Acetylene removal methods and apparatus

Abstract

The present invention provides a method and apparatus for removing acetylene from a gasoeus mixture comprising hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, butane, butenes, butadiene, and other C4 or higher hydrocarbons. The method of the invention utilizes a front-end acetylene removal unit (“ARU”) located after a charge gas compressor in which acetylene is selectively reduced. The method of the invention achieves selective reduction of acetylene by using a proprietary Chevron Phillips E series palladium based catalyst. The method of the invention also utilizes a novel startup procedure, a novel emergency shutdown procedure, a novel maximum cool down procedure, and a novel carbon monoxide monitoring procedure.

1 . A method of starting an acetylene removal system which comprises:
 one or more cracking furnaces;   a multistage compressor in communication with the one or more cracking furnaces for compressing the raw cracked gas;   one or more acetylene removal units in communication with the multistage compressor, each acetylene removal unit comprising:   a palladium containing catalyst that selectively reduces acetylene to ethylene, wherein the one or more acetylene removal units are capable of operating for a period of not less than one year before regenerating of the palladium catalyst is necessary and wherein the raw cracked gas flows from the one or more cracking furnaces to the multistage compressor and then through each of the one or more acetylene removal units;   a bypass conduit for diverting the raw cracked gas mixture such that the raw cracked gas mixture does not flow through the one or more acetylene removal units.   a series of post-acetylene reduction purifiers for separating and purifying hydrocarbons contained in the raw cracked gas mixture after acetylene reduction; and   a recycling conduit located upstream from the series of pos-acetylene reduction purifiers for recycling gas that has flowed through the bypass conduit or through the one or more acetylene removal units to the multistage compressor,   
       the method comprising:
 flowing an inert gas through the multistage compressor, the bypass conduit, and the recycling conduit for a sufficient time that the acetylene removal system achieves a sufficient operating pressure; 
 allowing at least a portion of inert gas to flow through the one or more acetylene removal units until the acetylene removal units achieve a sufficient operating pressure; and 
 introducing a cracked raw gas into the compressor such that at least a portion of the cracked gas flows through the acetylene removal units. 
 
     
     
         2 . The method of  claim 1  wherein the inert gas comprises a gaseous component selected from the group consisting of low sulfur alkanes, nitrogen gas, and combinations thereof. 
     
     
         3 . The method of  claim 2  wherein the inert gas comprises a methane gas. 
     
     
         4 . The method of  claim 1  wherein the raw cracked gas mixture is cooled prior to contacting the one or more acetylene removal units. 
     
     
         5 . The method of  claim 1  wherein carbon monoxide is added to the inert gas prior to contacting the one or more acetylene removal units if one or more of the acetylene removal units contains fresh catalyst. 
     
     
         6 . The method of  claim 5  further comprising reducing the carbon monoxide or injecting a sulfur containing compound into the raw cracked gas mixture. 
     
     
         7 . The method of  claim 5  further comprising increasing the temperature to a sufficient temperature to commence acetylene reduction. 
     
     
         8 . The method of  claim 5  wherein the temperature of the raw cracked gas mixture is increased to a temperature from about 120° F. to about 150° F. 
     
     
         9 . A cracked gas purification apparatus for removing acetylene from a raw cracked gas mixture comprising hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, butane, one or more butenes, and butadiene, the apparatus comprising:
 one or more cracking furnaces, each cracking furnace having:   an inlet port through which a hydrocarbon feed stock is introduced,   a heating section in which the hydrocarbon feedstock is heated to a sufficient temperature to form the raw cracked gas mixture, and   an outlet port out of which the crack gas mixture flows;   a multistage compressor in communication with the one or more cracking furnaces for compressing the raw cracked gas;   one or more acetylene removal units in communication with the multistage compressor, each acetylene removal unit comprising:   a palladium containing catalyst that selectively reduces acetylene to ethylene,   an ARU inlet port;   an ARU outlet port;   
       wherein the one or more acetylene removal units are capable of running for a period of not less than one year before regenerating of the palladium catalyst is necessary and wherein the raw cracked gas flows from the one or more cracking furnaces to the multistage compressor and then through each of the one or more acetylene removal units; and
 a bypass conduit for diverting the raw cracked gas mixture such that the raw cracked gas mixture does not flow through the one or more acetylene removal units. 
 
     
     
         10 . The apparatus of  claim 9  further comprising one or more carbon monoxide monitors, wherein at least one carbon monoxide monitor is in the vicinity of each outlet port of the one or more cracking furnaces. 
     
     
         11 . The apparatus of  claim 10  further comprising one or more sulfur injection units, wherein at least one sulfur injection unit is located 0. in the vicinity of each inlet port of the one or more cracking furnaces. 
     
     
         12 . The apparatus of  claim 9  further comprising a cooling unit for cooling the raw cracked gas mixture upon occurrence of a predetermined condition, the cooling unit being located upstream of one or more acetylene removal units. 
     
     
         13 . The apparatus of  claim 12  further comprising one or more auxiliary cooling units for supplying additional cooling of the cracking gas upon occurrence of the predetermined condition, wherein the one or more acetylene removal units include at least two acetylene removal units and wherein the auxiliary cooling units are interposed between each of the acetylene removal units. 
     
     
         14 . The apparatus of  claim 12  further comprising a heating unit for reheating the raw cracked gas mixture, the heating unit being located upstream of one or more acetylene removal units and downstream of the cooling unit. 
     
     
         15 . The apparatus of  claim 14  further comprising a carbon monoxide monitor upstream of the cooling unit and downstream of the multistage compressor. 
     
     
         16 . The apparatus of  claim 14  further comprising a carbon monoxide monitor downstream of the heating unit. 
     
     
         17 . The apparatus of  claim 9  further comprising a plurality of temperature measuring devices positioned at a plurality of locations in the one or more acetylene removal units. 
     
     
         18 . The apparatus of  claim 9  further comprising one or more temperature measuring devices positioned near the exit port of the one or more acetylene removal units.