas are removed. The cleaned flue gas is reheated and, together with the supply of pressurized steam, fed to the turbine and an exhaust gas boiler, before the cleaned flue gas is released into the atmosphere. A partial flow is used for heat exchange in the combustion chamber. Thereby optimal heating of this partial flow is achieved in the combustion chamber where the heat energy is transferred at the highest possible temperature and the partial flow is then carried on to the turbine inlet, so that the energy efficiency and performance of the gas turbine process can be maintained at the highest possible level.

A similar method is known from NO 3197 98. The plant according to this solution preferably comprises two gas turbines which comprise at least a compressor and a turbine and which further comprise a combustion chamber. Flue gas from the combustion chamber is expanded, compressed and cooled and passes through a pressurized cleaning unit where at least significant parts of the C02 content from the flue gas are removed. The purified flue gas is heated again and used for heat exchange in the combustion chamber, and together with the supply of pressurized steam, it is supplied to the turbine and the exhaust boiler before the purified flue gas is released into the atmosphere.

It is also known that more cost-effective concepts for CO2 capture exist, for example in WO 2004/072443, which describes capture systems of a similar type for exhaust gas with concentrated CO2 and higher pressure, but with a different type of combustion chamber arrangement.

Furthermore, it is well known that in order to achieve lower NOx emissions from gas turbine plants and combustion plants, it is beneficial to recycle cooled flue gas back to the combustion chamber.

One purpose of the invention is to lay the foundation for power plants where emissions of greenhouse gases are reduced to a minimum or eliminated by using a standard gas turbine power plant with a standard combustion chamber with some modifications.

Another purpose is to find more energy- and cost-effective solutions and to reduce, preferably halve, both investment costs and operating costs in relation to existing technology. It is of particular interest to achieve an energy-efficient solution in that the temperature at the inlet to the turbine part is kept as high as possible and preferably without deviation from a standard gas turbine power plant.

It is also an aim to find cost-effective solutions for gas power plants, where new compact capture systems for exhaust gas with concentrated C02 can be used.

According to the invention, the objectives are achieved by the method and a power plant as specified in the accompanying claims.

According to the invention, a more efficient power plant is achieved where emissions of CO2 can be reduced by preferably 85-90%, but can also be a lower reduction, i.e. from 0-90%.

Furthermore, a facility is achieved that is simpler to build and does not require such large areas compared to traditional facilities for amine washing, this in particular because a CO2 absorption part can be made simpler. An effective utilization of such a C02 solution for cleaning flue gas requires that the flue gas has concentrated CO2.

A further advantage of the solution according to the invention is a significantly reduced need for modifications of a standard combustor and it can be used for all types of gas turbine combustors, both external combustors or integrated combustors, including annular type or canned combustor type.

The objectives are achieved by a method, a gas power plant or cogeneration plant, as well as a combustion chamber as described in the independent patent claim. Alternative embodiments are defined in the independent patent claims.

The consequences are achieved/become a consequence of the invention:

The present invention uses an improved combustion chamber system adapted to the recycling of flue gas to achieve an optimal concentration of CO2, approx. 10 volume % C02, in the flue gas, without the problems of insufficient oxygen content to maintain a

stable combustion process.

Can perform cost-effective C02 separation due to

high CO2 concentration in the flue gas.

Can be used for all standard combustion chamber types in standard

gas turbine power plant with minor modifications. The combustion can take place at optimum

combustion temperature and excess air in order to meet the requirement for a necessary low NOx emission.

Preferred embodiments of the invention shall be described in more detail below with reference to the accompanying figures, where: figure 1 shows an improved combustion chamber system according to the invention;

figure 2 shows schematically in diagram form a preferred embodiment of a gas power plant according to the invention; and

figure 3 shows a further embodiment of a combustion chamber.

It should be stated that the indicated temperatures and pressures indicated below are only intended to be indicative of the described embodiment and these values can be varied without thereby deviating from the core of the invention.

