Application analysis of gas turbine in cogeneration project

abstract:

Gas turbine is the core power equipment of energy efficient conversion and clean utilization system in 2 1 century or even longer. This paper introduces the development status of gas turbine and its application in cogeneration projects, briefly describes the basic combination mode of combined cycle and simple cycle gas turbine power plants, and lists several main gas turbines currently used in cogeneration projects. This paper expounds the advantages of gas turbine over conventional thermal power units, analyzes the factors influencing the popularization of gas turbine in cogeneration projects, and looks forward to the development of gas turbine in China.

Key words:

Gas turbine; Combined cycle power plant; Waste heat power generation

China Library Classification Number: TK 479 Document Identification Number: A.

Application analysis of gas turbine in heat supply

Cogeneration project

Sun Peifeng, Jiang Zhiqiang

(1. China United Engineering Company, Hangzhou, China 310022;

2. china huadian corporation, China, Beijing 10003 1)

abstract:

Gas turbine is the core equipment of efficient and clean energy system in 2 1 century or even longer. The development status of gas turbine and its application in cogeneration projects are introduced. This paper briefly introduces two application forms of gas turbines in cogeneration projects, namely simple cycle gas turbine power plant and combined cycle power plant, and lists the gas turbines widely used in cogeneration projects at present. The advantages of gas turbine power station compared with conventional coal-fired units are expounded, and the factors affecting the application of gas turbine are analyzed. In addition, the development prospect of gas turbine in China is evaluated.

Key words:

Gas turbine; Combined cycle power plant; Cogeneration

Gas turbine consists of compressor, combustion chamber, turbine, control system and auxiliary equipment. The design of gas turbine is based on Brighton cycle. Compressors (that is, compressors) continuously suck air from the atmosphere and compress it. Compressed air is sent into the combustion chamber, mixed with injected natural gas, and ignited for combustion; The high-temperature flue gas generated after combustion immediately flows into the gas turbine to expand and do work, pushing the turbine to drive the compressor impeller to rotate together. The working capacity of the heated high-temperature gas is significantly improved. Therefore, while the turbine drives the compressor, there is still surplus work as the output work of the gas turbine.

Because the working medium of gas turbine is high temperature flue gas instead of steam, it can save large equipment such as boiler, condenser and water treatment. Therefore, the gas turbine power station has few ancillary equipment, simple system and small floor space.

Gas turbines can be divided into three categories: heavy-duty gas turbines, industrial gas turbines and aviation modified gas turbines. Heavy gas turbine parts are heavy, with long overhaul period and service life exceeding 654.38+10,000 h, which is mainly used to meet the needs of urban public power grid. For example, Hitachi's H25 and H80 series gas turbines, GE's F-class gas turbines, Siemens' SGT-8000 series gas turbines, Mitsubishi's M70 1 series gas turbines and Alstom's GT series heavy-duty gas turbines, etc. Industrial gas turbine has compact structure, good general material and high efficiency. For example, Sola's T 130 gas turbine and Siemens' SGT-800 gas turbine are often used in cogeneration projects. Aeronautical modified gas turbine is a gas turbine modified from aero-engine, which is widely used in aviation field, power generation and related industrial fields, such as LM series aero modified gas turbine of General Electric. Aeronautical modified gas turbine is the most compact, lightest and most efficient, but its service life is short [65438+].

Gas turbines have developed rapidly since their birth in the 1930s. The latest G-type gas turbines and H-type gas turbines in the world today have a single power of 292~334 MW and a thermal efficiency of 39.5%. Among them, the single unit power of combined cycle composed of G gas turbine can reach 489 MW, and the thermal efficiency of power generation can reach 58.7%. The thermal efficiency of the combined cycle unit composed of H-type gas turbines can reach 60% [3-5]. The combined cycle unit composed of H-type gas turbine is the largest commercial power generation mode with the highest thermal power cycle efficiency at present. Moreover, compared with steam turbines using coal as fuel, gas turbines have the advantages of light weight, small volume, high efficiency, little pollution and flexible start and stop. The gas turbine generator set can be started quickly without external power supply. Good handling. Widely used in power grid to drive peak load, as emergency standby power supply, it can also carry intermediate load, which can better ensure the safe operation of power grid [6].

Scientific and industrial circles at home and abroad have recognized that gas turbines will be the core power equipment of energy efficient conversion and clean utilization system in 2/kloc-0 century or even longer. Application mode of gas turbine in cogeneration project. 38660.88868888666

There are two main application forms of gas turbine in cogeneration projects: one is gas turbine combined cycle thermal power plant; The other is a gas turbine simple cycle thermal power plant.

