CN106090971A - A kind of combined steam flue gas MGGH system and method - Google Patents

Abstract

A combined steam-flue gas MGGH system. A flue gas cooler is installed on the connecting flue between the boiler air preheater and the dust collector, and a flue gas reheater is installed on the connecting flue between the desulfurization device and the chimney. An auxiliary heat exchanger is installed on the circulating water pipe of the hot section between the gas cooler and the flue gas reheater; the connected circulating water pipe and the inlet and outlet are arranged between the flue gas cooler, the flue gas reheater and the auxiliary heat exchanger The valve adjustment system is also connected to the auxiliary heat exchanger with a steam inlet pipe, a drain outlet pipe, a condensate inlet pipe, a condensate outlet pipe and a valve switching adjustment system for controlling the inflow of steam or condensate, which realizes various working conditions. It can automatically control the inlet temperature of the electrostatic precipitator flue gas, and automatically control the discharge temperature of the chimney. It has the technical effects of saving coal, water and reducing flue gas emissions while meeting the environmental protection requirements for flue gas emissions.

Description

A combined steam flue gas MGGH system and method

technical field

The invention relates to a thermal power plant ultra-low emission MGGH (intermediate heat medium flue gas heat exchanger: Media Gas-GasHeater) energy-saving and environmental protection equipment and method, and belongs to the technical field of thermal power plant ultra-low emission MGGH.

Background technique

The issue of ultra-low emissions from boilers in coal-fired power plants has been paid attention to by the state. In economically developed regions such as the Yangtze River Delta and the Pearl River Delta, considerable attention has been paid to white smoke from chimneys. The use of MGGH is becoming more and more common due to the inability to achieve ultra-low emissions due to leaks in previously used GGH systems.

Flue gas desulfurization (FGD for short). Lime-gypsum wet flue gas desulfurization technology of coal-fired flue gas is currently the most widely used and most efficient desulfurization technology. For coal-fired power plants, FGD will be the main method to control SO2 emissions for a long period of time in the future. There are two main types of flue gas desulfurization: dry flue gas desulfurization and wet flue gas desulfurization. Among them, the process flow, form and mechanism of wet flue gas desulfurization are similar, mainly using slurry such as limestone (CaCO3), lime (CaO) or sodium carbonate (Na2CO3) as detergent to wash the flue gas in the reaction tower to remove SO2 in flue gas. This process has a history of 50 years. After continuous improvement and perfection, the technology is relatively mature, and has high desulfurization efficiency (90%-98%), large unit capacity, strong adaptability to coal types, low operating costs and The by-products are easy to recycle and so on. It is also the wet desulfurization process that greatly increases the moisture content of the flue gas after desulfurization. These flue gases are discharged from the desulfurization tower into the chimney to the atmosphere in the state of saturated wet flue gas, causing the spectacular phenomenon of white smoke from the chimney.

Since white smoke will be emitted from the chimney in the state of saturated wet flue gas, heating the net flue gas to make it out of the saturated state and then discharging can reduce the phenomenon of white smoke, thus using the heat of the flue gas in front of the desulfurization tower to heat the net after the desulfurization tower Flue gas, the wide application of MGGH technology came into being. After solving the key technical problems of flue gas low-temperature corrosion, the economy of the MGGH system is more important. How to improve the coal-saving benefits as much as possible while meeting the requirements of net flue gas emissions has become the goal pursued by the majority of electric power technicians

The existing MGGH (tubular flue gas heat exchanger, water medium flue gas heat exchanger, tubular GGH) system uses auxiliary steam heating in winter to adjust the flue gas temperature. When the whole system is running in summer, a large number of Exhaust exhaust heat enters the desulfurization exhaust along with the heat medium water, resulting in unnecessary waste of the assembly. At the same time, there is no means to adjust the outlet flue gas temperature of the flue gas cooler in front of the dust collector in summer. According to the existing design, the flue gas cooler needs to be designed with a large heat exchange area in summer working conditions, resulting in waste of metal materials. Didn't fit in. At the same time, it is necessary to control the inlet flue temperature of the dust collector. For the electrostatic precipitator, the temperature of the flue gas is reduced, the volume flow rate of the flue gas is reduced, the specific resistance of the dust is reduced, the efficiency of dust removal is improved, and the power consumption of dust removal is reduced. For the bag dust removal device, the temperature of the flue gas is controlled to prevent the entry of over-temperature flue gas, which ensures the safety of the device and reduces the power consumption of dust removal. The current MGGH system has poor ability to adapt to seasonal changes.

