CA2241986A1

CA2241986A1 - Boiler firing method

Info

Publication number: CA2241986A1
Application number: CA002241986A
Authority: CA
Inventors: Evgeny Ivanovich Karpenko; Sergei Lubsanovich Buyantuev; Vladimir Efremovich Messerle
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-01-03
Filing date: 1996-01-03
Publication date: 1997-07-17
Also published as: WO1997025571A1; CN1207167A; DE19681723T1

Abstract

The invention is in the field of power engineering and can be used in thermal power plants to fire up boiler units without using fuel oil from a cool state to a working regime. The aim is to eliminate the need for fuel oil for firing coal-dust torches, thereby enhancing the efficiency of the boiler firing process. The proposed technology for firing industrial boilers without fuel oil is based on plasma fuel ignition techniques. A successful result is achieved when the coal-dust torch is fired by generating a stream of low-temperature plasma using plasma generators installed in the muffles of the lower-tier coal-dust burners, feeding the coal-dust mixture through the low-temperature plasma stream and igniting it and by subsequent switching off of plasma generators. In addition, depending on the type of boiler unit, pulverisation techniques and fuel characteristics, the quantity (n) of coal-dust burners equipped with plasma generators and muffles can be in the range of n = 1 m, where m is the quantity of burners on the lower tier.

Description

~ CA 02241986 1998-06-30 S A METHOD OF FIRING A BOILER UNIT

Field of the Invention This invention relates to power engineering and may be used in heat power plantsfor fuel oil - free firing up of a boiler unit from the cold state to operating conditions thereof.

Description of Prior Art Known is a method of firing low grade Donetsk AIII coal and stabilizing burning thereof (Sh. Sh. Ibraev, M. M. Golijachek N. A. Novokov, T. M. Sejtinov "Plzmennaja goreLka s istochnikom pitanija dlija rozzhiga i stabilizatsiji Donetstkogo AIII"/
"A Plasma Torch with a Feeding S~e for Firing and ~tabilizing Donetsk AIII"
{"Plazmennoje vosplamenenie i ~7hig~nie topliva"/"Plasma-type Ignition and Fuel Combustion"}, Theses of Reports of ~tercollege Scientific - and - Technical Conference, Makarov's NKI, the city of Nikolaev, 1989, pages 33 - 34), which method comprises the steps of prep~g an aelo~lule, dividing said aero~ ure flow into main and stabilizing flows, delivering both of ~e flows to a pulverized coal burner through pipe lines, heating the stabilizing flow and firing up the main flow. An electric arc plasma generator is used for heating the stabilizing flow in which plasma generator a portion of the arc column is blown out by air into the pulverized coal flow. A two -component fuel compri~in~ fuel gas and heated coking residue is formed in the process of the stabilizing flow heating which fuel, being supplied into the fire box, provides firing of the main flow and stabilizing burning thereof.
However, the known method of firing does not provide high efficiency of the process due to the fact that only a portion of the arc column is blown out into the pulverized coal flow, while the rest of the arc remains in the chamber of plasmagenerator. As the result, this method is of a low effect for performing firing of power boilers.

