summary
The XXXXXX t/h circulating fluidized bed boiler produced using XXXX was shut down due to national policies. In the past two years, the National Development and Reform Commission has issued new policies to encourage the use of renewable energy instead of coal resources. In order to comprehensively utilize resources, reduce production costs and reduce harmful gas emissions from boilers, XXXXX commissioned JiNan jiaoyuan boiler Co., Ltd. to transform the plant's 35t/h circulating fluidized bed boiler into a circulating fluidized bed boiler with 100 % biomass. This would allow for the full use of existing investment resources and would allow for the use of new combustion technologies for the operation of closed boilers, using national policies. It has great social and economic benefits.
This transformation is specially designed for XXXXXX.
一、 Technical requirements for adaptation
1. Boiler parameters
Nominated evaporation XXX T / H
Valued steam pressure 3.82 MPa
Rated steam temperature 450 °C
Water supply temperature 105 °C
Cold wind temperature 20 °C
2. Design fuel: crop palm-shell(fuel low calorific Qydw = 12600-1638KJ/kg).
Incoming sizes of biofuels ≤ 100 mm
Technical and Economic Indicators of the Reformed Boiler
Nominated evaporation XX T / H(left and right)
Rated superheated steam pressure 3.82 MPa
Rated steam temperature 450 °C
Exhaust temperature 150 °C
Design fuel QDyW = 12600-16380 KJ/kg
Water requirements ≤ 20 %
Boiler thermal efficiency(design fuel) 80 %
Smoke Emission Lingeman(Level 1)
Boiler initial discharge concentration 15g/Nm3
Filling size requirements for fuel ≤ 100 mm
二、 Instructions for the overall system layout of boilers
1. The boiler has a burning heat value of 12600-16380 KJ/kg, water ≤ 20 %, and fuel intake size ≤ 100 mm farming. It adopts a circulating fluidized bed structure with a low circulation rate and an appropriate bed surface area.
2. Special design is made for the membrane water wall at the feed port.
3. The inertial separator and high temperature cyclone separator of the boiler are not adjusted in structure.
4. Restricted by the civil beam of the rotating layer, to facilitate ignition and operation, ensure higher
The combustion efficiency of the combustion chamber is arranged in the lower part of the rotating layer.
5. In order to ensure that the larger fuel quantity is reliably fed into the furnace, a spiral feed machine that has been proved by practical operation experience and is truly adapted to biofuels has been arranged.
6. The cloth wind board is a water-cooled structure type, and the wind room is a water-cooled air room.
7. In order to ensure the long-term continuous operation of the boiler, the combustion chamber combustion belt, the insulation layer of the wind board, the cyclone separator and the refuel furnace wall all use special materials for high temperature resistance, wear-resistant refractory concrete and refractory bricks.
8. In order to adapt to the transport characteristics of biomass fuels and the combustion characteristics of circulating fluidized beds, the following systems and equipment need to be added:
(1) Material warehouse in the factory. The size of the material warehouse is determined by the available area and material storage time(such as one month or three months) in the power plant.
(2) Transmission belts. Including the materials warehouse in the factory and from the materials warehouse in the factory to the pre-furnace warehouse.
(3) Furnace material warehouse(including bottom transmission equipment). The main role is to serve as a buffer for boiler combustion, the buffer of one hour is.
(4) Pre-furnace feed machine. This equipment relates to the safe and stable operation of the boiler. A specially designed screw feeding machine has been used which has been proved by the practice of many boilers.
(5) Gaza warehouse(inert material) and its conveyer. In order to enable the circulating fluidized bed boiler to burn 100 % biomass fuel. A set of inert material systems must be added to ensure normal material circulation.
三、Introduction to Part of Boiler Reform Structure
1. Boiler.
According to the need for transformation, the pot is raised by 1.5 M, and the other structures have not been changed.
2. Water cooling system
The feed port is structurally treated. Part of the drop pipe needs to be redesigned and replaced. The combustion chamber part needs to be redesigned, mainly changes in the furnace area, secondary air outlet, and Gaza mouth. The water cooling wall around the furnace is a membrane wall structure. The new arrangement of the front, rear, left, and right water cooling collection box, and the combustion chamber water cold wall is welded with dense pins to fix the refractory material.
