JPS5824363B2 - Preheating and waste heat recovery method for sulfuric acid production equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a multi-stage contact, two-stage absorption type sulfuric acid production equipment using sulfur combustion.
The present invention relates to a preheating and waste heat recovery method that can raise the temperature of a waste heat boiler and a coal saver, and can compensate for a decrease in the amount of waste heat recovered during low load operation of the device.

Conventionally, the temperature of a converter or the like by sulfur combustion has been increased by utilizing the heat stored in the sulfur combustion furnace by burning auxiliary fuel in an auxiliary fuel burner installed in the sulfur combustion furnace, and by directly heating the combustion gas.

This method takes time to heat up to the temperature required for start-up, and the water vapor inevitably contained in the combustion gases produces sulfuric acid, damaging the vanadium pentoxide catalyst and equipment in the converter. Shorten your lifespan.

To solve this problem, the temperature of the converter etc. can be raised using clean Iyn heated dry air, but this requires the installation of a dry air heating device that is not normally used.

Of the heat of combustion of sulfur and heat of combustion of sulfur dioxide in a sulfur/combustion catalytic sulfuric acid production equipment, the surplus, excluding the amount necessary for sulfuric acid production, is generally recovered as steam in a waste heat boiler; The amount naturally decreases as the load on the equipment decreases.

When using sulfuric acid production equipment as a steam source for other equipment, for example, when using it as a steam source for phosphoric acid production equipment or power generation equipment, it is necessary to generate steam with little fluctuation, but due to storage equipment etc. When sulfuric acid production is curtailed, the lack of steam must be supplemented from other steam sources.

The present invention is intended to obtain the required amount of steam generation even during low-load operation of a sulfuric acid production apparatus, and at the same time to effectively perform preheating at the start of operation using clean dry air.

The features of the present invention will become clear from the following description with reference to the diagram of FIG.

That is, during low-load operation of the sulfuric acid production equipment, air 2 introduced from the blower 1 is used as auxiliary fuel 4 in the hot air generating furnace 3.
becomes high-temperature combustion gas 2A by combustion, and the heat exchanger 5
, the evaporator 6 and the economizer 7 before being discharged.

A portion 11a of the dry air 11 flowing through the pipe from the main blower 9 to the sulfur combustion furnace 10 through the drying tower 8 is branched,
It enters the heat exchanger 5 through the tube, where it is indirectly heated by the high-temperature combustion gas 2A, and is heated to the temperature necessary for the catalytic reaction from sulfur dioxide to sulfur trioxide. A reactant gas 12 from a reactor (not shown) is supplied to the catalyst bed of the converter 13 through a pipe or a pipe leading to the catalyst bed of the converter 13 into which the reactant gas 12 is to be introduced.

By supplying the heated dry air 11a in this way, the oxygen concentration in the reaction gas 12 will increase, and an improvement in the reaction rate from sulfur dioxide to sulfur trioxide can be expected.

The waste heat of the gas 14 that has exited the catalyst layer is recovered by a normally provided economizer, evaporator (none of which are shown), etc., but by adding the heated dry air 11a, the waste heat is recovered when the load on the device is reduced. This can compensate for the decrease in the amount of waste heat recovered.

A part of the boiler water 16 used in the waste heat boiler 15 is introduced into the evaporator 6 and the economizer 7, and is heat exchanged with the high temperature combustion gas 2A from the heat exchanger 5.

The amount of auxiliary fuel burned can be adjusted according to the load on the device, and the amount of waste heat recovered for the entire device can be kept approximately constant.

At the start of operation, high-temperature dry air 11a from the heat exchanger 5 is supplied through a pipe to the first layer involved in the reaction of the catalyst in the converter 13, and at the same time the temperature of the catalyst is raised to the reaction starting temperature. The reactant gas 12 is introduced into the pipe that supplies the reaction gas 12 from the absorption tower to the converter 13, or into the catalyst layer leading to the pipe, and the temperature of the catalyst is raised.

This operation makes it possible to uniformly raise the temperature of the entire catalyst to the reaction start temperature, which is not possible by simply introducing high-temperature dry air 11a into the first layer of the catalyst, and to increase the amount of harmful sulfur dioxide gas that tends to occur at the start of operation. emissions can be eliminated.

In addition, by heating the boiler water 16 of the evaporator 6 and the economizer T to a predetermined temperature by the high temperature combustion gas 2A from the heat exchanger 5, the device can be brought to a steady operating state in a short time. be able to.

Note that FIG. 1 shows an embodiment of the present invention, and the drying tower 8 and the main blower 9 do not necessarily have to be arranged in this order.

That is, first, there is a main blower 9, and the air from this main blower 9 is dried in the drying tower 8, and the dried air 11 may be supplied to the sulfur combustion furnace 10.

Further, the evaporator 6 and the waste heat boiler 15 may be manufactured as an integrated device with two flow paths on the gas side.

Below, the results of applying the present invention to a 100OT/D sulfur combustion type sulfuric acid production apparatus will be explained.

Here, the capacity of blower 1 is 1000 Nm'/77!17
2.120kW.

The temperature of the combustion gas at the outlet of the hot air generating furnace 3 was set to 650° C. based on the material of the heat exchanger 5.

The evaporator 6 and economizer 7 reduce the exhaust gas temperature to 200℃.
Waste heat was recovered until the temperature reached ℃.

As shown in Figure 2, the amount of steam generated when the device was under low load was able to maintain 80% of the amount when the device was loaded at 40% compared to when it was 100% loaded.

In addition, the consumption of auxiliary fuel has a calorific value of 10,000 Km/k.
The maximum rate was 1800 g of heavy oil/h.

At the start of operation of the equipment, 47°C is required to preheat the catalyst.
Dry air at 0° C. was supplied to the converter 13 at a necessary and sufficient rate of 4700 ONm”/h.

As described above, according to the present invention, it is possible to raise the temperature of the converter to an appropriate temperature using high-temperature dry air during preheating of the sulfuric acid production equipment and when the load is low. Not only can the reaction be promoted by increasing the oxygen concentration in the converter without causing damage, but also the operating rate of the dry air heating device, which was conventionally only used for preheating, can be improved. Since the boiler water of the waste heat boiler is heated with the auxiliary fuel combustion gas after heating the dry air, the required amount of waste heat and steam generation of the boiler can be secured even at low load, and the amount of steam generation can vary based on the load. can be kept to a minimum.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the load of the device and the amount of steam generated in the embodiment. 1...Blower, 2A...High temperature combustion gas, 3...Hot air generator, 5...Heat exchanger, 6...Evaporation Container, 1... Carbon saver, 8.
...Drying tower, 10...Sulfur combustion furnace, il
l...Dry air, 11a...Partly dry air, 12...Reaction gas, 13...Converter, 15...Waste Heat boiler, 16...
Boiler water.

Claims (1)

[Claims] 1 A method for preheating and waste heat recovery at the start of operation in a sulfur-burning multi-stage contact two-stage absorption sulfuric acid production equipment, in which dry air is indirectly heated with auxiliary fuel combustion gas to catalyze sulfur dioxide to sulfur trioxide. The temperature required for the reaction is reached, and this high-temperature dry air is sent to the converter during preheating and during low-load operation to raise the temperature of the converter, and the auxiliary fuel combustion gas after heating the dry air is used to preheat it. A method for preheating and recovering waste heat for a sulfuric acid production equipment, which is characterized by heating boiler water of a waste heat boiler during low-load operation and during low-load operation.