The gas turbine combined cycle thermal power plant consists of gas turbine, waste heat boiler, steam turbine (back pressure type, back pumping type or condensing type) and generator. The high-temperature flue gas discharged from the gas turbine recovers the heat in the flue gas through the waste heat boiler to obtain high-temperature steam, which is injected into the steam turbine to generate electricity. The exhaust steam of the steam turbine or part of the steam extracted after doing work in the steam turbine is used for heating. The forms are as follows: the gas turbine and the steam turbine coaxially push the single-shaft combined cycle of the generator; The gas turbine and steam turbine drive the multi-shaft combined cycle of their respective generators. Single-shaft gas turbine combined cycle power plants are relatively large, such as 9F series units of General Electric. Multi-shaft combined cycle units are common in small and medium-sized gas turbine combined cycle power plants. Therefore, for cogeneration projects with relatively small scale in power plants, multi-shaft gas turbine combined cycle units are often selected.

Gas turbine simple cycle thermal power plant consists of gas turbine and waste heat boiler. This type of gas turbine thermal power plant is not equipped with a steam turbine, but directly supplies heat to the outside through a waste heat boiler. Therefore, the thermal efficiency of this type of gas turbine thermal power plant is lower than that of combined cycle gas turbine thermal power plant, about 30% ~ 35%. In terms of thermoelectric ratio and heating cost, simple cycle gas turbine thermal power plant is also lower than combined cycle gas turbine thermal power plant [7].

It can be seen that the combined cycle of gas turbine can greatly improve the overall thermal efficiency of the power plant. Even the simple cycle gas turbine power plant without steam turbine, which is composed of gas turbine and waste heat boiler, has higher power generation efficiency than the conventional small coal-fired power plant.

2 Selection of gas turbines in cogeneration projects

Cogeneration projects followed? Set electricity by heat? In principle, the external demand for steam load is met first, and the general demand for power generation is relatively small. Therefore, for cogeneration projects, the use of high-power heavy-duty gas turbines is relatively small, and some small and medium-sized gas turbines are often equipped.

The main small and medium-sized gas turbines in the world are: Sola's T 130 gas turbine; Hitachi H25 and H80 gas turbines; 6F and LM series aero-modified gas turbine engines of General Electric Company: Siemens SGT-800 gas turbine. See table 1 for the main technical parameters of each model (see next page) (the data in the table comes from the product manuals of various gas turbine manufacturers, which will change slightly due to the calculated natural gas calorific value and other parameters).

Table 1 Relevant performance parameters of small and medium-sized gas turbines

Tab. 1

Performance parameters of some gas turbines

In table 1, H25, H80 and 6F are heavy gas turbines; SGT-800 and T 130 are industrial gas turbines; LM6000 is an aviation modified gas turbine. From the table 1, it can be seen that the single power generation efficiency of industrial and aviation modified gas turbines is obviously higher than that of heavy gas turbines, but the exhaust temperature of gas turbines is relatively low. Because the high-temperature flue gas discharged into the waste heat boiler contains relatively little heat, the overall power generation efficiency of industrial and aviation modified gas turbine combined cycle thermal power plants is low [8-9]. Simple cycle gas turbine thermal power plant

For gas turbine combined cycle with steam turbine, the flue gas temperature of heavy gas turbine is higher than that of industrial gas turbine and aviation modified gas turbine, and the high-temperature flue gas discharged into waste heat boiler contains relatively more heat, and the waste heat boiler also produces more high-temperature and high-pressure steam for steam turbine power generation. Therefore, the overall power generation efficiency of heavy gas turbine combined cycle is higher than that of industrial gas turbine and aviation modified gas turbine. Most gas turbine combined cycle thermal power plants choose heavy gas turbines.

From the point of view of full utilization of energy and cascade utilization, gas turbine combined cycle thermal power plant has more advantages than gas turbine simple cycle thermal power plant. At present, the gas turbine combined cycle thermal power plant composed of heavy gas turbines is mostly used in China's gas turbine cogeneration projects. For example, a thermal power plant in Zhejiang uses a 6F-class gas turbine to match a waste heat boiler and a steam turbine to form a gas turbine combined cycle unit for external heating and power supply. The overall thermal efficiency of the gas turbine combined cycle thermal power plant is about 60%.

However, for some occasions with strict requirements on floor space, such as offshore oil and gas platform wells, industrial gas turbines with compact structure and high efficiency or aviation modified gas turbines can generally be selected.