Contents of the invention

The purpose of the present invention is to solve the problem that the existing MGGH has poor ability to adapt to seasonal changes. The invention adopts heat medium water to be heated by auxiliary steam in winter and low-heating condensed water in summer, together with a flue gas cooler and a flue gas heater, it solves the problem of low temperature of desulfurization and exhaust gas in existing power plants.

In order to solve the above technical problems, the technical solution of the present invention is to provide a combined steam flue gas MGGH system. A flue gas cooler is installed on the connecting flue between the boiler air preheater and the dust collector, and a flue gas cooler is installed between the desulfurization device and the chimney. A flue gas reheater is set on the connecting flue between the flue gas coolers and a flue gas reheater, and a dust collector, an induced draft fan and a desulfurization device are set between the flue gas cooler and the flue gas reheater. An auxiliary heat exchanger is installed on the circulating water pipeline in the hot section; a connected circulating water pipeline and an inlet and outlet valve adjustment system are installed between the flue gas cooler, flue gas reheater and auxiliary heat exchanger. It is also connected with a steam inlet pipe, a drainage outlet pipe, a condensate inlet pipe, a condensate outlet pipe and a valve switching adjustment system for controlling the inflow of steam or condensate.

Also provided is a method for operating a combined steam flue gas MGGH system, including the following steps:

Set the inlet smoke temperature of the dust collector to a predetermined value to realize low-temperature electric dust removal;

Set the exhaust gas temperature of the chimney to a predetermined value to eliminate the phenomenon of white smoke;

During winter operation, the auxiliary heat exchanger in the flue gas MGGH system is connected to supplementary heat steam to implement the working mode of steam supplementary heat;

During summer operation, the auxiliary heat exchanger in the flue gas MGGH system is connected to condensed water to use condensed water to absorb heat;

When a malfunction occurs or the auxiliary heat exchanger does not need to be put into use, the associated bypass can be opened through the pipeline valve, the parallel bypass valve of the auxiliary heat exchanger can be opened, and the auxiliary heat exchanger is not put into use.

Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a combined steam-flue gas MGGH system, realizes steam-assisted heating and condensed water heat absorption switching, and ensures that ambient temperature changes and unit changes can be offset under various working conditions The impact of load changes on the exhaust gas temperature of the boiler, no matter how the ambient temperature changes, no matter how the unit load changes, it can automatically control the inlet temperature of the electric precipitator flue gas under various working conditions, and automatically control the discharge temperature of the chimney. While meeting environmental protection requirements, it has the technical effects of saving coal, water, and reducing flue gas emissions.

Description of drawings

Fig. 1 is a structural representation of the present invention

Among them: dust collector 2, induced draft fan 3, desulfurization device 4, chimney 9, flue gas cooler 1, flue gas reheater 5, circulating water pump 6, auxiliary heat exchanger 7, low pressure heater 8

detailed description

In order to make the present invention more comprehensible, preferred embodiments are described in detail below with accompanying drawings.

As shown in Figure 1, this embodiment provides a combined flue gas MGGH system. A flue gas cooler 1 is installed on the connecting flue between the boiler air preheater and the dust collector, and a flue gas cooler 1 is installed between the desulfurization device 4 and the chimney. A flue gas reheater 5 is installed on the connecting flue, an auxiliary heat exchanger 7 is installed on the hot section circulating water pipe between the flue gas cooler 1 and the flue gas reheater 5, and an auxiliary heat exchanger 7 is installed between the flue gas cooler 1 and the flue gas reheater. A dust collector 2, an induced draft fan 3 and a desulfurization device 4 are installed between the heaters 5, and a variable frequency circulating water pump 6 is installed on the cold section circulating water pipeline between the flue gas cooler 1 and the flue gas reheater 5, as shown in the figure Between the flue gas cooler 1, the flue gas reheater 5, and the auxiliary heat exchanger 7, a circulating water pipe and an inlet and outlet valve adjustment system are arranged, and the auxiliary heat exchanger 7 is also connected with a steam inlet pipe, a drain Outlet piping, condensate inlet piping, condensate outlet piping, and a valve switching regulation system for controlling inflow of steam or condensate.

