Process for producing synthetic ammonia or methanol by using calcium carbide furnace tail gasThe technical field is as follows: the invention belongs to the field of inorganic chemical industry, and particularly relates to a process for producing synthetic ammonia or methanol by using calcium carbide furnace tail gas.
Background art: calcium carbide production is generally carried out in a calcium carbide furnace, high temperature is generated through electric arcs, and calcium oxide reacts with carbon to generate carbonized calcium (calcium carbide) and carbon monoxide. The tail gas of the closed calcium carbide furnace contains more than 50 percent of carbon monoxide, a large amount of dust, a small amount of nitrogen, hydrogen and the like.
The process for synthesizing ammonia is a well-established process, which generally uses charcoal (anthracite or coke), natural gas (methane) and oil (hydrocarbons) as raw materials, and produces carbon monoxide, hydrogen and nitrogen (from air) through coal gasification or cracking reaction, then converts carbon monoxide into hydrogen through conversion, and the hydrogen and nitrogen are synthesized in a synthesis tower to obtain synthetic ammonia.
Methanol synthesis is also a conventional process and is generally obtained by catalytic synthesis of carbon monoxide and hydrogen.
At present, the known tail gas of the calcium carbide furnace is generally subjected to dust removal treatment, some tail gas is directly discharged and some tail gas is used as fuel, and Chinese patent CN1048917 discloses a method for recovering furnace gas of a closed calcium carbide furnace, and the main contents of the method are waste heat recovery and dust removal. Chinese patent CN1461936 discloses a 'method for removing dust from furnace gas of calcium carbide furnace and utilizing the same', and the technical scheme only relates to the recovery of tail gas waste heat. Chinese patent CN2601124 discloses a 'closed calcium carbide furnace gas purification system', which mainly adopts a set of wet dust removal device to remove dust in tail gas, and how to dispose the dust-removed gas is not involved.
In fact, wet dedusting is also a well-established method, i.e. the dust in the tail gas is washed away by water.
The invention content is as follows: the invention aims to overcome the defects of the prior art, and provides a process for producing synthetic ammonia or methanol by using tail gas of a calcium carbide furnace as raw material gas.
The purpose of the invention is realized according to the following scheme:
the tail gas is led out from a closed calcium carbide furnace, washed with water and dedusted, and then enters a synthetic ammonia or methanol synthesis system to produce synthetic ammonia or methanol;
the gas after being washed and dedusted firstly enters a conversion section of synthetic ammonia to convert carbon monoxide into hydrogen, then a proper amount of nitrogen is added according to the hydrogen-nitrogen ratio of the synthetic ammonia, and then the gas enters a synthetic tower;
adding a proper amount of hydrogen into the gas after washing and dedusting according to the proportion of carbon monoxide and hydrogen synthesized by methanol, and feeding the gas into a methanol synthesis tower to synthesize methanol;
the gas after being washed and dedusted is converted into hydrogen suitable for methanol synthesis through partial carbon monoxide self-transformation according to the proportion of carbon monoxide and hydrogen synthesized by methanol, and then enters a methanol synthesis tower to synthesize methanol.
Compared with the prior art, the invention has the following characteristics:
1. the tail gas of the calcium carbide furnace is used as the raw material to produce the synthetic ammonia or the methanol, and a new raw material gas source for producing the products is developed.
2. The carbon monoxide in the tail gas of the calcium carbide furnace is fully utilized and converted into more valuable synthetic ammonia or methanol instead of being simply converted into a heat source.
3. The production cost of synthetic ammonia or methanol is reduced, the economic benefit of the product is improved, and meanwhile, the cost of the calcium carbide furnace tail gas pollution treatment can be indirectly reduced, which is beneficial to the establishment of the recycling economy circle in the field.
The specific implementation mode is as follows:
example 1: the closed calcium carbide furnace enters a wet dust removal system through a flue, dust in tail gas is washed away by water, the tail gas enters a conversion system for synthesizing ammonia after the components of the gas are measured, and the tail gas passes through a conversion reaction (A)
) Conversion of CO to H
2Measuring the gas composition again, based on the measured H
2And N
2Amount according to the synthesis ammonia reaction (
)N
2The demand of (2) is supplemented by N through an air separation system
2And entering a synthesis tower for synthesis reaction to obtain synthetic ammonia.
Example 2: the closed calcium carbide furnace enters a wet dust removal system through a flue, dust in tail gas is washed away bywater, and the tail gas enters a methanol conversion system after the components of the gas are measured, and is subjected to conversion reaction (A)
) Partial conversion of CO to H
2Measuring the gas composition again, based on the measured H
2And CO amount according to the methanol synthesis reaction (
)H
2The demand make-up section H
2And entering a methanol synthesis tower for synthesis reaction to obtain methanol.
Example 3: the closed calcium carbide furnace enters a wet dust removal system through a flue, dust in tail gas is washed away by water, gas components are measured and then enter a methanol conversion system, reaction and measurement are carried out simultaneously, and the conversion reaction is controlled (
) Conversion of CO to H
2In an amount sufficient for the methanol synthesis reaction (c)
)H
2Then the obtained product enters a methanol synthesis tower for synthesis reaction to obtain methanol.