Coke oven construction, oven baking and start-up (5)

Section 4 Coke oven start-up

1. Preparation for start-up

1 Hot engineering and equipment trial operation

When the oven temperature reaches 500~600℃, hot engineering and equipment trial operation are required to prepare for the start-up. Since the masonry continues to expand during the oven baking process, all engineering projects that affect the expansion of the oven body should be carried out in the later stage of the oven baking. At the same time, before the coke oven starts, some temporary facilities used for the oven baking need to be removed. All these works are collectively referred to as hot engineering.

Most of the projects in the hot engineering should be started after the expansion of the oven body is basically completed, that is, after the oven temperature reaches 650℃, and completed before the start of work. Therefore, the time is short, the task is in the middle, and it has an important impact on the quality of the coke oven, so it should be properly arranged to ensure timely completion.

There are more than 30 or 40 hot engineering projects, mainly including: the riser base, the receiving interface between the bridge pipe and the riser, the adjustment and sealing of the exhaust gas disc seat and the two forks, the installation and adjustment of the coal loading car grinding wire rack; the adjustment of the coal loading car and the coke pulling car track and the connection with the operating tables at both ends; the removal of temporary facilities for the oven, the grouting of the protection plate (or furnace door frame) and the sealing of the furnace shoulder seam; the burial of the horizontal tie bar, etc. Here we only put forward the following points to draw attention:

1) The proportion of mortar used for sealing the main parts cannot be ignored, and the quality must be guaranteed.

2) The quality of the grouting of the protection plate (or furnace door frame) has a direct impact on the furnace head sealing. If the grouting quality is not good, the coke oven will cause smoke and fire after it is put into production, and even burn the furnace column and damage the furnace body.

3) When the upper horizontal rod is exposed to the outside during the oven drying, the temperature is relatively low. When the rod is buried by the insulation material, the temperature will rise rapidly and expand, causing the spring load to drop sharply, resulting in the free expansion of the furnace body. Therefore, the rod should be buried in sections and coordinated with the iron parts management. The rod nut should be tightened in time to ensure the spring load.

4) The gas collecting pipe and the riser should generally be installed in a hot state. When they are installed in a cold state due to the tight construction period, care should be taken not to affect the oven operation and the reasonable expansion of the furnace body.

In order to ensure the smooth start of the coke oven, it is also necessary to carefully carry out the trial operation of various pipelines, machinery, vehicles and other equipment. The defects and problems of each equipment should be eliminated before the start of work.

The equipment trial operation of the coking workshop includes: gas collection system, exchange transmission system and four major vehicles. The trial operation of each part should be carried out according to the plan and operating procedures.

At the same time as the trial operation of the coking workshop equipment, other workshops and sections related to the commissioning, including blast condensation, circulation sleeping, coal loading and coke screening systems, must also be in qualified operation.

2 Start-up plan and start-up scheme

After the oven temperature reaches above 900℃ and the equipment related to the coke oven passes the trial operation, the coke oven has the necessary conditions for start-up and production.

The start-up process of the coke oven includes: removing the sealing wall, loading coal and extracting the raw gas, changing to normal heating, and adjusting the furnace temperature. It is very complicated and important. If it is not considered carefully, it will cause difficulties in starting the work, especially when the solid fuel oven is baked, the furnace body will be damaged due to excessive heat loss, and even forced to start the work again. Therefore, all aspects of preparation must be made before starting the work, including human and material preparations. Determine the start-up plan and formulate a detailed start-up plan.

The main considerations for formulating the start-up plan are:

1) The equipment with the shortest gas flow distance and the least gas flow, so that the coke oven gas can be returned to the furnace for heating as quickly as possible.

2) The order of removing the sealing wall should ensure that each combustion chamber does not stop heating completely, so as to prevent the furnace temperature from dropping sharply after coal loading and damaging the furnace body.

3) The order of coal loading should consider the transition to the production sequence.