A bypass pipe connected in parallel with the auxiliary heat exchanger is also provided on the circulating water pipe of the hot section between the flue gas cooler 1 and the flue gas reheater 5, and the auxiliary heat exchanger is switched to use or bypass by using a regulating valve.

The condensate inlet pipe and condensate outlet pipe are drawn from the inlet and outlet ends of the first-stage low-pressure heater, respectively connected to the steam inlet pipe and drain outlet pipe of the auxiliary heat exchanger, and the regulating valve is used to control the switch to enter the auxiliary heat exchanger heating steam or condensed water.

By connecting the condensed water pipeline from the low-pressure heater to the existing flue gas cooler, flue gas heater, and auxiliary heat exchanger system, the auxiliary heat exchanger can be replaced by using steam to heat the flue gas cooler and flue gas in winter. The heat medium circulating water in the gas heater, and the seasonal adaptive heat exchanger for heating the condensed water by using the heat medium circulating water in the flue gas cooler and flue gas heater in summer.

A combined steam flue gas MGGH operation method comprises the following steps:

Set the flue gas temperature at the inlet of dust collector 2 to 90°C (or a certain required data between 85°C and 95°C) to realize low-temperature electric dust removal;

Set the exhaust gas temperature of the chimney to 80°C (or a certain required value) to eliminate the phenomenon of white smoke;

During winter operation, adjust the circulating water volume of the heat medium water system according to the flue gas temperature at the outlet of the flue gas cooler (the flue gas temperature at the inlet of the electrostatic precipitator). The flue temperature at the inlet and outlet of the reheater is used as a feed-forward) to adjust the amount of supplementary heating steam. Supplementary heating steam can be regulated by inlet steam regulating valve.

During summer operation, adjust the circulating water volume of the heat medium water system according to the flue gas temperature at the outlet of the flue gas reheater (the flue gas temperature at the chimney inlet). The flue gas temperature at the outlet of the device is used as feed-forward) to adjust the condensate flow from the low-pressure heater, and the condensate in the branch of the low-pressure heater is adjusted by means of a frequency conversion water pump and a regulating valve.

When adapting to the heat exchanger in spring and autumn or when the season does not need to be put into use, open the parallel bypass valve of the auxiliary heat exchanger and not put into use the auxiliary heat exchanger.

During specific implementation, by detecting parameters such as the flue gas inlet and outlet temperature of the flue gas cooler 1 and the flue gas reheater 5, heat medium water, condensed water inlet and outlet temperature, and the flue gas temperature flow, heat medium water flow temperature, Signals such as condensate flow and temperature are input into the control system, and the control system controls the operation of the entire system.

According to the flue gas inlet and outlet flow and temperature of the flue gas cooler and flue gas reheater and the heat medium water inlet and outlet flow, temperature, steam parameters, condensed water flow temperature, automatically adjust the supplementary heating steam flow or low-pressure heating The condensed water flow rate of the flue gas reheater is adapted to the heat required by the flue gas reheater. At the same time, the temperature of the heat medium water inlet of the flue gas reheater 5 is controlled at about 95°C to ensure that the temperature of the flue gas entering the chimney 10 is at 80°C. ℃ or so.

The incoming steam flow is regulated by valves, and the condensed water flow from the low-pressure heater is regulated by the inlet pipe pump and valves.

When a malfunction occurs or the auxiliary heat exchanger does not need to be used, the associated bypass can be opened through the pipeline valve, and the parallel bypass can be used to maintain the normal operation of the system.

Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be based on the scope defined by the claims of the present invention.

