The present invention relates to packaging, handling and transporting catalyst to a chemical reactor tube, including furnace and reformer tubes.
A chemical reactor is typically a large vessel designed to accommodate a chemical reaction. The reaction is often exothermic, so the reaction often takes place in a shell and tube heat exchanger, with the reaction occurring inside the tubes and a coolant circulating outside the tubes. The vessel also can be a simple tank with a single volume of catalyst inside it. The chemical reaction also can occur in a single large tube. Some chemical reactions are done in furnace or reformer tubes, which may be a part of a system with 10 to 500 or more such tubes. Catalyst, typically in the form of pellets, may be loaded inside any of these reactor tubes to facilitate the reaction. The catalyst is replaced periodically.
The reactor tubes may be quite large, housed in a structure several stories tall, in which case the catalyst may be transported up several stories to an elevation above the top of the tubes so it may then flow by gravity into the top of the tubes. The catalyst typically is supplied in 2,000 or more pound “super sacks”, 55 gallon drums, mini drums, metal bins or plastic bags loaded in pallet-mounted cardboard boxes.
The catalyst usually is trucked to the job site and dropped off at a catalyst staging area. To get the catalyst to the reactor vessel and its tubes, typically each catalyst container (super sack, drum, bin, box or bag) is first transported, via forklift truck, from the catalyst staging area to a crane or elevator staging area. The catalyst container is then loaded onto the elevator or secured to the crane by a member of the rigging crew, and the crane operator then lifts the load in accordance with verbal instructions and/or hand gestures issued by a crane spotter. A member of the rigging crew handles the tag line to guide and maintain control of the load as it is positioned over or near the reactor. The containers of catalyst may be set onto a hand truck on the top deck of the structure. The catalyst container is then hand trucked to a point adjacent a manway of the reactor vessel where the catalyst is manually poured or scooped into buckets and other containers such as hoppers with a calibrated volume or with a weight loaded charge per tube or otherwise handled and transferred into the reactor vessel for loading into the reactor tubes.
Sometimes, the crane also is used to hold the super sack of catalyst above the reactor vessel while the catalyst is gradually emptied from the super sack and loaded into the reactor tubes using a sock-like outlet hose that is integrated into the super sack design. The contents of the super sack may or may not pass by or through a screening device to remove dust and fines. Loading catalyst directly from the super sack further ties up the crane, and it is very difficult to control the volume of catalyst discharged from the super sack as well as minimize the amount of catalyst dust generated when this method of discharge is utilized. Flat open space to stage and store catalyst often is limited and at a premium in the area surrounding the upper part of the reactor.
The existing methods for transporting the catalyst are very labor intensive, requiring a forklift operator, a forklift spotter (who typically walks along the forklift truck to ensure that the forklift truck or its load does not injure personnel or hit something), a crane rigger, a crane operator, a crane spotter, a load tag-line handler, one or more people to “manhandle” the catalyst container from the spot where it is dropped by the crane to a spot adjacent the reactor vessel, or one or more people to “manhandle” the catalyst container into a hopper or screening device located above the tube, and one or more people to tend to the outlet of the sock at the end of the super sack or the outlet hose if a screening device is used.
Just as critical is the fact that “flying” catalyst (as it is referred to when using a crane to lift the catalyst to the top deck of the structure near the top of the tubes) cannot be performed during high wind conditions, nor is it desirable to do so when it is raining, as it is important to keep the catalyst and the reactor dry at all times. Furthermore, the crane and crane operator rental fee are very expensive and, typically, the crane is not available for any other task while it is “flying” catalyst Cranes for flying catalyst may also be in short supply since when the reactor is out of service much or all of the connected plant is also out of service and may have sub-systems that are being maintained at the same time as the reactor and tubes. The crane requires a significant surface area (footprint) especially for its outriggers that are used for support. The crane also requires a significant amount of three dimensional space in which to operate in and around which personnel must use caution to avoid being under the boom and load as well as keeping clear of the swing of the boom. For plants with multiple reactors, a dedicated crane often is necessary for simultaneous work, placing further restrictions and limitations on crane operation. The crane(s) block access to the reactor and other nearby equipment that also may need to be serviced when the reactors are undergoing catalyst handling activities. Important work in, on, or near the reactor may need to be suspended until the crane can be moved into or out of position. Older reactors are particularly crowded during catalyst handling with the catalyst staging areas and crane taking up what is very limited space, leading to congestion, trip hazards, and blocked lines of sight. The cranes are typically diesel powered, resulting in a continuous source of emissions which can be harmful to personnel working in the area as well as being non-environmentally friendly. Some cranes produce a high noise level when operating and thus contribute to the overall noise level in the vicinity of the crane. High noise levels are known to result in increased stress on workers and to lower their efficiency.
Catalyst is typically a friable material (meaning that it is brittle, fragile, and easily crumbled, often even by hand). The weight of the catalyst itself in the super sacks or other containers, during transportation to the job site, and especially after being jostled, picked up and dropped by the forklift truck, the crane, the hand truck or dolly and even during unloading from the containers, can result in a considerable amount of broken catalyst and catalyst dust generation, both of which can have detrimental effects on the operation or performance of the reactor. It should also be noted that catalyst is both very expensive and very valuable, so it is desirable to keep the catalyst intact as much as possible, and to avoid breaking it or crushing it. Also, the creation of catalyst dust is undesirable from the point of view of the workers who have to deal with the catalyst and do not wish to be exposed to the dust. It is preferable that dust generation be held to a minimum at all times for reasons of performance, health and safety, the environment, and cost savings.
The super sack acts as a bin but without internal controls to prevent any classification (sorting by size) that can occur in bins or bags. Classification is undesirable, since it is commonly known that smaller pieces of material, in this case, catalyst fines and dust, will tend to automatically segregate or classify themselves from the larger and whole pieces of catalyst particles such that, when a sizable volume of catalyst in a pelletized form is discharged from a container, a significant amount of segregation can occur, as measured through accurate pressure-drop testing after loading the tubes. Classical segregation models show that it is common for significant particle-size variation to occur within a container of the size of a super sack. This segregation is undesirable, because it means that the flow of reactants will not be consistent throughout the reactor, which reduces the efficiency of the reactor and may create hot spots or other problems.