JPH0768527B2 - Recovery Method of Ammonium Carbonate from Process Drain of Coal Partial Oxidation Furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to carbonization of an ammonia component from a process drain produced in the step of partially oxidizing coal to produce a syngas containing CO, a reducing gas or a fuel gas. It relates to a method of recovering ammonium.

[Prior Art] A partial oxidation method in which coal is burned with oxygen in the presence of steam in a combustion furnace to generate a gas containing CO, CO ₂ and H ₂ has been conventionally known.

The gas containing CO, CO ₂ , and H ₂ generated by this partial oxidation method is used as a synthesis gas, a reducing gas, a fuel gas, or the like.

A conventional method for partially oxidizing coal will be described with reference to FIG.

Coal as a raw material is put into the mill 1 together with water and finely pulverized into a slurry. This slurry is stored in the slurry tank 2 and sent to the combustion furnace (gasification furnace) 10 via the charge pump 3 and the slurry heater 4.

A combustion chamber 5 is formed in the upper part of the combustion furnace 10. The lower part of the combustion furnace 10 is a gas cleaning chamber 6, and the combustion chamber 5 passes through the throat portion 7 to the gas cleaning chamber 6. The gas cleaning chamber 6 is filled with water up to a middle height, and a cylindrical dip tube 8 and a draft tube 9 are coaxially provided so that the lower end is submerged in the water.

Although not shown, a quench ring for supplying water to the upper inner peripheral surface of the dip tube 8 and forming a water film on the inner peripheral surface is provided.

The gas taken out from the gas outlet 11 provided in the combustion furnace 10 is sent to the CO conversion furnace 14 via the scrubber 12 and the heat exchanger 13, and CO is converted into CO ₂ . The gas taken out from the CO conversion furnace 14 is sent to the waste heat boiler 15 via the heat exchanger 13 and is cooled. The drain generated in the boiler 15 is separated by the separator 16, and the drain is supplied to the scrubber 12 via the pump 16a. The gas component from the separator 16 is cooled by the condenser 17, and the drain (primary drain) generated thereby is separated by the separator 18. The gas component from the separator 18 is taken out as a process gas. The primary drain is heated by the heat exchanger 19 and then sent to the heavy coal cheap stripper 20.
It is heated by the steam heater 21 and stripped.
The gas component produced in the stripper 20 is cooled in the condenser 22, and the drain (secondary drain) produced thereby is separated from H ₂ S and CO _{2 in the} separator 23 and returned to the mill 1. The residue of heavy coal cheap stripper 20 is heat exchanger 19, cooler 24, pump
It is supplied to the scrubber 12 via 25.

[Problems to be Solved by the Invention] In the above-described conventional method for partial oxidation of coal, the secondary drain after the heavy coal cheap stripping is returned to the mill 1. Since H ₂ S and NH ₃ are contained in a considerable amount, it has a problem that it affects the slurry forming characteristics of coal and makes it difficult to increase the slurry concentration.

[Means for Solving the Problem] A method for recovering ammonium carbonate from the process drain of a partial oxidation furnace for coal of the present invention includes at least CO, CO ₂ and H ₂ by partially oxidizing coal in a combustion furnace. A step of generating a gas, a step of cooling the gas, a step of separating the generated primary drain, a step of heating the primary drain to strip an easily vaporizable gas component, a step of cooling the stripped gas component, A step of separating the generated secondary drain, and
The subsequent drain is stripped with CO ₂ gas to drive H ₂ S out of the aqueous solution, and the remaining ammonium carbonate is separated and recovered.

[Operation] According to the present invention, ammonium carbonate can be recovered from the secondary drain.

[Embodiment] Embodiment 1 FIG. 1 is a system diagram illustrating an embodiment method.

In this embodiment, the secondary drain from the separator 23 is introduced into the H ₂ S stripper 26 including a tray tower and a packed tower, and stripped by CO ₂ blown from the blowing line 27. In this embodiment, the steam heater 28 heats the drain to promote stripping.

