JPH0565222B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention is applicable to gas purification for removing impurities such as organic sulfur, NOx, dienes, etc. from coke oven gas (coal carbonization gas) for city gas.
This invention relates to a catalyst that can simultaneously decompose and remove these impurities at 160°C and at a low temperature and pressure higher than normal pressure. [Prior art] Coke oven gas for city gas usually contains sulfur as impurities of 0.10 to 0.15 g/Nm3, and ^0.3 to 0.15 g/Nm3.
Contains 0.4ppm of NOx and 150-250ppm of dienes, which polymerize in the pipes and produce gum substances such as sulfur gas and NO gum, which can cause clogging of combustion equipment, poor combustion, and poor pressure regulation. It has become the causative agent. In addition, sulfur, mainly organic sulfur, is oxidized during combustion and reacts with copper or copper alloys in gas appliances, producing white powder mainly composed of copper sulfate, causing combustion failure and causing corrosion of heat exchangers, etc. This is a major negative factor compared to competing fuel gases. In recent years, city gas has become increasingly high-calorie (13A), and coke oven gas has also been converted into alternative natural gas (SNG) using a catalytic chemical reaction. Pretreatment of sulfur compounds and gum substances that degrade catalyst performance has become a very important issue. Conventionally, H ₂ S from coke oven gas (COG) can be easily removed by solution absorption method or dry desulfurization method, but organic sulfur compounds such as COS and CS ₂ can be removed by Ni at relatively high temperature and high pressure. -Mo-based removal catalyst and Co
A hydrodesulfurization method using a -Mo catalyst was used. The method for purifying this coke oven gas is
High purity coke oven gas is produced by removing dienes, oxygen and sulfur compounds by contacting coke oven gas from which polymers and aromatic compounds produced due to the presence of NOx have been removed with a hydrodesulfurization catalyst under specific conditions. A method for obtaining this is disclosed in Japanese Patent Publication No. 58-12318. In addition, there is a special method for removing various impurities in COG at once by flowing COG from the inlet of coke oven gas into an adsorption tower filled with silica gel and zeolite in that order, and after preliminary purification, introducing it into an adsorption purification device. It is disclosed in Japanese Patent Publication No. 113689/1989. There are two methods currently in practical use for COG purification using this hydrogenation method: the Osaka Gas method and the Tokyo Gas method. All of these are installed as COG pretreatment and purification equipment in SNG plants. In the former method, dust and oil mist are first removed from the COG using a filter, and then high-boiling hydrocarbons and hydrogen sulfide are adsorbed and removed using an adsorption tower filled with activated carbon. Next, COG is compressed to 20Kg/cm ² G.
The pressure is increased to 1,000 ml, preheated by a heat exchanger, and then led to a hydrogenation reaction tower. In the hydrogenation reaction tower, Ni・
Due to the action of the Mo catalyst, sulfur compounds in COG react with hydrogen and convert into hydrogen sulfide. Oxygen and olefin compounds in COG similarly react with hydrogen in the hydrogenation reaction tower and change into water and paraffin compounds. The hydrogen sulfide generated in the hydrogenation reaction tower is transferred to the adsorption desulfurization tower, which is connected to the zinc oxide (ZnO) packed in the tower.
It is removed by adsorption. In the latter method, the pressure of COG is increased from normal pressure to 50 kg/cm ² G, oil mist is removed in the first separator, the COG is preheated to 160-200°C in the preheater, and then the COG is heated in the second separator.
It is then led to an adsorption separator to remove generated NO gas and other gum substances. Next, the COG is guided to the next first hydrogenation tower,
Dienes are hydrogenated and saturated using a palladium (Pd) catalyst. At this time, the recycled gas used for temperature control of the catalyst bed is a part of the second hydrogenation tower outlet gas, but this gas is heat exchanged with COG in a preheater and recycled gas is separately provided. The pressure is increased by the compressor and merges with the COG at the preheater inlet. The gas saturated with dienes contained in the first hydrogenation tower is heated to 350-400℃ in a heating furnace, enters the second hydrogenation tower for hydrodesulfurization, and is converted into cobalt and molybdenum (Co・Mo). The catalyst converts sulfur compounds (organic sulfur compounds) in the gas into hydrogen sulfide (H ₂ S) by reacting with hydrogen. This H ₂ S enters the adsorption desulfurization tower and is adsorbed and removed by the packed zinc oxide (ZnO). [Problem to be solved by the invention] As mentioned above, the coke oven gas purification method currently in practical use involves several pretreatment steps under high temperature and pressure to remove impurities (organic sulfur, NOx, etc.) in the coke oven gas. , dienes) by adsorption treatment and catalytic chemical reactions using platinum metal catalysts, Co, Mo, Ni, etc. Therefore, the following problems arise. That is, high temperature (300-400℃), high pressure (20-35Kg/cm ² G)
Therefore, running costs are high, it is necessary to use heat-resistant and pressure-resistant materials for gas purification equipment, it is necessary to use expensive metals for catalysts, equipment costs are high due to the large number of purification processes, and catalysts are required due to the large number of purification processes. It is difficult to control the reaction. Therefore, the initial cost is
