CN113028389A

CN113028389A - Low-nitrogen gas boiler and low-nitrogen combustion method thereof

Info

Publication number: CN113028389A
Application number: CN201911250017.1A
Authority: CN
Inventors: 李为臻; 张景才; 张涛
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2019-12-09
Filing date: 2019-12-09
Publication date: 2021-06-25

Abstract

The invention discloses a low-nitrogen gas boiler and a low-nitrogen combustion method thereof. The gas boiler comprises a gas mixing system, a combustion system, a heat exchange system, a monitoring system and an electric control system, wherein the combustion system comprises a flame burner and a catalytic burner, the catalytic burner is combined with the heat exchange system, the flame burner is used for heating the catalytic burner to a working temperature by heat generated by initial flame combustion, the catalytic burner is used for catalyzing low-nitrogen combustion, the heat exchange system removes partial heat generated when the catalytic burner normally works, the catalytic burner is guaranteed to be completely combusted in a proper temperature interval, and the generation of nitrogen oxides is effectively controlled. All the systems work cooperatively, so that the normal work of the gas-fired boiler is realized, the fuel utilization rate and the heat exchange efficiency are improved, the concentration of nitrogen oxides in tail gas is obviously reduced, and the standard of direct emission of the tail gas can be reached.

Description

Low-nitrogen gas boiler and low-nitrogen combustion method thereof

Technical Field

The invention relates to the technical field of gas-fired boilers, in particular to a low-nitrogen combustion gas-fired boiler and a low-nitrogen combustion method thereof.

Background

The nitrogen oxide is an important precursor formed by PM2.5 in haze, and the concentration of the nitrogen oxide allowed by the national environmental protection standard to the emission of the nitrogen oxide in the combustion tail gas of the gas boiler is lower and lower. The nitrogen oxide control of the tail gas of the gas boiler mainly has two modes: firstly, the combustion technology is improved, so that nitrogen oxides are generated as little as possible in the combustion process to meet the requirement of emission limit; secondly, the combustion tail gas is post-treated, and the concentration of the nitrogen oxide is reduced to the emission limit value by the catalytic selective reduction technology and equipment.

Most of traditional gas boiler burners adopt a diffusion flame combustion mode, and have the problems of incomplete fuel combustion, low fuel utilization rate, low heat efficiency, high NOx and CO emission concentration and the like. The low-nitrogen flame combustion technology developed at present mainly comprises an air staged combustion technology, a fuel staged combustion technology, a flue gas recirculation technology, a lean-burn premixed combustion technology, a full-premixed surface combustion technology and the like. The effect of reducing nitrogen oxides by full-premixing surface combustion is the best, but the problems of high operation and maintenance cost, high safety risk and the like exist.

Compared with flame combustion, flameless combustion can enable combustion to be carried out more uniformly and stably, local high temperature is avoided, and generation of nitrogen oxides is reduced. Flameless combustion includes both high temperature air combustion and catalytic combustion. High temperature air combustion utilizes high temperature air to heat the fuel gas above the auto-ignition temperature, thereby enabling flameless combustion to occur in a relatively wide area, avoiding local high temperatures and effectively reducing NOx emissions. The catalytic combustion is a complete oxidation reaction of fuel mixed gas on the surface of a catalyst, and the reaction site can be regulated according to the shape of the catalyst, so that the catalytic combustion has the advantages of high combustion efficiency, low combustion temperature, stable and controllable combustion process and the like.

In the catalytic combustion technology currently used in devices such as gas-fired boilers, for example, japanese patent No. JP09254970, entitled combined power generation device, a catalytic combustion device is provided in a boiler body of a boiler to realize catalytic combustion; KR1020010058836A, entitled catalytic burner for gas boiler, the combustion unit realizes gas phase combustion reaction and catalytic chemical reaction by metal fiber and catalyst on the carrier; the water heater is characterized in that a preheating burner and a catalytic burner are arranged in a shell of the water heater, wherein the preheating burner and the catalytic burner are provided with the Chinese patent number of 201711005587.5 named as a gas water heater and the Chinese patent number of 201711018017.X named as a gas water heater.

