CN1202387A

CN1202387A - Steam purifying method and apparatus for change-over system of synthetic ammonia plant

Info

Publication number: CN1202387A
Application number: CN 98113544
Authority: CN
Inventors: 陈劲松; 王梦飞; 吴大天; 曾建桥
Original assignee: HUBEI RESEARCH INSTITUTE OF CHEMISTRY
Current assignee: Huashuo Technology Co., Ltd.
Priority date: 1998-05-08
Filing date: 1998-05-08
Publication date: 1998-12-23
Anticipated expiration: 2018-05-08
Also published as: CN1057477C

Abstract

Steam after mixing directly with partial transforming gas is first heated to the temperature 10-100 deg above the dew point and then passed through one fixed bed purifier to separate out the solid impurity in overheated steam before entering the transforming catalyst bed. The fixed bed purifier includes one purifier with stuffing, steam inlet, transforming gas inlet and mixed gas outlet; one by-pass line for transforming gas and one temperature regulating valve beside the purifier. There are nitrogen or steam inlet above and outlet below the stuffing layer, and they are used to introduce nitrogen or steam to prevent air from entering transforming furnace during unloading stuffing. The diameter of the purifier is 10-100%, preferably 30-40%, of that of transforming furnace. The present invention makes it possible to omit the salt solution eliminating equipment for steam preparation.

Description

Steam purification method and device for conversion system of synthetic ammonia plant

The invention relates to a method and a device for separating solid impurities in steam by a conversion system of a synthetic ammonia plant.

At present, more than 100 families and small families exist in the whole countryThe ammonia synthesis plant adopts ZL90103262.X 'carbon monoxide low-temperature transformation process', which is called total low-temperature transformation process for short, and the inventor perfects and improves the process on the basis of the patent. The process conversion is carried out in two sections or three sections and four sections, and a cobalt-molybdenum series sulfur-resistant low-temperature high-activity conversion catalyst (ER-4 catalyst developed by chemical research institute in Hubei province) is completely used. Because the steam can cause the reversion, i.e. hydrolysis, of the cobalt-molybdenum sulfur-tolerant shift catalyst, the reversion causes MoS₂Conversion to inactive MoS₂。

In order to prevent the reaction, saturated steam is generally directly added into the middle, namely two or three sections of the shift converter without adding an inlet of the shift converter, which plays an important role in preventing the reversion. However, in use, it was found that a large amount of solid impurities was deposited on the upper part of the catalyst of the shift converter due to poor steam quality. The analyzed impurity components are the same as those of the boiler water and obviously caused by water and fog carried by steam. To solve this problem many plants use desalinated water to produce steam, which increases the investment and equipment.

The invention aims to provide a steam purification method and a steam purification device for a conversion system of a synthetic ammonia plant, which can prevent solid impurities in steam from entering a catalyst bed layer of a conversion furnace.

The steam and part of high-temperature conversion gas are mixed and superheated to above dew point, and then fed into fixed bed steam purifier to make the soluble impurities in the steam and/or mist be separated out, retained and deposited on the filler in the purifier, and the gas is fed into conversion furnace so as to protect catalyst in the conversion furnace.

The temperature of the mixed steam and the converted gas is generally 10-100 ℃ above the dew point, and preferably 30-50 ℃ above the dew point. The gas flow rate is increased due to the fact that the temperature is too high, impurities in the gas cannot be intercepted and deposited, and the resistance of a bed layer is increased; the impurities in the water vapor or fog can not be separated out due to low temperature, and the purification effect is lost.

A device for steam purification of a shift system of a synthetic ammonia plant comprises a fixed bed impurity separation purifier, wherein a filler is arranged in the purifier, a steam inlet is arranged at the upper part of the purifier, a mixed gas outlet is arranged at the lower part of the purifier, a shift gas straight-through auxiliary line and a regulating valve are arranged beside the purifier, a nitrogen or steam inlet and outlet is arranged above and below a filler layer, the diameter of the purifier is 10-100 percent, preferably 30-40 percent of the diameter of a shift converter, and the height of the purifier is 1.0-2.0 times of the diameter. The diameter of the straight-through secondary line is 1/2 times of the main pipeline diameter, and the fixed bed is generally phi 800 and the height is 1.0 meter. The secondary line is used for adjusting the temperature of the mixed gas of the steam and the conversion gas, and the pipe diameter is not suitable to be too large or too small.