Due to high running costs, it is economically difficult to adopt this purification method. [Means for Solving the Problems] The present invention provides a catalyst for decomposing organic sulfur, NOx, and dienes that solves these problems. Furthermore, it is characterized by the addition of a basic compound. It has long been known that iron oxide-based catalysts are effective for desulfurization and denitrification, but the present inventors combined iron oxide with zinc oxide and copper oxide and further added a basic compound.
We succeeded in obtaining a catalyst that can efficiently decompose dienes as well as organic sulfur and NOx in COG. As the carrier, CaO, SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ or the like may be used alone or in an appropriate mixture. Iron oxide is mainly α-Fe ₂ O ₃ and has a particle size of 60μ.
Ultrafine powder of less than m is preferred. Such ultrafine iron oxide powder can be obtained by spraying a solution of iron powder dissolved in dilute hydrochloric acid or the like together with fuel at 700 to 800°C and roasting. Commercially available industrial zinc oxide (ZnO) and copper oxide (CuO) can be used as they are. The basic compounds added thereto are suitably alkali metal or alkaline earth metal oxides and carbonates. Examples of oxides include CaO,
MgO, etc., and examples of carbonates include NaHCO ₃ ,
Examples include Na ₂ CO ₃ , CaCO ₃ , K ₂ CO ₃ and the like. The composition of the catalyst is approximately 30-80% by weight of iron oxide,
Zinc oxide 2-15% by weight, copper oxide 2-15% by weight
Appropriate amounts are approximately 10 to 30% by weight of the carrier, and approximately 1 to 10% by weight of the basic compound free of additives. The method for producing this catalyst is to mix iron oxide, zinc oxide, and copper oxide, then add a carrier, basic compound additives, and water, and granulate the mixture to remove crystallization water.
It can be lightly roasted at about 100 to 400℃. The carrier and the basic compound may be added together with iron oxide and the like.
The particle size is suitably about 5 to 20 mm, preferably about 7 to 15 mm. The catalyst of the present invention can simultaneously decompose organic sulfur, NOx, and dienes at a relatively low temperature and pressure of 120 to 300°C and above normal pressure. The flow rate of the target gas for purification can be used in the space velocity (SV) range of about 100 to 1000 hr ^-1 , and extremely good removal results can be achieved at a flow rate of 650 hr ^-1 or less. In addition, catalyst regeneration is performed by introducing a small amount of air and steam to regenerate Fe ₂ S ₃ ,
Catalysts that have changed to sulfides such as FeS are regenerated into Fe ₂ O ₃ and can be used continuously for a long period of time. FIG. 1 shows a process diagram of an example of an apparatus for refining COG using the catalyst of the present invention. COG is fed through line 1, and first filter 2 removes mist. Next, heating furnace 3, G/G heat exchanger 6
The mixture is preheated with air, mixed with air, and then enters the reaction tower 5 filled with catalyst. Air is introduced through line 10, preheated in heat exchanger 7, and then mixed. The mixing amount of preheated air is controlled by the controller 4 so as to be maintained within a predetermined range. This preheated air is preferably mixed immediately before the reaction tower in order to prevent NO oxidation and suppress the polymerization reaction of dienes. Reaction tower 5
The COG from which organic sulfur, NOx, dienes, etc. have been decomposed and removed is recovered by heat exchangers 6 and 7, further cooled by a cooler 8, and taken out from a purified gas discharge line 9. The cooler 8 is of a water-cooled type.
During catalyst regeneration, water vapor flows into the steam supply line 1.
1, mixed with air and sent to the reaction tower 5. This water vapor can also be used to control exothermic reactions. [Function] Due to the action of the catalyst of the present invention, organic sulfur reacts with H ₂ and H ₂ O generated by oxidation reaction in the catalyst layer.
Converted to H ₂ S, which is adsorbed by Fe ₂ O ₃ etc.
Fe ₂ S ₃ , FeS and other sulfides are removed. In addition, NOx forms complex compounds with sulfides and is fixed, or it undergoes catalytic reduction on the catalyst surface by reducing gases such as CO and H ₂ in COG, and is removed as N ₂ . Dienes are also removed by hydrogenation saturation or decomposition by H ₂ ·H ₂ O in COG. This catalyst has the great feature that it can undergo an oxidative exothermic reaction at a low temperature of 100 to 160°C and at a low pressure of normal pressure, and can maintain its activity for a long time. [Example] Waste acid (FeCl ₂ 20-30%) generated when steel plates are pickled with hydrochloric acid in the steel industry is spray roasted at 700-800°C to form α-Fe ₂ O with a particle size of 60 μm or less. Got ₃ powders. To this, 7.5% by weight each of ZnO and CuO were added and mixed uniformly, and cement (CaO64%,
After adding 30% by weight of SiO ₂ 22%, Al ₂ O ₃ 5%, etc., 7.5% of CaO and 20% of water and kneading it uniformly, 7~
It was granulated to a particle size of about 15 mm. 100 to 400 of this granulate
Roast at about ℃ for 1 hour to remove organic sulfur, NOx,
A catalyst for decomposing dienes was obtained. A COG purification test was conducted using this catalyst using the apparatus shown in FIG. COG is preheated to 100 to 140°C (120 to 160°C at start-up) using heat exchanger 6 and heating furnace 3, and the preheated air is heated to an O ₂ concentration of 0.5 to 3% (target catalyst The mixture was adjusted with controller 4 so that the temperature inside the layer was obtained. The pressure inside the catalyst layer is 1~6Kg/ ^cm2G , and the temperature is 140~250℃.
The space velocity (SV) was maintained at 600 hr ^-1 . Table 1 shows the impurity removal effects obtained as a result. In a steady state, the heat exchanger 6 sufficed for most of the temperature rise required for preheating the COG, and the fuel in the heating furnace was 0 to 30% of that at startup.