Above-mentioned boiler or water heater that adopts catalytic flameless combustion technology heating, its combustor and heat transfer system exist independently or partly combine, and the overheat protection to catalytic combustor is not enough, influences life.

Disclosure of Invention

In order to solve the problems of low-nitrogen combustion of the gas-fired boiler, the invention provides a low-nitrogen gas-fired boiler.

The technical scheme adopted by the invention for realizing the purpose is as follows:

the utility model provides a low nitrogen gas boiler, includes air intake system, combustion system, heat transfer system, monitoring system and electrical system, its characterized in that: the air inlet system comprises a fan 2, a gas proportional valve 3 and a gas nozzle 6, the combustion system comprises an ignition needle 7, a flame burner 8 and a catalytic burner 9, and the heat exchange system comprises a catalytic burner cooling mechanism 13 and a waste heat exchanger 15; the flame burner is arranged at the bottom of the low-nitrogen gas boiler body 12 and is connected with the gas inlet system in a sealing way; the burner cooling mechanism 13 is arranged on the inner wall of the furnace body 12 and the center of the furnace body; the catalytic combustor 9 is fixedly arranged on the cooling mechanism 13; the waste heat exchanger 15 is arranged at the upper part inside the furnace body 12, and the smoke collecting hood 18 and the flue 19 are arranged at the top part of the furnace body 12.

The flame burner 8 is a monolithic porous medium such as a foam or honeycomb structure of porous metal or porous ceramic.

The catalytic combustor 9 is a catalyst supported by a porous foam structure ceramic material.

The catalytic combustor cooling mechanism 13 in the heat exchange system is a metal pipe fitting or a metal jacket type structure which is communicated with the inside, the cooling mechanism 13 and the waste heat exchanger 15 are connected through a metal pipe fitting which allows water flow to circulate, one end of the cooling mechanism 13 is provided with a cooling water interface 16, and one end of the waste heat exchanger 15 is provided with another cooling water interface 17.

The low-nitrogen combustion method of the low-nitrogen gas boiler comprises the steps of starting the fan 2 for blowing before, then starting the ignition needle, then introducing mixed gas of gas and air, igniting the mixed gas after the mixed gas passes through the flame burner 8, closing the ignition needle after the high-temperature gas after combustion heats the catalytic burner 9 to 650 ℃, reducing the gas inflow of the gas to extinguish flame, and then adding the gas to ensure that the mixed gas of the gas and the air is completely combusted with low nitrogen on the catalytic burner 9.

Drawings

Fig. 1 is a schematic structural view of a low-nitrogen gas boiler according to the present invention.

In the figure: 1. the device comprises an electric control system, 2, a fan, 3, a gas valve, 4, a gas inlet, 5, an air inlet, 6, a gas nozzle, 7, an ignition needle, 8, a flame burner, 9, a catalytic burner, 10, a flame sensing needle, 11, a temperature probe, 12, a furnace body, 13, a cooling mechanism, 14, a combustion cavity, 15, a waste heat exchanger, 16, a cooling water inlet, 17, a cooling water outlet, 18, a smoke collecting hood, 19 and a flue.

Detailed Description

The following describes the embodiments and operation of the present invention with reference to the accompanying drawings.

The terms of orientation such as up, down, left, right, front, and rear in the present specification are established based on the positional relationship shown in the drawings. The corresponding positional relationship may also vary depending on the drawings, and therefore, should not be construed as limiting the scope of protection.