2. Start-up operation

The order of start-up operation is divided into two categories according to the different fuels used in the furnace. The start-up procedure for solid fuel and liquid fuel furnace is: remove the sealing wall - load coal - change to normal heating - adjust furnace temperature.

For gas fuel furnace, due to the availability of external gas fuel, the start-up procedure can be changed to: switch to normal heating - remove the sealing wall - load coal - adjust furnace temperature.

Now, we will take the first type of start-up procedure as an example to discuss several issues in the start-up:

(1) Remove the sealing wall When solid fuel or liquid fuel furnace is used, the sealing wall of the carbonization chamber, the furnace stove and the fire bed of the whole furnace need to be removed in two batches. The first batch is removed before loading coal and changing to normal heating, and the second batch is removed after changing to normal heating. The principle of determining the furnace number of the first batch of wall removal, in addition to the aforementioned that each combustion chamber cannot completely stop heating, should also take into account the problems of uniform heat load of the coke oven when loading coal, more coal loading furnace chambers and faster gas discharge. Generally, it can be carried out in a 9-3 or 6-2 series sequence, and there is also a 9-2 series sequence. When removing the sealing wall, we should concentrate our efforts to buy time, minimize the drop in furnace temperature, and pay attention not to damage the furnace wall.

(2) Coal loading and raw gas extraction The furnace temperature during coal loading and the amount of heat loss during the coal loading process are the key to the success of the coke oven operation. This is especially important for solid or liquid fuel ovens. Therefore, before loading coal, we must try to raise the furnace temperature and strive to reach about 900℃ before starting. During the coal loading process, we must also strengthen the management of small stoves to minimize the drop in furnace temperature.

The day before coal loading, spray the upper pipe with water preheated to 60~80℃. Two hours before coal loading, steam is passed through the gas collecting pipe and the air intake pipe to drive out the air. Usually, after loading a number of coal, the gas collecting pipe is connected from both ends to the center to drive out the steam in the gas collecting pipe and fill it with raw gas. When the pressure of the gas collecting pipe reaches a certain value (it should reach above 98.1Pa for 58-type coke ovens and 49~68.7Pa for 66-type coke ovens), gas is sent to the air intake pipe. After loading the second number of coal, take a gas sample at the end of the suction pipe for three explosion tests. When the gas fills the gas equipment and pipelines in front of the blower, a corresponding explosion test is also performed. After the explosion test is qualified, the blower and the gas pipeline behind the machine are purged of air with steam, and then the blower is started.

The coal loaded at the start of operation is required to have a large volatile matter, large shrinkage and low moisture content, so that it can produce more gas and push coke smoothly. Each carbonization chamber should be basically filled and leveled.

(3) The coke oven is changed to normal heating, that is, the coke oven is changed from the oven baking state to the heating state during normal production. Therefore, after the blower is started, it should be quickly changed to normal heating to avoid excessive furnace temperature drop, which will affect the smooth commissioning of the coke oven. At the start of operation, the coke oven gas returns to the furnace through the circulation pipe after the blower to simplify the process. Before the gas returns to the furnace, according to the direction of the gas, the head Wang passes steam to drive out the air, and then uses the returned gas to drive out the steam. When gas comes out of the discharge pipe at the end of the main pipe, turn off the steam and conduct an explosion test. After passing the test and when the pressure of the gas main pipe reaches the specified value, gas can be delivered to the furnace in groups. When delivering gas, air should be delivered first and then gas, and the fire situation should be checked at the fire hole on the top of the furnace while delivering. After delivering one group, the next group can be delivered after the combustion is normal, so that there is enough time to deal with it in time if a problem occurs. When the gas pressure is insufficient, the heating of the coal-loading furnace chamber should be ensured first. If the gas pressure is lower than the safety pressure (the pressure of the main pipe of the 58-type coke oven is 294Pa, and it can be appropriately lower for small and medium-sized coke ovens), the gas supply should be stopped immediately to prevent backfire and explosion, and the gas supply should be resumed after the pressure rises.