[Table] For comparison, catalyst A was granulated with only α-Fe ₂ O ₃ , and catalyst A was granulated with α-Fe ₂ O ₃ and CaO added to a siliceous mortar carrier containing SiO ₂ as the main component. Similar purification tests were conducted on Catalyst B and a commercially available iron oxide catalyst. Catalyst A and catalyst B were produced under the same conditions as above. The purification test results are shown in Table 2.

〔Effect of the invention〕

It has been found that the newly developed catalyst can remove sulfur (mainly organic sulfur), NOx, and dienes remaining in COG with an efficiency of over 90%. It was also confirmed that the removal effect was much higher than that of commercially available iron oxide systems. In addition, equipment pressure resistance and
Initial and running costs have been reduced by achieving a lower grade of heat resistance, simplified equipment configuration, reduced catalyst costs, and reduced heating costs, as well as being simple and easy to operate. We were able to develop the device. After use, the catalyst of the present invention can be reused as a raw material for iron manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of an example of an apparatus for refining COG using the catalyst of the present invention.

Claims (1)

[Claims] 1. An organic sulfur component in which iron oxide, zinc oxide, and copper oxide are supported on a carrier and a basic compound is added;
Catalyst for decomposition of NOx and dienes. 2. The organic sulfur component according to claim 1, wherein the carrier is composed of calcium oxide (CaO), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), magnesium oxide (MgO), titania (TiO ₂ ), etc. alone or in a mixture. ,
Catalyst for decomposition of NOx and dienes. 3. The organic sulfur component according to claim 1, wherein the basic compound additive according to claim 1 is an alkali metal or alkaline earth metal oxide or carbonate;
Catalyst for decomposition of NOx and dienes.