The characteristic feature of the proposed plant according to Figure 2 is that the combustion chambers 10, 10' work with essentially two separate gas streams, one of which is supplied inside the flame tube 40, 40' and the other is supplied on the outside of the flame tube. The flame tube 40, 40' has perforations so that optimal cooling of the flame tube is achieved, and the flow on the outside of the flame tube 40, 40' is gradually led through the perforation in the flame tube so that the partial flow can participate in cooling the combustion process and the combustion products. The flow is then passed on to the turbine part 14, 14' of the gas turbines 12, 12' at the highest possible temperature, so that the energy efficiency and performance of the gas turbine process can be maintained as high as possible.

It is a significant advantage of the proposed plant according to the design example shown in Figure 2 that the flue gas, which leaves the flame tube 40, 40' at a temperature as high as, for example, 1200 °C, can go directly to expansion in a turbine part that is built to withstand such high temperatures. The flue gas is then carried on via the standard exhaust boiler 29, 29' to the water cooler 47, 47'. After the water cooler 47, concentrated flue gas is fed to the CC>2 capture facility 11. The flue gas that goes to C02 capture is not pressurized.

After the water cooler 47', the flue gas is recycled from the second combustion chamber 10' to the compressor part 13' of the second turbine 12', where the flue gas is given a pressure of, for example, 15 bar and a temperature of 400 °C, before the flue gas is passed on to the combustion chambers 10, 10' for cooling on the outside of the flame tube 40, 40'. The recycled flue gas continues through the holes in the flame tube 40,40' and into the combustion zone where it serves to cool the combustion process and mix with the combustion products so that these are further cooled. This also means that the concentration of CO2 in the flue gas is increased, so that the CO2 capture plant 11 can work under conditions that bring benefits both with regard to energy and cost efficiency. The plant can be realized relatively easily.

Reference is made to Figure 1. In the process shown in Figure 2, a standard combustion chamber 10 is basically used, which can be modified somewhat with regard to controlling the air flows. Standard, more or less conventional combustion chambers are suitable for use in connection with the invention, as these are often equipped with perforations in the flame tube, which allow cooling air to enter the combustion chamber to mix with combustion products and further cool them. The constructive execution of a typical standard combustion chamber can be found described in open literature, textbooks and publications. However, a standard combustion chamber is usually used in a different way, as the air is usually first led to the outside of the flame tube 40 (between the mantle 27 and the flame tube 40), and then further into the flame tube 40 to the primary zone and secondary zone of the combustion process.

But in the present plant the procedure (air management) is different, as the combustion chamber 10 works with essentially two separate gas streams, one of which is fed directly together with fuel to the center of the primary zone inside the flame tube 40 and the other goes to the outside of the flame tube 40 for cooling on the outside of the flame tube before it passes through the holes 55 in the flame tube 40. The channels at the primary zone are constructive details that must be determined by experiments in test rigs for combustion chambers at suppliers of gas turbines and combustion chambers. At the entrance to the combustion zone, there is also an extensive valve and distributor system which is not shown in the figure and which is also not part of the invention, but represents entirely professional adaptations.

Although the figure for the present plant shows two combustion chambers, it will be possible to use several combustion chambers. Furthermore, it should be stated that the combustion chamber is shown entirely schematically, where parts that are obvious to a person skilled in the art are not shown. An example of such an omission is, among other things, the pressure jacket which necessarily surrounds the combustion chamber.

According to the embodiments shown and described, CO2 capture systems are used, for example of the amine type. This type of solution is in use in existing facilities. However, it may also be relevant to use new types of C02 capture without thereby deviating from the idea of the invention.