As shown in fig. 1, a low-nitrogen gas boiler comprises an air inlet system, a combustion system, a heat exchange system, a monitoring system and an electric control system. The air inlet system and the electric control system 1 are arranged below the cylindrical furnace body 12, the air inlet system comprises a fan 2, a gas valve 3 and a gas nozzle 6, a gas inlet 4 is connected with the gas valve 3, and an air inlet of the fan 2 is 5; the combustion system, the heat exchange system and the monitoring system are arranged in the furnace body 12, the combustion system comprises an ignition needle 7, a flame burner 8 and a catalytic burner 9, the heat exchange system comprises a catalytic burner cooling mechanism 13 and a waste heat exchanger 15, the detection system comprises a flame sensing needle 10 and a temperature probe 11, the flame sensing needle 10 is deeply arranged in a combustion cavity 14, the temperature probe 11 is arranged in the catalytic burner 9, the flame burner 8 is made of integral honeycomb ceramics and is arranged at the bottom of the furnace body 12 and is hermetically connected with an air inlet system, the ignition needle 7 is arranged at the upper part of the flame burner 8, the burner cooling mechanism 13 is spirally surrounded by metal pipe fittings and is arranged on the inner wall of the furnace body 12 and the center of the furnace body, the cooling mechanism 13 at the center of the furnace body is a cylinder with taper spirally surrounded by the metal pipe fittings, and the metal pipe is connected through a mosquito-repellent incense circular structure with a gap on the plane connected with the inner, the cooling mechanism 13 is enclosed into a combustion chamber 14 with a gap at the upper part, the catalytic combustor 9 is a catalyst loaded by porous foam structure ceramic material and is fixedly arranged on the inner surface of the cooling mechanism 13, the waste heat exchanger 15 is a fin type heat exchanger and is arranged at the upper part inside the furnace body 12, the bottom of the cooling mechanism 13 is provided with a cooling water inlet 16, the tail end of the waste heat exchanger 15 is provided with a cooling water outlet 17, the waste heat exchanger 15 and the smoke collecting hood 18 are provided with a gap, and the smoke collecting hood 18 is provided with a flue 19.

The low-nitrogen combustion process is that after the fan 2 is started to perform pre-purging, the ignition needle 7 is started, then the electric control system 1 controls the gas valve 3 and the fan 2 to introduce mixed gas of gas and air with proper proportion, the mixed gas is ignited by the ignition needle 7 after passing through the flame burner 8, after the high-temperature gas after combustion heats the catalytic burner 9 to above 650 ℃, the ignition needle is closed, a flame signal and a temperature signal are respectively monitored by the flame sensing needle 10 and the temperature probe 11 of the monitoring system and fed back to the electric control system 1, the gas valve 3 is adjusted to reduce the gas air input to extinguish the flame, then the gas is increased, and the mixed gas of the gas and the air is subjected to low-nitrogen complete combustion on the catalytic burner 9. The high-temperature gas after burning passes through the gap between the catalytic burner 9 at the upper part and the cooling mechanism 13, exchanges heat through the preheating heat exchanger 15, is collected through the smoke collecting hood 18 and is exhausted from the flue 19.

Claims

1. The utility model provides a low nitrogen gas boiler, includes boiler furnace body (12), air intake system, combustion system, heat transfer system, its characterized in that: the air inlet system comprises a fan (2), a gas proportional valve (3) and a gas nozzle (6), the combustion system comprises an ignition needle (7), a flame burner (8) and a catalytic burner (9), and the heat exchange system comprises a catalytic burner cooling mechanism (13) and a waste heat exchanger (15);

the bottom of the boiler body (12) is provided with a gas inlet for gas, oxygen and/or air, and the top is provided with a flue (19);

the catalytic combustor (9) is arranged on the wall surface of the cooling mechanism (13) in the furnace body (12) and forms a combustion cavity with the flame combustor (8) in a surrounding way, and the catalytic combustor (9) is a catalytic combustion catalyst loaded by an integral porous material;

a porous flame burner (8) is arranged at the air inlet of the furnace body; an air outlet of the fan (2) is communicated with an air inlet of the furnace body through a pipeline, a gas nozzle (6) is arranged below the air inlet of the furnace body, and a gas proportional valve (3) is arranged between the gas nozzle (6) and a gas source; the gas flowing out from the air outlet of the gas and fan (2) enters the catalytic combustor (9) through the flame combustor (8) to be combusted; an ignition needle (7) is arranged above the feed inlet of the flame burner (8);

a waste heat exchanger (15) is arranged in the furnace body (12) above the catalytic combustor (9).

2. The low-nitrogen gas boiler according to claim 1, wherein:

the flame burner is arranged at the bottom of the low-nitrogen gas boiler body (12), and the peripheral edge of the flame burner is hermetically connected with the inner wall surface of the air inlet.