' CA 02241986 1998-06-30 A number of methods of plasma ignition of coals are known in the art which methods comprise generating of electric arc, heating pulverized coal mixture in arc 5 plasma, firing and stabilizing burning a pulverized coal flare (Great Britain Patent No. 1585943, 1981).
However, the known methods of i~ni~ing are only effective in burning of high -grade coals having high yield of volatile matters. When low - grade coals are burnt in boiler units the power of an ignition torch is not sufficient.
A method of firing and stabilizing burning of a pulverized coal flare in a boiler unit (boiler unit firing) by burning fuel oil or natural gas is the most close one to the proposed invention. Starting or gas nozzles are either mounted together with main coal burners, or are installed additionally thereto. For example, boiler unit PK - 39 is provided with 12 main pulverized coal burners having the efficiency of 8 t/h and 8 fuel 15 oil nozzles having the efficiency of 1.3 t/h. When fuel oil and coal are supplied into a fire box the high reactive liquid fuel is ignited. A subst~n~i~l amount of heat is released in the process of fuel oil burning by which coal dust is heated. As the result of heating of the coal particles volatile matters evolve and the temperature of the solid fuel increases. At the same time the ignition of the coal particles occurs and intensive firing 20 and stabilizing burning of a pulverized coal flare are performed ("Kotelnije i lu~bi~ ije ustanovki energoblokov moshnostiju 500 i 800 MW"/"Boiler and Turbine In~t~ ons of Power Generating Units of 500 and 800 MW Capacity", Edited by V. E. Doroshuk and V. B. Ruban, Moscow, "Energija" Publishing House, 1070).
However, the known method of firing a boiler unit involves the use of valuable 25 fuel oil, as well as difficulties due to complexity of fuel oil equipment operation, especially in winter time when it is necessary to heat up fuel oil constantly. Besides that when coal and fuel oil are burnt together combustible losses (incomplete burning of carbon) in a fire box are increased, the effluent of nitrogen and sulfur oxides is increased as well, the corrosion of surfaces under heating is growing and the reliability 30 of power equipment declines.
Thus, none of the known methods of plasma ignition of a fuel can be used for effective firing of a boiler when low grade power - generating coals are combusted.

Summary of the Invention The aim of the proposed invention is to exclude the use of fuel oil for firing apulverized coal flare and increase the efficiency of the process of firing a boiler unit.
This aim, set forth, is obtained by that in the method of firing a boiler unit comprising firing a pulverized coal flare, subsequent sequential feeding of pulverized coal mixture through nozzles of pulverized coal burners installed in the boiler unit in tiers, and firing said lllixlule in accordance with the present invention; the firing of the pulverized coal flare being performed by generating a low - temperature plasma jet by means of a plasma generators provided in the muffles of the pulverized coal burners of the low tier, feeding said pulverized coal nlixLul~ through the low - temperature plasma jet and igniting thereof, said plasma generators being switched off when the burning of the pulverized coal flare is stabilized and the operating parameters are reached.
Besides that, depending on the type of a boiler unit, a technology of coal pulverization and ffiel characteristics, a number (n) of pulverized coal burners equipped with plasma generators and muffles can be within the range of n = 1 . m, whereinm is a number of burners of the low tier.
The proposed technology of the ffiel oil - free firing of an industrial boiler unit is based on a method of plasma ignition of a ffiel. To realize said technology developed is a design of a combined plasma generator having power of 30 - 100 kW, as well as a preswitched muffle built - in into a burner and providing self-i~niting of the ~ e after said muffle is heated up by means of the plasma generator. The arrangement of the plasma generator, the muffle, power supply, electrical systems, gas systems and water supply systems, protection and control equipment located on the boiler unit is compact, does not block passes, create no difficulties to operating and m~ e.~ ce personnel and permits to control the firing system by one operator from a unit - type control panel.
Brief Description of the Drawings The essence of the invention is ffirther explained by the accompanying drawings,wherein:

. CA 02241986 1998-06-30 Fig. 1 schematically illustrates the arr~ngement of the low tier of the pulverized coal burners in the boiler unit;
Fig . 2 shows the cross section along line 1 - 1 to illustrate the design of a pulverized coal burner with a built - in plasma generator.