In the process shown in Figure 2, a combined cycle gas power plant and an atmospheric CO2 capture plant 11 are used which will separate CO2 from flue gas with a concentrated C02 content. Two integrated gas turbine systems 12, 12' are used which are cross-connected with partial flows to combustion chambers 10, 10' and which work with essentially two separate gas flows, one of which is supplied directly together with fuel centrally inside the flame tube 40, 40' and the other is supplied on the outside of the flame tube 40, 40' through the mantle 27, before it enters through the holes in the flame tube and gradually mixes with the first partial flow. This gas, which is supplied on the outside of the flame tube 40, 40' is recycled exhaust gas, is used to cool the components of the combustion chamber and is then mixed with the combustion products that go to the turbine parts 14, 14' in the second gas turbine 12, 12', so that practical advantages in terms of reduced use of expensive high-temperature materials. In this context, reference is made to Figure 2. The flue gas then passes on to an exhaust boiler 29, 29' where the flue gas is cooled and the flue gas is carried on via a water cooler 47, 47'. The recycled flue gas for the gas turbine plant 12' goes to a water separator 56 after which the flue gas is led to the inlet of the compressor part 13', where the flue gas is compressed. From here, the flue gas stream is split in two, with one stream going to the combustion chamber 10 and the other stream going to the combustion chamber 10'. The recycled flue gas is used for cooling the outside of the flame tube 40, 40' and for the components of the combustion chambers.

The recycled flue gas continues through the holes in the flame tube and into the combustion zone where it serves to cool the combustion process and mix with the combustion products so that these are further cooled. This also means that the concentration of C02 in the flue gas can be increased to a maximum, as fresh air is supplied directly together with fuel centrally inside the flame tube and ensures a close stoichiometric combustion process, as a small excess of oxygen can be kept controlled at a level to simultaneously achieve a stable combustion.

In the design example shown in Figure 2, two different gas turbines are initially used with regard to usable shaft power, for example in a ratio of 1:3. But other ratios can also be used or similar gas turbines can be used, i.e. ratios between 1:3 and 1:1 can be used with regard to usable shaft power. However, the gas turbine's other parameters, such as pressure ratio, should be approximately the same. As available gas turbines on the market are only found in standard models with a given design and shaft power, the process shown in Figure 2 can be adapted to given gas turbines.

The gas power plant's combined cycle gas turbines 12,12' can be of the standard type, and the invention will involve a modification of the control system for the gas flows to the combustion chambers and the inlet channels to the combustion chambers. The present invention can be used in a simple way on all gas turbine plants, and is not limited to external combustors, "silo" type combustors, but can easily be used for integrated combustors, for example annular (annular) combustors or jug-shaped ("canned") type combustion chambers.

In addition, there is integration of the C02 capture facility 11, which is arranged as best as possible for practical implementation and cost-effectiveness.

The gas turbines 12,12' that are used comprise a compressor part 13,13' and a gas turbine part 14,14', each of which drives a separate generator 16,16'. The compressor part 13 supplies air through an outlet pipeline 17 to the combustion chamber 10. Typical temperature and pressure of the air supplied by the compressor part 13 can be 400 °C and 15 bar. Flue gas from the combustion chamber 10 is carried on through a pipeline 48 to the inlet of the turbine part 14.

The temperature of the flue gas out of the combustion chamber 10 can typically be in the order of 1200-1400 °C, which is the usual inlet temperature for the turbine part of normal gas turbines. From the turbine 14, the exhaust gas passes through an exhaust gas boiler 29 which produces steam for a steam turbine 58 which drives a generator 59, and/or possible heat delivery to an industrial plant. The temperature of the flue gas after the cooler 47 can typically be in the order of 100-60 °C. In the embodiment shown in Figure 2, the pressure is atmospheric at the entrance to the CO2 capture plant 11, while the temperature is typically around 100-60 °C and the C02 proportion is around 10% by volume. From the C02 plant 11, the purified flue gas is released into the atmosphere.Separated CO2 from the C02 plant 11 is compressed, condensed and pumped back, for example, to an oil well or to a suitable landfill.