The gas generated by stripping is cooled by the condenser 29 and then introduced into the separator 30. The drain separated by the separator 30 is returned to the stripper 26 as a reflux, and H ₂ S and CO ₂ are taken out and sent to the sulfur recovery step.

The drain (third drain) which is the stripping residue of the stripper 26 is almost pure ammonium carbonate water, which is cooled by the condenser 31, purified by the final purifier 32, and then stored in the tank 33.

The other steps are the same as in FIG.

Next, specific examples will be described.

Under the following conditions, the coal was partially oxidized according to the process shown in FIG. 1 to recover ammonium carbonate.

Coal feed amount 62500kg / h Water feed amount 38300kg / h Oxygen feed amount 39000Nm ³ / h Extraction from separator Primary drain amount 23600kg / h Extraction from separator process gas amount 160000Nm ³ / h Extraction from separator NH ³ amount 143kg / h h Primary H ₂ S content from separator 28 kg / h Primary CO ₂ content from separator 509 kg / h Secondary H ₂ S content 28 kg / h Secondary CO ₂ content from separator 218 kg / h h NH ₃ content in tertiary drain 143 kg / h CO ₂ content in tertiary drain 145 kg / h The elemental analysis results of coal are as follows.

C 67.9wt% H 5.3wt% N 1.0wt% S 4.9wt% Ash 14.8wt% Others 6.1wt% In the above, recovery of ammonium carbonate in the process drain caused by partial oxidation of coal was described. Similar results are obtained for hydrocarbon-based partial oxidation.

Example 2 Stripping was carried out in the same manner as in Example 1 except that the operating conditions of the H ₂ S stripper 26 were changed to those shown in Table 1, and the results are shown in Table 1.

The following is clear from Table 1.

That is, most of H ₂ S can be removed by stripping with N ₂ gas (No. 2, No. 5), but NH ₃ also escapes to the top of the column at the same time, and NH ₃ is efficiently removed. It cannot be collected well.

On the other hand, by blowing CO ₂ and stripping with CO ₂ (No. 3, No. 4), the H ₂ S removal rate can be maintained high and the NH ₃ recovery rate can be increased. Above all, by lowering the tower top temperature while making the stripper bottom temperature sufficiently high (No. 4), it is possible to remove H ₂ S by 97% or more and also recover ammonia by 97% or more. be able to.

This is due to the following reasons. That is, when the CO ₂ gas blown from the stripper bottoms, CO ₂ gas is NH ₃ and tied with ammonium carbonate (NH ₄₎ to form a ₂ CO _3. As a result, NH ₃ is prevented from being emitted as a gas from the top of the column, and is recovered with high recovery efficiency. On the other hand, with N ₂ gas, since there is no such action, NH ₃ is diffused from the top of the column in a gaseous state and cannot be efficiently recovered.

[Effect] As described above, according to the method of the present invention, ammonia by-produced in the partial oxidation step of coal can be recovered as ammonium carbonate. Further, since the drain is not returned to the mill, the slurry forming property in the mill is improved.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example method, and FIG. 2 is a system diagram showing a conventional method. 10 …… Combustion furnace (gasification furnace), 20 …… Heavy coal cheap stripper, 26 …… H ₂ S stripper.

Front page continuation (72) Inventor ▲ Yoshi ▼ Takeshi Taguchi 2575 Fujimagari, Ube-shi, Yamaguchi Ube Ammonia Industry Co., Ltd. (56) References JP-A-57-14693 (JP, A) JP-A-52- 148962 (JP, A)

Claims (1)

[Claims] 1. A step of partially oxidizing coal in a combustion furnace to generate a gas containing at least CO, CO ₂ and H ₂ ; a step of cooling this gas and separating the generated primary drain; The step of heating the secondary drain to strip the easily vaporizable gas component, the step of cooling the stripped gas component and separating the secondary drain generated, and stripping the secondary drain with CO ₂ gas A method of recovering ammonium carbonate from the process drain of a coal partial oxidation furnace, which comprises the step of expelling H ₂ S from the aqueous solution and separating and recovering ammonium carbonate.