Claims (10)

1. a combined steam flue gas MGGH system, the connection flue between boiler air preheater and cleaner unit arranges flue gas Cooler, the connection flue between desulfurizer and chimney arranges smoke re-heater, at gas cooler and flue gas reheat Cleaner unit, air-introduced machine and desulfurizer are set between device, it is characterised in that the heat between gas cooler and smoke re-heater On section circulating water pipeline, supplementary heat exchanger is set；Following of connection is set between gas cooler, smoke re-heater, supplementary heat exchanger Ring waterpipe and terminal valve regulation system, be also connected with being provided with steam inlet, hydrophobic outlet on supplementary heat exchanger Pipeline, condensation water inlet pipeline, condensation water exit conduit and control flow into the valve transfer of steam or condensation water and regulate system.

Combined steam flue gas MGGH system the most according to claim 1, it is characterised in that gas cooler and flue gas reheat Also set up the bypass duct in parallel with supplementary heat exchanger on circulating water pipeline between device, utilize control valve to change to switch auxiliary The coming into operation or bypassing of hot device.

Combined steam flue gas MGGH system the most according to claim 1, it is characterised in that at gas cooler with flue gas again On cold section of circulating water pipeline between hot device, water circulating pump is set；Use variable frequency pump.

Combined steam flue gas MGGH system the most according to claim 1, it is characterised in that in entering of one-level low-pressure heater Mouth end and the port of export are drawn and are condensed water inlet pipeline, condensation water exit conduit, are connected respectively to the steam inlet of supplementary heat exchanger Pipeline and hydrophobic outlet conduit, utilize control valve to control to switch into adding vapours or condensing water of supplementary heat exchanger.

Combined steam flue gas MGGH system the most according to claim 4, it is characterised in that low-pressure heater branch road condenses water Variable frequency pump and regulation valve mode is used to regulate.

6. an operation method for combined steam flue gas MGGH system, comprises the steps:

Cleaner unit import cigarette temperature is set as predetermined value, it is achieved low temp. electric dedusting；

Chimney emission temperature is set as predetermined value, eliminates and emit white cigarette phenomenon；

During winter operation, the supplementary heat exchanger in flue gas MGGH system accesses heat recovery steam to carry out utilizing steam concurrent heating Working mould Formula；

During summer operation, the supplementary heat exchanger in flue gas MGGH system accesses condensation water to carry out utilizing condensation water heat absorption Working mould Formula；

When break down work or be not required to come into operation supplementary heat exchanger time, can by pipe valve open association bypass, open auxiliary Heat exchangers in parallel bypass valve, do not come into operation this supplementary heat exchanger.

The operation method of combined steam flue gas MGGH system the most according to claim 6, it is characterised in that winter operation Time, regulating heat medium water system quantity of circulating water according to gas cooler exit gas temperature, quantity of circulating water can pass through frequency conversion recirculated water Pump is adjusted, and regulates heat recovery steam amount according to smoke re-heater inlet water temperature.

The operation method of combined steam flue gas MGGH system the most according to claim 7, it is characterised in that the most further may be used Utilize electric precipitation inlet flue gas temperature to regulate heat medium water system quantity of circulating water, utilize smoke re-heater to import and export cigarette temperature as feed-forward regulation Heat recovery steam amount, heat recovery steam can use inlet steam to regulate valve regulation.

The operation method of combined steam flue gas MGGH system the most according to claim 6, it is characterised in that summer operation Time, regulating heat medium water system quantity of circulating water according to smoke re-heater exit gas temperature, quantity of circulating water can pass through frequency conversion recirculated water Pump is adjusted, and regulates the condensing water flow from low-pressure heater according to gas cooler inlet water temperature.

The operation method of combined steam flue gas MGGH system the most according to claim 9, it is characterised in that the most further Available chimney inlet flue gas temperature regulation heat medium water system quantity of circulating water, utilizes gas cooler outlet cigarette temperature to coagulate as feed-forward regulation Bearing water flow, low-pressure heater branch road condenses hydromining variable frequency pump and regulation valve mode regulates.