Preferable Embodiment of the Invention In order to realize the proposed method of firing boiler unit 1 certain pulverized coal burners 2 of the low tier of the power generating boiler are provided, in~te~d of fuel oil nozzles, with muffles 3 comprising a steel tube tenoned and coated with a layer of silicon - carbide abrasive (Carborundum) from the inside thereof so that the inner diameter of the muffle is not less than the inner diameter of pulverized coal duct 4 coming thereto. The end of the muffle is built - in into the ambrasure of boiler 1 between water - wall tubes. Plasma generator 5 in arranged in a special opening at the beginning of muffle 3 along the incoming pulverized coal stream.
The proposed method of firing a boiler unit is conducted in the following way.
Plasma generators 5 built - in into muffles 3 of pulverized coal burners 2 of the low tier are switched on and a low - tempcl~lule plasma jet is generated. Then a coal dust feeding mill is switched on and the pulverized coal mixture is supplied to muffles 3 of pulverized coal burners equipped with plasma generators 5. The pulverized coal stream passes right through the zone where the electric arc is burning and intensive gasification thereof, ignition of the aelolllixlule and firing of the pulverized coal flare takes place. When the burning of the pulverized coal flare is stabilized and theoperating parameters are reached plasma generators 5 are switched off. The muffle surface is heated up to a temperature sufficient for self - igniting the pulverized coal mixlule passing therelllrough and due to that stable burning of the pulverized coal flare is exhibited after switching off of the plasma generators. Then, sequential feeding of pulverized coal mixture into the boiler is performed through the nozzles of pulverized coal burners of the upper and low tiers where intensive i~;niting and burning of the fuel takes place.
With the decrease of int~n~ity of the pulverized coal flare burning the plasma generators are switched on again and the parameters of the flare are brought to operating values.

The method is illustrated by the following example of the actual embodiment of the invention.
The method of fuel oil - free firing has been realized in boiler unit TPE - 215 having the output of 670 tons of steam per hour. This boiler unit is equipped with 16 pulverized coal burners arranged in two tiers, 8 burners in each tier. Four burners of the low tier (cf. Fig. 1) have been provided with muffles 3 and plasma generators 5 having the capacity of 60 kW. The tests have been run using Tugnujsk coal with the 10 following characteristics: ash content: A = 14.1 %; moisture content: W = 10.5 %;
volatile matters output: V = 37.8%; heating efficiency: Q = 5484 kcaVkg.
Plasma generators S are started and the operating parameters are m~int~ined as follows: V operating = 300V and I operating = 200A. Then, the mill is switched on, the pulverized coal is fed to four burners of the low tier equipped with the muffles and the 15 plasma generators (the rest of the pulverized coal ducts being closed by the gates) and fLIing of the pulverized coal flare is performed. In 15 minutes after the flare starts to burn, stable bu~ing of the flare is observed after switching off the plasma generators.
Then, sequential feeding of pulverized coal ~ Lule is performed to the nozzles of burners 2 of the upper and low tiers, which llliX Lu.e is intensively ignited and is burnt 20 in the boiler fire box. In 4 hours after starting said filing, the steam pressure in the boiler has reached 30 - 35 atm.; the temperature of the primaIy steam has been up to 300 - 350 degrees C. After that further filing of the boiler is conducted in accordance with conventional procedures but without switching on the fuel oil jet burners.
The operating parameters sufficient for starting the turbine are reached in 6 hours 25 after the beginning of firing the boiler unit.
The use of the plasma technology for firing a boiler unit in accordance with theproposed method provides the increase in effficiency of the process of firing and stabilizing of low grade coals burning, permits to exclude the consumption of valuable fuel oil, to lower combustible losses (incomplete burning of carbon), to bring down the 30 effluent of harmfill substances into the environment, to improve the safety conditions and to provide wide possibilities for automation of the process of firing and stabilizing of the pulverized coal flare burning in boiler units.

Claims

What is claimed is:

1. A method of firing a boiler unit comprising firing a pulverized coal flare, subsequent sequential feeding of pulverized coal mixture through nozzles of pulverized coal burners installed in the boiler unit in tiers, and firing said mixture, characterized in that the firing of the pulverized coal flare is performed by generating a low - temperature plasma jet by means of a plasma generators provided in muffles of the pulverized coal burners of the low tier, feeding said pulverized coal mixture through the low - temperature plasma jet and igniting thereof, said plasma generators being switched off when the burning of the pulverized coal flare is stabilized and theoperating parameters are reached.

2. A method according to claim 1, characterized in that depending on the type ofa boiler unit, a technology of coal pulverization and fuel characteristics, a number (n) of said pulverized coal burners equipped with the plasma generators and the muffles can be within the range of n = 1 ~ m, wherein m is a number of the burners of the tier.