MTO Plant Equipment Position

This post was last edited by SAN*NGR428 on 2015-11-15 at 19:27. The on-site supervisors are all provided by the general contractor; there are too many devices, so if any supervisors are needed, they should be from a third party. The technical exchange phase (note: this is not the procurement phase involving negotiations and signing of technical agreements) is the stage for selecting a shortlist of key equipment, such as compressors, steam turbines, imported pumps, etc., including details such as the dry gas seal and couplings of the units ； Cyclone separators, electro-hydraulic slide valves, special valves for high and low temperatures, wear-resistant ball valves, etc., used in MTO – this is a critical phase for finalizing the shortlist; suppliers of inferior quality should be ruled out right away, otherwise regret will set in once operations start. During the negotiation phase of the technical agreement, it is important to specify the requirements in detail. If the turbines are purchased by the owner themselves, the supplier must provide a piping plan for the instruments of the anti-surge system as part of the agreement; it is also necessary to estimate the quantities of these materials generously, otherwise installation will be very problematic. As for units with separation units, I personally think that for the dry gas seal of the reaction gas compressor, a double-faced design rather than a structure with a labyrinth in between would be much better; however, design firms generally do not support this approach. A double-faced seal requires 40 kilograms of nitrogen, and it is also necessary to consider increasing the capacity of the cooling tank ； With four-stage compression, the process for the unit is quite complex; even if a double-end face design cannot be used, high-pressure nitrogen must be supplied as a backup gas source. Installing a pressure booster pump for the unit is not reliable, and it is difficult to maintain the pressure difference in the main seal of the high-pressure cylinder during shutdown. Using high-pressure nitrogen makes things much simpler. There are also very small but crucial spare parts such as booster pumps that must be ordered; otherwise it will cause a lot of trouble later on. Many of the design conditions for MTO deviate from reality; for example, the quench water and wash water filters are not put into use, and the catalyst hydrocyclone becomes clogged, resulting in poor performance ； The quench water washing system contains excessive oil and catalyst, deviating significantly from the design; this leads to blockages in the heat exchanger tubes as well as in the shell side, requiring periodic cleaning. It is also necessary to keep an extra supply of heat exchanger gaskets on hand ； For the pumps in the quench water washing system and those in the wastewater stripping system, it is best to use PLAN32 external flushing, as it provides a longer service life for mechanical seals. If PLAN11, PLAN21, PLAN23, or similar options are chosen, frequent maintenance will be required during operation. The design margin of the drain valve in the steam heat exchanger of the methanol feed heating system must be large ； In the dryer and protection beds of the separation unit (regeneration of the hydrogenation reaction gas is not considered; basically, these beds are not used for regeneration), the temperature of the gas used for regeneration rarely reaches the designed level, resulting in poor regeneration efficiency. It is recommended to incorporate electric heaters in series or as bypasses when using steam for heating N2; the design should ensure that the temperature required for regeneration can be achieved solely by using electric heaters, without relying on steam heaters. When designing the heat removal in the coils of the MTO reaction gas or regenerator, it is essential to pay attention to this aspect; if there is a gas-liquid two-phase flow inside the tubes, the support structure for those tubes must be strengthened. Sufficient space must be reserved on the heat exchanger frame for future core extraction, and maintenance space for the pumps is also important; it is best to provide each pump with designed lifting points, and during design, it is sufficient to extend support beams from the columns. On-site construction is troublesome, with so many concealed works; the cleanliness of the pipes used in underground work is very important, and strict standards must be maintained regarding the backfill soil. Next is the inspection of the cast-in-place piles (in fact, many of the rebar frameworks do not meet the standards, especially regarding the insufficient number of spot welds; the quality deteriorates as one goes deeper. It is essential to supervise the grouting process, as grouting is often carried out at night so as to cut corners. Who knows what was used for grouting down there? Who knows whether the rebar frameworks are long enough or how the connection points were welded? ) MTO has many lining equipment, and the method of applying the lining material can be pouring or spraying; it is essential to review the plan before starting work, and to visit the site frequently during construction – you will find that it is very difficult to carry out the plan as planned. For the welding inspection of anchor pins, it is necessary to personally bend a few samples for inspection; when the deadline is tight, the quality of welding work is very poor. There is also the need for a dedicated person to handle equipment unboxing; otherwise, the spare parts that come out will get lost. The pressure testing of valves on-site must be supervised by a dedicated person from the owner; otherwise, after the system is put into operation, leaks will occur in various valves, and the equipment that needs repair cannot be isolated. It’s a real hassle. This is also related to the preliminary shortlist of suppliers – under no circumstances should unreliable suppliers be chosen for the supply of critical manual valves. Upon receipt, inspect heat exchangers and containers for internal cleanliness, whether they are dry, and whether there are any scratches on the flange surfaces. This is especially true for heat exchangers, as it’s difficult to dry their interiors; over time, severe rusting occurs, and cleaning them through purging takes a long time without achieving complete cleanliness. When signing the technical agreement, it is essential to require N2 protection for the key heat exchangers; detailed provisions regarding the protection of the flange surfaces must also be included in the agreement. Otherwise, when equipment without matching flanges arrives, those flanges will have no protective measures, or there will only be a plastic cover, which is hardly sufficient to protect the flange sealing surfaces – in some cases, it cannot even prevent rain from reaching them. The topcoat color of the equipment should be uniform; otherwise, having red and gray colors together looks unsightly. Those who need it can communicate separately.

It’s written very comprehensively and in great depth; it’s worth learning from*. But do we need to conduct pressure testing on all valves? Our company didn’t carry out pressure testing on valves at that time, nor on heat exchangers; only pressure testing of the towers was done.

Valve pressure testing is carried out at specialized valve testing stations； The workload related to hydraulic testing on heat exchangers and towers on site is quite large. For some heat exchangers, the hydraulic testing is carried out at the factory, and no further testing is needed on site; however, for larger heat exchangers, it is still necessary to have their tube bundles and shells delivered separately. The hydrostatic testing of the tower and that of the heat exchanger should be considered as a whole, which can save a lot of water.

For many projects, due to schedule and funding constraints, heat exchangers are not pressure-tested again before installation on site, and this practice is not recommended.