Diameter of the flow-limiting orifice plate on the pressure tapping pipe of the gasifier
Thread Content
This post was last edited by wang06120325 on 2015-10-18 21:21. High-pressure nitrogen is supplied to the pressure tapping pipe of the vaporization furnace for cooling and inerting purposes; this pipeline is activated before each start-up and material feeding process. The design includes two stop valves and a metal float flow meter. Flow meters often exhibit inaccurate measurements after being in use for a period of time. It is difficult to control the nitrogen flow rate merely by adjusting two shut-off valves; therefore, a combination of a flow-limiting orifice plate and a shut-off valve is planned to be installed to regulate the flow. I’m not sure what the appropriate pore size for the orifice plate is; for a pipeline with a diameter of 25, the gas flow rate is assumed to be 0.5 Nm3/h.
This post was last edited by HEJIYUER on 2015-10-18 at 21:17. Please provide the range of changes in upstream pressure, flow rate in NM/HR, and downstream pressure, so that it can be calculated. Is a flow rate as low as 0.1 Nm3/h assumed or actually required? Here is a reference post; see posts 2 and 3: http://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1471659
The flow rate is around 0.5 cubic meters, the nitrogen pressure is 10 MPa; the downstream pressure was determined using the pressure in the vaporization furnace. A software for calculating orifice diameters was used to carry out the calculations.
Having never worked with a vaporizer, I have to assume the downstream pressure. Based on the principle of flow restriction, the pressure upstream of the orifice plate is approximately twice that of the downstream side, and the upstream pressure is adjusted using a hand valve. 1. P1=2M, P2=1M Opening: 0.23mm 2. P1=4M, P2=2M Opening: 0.17mm 3. P1=6M, P2=3M. Opening size: 0.14mm. The flow rate is too low, resulting in a very small opening; it’s practically difficult to manufacture.
Our vaporizer pressure gauge – nitrogen has not been used·
Install a single stop valve and turn it down to a certain opening degree (there’s no need to specify the exact degree; adjust it slightly if necessary), then adjust the flow control valves at the front and back to get the desired flow rate… Can this subsequently installed stop valve be considered a flow-limiting orifice? -----------Isn’t the post by the master on the second floor, which addresses the original poster’s problem, based on exactly this principle? @HEJIYUER
This post was last edited by HEJIYUER on 2015-10-20 at 20:50. As a true \"flow control orifice plate,\" the flow rate remains constant; even if the pressure downstream changes, the flow rate does not change – and this is exactly the result you want. The condition is that the pressure upstream of the orifice plate is approximately twice that downstream (look at P1 and P2 that I used in my calculations). In this system of series-connected resistive elements, the orifice plate is responsible for flow restriction, while the manual valve handles pressure reduction; a smaller area leads to flow restriction. In a pipe, as long as one flow-restricting element brings it to the flow-limiting state, the entire flow rate is restricted. In practice, if you close the manual valve to a size smaller than that of the orifice (the opening), then the roles are reversed, and the manual valve becomes involved in \"flow restriction\". But generally, we prefer orifice plate flow restriction, because the orifice plate flow rate is “calculated”. From the perspective of throttling principles, globe valves and flow control orifices serve similar functions; a manual valve is essentially an \"orifice with an adjustable area.\" But the orifice size of the orifice plate is less than 0.2 mm; if a manual valve is used, the required size is also “0.2 mm”. A needle valve is a suitable choice, but even a slight movement causes a significant change in flow rate; therefore, in high-pressure applications some people use two valves for pressure reduction. However, if strict control over the flow rate is required, a flow-limiting orifice plate is used. The main issue for the poster: the flow rate is extremely low, even lower than that in conventional gauge backflow systems; it’s difficult to handle with dual valves, and it’s also hard to select an appropriate rotor flow meter. The brother who dealt with it earlier solved the problem, and I think there are two reasons: 1. The pressure upstream of N2 is low. Because he is a cold-box blower, his weight is around 6 KG (while the poster weighs 100 KG). The lower the upstream pressure, the larger the opening (a larger hole means it is easier to control with a hand valve). 2. Closing the manual valve behind the pressure gauge creates an artificial flow-limiting orifice; moreover, the flow rate he requires is not low (after all, there is a flow meter), and the degree of opening of the manual valve is not small, meaning it can be controlled. For this genuine flow-limiting orifice plate, the pressure behind the plate is the \"backpressure system\", which is maintained by that rear system, and it certainly meets the requirements.
The analysis upstairs is quite thorough; in actual practice, many things are not carried out in a proper manner, but no one really pays that much attention to it.