The exhaust gas from the second turbine part 14' maintains a temperature of around 500-600 °C, is led from the turbine's outlet to the exhaust gas boiler 29' and further out from the boiler at a temperature of approx. 100 °C to a cooler 47' which reduces the temperature to about 15 °C. Furthermore, this untreated flue gas is led to the water separator 56 where water is removed from the exhaust gas. The exhaust gas here has a pressure of about 1 bar and a temperature of about 15 °C, and is then led to the inlet of the second turbine's 12' compressor 13'. Here, the flue gas is compressed to typically approx. 15 bar and 400 °C, and the flue gas stream is then divided into two sub-streams, so that one sub-stream goes on to the combustion chamber 10 and the other sub-stream to the combustion chamber 10'.

Figure 3 basically shows an alternative embodiment of a combustion chamber 10 and an alternative way of recirculating flue gas through and around the flame tube 40. This combustion chamber 10 also essentially works with two separate gas flows, where a fresh air flow is supplied directly together with fuel to the center of the primary zone inside the the flame tube 40. But the other partial flow is supplied on the outside of the flame tube 40 and is led countercurrently in the annulus between the flame tube 40 and the mantle 27 in order to thereby achieve optimal cooling of the flame tube 40 and the other components of the combustion chamber, before it passes through the holes 55 in the flame tube 40. This the solution is based on the same principles as the combustion chamber shown and described in connection with figure 1. The combustion chamber according to figure 3 is particularly adapted to a practical design for standard gas turbine types that use counter-current heat winding, and which also provides advantages to ensure optimal temperature difference in the heat exchange .

The present invention is not limited to an atmospheric C02 capture system 11, as it would be possible to place a pressurized C02 ~ capture system after the combustion chamber 10 in the pipeline 48 or integrated in the turbine part 14, and still obtain the advantage that the C02 portion in the flue gas constitutes about 10% by volume. The temperature at the inlet to the C02 capture system must, however, be reduced to 100-50 °C by using expensive gas-gas heat exchangers, which e.g. is described in WO 2004/072443. Thereby, a more cost-effective and energy-efficient C02 capture plant 11 can be achieved, while the heat exchanger plant will be more costly.

According to the invention, the cooling of the flame tube 40,40' can be based either on counter-flow or co-flow cooling, without thereby deviating from the idea of the invention.

Claims (13)