3. The low-nitrogen gas boiler according to claim 1, wherein:

the burner cooling mechanism (13) is arranged on the inner wall surface of the furnace body (12) and the outside of the furnace body central catalytic burner (9): the cooling mechanism (13) of the catalytic combustor in the heat exchange system is of a metal pipe fitting or metal jacket type structure which is internally communicated, a chamber with a gas through hole is surrounded by the metal pipe fitting or the metal jacket type structure, the inner wall surface of the chamber is attached to the outer wall surface of the wall of the catalytic combustor (9), and the lower part of the chamber is provided with an opening communicated with the gas inlet of the catalytic combustor (9);

the catalytic burner (9) is fixedly arranged on the cooling mechanism (13).

4. The low-nitrogen gas boiler according to claim 1, wherein:

a smoke collecting hood (18) is arranged at the top in the furnace body (12), a smoke outlet communicated with a flue (19) is arranged above the smoke collecting hood (18), and an opening below the smoke collecting hood (18) is communicated with the interior of the furnace body (12);

the waste heat exchanger (15) is arranged at the upper part inside the furnace body (12) and below the smoke collecting hood (18).

5. The low-nitrogen gas boiler according to claim 1, wherein: the flame burner (8) is a monolithic porous medium, such as a foam or a honeycomb structure of porous metal or porous ceramic, which is a block or plate.

6. A low-nitrogen gas boiler in accordance with claim 1, wherein: the catalytic combustor (9) is a supported catalyst of a porous ceramic material with a foam structure and loaded with active components, the active components of metal oxides are one or more than two of aluminum oxide, cerium oxide, magnesium oxide, lanthanum oxide, titanium oxide, iron oxide, manganese oxide, silicon oxide, sodium oxide, copper oxide, nickel oxide, platinum oxide, rhodium oxide, silver oxide and the like, and the mass fraction of the active components of the metal oxides can be 0.5-15%.

7. The low-nitrogen gas boiler according to claim 1, wherein: the catalytic combustor cooling mechanism (13) in the heat exchange system is a metal pipe fitting or a metal jacket type structure which is internally communicated, one end (16) of the catalytic combustor cooling mechanism is communicated with a cooling liquid outside the furnace body (12), and the other end of the catalytic combustor cooling mechanism is connected with a waste heat exchanger (15); forming a tubular heat exchanger or a metal jacketed heat exchanger with a through hole on the wall surface;

the waste heat exchanger (15) is a tubular heat exchanger, one end of the waste heat exchanger is connected with the cooling mechanism (13), and the other end (17) of the waste heat exchanger is communicated with a heat exchange medium outside the furnace body (12).

8. The low-nitrogen gas boiler according to claim 1, wherein: the cooling liquid and the heat exchange medium are water or heat conducting oil and other liquid;

the cooling mechanism (13) and the waste heat exchanger (15) are connected through metal pipes allowing the cooling liquid and the heat exchange medium to flow.

9. The low-nitrogen gas boiler according to claim 1, wherein:

the system also comprises a monitoring system and an electric control system; the monitoring system comprises a flame induction needle (10) arranged inside the catalytic combustor (9), a temperature sensor or a temperature probe (11);

the electric control system comprises a computer or a singlechip, and the computer or the singlechip is connected with the flame induction needle (10) and the temperature sensor or the temperature probe (11);

the air output and the on-off of the fan (2) are controlled by a computer or a single chip microcomputer, and the opening degree of the fuel gas proportional valve (3) is controlled by the computer or the single chip microcomputer; the medium flow of the cooling mechanism (13) and/or the waste heat exchanger (15) is controlled by a computer or a singlechip relay.

10. A low-nitrogen combustion method of a low-nitrogen gas boiler according to claims 1 to 9, characterized in that: after the fan (2) is started for front blowing, the ignition needle is started again, then the mixed gas of the fuel gas and the air is introduced, the mixed gas is ignited after passing through the flame burner (8), the burnt high-temperature gas heats the catalytic burner (9) to a temperature higher than 650 ℃, the ignition needle is closed, the gas inflow is reduced, the flame is extinguished, then the fuel gas is added, and the mixed gas of the fuel gas and the air is subjected to low-nitrogen complete combustion on the catalytic burner (9).