The selection of specific gas turbine model number can be determined according to the actual situation of each project, such as external heating parameters, heating capacity, installed capacity, number of units, floor space and overall thermal efficiency.

3 Advantages of gas turbine combined cycle cogeneration project over conventional cogeneration [10]

Compared with the traditional coal-fired small thermal power cogeneration power plant, the advantages of gas turbine combined cycle thermal power plant mainly include:

(1) high efficiency: the thermal efficiency of gas turbine combined cycle reaches or even exceeds 60%, which is unmatched by general conventional thermal power units, even higher than the most advanced ultra-supercritical units at present, ranking first among all kinds of thermal power units.

(2) Low unit cost: The unit capacity cost of gas turbine combined cycle unit is about 400 USD? KW- 1, while the cost of conventional thermal power units is 600 ~ 1, 000 USD? kW- 1； If the manufacturing and processing level of domestic gas turbines in China is further improved, the unit capacity cost of gas turbine combined cycle units still has a great room for decline.

(3) Low emission: gas turbine combined cycle does not emit SO2, fly ash and ash; The emission of nitrogen oxides is also very low, generally reaching 49.20 mg? M-3, even below 30.75 mg as required? At M-3 level, the CO2 emission can be11.25mg? m-3； The environmental protection performance is superior to that of existing thermal power units.

(4) Water saving: Gas turbine combined cycle units mainly generate electricity, and the power of gas turbine generators accounts for 70% of the total capacity. The water consumption of combined cycle units is about 1/3 of that of conventional coal-fired units. This is especially important in some water-deficient areas. If the simple cycle with gas turbine and waste heat boiler is selected, the cooling water demand of the whole power plant will be greatly reduced compared with that of the conventional thermal power plant.

(5) Land saving: The gas turbine combined cycle unit does not need coal storage yard and coal conveying facilities, and its floor space is only 1/3 of that of conventional thermal power plants with desulfurization devices. This is particularly important in heating power plants in cities and urban fringe. (6) Short construction period: The gas turbine combined cycle unit is most suitable for modular design, and each module of the gas turbine can be produced in the factory and transported to the site for hoisting, which greatly shortens the fuel gas.

(7) Good peak shaving performance: Through the bypass chimney of the waste heat boiler, the load of the gas turbine and generator set can reach 100% within 20 minutes without running the steam turbine and generator set, and the load of the gas turbine and generator set accounts for about 70% of the rated load of the whole gas turbine combined cycle power plant, which ensures the good regulation performance of the gas turbine combined cycle and realizes the functions of day start and night stop and peak shaving of the unit.

(8) Less operation and maintenance personnel: Due to the high degree of automation of the gas turbine combined cycle power plant and the adoption of advanced control system, the demand for the number of employees in the power plant is greatly reduced. Generally, 20% ~ 25% employees are enough for conventional coal-fired power plants with the same capacity.

4 Main factors affecting the promotion of gas turbines in cogeneration projects

The gas turbine combined cycle power plant has been widely developed abroad, occupying an important position in the American power market in recent years, and the gas turbine combined cycle power plant in Europe has also made great progress. At present, whether China's gas turbine combined cycle power plant can be vigorously promoted and developed is mainly subject to the following three factors:

(1) How much natural gas resources can China provide for the gas turbine power generation industry; At present, some gas turbine combined cycle power plants in China are limited by fuel supply, and their annual operation time is far less than that of conventional coal-fired units.

20 12, with? West-to-East Gas Transmission? When the last trunk lines of the second line are completed and put into operation, the whole gas pipeline will transport 30 billion cubic meters of natural gas every year. Even planning and construction in China in the future? Four lines? Or? Line 5? Further promote the transportation of natural gas from the western region to the eastern region for development and utilization.

In addition, the development of offshore natural gas (East China Sea and South China Sea) and the import of liquefied natural gas (LNG) from coastal port cities have also expanded the gas supply conditions for combined cycle power generation. The reserves of three major coalbed methane resources in North China, Northeast China and Northwest China have been proved and will be gradually exploited.

With the expansion of natural gas source channel, the application scope of gas turbine combined cycle power plant will greatly break through the influence area of west-east gas pipeline network and offshore natural gas.

(2) How to reasonably determine the price of natural gas, so that the cost of gas turbine combined cycle power generation can compete with the conventional thermal power with serious pollution using coal as fuel.