1. Procedure for increasing energy and cost efficiency in a gas power plant or cogeneration plant and for energy and cost-effective CC>2 capture, which gas power plant or cogeneration plant includes a gas turbine plant or a combined plant with a steam and gas turbine cycle, preferably comprising at least two gas turbine plants with a compressor part (13, 13') and a turbine part (14, 14') and further comprising combustion chamber (10) with flame tube (40), where said combustion chamber (10) works with essentially two separate gas flows where one gas flow is made up of air which is supplied together with fuel centrally inside the flame tube, and where the second gas stream is made up of a cooling gas that runs on the outside of said flame tube, as flue gas from said combustion chamber (10) is expanded and cooled and passes through a cleaning unit (11) where at least significant parts of the CC>2 content from the flue gas are removed, before the purified flue gas is released into the atmosphere, characterized by the use of additional a combustion chamber (10'), in that the flue gas from said second combustion chamber (10'), in a purified, cooled and pressurized state, is supplied to at least one of the combustion chambers (10, 10') on the outside of said at least one of the flame tubes for cooling said flame tube ( 40,40'), after which said recycled, more or less uncleaned flue gas is led into said flame tube through holes in said flame tube to cool the combustion process and mix with the combustion products. 2. Method according to claim 1, where both flame tubes (40, 40') are cooled by flue gas delivered from the second combustion chamber (10'), this flue gas being cooled down, for example to about 15 °C beforehand and then compressed to about make 400 °C before introduction on the outside of said flame tube (40,40'). 3. Method according to claim 1 or 2, where recycled flue gas is led through holes (55) in said flame tube (40, 40') along the entire length of said flame tube. 4. Method according to claims 1-3, where the air flow from the compressor part (13) is led directly into the primary zone of the combustion chamber (10,10') together with fuel to ensure near stoichiometric combustion and where the combustion process is cooled using recycled flue gas. 5. Method according to claims 1-4, where the pressure of the flue gas is increased after expansion and cooling and where this pressurized flue gas is recycled back to the combustion chamber (10, 10'), with optimal concentration of C02 before a CC>2 membrane system (11), to the combustion chamber (10, 10') in the annular space between the flame tube (40, 40') and the mantle (27, 27'). 6. Method according to one of claims 1-5, where the exhaust gas from the gas turbine(s) is sent through a heat-recovering exhaust gas boiler (29, 29') for the production of steam, where the steam drives one or more steam turbines (58). 7. Method according to one of claims 1-6, where a first and a second cross-connected gas turbine plant (12, 12') is used which has combustion chamber(s) (10, 10') where the gas that cools the outside of the flame tube (40) is mixed with the combustion products and goes to the turbine part (14, 14') and that the flue gas formed in the flame pipe (40') goes to the turbine part (14') in the second gas turbine (12'), after which the flue gas goes on to an exhaust boiler (29') where the flue gas is cooled and passed on via a water cooler (47') to the inlet of the compressor part (13') in the second gas turbine (12'), where flue gas is compressed and divided into two flue gas sub-flows. 8. Thermal power plant comprising at least one gas turbine plant or a combined cycle gas turbine plant, comprising at least two gas turbine plants (12,12') comprising a compressor part (13,13'), a turbine part (14,14') and preferably also at least one steam turbine ( 58), which thermal power plant further comprises a combustion chamber (10) equipped with a flame tube (40) and a surrounding casing (27) for forming an annular space, a cooler (47), a plant (11) for separating C02 flue gas after the combustion chamber (10) and one or more exhaust gas boilers (29,29'), as well as associated pipelines between the various units in the gas turbine plant, as the flue gas from the combustion chamber (10) is cleaned of CO2 before the flue gas is released into the atmosphere, characterized in that the thermal power plant further comprises a second combustion chamber (10') equipped with a flame tube (40') and a surrounding jacket 27), the thermal power plant being configured so that the flue gas from the second combustion chamber (10'), after it has cooled down , is used to cool down the flame tube (40,40') in at least one of the combustion chambers (10,10'), preferably both, and that the flame tube (40,40') is equipped with a number of openings for supplying the recycled, uncleaned flue gas into the flame tube (40) through openings therein to cool the combustion process and to mix with the combustion products. 9. Power plant according to claim 8, which is configured so that recycled flue gas is compressed and where CO2 is concentrated to a level that lies within the operating conditions of the combustion chamber (10, 10'). 10. Power plant according to claim 8 or 9, which is configured so that recycled flue gas is supplied to the jacket (27) in the area of the combustion chamber (10) outlet and that the flue gas flows towards the primary zone of the combustion chamber so that optimal cooling of the flame tube can take place. 11. Power plant as stated in one of the claims (8-10), which is configured so that the turbine plant comprises two cross-connected gas turbine plants where both gas turbine plants (12,12') are driven by unclean flue gas from the combustion chamber (10,10'), as the combustion chambers ( 10,10') is supplied with air supplied from the compressor part (13) of the first turbine plant (12). 12. Combustion chamber for use in a heat or gas power plant comprising at least two gas turbine plants or a combined cycle gas turbine plant, where said combustion chamber (10,10') comprises a flame tube (40,40') and a surrounding jacket (27) for forming an annular space around the flame tube (40, 40'), characterized in that the flame tube (40, 40') is designed with a plurality of openings, which are arranged at least in the area of the primary combustion zone of the combustion chamber (10, 10') so that the cooling gas is brought to flow through the jacket (27,27') in the same direction as the combustion products, and so that the recycled flue gas helps to cool the combustion process and mix with the combustion products, and that fresh air is fed directly together with fuel centrally into the flame tube (40,40 ') to ensure near stoichiometric combustion. 13. Combustion chamber according to claim 12, where the intake for the recycled exhaust gas is arranged in the area at the outlet of the combustion products so that the cooling gas is caused to flow through the jacket (27, 27') in the opposite direction to the combustion products.