The purifier is filled with alumina pellets or rings or waste shift catalyst, the alumina pellets are phi-4 mm.

When the steam purifier is used for purifying steam, solid impurities in the steam can be intercepted and deposited on the filler, and the filler can be detached, sieved and reloaded after the purifier is blocked.

The invention has the advantages of easy control and saving huge investment for preparing steam by desalted water.

FIG. 1 is a schematic view of a steam purification apparatus of a shift system of a synthetic ammonia plant

The steam purifier of the conversion system of the synthetic ammonia plant shown in figure 1 comprises a purifier tank 1, alumina spherical filler 2 is arranged in the purifier, a steam inlet pipe 3 is arranged at the upper part of the purifier, a conversion gas inlet pipe 4 is arranged at the lower part of the purifier, an outlet 5 for purified steam and conversion gas mixture is arranged at the lower part of the purifier, a conversion gas straight-through secondary line 6 is arranged beside the purifier, a regulating valve 7 is arranged, the secondary line and the regulating valve are used for regulating conversion gas quantity so as to regulate the temperature of part of the conversion gas and the steam after mixing, nitrogen or steam inlets and outlets 8 and 9 are arranged at the upper part and the lower part of a filler layer of the purifier and are used for introducing nitrogen or steam when the filler is unloaded so as to prevent.

The embodiment, Anhui and Hunan middle and small ammonia synthesis plants omit desalted water equipment for preparing steam, a conversion system uses the steam purification method and device of the invention, the diameter of a conversion furnace is 3000mm, the diameter of a purifier is 800mm, the height is 1.0 m, alumina balls with the diameter of 4mm are filled in the conversion furnace, the diameter of a gas main pipeline is 426mm, the diameter of a secondary pipeline is 216mm, after the purifier is used for half a year, the purifier is blocked by impurities, alumina filler in the purifier is taken out only in half a day, sieved and reassembled for use. Therefore, soluble impurities in steam or/and mist are prevented from entering the conversion catalyst bed layer, and the normal production of the conversion process is ensured.

Claims

1. A steam purifying method for the transform system of synthetic ammonia plant features that the steam and part of transform gas are mixed and superheated to dew point, then they are fed into a fixed-bed steam purifier to make the soluble impurities in steam and/or fog be separated out, trapped and deposited on the filler in the purifier, and the purified steam is fed into transform furnace.

2. The steam cleaning method as claimed in claim 1, characterized in that the mixture of steam and partial change gas is superheated to 10-100 ℃ above the dew point and then enters a fixed bed steam cleaner for cleaning.

3. A steam cleaning method according to claim 1 or 2, characterized in thatthe mixture of steam and partial change gas is superheated to 30-50 ℃ above the dew point and then enters a fixed bed steam cleaner for cleaning.

4. A steam purification device of a conversion system of a synthetic ammonia plant comprises a fixed bed purifier (1), and a filler (2), a steam inlet (3) and a gas outlet (5) which are arranged inside the purifier (1), and is characterized in that a conversion gas inlet (4) is arranged at the steam inlet end, a conversion gas direct-through auxiliary line (6) and a regulating valve (7) are arranged beside the purifier (1), nitrogen or steam inlets and outlets (8) and (9) are arranged above and below the filler layer, the diameter of the purifier (1) is 10-100% of the diameter of a conversion furnace, and the height of the purifier (1) is 1.0-2.0 times of the diameter.

5. Steam cleaning apparatus according to claim 4, characterized in that the diameter of the cleaner (1) is 30-40% of the diameter of the shift converter.

6. Steam cleaning plant according to claims 4 and 5, characterized in that the diameter of the secondary line (6) for the through passage of the ventilation gas is-1/2 of the primary pipe diameter.

7. A steam cleaning device according to claim 4, characterized in that the packing (2) is an alumina ball, ring, or spent shift catalyst.