The furnace is divided into four water circulation circuits: left, right, front and back. The cross-sectional ratio is within the scope of the design specification. The container in each loop is fitted with a discharge valve for regular discharge.
3. superheater
The superheater tube system is modified, which is mainly to increase the superheated area and increase the superheated screen in the furnace. Add a sprinkler.
4. A thermostat
The original structure has not been changed.
5. Evaporator
In order to adapt to the combustion characteristics of biomass boilers, to ensure the operation load, reduce the exhaust temperature, add a group of evaporators before the coal economizer.
6. Coal economizer
The coal economizer's container is not moving, and the tube bundles are changed to square fin tubes. The spacing of the tubes arranged makes the smoke speed at this place reach a suitable range, reduces the wear of the coal economizer, reduces the formation of ash accumulation, and ensures the boiler operation. Reliability. The water supply flows from bottom to bottom along the serpentine tube and the flue gas flows in reverse.
7. Air preheater
The final stage of the air preheater was modified to avoid corrosion at low temperature with the use of Calden Steel.
1. Combustion system
The combustion system consists of a furnace, a cyclone separator and a refuel. The lower part of the furnace is a dense phase material layer. The wind cover is evenly arranged on the wind board, and the wind is evenly entered into the combustion chamber from the wind cap.
Biomass fuel of the design size is fed into the combustion chamber by a rotary feed machine in front of the furnace. Loading wind is arranged at the coal inlet.
The secondary wind is arranged on the front and rear walls of the furnace. Secondary winds account for about 30 % of the total air volume to facilitate the combustion of suspended fuel.
The burning flue gas passes through the screen superheater, the high temperature superheater, the low temperature superheater, and enters the inertial chamber and the cyclone separator. The separated fine particle material is returned to the furnace for recycling and combustion by the inertial chamber recharging device and the feeding leg recharging device. The flue gas leaving the cyclone separator is discharged into the atmosphere through the evaporator, coal economizer, air preheater, bag dust collector, fan, and chimney..
The burned ash is discharged from the two slag discharge pipes on the cloth wind board. When the boiler needs to start and run adjustment, the fly ash material in the refuel is discharged from the ash discharge pipe in the refuel.
The accumulated ash should be discharged regularly after a long period of operation in the pressure room under the cloth wind board.
The furnace adopts artificial ignition on the bed.
9. Architecture and platform escalators
The furnace structure is all steel structures. The steel frame has been adjusted according to needs. Some beams and columns need to be added to the furnace front warehouse and Gaza warehouse. And ... New platform escalators are arranged around the combustion chamber to facilitate ignition and overhaul.
10. Furnace Wall
The original furnace wall was reconstructed, and the furnace part was a light furnace wall. The modified furnace wall considers the expansion after the furnace wall is heated, and a reasonable expansion seam is arranged to ensure the sealing of the furnace wall.
10. Pipeline layout within boiler range
According to the increased overheated surface and the evaporative heated surface, the pipeline is partially adjusted. The new sprinkler dampers and surface dampers are adjusted according to their position to facilitate the layout of other components and the sewage pipes are installed in the new structure.
11 Safety accessories for boilers
The application of the original structure remains unchanged.
四、 the basis of transformation design
1. According to the rich technical experience of biomass boiler and circulating fluidized bed combustion. There are nearly 2000 circulating fluidized bed boilers and nearly 30 biomass boilers operating successfully.
2. The calculation of boiler heat is based on the former Soviet Union's "Standard Method for Thermal Calculation of Boiler Units."
3. The strength calculation is based on GB/T9222-2008 "Calculation of the strength of pressurized components of water pipe boilers."
4. The calculation of smoke resistance is based on the former Soviet Union's "Standard Method for Aerodynamic Calculation of Boiler Equipment."
5. Design, manufacture and installation of steam boilers according to the Ministry of Labor and Personnel "Safety Technical Supervision Regulations."
6. Other relevant national technical standards.