It must be pointed out that the price of natural gas has a decisive impact on the operating costs of gas turbines and combined cycles. Among the three major power generation costs of gas turbines (equipment depreciation cost, unit operation and maintenance cost and fuel cost), the fuel cost accounts for 60% ~ 65%. Even in the origin of natural gas, the cost of transportation process is greatly reduced, and the price of natural gas is cheaper than that in the southeast coastal areas, and its cost still accounts for a very high proportion of the power generation cost of gas turbines [4].

At present, as an important part of industrial enterprises and urban infrastructure, many small and medium-sized coal-fired power plants are usually located in cities or suburbs, which will inevitably have a great impact on the local atmospheric environmental quality. The transformation of small and medium-sized coal-fired power plants into gas turbine combined cycle power plants has a very obvious effect on improving local environmental quality, which is most easily accepted and supported by the public.

The fuel of thermal power plant is changed from coal to natural gas. Although the energy structure has been adjusted reasonably, the energy utilization efficiency has been improved, and the loss and waste in coal transportation have been reduced, the fuel cost is bound to increase for gas-turbine combined cycle thermal power plants, so it is a reasonable way to solve the relationship between natural gas market and cost by striving for the understanding and participation of the masses and enterprises.

The government should consider the environmental benefits of gas turbine when setting the on-grid electricity price and steam supply price of gas turbine combined cycle thermal power plant, and appropriately raise the on-grid electricity price and steam supply price, which is also a digestion of the high cost of natural gas.

(3) In the long run, the improvement of the overall industry level of China's gas turbines is an important factor that determines whether China's gas turbines and combined cycle power plants can be vigorously promoted.

The development level of gas turbine represents the overall level of a country's major equipment manufacturing industry. At present, there is a big gap between China's gas turbine technology level and the world's advanced level. The core components of gas turbines depend on imports, and the cost of each overhaul of gas turbines is very high. If some gas turbines can only be shipped back to developed countries such as the United States, the cost will be higher.

In recent years, in order to promote the development of gas turbine industry, according to? Market for technology? What are the principles of batch construction in China gas turbine power station project planning? Bound? Bidding procurement mode is that foreign advanced gas turbine manufacturing enterprises and domestic manufacturing enterprises unite with each other to form a consortium to conduct competitive bidding for gas turbine combined cycle power plant projects in order to absorb and introduce foreign advanced technology. In this process, China also imported F-class heavy gas turbines from the world's three major power groups (General Electric, Siemens and Mitsubishi). Good achievements have been made in the localization of gas turbine equipment manufacturing and the development of domestic gas turbine technology. On the basis of absorbing and introducing foreign advanced gas turbine technology, the localization of equipment research and development of gas turbine combined cycle power station and the autonomy of intellectual property rights have been gradually realized [1 1-65438+].

In 2008,110mwr0110 gas turbine with completely independent intellectual property rights in China was ignited and verified by experiments. Its performance is close to the current international advanced F-class gas turbine, which greatly improves the overall level of gas turbine design, manufacture and processing in China [13-65433].

At present, the gap between China's gas turbine technology level and the international advanced level is narrowing, and China's gas turbine has made great progress in independent research and development and manufacturing. September 12, 12, major project of Shanghai science and technology commission? Research on manufacturing technology of superalloy blades? Through expert acceptance, this marks a solid step on the road of localization and independent production of gas turbine core components in China.

From the three factors that restrict the development of gas turbine combined cycle power station and the corresponding situation in China at present, we can know that the conditions for vigorously developing gas turbine combined cycle power station in China are already met, and the rapid development of gas turbine combined cycle power station will become possible in the near future.

5 abstract

Realizing energy conservation and emission reduction and improving energy utilization rate are the goals of energy structure adjustment in China. With the development and utilization of natural gas resources and the introduction of liquefied natural gas resources, the number of gas turbine combined cycle units in China will continue to increase. The gas turbine combined cycle will become a type of power plant that will be developed vigorously in China in the future because of its high efficiency, cleanness and flexibility.

At present, the capacity of small and medium-sized gas turbines used for cogeneration and the heating capacity of the whole thermal power plant are very close to the specifications of steam turbine thermal power units widely used in China. Therefore, under the premise of not changing the external system, increasing the power generation capacity and uninterrupted heating and power generation, the transformation of replacing coal with gas in thermal power plant can be realized in a short time, with less investment and reasonable electricity and heat costs. This is also a realistic condition for the gas turbine combined cycle thermal power plant to be vigorously promoted.

In short, the role of gas turbine combined cycle units in China's power industry will be gradually enhanced, and the development of gas turbine combined cycle thermal power plants has a long way to go, but the prospects are very bright.

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