Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Ammonia synthesizer
Reexamination Certificate
1999-02-18
2001-04-10
Beck, Shrive (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Ammonia synthesizer
C422S186220, C422S198000, C422S198000, C422S198000, C422S198000, C422S208000, C422S211000, C422S218000
Reexamination Certificate
active
06214296
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a gas-solid phase catalytic reaction process and the apparatus for the embodiment of the method. Said process is useful for gas-solid phase catalytic reactions and heat transfer in the field of chemical engineering, in particular for the synthetic reaction of ammonia, as well as the synthesis of methanol, methane and methyl ether.
BACKGROUND OF THE INVENTION
In gas-solid phase exothermic catalytic reactions such as the synthesis of ammonia from hydrogen and nitrogen under pressure, there exists an optimal temperature for fixed pressure and fixed composition of reactant gases, under which temperature the reaction rate is the highest. This optimal temperature, however, decreases as the synthesis rate increases, and with the proceeding of the reaction, the temperature of the catalyst layer will be raised by the continuous releasing of the reaction heat. Thus, in order to improve the efficiency of the reactor, it is necessary to remove the reaction heat out of the reactor. One method that has been widely used is the multi-stage feed-gas-quench reactor, such as the Kellogg four-stage catalyst beds used in large scale ammonia plants. In such systems, feed-gas-quench is used between the stages to reduce the reaction temperature. But as the temperature of the reactant gases is reduced by feed-gas-quench, the concentration of the product of reaction is reduced at the same time, so the synthesis rate is also affected. Improved forms have appeared, in the better ones, the catalyst is divided into three beds. While feed-gas-quench is used between the first and the second section, indirect heat exchange is used between the second and the third section, see, for example, the Chinese patent application CN1030878 filed by the Casale Co. and published on Feb. 8, 1989. The affect on the concentration of the product of reaction by feed-gas-quench has not been completely overcome in this kind of reactors, and the structure of the equipment is made complicated by the adding of indirect heat exchangers between the layer beds.
SUMMARY OF THE INVENTION
The object of the present invention is, in accordance with the characteristics of the gas-solid phase catalytic exothermic reversible reactions, to provide an improved reactor that can overcome the disadvantages of the prior art and a method in which the reaction is operated under the optimal temperature. The technical features of the reactor are reasonable temperature distribution in the bed layers, high activity of the catalyst, simple and reliable structure, and good operating performance.
The reversible gas-solid catalytic exothermic reaction and the releasing of heat mainly occur at the initial stages of the reaction process. The purpose of the present invention is fulfilled by the following improvements. Firstly, the feed gas is divided into two streams, streams
1
and
2
, to be warmed respectively. Stream
1
is warmed by exchanging heat with the reaction gases exiting from the catalyst bed, and stream
2
flows in the cold tubes in the upper part of the catalyst layer and is warmed by exchanging heat with the counter-flowing reactant gases outside of the tubes. The flow rate and temperature of stream
2
in the cold tubes can be adjusted in accordance with the temperature of the catalyst layer. Secondly, the warmed streams
1
and
2
are combined together, react in the cold tube catalyst layer and exchange heat with the feed gas in the cold tubes, and then the reactant gases enter the lower part of the catalyst layer and react adiabatically. Thus, in the initial stage of the reaction, heat exchange is effected by counter-flow cold tubes, the reaction can start at an approximately adiabatic condition, so that the optimal temperature can be reached more quickly. As the heat exchange with the counter-flow cold tubes proceeds, the temperature difference between the interior and exterior of the tubes increases with the depth in the catalyst layer, so that the temperature of the catalyst decreases along the optimal line. At the outlet of the cold tube layer, the temperature of the catalyst decreases below the optimal line, and the catalyst is ready for the adiabatic reaction in the next stage.
The synthetic reactor of the present invention consists substantially of a housing P, a catalyst basket R and an heat exchanger E. The housing P can withstand pressure, the reaction pressure therein is typically 14-32 MPa. The catalyst basket R consists of a cover plate H, a cylinder S and a catalyst supporting grid J, the catalyst in the basket is supported on the supporting grid J at the bottom of the basket R. The catalyst layer consists of a cold tube catalyst layer K
1
having therein counter-flow cold-tube bunch Cb and an adiabatic catalyst layer K
2
. The cold tube bunch Cb consists substantially of an inlet tube a, the cold tubes b and a ring tube d
1
connecting the inlet tube a and the cold tubes b. The cold tube bunch Cb may also consist of an inlet tube a, cold tubes b, an outlet tube c, a ring tube d
1
connecting the inlet tube a and the cold tubes b, and a ring tube d
2
connecting the cold tubes b and the outlet tube c. The cold tube catalyst layer K
1
may have one or more cold tube bunch(es) Cb arranged concentrically, each bunch has a plurality of cold tubes b arranged concentrically at circles of different radii, and a central tube I connecting the heat exchanger E is located at the center of the catalyst layer. The feed gas enters the reactor from the inlet tube a, and is distributed to the plurality of cold tubes through the ring tube d
1
. The feed gas stream
2
in the tubes is heated by the high temperature reaction gases outside the tubes counter flowing in the catalyst layer K
1
. The heated stream either exits from the cold tubes b directly or exits through the ring tube d
2
and the outlet tube c. The exit stream
2
is then mixed with stream
1
, which has been heated in the heat exchanger and exited from the central tube I. The temperature of the mixture is elevated to a temperature above the active temperature of the catalyst. And the gas stream enters successively into the cold tube catalyst layer K
1
and the adiabatic catalyst layer K
2
. In cold tube catalyst layer K
1
the gases react and exchange heat with gas stream in the cold tubes b in a counter flowing manner, and the gases react adiabatically in the adiabatic catalyst layer K
2
. The ratio of the temperature of the gas stream
2
exiting the cold tubes to the temperature of the mixed gases entering the cold tube catalyst layer is 0.75-1.25. The amount of the catalyst in the cold tube catalyst layer is 15-80% by weight, preferably 30-50% by weight of the total amount of the catalyst, depending on the reaction conditions. The gas in the cold tube catalyst layer K
1
and the adiabatic catalyst layer K
2
may both flow in the axial direction; or the gas may first flow axially in the cold tube catalyst layer K
1
, and then flow radially and axially in the adiabatic catatyst layer K
2
; or flow counter-currently in the adiabatic catatyst layer K
2
. The cold tubes b may be round or flattened ones. The ratio of the heat-conducting area of the cold tubes to the volume of the catalyst is 3-20 M
2
/M
3
.
REFERENCES:
patent: 3663179 (1972-05-01), Mehta et al.
patent: 5190731 (1993-03-01), Stahl
patent: 2067184U (1990-12-01), None
patent: 1104126 (1993-06-01), None
patent: 1088476 (1994-06-01), None
Lou Ren
Lou Shoulin
Beck Shrive
Merchant & Gould
Varcoe Frederick
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